WO2004080425A2

WO2004080425A2 - Polypeptide compounds for inhibiting angiogenesis and tumor growth

Info

Publication number: WO2004080425A2
Application number: PCT/US2004/007755
Authority: WO
Inventors: Valery Krasnoperov; Sergey Zozulya; Nathalie Keretesz; Ramachandra Reddy; Parkash Gill
Original assignee: Vasgene Therapeutics, Inc.
Priority date: 2003-03-12
Filing date: 2004-03-12
Publication date: 2004-09-23
Also published as: WO2004080418A3; JP4762889B2; AU2004220525A1; EP1606305A2; US7585967B2; JP2011256179A; EP1605961A2; WO2004080425A3; US7862816B2; US20050164965A1; US20100093831A1; AU2010238577B2; AU2004220525B2; US20070031435A1; US8063183B2; CA2518912A1; AU2004220459B2; WO2004080418A2; AU2010238577A1; CA2518898A1

Abstract

In certain embodiments, this present invention provides polypeptide compositions, and methods for inhibiting Ephrin B2 or EphB4 activity. In other embodiments, the present invention provides methods and compositions for treating cancer or for treating angiogenesis-associated diseases.

Description

POLYPEPTIDE COMPOUNDS FOR INHIBITING ANGIOGENESIS AND TUMOR GROWTH

RELATED APPLICATIONS

This application claims the benefit of priority of U.S. Provisional Application number 60/454,300 filed March 12, 2003 and U.S. Provisional Application number 60/454,432 filed March 12, 2003. The entire teachings ofthe referenced Provisional Applications are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

Angiogenesis, the development of new blood vessels from the endothelium of a preexisting vasculature, is a critical process in the growth, progression, and metastasis of solid tumors within the host. During physiologically normal angiogenesis, the autocrine, paracrine, and amphicrine interactions ofthe vascular endothelium with its surrounding stromal components are tightly regulated both spatially and temporally. Additionally, the levels and activities of proangiogenic and angiostatic cytokines and growth factors are maintained in balance. In contrast, the pathological angiogenesis necessary for active tumor growth is sustained and persistent, representing a dysregulation ofthe normal angiogenic system. Solid and hematopoietic tumor types are particularly associated with a high level of abnormal angiogenesis.

It is generally thought that the development of tumor consists of sequential, and interrelated steps that lead to the generation of an autonomous clone with aggressive growth potential. These steps include sustained growth and unlimited self-renewal. Cell populations in a tumor are generally characterized by growth signal self-sufficiency, decreased sensitivity to growth suppressive signals, and resistance to apoptosis. Genetic or cytogenetic events that initiate aberrant growth sustain cells in a prolonged "ready" state by preventing apoptosis.

It is a goal ofthe present disclosure to provide agents and therapeutic treatments for inhibiting angiogenesis and tumor growth.

SUMMARY OF THE INVENTION hi certain aspects, the disclosure provides polypeptide agents that inhibit EphB4 or EphrinB2 mediated functions, including monomeric ligand binding portions ofthe EphB4 and EphrinB2 proteins and antibodies that bind to and affect EphB4 or EphrinB2 in particular ways. As demonstrated herein, EphB4 and EphrinB2 participate in various disease states, including cancers and diseases related to unwanted or excessive angiogenesis. Accordingly, certain polypeptide agents disclosed herein may be used to treat such diseases. In further aspects, the disclosure relates to the discovery that EphB4 and/or EphrinB2 are expressed, often at high levels, in a variety of tumors. Therefore, polypeptide agents that downregulate EphB4 or EphrinB2 function may affect tumors by a direct effect on the tumor cells as well as an indirect effect on the angiogenic processes recruited by the tumor, h certain embodiments, the disclosure provides the identity of tumor types particularly suited to treatment with an agent that downregulates EphB4 or EphrinB2 function.

In certain aspects, the disclosure provides soluble EphB4 polypeptides comprising an amino acid sequence of an extracellular domain of an EphB4 protein. The soluble EphB4 polypeptides bind specifically to an EphrinB2 polypeptide. The term "soluble" is used merely to indicate that these polypeptides do not contain a transmembrane domain or a portion of a transmembrane domain sufficient to compromise the solubility ofthe polypeptide in a physiological salt solution. Soluble polypeptides are preferably prepared as monomers that compete with EphB4 for binding to ligand such as EphrinB2 and inhibit the signaling that results from EphB4 activation. Optionally, a soluble polypeptide may be prepared in a multimeric form, by, for example, expressing as an Fc fusion protein or fusion with another multimerization domain. Such multimeric forms may have complex activities, having agonistic or antagonistic effects depending on the context. In certain embodiments the soluble EphB4 polypeptide comprises a globular domain of an EphB4 protein. A soluble EphB4 polypeptide may comprise a sequence at least 90% identical to residues 1-522 ofthe amino acid sequence defined by Figure 65. A soluble EphB4 polypeptide may comprise a sequence at least 90% identical to residues 1-412 ofthe amino acid sequence defined by Figure 65. A soluble EphB4 polypeptide may comprise a sequence at least 90% identical to residues 1-312 ofthe amino acid sequence defined by Figure 65. A soluble EphB4 polypeptide may comprise a sequence as set forth in Figure 1 or 2. In certain embodiments, the soluble EphB4 polypeptide may inhibit the interaction between Ephrin B2 and EphB4. The soluble EphB4 polypeptide may inhibit clustering of or phosphorylation of Ephrin B2 or EphB4. Phosphorylation of EphrinB2 or EphB4 is generally considered to be one ofthe initial events in triggering intracellular signaling pathways regulated by these proteins. As noted above, the soluble EphB4 polypeptide may be prepared as a monomeric or multimeric fusion protein. The soluble polypeptide may include one or more modified amino acids. Such amino acids may contribute to desirable properties, such as increased resistance to protease digestion.

In certain aspects, the disclosure provides soluble EphrinB2 polypeptides comprising an amino acid sequence of an extracellular domain of an EphrinB2 protein. The soluble EphrinB2 polypeptides bind specifically to an EphB4 polypeptide. The term "soluble" is used merely to indicate that these polypeptides do not contain a transmembrane domain or a portion of a transmembrane domain sufficient to compromise the solubility ofthe polypeptide in a physiological salt solution. Soluble polypeptides are preferably prepared as monomers that compete with EphrinB2 for binding to ligand such as EphB4 and inhibit the signaling that results from EphrinB2 activation. Optionally, a soluble polypeptide may be prepared in a multimeric form, by, for example, expressing as an Fc fusion protein or fusion with another multimerization domain. Such multimeric forms may have complex activities, having agonistic or antagonistic effects depending on the context. A soluble EphrinB2 polypeptide may comprise residues 1-225 ofthe amino acid sequence defined by Figure 66. A soluble EphrinB2 polypeptide may comprise a sequence defined by Figure 3. In certain embodiments, the soluble EphrinB2 polypeptide may inhibit the interaction between Ephrin B2 and EphB4. The soluble EphrinB2 polypeptide may inhibit clustering of or phosphorylation of EphrinB2 or EphB4. As noted above, the soluble EphrinB2 polypeptide may be prepared as a monomeric or multimeric fusion protein. The soluble polypeptide may include one or more modified amino acids. Such amino acids may contribute to desirable properties, such as increased resistance to protease digestion. In certain aspects, the disclosure provides antagonist antibodies for EphB4 and

EphrinB2. An antibody may be designed to bind to an extracellular domain of an EphB4 protein and inhibit an activity ofthe EphB4. An antibody may be designed to bind to an extracellular domain of an Ephrin B2 protein and inhibit an activity ofthe Ephrin B2. An antibody may be designed to inhibit the interaction between Ephrin B2 and EphB4. An antagonist antibody will generally affect Eph and/or Ephrin signaling. For example, an antibody may inhibit clustering or phosphorylation of Ephrin B2 or EphB4. An antagonist antibody may be essentially any polypeptide comprising a variable portion of an antibody, including, for example, monoclonal and polyclonal antibodies, single chain antibodies, diabodies, minibodies, etc.

In certain aspects, the disclosure provides pharmaceutical formulations comprising a polypeptide reagent and a pharmaceutically acceptable carrier. The polypeptide reagent may be any disclosed herein, including, for example, soluble EphB4 or EphrinB2 polypeptides and antagonist antibodies. Additional formulations include cosmetic compositions and diagnostic kits.

In certain aspects the disclosure provides methods of inhibiting signaling through Ephrin B2/EphB4 pathway in a cell. A method may comprise contacting the cell with an effective amount of a polypeptide agent, such as (a) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an EphB4 protein, wherein the EphB4 polypeptide is a monomer and binds specifically to an Ephrin B2 polypeptide; (b) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an Ephrin B2 protein, wherein the soluble Ephrin B2 polypeptide is a monomer and binds with high affinity to an EphB4 polypeptide; (c) an antibody which binds to an extracellular domain of an EphB4 protein and inhibits an activity ofthe EphB4; or (d) an antibody which binds to an extracellular domain of an Ephrin B2 protein and inhibits an activity ofthe Ephrin B2.

In certain aspects the disclosure provides methods for reducing the growth rate of a tumor, comprising administering an amount of a polypeptide agent sufficient to reduce the growth rate ofthe tumor, wherein the polypeptide agent is selected from the group consisting of: (a) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an EphB4 protein, wherein the EphB4 polypeptide is a monomer and binds specifically to an Ephrin B2 polypeptide; (b) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an Ephrin B2 protein, wherein the soluble Ephrin B2 polypeptide is a monomer and binds with high affinity to an EphB4 polypeptide; (c) an antibody which binds to an extracellular domain of an EphB4 protein and inhibits an activity ofthe EphB4; and (d) an antibody which binds to an extracellular domain of an Ephrin B2 protein and inhibits an activity ofthe Ephrin B2. Optionally, the tumor comprises cells expressing a higher level of EphB4 and/or EphrinB2 than noncancerous cells of a comparable tissue. In certain aspects, the disclosure provides methods for treating a patient suffering from a cancer. A method may comprise administering to the patient a polypeptide agent selected from the group consisting of: (a) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an EphB4 protein, wherein the EphB4 polypeptide is a monomer and binds specifically to an Ephrin B2 polypeptide; (b) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an Ephrin B2 protein, wherein the soluble Ephrin B2 polypeptide is a monomer and binds with high affinity to an EphB4 polypeptide; (c) an antibody which binds to an extracellular domain of an EphB4 protein and inhibits an activity ofthe EphB4; and (d) an antibody which binds to an extracellular domain of an Ephrin B2 protein and inhibits an activity ofthe Ephrin B2. Optionally, the cancer comprises cancer cells expressing EphrinB2 and/or EphB4 at a higher level than noncancerous cells of a comparable tissue. The cancer may be a metastatic cancer. The cancer may be selected from the group consisting of colon carcinoma, breast tumor, mesothelioma, prostate tumor, squamous cell carcinoma, Kaposi sarcoma, and leukemia. Optionally, the cancer is an angiogenesis-dependent cancer or an angiogenesis independent cancer. The polypeptide agent employed may inhibit clustering or phosphorylation of Ephrin B2 or EphB4. A polypeptide agent may be co-administered with one or more additional anti- cancer chemotherapeutic agents that inhibit cancer cells in an additive or synergistic manner with the polypeptide agent. hi certain aspects, the disclosure provides methods of inhibiting angiogenesis. A method may comprise contacting a cell with an amount of a polypeptide agent sufficient to inhibit angiogenesis, wherein the polypeptide agent is selected from the group consisting of: (a) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an EphB4 protein, wherein the EphB4 polypeptide is a monomer and binds specifically to an Ephrin B2 polypeptide; (b) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an Ephrin B2 protein, wherein the soluble Ephrin B2 polypeptide is a monomer and binds with high affinity to an EphB4 polypeptide; (c) an antibody which binds to an extracellular domain of an EphB4 protein and inhibits an activity ofthe EphB4; and (d) an antibody which binds to an extracellular domain of an Ephrin B2 protein and inhibits an activity ofthe Ephrin B2.

In certain aspects, the disclosure provides methods for treating a patient suffering from an angiogenesis-associated disease, comprising administering to the patient a polypeptide agent selected from the group consisting of: (a) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an EphB4 protein, wherein the EphB4 polypeptide is a monomer and binds specifically to an Ephrin B2 polypeptide; (b) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an Ephrin B2 protein, wherein the soluble Ephrin B2 polypeptide is a monomer and binds with high affinity to an EphB4 polypeptide; (c) an antibody which binds to an extracellular domain of an EphB4 protein and inhibits an activity ofthe EphB4; and (d) an antibody which binds to an extracellular domain of an Ephrin B2 protein and inhibits an activity ofthe Ephrin B2. The soluble polypeptide may be formulated with a pharmaceutically acceptable carrier. An angiogenesis related disease or unwanted angiogenesis related process may be selected from the group consisting of angiogenesis-dependent cancer, benign tumors, inflammatory disorders, chronic articular rheumatism and psoriasis, ocular angiogenic diseases, Osier- Webber Syndrome, myocardial angiogenesis, plaque neovascularization, telangiectasia, hemophiliac joints, angiofibroma, wound granulation, wound healing, telangiectasia psoriasis scleroderma, pyogenic granuloma, cororany collaterals, ischemic limb angiogenesis, rubeosis, arthritis, diabetic neovascularization, fractures, vasculogenesis, and hematopoiesis. An polypeptide agent may be co-administered with at least one additional anti-angiogenesis agent that inhibits angiogenesis in an additive or synergistic manner with the soluble polypeptide.

In certain aspects, the disclosure provides for the use of a polypeptide agent in the manufacture of medicament for the treatment of cancer or an angiogenesis related disorder, wherein the polypeptide agent is selected from the group consisting of: (a) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an EphB4 protein, wherein the EphB4 polypeptide is a monomer and binds specifically to an Ephrin B2 polypeptide; (b) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an Ephrin B2 protein, wherein the soluble Ephrin B2 polypeptide is a monomer and binds with high affinity to an EphB4 polypeptide; (c) an antibody which binds to an extracellular domain of an EphB4 protein and inhibits an activity ofthe EphB4; and (d) an antibody which binds to an extracellular domain of an Ephrin B2 protein and inhibits an activity ofthe Ephrin B2.

In certain aspects, the disclosure provides methods for for treating a patient suffering from a cancer, comprising: (a) identifying in the patient a tumor having a plurality of cancer cells that express EphB4 and/or EphrinB2; and (b) administering to the patient a polypeptide agent selected from the group consisting of: (i) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an EphB4 protein, wherein the EphB4 polypeptide is a monomer and binds specifically to an Ephrin B2 polypeptide; (ii) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an Ephrin B2 protein, wherein the soluble Ephrin B2 polypeptide is a monomer and binds with high affinity to an EphB4 polypeptide; (iii) an antibody which binds to an extracellular domain of an EphB4 protein and inhibits an activity ofthe EphB4; and (iv) an antibody which binds to an extracellular domain of an Ephrin B2 protein and inhibits an activity ofthe Ephrin B2. Optionally, a method may comprise identifying in the patient a tumor having a plurality of cancer cells having a gene amplification ofthe EphB4 and/or EphrinB2 gene.

In certain aspects, the disclosure provides methods for identifying a tumor that is suitable for treatment with an EphrinB2 or EphB4 antagonist. A method may comprise detecting in the tumor cell one or more ofthe following characteristics: (a) expression of EphB4 protein and/or mRNA; (b) expression of EphrinB2 protein and/or mRNA; (c) gene amplification ofthe EphB4 gene; or (d) gene amplification ofthe EphrihB2 gene. A tumor cell having one or more of characteristics (a)-(d) may be suitable for treatment with an EphrinB2 or EphB4 antagonist, such as a polypeptide agent described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows amino acid sequence ofthe B4ECv3 protein (predicted sequence of the precursor including uncleaved Eph B4 leader peptide is shown).

Figure 2 shows amino acid sequence ofthe B4ECv3NT protein (predicted sequence ofthe precursor including uncleaved Eph B4 leader peptide is shown). Figure 3 shows amino acid sequence ofthe B2EC protein (predicted sequence ofthe precursor including uncleaved Ephrin B2 leader peptide is shown).

Figure 4 shows amino acid sequence ofthe B4ECv3-FC protein (predicted sequence ofthe precursor including uncleaved Eph B4 leader peptide is shown).

Figure 5 shows amino acid sequence ofthe B2EC-FC protein (predicted sequence of the precursor including uncleaved Ephrin B2 leader peptide is shown).

Figure 6 shows B4EC-FC binding assay (Protein A-agarose based).

Figure 7 shows B4EC-FC inhibition assay (Inhibition in solution).

Figure 8 shows B2EC-FC binding assay (Protein- A- agarose based assay).

Figure 9 shows chemotaxis of HUAEC in response to B4Ecv3. Figure 10 shows chemotaxis of HHEC in response to B2EC-FC. Figure 11 shows chemotaxis of HHAEC in response to B2EC.

Figure 12 shows effect of B4Ecv3 on HUAEC tubule formation.

Figure 13 shows effect of B2EC-FC on HUAEC tubule formation.

Figure 14 is a schematic representation of human Ephrin B2 constructs. Figure 15 is a schematic representation of human EphB4 constructs.

Figure 16 shows the domain structure ofthe recombinant soluble EphB4EC proteins. Designation ofthe domains are as follows: L - leader peptide, G- globular (ligand-binding domain), C - Cys-rich domain, FI, F2 - fibronectin type III repeats, H - 6 x His-tag.

Figure 17 shows purification and ligand binding properties ofthe EphB4EC proteins. A. SDS-PAAG gel electrophoresis of purified EphB4-derived recombinant soluble proteins (Coomassie-stained). B. Binding of Ephrin B2-AP fusion to EphB4-derived recombinant proteins immobilized on Ni-NTA-agarose beads. Results of tliree independent experiments are shown for each protein. Vertical axis - optical density at 420 nm.

Figure 18 shows that EphB4v3 inhibits chemotaxis. Figure 19 shows that EphB4v3 inhibits tubule formation on Matrigel. A displays the strong inhibition of tubule formation by B4v3 in a representative experiment. B shows a quantitation ofthe reduction of tube-length obtained with B4v3 at increasing concentrations as well as a reduction in the number of junctions, in comparison to cells with no protein. Results are displayed as mean values _ S.D. obtained from three independent experiments performed with duplicate wells.

Figure 20 shows that soluble EphB4 has no detectable cytotoxic effect as assessed by MTS assay.

Figure 21 shows that B4v3 inhibits invasion and tubule formation by endothelial cells in the Matrigel assay. (A) to detect total invading cells, photographed at 20X magnification or with Masson's Trichrome Top left of A B displays section of a Matrigel plug with no GF , top right of A displays section with B4IgG containing GF and lower left section contains GF, and lower right shows GF in the presence of B4v3. Significant invasion of endothelial cells is only seenin GF containing Matrigel. Top right displays an area with a high number of invaded cells induced by B4IgG, which signifies the dimeric form of B4v3. The left upper parts ofthe pictures correspond to the cell layers formed around the Matrigel plug from which cells invade toward the center ofthe plug located in the direction ofthe right lower corner. Total cells in sections ofthe Matrigel plugs were quantitated with Scion Image software. Results obtained from two experiments with duplicate plugs are displayed as mean values _ S.D.

Figure 22 shows tyrosine phosphorylation of EphB4 receptor in PC3 cells in response to stimulation with EphrinB2-Fc fusion in presence or absence of EphB4-derived recombinant soluble proteins.

Figure 23 shows effects of soluble EphB4ECD on viability and cell cycle. A) 3-day cell viability assay of two HNSCC cell lines. B) FACS analysis of cell cycle in HNSCC-15 cells treated as in A. Treatment of these cells resulted in accumulation in subGO/Gl and S/G2 phases as indicated by the arrows.

Figure 24 shows that B4v3 inhibitis neovascular response in a murine corneal hydron micropocket assay.

Figure 25 shows that that SCC15, B16, and MCF-7 co-injected with sB4v3 in the presence of matrigel and growth factors, inhibits the in vivo tumor growth of these cells. Figure 26 shows that soluble EphB4 causes apoptosis, necrosis and decreased angiogenesis in threee tumor types, B16 melanoma, SCC15, head and neck carcinoma, and MCF-7 Breast carcinoma. Tumors were injected premixed with Matrigel plus growth factors and soluble EphB4 subcutaneously. After 10 to 14 days, the mice were injected intravenously with fitc-lectin (green) to assess blood vessel perfusion. Tumors treated with control PBS displayed abundant tumor density and a robust angiogenic response Tumors treated with sEphB4 displayed a decrease in tumor cell density and a marked inhibition of tumor angiogenesis in regions with viable tumor cells, as well as tumor necrosis and apoptosis.

Figure 27 shows expression of EphB4 in prostate cell lines. A) Western blot of total cell lysates of various prostate cancer cell lines, normal prostate gland derived cell line (MLC) and acute myeloblastic lymphoma cells (AML) probed with EphB4 monoclonal antibody. B) Phosphorylation of EphB4 in PC-3 cells determined by Western blot.

Figure 28 shows expression of EphB4 in prostate cancer tissue. Representative prostate cancer frozen section stained with EphB4 monoclonal antibody (top left) or isotype specific control (bottom left). Adjacent BPH tissue stained with EphB4 monoclonal antibody (top right). Positive signal is brown color in the tumor cells. Stroma and the normal epithelia are negative. Note membrane localization of stain in the tumor tissue, consistent with trans- membrane localization of EphB4. Representative QRT-PCR of RNA extracted from cancer specimens and adjacent BPH tissues (lower right).

Figure 29 shows downregulation of EphB4 in prostate cancer cells by tumor suppressors and RXR expression. A) PC3 cells were co-transfected with truncated CD4 and p53 or PTEN or vector only. 24 h later CD4-sorted cells were collected, lysed and analyzed sequentially by Western blot for the expression of EphB4 and β-actin, as a normalizer protein. B) Western blot as in (A) of various stable cell lines. LNCaP-FGF is a stable transfection clone of FGF-8, while CWR22R-RXR stably expresses the RXR receptor. BPH- 1 was established from benign hypertrophic prostatic epithelium. Figure 30 shows downregulation of EphB4 in prostate cancer cells by EGFR and

IGFR-1. A) Western blot of PC3 cells treated with or without EGFR specific inhibitor AG1478 (1 M) for 36 hours. Decreased EphB4 signal is observed after AG 1478 treatment. The membrane was stripped and reprobed with β-actin, which was unaffected. B) Western Blot of triplicate samples of PC3 cells freated with or without IGFR-1 specific neutralizing antibody MAB391 (2 μg/ml; overnight). The membrane was sequentially probed with EphB4, IGFR-1 and β-actin antibodies. IGFR-1 signal shows the expected repression of signal with MAB391 treatment.

Figure 31 shows effect of specific EphB4 AS-ODNs and siRNA on expression and prostate cell functions. A) 293 cells stably expressing full-length construct of EphB4 was used to evaluate the ability of siRNA 472 to inhibit EphB4 expression. Cells were transfected with 50 nM RNAi using Lipofectamine 2000. Western blot of cell lysates 40 h post transfection with control siRNA (green fluorescence protein; GFP siRNA) or EphB4 siRNA 472, probed with EphB4 monoclonal antibody, stripped and reprobed with β-actin monoclonal antibody. B) Effect of EphB4 AS-10 on expression in 293 transiently expressing full-length EphB4. Cells were exposed to AS-10 or sense ODN for 6 hours and analyzed by Western blot as in (A). C) 48 h viability assay of PC3 cells treated with siRNA as described in the Methods section. Shown is mean + s.e.m. of triplicate samples. D) 5-day viability assay of PC3 cells treated with ODNs as described in the Methods. Shown is mean + s.e.m. of triplicate samples. E) Scrape assay of migration of PC3 cells in the presence of 50 nM siRNAs transfected as in (A). Shown are photomicrographs of representative 20x fields taken immediately after the scrape was made in the monolayer (0 h) and after 20h continued culture. A large number of cells have filled in the scrape after 20 h with control siRNA, but not with EphB4 siRNA 472. F) Shown is a similar assay for cells treated with AS-10 or sense ODN (both 10 μM). G) Matrigel invasion assay of PC3 cells transfected with siRNA or control siRNA as described in the methods. Cells migrating to the underside ofthe Matrigel coated insert in response to 5 mg/ml fibronectin in the lower chamber were fixed and stained with Giemsa. Shown are representative photomicrographs of control siRNA and siRNA 472 treated cells. Cell numbers were counted in 5 individual high-powered fields and the average + s.e.m. is shown in the graph (bottom right).

Figure 32 shows effect of EphB4 siRNA 472 on cell cycle and apoptosis. A) PC3 cells transfected with siRNAs as indicated were analyzed 24 h post transfection for cell cycle status by flow cytometry as described in the Methods. Shown are the plots of cell number vs. propidium iodide fluorescence intensity. 7.9% ofthe cell population is apoptotic (in the Sub GO peak) when treated with siRNA 472 compared to 1% with control siRNA. B) Apoptosis of PC3 cells detected by Cell Death Detection ELISA^plus kit as described in the Methods. Absorbance at 405 nm increases in proportion to the amount of histone and DNA-POD in the nuclei-free cell fraction. Shown is the mean + s.e.m. of triplicate samples at the indicated concentrations of siRNA 472 and GFP siRNA (control).

Figure 33 shows that EphB4 and EphrinB2 are expressed in mesothelioma cell lines as shown by RT-PCR (A) and Western Blot (B).

Figure 34 shows expression of ephrin B2 and EphB4 by in situ hybridization in mesothelioma cells. NCI H28 mesothelioma cell lines cultured in chamber slides hybridized with antisense probe to eplirin B2 or EphB4 (top row). Control for each hybridization was sense (bottom row). Positive reaction is dark blue cytoplasmic stain.

Figure 35 shows cellular expression of EphB4 and ephrin B2 in mesothelioma cultures. Immunofluorescence staining of primary cell isolate derived from pleural effusion of a patient with malignant mesothelioma and cell lines NCI H28, NCI H2373, and NCI H2052 for eplirin B2 and EphB4. Green color is positive signal for FITC labeled secondary antibody. Specificity of immunofluorescence staining was demonstrated by lack of signal with no primary antibody (first row). Cell nuclei were counterstained with DAPI (blue color) to reveal location of all cells. Shown are merged images of DAPI and FITC fluorescence. Original magnification 200X. Figure 36 shows expression of ephrin B2 and EphB4 in mesothelioma tumor.

Immunohistochemistry of malignant mesothelioma biopsy. H&E stained section to reveals tumor architecture; bottom left panel is background control with no primary antibody. EphB4 and ephrin B2 specific staining is brown color. Original magnification 200X.

Figure 37 shows effects of EPHB4 antisense probes (A) and EPHB4 siRNAs (B) on the growth of H28 cells. Figure 38 shows effects of EPHB4 antisense probes (A) and EPHB4 siRNAs (B) on cell migration.

Figure 39 shows that EphB4 is expressed in HNSCC primary tissues and metastases. A) Top: Immunohistochemistry of a representative archival section stained with EphB4 monoclonal antibody as described in the methods and visualized with DAB (brown color) localized to tumor cells. Bottom: Hematoxylin and Eosin (H&E) stain of an adjacent section. Dense purple staining indicates the presence of tumor cells. The right hand column are frozen sections of lymph node metastasis stained with EphB4 polyclonal antibody (top right) and visualized with DAB. Control (middle) was incubation with goat serum and H&E (bottom) reveals the location ofthe metastatic foci surrounded by sfroma which does not stain. B) In situ hybridization of serial frozen sections of a HNSCC case probed with EρhB4 (left column) and ephrin B2 (right column) DIG labeled antisense or sense probes generated by run-off transcription. Hybridization signal (dark blue) was detected using alkaline- phosphatase-conjugated anti-DIG antibodies and sections were counterstained with Nuclear Fast Red. A serial section stained with H&E is shown (bottom left) to illustrate tumor architecture. C) Western blot of protein extract of patient samples consisting of tumor (T), uninvolved normal tissue (N) and lymph node biopsies (LN). Samples were fractionated by polyacrylamide gel electrophoresis in 4-20% Tris-glycine gels and subsequently electroblotted onto nylon membranes. Membranes were sequentially probed with EphB4 monoclonal antibody and β-actin MoAb. Chemiluminescent signal was detected on autoradiography film. Shown is the EphB4 specific band which migrated at 120 kD and β- actin which migrated at 40 kD. The β-actin signal was used to control for loading and transfer of each sample.

Figure 40 shows that EphB4 is expressed in HNSCC cell lines and is regulated by EGF: A) Survey of EphB4 expression in SCC cell lines. Western blot of total cell lysates sequentially probed with EphB4 monoclonal antibody, stripped and reprobed with β-actin monoclonal antibody as described for Fig. 39C. B) Effect ofthe specific EGFR inhibitor AG1478 on EphB4 expression: Western blot of crude cell lysates of SCC 15 treated with 0- 1000 nM AG 1478 for 24 h in media supplemented with 10% FCS (left) or with 1 mM AG 1478 for 4, 8, 12 or 24 h (right). Shown are membranes sequentially probed for EphB4 and β- actin. C) Effect of inhibition of EGFR signaling on EphB4 expression in SCC cell lines: Cells maintained in growth media containing 10%> FCS were treated for 24 hr with 1 μM AG 1478, after which crude cell lysates were analyzed by Western blots of cell lysates sequentially probed with for EGFR, EphB4, ephrin B2 and β-actin antibodies. Specific signal for EGFR was detected at 170 kD and ephrin B2 at 37 kD in addition to EphB4 and β-actin as described in Fig. IC. β-actin serves as loading and transfer confrol.

Figure 41 shows mechanism of regulation of EphB4 by EGF: A) Schematic ofthe EGFR signaling pathways, showing in red the sites of action and names of specific kinase inhibitors used. B) SCC 15 cells were serum-starved for 24 h prior to an additional 24 incubation as indicated with or without EGF (10 ng/ml), 3 μM U73122, or 5 μM SH-5, 5 μM SP600125, 25 nM LY294002, - μM PD098095 or 5 μM SB203580. N/A indicates cultures that received equal volume of diluent (DMSO) only. Cell lysates were subjected to Western Blot with EphB4 monoclonal antibody, β-actin signal serves as control of protein loading and transfer.

Figure 42 shows that specific EphB4 siRNAs inhibit EphB4 expression, cell viability and cause cell cycle arrest. A) 293 cells stably expressing full length EphB4 were transfected with 50 nM RNAi using LipofectamineTM2000. 40 h post-transfection cells were harvested, lysed and processed for Western blot. Membranes were probed with EphB4 monoclonal antibody, stripped and reprobed with β-actin monoclonal antibody as control for protein loading and transfer. Negative reagent control was RNAi to scrambled green fluorescence protein (GFP) sequence and confrol is transfection with LipofectamineTM2000 alone. B) MTT cell viability assays of SCC cell lines treated with siRNAs for 48 h as described in the Methods section. Shown is mean + s.e.m. of triplicate samples. C) SCC 15 cells transfected with siRNAs as indicated were analyzed 24 h post transfection for cell cycle status by flow cytometry as described in the Methods. Shown are the plots of cell number vs. propidium iodide fluorescence intensity. Top and middle row show plots for cells 16 h after siRNA transfection, bottom row shows plots for cells 36 h post transfection. Specific siRNA and concentration are indicated for each plot. Lipo = LipofectamineTM200 mock transfection.

Figure 43 shows in vitro effects of specific EphB4 AS-ODNs on SCC cells. A) 293 cells transiently transfected with EphB4 full-length expression plasmid were treated 6 h post transfection with antisense ODNs as indicated. Cell lysates were collected 24 h after AS- ODN treatment and subjected to Western Blot. B) SCC25 cells were seeded on 48 well plates at equal densities and treated with EphB4 AS-ODNs at 1, 5, and 10 μM on days 2 and 4. Cell viability was measured by MTT assay on day 5. Shown is the mean + s.e.m. of triplicate samples. Note that AS-ODNs that were active in inhibiting EphB4 protein levels were also effective inhibitors of SCC 15 cell viability. C) Cell cycle analysis of SCC 15 cells treated for 36 h with AS-10 (bottom) compared to cells that were not treated (top). D) Confluent cultures of SCC 15 cells scraped with a plastic Pasteur pipette to produce 3 mm wide breaks in the monolayer. The ability ofthe cells to migrate and close the wound in the presence of inhibiting EphB4 AS-ODN (AS-10) and non-inhibiting AS-ODN (AS-1) was assessed after 48 h. Scrambled ODN is included as a negative control ODN. Culture labeled no treatment was not exposed to ODN. At initiation ofthe experiment, all cultures showed scrapes of equal width and similar to that seen in 1 μM EphB4 AS-10 after 48 h. The red brackets indicate the width ofthe original scrape. E) Migration of SCC 15 cells in response to 20 mg/ml EGF in two-chamber assay as described in the Methods. Shown are representative photomicrographs of non-treated (NT), AS-6 and AS-10 treated cells and 10 ng/ml Taxol as positive control of migration inhibition. F) Cell numbers were counted in 5 individual high- powered fields and the average + s.e.m. is shown in the graph.

Figure 44 shows that EphB4 AS-ODN inhibits tumor growth in vivo. Growth curves for SCC15 subcutaneous tumor xenografts in Balb/C nude mice freated with EphB4 AS-10 or scrambled ODN at 20 mg/kg/day starting the day following implantation of 5 x 106 cells. Control mice received and equal volume of diluent (PBS). Shown are the mean + s.e.m. of 6 mice/group. * P = 0.0001 by Student's t-test compared to scrambled ODN treated group.

Figure 45 shows that Ephrin B2, but not EphB4 is expressed in KS biopsy tissue. (A) In situ hybridization with antisense probes for ephrin B2 and EphB4 with corresponding H&E stained section to show tumor architecture. Dark blue color in the ISH indicates positive reaction for ephrin B2. No signal for EphB4 was detected in the Kaposi's sarcoma biopsy. For contrast, ISH signal for EphB4 is strong in squamous cell carcinoma tumor cells. Ephrin B2 was also detected in KS using EphB4-AP fusion protein (bottom left). (B) Detection of ephrin B2 with EphB4/Fc fusion protein. Adjacent sections were stained with H&E (left) to show tumor architecture, black rectangle indicates the area shown in the

EphB4/Fc treated section (middle) detected with FITC-labeled anti-human Fc antibody as described in the methods section. As a control an adjacent section was treated with human Fc fragment (right). Specific signal arising from EphB4/Fc binding to the section is seen only in areas of tumor cells. (C) Co-expression of ephrin B2 and the HHV8 latency protein LANA1. Double-label confocal immunofluorescence microscopy with antibodies to ephrin B2 (red) LANA1 (green), or EphB4 (red) of frozen KS biopsy material directly demonstrates co- expression of LANAl and ephrin B2 in KS biopsy. Coexpression is seen as yellow color. Double label confocal image of biopsy with antibodies to PEC AM- 1 (green) in cells with nuclear propidium iodide stain (red), demonstrating the vascular nature ofthe tumor.

Figure 46 shows that HHV-8 induces arterial marker expression in venous endothelial cells. (A) Immunofluorescence of cultures of HUVEC and HUVEC/BC-1 for artery/vein markers and viral proteins. Cultures were grown on chamber slides and processed for immunofluorescence detection of ephrin B2 (a, e, i), EphB4 (m, q, u), CD 148 (j, v), and the HHV-8 proteins LANAl (b, f, m) or ORF59 (r) as described in the Materials and Methods. Yellow color in the merged images ofthe same field demonstrate co-expression of eplirin B2 and LANA or ephrin B2 and CD 148. The positions of viable cells were revealed by nuclear staining with DAPI (blue) in the third column (c, g, k, o, s, w). Photomicrographs are of representative fields. (B) RT-PCR of HUVEC and two HHV-8 infected cultures

(HUVEC/BC-1 and HUVEC BC-3) for ephrin B2 and EphB4. Ephrin B2 product (200 bp) is seen in HUVEC/BC-1, HUVEC/BC-3 and EphB4 product (400 bp) is seen in HUVEC. Shown also is β-actin RT-PCR as a control for amount and integrity of input RNA.

Figure 47 shows that HHV-8 induces arterial marker expression in Kaposi's sarcoma cells. (A) Western blot for ephrin B2 on various cell lysates. SLK-vGPCR is a stable clone of SLK expressing the HHV-8 vGPCR, and SLK-pCEFL is control stable clone transfected with empty expression vector. SLK cells transfected with LANA or LANAΔ440 are SLK-LANA and SLK-Δ440 respectively. Quantity of protein loading and transfer was determined by reprobing the membranes with β-actin monoclonal antibody. (B) Transient transfection of KS-SLK cells with expression vector pvGPCR-CEFL resulted in the expression of ephrin B2 as shown by immunofluorescence staining with FITC (green), whereas the control vector pCEFL had no effect. KS-SLK cells (0.8 x 105/ ell) were transfected with 0.8 μg DNA using Lipofectamine 2000. 24 hr later cells were fixed and stained with ephrin B2 polyclonal antibody and FITC conjugated secondary antibody as described in the methods. (C) Transient transfection of HUVEC with vGPCR induces transcription from ephrin B2 luciferase constructs. 8 x 103 HUVEC in 24 well plates were transfected using Superfect with 0.8 μg/well ephrin B2 promoter constructs containing sequences from -2941 to -11 with respect to the translation start site, or two 5 '-deletions as indicated, together with 80 ng/well pCEFL or pvGPCR-CEFL. Luciferase was deteπnined 48 h post transfection and induction ratios are shown to the right ofthe graph. pGL3Basic is promoterless luciferase control vector. Luciferase was normalized to protein since GPCR induced expression ofthe cotransfected β- galactosidase. Graphed is mean + SEM of 6 replicates. Shown is one of three similar experiments.

Figure 48 shows that VEGF and VEGF-C regulate ephrin B2 expression. A) Inhibition of ephrin B2 by neutralizing antibodies. Cells were cultured in full growth medium and exposed to antibody (100 ng/ml) for 36 hr before collection and lysis for Western blot. B) For induction of ephrin B2 expression cells were cultured in EBM growth medium containing 5% serum lacking growth factors. Individual growth factors were added as indicated and the cells harvested after 36 h. Quantity of protein loading and transfer was determined by reprobing the membranes β-actin monoclonal antibody.

Figure 49 shows that Eplirin B2 knock-down with specific siRNA inhibits viability in KS cells and HUVEC grown in the presence of VEGF but not IGF, EGF or bFGF. A) KS- SLK cells were transfected with various siRNA to ephrin B2 and controls. After 48 hr the cells were harvested and crude cell lysates fractionated on 4-20% SDS-PAGE. Western blot was performed with monoclonal antibody to ephrin B2 generated in-house. The membrane was stripped and reprobed with β-actin monoclonal antibody (Sigma) to illustrate equivalent loading and transfer. B) 3 day cell viability assay of KS-SLK cultures in the presence of eplirin B2 and EphB4 siRNAs. 1 x 10⁵ cells/well in 24-well plates were treated with 0, 10 and 100 ng/ml siRNAs as indicated on the graph. Viability of cultures was determined by MTT assay as described in the methods section. Shown are the mean + standard deviation of duplicate samples. C) HUVE cells were seeded on eight wells chamber slides coated with fibronectin. The HUVE cells were grown overnight in EGM-2 media, which contains all growth supplements. On the following day, the media was replaced with media containing VEGF (lOng/ml) or EGF, FGF and IGF as indicated. After 2 hrs of incubation at 37 °C, the cells were transfected using Lipofectamine 2000 (Invitrogen) in Opti-MEM medium containing 10 nM of siRNA to ephrin B2, Eph B4 or green fluorescence protein (GFP) as control. The cells were incubated for 2 hr and then the fresh media containing growth factors or VEGF alone was added to their respective wells. After 48 hrs, the cells were stained with crystal violet and the pictures were taken immediately by digital camera at 10X magnification. Figure 50 shows that soluble EphB4 inhibits KS and EC cord formation and in vivo angiogenesis. Cord formation assay of HUVEC in MatrigelTM (upper row). Cells in exponential growth phase were freated overnight with the indicated concentrations of EphB4 extracellular domain (ECD) prior to plating on MatrigelTM. Cells were trypsinized and plated (1 x 10⁵ cells/well) in a 24-well plate containing 0.5 ml MatrigelTM. Shown are representative 20X phase contrast fields of cord formation after 8 hr plating on MatrigelTM in the continued presence ofthe test compounds as shown. Original magnification 200 X. KS-SLK cells treated in a similar manner (middle row) in a cord formation assay on MatrigelTM. Bottom row shows in vivo MatrigelTM assay: MatrigelTM plugs containing growth factors and EphB4 ECD or PBS were implanted subcutaneously in the mid- ventral region of mice. After 7 days the plugs were removed, sectioned and stained with H&E to visualize cells migrating into the matrix. Intact vessels with large lumens are observed in the control, whereas EphB4 ECD almost completely inhibited migration of cells into the Matrigel. Figure 51 shows expression of EPHB4 in bladder cancer cell lines (A), and regulation of EPHB4 expression by EGFR signaling pathway (B).

Figure 52 shows that transfection of p53 inhibit the expression of EPHB4 in 5637 cell.

Figure 53 shows growth inhibition of bladder cancer cell line (5637) upon treatment with EPHB4 siRNA 472.

Figure 54 shows results on apoptosis study of 5637 cells transfected with EPHB4 siRNA 472.

Figure 55 shows effects of EPHB4 antisense probes on cell migration. 5637 cells were treated with EPHB4AS10 (10 μM). Figure 56 shows effects of EPHB4 siRNA on cell invasion. 5637 cells were transfected with siRNA 472 or control siRNA.

Figure 57 shows comparison of EphB4 monoclonal antibodies by G250 and in pulldown assay.

Figure 58 shows that EphB4 antibodies inhibit the growth of SCC15 xenograft tumors. Figure 59 shows that EplιB4 antibodies cause apoptosis, necrosis and decreased angiogenesis in SCC 15, head and neck carcinoma tumor type.

Figure 60 shows that systemic administration of EphB4 antibodies leads to tumor regression. Figure 61 shows a genomic nucleotide sequence of human EphB4.

Figure 62 shows a cDNA nucleotide sequence of human EphB4.

Figure 63 shows a genomic nucleotide sequence of human Ephrin B2.

Figure 64 shows a cDNA nucleotide sequence of human Ephrin B2.

Figure 65 shows an amino acid sequence of human EphB4. Figure 66 shows an amino acid sequence of human Ephrin B2.

DETAILED DESCRIPTION OF THE INVENTION

I. Overview

The current invention is based in part on the discovery that signaling through the ephrin/epl rin receptor pathway contributes to tumorigenesis. Applicants detected expression of ephrin B2 and EphB4 in tumor tissues and developed anti-tumor therapeutic agents for blocking signaling through the ephrin ephrin receptor. In addition, the disclosure provides polypeptide therapeutic agents and methods for polypep tide-based inhibition ofthe function of EphB4 and/or Ephrin B2. Accordingly, in certain aspects, the disclosure provides numerous polypeptide compounds (agents) that may be used to treat cancer as well as angiogenesis related disorders and unwanted angiogenesis related processes.

As used herein, the terms Ephrin and Eph are used to refer, respectively, to ligands and receptors. They can be from any of a variety of animals (e.g., mammals/non-mammals, vertebrates/non-vertebrates, including humans). The nomenclature in this area has changed rapidly and the terminology used herein is that proposed as a result of work by the Eph

Nomenclature Committee, which can be accessed, along with previously-used names at web site http://www.eph-nomenclature.com.

The work described herein, particularly in the examples, refers to Ephrin B2 and EphB4. However, the present invention contemplates any ephrin ligand and/or Eph receptor within their respective family, which is expressed in a tumor. The ephrins (ligands) are of two structural types, which can be further subdivided on the basis of sequence relationships and, functionally, on the basis ofthe preferential binding they exhibit for two corresponding receptor subgroups. Structurally, there are two types of ephrins: those which are membrane- anchored by a glycerophosphatidylinositol (GPI) linkage and those anchored through a transmembrane domain. Conventionally, the ligands are divided into the Ephrin-A subclass, which are GPI-linked proteins which bind preferentially to EphA receptors, and the Ephrin-B subclass, which are transmembrane proteins which generally bind preferentially to EphB receptors.

The Eph family receptors are a family of receptor protein-tyrosine kinases which are related to Eph, a receptor named for its expression in an erythropoietin-producing human hepatocellular carcinoma cell line. They are divided into two subgroups on the basis ofthe relatedness of their extracellular domain sequences and their ability to bind preferentially to Ephrin-A proteins or Ephrin-B proteins. Receptors which interact preferentially with Ephrin- A proteins are EphA receptors and those which interact preferentially with Ephrin-B proteins are EphB receptors.

Eph receptors have an extracellular domain composed ofthe ligand-binding globular domain, a cysteine rich region followed by a pair of fibronectin type III repeats (e.g., see Figure 16). The cytoplasmic domain consists of a juxtamembrane region containing two conserved tyrosine residues; a protein tyrosine kinase domain; a sterile α-motif (SAM) and a PDZ-domain binding motif. EphB4 is specific for the membrane-bound ligand Ephrin B2 (Sakano, S. et al 1996; Brambilla R. et al 1995). Ephrin B2 belongs to the class of Eph ligands that have a transmembrane domain and cytoplasmic region with five conserved tyrosine residues and PDZ domain. Eph receptors are activated by binding of clustered, membrane attached ephrins (Davis S et al, 1994), indicating that contact between cells expressing the receptors and cells expressing the ligands is required for Eph activation.

Upon ligand binding, an Eph receptor dimerizes and autophosphorylate the juxtamembrane tyrosine residues to acquire full activation (Kalo MS et al, 1999, Binns KS, 2000). In addition to forward signaling through the Eph receptor, reverse signaling can occur through the ephrin Bs. Eph engagement of ephrins results in rapid phosphorylation ofthe conserved intracellular tyrosines (Bruckner K, 1997) and somewhat slower recruitment of PDZ binding proteins (Palmer A 2002). Recently, several studies have shown that high expression of Eph/ephrins may be associated with increased potentials for tumor growth, tumorigenicity, and metastasis (Easty DJ, 1999; Kiyokawa E, 1994; Tang XX, 1999; Vogt T, 1998; Liu W, 2002; Stephenson SA, 2001; Steube KG 1999; Berclaz G, 1996).

In certain embodiments, the present invention provides polypeptide therapeutic agents that inhibit activity of Ephrin B2, EphB4, or both. As used herein, the term "polypeptide therapeutic agent" or "polypeptide agent" is a generic term which includes any polypeptide that blocks signaling through the Ephrin B2/EphB4 pathway. A preferred polypeptide therapeutic agent ofthe invention is a soluble polypeptide of Ephrin B2 or EphB4. Another preferred polypeptide therapeutic agent ofthe invention is an antagonist antibody that binds to Ephrin B2 or EphB4. For example, such polypeptide therapeutic agent can inhibit function of Ephrin B2 or EphB4, inhibit the interaction between Ephrin B2 and EphB4, inhibit the phosphorylation of Ephrin B2 or EphB4, or inhibit any ofthe downstream signaling events upon binding of Ephrin B2 to EphB4.

II. Soluble Polypeptides

In certain aspects, the invention relates to a soluble polypeptide comprising an extracellular domain of an Ephrin B2 protein (referred to herein as an Ephrin B2 soluble polypeptide) or comprising an extracellular domain of an EphB4 protein (referred to herein as an EphB4 soluble polypeptide). Preferably, the subject soluble polypeptide is a monomer and is capable of binding with high affinity to Ephrin B2 or EphB4. In a specific embodiment, the EphB4 soluble polypeptide ofthe invention comprises a globular domain of an EphB4 protein. Specific examples EphB4 soluble polypeptides are provided in Figures 1, 2, and 15. Specific examples of Ephrin B2 soluble polypeptides are provided in Figures 3 and 14.

As used herein, the subject soluble polypeptides include fragments, functional variants, and modified forms of EphB4 soluble polypeptide or an Ephrin B2 soluble polypeptide. These fragments, functional variants, and modified forms ofthe subject soluble polypeptides antagonize function of EphB4, Ephrin B2 or both. hi certain embodiments, isolated fragments ofthe subject soluble polypeptides can be obtained by screening polypeptides recombinantly produced from the corresponding fragment ofthe nucleic acid encoding an EphB4 or Ephrin B2 soluble polypeptides. In addition, fragments can be chemically synthesized using techniques known in the art such as conventional Merrifield solid phase f-Moc or t-Boc chemistry. The fragments can be produced (recombinantly or by chemical synthesis) and tested to identify those peptidyl fragments that can function to inhibit function of EphB4 or Ephrin B2, for example, by testing the ability ofthe fragments to inhibit angiogenesis or tumor growth.

In certain embodiments, a functional variant of an EphB4 soluble polypeptide has an amino acid sequence that is at least 90%, 95%, 97%>, 99% or 100% identical to residues 1- 522, residues 1-412, or residues 1-312 ofthe amino acid sequence defined by Figure 65. In other embodiments, a functional variant of an Ephrin B2 soluble polypeptide has a sequence at least 90%, 95%, 97%, 99% or 100% identical to residues 1-225 ofthe amino acid sequence defined by Figure 66.

In certain embodiments, the present invention contemplates making functional variants by modifying the structure ofthe subject soluble polypeptide for such purposes as enhancing therapeutic or prophylactic efficacy, or stability (e.g., ex vivo shelf life and resistance to proteolytic degradation in vivo). Such modified soluble polypeptide are considered functional equivalents ofthe naturally-occurring EphB4 or Ephrin B2 soluble polypeptide. Modified soluble polypeptides can be produced, for instance, by amino acid substitution, deletion, or addition. For instance, it is reasonable to expect, for example, that an isolated replacement of a leucine with an isoleucine or valine, an aspartate with a glutamate, a threonine with a serine, or a similar replacement of an amino acid with a structurally related amino acid (e.g., conservative mutations) will not have a major effect on the biological activity ofthe resulting molecule. Conservative replacements are those that take place within a family of amino acids that are related in their side chains.

This invention further contemplates a method of generating sets of combinatorial mutants ofthe EphB4 or Ephrin B2 soluble polypeptides, as well as truncation mutants, and is especially useful for identifying functional variant sequences. The purpose of screening such combinatorial libraries may be to generate, for example, soluble polypeptide variants which can act as antagonists of EphB4, EphB2, or both. Combinatorially-derived variants can be generated which have a selective potency relative to a naturally occurring soluble polypeptide. Such variant proteins, when expressed from recombinant DNA constructs, can be used in gene therapy protocols. Likewise, mutagenesis can give rise to variants which have intracellular half-lives dramatically different than the corresponding wild-type soluble polypeptide. For example, the altered protein can be rendered either more stable or less stable to proteolytic degradation or other cellular process which result in destruction of, or otherwise inactivation ofthe protein of interest (e.g., a soluble polypeptide). Such variants, and the genes which encode them, can be utilized to alter the subject soluble polypeptide levels by modulating their half-life. For instance, a short half-life can give rise to more transient biological effects and, when part of an inducible expression system, can allow tighter control of recombinant soluble polypeptide levels within the cell. As above, such proteins, and particularly their recombinant nucleic acid constructs, can be used in gene therapy protocols.

There are many ways by which the library of potential homologs can be generated from a degenerate oligonucleotide sequence. Chemical synthesis of a degenerate gene sequence can be carried out in an automatic DNA synthesizer, and the synthetic genes then be ligated into an appropriate gene for expression. The purpose of a degenerate set of genes is to provide, in one mixture, all ofthe sequences encoding the desired set of potential soluble polypeptide sequences. The synthesis of degenerate oligonucleotides is well known in the art (see for example, Narang, SA (1983) Tetrahedron 39:3; Itakura et al., (1981) Recombinant DNA, Proc. 3rd Cleveland Sympos. Macromolecules, ed. AG Walton, Amsterdam: Elsevier pp273-289; Itakura et al., (1984) Annu. Rev. Biochem. 53:323; Itakura et al., (1984) Science 198:1056; Hce et al., (1983) Nucleic Acid Res. 11:477). Such techniques have been employed in the directed evolution of other proteins (see, for example, Scott et al., (1990) Science 249:386-390; Roberts et al., (1992) PNAS USA 89:2429-2433; Devlin et al., (1990) Science 249: 404-406; Cwirla et al., (1990) PNAS USA 87: 6378-6382; as well as U.S. Patent Nos: 5,223,409, 5,198,346, and 5,096,815). Alternatively, other forms of mutagenesis can be utilized to generate a combinatorial library. For example, soluble polypeptide variants (e.g., the antagonist forms) can be generated and isolated from a library by screening using, for example, alanine scanning mutagenesis and the like (Ruf et al., (1994) Biochemistry 33:1565-1572; Wang et al., (1994) J. Biol. Chem. 269:3095-3099; Balint et al., (1993) Gene 137:109-118; Grodberg et al, (1993) Eur. J. Biochem. 218:597-601; Nagashima et al., (1993) J. Biol. Chem. 268:2888- 2892; Lowman et al., (1991) Biochemistry 30:10832-10838; and Cunningham et al., (1989) Science 244:1081-1085), by linker scanning mutagenesis (Gustin et al., (1993) Virology 193:653-660; Brown et al, (1992) Mol. Cell Biol. 12:2644-2652; McKnight et al., (1982) Science 232:316); by saturation mutagenesis (Meyers et al., (1986) Science 232:613); by PCR mutagenesis (Leung et al., (1989) Method Cell Mol Biol 1 : 11-19); or by random mutagenesis, including chemical mutagenesis, etc. (Miller et al., (1992) A Short Course in Bacterial Genetics, CSHL Press, Cold Spring Harbor, NY; and Greener et al., (1994) Strategies in Mol Biol 7:32-34). Linker scanning mutagenesis, particularly in a combinatorial setting, is an attractive method for identifying truncated (bioactive) forms ofthe subject soluble polypeptide.

A wide range of techniques are known in the art for screening gene products of combinatorial libraries made by point mutations and truncations, and, for that matter, for screening cDNA libraries for gene products having a certain property. Such teclmiques will be generally adaptable for rapid screening ofthe gene libraries generated by the combinatorial mutagenesis ofthe subject soluble polypeptides. The most widely used techniques for screening large gene libraries typically comprises cloning the gene library into replicable expression vectors, transforming appropriate cells with the resulting library of vectors, and expressing the combinatorial genes under conditions in which detection of a desired activity facilitates relatively easy isolation ofthe vector encoding the gene whose product was detected. Each ofthe illustrative assays described below are amenable to high through-put analysis as necessary to screen large numbers of degenerate sequences created by combinatorial mutagenesis techniques. In certain embodiments, the subject soluble polypeptides ofthe invention include a a small molecule such as a peptide and a peptidomimetic. As used herein, the term "peptidomimetic" includes chemically modified peptides and peptide-like molecules that contain non-naturally occurring amino acids, peptoids, and the like. Peptidomimetics provide various advantages over a peptide, including enhanced stability when administered to a subject. Methods for identifying a peptidomimetic are well known in the art and include the screening of databases that contain libraries of potential peptidomimetics. For example, the Cambridge Structural Database contains a collection of greater than 300,000 compounds that have known crystal structures (Allen et al., Acta Crystallogr. Section B, 35:2331 (1979)). Where no crystal structure of a target molecule is available, a structure can be generated using, for example, the program CONCORD (Rusinko et al., J. Chem. Inf. Comput. Sci. 29:251 (1989)). Another database, the Available Chemicals Directory (Molecular Design Limited, Informations Systems; San Leandro Calif.), contains about 100,000 compounds that are commercially available and also can be searched to identify potential peptidomimetics of the EphB4 or Ephrin B2 soluble polypeptides. To illustrate, by employing scanning mutagenesis to map the amino acid residues of a soluble polypeptidewhich are involved in binding to another protein, peptidomimetic compounds can be generated which mimic those residues involved in binding. For instance, non-hydrolyzable peptide analogs of such residues can be generated using benzodiazepine (e.g., see Freidinger et al., in Peptides: Chemistry and Biology, G.R. Marshall ed., ESCOM Publisher: Leiden, Netherlands, 1988), azepine (e.g., see Huffman et al., in Peptides: Chemistry and Biology, G.R. Marshall ed., ESCOM Publisher: Leiden, Netherlands, 1988), substituted gamma lactam rings (Garvey et al., in Peptides: Chemistry and Biology, G.R. Marshall ed., ESCOM Publisher: Leiden, Netherlands, 1988), keto-methylene pseudopeptides (Ewenson et al., (1986) J. Med. Chem. 29:295; and Ewenson et al., in Peptides: Structure and Function (Proceedings ofthe 9th American Peptide Symposium) Pierce Chemical Co. Rockland, IL, 1985), b-turn dipeptide cores (Nagai et al., (1985) Tetrahedron Lett 26:647; and Sato et al., (1986) J Chem Soc Perkin Trans 1:1231), and b-ammoalcohols (Gordon et al., (1985) Biochem Biophys Res Commun 126:419; and Dann et al., (1986) Biochem Biophys Res Commun 134:71). '

In certain embodiments, the soluble polypeptides ofthe invention may further comprise post-translational modifications. Such modifications include, but are not limited to, acetylation, carboxylation, glycosylation, phosphorylation, lipidation, and acylation. As a result, the modified soluble polypeptides may contain non-amino acid elements, such as polyethylene glycols, lipids, poly- or mono-saccharide, and phosphates. Effects of such non- amino acid elements on the functionality of a soluble polypeptide may be tested for its antagozing role in EplτB4 or Ephrin B2 function, e.g, it inhibitory effect on angiogenesis or on tumor growth. In certain aspects, functional variants or modified forms ofthe subject soluble polypeptides include fusion proteins having at least a portion ofthe soluble polypeptide and one or more fusion domains. Well known examples of such fusion domains include, but are not limited to, polyhistidine, Glu-Glu, glutathione S transferase (GST), thioredoxin, protein A, protein G, and an immunoglobulin heavy chain constant region (Fc), maltose binding protein (MBP), which are particularly useful for isolation ofthe fusion proteins by affinity chromatography. For the purpose of affinity purification, relevant matrices for affinity chromatography, such as glutathione-, amylase-, and nickel- or cobalt- conjugated resins are used. Another fusion domain well known in the art is green fluorescent protein (GFP). Fusion domains also include "epitope tags," which are usually short peptide sequences for which a specific antibody is available. Well known epitope tags for which specific monoclonal antibodies are readily available include FLAG, influenza virus haemagglutinin (HA), and c-myc tags. In some cases, the fusion domains have a protease cleavage site, such as for Factor Xa or Thrombin, which allows the relevant protease to partially digest the fusion proteins and thereby liberate the recombinant proteins therefrom. The liberated proteins can then be isolated from the fusion domain by subsequent chromatographic separation. In certain embodiments, the soluble polypeptides ofthe present invention contain one or more modifications that are capable of stabilizing the soluble polypeptides. For example, such modifications enhance the in vitro half life ofthe soluble polypeptides, enhance circulatory half life ofthe soluble polypeptides or reducing proteolytic degradation ofthe soluble polypeptides.

In certain embodiments, soluble polypeptides (unmodified or modified) ofthe invention can be produced by a variety of art-known techniques. For example, such soluble polypeptides can be synthesized using standard protein chemistry techniques such as those described in Bodansky, M. Principles of Peptide Synthesis, Springer Verlag, Berlin (1993) and Grant G. A. (ed.), Synthetic Peptides: A User's Guide, W. H. Freeman and Company, New York (1992). In addition, automated peptide synthesizers are commercially available (e.g., Advanced ChemTech Model 396; Milligen/Biosearch 9600). Alternatively, the soluble polypeptides, fragments or variants thereof may be recombinantly produced using various expression systems as is well known in the art (also see below).

III. Nucleic acids encoding soluble polypeptides

In certain aspects, the invention relates to isolated and/or recombinant nucleic acids encoding an EphB4 or Ephrin B2 soluble polypeptide. The subject nucleic acids may be single-stranded or double-stranded, DNA or RNA molecules. These nucleic acids are useful as therapeutic agents. For example, these nucleic acids are useful in making recombinant soluble polypeptides which are administered to a cell or an individual as therapeutics. Alternative, these nucleic acids can be directly administered to a cell or an individual as therapeutics such as in gene therapy. In certain embodiments, the invention provides isolated or recombinant nucleic acid sequences that are at least 80%, 85%, 90%, 95%, 97%, 98%, 99% or 100% identical to a region ofthe nucleotide sequence depicted in Figure 62 or 63. One of ordinary skill in the art will appreciate that nucleic acid sequences complementary to the subject nucleic acids, and variants ofthe subject nucleic acids are also within the scope of this invention. In further embodiments, the nucleic acid sequences ofthe invention can be isolated, recombinant, and/or fused with a heterologous nucleotide sequence, or in a DNA library. In other embodiments, nucleic acids ofthe invention also include nucleotide sequences that hybridize under highly stringent conditions to the nucleotide sequence depicted in Figure 62 or 63, or complement sequences thereof. As discussed above, one of ordinary skill in the art will understand readily that appropriate stringency conditions which promote DNA hybridization can be varied. One of ordinary skill in the art will understand readily that appropriate stringency conditions which promote DNA hybridization can be varied. For example, one could perform the hybridization at 6.0 x sodium chloride/sodium citrate (SSC) at about 45 °C, followed by a wash of 2.0 x SSC at 50 °C. For example, the salt concentration in the wash step can be selected from a low stringency of about 2.0 x SSC at 50 °C to a high stringency of about 0.2 x SSC at 50 °C. In addition, the temperature in the wash step can be increased from low stringency conditions at room temperature, about 22 °C, to high stringency conditions at about 65 °C. Both temperature and salt may be varied, or temperature or salt concentration may be held constant while the other variable is changed. In one embodiment, the invention provides nucleic acids which hybridize under low stringency conditions of 6 x SSC at room temperature followed by a wash at 2 x SSC at room temperature.

Isolated nucleic acids which differ from the subject nucleic acids due to degeneracy in the genetic code are also within the scope ofthe invention. For example, a number of amino acids are designated by more than one triplet. Codons that specify the same amino acid, or synonyms (for example, CAU and CAC are synonyms for histidine) may result in "silent" mutations which do not affect the amino acid sequence ofthe protein. However, it is expected that DNA sequence polymorphisms that do lead to changes in the amino acid sequences ofthe subject proteins will exist among mammalian cells. One skilled in the art will appreciate that these variations in one or more nucleotides (up to about 3-5% ofthe nucleotides) ofthe nucleic acids encoding a particulai- protein may exist among individuals of a given species due to natural allelic variation. Any and all such nucleotide variations and resulting amino acid polymorphisms are within the scope of this invention.

In certain embodiments, the recombinant nucleic acids ofthe invention may be operably linked to one or more regulatory nucleotide sequences in an expression construct. Regulatory nucleotide sequences will generally be appropriate for a host cell used for expression. Numerous types of appropriate expression vectors and suitable regulatory sequences are known in the art for a variety of host cells. Typically, said one or more regulatory nucleotide sequences may include, but are not limited to, promoter sequences, leader or signal sequences, ribosomal binding sites, transcriptional start and termination sequences, translational start and termination sequences, and enhancer or activator sequences. Constitutive or inducible promoters as known in the art are contemplated by the invention. The promoters may be either naturally occurring promoters, or hybrid promoters that combine elements of more than one promoter. An expression construct may be present in a cell on an episome, such as a plasmid, or the expression construct may be inserted in a chromosome. In a preferred embodiment, the expression vector contains a selectable marker gene to allow the selection of transformed host cells. Selectable marker genes are well known in the art and will vary with the host cell used. hi certain aspect ofthe invention, the subject nucleic acid is provided in an expression vector comprising a nucleotide sequence encoding an EplιB4 or Ephrin B2 soluble polypeptide and operably linked to at least one regulatory sequence. Regulatory sequences are art-recognized and are selected to direct expression ofthe soluble polypeptide. Accordingly, the term regulatory sequence includes promoters, enhancers, and other expression control elements. Exemplary regulatory sequences are described in Goeddel; Gene Expression Technology: Methods in Enzymology, Academic Press, San Diego, CA (1990). For instance, any of a wide variety of expression control sequences that confrol the expression of a DNA sequence when operatively linked to it may be used in these vectors to express DNA sequences encoding a soluble polypeptide. Such useful expression confrol sequences, include, for example, the early and late promoters of S V40, tet promoter, adenovirus or cytomegalovirus immediate early promoter, the lac system, the trp system, the TAC or TRC system, T7 promoter whose expression is directed by T7 RNA polymerase, the major operator and promoter regions of phage lambda , the control regions for fd coat protein, the promoter for 3 -phosphoglycerate kinase or other glycolytic enzymes, the promoters of acid phosphatase, e.g., Pho5, the promoters ofthe yeast α-mating factors, the polyhedron promoter ofthe baculovirus system and other sequences Icnown to control the expression of genes of prokaryotic or eukaryotic cells or their viruses, and various combinations thereof. It should be understood that the design ofthe expression vector may depend on such factors as the choice ofthe host cell to be transformed and/or the type of protein desired to be expressed. Moreover, the vector's copy number, the ability to control that copy number and the expression of any other protein encoded by the vector, such as antibiotic markers, should also be considered. This invention also pertains to a host cell transfected with a recombinant gene including a coding sequence for one or more ofthe subject soluble polypeptide. The host cell may be any prokaryotic or eukaryotic cell. For example, a soluble polypeptide ofthe invention may be expressed in bacterial cells such as E. coli, insect cells (e.g., using a baculovirus expression system), yeast, or mammalian cells. Other suitable host cells are known to those skilled in the art.

Accordingly, the present invention further pertains to methods of producing the subject soluble polypeptides. For example, a host cell transfected with an expression vector encoding an ΕphB4 soluble polypeptide can be cultured under appropriate conditions to allow expression ofthe EphB4 soluble polypeptide to occur. The EphB4 soluble polypeptide may be secreted and isolated from a mixture of cells and medium containing the soluble polypeptides. Alternatively, the soluble polypeptides may be retained cytoplasmically or in a membrane fraction and the cells harvested, lysed and the protein isolated. A cell culture includes host cells, media and other byproducts. Suitable media for cell culture are well lαiown in the art. The soluble polypeptides can be isolated from cell culture medium, host cells, or both using techniques known in the art for purifying proteins, including ion- exchange chromatography, gel filtration chromatography, ultrafiltration, electrophoresis, and immunoaffinity purification with antibodies specific for particular epitopes ofthe soluble polypeptides. hi a preferred embodiment, the soluble polypeptide is a fusion protein containing a domain wliich facilitates its purification.

A recombinant nucleic acid ofthe invention can be produced by li gating the cloned gene, or a portion thereof, into a vector suitable for expression in either prokaryotic cells, eukaryotic cells (yeast, avian, insect or mammalian), or both. Expression vehicles for production of a recombinant soluble polypeptide include plasmids and other vectors. For instance, suitable vectors include plasmids ofthe types: pBR322-derived plasmids, pEMBL- derived plasmids, pEX-derived plasmids, pBTac-derived plasmids and pUC-derived plasmids for expression in prokaryotic cells, such as E. coli.

The prefeπed mammalian expression vectors contain both prokaryotic sequences to facilitate the propagation ofthe vector in bacteria, and one or more eukaryotic transcription units that are expressed in eukaryotic cells. The pcDNAI/amp, pcDNAI/neo, pRc/CMV, pSV2gpt, pSV2neo, pSV2-dhfr, pTk2, pRSVneo, pMSG, ρSVT7, pko-neo and pHyg derived vectors are examples of mammalian expression vectors suitable for transfection of eukaryotic cells. Some of these vectors are modified with sequences from bacterial plasmids, such as pBR322, to facilitate replication and drug resistance selection in both prokaryotic and eukaryotic cells. Alternatively, derivatives of viruses such as the bovine papilloma virus (BPV-1), or Epstein-Ban- virus (pHEBo, pREP-derived and p205) can be used for transient expression of proteins in eukaryotic cells. Examples of other viral (including retroviral) expression systems can be found below in the description of gene therapy delivery systems. The various methods employed in the preparation ofthe plasmids and transformation of host organisms are well known in the art. For other suitable expression systems for both prokaryotic and eukaryotic cells, as well as general recombinant procedures, see Molecular Cloning A Laboratoiγ Manual, 2nd Ed., ed. by Sambrook, Fritscli and Maniatis (Cold Spring Harbor Laboratory Press, 1989) Chapters 16 and 17. In some instances, it may be desirable to express the recombinant SLC5 A8 polypeptide by the use of a baculovirus expression system. Examples of such baculovirus expression systems include pVL-derived vectors (such as pVL1392, pVL1393 and pVL941), pAcUW-derived vectors (such as pAcUWl), and pBlueBac-derived vectors (such as the β-gal containing pBlueBac III). Techniques for making fusion genes are well known. Essentially, the joining of various DNA fragments coding for different polypeptide sequences is performed in accordance with conventional techniques, employing blunt-ended or stagger-ended termini for ligation, restriction enzyme digestion to provide for appropriate termini, filling-in of cohesive ends as appropriate, alkaline phosphatase treatment to avoid undesirable joining, and enzymatic ligation. In another embodiment, the fusion gene can be synthesized by conventional techniques including automated DNA synthesizers. Alternatively, PCR amplification of gene fragments can be carried out using anchor primers which give rise to complementary overhangs between two consecutive gene fragments which can subsequently be annealed to generate a chimeric gene sequence (see, for example, Current Protocols in Molecular Biology, eds. Ausubel et al., John Wiley & Sons: 1992).

IV. Antibodies

In certain aspects, the the present invention provides antagonist antibodies against Ephrin B2 or EphB4. As described herein, the term "antagonist antibody" refers to an antibody that inliibits function of Eplirin B2 or EphB4. Preferably, the antagonist antibody binds to an extracellular domain of Ephrin B2 or EphB4. It is understood that antibodies of the invention may be polyclonal or monoclonal; intact or truncated, e.g., F(ab')2, Fab, Fv; xenogeneic, allogeneic, syngeneic, or modified forms thereof, e.g., humanized, chimeric, etc.

For example, by using immunogens derived from an Ephrin B2 or EphB4 polypeptide, anti-protein/anti-peptide antisera or monoclonal antibodies can be made by standard protocols (see, for example, Antibodies: A Laboratory Manual ed. by Harlow and Lane (Cold Spring Harbor Press: 1988)). A mammal, such as a mouse, a hamster or rabbit can be immunized with an immunogenic form ofthe peptide. (e.g., a polypeptide or an antigenic fragment which is capable of eliciting an antibody response, or a fusion protein). Techniques for conferring immunogenicity on a protein or peptide include conjugation to carriers or other techniques well known in the art. An immunogenic portion of an Ephrin B2 or EphB4 polypeptide can be administered in the presence of adjuvant. The progress of immunization can be monitored by detection of antibody titers in plasma or serum. Standard ELISA or other immunoassays can be used with the immunogen as antigen to assess the levels of antibodies, h one embodiment, antibodies ofthe invention are specific for the extracellular portion ofthe Ephrin B2 or EphB4 protein. In another embodiment, antibodies ofthe invention are specific for the intracellular portion or the transmembrane portion ofthe Ephrin B2 or EphB4 protein, hi a further embodiment, antibodies ofthe invention are specific for the extracellular portion ofthe Ephrin B2 or EphB4 protein.

Following immunization of an animal with an antigenic preparation of an Ephrin B2 or EphB4 polypeptide, antisera can be obtained and, if desired, polyclonal antibodies can be isolated from the serum. To produce monoclonal antibodies, antibody-producing cells (lymphocytes) can be harvested from an immunized animal and fused by standard somatic cell fusion procedures with immortalizing cells such as myeloma cells to yield hybridoma cells. Such techniques are well known in the art, and include, for example, the hybridoma technique (originally developed by Kohler and Milstein, (1975) Nature, 256: 495-497), the human B cell hybridoma technique (Kozbar et al., (1983) Immunology Today, 4: 72), and the EBV-hybridoma technique to produce human monoclonal antibodies (Cole et al., (1985) Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, Inc. pp. 77-96). Hybridoma cells can be screened immunochemically for production of antibodies specifically reactive with an Ephrin B2 or EphB4 polypeptide and monoclonal antibodies isolated from a culture comprising such hybridoma cells.

The term antibody as used herein is intended to include fragments thereof which are also specifically reactive with an Ephrin B2 or EphB4 polypeptides. Antibodies can be fragmented using conventional techniques and the fragments screened for utility in the same manner as described above for whole antibodies. For example, F(ab)2 fragments can be generated by treating antibody with pepsin. The resulting F(ab)2 fragment can be freated to reduce disulfide bridges to produce Fab fragments. The antibody ofthe present invention is further intended to include bispecific, single-chain, and chimeric and humanized molecules having affinity for an Ephrin B2 or EphB4 polypeptide confened by at least one CDR region ofthe antibody. Techniques for the production of single chain antibodies (US Patent No. 4,946,778) can also be adapted to produce single chain antibodies. Also, transgenic mice or other organisms including other mammals, may be used to express humanized antibodies. In prefeπed embodiments, the antibodies further comprise a label attached thereto and able to be detected (e.g., the label can be a radioisotope, fluorescent compound, enzyme or enzyme co- factor).

In certain prefeπed embodiments, an antibody ofthe invention is a monoclonal antibody, and in certain embodiments the invention makes available methods for generating novel antibodies. For example, a method for generating a monoclonal antibody that binds specifically to an Ephrin B2 or EphB4 polypeptide may comprise administering to a mouse an amount of an immunogenic composition comprising the Ephrin B2 or EphB4 polypeptide effective to stimulate a detectable immune response, obtaining antibody-producing cells (e.g., cells from the spleen) from the mouse and fusing the antibody-producing cells with myeloma cells to obtain antibody-producing hybridomas, and testing the antibody-producing hybridomas to identify a hybridoma that produces a monocolonal antibody that binds specifically to the Eplirin B2 or EphB4 polypeptide. Once obtained, a hybridoma can be propagated in a cell culture, optionally in culture conditions where the hybridoma-derived cells produce the monoclonal antibody that binds specifically to the Ephrin B2 or EphB4 polypeptide. The monoclonal antibody may be purified from the cell culture.

In addition, the techniques used to screen antibodies in order to identify a desirable antibody may influence the properties ofthe antibody obtained. For example, an antibody to be used for certain therapeutic purposes will preferably be able to target a particular cell type. Accordingly, to obtain antibodies of this type, it maybe desirable to screen for antibodies that bind to cells that express the antigen of interest (e.g., by fluorescence activated cell sorting). Likewise, if an antibody is to be used for binding an antigen in solution, it may be desirable to test solution binding. A variety of different techniques are available for testing antibody: antigen interactions to identify particularly desirable antibodies. Such techniques include ELISAs, surface plasmon resonance binding assays (e.g. the Biacore binding assay, Bia-core AB, Uppsala, Sweden), sandwich assays (e.g. the paramagnetic bead system of IGEN International, Inc., Gaithersburg, Maryland), western blots, immunoprecipitation assays and immunohistochemistry.

V. Drug Screening Assays

There are numerous approaches to screening for polypeptide therapeutic agents as antagonists of EphB4, Ephrin B2 or both. For example, high-throughput screening of compounds or molecules can be carried out to identify agents or drugs which inhibit angiogenesis or inhibit tumor growth. Test agents can be any chemical (element, molecule, compound, drug), made synthetically, made by recombinant techniques or isolated from a natural source. For example, test agents can be peptides, polypeptides, peptoids, sugars, hormones, or nucleic acid molecules. In addition, test agents can be small molecules or molecules of greater complexity made by combinatorial chemistry, for example, and compiled into libraries. These libraries can comprise, for example, alcohols, alkyl halides, amines, amides, esters, aldehydes, ethers and other classes of organic compounds. Test agents can also be natural or genetically engineered products isolated from lysates or growth media of cells ~ bacterial, animal or plant — or can be the cell lysates or growth media themselves. Presentation of test compounds to the test system can be in either an isolated form or as mixtures of compounds, especially in initial screening steps.

For example, an assay can be carried out to screen for compounds that specifically inhibit binding of Ephrin B2 (ligand) to EphB4 (receptor), or vice-versa, e.g., by inhibition of binding of labeled ligand- or receptor-Fc fusion proteins to immortalized cells. Compounds identified through this screening can then be tested in animals to assess their anti- angiogenesis or anti-tumor activity in vivo.

In one embodiment of an assay to identify a substance that interferes with interaction of two cell surface molecules (e.g., Ephrin B2 and EphB4), samples of cells expressing one type of cell surface molecule (e.g., EphB4) are contacted with either labeled ligand (e.g., Ephrin B2, or a soluble portion thereof, or a fusion protein such as a fusion ofthe extracellular domain and the Fc domain of IgG) or labeled ligand plus a test compound (or group of test compounds). The amount of labeled ligand which has bound to the cells is determined. A lesser amount of label (where the label can be, for example, a radioactive isotope, a fluorescent or colormetric label) in the sample contacted with the test compound(s) is an indication that the test compound(s) interferes with binding. The reciprocal assay using cells expressing a ligand (e.g., an Ephrin B2 ligand or a soluble form thereof) can be used to test for a substance that interferes with the binding of an Eph receptor or soluble portion thereof.

An assay to identify a substance which interferes with interaction between an Eph receptor and an ephrin can be performed with the component (e.g., cells, purified protein, including fusion proteins and portions having binding activity) which is not to be in competition with a test compound, linked to a solid support. The solid support can be any suitable solid phase or matrix, such as a bead, the wall of a plate or other suitable surface (e.g., a well of a microtiter plate), column pore glass (CPG) or a pin that can be submerged into a solution, such as in a well. Linkage of cells or purified protein to the solid support can be either direct or through one or more linker molecules.

In one embodiment, an isolated or purified protein (e.g., an Eph receptor or an ephrin) can be immobilized on a suitable affinity matrix by standard techniques, such as chemical cross-linking, or via an antibody raised against the isolated or purified protein, and bound to a solid support. The matrix can be packed in a column or other suitable container and is contacted with one or more compounds (e.g., a mixture) to be tested under conditions suitable for binding ofthe compound to the protein. For example, a solution containing compounds can be made to flow tlirough the matrix. The matrix can be washed with a suitable wash buffer to remove unbound compounds and non-specifically bound compounds. Compounds which remain bound can be released by a suitable elution buffer. For example, a change in the ionic strength or pH ofthe elution buffer can lead to a release of compounds. Alternatively, the elution buffer can comprise a release component or components designed to disrupt binding of compounds (e.g., one or more ligands or receptors, as appropriate, or analogs thereof which can disrupt binding or competitively inhibit binding of test compound to the protein).

Fusion proteins comprising all, or a portion of, a protein (e.g., an Eph receptor or an eplirin) linked to a second moiety not occurring in that protein as found in nature can be prepared for use in another embodiment ofthe method. Suitable fusion proteins for this purpose include those in which the second moiety comprises an affinity ligand (e.g., an enzyme, antigen, epitope). The fusion proteins can be produced by inserting the protein (e.g., an Eph receptor or an ephrin) or a portion thereof into a suitable expression vector which encodes an affinity ligand. The expression vector can be introduced into a suitable host cell for expression. Host cells are disrupted and the cell material, containing fusion protein, can be bound to a suitable affinity matrix by contacting the cell material with an affinity matrix under conditions sufficient for binding ofthe affinity ligand portion ofthe fusion protein to the affinity matrix.

In one aspect of this embodiment, a fusion protein can be immobilized on a suitable affinity matrix under conditions sufficient to bind the affinity ligand portion ofthe fusion protein to the matrix, and is contacted with one or more compounds (e.g., a mixture) to be tested, under conditions suitable for binding of compounds to the receptor or ligand protein portion of the bound fusion protein. Next, the affinity matrix with bound fusion protein can be washed with a suitable wash buffer to remove unbound compounds and non-specifically bound compounds without significantly disrupting binding of specifically bound compounds. Compounds which remain bound can be released by contacting the affinity matrix having fusion protein bound thereto with a suitable elution buffer (a compound elution buffer). In this aspect, compound elution buffer can be formulated to permit retention ofthe ftision protein by the affinity matrix, but can be formulated to interfere with binding ofthe compound(s) tested to the receptor or ligand protein portion ofthe fusion protein. For example, a change in the ionic strength or pH ofthe elution buffer can lead to release of compounds, or the elution buffer can comprise a release component or components designed to disrupt binding of compounds to the receptor or ligand protein portion of the fusion protein (e.g., one or more ligands or receptors or analogs thereof which can disrupt binding of compounds to the receptor or ligand protein portion ofthe fusion protein). Immobilization can be performed prior to, simultaneous with, or after contacting the fusion protein with compound, as appropriate. Various permutations ofthe method are possible, depending upon factors such as the compounds tested, the affinity matrix selected, and elution buffer formulation. For example, after the wash step, fusion protein with compound bound thereto can be eluted from the affinity matrix with a suitable elution buffer (a matrix elution buffer). Where the fusion protein comprises a cleavable linker, such as a thrombin cleavage site, cleavage from the affinity ligand can release a portion ofthe fusion with compound bound thereto. Bound compound can then be released from the fusion protein or its cleavage product by an appropriate method, such as extraction.

VI. Methods of Treatment h certain embodiments, the present invention provides methods of inhibiting angiogenesis and methods of treating angiogenesis-associated diseases. In other embodiments, the present invention provides methods of inhibiting or reducing tumor growth and methods of treating an individual suffering from cancer. These methods involve administering to the individual a therapeutically effective amount of one or more polypeptide therapeutic agents as described above. These methods are particularly aimed at therapeutic and prophylactic treatments of animals, and more particularly, humans.

As described herein, angiogenesis-associated diseases include, but are not limited to, angiogenesis-dependent cancer, including, for example, solid tumors, blood born tumors such as leukemias, and tumor metastases; benign tumors, for example hemangiomas, acoustic neuromas, neurofibromas, trachomas, and pyogenic granulomas; inflammatory disorders such as immune and non-immune inflammation; chronic articular rheumatism and psoriasis; ocular angiogenic diseases, for example, diabetic retinopathy, retinopathy of prematurity, macular degeneration, corneal graft rejection, neovascular glaucoma, retrolental fibroplasia, rubeosis; Osier- Webber Syndrome; myocardial angiogenesis; plaque neovascularization; telangiectasia; hemophiliac joints; angiofibroma; and wound granulation and wound healing; telangiectasia psoriasis scleroderma, pyogenic granuloma, cororany collaterals, ischemic limb angiogenesis, corneal diseases, rubeosis, arthritis, diabetic neovascularization, fractures, vasculogenesis, hematopoiesis. It is understood that methods and compositions ofthe invention are also useful for treating any angiogenesis-independent cancers (tumors). As used herein, the term "angiogenesis-independent cancer" refers to a cancer (tumor) where there is no or little neovascularization in the tumor tissue. hi particular, polypeptide therapeutic agents ofthe present invention are useful for treating or preventing a cancer (tumor), including, but not limited to, colon carcinoma, breast cancer, mesothelioma, prostate cancer, bladder cancer, squamous cell carcinoma ofthe head and neck (HNSCC), Kaposi sarcoma, and leukemia.

In certain embodiments of such methods, one or more polypeptide therapeutic agents can be administered, together (simultaneously) or at different times (sequentially). In addition, polypeptide therapeutic agents can be administered with another type of compounds for treating cancer or for inhibiting angiogenesis. In certain embodiments, the subject methods ofthe invention can be used alone. Alternatively, the subject methods may be used in combination with other conventional anti- cancer therapeutic approaches directed to treatment or prevention of proliferative disorders (e.g., tumor). For example, such methods can be used in prophylactic cancer prevention, prevention of cancer recuπence and metastases after surgery, and as an adjuvant of other conventional cancer therapy. The present invention recognizes that the effectiveness of conventional cancer therapies (e.g., chemotherapy, radiation therapy, phototherapy, immunotherapy, and surgery) can be enhanced through the use of a subject polypeptide therapeutic agent. A wide anay of conventional compounds have been shown to have anti-neoplastic activities. These compounds have been used as pharmaceutical agents in chemotherapy to shrink solid tumors, prevent metastases and further growth, or decrease the number of malignant cells in leukemic or bone marrow malignancies. Although chemotherapy has been effective in treating various types of malignancies, many anti-neoplastic compounds induce undesirable side effects. It has been shown that when two or more different treatments are combined, the treatments may work synergistically and allow reduction of dosage of each of the treatments, thereby reducing the detrimental side effects exerted by each compound at higher dosages. In other instances, malignancies that are refractory to a treatment may respond to a combination therapy of two or more different treatments.

When a polypeptide therapeutic agent ofthe present invention is administered in combination with another conventional anti-neoplastic agent, either concomitantly or sequentially, such therapeutic agent is shown to enhance the therapeutic effect ofthe antineoplastic agent or overcome cellular resistance to such anti-neoplastic agent. This allows decrease of dosage of an anti-neoplastic agent, thereby reducing the undesirable side effects, or restores the effectiveness of an anti-neoplastic agent in resistant cells.

Pharmaceutical compounds that may be used for combinatory anti-tumor therapy include, merely to illustrate: aminoglutethimide, amsacrine, anastrozole, asparaginase, beg, bicalutamide, bleomycin, buserelin, busulfan, campothecin, capecitabine, carboplatin, cannustine, chlorambucil, cisplatin, cladribine, clodronate, colchicine, cyclophosphamide, cyproterone, cytarabine, dacarbazine, dactinomycin, daunorubicin, dienestrol, diethylstilbestrol, docetaxel, doxorubicin, epirubicin, estradiol, estramustine, etoposide, exemestane, filgrastim, fludarabine, fludrocortisone, fluorouracil, fluoxymesterone, flutamide, gemcitabine, genistein, goserelin, hydroxyurea, idarubicin, ifosfamide, imatinib, interferon, irinotecan, ironotecan, letrozole, leucovorin, leuprolide, levamisole, lomustine, mechlorethamine, medroxyprogesterone, megesfrol, melphalan, mercaptopurine, mesna, methotrexate, mitomycin, mitotane, mitoxantrone, nilutamide, nocodazole, octreotide, oxaliplatin, paclitaxel, pamidronate, pentostatin, plicamycin, porfimer, procarbazine, raltitrexed, rituximab, sfreptozocin, suramin, tamoxifen, temozolomide, teniposide, testosterone, thioguanine, thiotepa, titanocene dichloride, topotecan, trastuzumab, tretinoin, vinblastine, vincristine, vindesine, and vinorelbine.

These chemotherapeutic anti-tumor compounds may be categorized by their mechanism of action into, for example, following groups: anti-metabolites/anti-cancer agents, such as pyrimidine analogs (5-fluorouracil, floxuridine, capecitabine, gemcitabine and cytarabine) and purine analogs, folate antagonists and related inhibitors (mercaptopurine, thioguanine, pentostatin and 2-chlorodeoxyadenosine (cladribine)); antiproliferative/antimitotic agents including natural products such as vinca alkaloids (vinblastine, vincristine, and vinorelbine), microtubule disrupters such as taxane (paclitaxel, docetaxel), vincristin, vinblastin, nocodazole, epothilones and navelbine, epidipodophyllotoxins (etoposide, teniposide), DNA damaging agents (actinomycin, amsacrine, anthracychnes, bleomycin, busulfan, camptothecin, carboplatin, chlorambucil, cisplatin, cyclophosphamide, cytoxan, dactinomycin, daunorubicin, doxorubicin, epirubicin, hexamethyhnelamineoxaliplatin, iphosphamide, melphalan, merchlorehtamine, mitomycin, mitoxantrone, nitrosourea, plicamycin, procarbazine, taxol, taxotere, teniposide, triethylenethiophosphoramide and etoposide (VP16)); antibiotics such as dactinomycin (actinomycin D), daunorubicin, doxorubicin (adriamycin), idarubicin, anthracychnes, mitoxantrone, bleomycins, plicamycin (mithramycin) and mitomycin; enzymes (L- asparaginase which systemically metabolizes L-asparagine and deprives cells which do not have the capacity to synthesize their own asparagine); antiplatelet agents; antiproliferative/antimitotic alkylating agents such as nitrogen mustards (mechlorethamine, cyclophosphamide and analogs, melphalan, chlorambucil), ethylenimines and methylmelamines (hexamethylmelamine and thiotepa), alkyl sulfonates-busulfan, nitrosoureas (cannustine (BCNU) and analogs, sfreptozocin), trazenes - dacarbazinine (DTIC); antiproliferative/antimitotic antimetabolites such as folic acid analogs (methotrexate); platinum coordination complexes (cisplatin, carboplatin), procarbazine, hydroxyurea, mitotane, aminoglutethimide; hormones, hormone analogs (estrogen, tamoxifen, goserelin, bicalutamide, nilutamide) and aromatase inhibitors (lefrozole, anastrozole); anticoagulants (heparin, synthetic heparin salts and other inhibitors of thrombin); fibrinolytic agents (such as tissue plasminogen activator, streptokinase and urokinase), aspirin, dipyridamole, ticlopidine, clopidogrel, abciximab; antimigratory agents; antisecretory agents (breveldin); immunosuppressives (cyclosporine, tacrolimus (FK-506), sirolimus (rapamycin), azathioprine, mycophenolate mofetil); anti-angiogenic compounds (TNP-470, genistein) and growth factor inhibitors (vascular endothelial growth factor (VEGF) inhibitors, fibroblast growth factor (FGF) inhibitors); angiotensin receptor blocker; nitric oxide donors; anti-sense oligonucleotides; antibodies (trastuzumab); cell cycle inhibitors and differentiation inducers (tretinoin); mTOR inhibitors, topoisomerase inhibitors (doxorubicin (adriamycin), amsacrine, camptothecin, daunorubicin, dactinomycin, eniposide, epirubicin, etoposide, idarubicin and mitoxantrone, topotecan, irinotecan), corticosteroids (cortisone, dexamethasone, hydrocortisone, methylpednisolone, prednisone, and prenisolone); growth factor signal transduction kinase inhibitors; mitochondrial dysfunction inducers and caspase activators; and chromatin disruptors.

hi certain embodiments, pharmaceutical compounds that may be used for combinatory anti-angiogenesis therapy include: (1) inhibitors of release of "angiogenic molecules," such as bFGF (basic fibroblast growth factor); (2) neutralizers of angiogenic molecules, such as an anti-βbFGF antibodies; and (3) inhibitors of endothelial cell response to angiogenic stimuli, including collagenase inhibitor, basement membrane turnover inhibitors, angiostatic steroids, fungal-derived angiogenesis inhibitors, platelet factor 4, thrombospondin, arthritis drugs such as D-penicillamine and gold thiomalate, vitamin D₃ analogs, alpha-interferon, and the like. For additional proposed inhibitors of angiogenesis, see Blood et al., Bioch. Biophys. Acta., 1032:89-118 (1990), Moses et al., Science, 248:1408- 1410 (1990), Ingber et al, Lab. Invest., 59:44-51 (1988), and U.S. Pat. Nos. 5,092,885, 5,112,946, 5,192,744, 5,202,352, and 6573256. In addition, there are a wide variety of compounds that can be used to inhibit angiogenesis, for example, peptides or agents that block the VEGF-mediated angiogenesis pathway, endostatin protein or derivatives, lysine binding fragments of angiostatin, melanin or melanin-promoting compounds, plasminogen fragments (e.g., Kringles 1-3 of plasminogen), tropoin subunits, antagonists of vitronectin α_vβ₃, peptides derived from Saposin B, antibiotics or analogs (e.g., tetracycline, or neomycin), dienogest-containing compositions, compounds comprising a MetAP-2 inhibitory core coupled to a peptide, the compound EM-138, chalcone and its analogs, and naaladase inhibitors. See, for example, U.S. Pat. Nos. 6,395,718, 6,462,075, 6,465,431, 6,475,784, 6,482,802, 6,482,810, 6,500,431, 6,500,924, 6,518,298, 6,521,439, 6,525,019, 6,538,103, 6,544,758, 6,544,947, 6,548,477, 6,559,126, and 6,569,845.

Depending on the nature ofthe combinatory therapy, administration ofthe polypeptide therapeutic agents ofthe invention may be continued while the other therapy is being administered and/or thereafter. Administration ofthe polypeptide therapeutic agents may be made in a single dose, or in multiple doses. In some instances, administration ofthe polypeptide therapeutic agents is commenced at least several days prior to the conventional therapy, while in other instances, administration is begun either immediately before or at the time ofthe adminisfration ofthe conventional therapy.

VII. Methods of Administration and Pharmaceutical Compositions hi certain embodiments, the subject polypeptide therapeutic agents (e.g., soluble polypeptides or antibodies) ofthe present invention are formulated with a pharmaceutically acceptable carrier. Such therapeutic agents can be administered alone or as a component of a pharmaceutical formulation (composition). The compounds may be foπnulated for administration in any convenient way for use in human or veterinary medicine. Wetting agents, emulsifiers and lubricants, such as sodium lauryl sulfate and magnesium stearate, as well as coloring agents, release agents, coating agents, sweetening, flavoring and perfuming agents, preservatives and antioxidants can also be present in the compositions.

Formulations ofthe subject polypeptide therapeutic agents include those suitable for oral/ nasal, topical, parenteral, rectal, and/or intravaginal administration. The formulations may conveniently be presented in unit dosage form and may be prepared by any methods well known in the art of pharmacy. The amount of active ingredient which can be combined with a canier material to produce a single dosage form will vary depending upon the host being treated, the particular mode of adminisfration. The amount of active ingredient which can be combined with a carrier material to produce a single dosage form will generally be that amount ofthe compound which produces a therapeutic effect.

In certain embodiments, methods of preparing these formulations or compositions include combining another type of anti-tumor or anti-angiogenesis therapeutic agent and a carrier and, optionally, one or more accessory ingredients. In general, the formulations can be prepared with a liquid carrier, or a finely divided solid carrier, or both, and then, if necessary, shaping the product.

Formulations for oral adminisfration may be in the form of capsules, cachets, pills, tablets, lozenges (using a flavored basis, usually sucrose and acacia or tragacanth), powders, granules, or as a solution or a suspension in an aqueous or non-aqueous liquid, or as an oil-in- water or water-in-oil liquid emulsion, or as an elixir or syrup, or as pastilles (using an inert base, such as gelatin and glycerin, or sucrose and acacia) and/or as mouth washes and the like, each containing a predeteπnined amount of a subject polypeptide therapeutic agent as an active ingredient. In solid dosage forms for oral administration (capsules, tablets, pills, dragees, powders, granules, and the like), one or more polypeptide therapeutic agents ofthe present invention may be mixed with one or more pharmaceutically acceptable earners, such as sodium citrate or dicalcium phosphate, and/or any ofthe following: (1) fillers or extenders, such as starches, lactose, sucrose, glucose, mannitol, and/or silicic acid; (2) binders, such as, for example, carboxymethylcellulose, alginates, gelatin, polyvinyl pyπolidone, sucrose, and/or acacia; (3) humectants, such as glycerol; (4) disintegrating agents, such as agar-agar, calcium carbonate, potato or tapioca starch, alginic acid, certain silicates, and sodium carbonate; (5) solution retarding agents, such as paraffin; (6) absorption accelerators, such as quaternary ammonium compounds; (7) wetting agents, such as, for example, cetyl alcohol and glycerol monostearate; (8) absorbents, such as kaolin and bentonite clay; (9) lubricants, such a talc, calcium stearate, magnesium stearate, solid polyethylene glycols, sodium lauryl sulfate, and mixtures thereof; and (10) coloring agents. In the case of capsules, tablets and pills, the pharmaceutical compositions may also comprise buffering agents. Solid compositions of a similar type may also be employed as fillers in soft and hard-filled gelatin capsules using such excipients as lactose or milk sugars, as well as high molecular weight polyethylene glycols and the like.

Liquid dosage forms for oral administration include pharmaceutically acceptable emulsions, microemulsions, solutions, suspensions, syrups, and elixirs, hi addition to the active ingredient, the liquid dosage forms may contain inert diluents commonly used in the art, such as water or other solvents, solubilizing agents and emulsifiers, such as ethyl alcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1,3 -butylene glycol, oils (in particular, cottonseed, groundnut, corn, geπn, olive, castor, and sesame oils), glycerol, tetrahydrofuryl alcohol, polyethylene glycols and fatty acid esters of sorbitan, and mixtures thereof. Besides inert diluents, the oral compositions can also include adjuvants such as wetting agents, emulsifying and suspending agents, sweetening, flavoring, coloring, perfuming, and preservative agents.

Suspensions, in addition to the active compounds, may contain suspending agents such as ethoxylated isostearyl alcohols, poiyoxyethylene sorbitol, and sorbitan esters, microcrystalline cellulose, aluminum metahydroxide, bentonite, agar-agar and tragacanth, and mixtures thereof.

In particular, methods ofthe invention can be administered topically, either to skin or to mucosal membranes such as those on the cervix and vagina. This offers the greatest opportunity for direct delivery to tumor with the lowest chance of inducing side effects. The topical formulations may further include one or more ofthe wide variety of agents known to be effective as skin or stratum corneum penetration enhancers. Examples of these are 2- pyπolidone, N-methyl-2-pynolidone, dimethylacetamide, dimethylformamide, propylene glycol, methyl or isopropyl alcohol, dimethyl sulfoxide, and azone. Additional agents may further be included to make the formulation cosmetically acceptable. Examples of these are fats, waxes, oils, dyes, fragrances, preservatives, stabilizers, and surface active agents. Keratolytic agents such as those known in the art may also be included. Examples are salicylic acid and sulfur.

Dosage forms for the topical or transdermal administration include powders, sprays, ointments, pastes, creams, lotions, gels, solutions, patches, and inhalants. The subject polypeptide therapeutic agents may be mixed under sterile conditions with a pharmaceutically acceptable carrier, and with any preservatives, buffers, or propellants which may be required. The ointments, pastes, creams and gels may contain, in addition to a subject polypeptide agent, excipients, such as animal and vegetable fats, oils, waxes, paraffins, starch, tragacanth, cellulose derivatives, polyethylene glycols, silicones, bentonites, silicic acid, talc and zinc oxide, or mixtures thereof.

Powders and sprays can contain, in addition to a subject polypeptide therapeutic agent, excipients such as lactose, talc, silicic acid, aluminum hydroxide, calcium silicates, and polyamide powder, or mixtures of these substances. Sprays can additionally contain customary propellants, such as chlorofluorohydrocarbons and volatile unsubstituted hydrocarbons, such as butane and propane. Phannaceutical compositions suitable for parenteral administration may comprise one or more polypeptide therapeutic agents in combination with one or more pharmaceutically acceptable sterile isotonic aqueous or nonaqueous solutions, dispersions, suspensions or emulsions, or sterile powders which maybe reconstituted into sterile injectable solutions or dispersions just prior to use, which may contain antioxidants, buffers, bacteriostats, solutes which render the formulation isotonic with the blood ofthe intended recipient or suspending or thickening agents. Examples of suitable aqueous and nonaqueous carriers which may be employed in the pharmaceutical compositions ofthe invention include water, ethanol, polyols (such as glycerol, propylene glycol, polyethylene glycol, and the like), and suitable mixtures thereof, vegetable oils, such as olive oil, and injectable organic esters, such as ethyl oleate. Proper fluidity can be maintained, for example, by the use of coating materials, such as lecithin, by the maintenance ofthe required particle size in the case of dispersions, and by the use of surfactants.

These compositions may also contain adjuvants, such as preservatives, wetting agents, emulsifying agents and dispersing agents. Prevention ofthe action of microorganisms may be ensured by the inclusion of various antibacterial and antifungal agents, for example, paraben, chlorobutanol, phenol sorbic acid, and the like. It may also be desirable to include isotonic agents, such as sugars, sodium chloride, and the like into the compositions. In addition, prolonged absorption ofthe injectable pharmaceutical form may be brought about by the inclusion of agents which delay absorption, such as aluminum monostearate and gelatin.

Injectable depot forms are made by forming microencapsule matrices of one or more polypeptide therapeutic agents in biodegradable polymers such as polylactide-polyglycolide. Depending on the ratio of drug to polymer, and the nature ofthe particular polymer employed, the rate of drug release can be controlled. Examples of other biodegradable polymers include poly(orthoesters) and poly(anhydrides). Depot injectable formulations are also prepared by entrapping the drug in liposomes or microemulsions which are compatible with body tissue.

Formulations for intravaginal or rectally administration may be presented as a suppository, which may be prepared by mixing one or more compounds ofthe invention with one or more suitable nonirritating excipients or carriers comprising, for example, cocoa butter, polyethylene glycol, a suppository wax or a salicylate, and which is solid at room temperature, but liquid at body temperature and, therefore, will melt in the rectum or vaginal cavity and release the active compound.

In other embodiments, the polypeptide therapeutic agents ofthe instant invention can be expressed within cells from eukaryotic promoters. For example, a soluble polypeptide of EphB4 or Ephrin B2 can be expressed in eukaryotic cells from an appropriate vector. The vectors are preferably DNA plasmids or viral vectors. Viral vectors can be constructed based on, but not limited to, adeno-associated virus, refrovirus, adenovirus, or alphavirus. Preferably, the vectors stably introduced in and persist in target cells. Alternatively, viral vectors can be used that provide for transient expression. Such vectors can be repeatedly administered as necessary. Delivery of vectors encoding the subject polypeptide therapeutic agent can be systemic, such as by intravenous or intramuscular administration, by administration to target cells ex-planted from the patient followed by reintroduction into the patient, or by any other means that would allow for introduction into the desired target cell (for a review see Couture et al., 1996, TIG., 12, 510).

EXEMPLIFICATION

The invention now being generally described, it will be more readily understood by reference to the following examples, which are included merely for purposes of illustration of certain aspects and embodiments ofthe present invention, and are not intended to limit the invention.

Example 1. Soluble derivatives ofthe extracellular domains of human Ephrin B2 and EphB4 proteins

Soluble derivatives of the extracellular domains of human Ephrin B2 and EphB4 proteins represent either truncated full-length predicted extracellular domains of Ephrin B2 (B4ECv3, B2EC) or translational fusions of the domains with constant region of human immunoglobulins (IgGl Fc fragment), such as B2EC-FC, B4ECv2-FC and B4ECv3-FC. Representative human Ephrin B2 constructs and human EphB4 constructs are shown Figures 14 and 15.

The cDNA fragments encoding these recombinant proteins were subcloned into mammalian expression vectors, expressed in transiently or stably transfected mammalian cell lines and purified to homogeneity as described in detail in Materials and Methods section (see below). Predicted amino acid sequences ofthe proteins are shown in Figures 1-5. High purity ofthe isolated proteins and their recognition by the coπesponding anti-Ephrin B2 and anti- EphB4 monoclonal or polyclonal antibodies were confirmed. The recombinant proteins exhibit the expected liigh-affmity binding, binding competition and specificity properties with their corresponding binding partners as coπoborated by the biochemical assays (see e.g., Figures 6-8).

Such soluble derivative proteins human Ephrin B2 and EphB4 exhibit potent biological activity in several cell-based assays and in vivo assays which measure angiogenesis or anti-cancer activities, and are therefore perspective drug candidates for anti-angiogenic and anti-cancer therapy. B4ECv3 as well as B2EC and B2EC-FC proteins blocked chemotaxis of human endothelial cells (as tested with umbilical cord and hepatic AECs or VECs), with a decrease in degradation ofthe extracellular matrix, Matrigel, and a decrease in migration in response to growth factor stimuli (Figures 9-11). B4ECv3 and B2EC-FC proteins have potent anti-angiogenic effect as demonstrated by their inhibition of endothelial cell tube formation (Figures 12-13).

Materials and Methods

1) Mammalian expression vectors for producing recombinant soluble derivatives of Ephrin B2 and Eph B4

Plasmids vectors for expressing recombinant soluble derivatives of Ephrin B2 and EphB4 were based on pEF6/V5-His-TOPO vector (Invitrogen), pIG (Novagen) or pRK5. pEF6/V5-His-TOPO contains human elongation factor la enhancer/promoter and blasticidin resistance marker. pIG vector is designed for high-level expression of protein fusions with Fc portion of human IgGlunder CMV promoter confrol and pRK5 is a general purpose CMV promoter-containing mammalian expression vector. To generate plasmid construct pEF6- B4EC-NT, cDNA fragment of human EphB4 was amplified by PCR using oligo primers 5'- GGATCCGCC ATGGAGCTC CGGGTGCTGCT-3' and 5'-TGGATCCCT GCTCCCGC CAGCCCTCG CTCTCATCCA-3', and TOPO-cloned into pEF6/V5-His-TOPO vector. pEF6-hB4ECv3 was derived from pEF6-B4ECNT by digesting the plasmid DNA with EcoRV and BstBI, filling-in the ends with Klenow enzyme and religating the vector. Recombinant EphB4 derivative encoded by pEF6-B4EC-NT does not contain epitope- or purification tags, while the similar B4ECv3 protein encoded by pEF6-hB4ECv3 contains V5 epitope tag and 6xHis tag on its C-terminus to facilitate purification from conditioned media. Plasmid construct pEF6-hB2EC was created by PCR amplification of Ephrin B2 cDNA using oligo primers 5'- TGGATCCAC CATGGCTGT GAGAAGGGAC-3' plus 5'- ATTAATGGTGATGGT GAT GATGACTAC CCACTTCGG AACCGAGGATGTTGTTC- 3' and TOPO-cloning into ρEF6/V5-His-TOPO vector. Plasmid construct pIG-hB2EC-FC was created by PCR amplification of Eplirin B2 cDNA with oligo primers 5 '-

TAAAGCTTCCGCCATGG CTGTGAGAAGGGAC-3 ' and 5'-TAGGATCCACTTCGGA ACCGAGGATGTTGTT CCC-3' , followed by TOPO-cloning and sequencing the resulting PCR fragment with consecutive subcloning in pIG hlgGl Fc fusion expression vector cut with Bam HI and Hind in. Similarly, pIG-hB2EC and pIG-hB4ECv3 were generated by PCR amplifying portions of EphB4 ECD cDNA using oligo primers 5 ' - ATAAGCTTCC

GCCATGGAGC TCCGGGTGCTG-3' plus 5'-TTGGATCCTGCTCCCG CCAGCCCTCGC TCTCATC-3' with consecutive subcloning into pIG hlgGl Fc fusion expression vector cut with Bam HI and Hind III. Predicted sequences ofthe proteins encoded by the vectors described above are shown in Figures 1-5.

2) Mammalian cell culture and transfections

HEK293T (human embryonic kidney line) cells were maintained in DMEM with 10% dialyzed fetal calf serum and 1%> penicillin/streptomycin/neomycin antibiotics. Cells were maintained at 37 °C in a humidified atmosphere of 5% CO₂/95% air. Transfections were performed using Lipofectamine 2000 reagent (Invitrogen) according to the manufacturer's protocol. One day before transfections, 293T cells were seeded at a high density to reach 80% confluence at the time of transfection. Plasmid DNA and Lipofectamine reagent at 1:3 ratio were diluted in Opti-MEM I reduced serum medium (Invitrogen) for 5 min and mixed together to form DNA:Lipofectamine complex. For each 10 cm culture dish, 10 μg of plasmid DNA was used. After 20 min, above complex was added directly to cells in culture medium. After 16 hours of transfection, medium was aspirated, washed once with serum free DMEM and replaced with serum free DMEM. Secreted proteins were harvested after 48 hours by collecting conditional medium. Conditional medium was clarified by centrifugation at 10,000 g for 20 min, filtered through 0.2 μm filter and used for purification.

3) Generating stable cell lines

To create stable cell lines producing EphB4ECv3 and EphB4ECnt HEK293 or

HEK293T cells were transfected with either pEF6-B4ECv3 or pEF6-B4EC-NT plasmid constructs as described above and selected using antibiotic Blasticidin. After 24 hours of transfection, cells were seeded at low density. Next day, cells were treated with 10 μg/ml of Blasticidin. After two weeks of drug selection, surviving cells were pooled and selected further for single cell clone expansion. After establishing stable cells, they were maintained at 4 μg/ml Blasticidin. Conditioned media were tested to confirm expression and secretion of the respective recombinant proteins. Specificity of expression was confirmed by Western blot with anti-B4 mono- or polyclonal ABs and B2EC-AP reagent binding and competition assays.

4) Protein purification

HEK293 cells were transiently transfected with a plasmid encoding secreted fonn of

EphB4ectodomain (B4ECv3). Conditional media was harvested and supplemented with 10 mM imidazole, 0.3 M NaCl and centrifuged at 20,000g for 30 min to remove cell debris and insoluble particles. 80 ml of obtained supernatant were applied onto the pre-equilibrated column with 1 ml of Ni-NTA-agarose (Qiagen) at the flow rate of 10 ml/h. After washing the column with 10 ml of 50 mM Tris-HCl, 0.3 M NaCl and 10 mM imidazole, pH 8, remaining proteins were eluted with 3 ml of 0.25 M imidazole. Eluted proteins were dialyzed against 20 mM Tris-HCl, 0.15 M NaCl, pH 8 overnight. Purity and identity of B4ECv3 was verified by PAGE/Coomassie G-250 and Western blot with anti-Eph.B4 antibody. Finally, the concentration of B4ECv3 was measured, and the protein was aliquoted and stored at -70 °C.

B4EC-FC protein and B2EC-FC protein were similarly purified.

5) Biochemical Assays

A. binding; assay

10 μl of Ni-NTA- Agarose were incubated in microcentrifuge tubes with 50 μl of indicated amount of B4ECv3 diluted in binding buffer BB (20 mM Tris-HCl, 0.15 M NaCl, 0.1%) bovine serum albumin pH 8) After incubation for 30 min on shaking platform, Ni-NTA beads were washed twice with 1.4 ml of BB, followed by application of 50 μl of B2-AP in the final concentration of 50 nM. Binding was performed for 30 min on shaking platform, and then tubes were centrifuged and washed one time with 1.4 ml of BB. Amount of precipitated AP was measured colorimetrically after application of PNPP. B. Iinhibition assay

Inhibition in solution. Different amounts of B4ECv3 diluted in 50 μl of BB were pre- incubated with 50 μl of 5 nM B2EC-AP reagent (protein fusion of Ephrin B2 ectodomain with placental alkaline phosphatase). After incubation for 1 h, unbound B2EC-AP was precipitated with 5,000 HEK293 cells expressing membrane-associated full-length EphB4 for 20 min. Binding reaction was stopped by dilution with 1.2 ml of BB, followed by centrifugation for 10 min. Supernatants were discarded and alkaline phosphatase activities associated with collected cells were measured by adding para-nitrophenyl phosphate (PNPP) substrate.

Cell based inhibition. B4ECv3 was serially diluted in 20 mM Tris-HCl, 0.15 M NaCl,

0.1%) BSA, pH 8 and mixed with 5,000 HEK293 cells expressing membrane-associated full- length Ephrin B2. After incubation for 1 h, 50 μl of 5 nM B4EC-AP reagent (protein fusion of EphB4 ectodomain with placental alkaline phosphatase were added into each tube for 30 min to detect unoccupied Ephrin B2 binding sites. Binding reactions were stopped by dilution with 1.2 ml of BB and centrifugation. Colorimetric reaction of cell-precipitated AP was developed with PNPP substrate.

C. B4EC-FC binding assay

Protein A-agarose based assay. 10 μl of Protein A-agarose were incubated in Eppendorf tubes with 50 μl of indicated amount of B4EC-FC diluted in binding buffer BB (20 mM Tris-HCl, 0.15 M NaCl, 0.1 % BSA pH 8). After incubation for 30 min on shaking platform, Protein AAagarose beads were washed twice with 1.4 ml of BB, followed by application of 50 μl of B2ECAP reagent at the final concentration of 50 nM. Binding was performed for 30 min on shaking platform, and then tubes were centrifuged and washed once with 1.4 ml of BB. Colorimetric reaction of precipitated AP was measured after application of PNPP (Fig. 6).

Nitrocellulose based assay. B4EC-FC was serially diluted in 20 mM Tris-HCl, 0.15 M NaCl, 50 μg/ml BSA, pH 8. 2 μl of each fraction were applied onto nitrocellulose strip and spots were dried out for 3 min. Nitrocellulose strip was blocked with 5%> non-fat milk for 30 min, followed by incubation with 5 nM B2EC-AP reagent. After 45 min incubation for binding, nitrocellulose was washed twice with 20 mM Tris-HCl, 0.15 M NaCl, 50 μg/ml BSA, pH 8 and color was developed by application of alkaline phosphatase substrate Sigma Fast (Sigma).

P. B4EC-FC inhibition assay

Inhibition in solution. See above, for B4ECv3. The results were shown in Figure 7.

Cell based inhibition. See above, for B4ECv3.

E. B2EC-FC binding; assay

Protein-A-agarose based assay. See above, for B4EC-FC. The results were shown in Figure 8.

Nitrocellulose based assay. See above, for B4EC-FC.

6) Cell-Based Assays

A. Growth Inhibition Assay

Human umbilical cord vein endothelial cells (HUVEC) (1.5x103) are plated in a 96- well plate in 100 μl of EBM-2 (Clonetic # CC3162). After 24 hours (day 0), the test recombinant protein (100 μl) is added to each well at 2X the desired concentration (5-7 concentration levels) in EBM-2 medium. On day 0, one plate is stained with 0.5% crystal violet in 20% methanol for 10 minutes, rinsed with water, and air-dried. The remaining plates are incubated for 72 h at 37 °C. After 72 h, plates are stained with 0.5%) crystal violet in 20% methanol, rinsed with water and airdried. The stain is eluted with 1:1 solution of ethanol: 0.1 M sodium citrate (including day 0 plate), and absorbance is measured at 540 nm with an ELISA reader (Dynatech Laboratories). Day 0 absorbance is subtracted from the 72 h plates and data is plotted as percentage of control proliferation (vehicle treated cells). IC50 (drug concentration causing 50%> inhibition) is calculated from the plotted data.

B. Cord Formation Assay (Endothelial Cell Tube Formation Assay)

Matrigel (60 μl of 10 mg/ml; Collaborative Lab # 35423) is placed in each well of an ice-cold 96-well plate. The plate is allowed to sit at room temperature for 15 minutes then incubated at 37 °C for 30 minutes to permit the matrigel to polymerize. In the mean time, HUVECs are prepared in EGM-2 (Clonetic # CC3162) at a concentration of 2X10⁵ cells/ml. The test compound is prepared at 2X the desired concenfration (5 concentration levels) in the same medium. Cells (500 μl) and 2X drug (500 μl) is mixed and 200 μl of this suspension are placed in duplicate on the polymerized matrigel. After 24 h incubation, triplicate pictures are taken for each concentration using a Bioquant Image Analysis system. Drug effect (IC50) is assessed compared to untreated controls by measuring the length of cords formed and number ofjunctions.

C. Cell Migration Assay

Migration is assessed using the 48-well Boyden chamber and 8 μm pore size collagen-coated (10 μg/ml rat tail collagen; Collaborative Laboratories) polycarbonate filters (Osmonics, Inc.). The bottom chamber wells receive 27-29 μl of DMEM medium alone (baseline) or medium containing chemo-attractant (bFGF, VEGF or Swiss 3T3 cell conditioned medium). The top chambers receive 45 μl of HUVEC cell suspension (1X10 cells/ml) prepared in DMEM+1% BSA with or without test compound. After 5 h incubation at 37 °C, the membrane is rinsed in PBS, fixed and stained in Diff-Quick solutions. The filter is placed on a glass slide with the migrated cells facing down and cells on top are removed using a Kimwipe. The testing is perfonned in 4-6 replicates and five fields are counted from each well. Negative unstimulated control values are subtracted from stimulated control and drug treated values and data is plotted as mean migrated cell ± S.D. IC50 is calculated from the plotted data.

Example 2. Extracellular domain fragments of EphB4 receptor inhibit angiogenesis and tumor growth.

A. Globular domain of EphB4 is required for EphrinB2 binding and for the activity of EplιB4-derived soluble proteins in endothelial tube formation assay.

To identify subdomain(s) ofthe ectopic part of EphB4 necessary and sufficient for the anti-angiogenic activity ofthe soluble recombinant derivatives ofthe receptor, four recombinant deletion variants of EphB4EC were produced and tested (Fig. 16). Extracellular part of EphB4, similarly to the other members of EphB and EphA receptor family, contains N-terminal ligand-binding globular domain followed by cysteine-rich domain and two fibronectin type III repeats (FNIII). In addition to the recombinant B4-GCF2 protein containing the complete ectopic part of EphB4, we constructed three deletion variants of

EphB4EC containing globular domain and Cys-rich domain (B4-GC); globular, Cys-rich and the first FNIII domain (GCF1) as well as the ECD version with deleted globular domain (CF2). Our attempts to produce several versions of truncated EphB4EC protein containing the globular domain alone were not successful due to the lack of secretion of proteins expressed from all these constructs and absence of ligand binding by the intracellularly expressed recombinant proteins. In addition, a non-tagged version of B4-GCF2, called GCF2- F, containing complete extracellular domain of EphB4 with no additional fused amino acids was expressed, purified and used in some ofthe experiments described here.

All four C-terminally 6xHis tagged recombinant proteins were preparatively expressed in transiently transfected cultured mammalian cells and affinity purified to homogeneity from the conditioned growth media using chromatography on Ni²⁺-chelate resin (Fig. 17). Apparently due to their glycosylation, the proteins migrate on SDS-PAAG somewhat higher than suggested by their predicted molecular weights of 34.7 kDa (GC), 41.5 (CF2), 45.6 kDa (GCF1) and 57.8 kDa (GCF2). Sequence ofthe extracellular domain of human EphB4 contains three predicted N-glycosylation sites (NXS/T) which are located in the Cys-rich domain, within the first fibronectin type III repeat and between the first and the second fibronectin repeats.

To confirm ability ofthe purified recombinant proteins to bind Ephrin B2, they were tested in an in vitro binding assay. As expected, GC, GCF1 and GCF2, but not CF2 are binding the cognate ligand Ephrin B2 as confirmed by interaction between Ephrin B2 - alkaline phosphatase (Eplirin B2-AP) fusion protein with the B4 proteins immobilized on Ni^2+"resin or on nitrocellulose membrane (Fig. 17).

All four proteins were also tested for their ability to block ligand-dependent dimerization and activation of Eph B4 receptor kinase in PC3 cells. The PC3 human prostate cancer cell line is known to express elevated levels of human Eph B4. Stimulation of PC3 cells with Eplirin B2 IgG Fc fusion protein leads to a rapid induction of tyrosine phosphorylation ofthe receptor. However, preincubation ofthe ligand with GCF2, GCF1 or GC, but not CF2 proteins suppresses subsequent EphB4 autophosphorylation. Addition ofthe proteins alone to the PC3 cells or preincubation ofthe cells with the proteins followed by changing media and adding the ligand does not affect EphB4 phosphorylation status. Further, we found that globular domain of EphB4 is required for the activity of

EphB4-derived soluble proteins in endothelial tube formation assay.

B. Effects of soluble EρhB4 on HUV/AEC in vitro. Initial experiments were performed to determine whether soluble EphB4 affected the three main stages in the angiogenesis pathway. These were carried out by establishing the effects of soluble EphB4 on migration / invasion, proliferation and tubule formation by HUV/AEC in vitro. Exposure to soluble EphB4 significantly inhibited both bFGF and VEGF-induced migration in the Boyden chamber assay in a dose-dependent manner, achieving significance at nM (Fig. 18). Tubule formation by HUV/AECS on wells coated with Matrigel was significantly inhibited by soluble EpliB4 in a dose-dependent manner in both the absence and presence of bFGF and VEGF (Fig. 19). We also assessed in vitro, whether nM of soluble EphB4 was cytotoxic for HUVECS. Soluble EphB4 was found to have no detectable cytotoxic effect at these doses, as assessed by MTS assay (Fig. 20).

C. Soluble EphB4 receptor Inhibits Vascularization of Matrigel Plugs, in vivo

To demonstrate that soluble EphB4 can directly inhibit angiogenesis in vivo, we performed a murine matrigel plug experiment. Matrigel supplemented with bFGF and VEGF with and without soluble EphB4 was injected s.c. into Balb/C nu/numice, forming semi-solid plugs, for six days. Plugs without growth factors had virtually no vascularization or vessel structures after 6 days (Fig. 21). In contrast, plugs supplemented with bFGF and VEGF had extensive vascularization and vessels throughout the plug. Plugs taken from mice treated with μg of soluble EphB4 had markedly reduced vascularization of plugs, comparable to plugs without growth factor (Fig. 21). Furthermore, histological examination of plugs showed decreased vessel staining (Fig. 21). Treatment at 0 μg/dose significantly inliibited the amount of infiltration in Matrigel plugs compared to control (Fig. 21).

We examined EphB4 receptor phosphorylation in HUVECs by performing Western blot analyses with lysates from soluble EphB4-treated cells and antibodies against phosphor- tyrosine. We found that soluble EphB4 treatment of serum-starved HUVECs stimulated a rapid and transient decrease in the level of phosphorylated EphB4, in the presence of

EphrinB2Fc, EphB4 ligand dimer. Ephrin B2Fc without the soluble EphB4 protein induced phosphorylation of EphB4 receptor (Fig. 22).

D. Effects of soluble EphB4 on tumor growth, in vitro.

We found that soluble EphB4 inhibits the growth of SCC 15 tumors grown in Balb/C Nu/Nu mice (Fig. 23).

E. Soluble EphB4 inhibited corneal neovascularization To further investigate the antiangiogenic activity of soluble EphB4 in vivo, we studied the inhibitory effect of adminisfration of soluble EphB4 on neovascularization in the mouse cornea induced by bFGF. Hydron Pellets implanted into corneal micropocket could induce angiogenesis, in the presence of growth factors, in a typically avascular area. The angiogenesis response in mice cornea was moderate, the appearance of vascular buds was delayed and the new capillaries were sparse and grew slowly. Compared with the control group, on day 7 of implantation, the neovascularization induced by bFGF in mice cornea was markedly inliibited in soluble EphB4-treated group (Fig. 24).

F. Effects of soluble EphB4 on tumor growth, in vivo. The same model was used to determine the effects of soluble EphB4 in vivo. SCC 15 tumors implanted subcutaneously, pre-incubated with matrigel and with or w/o growth factors, as well as implanted sc alone, and mice treated sc or ip daily with l-5ug of soluble EphB4 were caπied out.

Tumors in the control group continued to grow steadily over the treatment period, reaching a final tumor volume of mm3. However, animals injected with soluble EphB4 exhibited a significantly (p<0.0/) reduced growth rate, reaching a final tumor volume of only mm3 (Fig. 25). Similar results were obtained in two further cohorts of such tumor-bearing mice. Soluble EphB4 administration appeared to be well tolerated in vivo, with no significant effect on body weight or the general well-being ofthe animals (as determined by the absence of lethargy, intermittent hunching, tremors or disturbed breathing patterns).

G. Effects of soluble EphB4 on tumor histology.

Histological analysis revealed the presence of a central area of necrosis in all SCC15 tumors, which was usually suπounded by a viable rim of tumor cells um in width. The central necrotic areas were frequently large and confluent and showed loss of cellular detail. Necrosis, assessed as a percentage of tumor section area, was significantly (p<0.02) more extensive in the soluble EphB4-treated group (% necrosis in freated vs. control). To detennine whether the reduced volume of soluble EphB4 treated tumors was due to an effect of this protein on the tumor vascular supply, endothelial cells in blood vessels were identified in tumor sections using immunostaining with an anti-platelet cell adhesion molecule (PECAM-1; CD31) antibody (Fig. 26) and the density of microvessels was assessed.

Microvessel density was similar in the outer viable rim of tumor cells (the unifonn layer of cells adjacent to the tumor periphery with well defined nuclei) in control and soluble EphB4- treated tumors. Microvessel density was significantly in the inner, less viable region of tumor cells abutting the necrotic central areas in soluble EphB4-treated than control tumors. Fibrin deposition, as identified by Masson's Trichrome staining, was increased in and around blood vessels in the inner viable rim and the central necrotic core of soluble EphB4 treated than control tumors. In the outer viable rim of soluble EphB4 treated tumors, although the vessel lumen remained patent and contained red blood cells, fibrin deposition was evident around many vessels. Soluble EphB4 was found to have no such effects on the endothelium in the normal tissues examined (lungs, liver and kidneys).

H. Materials and Methods 1 ) Expression constructs

To construct expression vectors for producing soluble, 6xHis-tagged EphB4-ECD variants, cloned full-length human EphB4 cDNA was amplified by PCR using the following oligo primers: TACTAGTCCGCCATGGAGCTCCGGGTGCTGCT (common EphB4 N- terminal primer) and GCGGCCGCTTAATGGTGATGGTGA TGATGAGCCGAAGGA GGGGTGGTGCA (B4-GC), AGCGGCCGCTTAATGGTGATGGTGAT GATGGACATTGA CAGGCTCAAATGGGA (B4-GCF1) or TGCGGCCGCTTAATGGTGATGGTGATGAT

GCTGCTCCCGCCAGCCCTCGCTCTCAT (B4-GCF2). The resulting PCR fragments were TA-cloned into mammalian expression vector pEF6/V5-His-TOPO (Invitrogen) under EF-lα promoter control. The expressed recombinant proteins encode the following fragments ofthe mature extracellular part of human EphB4: amino acid positions 1-522 (GCF2), 1-412 (GCF1) and 1-312 (GC). To generate the B4-CF2 deletion (δ amino acids 13-183) PCR fragment for pEF6 cloning, EphB4 cDNA was amplified by two-step overlap PCR using oligo primers TACTAGTCCGCCATGGAGCTCCGGGTGCTGCT, CAGCTGAGTTTCCAATTTTGTGTTC,

GAACACAAAATTGGAAACTCAGCTGACTGTGAACCTGAC and GCGGCCGCCCTG CTCCCGCCAGCCCTCGCT.

Vector for producing secreted human EplιrinB2-alkaline phosphatase (B2-AP) reagent was constructed by PCR amplification of human Ephrin B2 cDNA using primers TAAAGCTTCCGCCATGGCTGTGAGAAGGGAC and TAGGATCCTTCGGAACCG AGGATGTTGTTCCC and cloning the resulting fragment, digested with Hind III and Bam HI, into Hind III-Bgl II digested pAPTag2 vector (GenHunter, Inc.). In each case, inserts in expression vectors were verified by complete sequencing.

2) Antibodies and other reagents

Anti-Eph B4 monoclonal antibodies mAB79 and mAB23 were raised in mice against the GCF2 protein containing amino acids 1-522 of mature human EphB4 and purified from hybridoma supernatants by Protein A chromatography. The anti-phosphotyrosine antibody 4G10 was from UBI (Lake Placid, NY). Protein G-HRP conjugate was purchased from Bio- Rad.

3) Expression and purification of EphB4-derived recombinant proteins To produce the EphB4-ECD soluble proteins, cultured human embryonic kidney cells

HEK293T were transfected with the conesponding plasmid constructs using standard calcium phosphate or Lipofectamin 2000 reagent (Invitrogen) protocols. Twelve to sixteen hours post-transfection, the growth medium (DMEM+10%> fetal bovine serum) was aspirated, cells washed once with serum free DMEM and replaced with serum free DMEM. Conditioned media containing the secreted proteins were harvested 72-96 hours later, clarified by centrifugation and used for purification of His-tagged proteins using Ni-NTA Agarose (Qiagen). The purity and quantity ofthe recombinant proteins was tested by SDS- PAAG elecfrophoresis with Coomassie Blue or silver staining, Western blotting and UV spectroscopy. Purified proteins were dialyzed against 20 mM Tris-HCl, 0.15 M NaCl, pH 8 and stored at -70 °C.

To test ligand binding properties ofthe proteins, 10 μl of Ni-NTA-Agarose (Qiagen) were incubated in microcentrifuge tubes with 10-500 ng sample of a B4-ECD protein diluted in 0.5 ml of binding buffer BB (20 mM Tris-HCl, 0.15 M NaCl, 0.1% bovine serum albumin, pH 8). After incubation for 30 min on shaking platform, Ni-NTA beads were washed twice with 1.4 ml of BB, followed by addition of B2-AP fusion protein at concentration of 50 nM. Binding was performed for 30 min on a shaking platform. Tubes were centrifuged and washed once with 1.4 ml of BB. Amount of precipitated AP was measured colorimetrically at 420 nm after application of p-nitrophenyl phosphate (PNPP) and incubation for 5-30 min.

4) Immunoprecipitation

All lysates were processed at 4 °C. Cells were lysed in 1 ml of buffer containing 20 mM Hepes at pH 7.4, 100 mM sodium chloride, 50 mM sodium fluoride, 2 mM EDTA, 2 mM EGTA, 1 mM sodium orthovanadate, l%(v/v) NP-40, 0.5% (w/v) sodium deoxycholate, 1 mM phenyl methylsulphonyl fluoride (added freshly) and 100U Trasylol. Lysates were scraped into Epperidorf tubes and 50 μl of boiled, formalin-fixed Staphylococcus aureus was added (Calbiochem, San Diego). After 30 min of mixing, the lysates were centrifuged for 5 min at 25,000g in a minifuge and the supematants transfened to new tubes containing the appropriate antibody. Lysates were mixed with antibodies for 1 h, after which time 50 μl of protein A-Sepharose beads were added and the contents ofthe tubes mixed for 1 h to collect the immunoprecipitates. Protein A beads were collected by centrifugation at 25,000g for 30 s. The supematants were discarded and the beads washed tliree times with 1 ml lysis buffer minus deoxycholate.

5) Cell-based EphB4 tyrosine kinase assay

The human prostate carcinoma cell line PC3 cells were maintained in RPMI medium with 10%) dialyzed fetal calf serum and 1% penicillin/streptomycin/neomycin antibiotics mix. Cells were maintained at 37 °C in a humidified atmosphere of 5% CO₂/95%) air. Typically, cells were grown in 60 mm dishes until confluency and were either treated with mouse Eplirin B2-Fc fusion at 1 μg/ml in RPMI for 10 min to activate EphB4 receptor or plain medium as a control. To study the effect of different derivatives of soluble EphB4 ECD proteins on EphB4 receptor activation, three sets of cells were used. In the first set, cells were treated with various proteins (5 proteins; GC, GCF1, GCF2, GCF2-F, CF2) at 5 μg/ml for 20 min. hi the second set of cells, prior to application, proteins were premixed with ephrinB2-Fc at 1 :5 (EphB4 protein: B2-Fc) molar ratio, incubated for 20 min and applied on cells for 10 min. In the third set of cells, cells were first treated with the proteins for 20 min at 5 μg/ml, media was replaced with fresh media containing 1 μg/ml of EphrinB2-Fc and incubated for another 10 min.

After the stimulation, cells were immediately harvested with protein extraction buffer containing 20 mM Tris-HCl, pH 7.4, 150 mM NaCl, 1% (v/v) Triton X100, 1 mM EDTA, 1 mM PMSF, 1 mM Sodium vanadate. Protein extracts were clarified by centrifugation at 14,000 rpm for 20 min at 4 °C. Clarified protein samples were incubated overnight with protein A/G coupled agarose beads pre-coated with anti-EphB4 monoclonal antibodies. The JP complexes were washed twice with the same extraction buffer containing 0.1% Triton XI 00. The immunoprecipitated proteins were solubilized in IX SDS-PAGE sample loading buffer and separated on 10% SDS-PAGE. For EphB4 receptor activation studies, electroblotted membrane was probed with anti-pTyr specific antibody 4G10 at 1 : 1000 dilution followed by Protein G-HRP conjugate at 1 :5000 dilutions.

6) Cell Culture

Normal HUVECs were obtained from Cambrex (BioWhittaker) and maintained in EBM2 medium supplemented with 0.1 mg/ml endothelial growth supplement (crude extract from bovine brain), penicillin (50 U/ml), streptomycin (50 U/ml), 2 mmol/1 glutamine and 0.1 mg/ml sodium heparin. Aliquots of cells were preserved frozen between passages 1 and 3. For all experiments, HUVECs were used at passages 4 or below and collected from a confluent dish. 7) Endothelial Cell Tube Formation Assay

Matrigel (60 μl of lOmg/ml; Collaborative Lab, Cat. No. 35423) was placed in each well of an ice-cold 96-well plate. The plate was allowed to sit at room temperature for 15 minutes then incubated at 37 °C for 30 minutes to permit Matrigel to polymerize. In the mean time, human umbilical vein endothelial cells were prepared in EGM-2 (Clonetic, Cat. No. CC3162) at a concentration of 2x10⁵ cells/ml. The test protein was prepared at 2x the desired concentration (5 concentration levels) in the same medium. Cells (500 μl) and 2x protein (500 μl) were mixed and 200 μl of this suspension were placed in duplicate on the polymerized Matrigel. After 24 h incubation, triplicate pictures were taken for each concentration using a Bioquant Image Analysis system. Protein addition effect (IC₅₀) was assessed compared to untreated confrols by measuring the length of cords fomied and number ofjunctions.

8) Cell Migration Assay

Chemotaxis of HUVECs to VEGF was assessed using a modified Boyden chamber, franswell membrane filter inserts in 24 well plates, 6.5 mm diam, 8 μm pore size, 10 μm thick matrigel coated, polycarbonate membranes (BD Biosciences). The cell suspensions of HUVECs (2x 10⁵ cells/ml) in 200 μl of EBM were seeded in the upper chamber and the soluble EphB4 protein were added simultaneously with stimulant (VEGF or bFGF) to the lower compartment ofthe chamber and their migration across a polycarbonate filter in response to 10- 20 ng/ml of VEGF with or without 100 nM-1 μM test compound was investigated. After incubation for 4-24 h at 37 °C, the upper surface ofthe filter was scraped with swab and filters were fixed and stained with Diff Quick. Ten random fields at 200x mag were counted and the results expressed as mean # per field. Negative unstimulated control values were subtracted from stimulated control and protein freated sample values and the data was plotted as mean migrated cell ± S.D. IC₅₀ was calculated from the plotted data.

9) Growth Inhibition Assay

HUVEC (1.5xl0³ cells) were plated in a 96-well plate in 100 μl of EBM-2 (Clonetic, Cat. No. CC3162). After 24 hours (day 0), the test recombinant protein (100 μl) is added to each well at 2x the desired concentration (5-7 concentration levels) in EBM-2 medium. On day 0, one plate was stained with 0.5% crystal violet in 20%> methanol for 10 minutes, rinsed with water, and air-dried. The remaining plates were incubated for 72 h at 37 °C. After 72 h, plates were stained with 0.5% crystal violet in 20% methanol, rinsed with water and air-dried. The stain was eluted with 1:1 solution of ethanol: 0.1M sodium citrate (including day 0 plate), and absorbance measured at 540 nm with an ELISA reader (Dynatech Laboratories). Day 0 absorbance was subtracted from the 72 h plates and data is plotted as percentage of control proliferation (vehicle treated cells). IC₅₀ value was calculated from the plotted data.

10) Murine Matrigel Plug Angiogenesis Assay In vivo angiogenesis was assayed in mice as growth of blood vessels from subcutaneous tissue into a Matrigel plug containing the test sample. Matrigel rapidly forms a solid gel at body temperature, trapping the factors to allow slow release and prolonged exposure to suπounding tissues. Matrigel (8.13 mg/ml, 0.5 ml) in liquid fonn at 4 °C was mixed with Endothelial Cell Growth Supplement (ECGS), test proteins plus ECGS or Matrigel plus vehicle alone (PBS containing 0.25% BSA). Matrigel (0.5ml) was injected into the abdominal subcutaneous tissue of female nu/nu mice (6 wks old) along the peritoneal mid line. There were 3 mice in each group. The animals were cared for in accordance with institutional and NIH guidelines. At day 6, mice were sacrificed and plugs were recovered and processed for histology. Typically the overlying skin was removed, and gels were cut out by retaining the peritoneal lining for support, fixed in 10%o buffered formalin in PBS and embedded in paraffin. Sections of 3 μm were cut and stained with H&E or Masson's trichrome stain and examined under light microscope

11) Mouse Corneal Micropocket assay

Mouse corneal micropocket assay was performed according to that detailed by Kenyon et al., 1996. Briefly, hydron pellets (polyhydroxyethylmethacrylate [polyHEMA], hiterferon Sciences, New Brunswick, NJ, U.S.A.) containing either 90 ng of bFGF (R&D) or 180 ng of VEGF (R&D Systems, Minneapolis, MN, U.S.A.) and 40 μg of sucrose aluminium sulfate (Sigma) were prepared. Using an operating microscope, a stromal linear keratotomy was made with a surgical blade (Bard-Parker no. 15) parallel to the insertion ofthe lateral rectus muscle in an anesthetized animal. An infrastromal micropocket was dissected using a modified von Graefe knife (2^"30 mm). A single pellet was implanted and advanced toward the temporal corneal limbus (within 0±7±1±0 mm for bFGF pellets and 0±5 mm for VEGF pellets). The difference in pellet location for each growth factor was determined to be necessary given the relatively weaker angiogenic stimulation of VEGF in this model. Antibiotic ointment (erythromycin.) was then applied to the operated eye to prevent infection and to decrease surface iπegularities. The subsequent vascular response was measured extending from the limbal vasculature toward the pellet and the contiguous circumferential zone of neovascularization Data and clinical photos presented here were obtained on day 6 after pellet implantation, which was found to be the day of maximal angiogenic response.

12) In vitro invasion assay

"Matrigel" matrix-coated 9-mm cell culture inserts (pore size, 8 μm; Becton Dickinson, Franklin Lakes, NJ) were set in a 24-well plate. The HUVEC cells were seeded at a density of 5x10³ cells per well into the upper layer ofthe culture insert and cultured with serum-free EBM in the presence of EphB4 ECD for 24 h. The control group was cultured in the same media without EphB4. Then 0.5 ml ofthe human SCC15 cell line, conditioned medium was filled into the lower layer ofthe culture insert as a chemo-attractant. The cells were incubated for 24 h, then the remaining cells in the upper layer were swabbed with cotton and penetrating cells in the lower layer were fixed with 5% glutaraldehyde and stained with Diff Quick. The total number of cells passing through the Matrigel matrix and each 8 μm pore ofthe culture insert wascounted using optical microscopy and designated as an invasion index (cell number/area). 13) SCC 15 tumor growth in mice

Subcutaneously inject logarithmically growing SCC15, head and neck squamous cell carcinoma cell line, at 5X10⁶ cell density; with or without EphB4 ECD in the presence or absence of human bFGF, into athymic Balb/c nude mice, along with Matrigel (BD Bioscience) synthetic basement membrane (1 :1 v/v), and examine tumors within 2 weeks. Tumor volumes in the EphB4 ECD group, in the presence and absence of growth factor after implantation were three-fold smaller than those in the vehicle groups. There was no difference in body weight between the groups. Immunohistochemical examination of cross- sections of resected tumors and TUNEL-positive apoptosis or necrosis, CD34 immunostaining, and BrdU proliferation rate will be performed, after deparaffinized, rehydrated, and quenched for endogenous peroxidase activity, and after 10 min permeabilization with proteinase K. Quantitative assessment of vascular densities will also be performed. Local intratumoral delivery or IV delivery of EphB4 ECD will also be performed twice a week.

30 athymic nude mice, BALB/c (nu/nu), were each injected with 1 x 10⁶ B16 melanoma cells with 0.1 ml PBS mixed with 0.1 ml matrigel or 1.5 x 10⁶ SCC 15 cells resuspended in 200 μl of DMEM serum-free medium and injected subcutaneously on day 0 on the right shoulder region of mice. Proteins were injected intravenously or subcutaneously, around the tumor beginning on day 1 at a loading dose of 4 μg/mg, with weekly injections of 2ug/mg. (10 μg/g, 50 μg/kg/day), and at 2 weeks post-inoculation. Mice are sacrificed on Day 14. Control mice received PBS 50 μl each day.

14) Tumor formation in nude mice All animals were treated under protocols approved by the institutional animal care committees. Cancer cells (5xl0⁶) were subcutaneously inoculated into the dorsal skin of nude mice. When the tumor had grown to a size of about 100 mm (usually it took 12 days), sEphB4 was either infraperitoneally or subcutaneously injected once/day, and tumorigenesis was monitored for 2 weeks. Tumor volume was calculated according to the formula a²xb, where a and b are the smallest and largest diameters, respectively. A Student's t test was used to compare tumor volumes, with P<.05 being considered significant.

15) Quantification of microvessel density

Tumors were fixed in 4% formaldehyde, embedded in paraffin, sectioned by 5 μm, and stained with hematoxylineosin. Vessel density was semi-quantitated using a computer- based image analyzer (five fields per section from three mice in each group).

Example 3. EphB4 Is Upregulated and Imparts Growth Advantage in Prostate Cancer

A. Expression of EphB4 in prostate cancer cell lines

We first examined the expression of EphB4 protein in a variety of prostate cancer cell lines by Western blot. We found that prostate cancer cell lines show marked variation in the abundance ofthe 120 kD EphB4. The levels were relatively high in PC3 and even higher in PC3M, a metastatic clone of PC3, while normal prostate gland derived cell lines (MLC) showed low or no expression of EphB4 (Fig. 27 A). We next checked the activation status of EphB4 in PC3 cells by phosphorylation study. We found that even under normal culture conditions, EphB4 is phosphorylated though it can be further induced by its ligand, ephrin B2 (Fig. 27B).

B. Expression of EphB4 in clinical prostate cancer samples

To determine whether EphB4 is expressed in clinical prostate samples, tumor tissues and adjacent normal tissue from prostate cancer surgical specimens were examined. The histological distribution of EphB4 in the prostate specimens was determined by iinmunohistochemistry. Clearly, EphB4 expression is confined to the neoplastic epithelium (Fig. 28, top left), and is absent in stromal and normal prostate epithelium (Fig. 28, top right), prostate tissue anay, 24 ofthe 32 prostate cancers examined were positive. We found EphB4 mRNA is expressed both in the normal and tumor tissues of clinical samples by quantitative RT-PCR. However, tumor EphB4 mRNA levels were at least 3 times higher than in the normal in this case (Fig. 28, lower right).

C. p53 and PTEN inliibited the expression of EphB4 in PC3 cells

PC3 cells are known to lack PTEN expression (Davis, et al., 1994, Science. 266:816- 819) and wild-type p53 function (Gale, et al., 1997, Cell Tissue Res. 290:227-241). We investigated whether the relatively high expression of EphB4 is related to p53 and/or PTEN by re-introducing wild-type p53 and/or PTEN into PC3 cells. To compensate for the transfection efficiency and the dilution effect, transfected cells were sorted for the cofransfected truncated CD4 marker. We found that the expression of EphB4 in PC3 cells was reduced by the re-introduction of either wild-type p53 or PTEN. The co-transfection of p53 and PTEN did not further inhibit the expression of EphB4 (Fig. 29 A). D. Retinoid X receptor (RXR α ) regulates the expression of EphB4

We previously found that RXRα was down-regulated in prostate cancer cell lines (Zhong, et al, 2003, Cancer Biol Ther. 2:179-184) and here we found EphB4 expression has the reverse expression pattern when we looked at "normal" prostate (MLC), prostate cancer (PC3), and metastatic prostate cancer (PC3M) (Fig. 27A), we considered whether RXRα regulates the expression of EphB4. To confirm the relationship, the expression of EphB4 was compared between CWR22R and CWR22R-RXRα, which constitutively expresses RXRα. We found a modest decrease in EphB4 expression in the RXRα overexpressing cell line, while FGF8 has no effect on EphB4 expression. Consistent with initial results, EphB4 was not found in "normal" benign prostate hyperfrophic cell line BPH-1 (Fig. 29B).

E. Growth factor signaling pathway of EGFR and IGF-IR regulates EphB4 expression

EGFR and IGF-IR have both been shown to have autocrine and paracrine action on PC3 cell growth. Because we found that EplιB4 expression is higher in the more aggressive cell lines, we postulated that EphB4 expression might conelate with these pro-survival growth factors. We tested the relationship by independently blocking EGFR and IGF-IR signaling. EphB4 was down-regulated after blocking the EGFR signaling using EGFR kinase inhibitor AG 1478 (Fig. 30A) or upon blockade ofthe IGF-IR signaling pathway using IGF- 1R neutralizing antibody (Fig. 30B).

F. EphB4 siRNA and antisense ODNs inhibit PC3 cell viability

To define the significance of this EphB4 overexpression in our prostate cancer model, we concentrated our study on PC3 cells, which have a relatively high expression of EphB4. The two approaches to decreasing EphB4 expression were siRNA and AS-ODNs. A number of different phosphorothioate-modifϊed AS-ODNs complementary to different segments of the EphB4 coding region were tested for specificity and efficacy of EphB4 inhibition. Using 293 cells transiently transfected with full-length EphB4 expression vector AS-10 was found to be the most effective (Fig. 3 IB). A Similar approach was applied to the selection of specific siRNA. EphB4 siRNA 472 effectively knocks down EphB4 protein expression (Fig. 31 A). Both siRNA 472 and antisense AS-10 ODN reduced the viability of PC3 cells in a dose dependent manner (Fig. 31C, D). Unrelated siRNA or sense oligonucleotide had no effect on viability.

G. EphB4 siRNA and antisense ODNs inhibit the mobility of PC3 Cells

PC3 cells can grow aggressively locally and can form lymph node metastases when injected orthotopically into mice, hi an effort to study the role of EphB4 on migration of PC3 cells in vitro, we performed a wound-healing assay. When a wound was introduced into a monolayer of PC3 cells, over the course ofthe next 20 hours cells progressively migrated into the cleared area. However, when cells were transfected with siRNA 472 and the wound was introduced, this migration was significantly inhibited (Fig. 3 IE). Pretreatment of PC3 cells with 10 μM EphB4 AS-10 for 12 hours generated the same effect (Fig. 3 IF), hi addition, knock-down of EphB4 expression in PC3 cells with siRNA 472 severely reduced the ability of these cells to invade Matrigel as assessed by a double-chamber invasion assay (Fig. 31G), compared to the control siRNA.

H. EphB4 siRNA induces cell cycle anest and apoptosis in PC3 cells

Since knock-down of EphB4 resulted in decreased cell viability (Fig. 31C) we sought to determine whether this was due to effects on the cell cycle. In comparison to control siRNA transfected cells, siRNA 472 resulted in an accumulation of cells in the sub GO and S phase fractions compared to cells treated with control siRNA. The sub GO fraction increased from 1 % to 7.9%, and the S phase fraction from 14.9 % to 20.8 % in siRNA 472 freated cells compared to control siRNA treated cells (Fig. 32A). Cell cycle arrest at sub GO and G2 is indicative of apoptosis. Apoptosis as a result of EphB4 knock-down was confirmed by ELISA assay. A dose-dependent increase in apoptosis was observed when PC3 cells were transfected with siRNA 472, but not with control siRNA (Fig. 32B). At 100 nM there was 15 times more apoptosis in siRNA 472 transfected than control siRNA transfected PC3 cells.

I. Materials and Methods 1) Reagents

Neutralizing IGF-IR antibody was from R&D Systems (Minneapolis MN). Anti-IGF- lR(β), -EGFR, -EphB4(C-16) were from Santa Cruz Biotech (Santa Cruz, CA). β-actin monoclonal antibody was purchased from Sigma Chemical Co. (St Louis, MO). Media and fetal bovine seram (FBS) were from Invitrogen (Carlsbad, CA). AG 1478(4-(3'- ChloiOanilino)-6,7-dimethoxy-quinazoline) was from Calbiochem (San Diego, CA).

2) Antisense oligodeoxynucleotides and EphB4 siRNAs

EphB4 specific antisense phosphorothioate-modified oligodeoxynucleotide (ODN) and sense ODN were synthesized and purified by Qiagen (Alameda CA). The sequences are: Sense, 5'-TCC-TGC-AAG-GAG-ACC-TTC-AC-3'; AS1: 5'-GTG-CAG-GGA-TAG-CAG~ GGC-CAT-3'; AS10: 5'-ATG-GAG-GCC-TCG-CTC-AGA-AA-3'. siRNAs were synthesized at the USC/Norris Comprehensive Cancer Center Microchemical Core laboratory. Sequences of EphB4 siRNAs are siRNA 472 5'-GGU-GAA-UGU-CAA-GAC- GCU-GUU-3' and siRNA 2303 5'-cuc-uuc-cga-ucc-cac-cua-cuu-3'. Negative control siRNA to scrambled GAPDH was from Ambion (Austin, TX) 3) Cell lines and culture The prostate cancer cell lines, PC3, PC3M, DU145, ALVA31, LAPC-4, LNCaP, CWR22R and adult human normal prostate epithelial cell line MLC SV40, and BPH-1 were obtained and cultured as described previously (7). Stable cell line CWR22R-RXR, LNCaP- FGF8 were established and cultured as described before (7, 33). 4) Generation of EphB4 monoclonal antibody

The extracellular domain (ECD) of EphB4 was cloned into pGEX-4T-l to generate GST-fused ECD (GST-ECD). EphB4ECD expressed as a GST fusion protein in BL21 E. coli was purified by affinity chromatography and the GST domain was cleaved by thrombin. Monoclonal antibody was generated and the sensitivity and specificity ofthe antibody was reconfirmed by Western blot with whole cell lysate of 293 cells stably transfected with EphB4.

5) One-Step RT-PCR and Quantitative RT-PCR

Total RNA was extracted using RNA STAT-60 (Tel-Test, hie. Friendswood TX) from prostate cancer specimens and adjacent nonxial specimens. For quantitative RT-PCR first sfrand cDNA was synthesized from 5 μg of total RNA using Superscript III (Invitrogen, Carlsbad CA). Quantitative RT-PCR was performed on the Stratagene MX3000P system (Stratagene, La Jolla CA) using SYBR Green I Brilliant Mastermix (Stragene) according to the manufacture's instructions. Optimized reactions for EphB4 and β-actin (used as the normalizer gene) were 150 nM each ofthe forward primer (β-actin, 5'-GGA-CCT-GAC- TGA-CTA-CCT-A-3⁵; EphB4, 5⁵-AAG-GAG-ACC-TTC-ACC-GTC-TT-3⁵) and reverse primer (β-actin 5⁵-TTG-AAG-GTA-GTT-TCG-TGG-AT-3'; EphB4, 5'-TCG-AGT-CAG- GTT-CAC-AGT-CA-3') with DNA denaturation/activation of polymerase at 95 °C for 10 min followed by 40 cycles of 95 °C for 30s, 60 °C for lmin, 72 °C for lmin. The specificity ofthe gene-specific amplification was confirmed by the presence of a single dissociation peak. All reactions were performed in triplicate with RT and no template negative controls.

6) Immunohistochemistry

OCT-embedded tissues were sectioned at 5 μm and fixed in phosphate-buffered 4% parafomialdehyde. Sections were washed for 3 x 5 min in PBS and endogenous peroxidase was blocked by incubation in 0.3% H₂O₂ in PBS for 10 min at room temperature. Sections were incubated with Eph4 (C-l 6) antibody (1 :50) for 1 h at room temperature followed by three washes in PBS and incubation with donkey anti-goat secondary antibody (Santa Cruz Biotech.) for 1 h at room temperature. After three washes in PBS, peroxidase activity was localized by incubation in DAB substrate solution (Vector Laboratories, hie. Burlingame CA) for 10 min at room temperature. Sections were counterstained with Hematoxylin for 20 s, dehydrated and mounted. Negative control for staining was substitution of normal goat serum for primary antibody. Immunohistochemical staining on prostate aπay (BioMeda, Foster City, CA) was done using goat ABC Staining System (Santa Cruz Biotech.) according to the manufacturer's instructions.

7) Western blot

Whole cell lysates were prepared using Cell Lysis Buffer (GeneHunter, Basgvukke TN) supplemented with protease inhibitor cocktail (Pierce, Rockford IL), unless otherwise noted. Total protein was deteπnined using the DC reagent system (Bio-Rad, Hercules CA). Typically, 20 μg whole cell lysate was run on 4-20% Tris-Glycine gradient gel. The samples were electro-transfeπed to PVDF membrane and the non-specific binding was blocked in TBST buffer (0.5 mM Tris-HCl, 45 mM NaCl, 0.05% Tween-20, pH 7.4) containing 5% nonfat milk. Membranes were first probed with primary antibody overnight, stripped with Restore™ Western Blot stripping buffer (Pierce, Rockford IL) and reprobed with β-actin to confirm equivalent loading and transfer of protein. Signal was detected using SuperSignal West Femto Maximum Sensitivity Substrate (Pierce).

8) Phosphorylation analysis

Cells growing in 60 mm dishes were either serum starved (1% FBS supplemented RPMI 1640, 24 hours) or cultured in normal conditions (10% FBS) and then treated with or without 1 μg/ml mouse ephrin B2/F_c for 10 min to activate EphB4 receptor Cleared cell lysates were incubated with EphB4 monoclonal antibody overnight at 4°C. Antigen-antibody complex was immunoprecipitated by the addition of 100 μl of Protein G-Sepharose in 20 mM sodium phosphate, pH 7.0 with incubation overnight at 4 °C. Immunoprecipitates were analyzed by Western blot with pTyr specific antibody (Upstate, clone 4G10) at 1 : 1000 dilution followed by incubation with protein G-HRP (Bio-Rad) at 1:5000 dilution. To monitor immunoprecipitation efficiency, a duplicate membrane was probed with EphB4 specific monoclonal antibody.

9) Transient transfection and sorting of transfected cells PC3 cells were cotransfected with pMACS 4.1 coding for CD4 and wild type p53

(pC53-SN3) or PTEN vector or both using Lipofectamine 2000 (Invitrogen) according to the manufacturer's instructions. The molar ratio of CD4 to p53 or PTEN or vector was 1 :3 and total plasmid was 24 μg for a 10 cm² dish of 90% confluent cells using 60 μl of Lipofectamine 2000. 24 hours after transfection, a single cell suspension was made and sorted using truncated CD4 as a surface marker according to the manufacturer's protocol (Miltenyi Biotec, Germany). Sorted cells were lysed in 1 x SDS sampling buffer and analyzed by Western blot.

10) Study of IGF and EGF signaling pathway on the expression of EphB4

PC3 cells were seeded into 6-well plates and cultured until 80%> confluent and treated with 2 μg/ml neutralizing IGF-IR monoclonal antibody, MAB391 (Hailey, et al, 2002, Mol Cancer Ther. 1:1349-1353), or with 1 nM AG 1478, a strong EGFR inhibitor (Liu, et al, 1999, J Cell Sci. 112 (Pt 14):2409-2417) for 24 h. Crude cell lysates were analyzed by

Western blot. Band density was quantified with the Bio-Rad QuantityOne System software.

11) Cell viability assay

PC3 cells were seeded on 48-well plates at a density of approximately l lO⁴ cells/well in a total volume of 200 ml. Media was changed after the cells were attached and the cells were treated with various concentrations (1-10 μM) of EplιB4 antisense ODN or sense ODN as control. After three days media was changed and fresh ODNs added. Following a further 48 h incubation, cell viability was assessed by MTT as described previously (36). EphB4 siRNAs (10-100 nM) were introduced into 2 x 10⁴PC3 cells/well of a 48-well plate using 2 μl of Lipofectamine™ 2000 according to the manufacturer's instructions. 4 h post-transfection the cells were returned to growth media (RPMI 1640 supplemented with 10 % FBS). Viability was assayed by MTT 48 h following transfection.

12) Wound healing migration assay

PC3 cells were seeded into 6-well plates and cultured until confluent. 10 μM AS-10 or sense ODN as control were introduced to the wells as described for the viability assay 12 hours before wounding the monolayer by scraping it with a sterile pipette tip. Medium was changed to RPMI 1640 supplemented with 5% FBS and fresh ODNs. Confluent cultures transfected with 50 nM siRNA 472 or GAPDH negative control siRNA 12 hours prior to wounding were also examined. The healing process was examined dynamically and recorded with a Nikon Coolpix 5000 digital camera with microscope adapter. 13) Invasion assay PC3 cells were transfected with siRNA 472 or control siRNA using Lipofectamine™ 2000 and 6 hours later 0.5 x 105 cells were transfened into 8 μm Matrigel-precoated inserts (BD Bioscience, Palo Alto, CA). The inserts were placed in companion wells containing RPMI supplemented with 5 % FBS and 5 μg/ml fibronectin as a chemoattractant. Following 22 h incubation the inserts were removed and the noninvading cells on the upper surface were removed by with a cotton swab. The cells on the lower surface ofthe membrane were fixed in 100%) methanol for 15 min, air dried and stained with Giemsa stain for 2 min. The cells were counted in five individual high-powered fields for each membrane under a light microscope. Assays were performed in triplicate for each treatment group. 14) Cell cycle analysis

80% confluent cultures of PC3 cells in 6-well plates were transfected with siRNA472 (100 nM) using Lipofectamine™ 2000. 24 hours after transfection, cells were trypsinized, washed in PBS and incubated for 1 h at 4oC in 1 ml of hypotonic solution containing 50 μg/ml propidium iodide, 0.1% sodium citrate, 0.1 Triton X-100 and 20 μg/ml Dnase-free RnaseA. Cells were analyzed in linear mode at the USC Flow cytometry facility. Results were expressed as percentages of elements detected in the different phases ofthe cell cycle, namely Sub GO peak (apoptosis), G0/G1 (no DNA synthesis), S (active DNA systhesis), G2 (premitosis) and M (mitosis).

15) Apoptosis ELISA Apoptosis was studied using the Cell Death Detection ELISAplus Kit (Roche,

Piscataway, NJ) according to the manufacturer's instructions. Briefly, PC3 80% confluent cultures in 24-well plates were transfected using Lipofectamine™ 2000 with various concentrations (0-100 nM) of siRNA 472 or 100 nM confrol siRNA. 16 hours later, cells were detached and 1 x 10⁴ cells were incubated in 200 μl lysis buffer. Nuclei were pelleted by centrifugation and 20 μl of supernatant containing the mono- or ohgonucleosomes was taken for ELISA analysis. Briefly, the supernatant was incubated with anti-histone-biotin and anti- DNA-POD in streptavidin-coated 96-well plate for 2 hours at room temperature. The color was developed with ABST and absorbance at 405 nm was read in a microplate reader (Molecular Devices, Sunnyvale, CA).

Example 4. Expression of EPHB4 in Mesothelioma: a candidate target for therapy Malignant mesothelioma (MM) is a rare neoplasm that most often arises from the pleural and peritoneal cavity serous surface. The pleural cavity is by far the most frequent site affected (> 90%), followed by the peritoneum (6-10%) (Carbone et al., 2002, Semin Oncol. 29:2-17). There is a strong association with asbestos exposure, about 80% of malignant mesothelioma cases occur in individuals who have ingested or inhaled asbestos. This tumor is particularly resistant to the cuπent therapies and, up to now, the prognosis of these patients is dramatically poor (Lee et al, 2000, Cuπ Opin Pulm Med. 6:267-74).

Several clinical problems regarding the diagnosis and treatment of malignant mesothelioma remain unsolved. Making a diagnosis of mesothelioma from pleural or abdominal fluid is notoriously difficult and often requires a thoracoscopic or laproscopic or open biopsy and Immunohistochemical staining for certain markers such as meosthelin expressed preferentially in this tumor. Until now, no intervention has proven to be curative, despite aggressive chemotherapeutic regimens and prolonged radiotherapy. The median survival in most cases is only 12-18 months after diagnosis. In order to identify new diagnostic markers and targets to be used for novel diagnostic and therapeutic approaches, we assessed the expression of EPHB4 and its ligand EphrinB2 in mesothelioma cell lines and clinical samples.

A. EPHB4 and EphrinB2 is expressed in mesothelioma cell lines

The expression of Ephrin B2 and EphB4 in malignant mesothelioma cell lines was detenxiined at the RNA and protein level by a variety of methods. RT-PCR showed that all of the four cell lines express EphrinB2 and EPHB4 (fig. 33 A). Protein expression was determined by Western blot in these cell lines. Specific bands for EphB4 were seen at 120 kD. In addition, Ephrin B2 was detected in all cell lines tested as a 37 kD band on Western blot (fig. 33B). No specific band for Ephrin B2 was observed in 293 human embryonic kidney cells, which were included as a negative control.

To confirm the presence of EphB4 transcription in mesothelioma cells, in situ hybridization was caπied out on NCI H28 cell lines cultured on chamber slides. Specific signal for EphB4 was detected using antisense probe Ephrin B2 transcripts were also detected in the same cell line. Sense probes for both EphB4 and Ephrin B2 served as negative controls and did not hybridize to the cells (figure 34). Expression of EphB4 and Ephrin B2 proteins was confirmed in the cell lines by immunofluorescence analysis (fig. 35). Tliree cell lines showed strong expression of Epl B4, whereas expression of Ephrin B2 was present in H28 and H2052, and weakly detectable in H2373.

B. Evidence of Expression of EPHB4 and EphrinB2 in clinical samples

Tumor cells cultured from the pleural effusion of a patient diagnosed with pleural malignant mesothelioma were isolated and showed positive staining for both EphB4 and Ephrin B2 at passage 1 (figure 35, bottom row). These results confirm co-expression of EphB4 and Ephrin B2 in mesothelioma cell lines. To determine whether these results seen in tumor cell lines were a real reflection of expression in the disease state, tumor biopsy samples were subjected to immunohistochemical staining for EphB4 and Ephrin B2. Antibodies to both proteins revealed positive stain in the tumor cells. Representative data is shown in figure 36.

C. EPHB4 is involved in the cell growth and migration of mesothelioma

The role of EphB4 in cell proliferation was tested using EPHB4 specific antisepses oligonucleotides and siRNA. The freatment of cultured H28 with EPHB4 antisense reduced cell viability. One ofthe most active inhibitor of EphB4 expression is EPHB4AS-10 (fig. 37A). Transfection of EPHB4 siRNA 472 generated the same effect (fig. 37B).

MM is a locally advancing disease with frequent extension and growth into adjacent vital stractures such as the chest wall, heart, and esophagus. In an effort to study this process in vitro, we perform wound healing assay using previously described techniques (3:36). When a wound was introduced into sub confluent H28 cells, over the course ofthe next 28 hours cells would progressively migrate into the area ofthe wound. However, when cells were pretreated with EPHB4AS-10 for 24 hours, and the wound was introduced, this migration was virtually completely prevented (fig. 38 A). The migration study with Boyden Chamber assay with EPHB4 siRNA showed that cell migration was greatly inhibited with the inhibition of EPHB4 expression (Fig. 38B).

D. Materials and Methods

1) Cell lines and reagents

NCI H28, NCI H2052, NCI H2373, MSTO 21 IH mesothelioma cell lines and 293 human embryonic kidney cells were obtained from the ATCC (Manassas, VA). Cells were maintained in RPMI 1640 media supplemented with 10 %> heat-inactivated fetal bovine seram (FBS; Life Technologies, Gaithersburg, MD) and antibiotics. Primary cells were obtained from pleural effusion of patients with mesothelioma. A large number of EPHB4 phosphorothioate modified antisense oligonucleotides were synthesized. Similarly a number of EphB4 specific siRNAs were generated. Monoclonal antibody produced against EPHB4 was used for western blot. Polyclonal antibody against EphrinB2 and EPHB4 (C-l 6) (for immunohistochemical staining) was from Santa Cruz.

2) RT-PCR

Total RNA was reversed transcribed by use of random hexamers (Invitrogen). Primers for EphB4 and EphrinB2 were designed with Primer 3 software. The sequences for all primers are as follows: EPHB4 forward primer and EPHB4 reverse primer (see, e.g., in Example 2); EphrinB2 forward primer and EphrinB2 reverse primer (see, e.g., in Example 6); G3PDH forward primer, 5'-GGAGCCAAAAGGGTCATCAT-3'; G3PDH reverse primer, 5'-GGCATTGCTGCAAAGAAAGAG-3'; Clonetics kit was used for PCR. PCRs were performed with the ABI PCR System 2700 (Applied Biosystem). The PCR conditions were 95 °C for 5 min, followed by 35 cycles of 95 °C for 30 seconds, 60 °C for 30 seconds and 72 °C for lmin.

3) Preparation of digoxigenin-labeled RNA probes

Ephrin-B2 and EphB4 PCR products were cloned using the pGEM-T Easy System (Promega, Madison WI) according to the manufacturer's description. The primers and PCR products were 5'-tccgtgtggaagtactgctg-3' (forward), 5'-tctggtttggcacagttgag-3' (reverse), for ephrin-B2 that yielded a 296-bp product and 5'-ctttggaagagaccctgctg-3' (forward), 5 ^s- agacggtgaaggtctccttg-3', for EphB4 that yielded a 297-bp product. The authenticity and insert orientation were confirmed by DNA sequencing.

The pGEM-T Easy plasmids containing the PCR product ofthe human ephrin-B2 or EphB4 gene were linearized with Spe I or Nco I. Antisense or sense digoxigenin (DIG)- labeled RNA probes were transcribed from T7 or SP6 promoters by ran-off transcription using a DIG RNA labeling kit (Roche, Indianapolis IN). RNA probes were quantitated by spot assay as described in the DIG RNA labeling kit instructions.

4) In situ hybridization

Cells were cultured in Labtech II 4-well chamber slides (Nalge Nunc International, Naperville, IL). Cells were washed in PBS (37 °C), then fixed for 30 min at 25 °C in a solution of 4% (w/v) foπnaldehyde, 5% (v/v) acetic acid, and 0.9%> (w/v) NaCl. After fixation, slides were rinsed with PBS and stored in 70% ethanol at 4 °C until further use. Before in situ hybridization, cells were dehydrated, washed in 100% xylene to remove residual lipid and then rehydrated, finally in PBS. Cells were permeabihzed by incubating at 37 °C with 0.1%) (w/v) pepsin in 0.1 N HCl for 20 min and post-fixed in 1% formaldehyde for 10 min. Prehybridization was performed for 30 min at 37 °C in a solution of 4 X SSC containing 50%(v/v) deionized formamide. Slides were hybridized overnight at 42 °C with 25 ng antisense or sense RNA probes in 40% deionized formamide, 10%> dextran sulfate, IX Denhardt's solution, 4 X SSC, 10 mM DTT, 1 mg/ml yeast t-RNA and lmg/ml denatured and sheared salmon spenn DNA in a total volume of 40 μl. Slides were then washed at 37 °C as follows: 2 X 15 min with 2 X SSC, 2 X 15min with 1 X SSC, 2 X 15 min with 0.5 X SSC and 2 X 30 min with 0.2 X SSC. Hybridization signal was detected using alkaline- phosphatase-conjugated anti-DIG antibodies (Roche) according to the manufacturer's instructions. Color development was stopped by two washes in 0.1 M Tris-HCl, linM EDTA, pH 8.0 for 10 min. Cells were visualized by counterstaining of nucleic acids with Nuclear Fast Red (Vector Laboratories, Burlingame, CA) and the slides were mounted with DVIMU- MOUNT (Shandon, Astmoor UK).

5) Western Blot

Crude cell lysates were prepared by incubation in cell lysis buffer (10 mM Tris, pH 7.5, 1 mM EDTA, 150 mM NaCl, 1 % Triton X-100, 1 mM DTT, 10 % glycerol). Lysates were cleared by centrifugation at 10,000 x g for 10 min. Total protein was determined by Bradford assay (Bio-Rad). Samples (20 μg protein) were fractionated on a 4-20 % Tris- glycine polyacrylamide gel and transfened to polyvinylidene difluoride (PVDT) membrane (Bio-Rad) by electroblotting. Membranes were blocked with 5 % non-fat milk prior to incubation with antibody to EphB4 (1:5000 dilution) at 4° C, for 16 h. Secondary antibody (1:100,000 dilution) conjugated with horseradish peroxidase was applied for 1 h at 25 °C. The membranes were developed using the SuperSignal West Femto Maximum sensitivity chemiluminescent substrate (Pierce, Rockford, IL) according to the manufacturer's instructions.

6) hnmunohistochemistry

Formalin-fixed tissue sections were deparaffinized and incubated with 10%) goat serum at -70 °C for 10 minutes and incubated with the primary rabbit antibodies against either Ephrin B2 or EphB4 (Santa Cruz Biotechnologies; 1:100) at 4 °C overnight. Isotype- specific rabbit IgG was used as control. The immunoreactivity for these receptors was revealed using an avidin-biotin kit from Vector Laboratories. Peroxidase activity was revealed by the diaminobenzidine (Sigma) cytochemical reaction. The slides were then counterstained with H&E.

7) Immunofluorescence studies Cells were cultured on Labtech II 4-well chamber slides and fixed in 4% parafomialdehyde in Dulbecco's phosphate buffered saline pH 7.4 (PBS) for 30 min. The slides were rinsed twice in PBS and preincubated with blocking buffer (0.2%> Triton-XlOO, 1% BSA in PBS) for 20 min. The slides were then incubated with antibodies to EphB4 or ephrin B2 (1:100 dilution in PBS) in blocking buffer at 4 °C for 16 hr. After washing three times, the slides were incubated with the appropriate fluorescein-conjugated secondary antibodies (Sigma-Aldrich, St. Louis, MO). Nuclei were counterstained with 4',6-diamidino- 2-phenylindole dihydrochloride hydrate (DAPI), washed extensively with PBS and mounted with Vectasheild antifade mounting solution (Vector Laboratories). Images were obtained using an Olympus AX70 fluorescence microscope and Spot v2.2.2 (Diagnostic Instruments Inc., Sterling Heights, MI) digital imaging system.

8) Cell viability assay

Cells were seeded at a density of 5 x 10 per well in 48-well plates on day 0 in appropriate growth media containing 2% fetal calf serum (FCS). On the following day, the media was changed and cells were freated with various concenfrations (1-10 μM) of EphB4 Antisense. On day 4, viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) at a final concentration of 0.5 mg/ml. Cells were incubated for 2 hr, medium was aspirated, and the cells were dissolved in acidic isopropanol (90% isopropanol, 0.5% SDS and 40 mM HCl). Optical density was read in an ELISA reader at 490 nm using isopropanol as blank (Molecular Devices, CA). 9) Cell migration

In vitro wound healing assay was adopted. Briefly, cells were seeded onto 6-cm plates in full culture media for 24 hours, and then switched to medium containing 5% FBS. EPHB4 antisense 10 (10 μM) was also added to treated well. 24 hours later, wounds were made using the tip of a p-200 pipette man; a line was drawn through the middle ofthe plates. The plate was photographed at 0, 12, 24 hours. The experiment was repeated three times. Example 5. EphB4 Is Expressed in Squamous Cell Carcinoma of The Head and Neck: Regulation by Epidermal Growth Factor Signaling Pathway and Growth Advantage.

Squamous cell carcinoma ofthe head and neck (HNSCC) is the sixth most frequent cancer worldwide, with estimated 900,000 cases diagnosed each year. It comprises almost 50%) of all malignancies in some developing nations, h the United States, 50,000 new cases and 8,000 deaths are reported each year. Tobacco carcinogens are believed to be the primary etiologic agents ofthe disease, with alcohol consumption, age, gender, and ethnic background as contributing factors.

The differences between normal epithelium ofthe upper aerodigestive tract and cancer cells arising from that tissue are the result of mutations in specific genes and alteration of their expression. These genes control DNA repair, proliferation, immortalization, apoptosis, invasion, and angiogenesis. For head and neck cancer, alterations of tliree signaling pathways occur with sufficient frequency and produce such dramatic phenotypic changes as to be considered the critical transforming events ofthe disease. These changes include mutation ofthe p53 tumor suppressor, overexpression of epidermal growth factor receptor (EGFR), and inactivation ofthe cyclin dependent kinase inhibitor pi 6. Other changes such as Rb mutation, ras activation, cyclin D amplification, and myc overexpression are less frequent in HNSCC.

Although high expression of EphB4 has been reported in hematologic malignancies, breast carcinoma, endometrial carcinoma, and colon carcinoma, there is limited data on the protein levels of EphB4, and complete lack of data on the biological significance of this protein in tumor biology such as HNSCC.

A. HNSCC tumors express EphB4

We studied the expression of EphB4 in human tumor tissues by immunohistochemistry, in situ hybridization, and Western blot. Twenty prospectively collected tumor tissues following IRB approval have been evaluated with specific EphB4 monoclonal antibody that does not react with other members ofthe EphB and EphA family. EphB4 expression is observed in all cases, with varying intensity of staining. Figure 39A (top left) illustrates a representative case, showing that EphB4 is expressed in the tumor regions only, as revealed by the H&E tumor architecture (Fig. 39A bottom left). Note the absence of staining for EphB4 in the stroma. Secondly, a metastatic tumor site in the lymph node shows positive staining while the remainder ofthe lymph node is negative (Fig. 39A, top right).

In situ hybridization was carried out to determine the presence and location of EphB4 transcripts in the tumor tissue. Strong signal for EphB4 specific antisense probe was detected indicating the presence of transcripts (Figure 39 B, top left). Comparison with the H&E stain (Fig. 39B, bottom left) to illustrate tumor architecture reveals that the signal was localized to the tumor cells, and was absent from the stromal areas. Ephrin B2 transcripts were also detected in tumor sample, and as with EphB4, the signal was localized to the tumor cells (Fig. 39B, top right). Neither EphB4 nor ephrin B2 sense probes hybridized to the sections, proving specificity ofthe signals.

B. High expression of EphB4 in primary and metastatic sites of HNSCC

Western blots of tissue from primary tumor, lymph node metastases and uninvolved tissue were carried out to determine the relative levels of EphB4 expression in these sites. Tumor and normal adjacent tissues were collected on 20 cases, while lymph nodes positive for tumor were harvested in 9 of these 20 cases. Representative cases are shown in figure 39C. EphB4 expression is observed in each ofthe tumor samples. Similarly, all tumor positive lymph nodes show EphB4 expression that was equal to or greater than the primary tumor. No or minimal expression is observed in the normal adjacent tissue.

C. EphB4 expression and regulation by EGFR activity in HNSCC cell lines Having demonstrated the expression of EphB4 limited to tumor cells, we next sought to determine whether there was an in vitro model of EphB4 expression in HNSCC. Six HN SCC cell lines were surveyed for EphB4 protein expression by Western Blot (Fig. 40A). A majority of these showed strong EphB4 expression and thus established the basis for subsequent studies. Since EGFR is strongly implicated in HNSCC we asked whether EphB4 expression is associated with the activation of EGFR. Pilot experiments in SCC-15, which is an EGFR positive cell line, established an optimal time of 24 h and concentration of 1 mM of the specific EGFR kinase inhibitor AG 1478 (Figure 40B) to inhibit expression of EphB4. When all the cell lines were studied, we noted robust EGFR expression in all but SCC-4, where it is detectable but not strong (Fig. 40C, top row). In response to EGFR inhibitor AG1478 marked loss in the total amount of EphB4 was observed in certain cell lines (SCC- 15, and SCC-25) while no effect was observed in others (SCC-9, -12, -13 and -71). Thus SCC-15 and -25 serve as models for EphB4 being regulated by EGFR activity, while SCC-9, -12, -13 and -71 are models for regulation of EphB4 in HNSCC independent of EGFR activity, where there may be input from other factors such as p53, PTEN, IL-6 etc. We also noted expression ofthe ligand of EphB4, namely ephrin B2, in all ofthe cell lines tested. As with EphB4 in some lines eplirin B2 expression appears regulated by EGFR activity, while it is independent in other cell lines.

Clearly, inhibition of constitutive EGFR signaling repressed EphB4 levels in SCC15 cells. We next studied whether EGF could induce EphB4. We found that EphB4 levels were induced in SCC 15 cells that had been serum starved for 24 h prior to 24 h treatment with 10 ng/ml EGF as shown in figure 41B (lanes 1 and 2). The downstream signaling pathways known for EGFR activation shown in figure 41A, (for review see Yarden & Slikowski 2001) were then investigated for their input into EGF mediated induction of EphB4. Blocking PLCg, AKT and INK phosphorylation with the specific kinase inhibitors U73122, SH-5 and SP600125 respectively reduced basal levels and blocked EGF stimulated induction of EphB4 (Fig. 41B, lanes 3-8). In contrast, inhibition of ERK1/2 with PD098095 and PI3-K with LY294002 or Wortmannin had no discernible effect on EGF induction of EphB4 levels.

However, basal levels of EphB4 were reduced when ERK1/2 phosphorylation was inhibited. Interestingly, inhibition of p38 MAPK activation with SB203580 increased basal, but not EGF induced EplιB4 levels. Similar results were seen in the SCC25 cell line (data not shown). D. Inhibition of EphB4 in high expressing cell lines results in reduced viability and causes cell-cycle anest

We next turned to the role of EphB4 expression in HNSCC by investigating the effect of ablating expression using siRNA or AS-ODN methods. Several siRNAs to EphB4 sequence were developed (Table 1) which knocked-down EphB4 expression to varying degrees as seen in figure 42A. Viability was reduced in SCC-15, -25 and -71 cell lines transfected with siRNAs 50 and 472, which were most effective in blocking EphB4 expression (Figure 42B). Little effect on viability was seen with EphB4 siRNA 1562 and 2302 or ephrin B2 siRNA 254. Note that in SCC-4, which does not express EphB4 (see Fig. 40 A) there was no reduction in cell viability. The decreased cell viability seen with siRNA 50 and 472 treatment was attributable to accumulation of cells in sub GO, indicative of apoptosis. This effect was both time and dose-dependant (Figure 42C and Table 2). In contrast, siRNA2302 that was not effective in reducing EphB4 levels and had only minor effects on viability did not produce any changes in the cell cycle when compared with the mock Lipofectamine™2000 transfection.

Table l : EphB4 siRNAs

Name siRNA sequence

Eph B4 50: 5 ' -GAGACCCUGCUGAACACAAUU-3 ' 3 ' -UUCUCUGGGACGACUUGUGUU-5 '

Eph B4 472: 5 ' -GGUGAAUGUCAAGACGCUGUU-3 ' 3 ' -UUCCACUUACAGUUCUGCGAC-5 '

Eph B4 1562: 5 ' -CAUCACAGCCAGACCCAACUU-3 ' 3 ' -UUGUAGUGUCGGUCUGGGUUG-5 '

Eph B4 2302 5' -CUCUUCCGAUCCCACCUACUU-3 ' 3 ' -UUGAGAAGGCUAGGGUGGAUG-5 '

Table 2: Effect of different EphB4 siRNA on Cell Cycle

Treatment Sub GO G1 S G2

36hr

Lipo alone 1.9 39.7 21.3 31.8

100 nM 2302 2.0 39.3 21.2 31.2

100 nM 50 18.1 31.7 19.7 24.4

100 nM 472 80.2 10.9 5.2 2.1

16hr

Lipo alone 7.8 55.7 15.2 18.5

100 nM 2302 8.4 57.3 14.3 17.3

10 nM 50 10.4 53.2 15.7 17.7

100 nM 50 27.7 31.3 18.1 19.6

10 nM 472 13.3 50.2 15.8 17.5

100 nM 472 30.7 31.9 16.4 18.0 In addition, over 50 phosphorothioate AS-ODNs complementary to the human EphB4 coding sequences were synthesized and tested for their ability to inhibit EphB4 expression in 293 cells transiently transfected with full length EphB4 expression plasmid. Figure 43 A shows a representative sample ofthe effect of some of these AS-ODNs on EphB4 expression. Note that expression is totally abrogated with AS-10, while AS-11 has only a minor effect. The effect on cell viability in SCC 15 cells was most marked with AS-ODNs that are most effective in inhibiting EphB4 expression as shown in figure 43B. The IC₅₀ for AS-10 was approximately 1 μM, while even 10 μM AS-11 was not sufficient to attain 50 % reduction of viability. When the effect that AS-10 had on the cell cycle was investigated, it was found that the sub GO fraction increased from 1.9 % to 10.5 % compared to non-treated cells, indicative of apoptosis (Fig. 43C).

E. EphB4 regulates Cell migration

We next wished to determine if EphB4 participates in the migration of HNSCC. Involvement in migration may have implications for growth and metastasis. Migration was assessed using the wound-healing/scrape assay. Confluent SCC15 and SCC25 cultures were wounded by a single scrape with a sterile plastic Pasteur pipette, which left a 3 mm band with clearly defined borders. Migration of cells into the cleared area in the presence of test compounds was evaluated and quantitated after 24, 48 and 72 hr. Cell migration was markedly diminished in response to AS-10 that block EphB4 expression while the inactive compounds, AS-1 and scrambled ODN had little to no effect as shown in figure 43D.

Inhibition of migration with AS-10 was also shown using the Boyden double chamber assay (Fig. 43E).

F. EphB4 AS-10 in vivo anti-tumor activity

The effect of EphB4 AS-10, which reduces cell viability and motility, was determined in SCC15 tumor xenografts in Balb/C nude mice. Daily treatment of mice with 20 mg/kg AS- 10, sense ODN or equal volume of PBS by LP. injection was started the day following tumor cell implantation. Growth of tumors in mice receiving AS-10 was significantly retarded compared to mice receiving either sense ODN or PBS diluent alone (Figure 44). Non-specific effects attributable to ODN were not observed, as there was no difference between the sense ODN treated and PBS treated groups.

G. Materials and Methods

1) Cell lines and reagents HNSCC-4, -9, 12, -13, -15, -25, and -71 were obtained from and 293 human embryonic kidney cells were obtained from the ATCC (Manassas, VA). Cells were maintained in RPMI 1640 media supplemented with 10% heat-inactivated fetal bovine serum (FBS; Invitrogen, Carlsbad, CA) and antibiotics. EGFR, EphB4(C-16) polyclonal antibodies were from Santa Craz Biotech (Santa Cruz, CA). β-actin monoclonal antibody was purchased from Sigma Chemical Co. (St Louis, MO). Ephrin B2 and EphB4 polyclonal antibodies and their conesponding blocking peptides were obtained from Santa Craz Biotechnology (Santa Cruz, CA). AG 1478 (4-(3'-Chloroanilino)-6,7-dimethoxy-quinazoline) was from Calbiochem (San Diego, CA). Kinase inhibitors SH-5 and SP 600125 were from A.G. Scientific (San Diego, CA), PD98095, U73122, SB203580, LY294002, and Wortmannin were obtained from Sigma.

2) Preparation of digoxigenin-labeled RNA probes See above, e.g., Example 3.

3) In situ hybridization See above, e.g., Example 3.

4) Immunohistochemistry

Formalin-fixed tissue sections were deparaffinized and incubated with 10%> goat serum at -70 °C for 10 minutes and incubated with the EphB4 monoclonal antibody 4 °C overnight. Isotype specific rabbit IgG was used as control. The immunoreactivity for these receptors was revealed using an avidin-biotin kit from Vector Laboratories. Peroxidase activity was revealed by the diaminobenzidine (Sigma) cytochemical reaction. The slides were then counterstained with 0.12%> methylene blue or H&E. For frozen sections, OCT- embedded tissues were sectioned at 5 μm and fixed in phosphate-buffered 4%> parafomialdehyde. Sections were washed for 3 x 5 min in PBS and endogenous peroxidase was blocked by incubation in 0.3% H₂O₂ in PBS for 10 min at room temperature. Sections were incubated with Eph4 (C-16) antibody (1 :50) for 1 h at room temperature followed by three washes in PBS and incubation with donkey anti-goat secondary antibody (Santa Craz Biotech.) for 1 h at room temperature. After three washes in PBS, peroxidase activity was localized by incubation in DAB substrate solution (Vector Laboratories, Inc. Burlingame CA) for 10 min at room temperature. Sections were counterstained with Hematoxylin for 20 s, dehydrated and mounted. Negative control for staining was substitution of normal goat serum for primary antibody. Immunohistochemical staining on prostate anay (BioMeda, Foster City, CA) was done using goat ABC Staining System (Santa Craz Biotech.) according to the manufacturer's instructions.

5) Western Blot

See above, e.g., Example 3. 6) Synthesis of EphB4 siRNA by in vitro transcription

The Silencer™ siRNA construction kit (Ambion, Austin TX) was used to synthesize siRNA to EphB4. Briefly, 21 bp target sequences containing 19 bp downstream of 5'-AA dinucleotides were identified that showed no significant homology to other sequences in the GenBank database. Sense and antisense siRNA 29-mer DNA oligonucleotide templates were synthesized at the USC Noπis Microchemical Core Facility. Antisense template conesponded to the target sequence followed by 8 bp addition (5'-CCTGTCTC-3') at the 3' end complementary to the T7 promoter primer provided by the Silencer™ siRNA construction kit. Sense template comprised 5'-AA followed by the complement ofthe target 19 bp, then the T7 8 bp sequence as above. In separate reactions, the two siRNA oligonucleotide templates were hybridized to a

T7 promoter primer. The 3³ ends ofthe hybridized oligonucleotides were extended by the Klenow fragment of DNA polymerase to create double-stranded siRNA transcription templates. The sense and antisense siRNA templates were transcribed by T7 RNA polymerase and the resulting RNA transcripts were hybridized to create dsRNA. The leader sequences were removed by digesting the dsRNA with a single-stranded specific ribonuclease leaving the overhanging UU dinucleotides. The DNA template was removed at the same time by treatment with RNase free deoxyribonuclease. The resulting siRNA was purified by glass fiber filter binding to remove excess nucleotides, short oligomers, proteins, and salts in the reaction. The end products (shown in Table 3) were double-stranded 21-mer siRNAs with 3 ' terminal uridine that can effectively reduce the expression of target mRNA when transfected into cells.

A number of phosphorothioate AS-ODNs were also synthesized (Operon, Valencia CA) to test for inhibition of EphB4 expression (Table 3).

Table 3: EρhB4 Antisense ODNs

Name Position Sequence (5' -> 3') Eph B4 AS-1 (552-572) GTG CAG GGA TAG CAG GGC CAT Eph B4 AS-2 (952-972) AAG GAG GGG TGG TGC ACG GTG Eph B4 AS-3 (1007-1027) TTC CAG GTG CAG GGA GGA GCC Eph B4 AS-4 (1263-1285) GTG GTG ACA TTG ACA GGC TCA Eph B4 AS-5 (1555-1575) TCT GGC TGT GAT GTT CCT GGC Eph B4 AS-6 (123-140) GCC GCT CAG TTC CTC CCA Eph B4 AS-7 (316-333) TGA AGG TCT CCT TGC AGG Eph B4 AS-8 (408-428) CGC GGC CAC CGT GTC CAC CTT Eph B4 AS-9 (1929-1949) CTT CAG GGT CTT GAT TGC CAC Eph B4 AS-10 (1980-1999) ATG GAG GCC TCG CTC AGA AA Eph b4 AS-11 (2138-2158) CAT GCC CAC GAG CTG GAT GAC

7) Cell viability assay

Cells were seeded at a density of 5 x 10³ per well in 48-well plates on day 0 in appropriate growth media containing 2% fetal calf seram (FCS). Cells were treated with various concenfrations (1-10 μg/ml) of ODNs on days 2 and 4. On day 5, viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) as previously described (Masood et al ⁵03). For viability with siRNA, 2 x 10⁴ cells/well of SCC- 4, -15, -25 or -71 in a 48-well plate were transfected with siRNAs (10-100 nM) using 2 μl of Lipofectamine™ 2000 according to the manufacturer's instructions. 4 h post-transfection the cells were returned to growth media (RPMI 1640 supplemented with 10 % FBS). Viability was assayed by MTT 48 h following transfection.

8) Cell cycle analysis

80%) confluent cultures of SCC 15 cells in 6-well plates were transfected with siRNA472 (100 nM) using Lipofectamine™ 2000. Either 16 or 36 hours after transfection, cells were trypsinized, washed in PBS and incubated for 1 h at 4 °C in 1 ml of hypotonic solution containing 50 μg/ml propidium iodide, 0.1%> sodium citrate, 0.1 Triton X-100 and 20 μg/ml DNase-free RNaseA. Cells were analyzed in linear mode at the USC Flow cytometry facility. Results were expressed as percentages of elements detected in the different phases of the cell cycle, namely Sub GO pealc (apoptosis), G0/G1 (no DNA synthesis), S (active DNA systhesis), G2 (premitosis) and M (mitosis). For AS-ODN experiment the cells were exposed to 5 μM ODN for 36 h prior to processing.

9) Wound healing migration assay

SCC 15 cells were seeded into 6-well plates and cultured until confluent. 10 μM AS-1, AS-10, or sense ODN as control were infroduced to the wells as described for the viability assay 12 hours before wounding the monolayer by scraping it with a sterile pipette tip. Medium was changed to RPMI 1640 supplemented with 5% FBS and fresh ODNs. The healing process was examined dynamically and recorded with a Nikon Coolpix 5000 digital camera with microscope adapter. 10) Boyden Chamber assay of migration

Cell migration assays were performed as previously described (Masood ANUP paper '99) except that 1 μM AS-10 or AS-6 were added to the upper chamber. EGF (20 ng/ml) was used as chemoattractant in the lower chamber. Taxol at 10 ng/ml was used as a negative control. 11 ) In vivo studies

SCC15 (5 x 10⁶ cells) were injected subcutaneously in the lower back of 5-week old male Balb/C Nu /nu athymic mice. Treatment consisted of daily intraperitoneal injection of ODN (20 mg/kg in a total volume of 100 μl) or diluent (PBS) begun the day following tumor cell implantation and continued for two weeks. Tumor growth in mice was measured as previously described (Masood CCR '01). Mice were sacrificed at the conclusion ofthe study. All mice were maintained in accord with the University of Southern California Animal Care and Use Committee guidelines governing the care of laboratory mice.

Example 6. Ephrin B2 Expression in Kaposi's Sarcoma Is Induced by Human Herpesviras Type 8: Phenotype Switch from Venous to Arterial Endothelium

Kaposi's Sarcoma (KS) manifests as a multifocal angioproliferative disease, most commonly ofthe skin and mucus membranes, with subsequent spread to visceral organs (1) Hallmarks ofthe disease are angiogenesis, edema, infiltration of lymphomononuclear cells and growth of spindle-shaped tumor cells. Pathologically, established lesions exhibit an extensive vascular network of slit-like spaces. The KS vascular network is distinct from normal vessels in the lack of basement membranes and the abnormal spindle shaped endothelial cell (tumor cell) lining these vessels. Defective vasculature results in an accumulation ofthe blood components including albumin, red and mononuclear cells in the lesions (1). The KS tumor is endothelial in origin; the tumor cells express many endothelial markers, including lectin binding sites for Ulex europeaus agglutinin-1 (UEA-1), CD34, EN- 4, PAL-E (2) and the endothelial cell specific tyrosine kinase receptors, VEGFR-1 (Flt-1), VEGFR-2 (Flk-1/KDR), VEGFR-3 (Flt-4), Tie-1 and Tie-2 (3, RM & PSG unpublished data). KS cells co-express lymphatic endothelial cell related proteins including LYVE and podoplanin (4).

The herpesviras HHV-8 is considered the etiologic agent for the disease. In 1994 sequences of this new herpes virus were identified in KS tumor tissue (5), and subsequent molecular-epidemiology studies have shown that nearly all KS tumors contain viral genome. Sero-epidemiology studies show that HIV infected patients with KS have the highest prevalence of HHV-8 and secondly that those with HIV infection but no KS have increased risk of developement of KS over the ensuing years if they are also seropositive for HHV-8 (6). Direct evidence for the role of HHV-8 in KS is the transfomiation of bone manow endothelial cells after infection with HHV-8 (7). A number of HHV-8 encoded genes could contribute to cellular transformation (reviewed in 8). However, the most evidence has accumulated for the G-protein coupled receptor (vGPCR) in this role (9).

We investigated whether KS tumor cells are derived from arterial or venous endothelium. hi addition, we investigated whether HHV-8 has an effect on expression of arterial or venous markers in a model of KS. KS tumor cells were found to express the ephrin B2 arterial marker. Further, ephrin B2 expression was induced by HHV-8 vGPCR in KS and endothelial cell lines. Ephrin B2 is a potential target for treatment of KS because inhibition of ephrin B2 expression or signaling was detrimental to KS cell viability and function.

A. KS tumors express Eplirin B2, but not EphB4

The highly vascular nature of KS lesions and the probable endothelial cell origin of the tumor cells prompted investigation of expression of EphB4 and ephrin B2 which are markers for venous and arterial endothelial cells, respectively. Ephrin B2, but not EphB4 transcripts were detected in tumor cells of KS biopsies by in situ hybridization (figure 45A). Comparison ofthe positive signal with ephrin B2 antisense probe and tumor cells as shown by H&E staining shows that ephrin B2 expression is limited to the areas ofthe biopsy that contain tumor cells. The lack of signal in KS with EphB4 antisense probe is not due to a defect in the probe, as it detected transcripts in squamous cell carcinoma, which we have shown expresses this protein (18). Additional evidence for the expression of ephrin B2 in KS tumor tissue is afforded by the localization of EphB4/Fc signal to tumor cells, detected by FITC conjugated anti human Fc antibody. Because ephrin B2 is the only ligand for EphB4 this reagent is specific for the expression of ephrin B2 (figure 45B, left). An adjacent section freated only with the secondary reagent shows no specific signal. Two-color confocal microscopy demonstrated the presence ofthe HHV-8 latency protein, LANAl in the ephrin B2 positive cells (Fig. 45 C, left), indicating that it is the tumor cells, not tumor vessels, which are expressing this arterial marker. Staining of tumor biopsy with PECAM-1 antibody revealed the highly vascular nature of this tumor (Fig. 45C, right). A pilot study ofthe prevalence of this pattern of ephrin B2 and EphB4 expression on KS biopsies was conducted by RT-PCR analysis. All six samples were positive for ephrin B2, while only 2 were weakly positive for EphB4 (data not shown).

B. Infection of venous endothelial cells with HHV-8 causes a phenotype switch to arterial markers

We next asked whether HHV-8, the presumed etiologic agent for KS, could itself induce expression of ephrin B2 and repress EphB4 expression in endothelial cells. Co-culture of HUVEC and BC-1 lymphoma cells, which are productively infected with HHV-8, results in effective infection ofthe endothelial cells (16). The attached monolayers of endothelial cells remaining after extensive washing were examined for ephrin B2 and EphB4 by RT-PCR and immunofluorescence. HUVEC express EphB4 venous marker strongly at the RNA level, but not ephrin B2 (figure 46B). In contrast, HHV-8 infected cultures (HUVEC/BC-1 and HUVEC/BC-3) express eplirin B2, while EphB4 transcripts are almost absent.

Immunofluorescence analysis of cultures of HUVEC and HUVEC/HHV-8 for artery/vein markers and viral proteins was undertaken to determine whether changes in protein expression minored that seen in the RNA. hi addition, cellular localization of the proteins could be determined. Consistent with the RT-PCR data HUVEC are ephrin B2 negative and EphB4 positive (Fig. 46A(a & m)). As expected they do not express any HHV-8 latency associated nuclear antigen (LANAl) (Fig. 46A(b, n)). Co-culture of BC-1 cells, which are productively infected with HHV-8, resulted in infection of HUVEC as shown by presence of viral proteins LANAl and ORF59 (Fig. 46A(f, r)). HHV-8 infected HUVEC now express ephrin B2 but not EphB4 (Fig. 46A(e, q, u), respectively). Expression of ephrin B2 and LANAl co-cluster as shown by yellow signal in the merged image (Fig. 46A(h)). HHV-8 infected HUVEC positive for eplirin B2 and negative for Eph B 4 also express the arterial marker CD148 (19) (Fig. 46A (j, v)). Expression of ephrin B2 and CD148 co-cluster as shown by yellow signal in the merged image (Fig. 46A(1)). Uninfected HUVEC expressing Eph B4 were negative for CD 148 (not shown).

C. HHV-8 vGPCR induces ephrin B2 expression

To test whether individual viral proteins could induce the expression of ephrin B2 seen with the whole viras KS-SLK cells were stably transfected with HHV-8 LANA, or LANAΔ440 or vGPCR. Western Blot of stable clones revealed a five-fold induction of ephrin B2 in KS-SLK transfected with vGPCR compared to SLK-LANA or SLK-LANAΔ440 (Fig. 47A). SLK transfected with vector alone (pCEFL) was used as a confrol. SLK-vGPCR and SLK-pCEFL cells were also examined for ephrin B2 and Eph B4 expression by immunofluorescence in transiently transfected KS-SLK cells. Figure 47B shows higher expression of ephrin B2 in the SLK-vGPCR cells compared to SLK-pCEFL. No changes in Eph B4 were observed in SLK-vGPCR compared to SLK-pCEFL. This clearly demonstrates that SLK-vGPCR cells expressed high levels of ephrin B2 compared to SLK-pCEFL cells. This suggests that vGPCR of HHV-8 is directly involved in the induction of Ephrin B2 and the arterial phenotype switch in KS. Since we had shown that HHV-8 induced expression of ephrin B2 in HUVEC, we next asked if this could be mediated by a transcriptional effect.

Ephrin B2 5 '-flanking DNA-luciferase reporter plasmids were constructed as described in the Materials and Methods and transiently transfected into HUVECs. Ephrin B2 5 '-flanking DNA sequences -2491/-11 have minimal activity in HUVEC cells (figure 47C). This is consistent with ephrin B2 being an arterial, not venous marker. However, we have noted that HUVEC in culture do express some ephrin B2 at the RNA level. Cotransfection of HHV-8 vGPCR induces ephrin B2 transcription approximately 10-fold compared to the control expression vector pCEFL. Roughly equal induction was seen with ephrin B2 sequences - 2491/-11, -1242/-11, or -577/-11, which indicates that elements between -577 and -11 are sufficient to mediate the response to vGPCR, although maximal activity is seen with the - 1242/- 11 luciferase construct.

D. Expression of Ephrin B2 is regulated by VEGF and VEGF-C We next asked whether known KS growth factors could be involved in the vGPCR- mediated induction of ephrin B2 expression. SLK-vGPCR cells were treated with neutralizing antibodies to oncostatin-M, IL-6, IL-8, VEGF or VEGF-C for 36 hr. Figure 48A shows that neutralization of VEGF completely blocked expression of ephrin B2 in SLK- vGPCR cells. A lesser, but significant decrease in ephrin B2 was seen neutralization of

VEGF-C and IL-8. No appreciable effect was seen with neutralization of oncostatin-M or IL- 6. To verify that VEGF and VEGF-C are integral to the induction of ephrin B2 expression we freated HUVEC with VEGF, VEGF-C or EGF. HUVECs were grown in EBM-2 media containing 5 %> FBS with two different concentration of individual growth factor (10 ng, 100 ng/ml) for 48 h. Only VEGF-A or VEGF-C induced eplirin B2 expression in a dose dependent manner (Figure 48B). In contrast, EGF had no effect on expression of ephrin B2.

E. Ephrin B2 siRNA inhibits the expression of Ephrin B2 in KS

Three ephrin B2 siRNA were synthesized as described in the methods section. KS- SLK cells were transfected with siRNA and 48 h later ephrin B2 expression was determined by Western Blot. Ephrin B2 siRNAs 137 or 254 inhibited about 70% of ephrin B2 expression compared to control siRNA such as siRNA Eph B4 50 or siRNA GFP. Ephrin B2 63 siRNA was less effective than the above two siRNA Ephrin B2 (Figure 49 A).

F. Ephrin B2 is necessary for full KS and EC viability, cord formation and in vivo angiogenesis activities

The most effective ephrin B2 siRNA (254) was then used to detemiine whether inhibiting expression of ephrin B2 has any effect on the growth of KS-SLK or HUVEC cells. The viability of KS-SLK cells was decreased by the same siRNAs that inhibited eplirin B2 protein levels (figure 49B). KS-SLK express high levels of ephrin B2 and this result shows maintenance of ephrin B2 expression is integral to cell viability in this setting. HUVECs do not express ephrin B2, except when stimulated by VEGF as shown in Fig. 48B. Ephrin B2 siRNA 264 dramatically reduced growth of HUVECs cultured with VEGF as the sole growth factor. In contrast, no significant effect was seen when HUVECs were cultured with IGF, EGF and bFGF. As a control, EphB4 siRNA 50 had no detrimental effect on HUVECs in either culture condition (figure 49C).In addition to inhibition of viability of KS and primary endothelial cells, EphB4-ECD inhibits cord formation in HUVEC and KS-SLK and in vivo angiogenesis in the Matrigel™ plug assay (Figure 50). G. Methods and Materials

1) Cell lines and reagents

Human vascular endothelial cells (HUVEC) were from Clonetics (San Diego, CA) and were maintained in EGM-2 and EGM-2MV media respectively (Clonetics). TI human fibroblast line was from Dr. Peter Jones, USC. BC-1 and BC-3 human pleural effusion lymphoma cell lines and monoclonal antibodies to LANAl and ORF59 were the kind gift of Dr. Dharam Ablashi (Advanced Biotechnologies Inc., Columbia, MD). KS-SLK was isolated from a Classic Kaposi's sarcoma patient (15). Polyclonal antibodies to EphB4, ephrin B2, CD148, PECAM-1 were obtained from Santa Cruz Biotechnology (Santa Cruz, CA). Mouse EphB4/F_c' and monoclonal antibodies to human vascular endothelial growth factor (VEGF), VEGF-C, interleukin-(IL)6, IL-8 and oncostatin-M were purchased from R & D Systems (Minneapolis, MN). Expression vectors pKSvGPCR-CEFL and pCEFL were the kind gift of Dr. Enrique Mesri (Cornell University, New York, NY). Expression vectors for HHV-8 latency associated nuclear antigen (LANA) were kindly provided by Dr Matthew Rettig, Veteran's Administration Greater Los Angeles Healthcare System.

2) Collection and preparation of human tissue

Human cutaneous Kaposi's sarcoma biopsy material was obtained under local anesthesia with informed consent from patients at the LAC/USC Medical Center, using an IRB approved consent form. Biopsies were processed for either total RNA, paraffin blocks or frozen tissue blocks in OCT. Total RNA was extracted by homogenization in guanidine isothiocyanate, (RNAzol: Tel-Test, Inc., Friendswoods, TX). cDNAs were synthesized by reverse franscriptase using a random hexamer primer (Superscript II; Invitrogen, Carlsbad, CA).

3) Preparation of digoxigenin-labeled RNA probes

Eplirin B2 and EphB4 PCR products from the primers shown in Table 4 for in situ hybridization were cloned using the pGEM-T Easy system (Promega, Madison WI) according to the manufacturer's description using. The authenticity and insert orientation were confirmed by DNA sequencing. The pGEM-T Easy plasmids containing the PCR product ofthe human ephrin-B2 or EphB4 gene were linearized with Spe I or Nco I. Antisense or sense digoxigenin (DIG)-labeled RNA probes were transcribed from T7 or SP6 promoters by run-off transcription using a DIG RNA labeling kit (Roche, Indianapolis IN). RNA probes were quantitated by spot assay as described in the DIG RNA labeling kit instructions.

Table 4: Primers for Ephrin B2 and EphB4.

4) In situ hybridization

See above, e.g., Example 3.

5) Co-culture of HUVEC and BC-1

HUVEC cells were grown to 50-70%> confluence in EGM-2 on gelatin-coated Labtech II 4-well chamber slides (Nalge Nunc International, Naperville, IL). Co-culture with BC-1 or BC-3 was essentially as described by Sakurada and coworkers (16). Briefly, BC-1 or BC-3 cells were preheated with TPA (20 ng/ml) to induce viras for 48 hrs and then added to the HUVEC culture at a ratio of 10:1 for cocultivation for two days. The HUVECs were washed extensively with PBS to remove the attached BC-1 or BC-3 cells. 6) Preparation of cDNA and RT-PCR

The TITANIUM™ One-Step RT-PCR kit (Clontech, Palo Alto, CA) was used for RT-PCR from 1 x 10⁵ cells. Primer pairs for amplification of EphB4, ephrin B2 and β-actin are shown in Table 4. Each PCR cycle consisted of denaturation at 94 °C for 30 s, primer annealing at 60 °C for 30 s and extension at 72 °C for 30 s. The samples were amplified for 30 cycles. PCR products were separated on 1.5% agarose gels and stained with ethidium bromide.

7) Cell viability assay

KS-SLK cells were seeded at a density of 1 x 10⁴ per well in 48-well plates on day 0 in appropriate growth media containing 2% fetal calf seram (FCS). On the following day, the media was changed and cells were freated with 0, 10 or 100 nM siRNA. On day 3, viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) as previously described (17).

8) Immunofluorescence studies

Cells cultured on Labtech II 4-well chamber slides or frozen sections of KS biopsy material were fixed in 4% parafomialdehyde in Dulbecco's phosphate buffered saline pH 7.4 (PBS) for 30 min. The slides were rinsed twice in PBS and preincubated with blocking buffer (0.2%) Triton-XlOO, 1% BSA in PBS) for 20 min, followed by incubation with antibodies to EphB4, ephrin B2, CD148, LANAl or ORF59 (1 :100 dilution in PBS) in blocking buffer at 4 °C for 16 hr. After washing three times, the slides were incubated with the appropriate fluorescein or rhodamine-conjugated secondary antibodies (Sigma-Aldrich, St. Louis, MO). Nuclei were counterstained with 4',6-diamidino-2-phenylindole dihydrochloride hydrate (DAPI), washed extensively with PBS and mounted with Vectasheild antifade mounting solution (Vector Laboratories, Burlingame, CA). Images were obtained using a Olympus AX70 fluorescence microscope and Spot v2.2.2 (Diagnostic Instruments Inc., Sterling Heights, MI) digital imaging system.

Immunofluorescence detection of EphrinB2 with EPHB4-Fc was done as follows. Frozen sections fixed in 4% parafomialdehyde and blocked with 20% FBS were incubated with 5 μg/ml EphB4/Fc (R&D Systems) for 1 h at RT. Sections were then incubated with 10 μg/ml rabbit anti-human IgG-FITC in PBS (Jackson ImmunoResearch Laboratories West Grove, PA) at RT for 1 hour. Nuclei were counterstained with DAPI and sections mounted as above. Human Fc (Jackson ImmunoResearch) was used as the negative confrol.

9) Western Blot

Crude cell lysates were prepared, quantitated, fractionated and transfened to membranes as described previously (17). Membranes were blocked with 5%> non-fat milk prior to incubation with antibody to ephrin B2 (1 :5000 dilution) at 4 °C, for 16 h. Secondary antibody (1:100,000 dilution) conjugated with horseradish peroxidase was applied for 1 h at 25 °C. The membranes were developed using the SuperSignal West Femto Maximum sensitivity chemiluminescent substrate (Pierce, Rockford, IL) according to the manufacturer's instructions. Membranes were stripped using Restore™ Western Blot Stripping Buffer (Pierce) and reprobed with EphB4 or β-actin.

10) Cord formation assay

Matrigel™ Basement Membrane Matrix (BD Biosciences Discovery Labware, Bedford, MA) was mixed with growth medium (3:1) on ice and 0.5 ml liquid placed in 24- well plates. Incubation of plates at 37 °C for 15 min caused Matrigel™¹ polymerization.

HUVEC or KS-SLK in exponential phase growth were treated with 2 or 8 μg/ml EphB4-ECD or PBS as control for 16 h prior to trypsinizing and plating on the Matrigel™. Culture on Matrigel was continued in the presence of recombinant fusion proteins for 6 h. Cultures were fixed in 4% parafomialdehyde for 30 min and evaluated by inverted phase-contrast photomicroscopy.

11) Synthesis of Ephrin B2 and EphB4 siRNA by in vitro transcription

The Silencer™ siRNA constraction kit (Ambion, Austin TX) was used to synthesize siRNA to eplirin B2 and EphB4. Briefly, three 21 bp target sequences comprising 19 bp downstream of a 5'-AA dinucleotide were identified in the ephrin B2 cDNA (Accession number NM_004093) that showed no significant homology to other sequences in the

GenBank database. Sense and antisense siRNA 29-mer DNA oligonucleotide templates were synthesized at the USC Nonis Microchemical Core Facility. Antisense template conesponded to the target sequence followed by 8 bp addition (5'-CCTGTCTC-3') at the 3' end complementary to the T7 promoter primer provided with the Silencer SiRNA Constraction Kit. Sense template comprised 5'-AA followed by the complement ofthe target 19 bp, then the T7 8 bp sequence as above. In separate reactions, the two siRNA oligonucleotide templates were hybridized to a T7 promoter primer. The 3' ends ofthe hybridized oligonucleotides were extended by the Klenow fragment of DNA polymerase to create double-stranded siRNA transcription templates. The sense and antisense siRNA templates were transcribed by T7 RNA polymerase and the resulting RNA transcripts were hybridized to create dsRNA. The dsRNA consisted of 5' terminal single-stranded leader sequences, a 19 nt target specific dsRNA, and 3' terminal UUs. The leader sequences were removed by digesting the dsRNA with a single-stranded specific ribonuclease. The DNA template was removed at the same time by treatment with RNAse free deoxyribonuclease.

The resulting siRNAs were purified by glass fiber filter binding to remove excess nucleotides, short oligomers, proteins, and salts in the reaction. End product double-stranded 21mer siRNAs are shown in Table 5. Similarly, an EphB4 and green fluorescence protein (GFP) siRNAs were synthesized.

Table 5: siRNAs of eplirin B2 and EphB4.

12) Transfection of Ephrin B2 or EplιB4 siRNA

HUVEC were seeded on eight-well chamber slides coated with fibronectin and grown overnight in EGM-2 (Cambrex, WalkersviUe, MD). 16 h later media was replaced either with EBM-2 supplemented with 5% fetal calf serum (FCS) and EGM-2 BulletKit supplements bFGF, hEGF and R -IGF-I at the concentrations provided by the manufacturer, or EBM-2 supplemented with 5% FCS and 10 ng/ml rhVEGF (R&D Systems). After 2 h incubation at 37 °C, the cells were transfected using Lipofectamine 2000 (1 μg/ml; Invitrogen) and 10 nM specific siRNAs in Opti-MEM-1 serum-free medium (Invitrogen). Following transfection for 2 hr in Opti-MEM-1, media supplemented as above was replaced in the appropriate wells. After 48 hrs, the cells were stained with crystal violet and immediately photographed at 10X magnification.

13) Construction of ephrin B2 reporter plasmids

Human ephrin B2 5 '-flanking DNA from -2491 to -11 with respect to the translation start site was amplified from BACPAC clone RP11-29716 (BacPac Resources, Children's Hospital, Oakland, CA) using the Advantage GC Genomic PCR kit (Clontech Palo Alto, CA) to overcome the large tracts of CG-rich sequence in the target area. Primers were designed to contain Mlul sites for cloning. Amplified product was digested with Mlul, gel purified and ligated into the Mlul site in the multiple cloning site of pGL3Basic (Promega, Madison, WI). Orientation ofthe resulting clones was confirmed by restriction digest analysis. The conect clone was designated pEFNB2_{-2 1/-}nluc. Digestion of this clone with either Kpnl or Sacl followed by recircularization yielded pEFNB2_-1242/-iiluc and pEFNB2_-577/-ι₁luc, respectively. Plasmid DNAs used for transient transfections were purified using a Mega Prep kit (QIAGEN, Valencia, CA).

14) Transient transfection

HUVEC cells (0.8 x 10⁴ cells/well in 24 well plates) maintained in EGM-2 media were transiently co-transfected with 0.5 μg/well eplirin B2 promoter-luciferase constructs together with 50 ng/well either pCEFL or pKSvGPCR-CEFL, using Superfect reagent (QIAGEN) according to the manufacturer's instructions. Cells were harvested 48 h post- transfection and lysed with Luciferase cell lysis buffer (Promega). Luciferase activity was assayed using the Luciferase Assay System (Promega) according to the manufacturer's instructions. Luciferase was normalized to protein, because pCEFL-vGPCR induced the expression of β-galactosidase from pCMV-Sport-βgal (Invitrogen).

15) Construction and purification of EphB4 extra cellular domain (ECD) protein

See above, e.g., Example 1.

Example 7. Expression of EphB4 in Bladder cancer: a candidate target for therapy Figure 51 shows expression of EPHB4 in bladder cancer cell lines (A), and regulation of EPHB4 expression by EGFR signaling pathway (B).

Figure 55 shows effects of EPHB4 antisense probes on cell migration. 5637 cells were treated with EPHB4AS10 (10 μM).

Figure 56 shows effects of EPHB4 siRNA on cell invasion. 5637 cells were transfected with siRNA 472 or control siRNA.

Example 8. Inhibition of EphB4 Gene Expression by EphB4 antisense probes and RNAi probes

Cell lines expressing EphB4 were treated with the synthetic phosphorothioate modified oligonucleotides and harvested after 24 hr. Cell lysates were prepared and probed by western blot analysis for relative amounts of EphB4 compared to untreated control cells.

Studies on inhibition of cell proliferation were done in HNSCC cell lines characterized to express EphB4. Loss of cell viability was shown upon knock-down of EphB4 expression. Cells were treated in vitro and cultured in 48-well plates, seeded with 10 thousand cells per well. Test compounds were added and the cell viability was tested on day 3. The results on EphB4 antisense probes were summarized below in Table 6. The results on EphB4 RNAi probes were summarized below in Table 7.

Table 6. Inhibition of EphB4 Gene Expression by EphB4 antisense probes

Name Sequence 5'-> 3' position Inhibition Percent of EphB4 reduction Expression in viability

Eph B4 169 TCA GTA CTG CGG GGC CGG TCC (2944-2963) ++ 36

Eph B4 168 TCC TGT CCC ACC CGG GGT TC (2924-2943) ++ 51

Eph B4 167 CCG GCT TGG CCT GGG ACT TC (2904-2923) +++ 66

Eph B4 166 ATG TGC TGG ACA CTG GCC AA (2884-2903) ++++ 70

Eph B4 165 GAT TTT CTT CTG GTG TCC CG (2864-2883) ++++ 75

Eph B4 164 CCA GAG TGA CTC CGA TTC GG (2844-2863) ++ 40

Eph B4 163 AGC AGG TCC TCA GCA GAG AT (2824-2843) ++++ 66

Eph B4 162 CTG GCT GAC CAG CTC GAA GG (2804-2823) 25 Eph B4 161 AGC CAA AGC CAG CGG CTG CG (2784-2803) + 33

Eph B4 160 AAA CTT TCT TCG TAT CTT CC (2763-2783) + 25

Eph B4 159 CAT TTT GAT GGC CCG AAG CC (2743-2762) ++ 40

Eph B4 158 ACT CGC CCA CAG AGC CAA AA (2723-2742) 30

Eph B4 157 GCT GAG TAG TGA GGC TGC CG (2703-2722) + 25

Eph B4 156 CTG GTC CAG GAG AGG GTG TG (2683-2702) ++ 30

Eph B4 155 AGG CCC CGC CAT TCT CCC GG (2663-2682) 25

Eph B4 154 GCC ACG ATT TTG AGG CTG GC (2643-2662) ++ 40

Eph B4 153 GGG GTT CCG GAT CAT CTT GT (2623-2642) ++ 35

Eph B4 152 CCA GGG CGC TGA CCA CCT GG (2603-2622) + 30

Eph B4 151 GGG AAG CGG GGC CGG GCA T (2583-2602) + 25

Eph B4 150 CCG GTC TT CTG CCA ACA GT (2563-2582) ++ 25

Eph B4 149 CCA GCA TGA GCT GGT GGA GG (2543-2562) ++ 20

Eph B4 148 GAG GTG GGA CAG TCT GGG GG (2523-2542) + 30

Eph B4 147 CGG GGG CAG CCG GTA GTC CT (2503-2522) ++ 40

Eph B4 146 GTT CAA TGG CAT TGA TCA CG (2483-2502) ++++ 70

Eph B4 145 CC TGA TTG CTC ATG TCC CA (2463-2482) ++++ 80

Eph B4 144 GTA CGG CCT CTC CCC AAA TG (2443-2462) +++ 60

Eph B4 143 ACA TCA CCT CCC ACA TCA CA (2423-2442) ++++ 80

Eph B4 142 ATC CCG TAA CTC CAG GCA TC (2403-2422) ++ 40

Eph B4 141 ACT GGC GGA AGT GAA CTT CC (2383-2402) +++ 50

Eph B4 140 GGA AGG CAA TGG CCT CCG GG (2363-2382) ++ 45

Eph B4 139 GCA GTC CAT CGG ATG GGA AT (2343-2362) ++++ 70

Eph B4 138 CTT TCC TCC CAG GGA GCT CG (2323-2342) ++++ 70

Eph B4 137 TGT AGG TGG GAT CGG AAG AG (2303-2322) ++ 40

Eph B4 136 TC TCC TCC AGG AAT CGG GA (2283-2302) ++ 35

Eph B4 135 AAG GCC AAA GTC AGA CAC T (2263-2282) ++++ 60

Eph B4 134 GCA GAC GAG GTT GCT GTT GA (2243-2262) ++ 50

Eph B4 133 CTA GGA TGT TGC GAG CAG CC (2223-2242) ++ 40

Eph B4 132 AGG TCT CGG TGG ACG TAG CT (2203-2222) ++ 40

Eph B4 131 CAT CTC GGC AAG GTA CCG CA (2183-2202) +++ 50

Eph B4 130 TGC CCG AGG CGA TGC CCC GC (2163-2182) ++ 50

Eph B4 129 AGC ATG CCC ACG AGC TGG AT (2143-2162) ++ 50

Eph B4 128 GAC TGT GAA CTG TCC GTC GT (2123-2142) ++ 50

Eph B4 127 TTA GCC GCA GGA AGG AGT CC (2103-2122) +++ 60

Eph B4 126 AGG GCG CCG TTC TCC ATG AA (2083-2102) ++ 50

Eph B4 125 CTC TGT GAG AAT CAT GAC GG (2063-2082) ++++ 80

Eph B4 124 GCA TGC TGT TGG TGA CCA CG (2043-2062) ++++ 70

Eph B4 123 CCC TCC AGG CGG ATG ATA TT (2023-2042) ++ 50

Eph B4 122 GGG GTG CTC GAA CTG GCC CA (2003-2022) ++++ 80

Eph B4 121 TGA TGG AGG CCT CGC TCA GA (1983-2002) ++ 50

Eph B4 120 AAC TCA CGC CGC TGC CGC TC (1963-1982) ++ 40

Eph B4 119 CGT GTA GCC ACC CTT CAG GG (1943-1962) ++++ 75

Eph B4 118 TCT TGA TTG CCA CAC AGC TC (1923-1942) ++++ 80

Eph B4 117 TCC TTC TTC CCT GGG GCC TT (1903-1922) ++++ 70

Eph B4 116 GAG CCG CCC CCG GCA CAC CT (1883-1902) ++ 50

Eph B4 115 CGC CAA ACT CAC CTG CAC CA (1863-1882) ++++ 60

Eph B4 114 ATC ACC TCT TCA ATC TTG AC (1843-1862) ++++ 65

Eph B4 113 GTA GGA GAC ATC GAT CTC TT (1823-1842) ++++ 90

Eph B4 112 TTG CAA ATT CCC TCA CAG CC (1803-1822) ++++ 70

Eph B4 111 TCA TTA GGG TCT TCA TAA GT (1783-1802) ++++ 70

Eph B4 110 GAA GGG GTC GAT GTA GAC CT (1763-1782) ++++ 80

Eph B4 109 TAG TAC CAT GTC CGA TGA GA (1743-1762) ++ 50

Eph B4 108 TAC TGT CCG TGT TTG TCC GA (1723-1742) ++ 45

Eph B4 107 ATA TTC TGC TTC TCT CCC AT (1703-1722) ++++ 70

Eph B4 106 TGC TCT GCT TCC TGA GGC AG (1683-1702) ++++ 70

Eph B4 105 AGA ACT GCG ACC ACA ATG AC (1663-1682) ++ 40

Eph B4 104 CAC CAG GAC CAG GAC CAC AC (1643-1662) ++++ 70 Eph B4 103 CCA CGA CTG CCG TGC CCG CA (1623-1642) ++ 40

Eph B4 102 ATC AGG GCC AGC TGC CC CG (1603-1622) +++ 50

Eph B4 101 CCA GCC CTC GCT CTC ATC CA (1583-1602) ++++ 80

Eph B4 100 GTT GGG TCT GGC TGT GAT GT (1563-1582) ++++ 80

Eph B4 99 TCC TGG CCG AAG GGC CCG TA (1543-1562) ++ 35

Eph B4 98 GCC GGC CTC AGA GCG CGC CC (1523-1542) ++ 50

Eph B4 97 GTA CCT GCA CCA GGT AGC TG (1503-1522) ++++ 80

Eph B4 96 GCT CCC CGC TTC AGC CCC CG (1483-1502) ++ 50

Eph B4 95 CAG CTC TGC CCG GTT TTC TG (1463-1482) ++ 50

Eph B4 94 ACG TCT TCA GGA ACC GCA CG (1443-1462) ++++ 80

Eph B4 93 CTG CTG GGA CCC TCG GCG CC (1423-1442) ++ 40

Eph B4 92 CTT CTC ATG GTA TTT GAC CT (1403-1422) ++++ 80

Eph B4 91 CGT AGT CCA GCA CAG CCC CA (1383-1402) ++++ 85

Eph B4 90 CTG GGT GCC CGG GGA ACA GC (1363-1382) +++ 50

Eph B4 89 CCA GGC CAG GCT CAA GCT GC (1343-1462) ++++ 70

Eph B4 88 TGG GTG AGG ACC GCG TCA CC (1323-1342) ++ 40

Eph B4 87 CGG ATG TCA GAC ACT GCA GG (1303-1322) ++++ 60

Eph B4 86 AGG TAC CTC TCG GTC AGT GG (1283-1302) ++ 50

Eph B4 85 TGA CAT TGA CAG GCT CAA AT (1263-1282) ++++ 80

Eph B4 84 GGG ACG GGC CCC GTG GCT AA (1243-1262) ++ 50

Eph B4 83 GGA GGA TAC CCC GTT CAA TG (1223-1242) +++ 60

Eph B4 82 CAG TGA CCT CAA AGG TAT AG (1203-1222) ++++ 70

Eph B4 81 GTG AAG TCA GGA CGT AGC CC (1183-1202) +++ 60

Eph B4 80 TCG AAC CAC CAC CCA GGG CT (1163-1182) +++ 50

Eph B4 79 CCA CCA GGT CCC GGG GGC CG (1143-1162) ++ 40

Eph B4 78 GGG TCA AAA GTC AGG TCT CC (1123-1142) ++++ 70

Eph B4 77 CCC GCA GGG CGC ACA GGA GC (1103-1122) +++ 60

Eph B4 76 CTC CGG GTC GGC ACT CCC GG (1083-1102) +++ 60

Eph B4 75 CAG CGG AGG GCG TAG GTG AG (1063-1082) ++ 40

Eph B4 74 GTC CTC TCG GCC ACC AGA CT (1043-1062) ++ 50

Eph B4 73 CCA GGG GGG CAC TCC ATT CC (1023-1042) ++ 50

Eph B4 72 AGG TGC AGG GAG GAG CCG TT (1003-1022) ++++ 70

Eph B4 71 CAG GCG GGA AAC CAC GCT CC (983-1002) ++ 40

Eph B4 70 GCG GAG CCG AAG GAG GGG TG (963-982) +++ 50

Eph B4 69 GTG CAG GGT GCA CCC CGG GG (943-962) +++ 50

Eph B4 68 GTC TGT GCG TGC CCG GAA GT (923-942) ++ 40

Eph B4 67 ACC CGA CGC GGC ACT GGC AG (903-922) ++ 40

Eph B4 66 ACG GCT GAT CCA ATG GTG TT (883-902) ++ 50

Eph B4 65 AGA GTG GCT ATT GGC TGG GC (863-882 ( ++++ 60

Eph B4 64 ATG GCT GGC AGG ACC CTT CT (843-862) ++++ 80

Eph B4 63 CCT GAC AGG GGC TTG AAG GT (823-842) ++++ 80

Eph B4 62 GCC CTG GGC ACA GGC TCG GC (803-822) +++ 70

Eph B4 61 ACT TGG TGT TCC CCT CAG CT (783-802) ++++ 80

Eph B4 60 GCC TCG AAC CCC GGA GCA CA (763-782) +++ 50

Eph B4 59 GCT GCA GCC CGT GAC CGG CT (743-762) +++ 50

Eph B4 58 GTT CGG CCC ACT GGC CAT CC (723-742) ++ 45

Eph B4 57 TCA CGG CAG TAG AGG CTG GG (703-722) +++ 70

Eph B4 56 GCT GGG GCC AGG GGC GGG GA (683-702) ++ 50

Eph B4 55 CGG CAT CCA CCA CGC AGC TA (663-682) ++ 50

Eph B4 54 CCG GCC ACG GGC ACA ACC AG (643-662) ++ 50

Eph B4 53 CTC CCG AGG CAC AGT CTC CG (623-642) +++ 50

Eph B4 52 GGA ATC GAG TCA GGT TCA CA (603-622) ++++ 90

Eph B4 51 GTC AGC TGG GCG CAC TTT TT (583-602) +++ 70

Eph B4 50 GTA GAA GAG GTG CAG GGA TA (563-582) ++++ 80

Eph B4 49 GCA GGG CCA TGC AGG CAC CC (543-562) ++++ 80

Eph B4 48 TGG TCC TGG AAG GCC AGG TA (523-542) ++++ 90

Eph B4 47 GAA GCC AGC CTT GCT GAG CG (503-522) ++++ 80

Eph B4 46 GTC CCA GAC GCA GCG TCT TG (483-502) ++ 40 Eph B4 45 ACA TTC ACC TTC CCG GTG GC (463-482) +++ 50

Eph B4 44 CTC GGC CCC AGG GCG CTT CC (443-462) ++ 50

Eph B4 43 GGG TGA GAT GCT CCG CGG CC (423-442) +++ 60

Eph B4 42 ACC GTG TCC ACC TTG ATG TA (403-422) ++++ 80

Eph B4 41 GGG GTT CTC CAT CCA GGC TG (383-402) ++++ 80

Eph B4 40 GCG TGA GGG CCG TGG CCG TG (363-382) ++ 50

Eph B4 39 TCC GCA TCG CTC TCA TAG TA (343-362) +++ 60

Eph B4 38 GAA GAC GGT GAA GGT CTC CT (323-342) ++++ 80

Eph B4 37 TGC AGG AGC GCC CAG CCC GA (303-322) +++ 50

Eph B4 36 GGC AGG GAC AGG CAC TCG AG (283-302) +++ 45

Eph B4 35 CAT GGT GAA GCG CAG CGT GG (263-282) ++ 50

Eph B4 34 CGT ACA CGT GGA CGG CGC CC (243-262) ++ 40

Eph B4 33 CGC CGT GGG ACC CAA CCT GT (223-242) +++ 60

Eph B4 32 GCG AAG CCA GTG GGC CTG GC (203-222) ++++ 70

Eph B4 31 CCG GGG CAC GCT GCA CGT CA (183-202) +++ 60

Eph B4 30 CAC ACT TCG TAG GTG CGC AC (163-182) +++ 70

Eph B4 29 GCT GTG CTG TTC CTC ATC CA (143-162) ++++ 80

Eph B4 28 GGC CGC TCA GTT CCT CCC AC (123-142) ++ 40

Eph B4 27 TGC CCG TCC ACC TGA GGG AA (103-122) ++ 50

Eph B4 26 TGT CAC CCA CTT CAG ATC AG (83-102) ++++ 70

Eph B4 25 CAG TTT CCA ATT TTG TGT TC (63-82) ++++ 70

Eph B4 24 AGC AGG GTC TCT TCC AAA GC (43-62) ++++ 80

Eph B4 23 TGC GGC CAA CGA AGC CCA GC (23-42) ++ 50

Eph B4 22 AGA GCA GCA CCC GGA GCT CC (3-22) +++ 50

Eph B4 21 AGC AGC ACC CGG AGC TCC AT (1-20) +++ 50

Adciitional antisense probes desc]ribed in the specification

EphB4 AS-1 GTG CAG GGA TAG CAG GGC CAT (552-572)

EphB4 AS-2 AAG GAG GGG TGG TGC ACG GTG (952-972)

EphB4 AS-3 TTC CAG GTG CAG GGA GGA GCC (1007-1027)

EphB4 AS-4 GTG GTG ACA TTG ACA GGC TCA (1263-1285)

EphB4 AS-5 TCT GGC TGT GAT GTT CCT GGC (1555-1575)

EphB4 AS-6 GCC GCT CAG TC CTC CCA (123-140)

EphB4 AS-7 TGA AGG TCT CCT TGC AGG (316-333)

EphB4 AS-8 CGC GGC CAC CGT GTC CAC CTT (408-428)

EphB4 AS-9 CTT CAG GGT CTT GAT TGC CAC (1929-1949)

EphB4 AS-10 ATG GAG GCC TCG CTC AGA AA (1980-1999)

Ephb4 AS- 11 CAT GCC CAC GAG CTG GAT GAC (2138-2158)

Table 7. Inhibition of EphB4 Gene Expression by EphB4 RNAi probes

RNAi EphB4 RNAi sequence Inhibition Percent of EphB4 reduction Expression in viability

1 446 aaattggaaactgctgatctg 466

2 447 aattggaaactgctgatctga 467 +++ 70

3 453 aaactgctgatctgaagtggg 473 ++++ 70

4 454 aactgctgatctgaagtgggt 474 +++ 80

5 854 aatgtcaagacgctgcgtctg 874 +++ 65

6 467 aagtgggtgacattccctcag 487 + 35

7 848 aaggtgaatgtcaagacgctg 868 ++ 50 698 aaggagaccttcaccgtcttc 718 +++ 75

959 aaaaagtgcgcccagctgact 979 + 40

1247 aatagccactctaacaccatt 1267 ++ 50

1259 aacaccattggatcagccgtc 1279 ++ 50

1652 aatgtcaccactgaccgagag 1672 + 35

1784 aaataccatgagaagggcgcc 1804 +++ 65

1832 aagacgtcagaaaaccgggca 1852 + 30

1938 aacatcacagccagacccaac 19 ++ 50

2069 aagcagagcaatgggagagaa 2089 ++++ 75

2078 aatgggagagaagcagaatat 2098 +++ 65

2088 aagcagaatattcggacaaac 2108 +++ 70

2094 aatattcggacaaacacggac 2114 ++ 40

2105 aaacacggacagtatctcatc 2125 ++ 50

2106 aacacggacagtatctcatcg 2126 + 35

2197 aaaagagatcgatgtctccta 2217 +++ 65

2174 aatgaggctgtgagggaattt 2194 ++ 50

2166 aagaccctaatgaggctgtga 2186 ++ 50

2198 aaagagatcgatgtctcctac 2218 +++ 55

2199 aagagatcgatgtctcctacg 2219 +++ 70

2229 aagaggtgattggtgcaggtg 2249 + 33

2222 aagattgaagaggtgattggt 2242 + 30

2429 aacagcatgcccgtcatgatt 2449 ++ 40

2291 aagaaggagagctgtgtggca 2311 +++ 50

2294 aaggagagctgtgtggcaatc 2314 +++ 60

2311 aatcaagaccctgaagggtgg 2331 +++ 70

2497 aaacgacggacagttcacagt 2517 + 35

2498 aacgacggacagttcacagtc 2518 + 40

2609 aacatcctagtcaacagcaac 2629 ++ 50

2621 aacagcaacctcgtctgcaaa 2641 + 35

2678 aactcttccgatcccacctac 2698 ++ 50

2640 aagtgtctgactttggccttt 2660 +++ 70

2627 aacctcgtctgcaaagtgtct 2647 ++ 50

2639 aaagtgtctgactttggcctt 2659 + 25

2852 aatcaggacgtgatcaatgcc 2872 +++ 75

2716 aaagattcccatccgatggac 2736 ++ 50

2717 aagattcccatccgatggact 2737 ++ 60

2762 aagttcacttccgccagtgat 2782 +++ 70

3142 aagatacgaagaaagtttcgc 3162 ++ 50

3136 aatgggaagatacgaagaaag 3156 +++ 66

2867 aatgccattgaacaggactac 2887

3029 aaaatcgtggcccgggagaat 3049 + 33

3254 aaaatcttggccagtgtccag 3274 ++ 50

Example 9. Inhibition of Eplirin B2 Gene Expression by Ephrin B2 antisense probes and RNAi probes

KS SLK, a cell line expressing endogenous high level of ephrin B2. Cell viability was tested using fixed dose of each oligonuceotide (5UM). Gene expression downregulation was done using cell line 293 engineered to stably express full-length ephrin B2. KS SLK expressing EphrinB2 were also used to test the viability in response to RNAi probes tested at the fixed dose of 50 nM. Protein expression levels were measured using 293 cells stably expressing full-length EphrinB2, in cell lysates after 24 hr treatment with fixed 50 nM of RNAi probes.

The results on Ephrin B2 antisense probes were summarized below in Table 8. The results on Ephrin B2 RNAi probes were summarized below in Table 9.

Table 8. Ephrin B2 antisense ODNs. sequence Coding Percent Inhibition region reduction in of Ephrin B2 viability Expression

Ephrin AS- TCA GAC CTT GTA GTA AAT GT (983-1002) 35 ++ 51

Ephrin AS- TCG CCG GGC TCT GCG GGG GC (963-982) 50 +++ 50

Ephrin AS- ATC TCC TGG ACG ATG TAC AC (943-962) 45 ++ 49

Ephrin AS- CGG GTG CCC GTA GTC ccc GC (923-942) 35 ++ 48

Ephrin AS- TGA CCT TCT CGT AGT GAG GG (903-922) 40 +++ 47

Ephrin AS- CAG AAG ACG CTG TCC GCA GT (883-902) 40 ++ 46

Ephrin AS- CCT TAG CGG GAT GAT AAT GT (863-882) 35 ++ 45

Ephrin AS- CAC TGG GCT CTG AGC CGT TG (843-862) 60 +++ 44

Ephrin AS- TTG TTG CCG CTG CGC TTG GG (823-842) 40 ++ 43

Ephrin AS- TGT GGC CAG TGT GCT GAG CG (803-822) 40 ++

9

Ephrin AS- GTC CTT GTC CAG GTA GAA AT (123-142) 60 +++ 8

Ephrin AS- TTG GAG TTC GAG GAA TTC CA (103-122) 80 ++++ 7

Ephrin AS- ATA GAT AGG CTC TAA AAC TA (83-102) 70 +++ 6

Ephrin AS- TCG ATT TGG AAA TCG CAG TT (63-82) 50 +++ 5

Ephrin AS- CTG CAT AAA ACC ATC AAA AC (43-62) 80 ++++ 4

Ephrin AS- ACC CCA GCA GTA CTT CCA CA (23-42) 85 ++++ 3

Ephrin AS- CGG AGT CCC TTC TCA CAG CC (3-22) 70 +++ 2

Ephrin AS- GAG TCC CTT CTC ACA GCC AT (1-20) 80 ++++ 1

Table 9. Ephrin B2 RNAi probes.

Example 10. EphB4 antibodies inhibit tumor growth

Figure 57 shows results on comparison of EplιB4 monoclonal antibodies by G250 and in Pull-down assay.

Figure 58 shows that EphB4 antibodies, in the presence of matrigel and growth factors, inhibit the in vivo tumor growth of SCC 15 cells.

BalbC nude mice were injected subcutaneously with 2.5 x 10⁶ viable tumor cells SCC 15 is a head and neck squamous cell carcinoma line. Tumors were initiated in nu/nu mice by injecting 2.5-5xl0⁶ cells premixed with matrigel and Growth factors, and Ab's subcutaneously to initiate tumor xenografts. Mice were opened 14 days after injections. SCC 15 is a head and neck squamous cell carcinoma line, B16 is a melanoma cell line, and MCF-7 is a breast carcinoma line. The responses of tumors to these treatments were compared to control treated mice, which receive PBS injections. Animals were observed daily for tumor growth and subcutaneous tumors were measured using a caliper every 2 days. Antibodies #1 and #23 showed significant regression of SCC 15 tumor size compared to control, especially with no additional growth factor added.

Figure 59 shows that EphB4 antibodies cause apoptosis, necrosis and decreased angiogenesis in SCC 15, head and neck carcinoma tumor type.

Angiogenesis was assessed by CD-31 immunohistochemistry. Tumor tissue sections from freated and untreated mice were stained for CD31. Apoptosis was assessed by immunohistochemical TUNNEL, and proliferation by BrdU assay. Following surgical removal, tumors were immediately sliced into 2 mm serial sections and embedded in paraffin using standard procedures. Paraffin embedded tissue were sectioned at 5 μm, the wax removed and the tissue rehydrated. The rehydrated tissues were microwave inadiated in antigen retreival solution. . Slides were rinsed in PBS, and TUNNEL reaction mixture (Terminal deoxynucleotidyl fransferase and flourescein labeled nucleotide solution), and BrdU were added in a humidity chamber completely shielded from light. The TUNNEL and BrdU reaction mixture were then removed, slides were rinsed and anti-flourescein antibody conjugated with horseradish peroxidase was added. After incubation and rinsing, 3,

3'diaminobenzidine was added. Masson's Trichrome and Hematoxylin and Eosin were also used to stain the slides to visualize morphology. Masson's Trichrome allows to visualize necrosis and fibrosis. The tumor gets blood support from tumor/skin, muscle boundary. As tumor grows, inner regions get depleted of nutrients. This leads to necrosis (cell death), preferably at the tumor center. After cells die, (tumor) tissue gets replaced with fibroblastic tissue. Slides were visualized under 20-fold magnification with digital images acquired. A different morphology was obtained on SCC tumors with each antibody administered. Ab #1 showed an increase in necrosis and fibrosis but not apoptosis. Ab #23 showed an increase in apoptosis, necrosis and fibrosis and a decrease in vessel infiltration. Ab #35 showed an increase in necrosis and fibrosis, and a small increase in apoptosis and a decrease in vessel infiltration. Ab #79 showed a large increase in apoptosis, and necrossis and fibrosis. Ab #91 showed no change in apoptosis but an increase in proliferation. And Ab #138 showed an increase in apoptosis, necrosis, fibrosis and a decrease in proliferation and vessel infiltration. Tumors treated with control PBS displayed abundant tumor density and a robust angiogenic response. Tumors treated with EphB4 antibodies displayed a decrease in tumor cell density and a marked inhibition of tumor angiogenesis in regions with viable tumor cells, as well as tumor necrosis and apoptosis. Figure 60 shows that systemic administration of antibodies on xenografts leads to tumor regression in SCC15 tumor xenografts.

Alternate day treatment with EphB4 monoclonal antibody or an equal volume of PBS as control were initiated on day 4, after the tumors have established, and continued for 14 days. Systemic administration was administered either IP or SC with no significant difference. All the experiments were carried out in a double-blind manner to eliminate investigator bias. Mice were sacrificed at the conclusion ofthe two week treatment period. Tumors were harvested immediately postmortem and fixed and processed for immunohistochemistry. EphB4 antibodies 40 mg per kg body weight were administered. Treatment with EphB4 antibody significantly inhibited human SCC tumor growth compared with control-treated mice (p<0.05). Treatment with EphB4 antibody significantly inhibited tumor weight compared with control-treated mice (p<0.05).

INCORPORATION BY REFERENCE

All publications and patents mentioned herein are hereby incorporated by reference in their entirety as if each individual publication or patent was specifically and individually indicated to be incorporated by reference.

While specific embodiments ofthe subject invention have been discussed, the above specification is illustrative and not restrictive. Many variations ofthe invention will become apparent to those skilled in the art upon review of this specification and the claims below. The full scope ofthe invention should be determined by reference to the claims, along with their full scope of equivalents, and the specification, along with such variations.

Claims

WE CLAM:

I . An isolated soluble polypeptide comprising an amino acid sequence of an extracellular domain of an EphB4 protein, wherein the EphB4 polypeptide is a monomer and binds specifically to an Ephrin B2 polypeptide. 2. The soluble polypeptide of claim 1, comprising a globular domain of an EphB4 protein.

3. The soluble polypeptide of claim 1, comprising a sequence at least 90% identical to residues 1-522 ofthe amino acid sequence defined by Figure 65.

4. The soluble polypeptide of claim 1, comprising a sequence at least 90% identical to residues 1-412 ofthe amino acid sequence defined by Figure 65.

5. The soluble polypeptide of claim 1, comprising a sequence at least 90% identical to residues 1-312 ofthe amino acid sequence defined by Figure 65.

6. The soluble polypeptide of claim 1, comprising a sequence defined by Figure 1 or 2.

7. The soluble polypeptide of claim 1, wherein the soluble polypeptide inhibits the interaction between Ephrin B2 and EphB4.

8. The soluble polypeptide of claim 1, wherein the soluble polypeptide inhibits clustering ofEphrin B2 or EphB4.

9. The soluble polypeptide of claim 1, wherein the soluble polypeptide inhibits phosphorylation of Ephrin B2 or EphB4. 10. The soluble polypeptide of claim 1, wherein the soluble polypeptide is a fusion protein.

I I . The soluble polypeptide of claim 1 , wherein the soluble polypeptide comprises one or more modified amino acid residues.

12. An isolated soluble polypeptide comprising an amino acid sequence of an extracellular domain of an Ephrin B2 protein, wherein the soluble Ephrin B2 polypeptide is a monomer and binds with high affinity to an EphB4 polypeptide.

13. The soluble polypeptide of claim 12, comprising residues 1-225 ofthe amino acid sequence defined by Figure 66.

14. The soluble polypeptide of claim 12, comprising a sequence defined by Figure 3. 15. The soluble polypeptide of claim 12, wherein the soluble polypeptide inhibits the interaction between Ephrin B2 and EphB4.

16. The soluble polypeptide of claim 12, wherein the soluble polypeptide inhibits clustering of Eplirin B2 or EphB4.

17. The soluble polypeptide of claim 12, wherein the soluble polypeptide inhibits phosphorylation of Ephrin B2 or EphB4.

18. The soluble polypeptide of claim 12, wherein the soluble polypeptide is a fusion protein. 19. The soluble polypeptide of claim 12, wherein the soluble polypeptide comprises one or more modified amino acid residues.

20. A pharmaceutical composition comprising the soluble polypeptide of claim 1, and a pharmaceutically acceptable carrier.

21. A pharmaceutical composition comprising the soluble polypeptide of claim 12, and a pharmaceutically acceptable canier.

22. A cosmetic composition comprising the soluble polypeptide of claim 1, and a pharmaceutically acceptable carrier.

23. A cosmetic composition comprising the soluble polypeptide of claim 12, and a pharmaceutically acceptable canier. 23. A diagnostic kit comprising the soluble polypeptide of claim 1 and a phannaceutically acceptable canier.

24. A diagnostic kit comprising the soluble polypeptide of claim 12 and a canier.

25. An antagonist antibody selected from the group consisting of:

(a) an antibody which binds to an extracellular domain of an EphB4 protein and inhibits an activity ofthe EphB4; and

(b) an antibody which binds to an extracellular domain of an Ephrin B2 protein and inhibits an activity ofthe Ephrin B2.

26. The antagonist antibody of claim 25, wherein the antagonist antibody inhibits the interaction between Ephrin B2 and EphB4. 27. The antagonist antibody of claim 25, wherein the antagonist antibody inhibits clustering of Ephrin B2 or EphB4.

28. The antagonist antibody of claim 25, wherein the antagonist antibody inhibits phosphorylation of Ephrin B2 or EphB4.

29. The antagonist antibody of claim 25, wherein the antagonist antibody is a monoclonal antibody.

30. The antagonist antibody of claim25, wherein the antagonist antibody is a polyclonal antibody.

31. A pharmaceutical composition comprising the antagonist antibody of claim 25, and a pharmaceutically acceptable carrier.

32. A cosmetic compostion comprising the antagonist antibody of claim 25, and a pharmaceutically acceptable carrier. 33. A diagnostic kit comprising the antagonist antibody of claim 25, and a canier.

34. A method of inhibiting signaling through Ephrin B2/EphB4 pathway in a cell, comprising contacting the cell with an effective amount of a soluble polypeptide of claim 1.

35. A method of inhibiting signaling through Ephrin B2/EphB4 pathway in a cell, comprising contacting the cell with an effective amount of a soluble polypeptide of claim 12.

36. A method of inhibiting signaling through Ephrin B2/EphB4 pathway in a cell, comprising contacting the cell with an effective amount of a soluble polypeptide of claim 25. 37. A method of reducing the growth rate of a tumor, comprising administering an amount of a polypeptide agent sufficient to reduce the growth rate ofthe tumor, wherein the polypeptide agent is selected from the group consisting of:

(a) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an EphB4 protein, wherein the EphB4 polypeptide is a monomer and binds specifically to an Ephrin B2 polypeptide;

(b) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an Ephrin B2 protein, wherein the soluble Ephrin B2 polypeptide is a monomer and binds with high affinity to an EphB4 polypeptide.

(c) an antibody which binds to an extracellular domain of an EphB4 protein and inhibits an activity ofthe EphB4; and

(d) an antibody which binds to an extracellular domain of an Ephrin B2 protein and inhibits an activity ofthe Ephrin B2.

38. The method of claim 37, wherein the tumor comprises cells expressing a higher level of EphB4 and/or EphrinB2 than noncancerous cells of a comparable tissue. 39. A method for treating a patient suffering from a cancer, comprising administering to the patient a polypeptide agent selected from the group consisting of:

(a) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an EphB4 protein, wherein the EphB4 polypeptide is a monomer and binds specifically to an Ephrin B2 polypeptide; (b) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an Ephrin B2 protein, wherein the soluble Ephrin B2 polypeptide is a monomer and binds with high affinity to an EphB4 polypeptide.

40. The method of claim 39, wherein the cancer comprises cancer cells expressing EpbrinB2 and/or EphB4 at a higher level than noncancerous cells of a comparable tissue.

41. The method of claim 39, wherein the cancer is metastatic cancer.

42. The method of claim 39, wherein the tumor is selected from the group consisting of colon carcinoma, breast tumor, mesothelioma, prostate tumor, squamous cell carcinoma, Kaposi sarcoma, and leukemia. 43. The method of claim 39, wherein the cancer is an angiogenesis-dependent cancer.

44. The method of claim 39, wherein the cancer is an angiogenesis-independent cancer.

45. The method of claim 39, wherein the polypeptide agent inhibits the interaction between Ephrin B2 and EphB4.

46. The method of claim 39, wherein the polypeptide agent inhibits clustering of Ephrin B2 or EphB4.

47. The method of claim 39, wherein the polypeptide agent inhibits phosphorylation of Ephrin B2 or EphB4.

48. The method of claim 39, wherein the polypeptide agent is formulated with a pharmaceutically acceptable canier. 49. The method of claim 39, further including administering at least one additional anti- cancer chemotherapeutic agent that inhibits cancer cells in an additive or synergistic manner with the polypeptide agent.

50. A method of inhibiting angiogenesis, comprising contacting a cell an amount of a polypeptide agent sufficient to inhibit angiogenesis, wherein the polypeptide agent is selected from the group consisting of:

51. The method of claim 50, wherein the cell expresses EphB4 or Ephrin B2.

52. A method for treating a patient suffering from an angiogenesis-associated disease, comprising administering to the patient a polypeptide agent selected from the group consisting of:

(c) an antibody which binds to an extracellular domain of an EphB4 protein and inhibits an activity ofthe EphB4; and (d) an antibody which binds to an extracellular domain of an Ephrin B2 protein and inhibits an activity ofthe Ephrin B2.

53. The method of claim 52, wherein the soluble polypeptide is formulated with a pharmaceutically acceptable carrier.

54. The method of claim 52, wherein the angiogenesis-associated disease is selected from the group consisting of angiogenesis-dependent cancer, benign tumors, inflammatory disorders, chronic articular rheumatism and psoriasis, ocular angiogenic diseases, Osier- Webber Syndrome, myocardial angiogenesis, plaque neovascularization, telangiectasia, hemophiliac joints, angiofibroma, wound granulation, wound healing, telangiectasia psoriasis scleroderma, pyogenic granuloma, cororany collaterals, ischemic limb angiogenesis, rubeosis, arthritis, diabetic neovascularization, fractures, vasculogenesis, and hematopoiesis.

55. The method of claim 52, further including administering at least one additional anti- angiogenesis agent that inhibits angiogenesis in an additive or synergistic manner with the soluble polypeptide.

56. Use of a polypeptide agent in the manufacture of medicament for the treatment of cancer, wherein the polypeptide agent is selected from the group consisting of:

(b) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an Eplirin B2 protein, wherein the soluble Ephrin B2 polypeptide is a monomer and binds with high affinity to an EphB4 polypeptide.

57. Use of a polypeptide agent in the manufacture of medicament for the freatment of an angiogenesis-associated disease, wherein the polypeptide agent is selected from the group consisting of:

58. A method for treating a patient suffering from a cancer, comprising:

(a) identifying in the patient a tumor having a plurality of cancer cells that express EphB4 and/or EphrinB2; and

(b) administering to the patient a polypeptide agent selected from the group consisting of:

(i) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an EphB4 protein, wherein the EphB4 polypeptide is a monomer and binds specifically to an Ephrin B2 polypeptide; (ii) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an Ephrin B2 protein, wherein the soluble Ephrin B2 polypeptide is a monomer and binds with high affinity to an EphB4 polypeptide.

(iii) an antibody which binds to an extracellular domain of an EphB4 protein and inhibits an activity of the EphB4; and

(iv) an antibody which binds to an extracellular domain of an Ephrin B2 protein and inhibits an activity ofthe Ephrin B2.

59. A method for treating a patient suffering from a cancer, comprising:

(a) identifying in the patient a tumor having a plurality of cancer cells having a gene amplification ofthe EphB4 and/or EphriιιB2 gene; and

(i) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an EphB4 protein, wherein the EphB4 polypeptide is a monomer and binds specifically to an Ephrin B2 polypeptide;

(ii) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an Ephrin B2 protein, wherein the soluble Ephrin B2 polypeptide is a monomer and binds with high affinity to an EphB4 polypeptide.

(iii) an antibody which binds to an extracellular domain of an EphB4 protein and inhibits an activity ofthe EphB4; and

(iv) an antibody which binds to an extracellular domain of an Ephrin B2 protein and inhibits an activity ofthe Eplirin B2.

60. A method for identifying a tumor that is suitable for treatment with an EphrinB2 or EphB4 antagonist, the method comprising detecting in the tumor cell one or more of the following characteristics:

(a) expression of EphB4 protein and/or mRNA;

(b) expression of EphrinB2 protein and/or mRNA;

(c) gene amplification ofthe EphB4 gene; and

(d) gene amplification ofthe EphrinB2 gene, wherein a tumor cell having one or more of characteristics (a)-(d) is suitable for treatment with an EphrinB2 or EphB4 antagonist.

61. The method of claim 60, wherein the EphrinB2 or EphB4 antagonist is selected from the group consisting of: (a) a soluble polypeptide comprising an amino acid sequence of an extracellular domain of an EphB4 protein, wherein the EphB4 polypeptide is a monomer and binds specifically to an Ephrin B2 polypeptide;