B7-H3L cell surface antigen and antibodies that bind thereto

1. A substantially purified immunoglobulin polypeptide or an antigen binding fragment thereof, that specifically binds to an epitope of a B7-H3L protein that is expressed and exposed in its native conformation on the surface of a living cancer cell in vitro or in vivo, wherein said epitope is insufficiently expressed on the surface of a living normal cell to exhibit binding by said purified immunoglobulin polypeptide, and wherein said purified immunoglobulin polypeptide or antigen binding fragment thereof can be internalized into said cancer cell expressing B7-H3L.

2. The purified immunoglobulin polypeptide or antigen binding fragment of claim 1 , wherein said cancer cell is selected from the group consisting of a cancer cell from: an adrenal gland tumor, an AIDS-associated cancer, an alveolar soft part sarcoma, an astrocytic tumor, a bladder cancer, a bone cancer, a brain or spinal cord cancer, a metastatic brain tumor, a breast cancer, a carotid body tumor, a cervical cancer, a chondrosarcoma, a chordoma, a chromophobe renal cell carcinoma, a clear cell carcinoma, a colon cancer, a colorectal cancer, a cutaneous benign fibrous histiocytoma, a desmoplastic small round cell tumor, an ependymoma, a Ewing's tumor, an extraskeletal myxoid chondrosarcoma, a fibrogenesis imperfecta ossium, a fibrous dysplasia of the bone, a gallbladder or bile duct cancer, a gestational trophoblastic disease, a germ cell tumor, a head and neck cancer, an islet cell tumor, a Kaposi's Sarcoma, a kidney cancer, a leukemia, a lipoma/benign lipomatous tumor, a liposarcoma/malignant lipomatous tumor, a liver cancer, a lymphoma, a lung cancer, a medulloblastoma, a melanoma, a meningioma, a multiple endocrine neoplasia, a multiple myeloma, a myelodysplastic syndrome cell, a neuroblastoma, a neuroendocrine tumor, an ovarian cancer, a pancreatic cancer, a papillary thyroid carcinoma, a parathyroid tumor, a pediatric cancer cell, a peripheral nerve sheath tumor, a phaeochromocytoma, a pituitary tumor, a prostate cancer, a posterious uveal melanoma, a rare hematologic disorder, a renal metastatic cancer, a rhabdoid tumor, a rhabdomysarcoma, a sarcoma, a skin cancer, a soft-tissue sarcoma a squamous cell cancer, a stomach cancer, a synovial sarcoma, a testicular cancer, a thymic carcinoma, a thymoma, a thyroid metastatic cancer, and a uterine cancer.

3. A pharmaceutical composition comprising the purified immunoglobulin polypeptide or antigen binding fragment of claim 1 , together with a pharmaceutically acceptable carrier.

4. A pharmaceutical composition comprising a monoclonal antibody or an antigen binding fragment thereof that specifically binds to an epitope of B7-H3L protein that is expressed and exposed in its native conformation on the surface of a living cancer cell in vitro or in vivo, wherein said epitope is insufficiently expressed on the surface of a living normal cell to exhibit binding by said antibody, and wherein said purified antibody or antigen binding fragment thereof can be internalized into said cancer cell expressing B7-H3L;

together with a pharmaceutically acceptable carrier.

5. The pharmaceutical composition of claim 4 , wherein the composition comprises an additional therapeutic moiety.

6. An isolated antibody comprising an antigen-binding fragment of the antibody expressed by the hybridoma having ATCC Deposit No. PTA-4217, ATCC Deposit No. PTA-4218, ATCC Deposit No. PTA-4244, or ATCC Deposit No. PTA-4245.

7. The purified immunoglobulin polypeptide or antigen binding fragment of claim 1 , wherein said purified immunoglobulin polypeptide or antigen binding fragment thereof exhibits the same binding specificity as the monoclonal antibody expressed by the hybridoma having ATCC Deposit No. PTA-4217, ATCC Deposit No. PTA-4218, ATCC Deposit No. PTA-4244, or ATCC Deposit No. PTA-4245.