Cell binding and tumor inhibiting functions of a new antihuman melanoma murine monoclonal antibody.

Murine, antihuman melanoma cell monoclonal antibody (mAb) 16.C8 was generated by fusing the murine myeloma cell line P3X63/Ag8.653 with splenocytes from a nude mouse bearing a human melanoma xenograft, after reconstitution with splenocytes from syngeneic immunocompetent BALB/c mice. The antibody reacted strongly with fresh human melanoma cells and exhibited preferential reactivity with established human melanoma and neuroectodermal tumor cell lines. Electrophoresis and Western blotting experiments indicated that 16.C8 is directed against a sialoglycoprotein antigen with a molecular weight of 110-120 kDa. mAb 16.C8 mediated lysis of melanoma cells in vitro in antibody-dependent cellular cytotoxicity assays using human mononuclear effector cells isolated from normal volunteers or malignant melanoma patients. In addition, the administration of mAb 16.C8 to nude mice bearing established human melanoma lung and liver metastases resulted in significant inhibition of tumor growth as shown by gross and histologic examination. In contrast, animals treated with Hanks' balanced salt solution or nonspecific immunoglobulin exhibited a large tumor burden. These results suggest that mAb 16.C8 may be of value in treatment of metastatic melanoma in humans.