Identification of melanoma cell surface antigens immunogenic in mice

Active immunization to B16 melanoma cells or vaccines induces anti-melanoma immune responses in syngeneic mice. The immunogenic antigens stimulating immunity to this tumor have not been identified. In this study we detected several B16 melanoma antigens immunogenic in syngeneic mice using as probes antimelanoma antibodies induced by immunization to B16 melanoma vaccines. These antigens were identified by SDS-PAGE and autoradiographic analysis of specific immunoprecipitates. They were cell-surface components with approximate molecular weights of 41, 46, 50, 75, 80, and 104 KD. All these antigens were expressed by syngeneic and xenogeneic melanomas and by some unrelated syngeneic tumors but not by normal syngeneic cells, xenogeneic melanocytes, or by B16 melanoma cells obtained from fresh tumors or grown in defined medium. The antigens were distinct from murine viral antigens expressed by B16 melanoma cells and from components of the culture medium used to grow cells for vaccine production. These results indicate that several B16 melanoma cell-surface antigens are immunogenic in syngeneic mice. Expression of these antigens appears to be related to malignant transformation as they were found on all melanomas studied, and some other cancers, but not on normal cells.