Syngeneic humoral immune responses to tumor-associated antigens expressed by K-1735 UV-induced melanoma and its metastases

An enzyme-linked immunoassay (ELISA) was developed to study syngeneic humoral immune response to a primary tumor and its metastases in the K-1735 ultraviolet light (UV)-induced C3H murine melanoma system. Binding of sera from syngeneic animals previously immunized with primary tumor or metastatic tumor tissue (M-3, M-4) to corresponding 3 M KCl extracts of tumor was significantly greater than binding of control C3H mouse serum. Antibody binding was not significantly reduced by competitive binding with syngeneic murine muscle or liver extracts, indicating the presence of tumor antigen(s) not shared by normal murine tissue. Antibodies to the tumor-associated antigens were selectively removed by competitive binding with syngeneic K-1735 tumor extracts but not by the unrelated 102 murine sarcoma from C57BL/6. However, EL-4 extracts (C57BL/6) did inhibit antibody binding to the primary and both metastases. Further competitive binding studies demonstrated the presence of a common antigen(s) present on the primary tumor and both metastases. We conclude that the K-1735 UV-induced melanoma primary tumor and its metastases express serologically detectable shared antigenic determinate.