Immunophenotype of human melanoma cells in different metastases.

The pattern of melanoma-associated antigens (MAAs) expressed on the surface of melanoma cells in 23 metastases, 15 obtained from different patients and 8 from different metastases in two patients, was studied by immunoprecipitation and sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis using monoclonal and polyclonal melanoma antisera. Though there were differences in the MAAs expressed by each melanoma, there were marked similarities as well. No more than two melanomas had a similar pattern of MAAs. However, all melanomas expressed some MAAs, and most MAAs were commonly expressed by several melanomas. Two of the MAAs studied, with molecular weights of approximately 75,000 and 95,000 to 97,000, were particularly well represented, and at least one of these two antigens was expressed by all melanoma cells. These results suggest that complete absence of tumor-associated antigens on metastatic melanoma cells is a rare phenomenon. All melanoma lines we studied expressed at least one of a restricted number of antigens. Thus despite antigenic heterogeneity, sufficient similarity remains between different melanomas to permit specific immunotherapy to be targeted to a limited number of tumor antigens.