Cell Surface Antigens of Human Melanocytes and Melanoma

Clinical and histopathological observations suggest that the pathogenesis of cutaneous melanoma evolves through multiple stages . It has been proposed that early stages are characterized by benign proliferation of melanocytic cells and later stages by acquisition of competence for invasion and metastasis (1) . The recognition that dysplastic nevi are a class of pigmented lesions with potential for malignant change is consistent with the existence of a precursor step in the development of melanoma (2). Phenotypic markers that discriminate normal melanocytes from melanoma cells would be particularly useful for dissecting stages in melanocyte transformation . However, definitive criteria that distinguish benign melanocytes from premalignant and malignant cells have not been established . In previous studies, we have used morphology, pigmentation, and expression of cell surface and intracellular antigens to characterize the phenotype ofcultured human melanocytes and melanomas (3, 4) . Serological typing has revealed that antigens that are expressed on a subset of melanomas or melanocytes generally are regulated by the melanocyte differentiation program (3, 4) . During these investigations, an antigen system was recognized whose pattern of expression was remarkable because it was not associated with the stage of melanocyte differentiation, but appeared to be regulated with melanocyte transformation . This antigen system was expressed by all cultured melanocytes but not by melanomas. mAbs that react with this antigen bind to a 120AD cell surface glycoprotein that has been identified as the adenosine deaminase binding protein (ADAbp) (5). These studies indicate that cell surface expression of ADAbp is downregulated and apparently extinguished during the process of melanocyte transformation .