Surface Antigens of Melanomas and Melanocytes Defined by Mouse Monoclonal Antibodies: Specificity Analysis and Comparison of Antigen Expression in Cultured Cells and Tissues

Mouse monoclonal antibodies (mAb) detecting 13 distinct systems of surface antigens on cultured melanocytes and melanomas were tested for reactivity with panels of (a) normal and malignant cultured cells; (b) normal adult and fetal tissues; and (c) specimens of metastatic melanoma and other tumor types. The objectives of this study were to compare antigen expression in cultured versus noncultured cells, to develop a panel of mAbs that identify subsets of melanomas, and to provide requisite information about antibody specificity in preparation for the use of antibodies in the diagnosis, imaging, and therapy of melanoma. Five of the melanoma surface antigens have been well characterized biochemically, chondroitin sulfate proteoglycan, HLA Class II antigens, glycoprotein of molecular weight 130,000 (gp130), and glycoprotein M95,000/protein M97,000 (gp95/ p97)]. Three antigens have been related to melanocyte differentiation (HLA Class II, M111/M231, and M144), and six provide additional markers for subsets of cultured melanomas. mAb R reacts with the disialoganglioside G, a predominant ganglioside on cultured melanoma cells and other cells of neuroectodermal origin. A high proportion of melanoma, astrocytoma, and sarcoma tissue specimens were. in normal tissues, reactivity of mAb R was restricted to melanocytes, neuronal and glial cells in the central nervous system, parotid gland, adrenal medullary cells, and rare cells in the connective tissue. mAb B5 detects a chondroitin sulfate proteoglycan that is expressed by most melanoma and astrocytoma cell lines and by cultured melanocytes. Most of the melanoma and astrocytoma specimens were B5, whereas other tumor types tested were B5. mAb 13–17, which detects a monomorphic determinant of HLA Class II antigens, reacted with melanomas, and with a variety of other cancers, but not with normal skin melanocytes. There is considerable variability in the expression of and HLA Class II antigens in individual melanoma specimens; cotyping for these two antigens showed no evidence for coordinate expression. mAb L101 detects gp130 and mAb L235 detects gp95, antigens that are strongly expressed on a broad range of cultured cell types. in contrast to their wide distribution on cultured cells, gp130 expression in tissues was generally restricted to a subset of melanomas and some normal cells, and gp95 was detected.