Identification of a secreted Mr 95,000 glycoprotein in human melanocytes and melanomas by a melanocyte specific monoclonal antibody.

We have isolated a monoclonal antibody, designated HMB-50, that is highly specific for melanomas and melanocyte derived lesions. The antibody recognizes melanomas, neonatal melanocytes, and junctional nevi but does not react with adult melanocytes, dermal nevi, or a variety of non-melanocyte derived neoplasms. In tissue culture, the antibody reacts with five of seven human melanoma lines and neonatal foreskin melanocytes but fails to recognize fibroblasts and a number of different carcinomas. HMB-50 identifies a Mr 95,000 glycoprotein that is released into the growth medium by melanoma cells and neonatal melanocytes in vitro. This molecule is unrelated to antigens recognized by a variety of antimelanoma monoclonal antibodies isolated in other laboratories. The Mr 95,000 glycoprotein has been purified by antibody affinity chromatography and a polyclonal rabbit antiserum raised that exhibits identical specificity to the monoclonal antibody. The Mr 95,000 glycoprotein is rapidly released by melanoma cells (within 60 min) and one line produces relatively large quantities of the molecule (1 microgram/10(6) cells/24 h). The molecule in normal melanocytes differs slightly in electrophoretic mobility compared to its counterpart in melanomas and this difference appears to result from posttranslational modification.