HUMAN MELANOCYTES AND MELANOMA-CELLS CONSTITUTIVELY EXPRESS THE BCL-2PROTOONCOGENE IN-SITU AND IN CELL-CULTURE

The Bcl-2 proto-oncogene regulates cell survival by antagonizing event s that lend to apoptotic cell death and has been reported to be expres sed in situ is lymphoid tissues, glandular epithelium, neurons, and ba sal epidermal cells, When we performed immunostaining on cryostat sect ions of normal skin, anti-Bcl-2 reactivity was confined to scattered d endritic cells is the basal epidermal layer Double-staining experiment s showed that the Bcl(-2+) cells were positive for vimentin bat negati ve for cytokeratins, CD1a, and CD45 antigens, excluding keratinocytes and Langerhans cells as possible candidates for constitutive Bcl-2 exp ression Bcl-2(+) epidermal cells also reacted with the monoclonal anti -melanocyte antibody NKl/beteb, and were absent from lesional skin in vitiligo, confirming that they represented epidermal melanocytes, West ern blot analysis of cultured melanocytes and melanoma cell lines reve aled a 26-kd protein specifically reacting with the anti-Bcl-2 monoclo nal antibody Immunostaining of pigmented lesions revealed strong expre ssion of Bcl-2 by five of five nevocellular nevi and seven of seven me lanomas. Our observations demonstrate that, within normal human epider mis, melanocytes are the only cells that express Bcl-2 constitutively and that Bcl-2 is expressed in benign and malignant pigmented tumors o f the skin in situ.