TRANSCRIPTION OF THE GENE ENCODING MELANOMA-ASSOCIATED ANTIGEN GP100 IN TISSUES AND CELL-LINES OTHER THAN THOSE OF THE MELANOCYTIC LINEAGE

The expression of the gp100 antigen is generally thought to be confine d to cells of the melanocytic lineage, which makes the protein a suita ble melanoma-specific marker. Strikingly, after screening a panel of n ormal tissues, tumour samples and cell lines of non-melanocytic origin , we found transcripts encoding gp100 in virtually every tissue and ce ll line tested. In contrast, tyrosinase and MART-1/MelanA transcripts were detected only in cells of the melanocytic lineage. However, no gp 100 protein could be detected by either Western blotting or cytotoxici ty assays. Therefore, at the protein level, gp100 remains exclusive fo r cells of melanocytic origin despite its transcription in many cell t ypes. The major implication of this finding is that screening of patie nt material for gp100 expression should preferrably be performed by an tibody staining. Reverse transcriptase polymerase chain reaction (RT-P CR) can be employed, provided that it is performed in a tightly contro lled, semiquantitative setting.