PCR-mediated differential display and cloning of a melanocyte gene decreased in malignant melanoma and up-regulated with sensitization to DNA damage.

Characterization of genes expressed in normal cells and decreased in their malignant counterparts is important for detecting candidate tumor suppressor genes. We have now used comparative differential display of MRNAs from B16 melanoma and matched syngeneic normal melanocytes to detect a G0A gene expressed preferentially in resting G0 melanocytes compared to proliferating cells. Cloning and sequencing revealed no homology of G0A in the GenBank Database, suggesting that this is a new gene. Northern blot analysis with the cloned probe, confirmed about a five-fold higher expression in normal melanocytes compared to melanoma. Up-regulation of this gene was not detected by L-tyrosine induction of B16 melanoma terminal differentiation, but was seen in these cells, when exposed to the radiation sensitizer bromodeoxyuridine and subsequent UV radiation. Our differential expression data suggest that the G0A gene is important for melanocytic growth control and for the response of melanoma cells to radiation sensitizers.