Enhanced expression of HLA-DR antigens by the human melanoma cell line CaCL 73-36 upon induction of a less differentiated phenotype with bromodeoxyuridine.

The effects of bromodeoxyuridine (BUdr) on the in vitro growth, morphology and expression of HLA-DR antigens in the human melanoma line CaCL 73-36 were studied. Treatment of melanoma cells with BUdr resulted in an inhibition of growth with 30-35% reduction in saturation density at 2 micrograms/ml and 50-54% reduction at 4 micrograms/ml. BUdr-treated melanoma cells showed marked morphological changes including more flattened and epithelial cell shapes. These changes are consistent to a less differentiated phenotype. Quantitative absorption analysis using an anti HLA-DR monoclonal antibody revealed that the expression of surface HLA-DR antigens was enhanced by up to 2.5-fold in a BUdr dose-dependent manner. This enhancement could be related to an increased synthesis of HLA-DR antigens rather than a decrease shedding of these antigens. Further studies are needed to fully elucidate the biological significance and mechanism of action of BUdr in causing such altered HLA-DR expression.