Enhanced expression of melanoma-associated antigens and beta 2-microglobulin on cultured human melanoma cells by interferon.

The effect of human leukocyte interferon (IFN) on the in vitro growth and expression of melanoma-associated antigens (MAA). beta 2-microglobulin (beta 2m) and HLA-DR antigen on cultured human melanoma cells was studied. Exposure of melanoma cells to IFN for 64 hours resulted in a dose-dependent inhibition of growth with 46% reduction in cell number at 10(3) U IFN/ml and 74% reduction at 10(5) U/ml. Quantitative absorption experiments in the mixed hemadsorption assay determined that the expression of MAA and beta 2m on treated cells was enhanced at 10(2)-10(5) U IFN/ml, twofold to fivefold for MAA and fivefold to twelvefold for beta 2m. No change was seen in HLA-DR antigen expression. The IFN-induced enhancement of MAA and beta 2m could be detected as early as after 16 hours and a maximum expression was reached at 96 hours after IFN exposure. The IFN-induced enhancement of MAA and beta 2m on melanoma cells was reversible. Studies with melanoma cells grown in stationary phase and serum-deprived conditions indicated that IFN-induced augmentation of MAA and beta 2m did not require cell proliferation. The data suggest that the effect of IFN on antigen expression is independent of its effect on cell growth. Further studies are needed to fully elucidate the mechanism.