Anti-proliferative activity of natural interferon-alpha, isotretinoin and their combination varies in different human melanoma cell lines.

Natural interferon alpha (nIFN-alpha) isotretinoin and their combination were tested for their capacity to modulate the proliferation of different human melanoma cell lines. Modulation of cell growth was measured using the MTT-assay. Isotretinoin and nIFN-alpha as single agents inhibited the proliferation in a dose dependent manner in the three cell lines: SK-Mel-30, SK-Mel-28 and MaRi. The combination of isotretinoin and nIFN-alpha led to a marked enhancement of the antiproliferative effect compared with either nIFN-alpha or isotretinoin alone in SK-Mel-30 cells. In contrast, there were no additive effects on growth inhibition of melanoma cell lines SK-Mel-28 and MaRi when nIFN-alpha and isotretinoin was combined. In one melanoma cell line (MaRi) proliferation was actually enhanced by isotretinoin in combination with nIFN-alpha. These results demonstrate the heterogeneous response of human melanoma cell lines to noncytotoxic concentrations of isotretinoin and nIFN-alpha alone and in combination.