Characterization of the antitumor activities of IFN-alpha8 on renal cell carcinoma cells in vitro.

Interferon-alpha (IFN-alpha) has a number of therapeutic applications in the treatment of various human cancers and diseases of viral origin. IFN-alpha includes several subtypes, and little has been reported on the biologic properties of the individual subtypes. Here, we report on the individual antitumor effects of five IFN-alpha subtypes, alpha1, alpha2, alpha5, alpha8, and alpha10, against six renal cell carcinoma (RCC) cell lines in vitro. Among the subtypes, IFN-alpha8 most potently inhibited cell proliferation and delayed the G(1)/S transition. Synergistic induction of apoptosis was shown in two of the RCC cell lines when treated with the combination of IFN-alpha and IFN-gamma rather than with either IFN-alpha or IFN-gamma alone. IFN-alpha8 was most effective in the induction of apoptosis when combined with IFN-gamma. In addition, IFN-alpha8 had the strongest ability to upregulate HLA class II antigen expression in the subtypes examined. These data indicate that subtypes of IFN-alpha have disparate antitumor effects in vitro, and in vitro distinctions among the IFN-alpha subtypes should be appreciated more in clinical application.