Acquisition of resistance to Fas-mediated apoptosis by overexpression of clusterin in human renal-cell carcinoma cells

Recent studies have shown the antiapoptotic activity of clusterin against a wide variety of stimuli; however, the functional role of clusterin in Fas- mediated apoptosis has not been well characterized. We transfected the clus terin cDNA into human renal-cell carcinoma (RCC) ACHN cells that scarcely e xpress clusterin protein in order to examine whether overexpression of clus terin inhibits the Fas-mediated signal pathway for apoptotic cell death. No significant difference was observed in the in vitro cell growth rates betw een the clusterin-transfected cell line (ACHN/CL) and the vector-only-trans fected control cell line (ACHN/C), whereas the colony-forming efficiency in soft agar of ACHN/CL was significantly higher than that of ACRAN/C. The an ti-Fas monoclonal antibody CH11 induced apoptosis in ACHAN/C cells in a dos e-dependent manner; however, the growth-inhibitory effect of CH11 on ACHN/C L cells was markedly suppressed, with corresponding increases in p53 expres sion and decrease in the fraction of cells in the sub-G, phase of the cell cycle. Furthermore, the cytotoxic effect of CH11 on ACHN/CL cells was augme nted by treatment with interferon-gamma, but a corresponding effect on ACHN /C cells was not observed. These findings suggest that overexpression of cl usterin may contribute to a phenotype resistant to Fas-mediated apoptosis, and that if interferon-gamma treatment is added according to the clusterin expression level, Fas-mediated therapy could be a novel approach to RCC.