The renal cell carcinoma lysis by a specific cytotoxic T cell clone is independent of the Fas/Fas-L cytotoxic pathway

The expression of Fas antigen at the surface of renal cell carcinoma and the susceptibility to Fas-mediated lysis by a tumor specific CTL clone were investigated. Renal cell carcinoma cell lines expressed Fas antigen and were susceptible to apoptosis mediated by antibodies to Fas/APO1. Using RT-PCR, we further showed that these cell lines expressed mRNA for Fas deleted transmembrane region, corresponding to a soluble form of Fas/APO-1. To investigate the role of the Fas/FasL pathway in the cytotoxic response against RCC cells, we analyzed the induction of Fas-L on a tumor specific T cell clone (CTL 8C2), previously generated against one RCC cell line. Fas-L expression on CTL 8C2 was detected by RT-PCR after stimulation with autologous tumor cells. However, the cytotoxic activity of CTL 8C2 was completely abolished when EGTA was added, suggesting that the cytolysis was mainly mediated by a Ca++-dependent pathway, perforin/granzyme-based.