Are renal cell carcinoma cells able to modulate the cytotoxic effect of tumor infiltrating lymphocytes by secretion of interleukin-6?

Background: Interleukin(IL)-6 can suppress the cisplatin-induced induction of apoptosis in renal cell carcinoma (RCC) in vitro. Thera are reports on I L-6 secretion by tumor cells. Materials and Methods: In supematants of RCC cultures we measured IL-6 levels by a bioassay. In a videomicroscopic micro cytotoxicity assay the immunomodulating effect of secreted cytokines on the cytotoxicity of tumor infiltrating lymphocytes (TIL) was studied Results: The IL-6 concentrations in 17 supematants of healthy I renal cells tended t o be higher than in the supernatants of tumor cell cultures. By immunostain ing we detected IL-6 in 3/6 cell cultures fi om healthy renal tissue, in 12 /22 tumor. tissue samples, and in 8/18 tumor cultures respectively Supemata nts suppressing cytotoxic activity of TIL showed higher IL-6 concentrations in tendency. Suppression of cytotoxicity could also be induced by adding d iscrete concentrations of IL-6 Conclusions: IL6 secreted by tumor cells see ms to be tumor protecting against cytotoxic TIL. Blocking this mechanism co uld be an additional approach in immunotherapy of RCC.