Interleukin-6 (IL-6) functions as an in vitro autocrine growth factor in renal cell carcinomas

Interleukin-6 (IL-6) was found to be a growth factor of renal cell carcinomas Furthermore, renal cell carcinomas freshly isolated from the patients expressed mRNA of IL-6 and secreted biologically active IL-6 under the culture conditions where the tumor cells could grow, but they did not produce IL-6 nor proliferate in the absence of fetal calf serum. The production of IL-6 by the tumor cells was also demonstrated by immunostaining of the IL-6-producing cells utilizing anti-IL-6 antiserum. Moreover, anti-IL-6 antiserum specifically inhibited the in vitro tumor growth. All data indicated that IL-6 functions as an in vitro autocrine growth factor of renal cell carcinomas.