INTERLEUKIN-6 AND TNF-ALPHA PRODUCTION IN HUMAN RENAL-CELL CARCINOMA

Several clinical and biological features suggest that cytokines implicated in the inflammatory response are produced by renal cell carcinoma (RCC). To define if alterations of tumor necrosis factor alpha (TNFalpha), interleukin 1 alpha (IL-1alpha), IL-1beta and IL-6 gene expression are present in this malignancy, samples from 19 tumors as well as samples from seven paired normal renal tissue were examined using Northern blot and immunohistochemical analysis. In addition, the expression of these cytokines was evaluated in seven RCC-derived cell cultures using Northern blot or RT-PCR. TNFalpha and IL-6 proteins were measured in culture supernatants using specific bio- and immunoassays. Consistent levels of IL-6 mRNA were detected in 17 of the 19 tested tumors whereas TNFalpha specific transcripts were present in seven of eight available RNA samples. TNFalpha and IL-6 mRNA were also detected in five of the seven paired normal kidneys. By immunolabeling, IL-6 antigen was not detected in RCC cells in any of the 19 studied samples. In contrast, using anti-TNFalpha antibody a strong labeling of stromal endothelia and macrophage cells was detected in all the 19 cases, and evident TNFalpha staining of the carcinoma cells themselves was observed in eight cases. Spontaneous IL-6 mRNA expression was detected in five RCC cel- cultures and TNFalpha mRNA in four. The cultured cells exhibited positive TNFalpha immunolabeling in six of seven cases but were always IL,6 negative. Bioactive IL-6 was detected in all culture supernatants while bioactive TNFalpha was not detected. However, immunoreactive TNFalpha protein was measured in two of three supernatants tested. Altogether these data indicate that RCC cells produce TNFalpha and IL-6 in vivo and in vitro at the RNA and protein level.