Nuclear factor kB, nuclear factor interleukin-6 (NFIL6 or C/EBPbeta) and nuclear factor interleukin-6beta (NFIL6beta or C/EBPdelta) are not sufficient to activate the endogenous interleukin-6 gene in the human breast carcinoma cell line MCF-7. Comparative analysis with MDA-MB-231 cells, an interleukin-6 expressing human breast carcinoma cell line.

A comparative study of the molecular mechanism of interleukin-6 (IL-6) gene induction on two breast-carcinoma-derived cell lines has been performed. MDA-MB-231 cells produce constitutive detectable levels of both secreted LL-6 and mRNA which, as expected, are dramatically enhanced following induction by either IL-1β or tumor necrosis factor-α (TNF-α). The levels of both secreted IL-6 and IL-6 mRNA are significantly higher in response to IL-1β in spite of the fact that stimulation by TNF-α alone enhances the half life of IL-6 mRNA. The protein synthesis inhibitor cycloheximide is also a fairly strong inducer of IL-6 in these cells. In contrast, MCF-7 cells fail to produce detectable IL-6 protein or mRNA, even after stimulation with proper inducers. Analysis of transcription factors NF-κB, NFIL6 and NFIL6β, which have been described to be sufficient to activate the IL-6 gene in other cell systems, shows a similar pattern of expression in both MCF-7 and MDA-MB-231 cells. Furthermore, tran...