Nuclear factor kappa B (NF-kappa B), nuclear factor interleukin-6 (NFIL-6 or C/EBP beta) and nuclear factor interleukin-6 beta (NFIL6-beta or C/EBP delta) 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 IL-6 and mRNA which, as expected, are dramatically enhanced following induction by either IL-1 beta or tumor necrosis factor-alpha (TNF-alpha). The levels of both secreted IL-6 and IL-6 mRNA are significantly higher in response to IL-1 beta in spite of the fact that stimulation by TNF-alpha 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-kappa B, NFIL6 and NFIL6 beta, 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, transfection of a recombinant plasmid carrying the IL-6 promoter linked to a luciferase reporter gene shows that both cell lines are able to drive IL-1 beta or TNF-alpha activation of this construction in a very similar manner. Finally, when MCF-7 cells were treated with IL-1 beta or TNF-alpha in the presence of cycloheximide, transcription of IL-6 mRNA from the endogenous IL-6 gene was observed. These data suggest that a mechanism of IL-6 gene repression is active in MCF-7 cells.
Faggioli
L
L
Istituto di Chimica Biologica, Università di Verona, Italy.
Costanzo
C
C
Merola
M
M
Bianchini
E
E
Furia
A
A
Carsana
A
A
Palmieri
M
M
D001483:Base Sequence; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D051743:CCAAT-Enhancer-Binding Protein-delta; D022762:CCAAT-Enhancer-Binding Proteins; D002277:Carcinoma / Q000235:genetics* / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D016207:Cytokines / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics*; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D012334:RNA, Neoplasm / Q000096:biosynthesis; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D022762:CCAAT-Enhancer-Binding Proteins; C497252:CEBPD protein, human; D016207:Cytokines; D004268:DNA-Binding Proteins; D015850:Interleukin-6; D016328:NF-kappa B; D009687:Nuclear Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D014157:Transcription Factors; D051743:CCAAT-Enhancer-Binding Protein-delta; D003513:Cycloheximide