Hyperactivated NF-κB and AP-1 Transcription Factors Promote Highly Accessible Chromatin and Constitutive Transcription across the Interleukin-6 Gene Promoter in Metastatic Breast Cancer Cells

Abstract

Interleukin-6 (IL-6), involved in cancer-related inflammation, acts as an autocrine and paracrine growth factor, which promotes angiogenesis, metastasis, and subversion of immunity, and changes the response to hormones and to chemotherapeutics. We explored transcription mechanisms involved in differential IL-6 gene expression in breast cancer cells with different metastatic properties. In weakly metastatic MCF7 cells, histone H3 K9 methylation, HP1 binding, and weak recruitment of AP-1 Fra-1/c-Jun, NF-κB p65 transcription factors, and coactivators is indicative of low chromatin accessibility and gene transcription at the IL-6 gene promoter. In highly metastatic MDA-MB231 cells, strong DNase, MNase, and restriction enzyme accessibility, as well potent constitutive transcription of the IL-6 gene promoter, coincide with increased H3 S10 K14 phosphoacetylation and promoter enrichment of AP-1 Fra-1/c-Jun and NF-κB p65 transcription factors and MSK1, CBP/p300, Brg1, and Ezh2 cofactors. Complementation, silencing, and kinase inhibitor experiments further demonstrate involvement of AP-1 Fra-1/c-Jun and NF-κB p65/RelB members, but not of the alpha estrogen receptor in promoting chromatin accessibility and transcription across the IL-6 gene promoter in metastatic breast cancer cells. Finally, the natural withanolide Withaferin A was found to repress IL-6 gene transcription in metastatic breast cancer cells upon dual inhibition of NF-κB and AP-1 Fra-1 transcription factors and silencing of IL-6 promoter chromatin accessibility.

ACKNOWLEDGMENTS

We thank K. Anasinska, V. Quivy, J. Claes, and P. Faes for expertise and technical support and all lab members for suggestions and critical comments.

This work was supported by the IAP5/12 program (Brussels, Belgium). W.V.B. is a postdoctoral fellow with the FWO-Vlaanderen. Work in the C.V.L. lab was supported by grants from the Belgian Fund for Scientific Research (FRS-FNRS, Belgium), the Televie-Program of the FRS-FNRS, the Action de Recherche Concertée du Ministère de la Communauté Francaise (Université Libre de Bruxelles, ARC program no. 04/09-309), the Programme d'Excellence “Cibles” of the Region Wallonne, and the Internationale Brachet Stiftung. C.V.L. is Directeur de Recherches of the FRS-FNRS.