Abstract LB-154: Epigenetic silencing of triple-negative breast cancer hallmarks by Withaferin A

Abstract

Abstract Background: Triple negative breast cancer (TNBC) is characterized by poor prognosis and a DNA hypomethylation profile. We found that the steroidal lactone Withaferin A (WA), isolated from the plant Withania somnifera, triggers active chromatin remodeling and elicits promising chemosensitizing effects in triple negative breast cancer (BC) cells. Here, we have further characterized potential involvement of epigenetic reprogramming by Withaferin A in TNBC treatment. Materials and methods: By Infinium HumanMethylation450 arrays, Epityper Mass array and CpG pyrosequencing, we determined genome-wide DNA methylation changes in weakly-metastatic and aggressive, metastatic BC cell lines treated with a pharmacologically relevant concentration of 700 nM WA. In parallel, we performed ChIP analysis of histone mark H3K4Me3 to evaluate histone demethylation by JARID1B/KDM5B. Furthermore, epigenetic changes in response to WA were crosscompared with genomewide methylation changes and clinical breast cancer patient characteristics in The Cancer Genome Atlas database. Results: In contrast to the DNA hypomethylating agent 5-aza-2’-deoxycytidine (DAC), WA treatment of TNBC cells silences an epigenetic cancer network through gene-specific hypermethylation of tumor promoting genes including ADAM metallopeptidase domain 8 (ADAM8), urokinase-type plasminogen activator (PLAU), tumor necrosis factor (ligand) superfamily, member 12 (TNFSF12), and genes related to detoxification (glutathione S-transferase mu 1, GSTM1), or mitochondrial metabolism (malic enzyme 3, ME3). Remarkably, DNA hypermethylation of corresponding CpG sites in these genes correlates with receptor tyrosine-protein kinase erbB-2 amplification (HER2)/estrogen receptor (ER)/progesterone receptor (PR) positive status in primary BC tumors. Increased expression levels of JARID1B, promoter-specific loss of active H3K4me3 chromatin marks and gain of DNA methylation suggest that WA-specific gene silencing involves epigenetic reprogramming of HER2/ER/PR-dependent gene expression programs to suppress aggressive TNBC characteristics in favor of luminal BC hallmarks with an improved therapeutic sensitivity. Conclusions: WA may represent a novel and attractive phytopharmaceutical to overcome therapy resistance in TNBC. Citation Format: Wim Vanden Berghe, Katarzyna Szarc vel Szic, Ken Declerck, René A.J. Crans, Jolien Diddens, Clarissa Gerhäuser. Epigenetic silencing of triple-negative breast cancer hallmarks by Withaferin A. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-154.