Abstract 1385: Galangin is an epigenetic modulator or BRCA1 and induces estrogen receptor alpha in triple negative breast cancer cells

Abstract

Abstract The aryl hydrocarbon receptor (AhR) is a driver of breast cancer progression and its overexpression is often observed in triple negative breast cancer (TNBC). Activation of AhR results in epigenetic silencing of the breast cancer 1 gene (BRCA1), a necessary factor in the transcriptional activation of estrogen receptor-alpha (ERα). The purpose of this study was to examine the capacity for galangin (GAL; 3,5,7-trihydroxy-2-phenylchromen-4-one), a natural AhR antagonist, to mimic the effects of synthetic AhR antagonists alpha-naphthoflavone (αNF, 2-phenylbenzo[h]chromen-4-one) and 3'-methoxy-4'-nitroflavone (MNF; 2-(3-methoxy-4-nitrophenyl)chromen-4-one) in regards to counteracting epigenetic silencing of BRCA1 and restoring ERα protein expression. We utilized TNBC cells with hypermethylated BRCA1 and constitutively active AhR (HCC38 cells) for these experiments. After 72h in phenol-red free media, cells were treated for up to 72h against a range of GAL, αNF, and MNF concentrations in the presence or absence of estradiol (E2). Transcript levels of AhR and its downstream target genes CYP1A1 and CYP1B1 were determined by real-time polymerase chain reaction (RT-PCR). Protein levels of BRCA1, ERα, and AhR were determined by Western blot. Treatment with GAL results in stabilization of BRCA1 and ERα protein levels, similarly to αNF and MNF. To determine potential mechanisms of these observations, we are currently conducting experiments to analyze changes in BRCA1 promoter methylation using methylation-specific RT-PCR (MSP) and DNA methyltransferase 1 (DNMT1) protein levels by Western blot. These data suggest the naturally occurring flavanoid GAL may be an effective compound for modulating epigenetic repression of BRCA1 and restoring ERα levels, which may provide options for anti-hormonal therapy in ERα-negative breast cancers. Citation Format: Micah G. Donovan, Ornella I. Selmin, Donato F. Romagnolo. Galangin is an epigenetic modulator or BRCA1 and induces estrogen receptor alpha in triple negative breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1385.