P1-05-02: Epigenetic Regulation by Alcohol Reactivates Estrogen Receptor alpha in Estrogen Receptor alpha-Negative Cells.

Abstract

Abstract Introduction: Alcohol consumption is an established risk factor for breast cancer development and contributes to mammary tumorigenesis through the regulation of estrogen receptor alpha (ERα) expression. Previously, we reported that alcohol consumption in the MMTV-neu ERα-negative mouse model of human breast cancer resulted in significantly increased ERα expression compared to non-alcohol consuming mice. Thus, our results indicated that alcohol consumption led to reexpression of ERα in an ERα-negative mouse model. Several lines of evidence suggest that ERα expression in ERα-negative cancer cells is inhibited through epigenetic mechanisms. In this study, we examine the role of alcohol on ERα reactivation through changes in histone modifications, DNA methylation, and recruitment of transcriptional regulation complexes on the ERα promoter, in vitro. Methods: ERα-negative MDA-MB-231 human breast cancer cells were treated with 0.1%, 0.2% and 0.5% v/v ethanol in culture media for 24 h. Chromatin immunoprecipitation (ChIP) assays were used to examine the enrichment of active and inactive markers of chromatin on the ERα promoter following alcohol treatment. DNA methylation at three ERα promoter CpG dinucleotide sites was assessed following alcohol treatment using methyl-sensitive restriction enzyme (MSRE)-qPCR. ChIP assays are used to determine the binding of the transcriptional regulation complexes, pRb2/p130-E2F4/5-HDAC1-SUV39H1-p300 and pRb2/p130-E2F4/5-HDAC1-SUV39H1-DNMT1, to the ERa promoter following alcohol treatment. MCF-7 human breast cancer cells served as an ERα-positive control. Results: We report that histone modifications were affected by alcohol treatment in a dose-dependent manner. Enrichment levels of all five chromatin markers tested, which includes markers of active and inactive transcription, were significantly altered as a result of alcohol treatment (p<0.05). We also found significantly decreased DNA methylation at three ERα promoter CpG sites as a result of alcohol treatment (p<0.05). Experiments testing the recruitment of the transcriptional regulation complexes, pRb2/p130-E2F4/5-HDAC1-SUV39H1-p300 and pRb2/p130-E2F4/5-HDAC1-SUV39H1-DNMT1, are currently ongoing. Discussion: ERα expression has been linked to mammary carcinogenesis and clinical outcome in breast cancer patients. However, approximately one out of three breast cancers lack ERα expression at the time of diagnosis and many breast cancers lose ERα expression during the course of tumor progression. Thus, understanding the regulation of ERα expression in breast cancer cells is critical and results from this study will facilitate the development of novel therapeutic strategies and treatment options for hormone-resistant breast cancer. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-05-02.