Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, United States; Department of Hygienic Analysis and Detection and Ministry of Education Key Lab for Modern Toxicology, School of Public Health, Nanjing Medical University, Nanjing, China.
Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, United States.
Toxicol Appl Pharmacol. 2019 Mar 15;367:12-22. doi: 10.1016/j.taap.2019.01.016. Epub 2019 Jan 23.
Catechol-O-methyltransferase (COMT) acts as a 'gate-keeper' to prevent DNA damage during estrogen metabolism. Both experimental and epidemiological studies suggest the role of COMT in pathogenesis of human breast cancer (BCa). It was previously reported that inhibition of COMT enzyme activity in estradiol-treated human breast epithelial carcinoma-derived MCF-7 cells caused increased oxidative DNA damage and formation of mutagenic depurinating adducts. To improve our understanding of factors influencing estrogen metabolism in BCa, it requires a mechanistic study illustrating the regulation of this 'gate-keeper'. We investigated the epigenetic mechanisms underlying decreased COMT transcription in MCF-7 cells exposed to 17ß-estradiol (E2) and the phytoestrogen, genistein (GEN). CpG site-specific methylation at promoters for both soluble (S) and membrane-bound (MB) COMT transcripts were assessed. Both E2 and GEN induced CpG site-specific methylation within the distal promoter of MB-COMT. In addition, ChIP analysis showed that there was increased binding of DNMT3B, MBD2 and HDAC1 within this promoter. These epigenetic changes were associated with decreased COMT transcript levels. Interestingly, sulforaphane, an antioxidant commonly found in cruciferous vegetables, was able to reverse the estrogen-induced epigenetic changes and gene silencing of COMT. Our data provide a new insight in epigenetically targeting COMT transcription. Since reactive estrogen metabolites may contribute to breast cancer, our findings may help in developing prevention and/or intervention strategies for human BCa.
儿茶酚-O-甲基转移酶（COMT）作为一种“守门员”，可防止雌激素代谢过程中的 DNA 损伤。实验和流行病学研究表明，COMT 在人类乳腺癌（BCa）发病机制中起作用。先前的研究报道，在雌二醇处理的人乳腺上皮癌细胞 MCF-7 中抑制 COMT 酶活性会导致氧化 DNA 损伤增加和诱变脱嘌呤加合物的形成。为了更好地了解影响 BCa 中雌激素代谢的因素，需要进行一项阐明这种“守门员”调控机制的机制研究。我们研究了 MCF-7 细胞暴露于 17β-雌二醇（E2）和植物雌激素染料木黄酮（GEN）时 COMT 转录降低的表观遗传机制。评估了可溶性（S）和膜结合（MB）COMT 转录物启动子的 CpG 位点特异性甲基化。E2 和 GEN 均诱导 MB-COMT 远端启动子的 CpG 位点特异性甲基化。此外，ChIP 分析表明，该启动子内的 DNMT3B、MBD2 和 HDAC1 结合增加。这些表观遗传变化与 COMT 转录物水平降低有关。有趣的是，十字花科蔬菜中常见的抗氧化剂萝卜硫素能够逆转雌激素诱导的 COMT 表观遗传改变和基因沉默。我们的数据为表观遗传靶向 COMT 转录提供了新的见解。由于反应性雌激素代谢物可能导致乳腺癌，因此我们的发现可能有助于为人类 BCa 开发预防和/或干预策略。
