ABSTRACT

Estrogen (E2) regulates hundreds of genes involved in cell metabolism and disrupts iron homoeostasis in various cell types. Herein, we addressed whether E2-induced epigenetic modifications are involved in modulating the expression of iron-regulatory genes. Epigenetic status of FTH1 and TFRC genes was assessed in E2-treated cancer cells. E2-induced DNA methylation was associated with decreased FTH1 and TFRC expression in Hep-G2 and Huh7 cells, but not in AGS or MCF7 cells. Demethylation with 5-Aza-2-deoxycytidine upregulated the expression of both these genes in Hep-G2 cells. The expression of DNMT3B, PRMT5, and H4R3me2s increased in E2-treated cells. Chromatin immunoprecipitation showed that E2 treatment recruited PRMT5 and H4R3me2s on FTH1 but not on TFRC. Knockdown of PRMT5, DNMT3B, and Estrogen-receptor alpha rescued FTH1 from E2-induced silencing. However, knockdown of DNMT3B alone blocked the inhibitory effects of E2 on TFRC. Analysis of human liver tissues in publicly available datasets showed that FTH1 and TFRC are highly expressed in primary liver tumours, but a lower expression is associated with better survival. Interestingly, we showed that the silencing of FTH1 and/or TFRC inhibited carcinogenesis in Hep-G2 cells. For the first time, our findings uncovered the novel signalling pathway involved in the protective effects of E2 against liver cancer.

 抽象的

雌激素 (E2) 调节数百个参​​与细胞代谢的基因，并破坏各种细胞类型中的铁稳态。在此，我们探讨了 E2 诱导的表观遗传修饰是否参与调节铁调节基因的表达。在 E2 处理的癌细胞中评估了FTH1和TFRC基因的表观遗传状态。 E2诱导的DNA甲基化与Hep-G2和Huh7细胞中FTH1和TFRC表达降低相关，但与AGS或MCF7细胞中无关。 5-Aza-2-deoxycytidine 去甲基化上调了 Hep-G2 细胞中这两个基因的表达。 E2 处理的细胞中 DNMT3B、PRMT5 和 H4R3me2s 的表达增加。染色质免疫沉淀显示 E2 处理在FTH1上募集 PRMT5 和 H4R3me2，但在TFRC上未募集。 PRMT5、DNMT3B 和雌激素受体 α 的敲低可将FTH1从 E2 诱导的沉默中拯救出来。然而，单独敲低 DNMT3B 会阻断 E2 对TFRC的抑制作用。对公开数据集中的人类肝脏组织的分析表明， FTH1和TFRC在原发性肝脏肿瘤中高表达，但较低的表达与更好的生存相关。有趣的是，我们发现FTH1和/或TFRC的沉默可抑制 Hep-G2 细胞的癌变。我们的研究结果首次揭示了 E2 对肝癌的保护作用所涉及的新信号通路。