Estrogen-induced epigenetic silencing of <i>FTH1</i> and <i>TFRC</i> genes reduces liver cancer cell growth and survival

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 <i>FTH1</i> and <i>TFRC</i> genes was assessed in E2-treated cancer cells. E2-induced DNA methylation was associated with decreased <i>FTH1</i> and <i>TFRC</i> 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 <i>FTH1</i> but not on <i>TFRC</i>. Knockdown of PRMT5, DNMT3B, and Estrogen-receptor alpha rescued <i>FTH1</i> from E2-induced silencing. However, knockdown of DNMT3B alone blocked the inhibitory effects of E2 on <i>TFRC</i>. Analysis of human liver tissues in publicly available datasets showed that <i>FTH1</i> and <i>TFRC</i> are highly expressed in primary liver tumours, but a lower expression is associated with better survival. Interestingly, we showed that the silencing of <i>FTH1</i> and/or <i>TFRC</i> 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.