Regulation of TET2 gene expression and 5mC oxidation in breast cancer cells by estrogen signaling.

Estrogen signaling plays important roles in diverse physiological and pathophysiological processes. However, the relationship between estrogen signaling and epigenetic regulation is not fully understood. Here, we explored the effect of estrogen signaling on the expression of Ten-Eleven Translocation (TET) family genes and DNA hydroxylmethylation in estrogen receptor alpha positive (ERα+) breast cancer cells. By analyzing the RNA-seq data, we identified TET2 as an estradiol (E2)-responsive gene in ERα+ MCF7 cells. RT-qPCR and Western blot analyses confirmed that both the mRNA and protein levels of TET2 gene were upregulated in MCF7 cells by E2 treatment. ChIP-seq and qPCR analyses showed that the enrichment of ERα and H3K27ac on the upstream regulatory regions of TET2 gene was increased in MCF7 cells upon E2 treatment. Moreover, E2 treatment also led to a significant increase in the global 5-hydroxymethylcytosine (5hmC) level, while knockout of TET2 abolished such E2-induced 5hmC increase. Conversely, treatment with ICI 182780, a potent and selective estrogen receptor degrader (SERD), inhibited TET2 gene expression and down-regulated the 5hmC level in MCF7 cells. Taken together, our study identified an ERα/TET2/5hmC epigenetic pathway, which may participate in the estrogen-associated physiological and pathophysiological processes.