Role of TET Dioxygenases and DNA Hydroxymethylation in Bisphenols-Stimulated Proliferation of Breast Cancer Cells

Abstract

BACKGROUND: Bisphenol A (BPA), a ubiquitous environmental endocrine disruptor targeting estrogen receptors (ERs), has been implicated in the promotion of breast cancer. Perinatal exposure of BPA could induce longitudinal alteration of DNA hydroxymethylation in imprinted loci of mouse blood cells. To date, no data has been reported on the effects of BPA on DNA hydroxymethylation in breast cells. Therefore, we asked whether BPA can induce DNA hydroxymethylation change in human breast cells. Given that dysregulated epigenetic DNA hydroxymethylation is observed in various cancers, we wondered how DNA hydroxymethylation modulates cancer development, and specifically, whether and how BPA and its analogs promote breast cancer development via DNA hydroxymethylation. OBJECTIVES: We aimed to explore the interplay of the estrogenic activity of bisphenols at environmental exposure dose levels with TET dioxygenase-catalyzed DNA hydroxymethylation and to elucidate their roles in the proliferation of ER + breast cancer cells as stimulated by environmentally relevant bisphenols. METHODS: Human MCF-7 and T47D cell lines were used as ER-dependent breast cell proliferation models, and the human MDA-MB-231 cell line was used as an ER-independent breast cell model. These cells were treated with BPA or bisphenol S (BPS) to examine BPA/BPS-related proliferation. Ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and enzyme-linked immunosorbent assays (ELISAs) were used to detect DNA hydroxymethylation. Crispr/Cas9 and RNA interference technologies, quantitative polymerase chain reaction (qPCR), and Western blot analyses were used to evaluate the expression and function of genes. Co-immunoprecipitation (Co-IP), bisulfite sequencing-PCR (BSP), and chromatin immunoprecipitation-qPCR (ChIP-qPCR) were used to identify the interactions of target proteins. RESULTS: We measured higher proliferation in ER + breast cancer cells treated with BPA or its replacement, BPS, accompanied by an ERa-dependent decrease in genomic DNA hydroxymethylation. The results of our overexpression, knockout, knockdown, and inhibition experiments suggested that TET2-catalyzed DNA hydroxymethylation played a suppressive role in BPA/BPS-stimulated cell proliferation. On the other hand, we observed that TET2 was negatively regulated by the activation of ERa (dimerized and phosphorylated), which was also induced by BPA/BPS binding. Instead of a direct interaction between TET2 and ERa, data of our Co-IP, BSP, and ChIP-qPCR experiments indicated that the activated ERa increased the DNA methyltransferase (DNMT)-mediated promoter methylation of TET2, leading to an inhibition of the TET2 expression and DNA hydroxymethylation. CONCLUSIONS: We identified a new feedback circuit of ERa activation-DNMT-TET2-DNA hydroxymethylation in ER + breast cancer cells and uncovered a pivotal role of TET2-mediated DNA hydroxymethylation in modulating BPA/BPS-stimulated proliferation. Moreover, to our knowledge, we for the first time established a linkage among...

Bisphenols and Risk of Breast Cancer: A Narrative Review of the Impact of Diet and Bioactive Food Components

“…Higher proliferation in ER-positive breast cancer cells is noted following treatment with BPA or its substitute, BPS, accompanied by an ERα-dependent decrease in genomic TET-catalyzed DNA hydroxymethylation. These findings highlight the E2-like activity of BPA/BPS and the epigenetic impact on breast tumorigenesis (97). The exposure of MCF-7 cells to BPS induces DNA methylation of transposons.…”

Understanding the Mechanistic Link between Bisphenol A and Cancer Stem Cells: A Cancer Prevention Perspective

“…The study by Dolinoy et al [58] using this model found that the methyl-donors genistein and folate could reverse the hypomethylating effects of BPA, which caused a yellow coat color in viable yellow agouti mouse offspring. A recent work by Li et al [59] found that BPA-induced proliferation of MCF-7 cells was found to be mediated through suppression of DNA hydroxymethylation. Specifically, Ten-eleven translocation (TET)2 plays a direct role in DNA hydroxymethylation in response to BPA through interaction with ERα [59].…”

“…A recent work by Li et al [ 59 ] found that BPA-induced proliferation of MCF-7 cells was found to be mediated through suppression of DNA hydroxymethylation. Specifically, Ten-eleven translocation (TET)2 plays a direct role in DNA hydroxymethylation in response to BPA through interaction with ERα [ 59 ]. This novel pathway suggests a potential mechanism through which epigenetics play a role in breast cancer development in response to BPA exposure.…”

Epigenetic Alteration Shaped by the Environmental Chemical Bisphenol A

“…Cancer cell proliferation has been reported to be mediated by DNA methylation induced by BPA exposure. Recently, Li et al (2020) revealed the pivotal role of TET dioxygenases and DNA hydroxymethylation in the bisphenol-stimulated proliferation of breast cancer cells. They found that BPA or its replacement BPS increased the promoter methylation of TET2, leading to an inhibition of TET2 expression and DNA hydroxymethylation.…”