Exposure to physiological estrogens or xenoestrogens (e.g., zearalenone or bisphenol A) increases the risk for cancer. However, little information is available on their significance in ovarian cancer. We present a comprehensive study on the effect of estradiol, zearalenone and bisphenol A on the phenotype, mRNA, intracellular and cell-free miRNA expression of human epithelial ovarian cell lines. Estrogens induced a comparable effect on the rate of cell proliferation and migration as well as on the expression of estrogen-responsive genes (GREB1, CA12, DEPTOR, RBBP8) in the estrogen receptor α (ERα)-expressing PEO1 cell line, which was not observable in the absence of this receptor (in A2780 cells). The basal intracellular and cell-free expression of miR200s and miR203a was higher in PEO1, which was accompanied with low ZEB1 and high E-cadherin expression. These miRNAs showed a rapid but intermittent upregulation in response to estrogens that was diminished by an ERα-specific antagonist. The role of ERα in the regulation of the MIR200B-MIR200A-MIR429 locus was further supported by publicly available ChIP-seq data. MiRNA expression of cell lysates correlated well with cell-free miRNA expression. We conclude that cell-free miR200s might be promising biomarkers to assess estrogen sensitivity of ovarian cells.

Xenoestrogens are synthetic or natural compounds that mimic the effect of endogenous estrogens by binding to estrogen receptors (ERs). Human exposure to xenoestrogens is increasing globally, raising substantial concerns regarding their endocrine-disrupting effects. Here, we investigated the ERα-mediated genomic and transcriptional response of human ovarian cells following exposure to estradiol (E2), zearalenone (ZEA), and bisphenol A (BPA) using ChIP-seq integrated with transcriptomic analysis. Our results demonstrate that the ERα-dependent response induced by ZEA closely resembles that of E2, whereas BPA elicits a markedly attenuated response. ERα signal intensity was higher in cells treated with E2 or ZEA than in cells treated with BPA, indicating reduced ERα occupancy in response to BPA exposure. We identified 641 genomic regions that were occupied by ERα after any treatment, defining a core set of shared binding sites. Integration with mRNA-seq datasets revealed 162 ERα-binding sites located within ±50 kb of the transcription start sites of 109 upregulated genes. Among these, 28 genes were induced across all treatments, constituting a core estrogen-responsive gene set in human ovarian cells. RT-qPCR validation of six representative genes (GREB1, RASGRP1, CISH, RBBP8, KCNF1, and LONRF2) confirmed stronger and sustained transcriptional induction following E2 and ZEA exposure than following BPA exposure; this induction was inhibited by the ERα antagonist MPP. Our findings suggest that BPA has a lower capacity to activate ERα chromatin binding and downstream transcriptional programs, affecting primarily high-affinity estrogen-responsive loci in human ovarian cells.