MON-008 Estrogen-Responsive and -Unresponsive Gene Expressions Promoted by Enhancers Specifically Hypomethylated in Endometriotic Cells May Become a Molecular Marker in Endometriosis Lesions

BACKGROUND: Endometriosis is an estrogen-dependent, inflammatory disease, and the role of estrogen is obvious because the symptoms associated with endometriosis often disappear after menopause, and GnRH agonists or progestin relieve the pelvic lesions and endometriosis-associated pain. However, there are limitations to these treatments that target the estrogen reduction in endometriotic lesions. We sought to define an aberrant gene expression derived from an epigenetic background in endometriosis.Objective: In the hope of overcoming the limitations of endocrine treatments in endometriosis, we examined estrogen receptor (ER)-dependent and -independent gene expressions promoted by active enhancers specifically hypomethylated in endometriotic cells. Patients: Institutional Review Boards approved this project. We obtained the informed consent from all patients. The chocolate cyst lining in ovaries of patients with endometriosis was the source of endometriotic tissue. As the control, the eutopic endometrial tissues were obtained from uteri of premenopausal women who had uterine leiomyoma.Methods: Stromal cells were prepared from endometriotic and endometrial tissues. Gene expression was examined using RT-PCR. The potential function of hypomethylated gene sequence as an active enhancer was evaluated by ChIP analysis using anti-H3K4me1 and anti-H3K27ac antibodies and eRNA expression analysis. Using ChIP-seq and ChIA-PET analysis in silico, ER-specific loci within gene bodies and the up- and downstream regions were extracted. ER-dependent gene expression was examined using estradiol or SERM.Results: ER expression in endometriotic cells.1) Relative expression of ERα mRNA was estimated to be one tenth of that in endometrial cells. 2) Relative expression of ERβ1 mRNA was 40-fold higher than that in endometrial cells, which is at a comparable level of the ERα. 3) ERβ2 mRNA expression was at a comparable level of the ERβ1. From our DNA methylation and gene expression analysis, 6 genes were selected and classified into 3 categories: estrogen-responsive genes with specific methylation (ESR1 and ESR2) or without any methylation (TGFα and GREB1), and estrogen-unresponsive but upregulated genes depending on specific hypomethylation (GATA6 and CYP19). 4) ChIP-seq and ChIA-PET analysis in silico suggested the presence of ER-specific loci within gene bodies and the up- and downstream in estrogen-responsive genes. 5) ChIP and eRNA expression analysis predicted active enhancer regions both in estrogen-responsive and -unresponsive genes. 6) In response to estrogen, TGFα and GREB1 expressions were upregulated, but ESR1 and ESR2 showed marginal responses.Conclusion: We focused on estrogen-responsive and -unresponsive genes linked to the epigenetic environment of endometriotic lesions, and revealed a facet of gene expression in endometriotic cells.