ERβ Regulates Genes That Have Kinase and GTPase Functions and Enhance Cell Survival in Endometriosis.

Endometriosis is an estrogen-dependent gynecological disease that affects 6–10% of women of reproductive age. It is a major cause of chronic pelvic pain and infertility, and poses a heavy financial burden on society, with annual estimates totaling $22 billion in the US alone. Methylation defects have been characterized in stromal cells derived from ovarian endometriotic lesions. In particular, a CpG island in the ESR2 promoter region is hypomethylated and contributes to a corresponding increase in ERβ mRNA and protein relative to the normal endometrium. The high local levels of 17 β-Estradiol (E2) that are present in the endometriotic lesion milieu underscore the importance of elevated ERβ expression in endometriosis. However, the precise contribution of ERβ to endometriosis has not been fully characterized. In this study we show that ERβ transcriptionally regulates a subset of genes whose corresponding proteins possess intrinsic kinase or GTPase activity and contribute to endometriotic cell proliferation and survival. We correlated the differentially expressed genes from a microarray that compared normal endometrial and endometriotic stromal cells with previously identified ERβ genomic targets from ChIP-on-ChIP and ChIP-Seq experiments. Using this strategy, we found 70 differentially expressed genes in endometriosis that are potentially regulated by ERβ, 42 of which encode phosphoproteins. We validated that two of these genes are in fact ERβ genomic targets by showing 1) that their transcript and protein levels increase in response to E2, 2) that their expression decreases after ERβ siRNA knockdown, and 3) that ERβ is enriched at the promoter regions of these two genes. Furthermore, we showed that these two genes, ras-like and estrogen regulated growth inhibitor (RERG) and serum and glucocorticoid-regulated kinase-1 (SGK-1), contribute to cell proliferation and apoptosis in endometriotic stromal cells. Our results demonstrate that in endometriosis, ERβ regulates a novel and important network of genes with intrinsic kinase and GTPase activity that control cell fate. Moreover, our study underscores the contribution of an altered nuclear receptor to endometriosis and poses ERβ as a potential drug target for this debilitating disease.