No abstract

Steroid receptors in the stromal cells of endometrium and its disease counterpart tissue endometriosis play critical physiologic roles. We found that mRNA and protein levels of estrogen receptor 2 (ESR2) were strikingly higher, whereas levels of estrogen receptor 1 (ESR1), total progesterone receptor (PGR), and progesterone receptor B (PGR B) were significantly lower in endometriotic versus endometrial stromal cells. Because ESR2 displayed the most striking levels of differential expression between endometriotic and endometrial cells, and the mechanisms for this difference are unknown, we tested the hypothesis that alteration in DNA methylation is a mechanism responsible for severely increased ESR2 mRNA levels in endometriotic cells. We identified a CpG island occupying the promoter region (À197/þ359) of the ESR2 gene. Bisulfite sequencing of this region showed significantly higher methylation in primary endometrial cells (n ¼ 8 subjects) versus endometriotic cells (n ¼ 8 subjects). The demethylating agent 5-aza-2 0 -deoxycytidine significantly increased ESR2 mRNA levels in endometrial cells. Mechanistically, we employed serial deletion mutants of the ESR2 promoter fused to the luciferase reporter gene and transiently transfected into both endometriotic and endometrial cells. We demonstrated that the critical region (À197/þ372) that confers promoter activity also bears the CpG island, and the activity of the ESR2 promoter was strongly inactivated by in vitro methylation. Taken together, methylation of a CpG island at the ESR2 promoter region is a primary mechanism responsible for differential expression of ESR2 in endometriosis and endometrium. These findings may be applied to a number of areas ranging from diagnosis to the treatment of endometriosis.

Loss of progesterone signaling in the endometrium may be a causal factor in the development of endometriosis, and progesterone resistance is commonly observed in women with this disease. In endometriotic stromal cells, the levels of progesterone receptor (PR), particularly the PR-B isoform, are significantly decreased, leading to a loss of paracrine signaling. PR deficiency likely underlies the development of progesterone resistance in women with endometriosis who no longer respond to progestin therapy. Here we review the complex epigenetic and transcriptional mechanisms leading to PR deficiency. The initial event may involve deficient methylation of the estrogen receptor (ER)β promoter resulting in pathologic overexpression of ERβ in endometriotic stromal cells. We speculate that alterations in the relative levels of ERβ and ERα in endometrial tissue dictate E2-regulated PR expression, such that a decreased ERα--ERβ ratio may result in suppression of PR. In this review, we propose a molecular model that may be responsible for changes in ERβ and ERα leading to PR loss and progesterone resistance in endometriosis.

This is the first demonstration of methylation-dependent regulation of SF-1 in any mammalian tissue. These findings point to a new mechanism for targeting local estrogen biosynthesis in endometriosis.

Our findings indicate that miRNAs are differentially expressed between human leiomyoma and matched myometrium. Given this differential expression, miRNAs may play a role in the pathogenesis of uterine leiomyoma and may serve as future therapeutic targets for the treatment of these tumors.

High levels of ERbeta suppress ERalpha expression and response to estradiol in endometrial and endometriotic stromal cells via binding to classic and nonclassic DNA motifs in alternatively used ERalpha promoters. ERbeta also regulates cell cycle progression and might contribute to proliferation of endometriotic stromal cells. We speculate that a significantly increased ratio of ERbeta:ERalpha in endometriotic tissues may also suppress progesterone receptor expression and contribute to progesterone resistance. Thus, ERbeta may serve as a significant therapeutic target for endometriosis.

No abstract

Estrogen receptor-A (ERA) and its ligand estradiol play critical roles in breast cancer growth and are important therapeutic targets for this disease. Using chromatin immunoprecipitation (ChIP)-on-chip, ligand-bound ERA was recently found to function as a master transcriptional regulator via binding to many cis-acting sites genome-wide. Here, we used an alternative technology (ChIP cloning) and identified 94 ERA target loci in breast cancer cells. The ERA-binding sites contained both classic estrogen response elements and nonclassic binding sequences, showed specific transcriptional activity in reporter gene assay, and interacted with the key transcriptional regulators, including RNA polymerase II and nuclear receptor coactivator-3. The great majority of the binding sites were located in either introns or far distant to coding regions of genes. Forty-three percent of the genes that lie within 50 kb to an ERA-binding site were regulated by estradiol. Most of these genes are novel estradiol targets encoding receptors, signaling messengers, and ion binders/ transporters. mRNA profiling in estradiol-treated breast cancer cell lines and tissues revealed that these genes are highly ERA responsive both in vitro and in vivo. Among estradiol-induced genes, Wnt11 was found to increase cell survival by significantly reducing apoptosis in breast cancer cells. Taken together, we showed novel genomic binding sites of ERA that regulate a novel set of genes in response to estradiol in breast cancer. Our findings suggest that at least a subset of these genes, including Wnt11, may play important in vivo and in vitro biological roles in breast cancer. [Cancer Res 2007;67(10):5017-24]