Molecular and cellular determinants of estrogen receptor alpha expression

Epigenetic regulation of sex dimorphism in cardiovascular health

Cardiovascular diseases (CVDs) remain the leading cause of morbidity and mortality, affecting people of all races, ages, and sexes. Substantial sex dimorphism exists in the prevalence, manifestation, and outcomes of CVDs. Understanding the role of sex hormones as well as sex-hormone-independent epigenetic mechanisms could play a crucial role in developing effective and sex-specific cardiovascular therapeutics. Existing research highlights significant disparities in sex hormones, epigenetic regulators, and gene expression related to cardiac health, emphasizing the need for a nuanced understanding of these variations between men and women. Despite these differences, current treatment approaches for CVDs often lack sex-specific considerations. A pivotal shift toward personalized medicine, informed by comprehensive insights into sex-specific DNA methylation, histone modifications, and non-coding RNA dynamics, holds the potential to revolutionize CVD management. By understanding sex-specific epigenetic complexities, independent of sex hormone influence, future cardiovascular research can be tailored to achieve effective diagnostic and therapeutic interventions for both men and women. This review summarizes the current knowledge and gaps in epigenetic mechanisms and sex dimorphism implicated in CVDs.

Gene expression and trace elements in Greenlandic ringed seals (Pusa hispida)

Marine top predators such as ringed seals biomagnify environmental contaminants; and with the increasing human activities in the Arctic, ringed seals are exposed to biologically significant concentrations of trace elements resulting in reproductive impairment, immunosuppression, and neurological damages. Little is known about the molecular effects of heavy metals on these vulnerable apex predators suffering from a rapidly changing Arctic with significant loss of sea-ice. In the present study, concentrations of cadmium (Cd), mercury (Hg) and selenium (Se) were measured in liver of sixteen Greenlandic ringed seals (nine adults and seven subadults) together with molecular biomarkers involved in bio-transformation, oxidative stress, endocrine disruption and immune activity in blood and blubber. The concentrations of trace elements increased in the following order: Hg > Se > Cd with levels of mercury and selenium being highest in adults. Aryl hydrocarbon receptor nuclear translocator (ARNT), peroxisome proliferator activated receptor alpha (PPARα, estrogen receptor alpha (ESR1), thyroid hormone receptor alpha (TRα) and interleukin - 2 (IL-2) mRNA transcript levels were highest in blubber, while heat shock protein 70 (HSP70) and interleukin - 10 (IL-10) were significantly higher in blood. There were no significant correlations between the concentrations of trace elements and mRNA transcript levels suggesting that stressors other than the trace elements investigated are responsible for the changes in gene expression levels. Since Hg seems to increase in Greenlandic ringed seals, there is a need to re-enforce health monitoring of this ringed seal population.

Hormone replacement therapy for postmenopausal atherosclerosis is offset by late age iron deposition

Postmenopausal atherosclerosis (AS) has been attributed to estrogen deficiency. However, the beneficial effect of hormone replacement therapy (HRT) is lost in late postmenopausal women with atherogenesis. We asked whether aging-related iron accumulation affects estrogen receptor α (ERα) expression, thus explaining HRT inefficacy. A negative correlation has been observed between aging-related systemic iron deposition and ERα expression in postmenopausal AS patients. In an ovariectomized Apoe-/- mouse model, estradiol treatment had contrasting effects on ERα expression in early versus late postmenopausal mice. ERα expression was inhibited by iron treatment in cell culture and iron-overloaded mice. Combined treatment with estradiol and iron further decreased ERα expression, and the latter effect was mediated by iron-regulated E3 ligase Mdm2. In line with these observations, cellular cholesterol efflux was reduced, and endothelial homeostasis was disrupted. Consequently, AS was aggravated. Accordingly, systemic iron chelation attenuated estradiol-triggered progressive AS in late postmenopausal mice. Thus, iron and estradiol together downregulate ERα through Mdm2-mediated proteolysis, providing a potential explanation for failures of HRT in late postmenopausal subjects with aging-related iron accumulation. This study suggests that immediate HRT after menopause, along with appropriate iron chelation, might provide benefits from AS.

Glucocorticoid induced loss of oestrogen receptor alpha gene methylation and restoration of sensitivity to fulvestrant in triple negative breast cancer

The response to psychological stress can differ depending on the type and duration of the stressor. Acute stress can facilitate a "fight or flight response" and aid survival, whereas chronic long-term stress with the persistent release of stress hormones such as cortisol has been shown to be detrimental to health. We are now beginning to understand how this stress hormone response impacts important processes such as DNA repair and cell proliferation processes in breast cancer. However, it is not known what epigenetic changes stress hormones induce in breast cancer. Epigenetic mechanisms include modification of DNA and histones within chromatin that may be involved in governing the transcriptional processes in cancer cells in response to changes by endogenous stress hormones. The contribution of endogenous acute or long-term exposure of glucocorticoid stress hormones, and exogenous glucocorticoids to methylation patterns in breast cancer tissues with different aetiologies remains to be evaluated. In vitro and in vivo models were developed to investigate the epigenetic modifications and their contribution to breast cancer progression and aetiology. A panel of triple negative breast cancer cell lines were treated with the glucocorticoid, cortisol which resulted in epigenetic alteration characterised by loss of methylation on promoter regions of tumour suppressor genes including ESR1, and loss of methylation on LINE-1 repetitive element used as a surrogate marker for global methylation. This was verified in vivo in MDA-MB-231 xenografts; the model verified the loss of methylation on ESR1 promoter, and subsequent increase in ESR1 expression in primary tumours in mice subjected to restraint stress. Our study highlights that DNA methylation landscape in breast cancer can be altered in response to stress and glucocorticoid treatment.

A review on epidermal growth factor receptor's role in breast and non-small cell lung cancer

Epithelial growth factor receptor (EGFR) is a cell surface transmembrane receptor that mediates the tyrosine signaling pathway to carry the extracellular messages inside the cell and thereby alter the function of nucleus. This leads to the generation of various protein products to up or downregulate the cellular function. It is encoded by cell erythroblastosis virus oncogene B1, so called C-erb B1/ERBB2/HER-2 gene that acts as a proto-oncogene. It belongs to the HER-2 receptor-family in breast cancer and responds best with anti-Herceptin therapy (anti-tyrosine kinase monoclonal antibody). HER-2 positive breast cancer patient exhibits worse prognosis without Herceptin therapy. Similar incidence and prognosis are reported in other epithelial neoplasms like EGFR + lung non-small cell carcinoma and glioblastoma (grade IV brain glial tumor). Present study highlights the role and connectivity of EGF with various cancers via signaling pathways, cell surface receptors mechanism, macromolecules, mitochondrial genes and neoplasm. Present study describes the EGFR associated gene expression profiling (in breast cancer and NSCLC), relation between mitrochondrial genes and carcinoma, and several in vitro and in vivo models to screen the synergistic effect of various combination treatments. According to this study, although clinical studies including targeted treatments, immunotherapies, radiotherapy, TKi-EGFR combined targeted therapy have been carried out to investigate the synergism of combination therapy; however still there is a gap to apply the scenarios of experimental and clinical studies for further developments. This review will give an idea about the transition from experimental to most advanced clinical studies with different combination drug strategies to treat cancer.

Sex Differences, Estrogen Metabolism and Signaling in the Development of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a complex and devastating disease with a poor long-term prognosis. While women are at increased risk for developing PAH, they exhibit superior right heart function and higher survival rates than men. Susceptibility to disease risk in PAH has been attributed, in part, to estrogen signaling. In contrast to potential pathological influences of estrogen in patients, studies of animal models reveal estrogen demonstrates protective effects in PAH. Consistent with this latter observation, an ovariectomy in female rats appears to aggravate the condition. This discrepancy between observations from patients and animal models is often called the "estrogen paradox." Further, the tissue-specific interactions between estrogen, its metabolites and receptors in PAH and right heart function remain complex; nonetheless, these relationships are essential to characterize to better understand PAH pathophysiology and to potentially develop novel therapeutic and curative targets. In this review, we explore estrogen-mediated mechanisms that may further explain this paradox by summarizing published literature related to: (1) the synthesis and catabolism of estrogen; (2) activity and functions of the various estrogen receptors; (3) the multiple modalities of estrogen signaling in cells; and (4) the role of estrogen and its diverse metabolites on the susceptibility to, and progression of, PAH as well as their impact on right heart function.

Serum estrogen and its soluble receptor levels in Egyptian patients with acute leukemia: case-control study

Background

Acute leukemias are malignant neoplastic diseases that arise from either lymphoid [ALL] or myeloid [AML] cell lines that are distinguished by the proliferation of BM non-functional immature cells and subsequently released into the bloodstream. ALL is prevalent malignancy in young, while AML in older. Diagnosis is usually routinely performed through peripheral blood count and smear then confirmed by BM aspirate. It is remarkable to notice that leukemia can be manifested at high, low, and even at normal leucocyte count. While treatment results have improved steadily over the last decades in younger and adults, limited changes have been in survival among subjects of age > 60 years. Aim of the work is to measure the serum estrogen [E2] and its soluble receptor [ER] levels in acute leukemia patients and extrapolate its possible clinical significance. This study included 40 [20 females and 20 males] healthy volunteers clinically free from any disease, 40 [20 females and 20 males] AML patients, and 40 [20 females and 20 males] ALL. To all subjects, serum E2 and its soluble ER level were investigated by ELISA.

Results

Serum E2 [pg/ml] level was lower in AML and ALL female and male patients groups than control group. Serum ER [ng/ml] level was lower in AML and ALL female and male patients groups than control group.

Conclusion

Estimation of serum E2 and its soluble ER level is of edifying diagnostic value. Determination of serum E2 and its soluble ER level in AML and ALL patients is of value in deciding treatment therapeutic target protocol.

Single-cell immunoblotting resolves estrogen receptor-α isoforms in breast cancer

An array of isoforms of the nuclear estrogen receptor alpha (ER-α) protein contribute to heterogeneous response in breast cancer (BCa); yet, a single-cell analysis tool that distinguishes the full-length ER-α66 protein from the activation function-1 deficient ER-α46 isoform has not been reported. Specific detection of protein isoforms is a gap in single-cell analysis tools, as the de facto standard immunoassay requires isoform-specific antibody probes. Consequently, to scrutinize hormone response heterogeneity among BCa tumor cells, we develop a precision tool to specifically measure ER-α66, ER- α46, and eight ER-signaling proteins with single-cell resolution in the highly hetero-clonal MCF-7 BCa cell line. With a literature-validated pan-ER immunoprobe, we distinguish ER-α66 from ER-α46 in each individual cell. We identify ER-α46 in 5.5% of hormone-sensitive (MCF-7) and 4.2% of hormone-insensitive (MDA-MB-231) BCa cell lines. To examine whether the single-cell immunoblotting can capture cellular responses to hormones, we treat cells with tamoxifen and identify different sub-populations of ER-α46: (i) ER-α46 induces phospho-AKT at Ser473, (ii) S6-ribosomal protein, an upstream ER target, activates both ER-α66 and ER-α46 in MCF-7 cells, and (iii) ER-α46 partitions MDA-MB-231 subpopulations, which are responsive to tamoxifen. Unlike other single-cell immunoassays, multiplexed single-cell immunoblotting reports–in the same cell–tamoxifen effects on ER signaling proteins and on distinct isoforms of the ER-α protein.

Methylation as a critical epigenetic process during tumor progressions among Iranian population: an overview

Cancer is one of the main health challenges and leading causes of deaths in the world. Various environmental and genetic risk factors are associated with tumorigenesis. Epigenetic deregulations are also important risk factors during tumor progression which are reversible transcriptional alterations without any genomic changes. Various mechanisms are involved in epigenetic regulations such as DNA methylation, chromatin modifications, and noncoding RNAs. Cancer incidence and mortality have a growing trend during last decades among Iranian population which are significantly related to the late diagnosis. Therefore, it is required to prepare efficient molecular diagnostic panels for the early detection of cancer in this population. Promoter hyper methylation is frequently observed as an inhibitory molecular mechanism in various genes associated with DNA repair, cell cycle regulation, and apoptosis during tumor progression. Since aberrant promoter methylations have critical roles in early stages of neoplastic transformations, in present review we have summarized all of the aberrant methylations which have been reported during tumor progression among Iranian cancer patients. Aberrant promoter methylations are targetable and prepare novel therapeutic options for the personalized medicine in cancer patients. This review paves the way to introduce a non-invasive methylation specific panel of diagnostic markers for the early detection of cancer among Iranians.

Emerging role of pioneer transcription factors in targeted ERα positive breast cancer

Transcription factors (TFs) are modular protein groups that preferably bind to DNA sequences and guide genomic expression through transcription. Among these key regulators, “pioneer factors” are an emerging class of TFs that specifically interact with nucleosomal DNA and facilitate accessible genomic binding sites for the additional TFs. There is growing evidence of these specialized modulators in particular malignancies, as highlighted by agents’ clinical efficacy, specifically targeting nuclear hormone receptors. They have been implicated in multiple cancers more recently, with a high proportion inculpating on hormone influential cancers. Moreover, extended crosstalk and cooperation between ERα pioneering factors in estrogen-dependent breast cancer (BC) remain elucidated. This review discusses on the recent advances in our understanding of pioneer TFs in cancer, especially highlighting its potentiality to modulate chromatin condensation to permit ERα recruitment in BC cells. Through the study it was concluded that the highly prospected pioneer TFs in BC, including FOXA1, TLE1, PBX1, and GATA3, possess the potential therapeutic significance and further innovations in the field could yield targeted therapy in cancer treatment.

6-Prenylnaringenin from Hops Disrupts ERα-Mediated Downregulation of CYP1A1 to Facilitate Estrogen Detoxification

Botanical dietary supplements (BDS) containing hops are sold as women's health supplements due to the potent hop phytoestrogen, 8-prenylnaringenin (8-PN), and the cytoprotective chalcone, xanthohumol. Previous studies have shown a standardized hop extract to beneficially influence chemical estrogen carcinogenesis in vitro by fostering detoxified 2-hydroxylation over genotoxic 4-hydroxylation estrogen metabolism. In this study, hop extract and its bioactive compounds were investigated for its mechanism of action within the chemical estrogen carcinogenesis pathway, which is mainly mediated through the 4-hydroxylation pathway catalyzed by CYP1B1 that can form gentoxic quinones. Aryl hydrocarbon receptor (AhR) agonists induce CYP1A1 and CYP1B1, while estrogen receptor alpha (ERα) inhibits transcription of CYP1A1, the enzyme responsible for 2-hydroxylated estrogens and the estrogen detoxification pathway. An In-Cell Western MCF-7 cell assay revealed hop extract and 6-prenylnaringenin (6-PN) degraded ERα via an AhR-dependent mechanism. Reverse transcription PCR and xenobiotic response element luciferase assays showed hop extract and 6-PN-mediated activation of AhR and induction of CYP1A1. A reduction in estrogen-mediated DNA (cytosine-5)-methyltransferase 1 (DNMT1) downregulation of CYP1A1 accompanied this activity in a chromatin immunoprecipitation assay. Ultimately, hop extract and 6-PN induced preferential metabolism of estrogens to their detoxified form in vitro. These results suggest that the standardized hop extract and 6-PN activate AhR to attenuate epigenetic inhibition of CYP1A1 through degradation of ERα, ultimately increasing 2-hydroxylated estrogens. A new mechanism of action rationalizes the positive influence of hop BDS and 6-PN on oxidative estrogen metabolism in vitro and, thus, potentially on chemical estrogen carcinogenesis. The findings underscore the importance of elucidating various biological mechanisms of action and standardizing BDS to multiple phytoconstituents for optimal resilience promoting properties.

Scl-Ab reverts pro-osteoclastogenic signalling and resorption in estrogen deficient osteocytes

Background

Neutralising antibodies to sclerostin (Scl-Ab) have shown significant potential to induce bone formation and decrease bone resorption, increase strength and substantially reduce fracture risk in animal studies and clinical trials. Mechanical loading negatively regulates sclerostin expression, and sclerostin has been shown to induce RANKL synthesis in osteocytes. However, how Scl-Ab governs osteocyte regulation of osteoclast differentiation and function is not fully understood. We have recently discovered that osteoblasts and osteocytes alter osteoclastogenic signalling (RANKL/OPG) during estrogen-deficiency, and that osteoblast-induced osteoclastogenesis and resorption are exacerbated. However, it is not known whether estrogen deficient osteocytes exacerbate osteoclastogenesis. The aims of this study were to (1) establish whether osteocytes induce osteoclastogenesis and bone resorption during estrogen deficiency in vitro (2) investigate whether the sclerostin antibody can revert osteocyte-mediated osteoclastogenesis and resorption by attenuating RANKL/OPG expression.

Results

Using conditioned media and co-culture experiments we found increased osteocyte-induced osteoclastogenesis and bone resorption in estrogen deficient conditions. This is the first study to report that administration of Scl-Ab has the ability to revert osteocyte-mediated osteoclastogenesis and resorption by decreasing RANKL/OPG ratio expression and increasing WISP1 expression in estrogen deficient osteocytes.

Conclusions

This study provides an enhanced understanding of the biological changes underpinning decreases in bone resorption following Scl-Ab treatment observed in vivo by revealing that Scl-Ab can reduce pro-osteoclastogenic cell signalling between osteocytes and osteoclasts.

ESR1 gene variants, haplotypes and diplotypes may influence the risk of breast cancer and mammographic density

Breast cancer as the most common cancer worldwide is influenced by genetic and physiological factors. Based on some evidence indicating the role of estrogen receptor 1 gene (ESR1) in breast cancer development, in this study, the association of three common variations in ESR1 gene with breast cancer and density in an Iranian population was evaluated. In a case-control study, 400 blood samples were collected for DNA extraction and genotyping. Breast density was assessed using mammography. ESR1 rs6915267 (G/A), rs2077647 (C/T) and rs1801132 (C/G) were genotyped using ARMS-PCR method. PHASE program was used to estimate the haplotypes frequencies. Our data analysis showed rs6915267 GA genotype in the heterozygous (GA) as well as co-dominant models was associated with lower mammographic density. None of the three variations were associated with the breast cancer risk. Haplotype analysis indicated G-T-C haplotype of rs6915267, rs2077647 and rs1801132 [OR = 0.54, 95% CI (0.31-0.92), p = 0.025] and G-T/G-T diplotype of rs6915267-rs2077647 [OR = 0.38, 95% CI (0.17-0.86), p = 0.019] were associated with a decreased risk of breast cancer. ESR1 may affect density of the breast and its haplotypes may modulate breast cancer risk.

Organic extract of indoor dust induces estrogen-like effects in human breast cancer cells

Indoor dust often contains organic contaminants, which adversely impacts human health. In this study, the organic contaminants in the indoor dust from commercial offices and residential houses in Nanjing, China were extracted and their effects on human breast cancer cells (MCF-7) were investigated. Both dust extracts promoted proliferation of MCF-7 cells at ≤24 μg/100 μL, with cell viability being decreased with increasing dust concentrations. Based on LC₅₀, house dust was less toxic than office dust. At 8 μg/100 μL, both extracts caused more MCF-7 cells into active cycling (G2/M + S) and increased intracellular Ca²⁺ influx, with house dust inducing stronger effects than office dust. Further, the expression of estrogen-responsive genes for TFF1 and EGR3 was enhanced by 3-9 and 4-9 folds, while the expression of cell cycle regulatory genes for cyclin D was enhanced by 2-5 folds. The results suggested that organic dust extract influenced cell viability, altered cell cycle, increased intracellular Ca²⁺ levels, and activated cell cycle regulatory and estrogen-responsive gene expressions, with house dust showing lower cytotoxicity but higher estrogenic potential on MCF-7 cells. The results indicate the importance of reducing organic contaminants in indoor dust to mitigate their adverse impacts on human health.

Progesterone receptor membrane component 1 regulates lipid homeostasis and drives oncogenic signaling resulting in breast cancer progression

Background

PGRMC1 (progesterone receptor membrane component 1) is a highly conserved heme binding protein, which is overexpressed especially in hormone receptor-positive breast cancer and plays an important role in breast carcinogenesis. Nevertheless, little is known about the mechanisms by which PGRMC1 drives tumor progression. The aim of our study was to investigate the involvement of PGRMC1 in cholesterol metabolism to detect new mechanisms by which PGRMC1 can increase lipid metabolism and alter cancer-related signaling pathways leading to breast cancer progression.

Methods

The effect of PGRMC1 overexpression and silencing on cellular proliferation was examined in vitro and in a xenograft mouse model.

Next, we investigated the interaction of PGRMC1 with enzymes involved in the cholesterol synthesis pathway such as CYP51, FDFT1, and SCD1. Further, the impact of PGRMC1 expression on lipid levels and expression of enzymes involved in lipid homeostasis was examined. Additionally, we assessed the role of PGRMC1 in key cancer-related signaling pathways including EGFR/HER2 and ERα signaling.

Results

Overexpression of PGRMC1 resulted in significantly enhanced proliferation. PGRMC1 interacted with key enzymes of the cholesterol synthesis pathway, alters the expression of proteins, and results in increased lipid levels. PGRMC1 also influenced lipid raft formation leading to altered expression of growth receptors in membranes of breast cancer cells. Analysis of activation of proteins revealed facilitated ERα and EGFR activation and downstream signaling dependent on PGRMC1 overexpression in hormone receptor-positive breast cancer cells. Depletion of cholesterol and fatty acids induced by statins reversed this growth benefit.

Conclusion

PGRMC1 may mediate proliferation and progression of breast cancer cells potentially by altering lipid metabolism and by activating key oncogenic signaling pathways, such as ERα expression and activation, as well as EGFR signaling. Our present study underlines the potential of PGRMC1 as a target for anti-cancer therapy.

Differential ESR1 Promoter Methylation in the Peripheral Blood-Findings from the Women 40+ Healthy Aging Study

Background Estrogen receptor α (ERα) contributes to maintaining biological processes preserving health during aging. DNA methylation changes of ERα gene (ESR1) were established as playing a direct role in the regulation of ERα levels. In this study, we hypothesized decreased DNA methylation of ESR1 associated with postmenopause, lower estradiol (E2) levels, and increased age among healthy middle-aged and older women. Methods We assessed DNA methylation of ESR1 promoter region from dried blood spots (DBSs) and E2 from saliva samples in 130 healthy women aged 40-73 years. Results We found that postmenopause and lower E2 levels were associated with lower DNA methylation of a distal regulatory region, but not with DNA methylation of proximal promoters. Conclusion Our results indicate that decreased methylation of ESR1 cytosine-phosphate-guanine island (CpGI) shore may be associated with conditions of lower E2 in older healthy women.

Metformin Promotes Anti-tumor Biomarkers in Human Endometrial Cancer Cells

Metformin (MET) is increasingly implicated in reducing the incidence of multiple cancer types in patients with diabetes. However, similar effects of MET in non-diabetic women with endometrial cancer (EC) remain unknown. In a pilot study, obese non-diabetic women diagnosed with type 1, grade 1/2 EC, and consenting to participate were randomly assigned to receive MET or no MET (control (CON)) during the pre-surgical window between diagnosis and hysterectomy. Endometrial tumors obtained at surgery (MET, n = 4; CON, n = 4) were analyzed for proliferation (Ki67), apoptosis (TUNEL), and nuclear expression of ERα, PGR, PTEN, and KLF9 proteins in tumor glandular epithelial (GE) and stromal (ST) cells. The percentages of immunopositive cells for PGR and for KLF9 in GE and for PTEN in ST were higher while those for ERα in GE but not ST were lower, in tumors of MET vs. CON patients. The numbers of Ki67- and TUNEL-positive cells in tumor GE and ST did not differ between groups. In human Ishikawa endometrial cancer cells, MET treatment (60 μM) decreased cell numbers and elicited distinct temporal changes in ESR1, KLF9, PGR, PGR-B, KLF4, DKK1, and other tumor biomarker mRNA levels. In the context of reduced KLF9 expression (by siRNA targeting), MET rapidly amplified PGR, PGR-B, and KLF4 transcript levels. Our findings suggest that MET acts directly in EC cells to modify steroid receptor expression and signaling network and may constitute a preventative strategy against EC in high-risk non-diabetic women.

Cyclical cervical function in the mare involves remodelling of collagen content, which is correlated with modification of oestrogen receptor 1 abundance

This study was conducted to elucidate mare cervical dilation mechanisms by testing two hypotheses: (i) the proportion of collagen staining in histological samples of mare cervices and (ii) the abundance of hormone receptors in the equine cervix differ with stage of the oestrous cycle and site within the cervix. Tissues and jugular vein blood samples were collected from 15 mares. Collagen content was assessed using Masson's Trichome staining. Receptor abundance was assessed using RT-PCR, qRT-PCR and immunohistochemistry. In sub-epithelial stroma, there was less collagen during the follicular than luteal phase, in the caudal- (P =  0.029), mid- (P =  0.0000) and cranial (P =  0.001) cervical tissue. In the deep stroma, there was less collagen staining during the follicular stage in the mid- (P =  0.004) and cranial- (P =  0.041) cervical regions. There were PTGER2, PTGER3, PGR and ESR1 mRNA transcripts in the cervix. A greater proportion of cells were positive for ESR1 protein during the follicular phase in sub-epithelial (P =  0.019) and deep (P =  0.013) stroma. The abundance of ESR1 in the epithelium was negatively correlated with collagen staining in sub-epithelial (P =  0.007) and deep (P =  0.005) stroma. The results of the study provide new information about the cervical biology of mares by increasing the knowledge about collagen content and the relationship between collagen content and ESR1 protein abundance during the oestrous cycle which indicates the ESR1 receptor is a candidate for involvement in control of cervical dilation.

ZBTB7A governs estrogen receptor alpha expression in breast cancer

ZBTB7A, a member of the POZ/BTB and Krüppel (POK) family of transcription factors, has been shown to have a context-dependent role in cancer development and progression. The role of ZBTB7A in estrogen receptor alpha (ERα)-positive breast cancer is largely unknown. Approximately 70% of breast cancers are classified as ERα-positive. ERα carries out the biological effects of estrogen and its expression level dictates response to endocrine therapies and prognosis for breast cancer patients. In this study, we find that ZBTB7A transcriptionally regulates ERα expression in ERα-positive breast cancer cell lines by binding to the ESR1 promoter leading to increased transcription of ERα. Inhibition of ZBTB7A in ERα-positive cells results in decreased estrogen responsiveness as demonstrated by diminished estrogen-response element-driven luciferase reporter activity, induction of estrogen target genes, and estrogen-stimulated growth. We also report that ERα potentiates ZBTB7A expression via a post-translational mechanism, suggesting the presence of a positive feedback loop between ZBTB7A and ERα, conferring sensitivity to estrogen in breast cancer. Clinically, we find that ZBTB7A and ERα are often co-expressed in breast cancers and that high ZBTB7A expression correlates with improved overall and relapse-free survival for breast cancer patients. Importantly, high ZBTB7A expression predicts a more favorable outcome for patients treated with endocrine therapies. Together, these findings demonstrate that ZBTB7A contributes to the transcriptional program maintaining ERα expression and potentially an endocrine therapy-responsive phenotype in breast cancer.

Aging women and their endothelium: probing the relative role of estrogen on vasodilator function

Despite significant decreases in cardiovascular disease (CVD) mortality in the past three decades, it still remains the leading cause of death in women. Following menopause and the accompanying loss of estrogen, women experience a unique, accelerated rise in CVD risk factors. Dysfunction of the endothelium represents an important antecedent to CVD development, with rapid declines in endothelial vasodilator function reportedly taking place across the menopause transition. Importantly, the decline in endothelial function is independent of chronological age and is associated with estrogen deficiency. Estrogen-mediated effects, including increasing nitric oxide bioavailability and attenuating oxidative stress and inflammation, contribute to preserving endothelial health. This review will discuss studies that have probed the role of estrogen on endothelial vasodilator function in women at discrete stages of the menopause transition and the effects of estradiol supplementation in postmenopausal women. Estrogen receptor signaling is also an important aspect of endothelial function in women, and studies suggest that expression is reduced with both acute and prolonged estrogen deficiency. Changes in regulatory mechanisms of estrogen receptor-α expression as well as sensitivity to estrogen may underlie the differential effects of estrogen therapy in early (≤5 yr past final menstrual period) and late postmenopausal women (>5 yr past final menstrual period). Lastly, this review presents potential therapeutic targets that include increasing l-arginine bioavailability and estrogen receptor activation to prevent endothelial dysfunction in postmenopausal women as a strategy for decreasing CVD mortality in this high-risk population.

How hormones may modulate human skin pigmentation in melasma: An in vitro perspective

Melasma is a common acquired hyperpigmentary disorder occurring primarily in photo-exposed areas and mainly affecting women of childbearing age. To decipher the role of sex hormones in melasma, this viewpoint reviews the effects of sex hormones on cutaneous cells cultured in monolayers, in coculture, in 3D models and explants in the presence or the absence of UV. The data show that sex steroid hormones, especially oestrogen, can modulate in vitro pigmentation by stimulating melanocytes and keratinocyte pro-pigmentary factors, but not via fibroblast or mast cell activation. In vitro data suggest that oestrogen acts on endothelial cell count, which may in turn increase endothelin-1 concentrations. However, data on explants revealed that sex steroid even at doses observed during pregnancy cannot induce melanogenesis alone nor melanosome transfer but that it acts in synergy with UVB. In conclusion, we hypothesize that in predisposed persons, sex steroid hormones initiate hyperpigmentation in melasma by amplifying the effects of UV on melanogenesis via direct effects on melanocytes or indirect effects via keratinocytes and on the transfer of melanosomes. They also help to sustain hyperpigmentation by increasing the number of blood vessels and, in turn, the level of endothelin-1.

Tissue steroid levels in response to reduced testicular estrogen synthesis in the male pig, Sus scrofa

Production of steroid hormones is complex and dependent upon steroidogenic enzymes, cofactors, receptors, and transporters expressed within a tissue. Collectively, these factors create an environment for tissue-specific steroid hormone profiles and potentially tissue-specific responses to drug administration. Our objective was to assess steroid production, including sulfated steroid metabolites in the boar testis, prostate, and liver following inhibition of aromatase, the enzyme that converts androgen precursors to estrogens. Boars were treated with the aromatase inhibitor, letrozole from 11 to 16 weeks of age and littermate boars received the canola oil vehicle. Steroid profiles were evaluated in testes, prostate, and livers of 16, 20, and 40 week old boars using liquid chromatography/mass spectrometry. Testis, prostate, and liver had unique steroid profiles in vehicle-treated animals. Only C18 steroid hormones were altered by treatment with the aromatase inhibitor, letrozole; no significant differences were detected in any of the C19 or C21 steroids evaluated. Testis was the only tissue with significantly decreased free estrogens following treatment with the aromatase inhibitor; estrone and estradiol concentrations were lower (p < 0.05) in testes from 16, 20, and 40 week letrozole-treated boars. However, concentrations of the sulfated conjugates, estrone-sulfate and estradiol-sulfate, were significantly decreased (p<0.05) in 16 and 20 week boar testes, prostates, and livers from letrozole-treated boars. Hence, the distribution of estrogens between the free and conjugated forms was altered in a tissue-specific manner following inhibition of aromatase. The results suggest sulfated testicular estrogens are important estrogen precursors for the prostate, potentially enabling peripheral target tissues to synthesize free estrogens in the male pig.

Neddylation Inactivation Facilitates FOXO3a Nuclear Export to Suppress Estrogen Receptor Transcription and Improve Fulvestrant Sensitivity

PURPOSE

How the neddylation pathway functions in breast tumor and regulation of estrogen receptor (ER) expression is rarely reported. The purpose of this study was to identify the role of neddylation in breast cancer and ER expression, and further explore the underlying mechanisms.

EXPERIMENTAL DESIGN

Expression patterns of nedd8-activating enzyme (NAE) and nedd8, two key proteins in the neddylation pathway, were examined in human breast specimens. ER-α expression was investigated using animal 18F-FES-PET/CT and immunoblotting upon NAE inhibitor MLN4924 treatment. Chromatin immunoprecipitation assay, luciferase reporter promoter assay, and the CRISPR-Cas9 system were used to elucidate the mechanism of ER-α regulation by MLN4924. The ER-positive breast cancer mouse model was used to determine the synergetic effect of MLN4924 and fulvestrant on tumor growth. All statistical tests were two-sided.

RESULTS

Both NAE1 and nedd8 expressions were higher in the ER-positive subgroup. Higher expressions of NAE1 and nedd8 indicated poorer prognosis. Importantly, ER-α expression was significantly downregulated upon MLN4924 treatment in vitro and in vivo. Mechanistically, MLN4924 treatment delayed serum and glucocorticoid-induced protein kinase (SGK) degradation and induced Forkhead box O3a (FOXO3a) nuclear export as well as decreased binding to the ESR1 promoter. Importantly, MLN4924 single or synergized with fulvestrant significantly suppressed the growth of ER-positive breast cancer in vitro and in vivo.

CONCLUSIONS

Our proof-of-principle study determines the activation of neddylation in breast tumor tissues for the first time and reveals a new ER-α regulatory mechanism, as well as further explores an effective approach to improve fulvestrant sensitivity through a neddylation inactivation combination.

Overview on Epigenetic Re-programming: A Potential Therapeutic Intervention in Triple Negative Breast Cancers

Breast cancer treatments leads to variable responses. Hormonal therapy is beneficial to receptor positive breast cancer subtypes and display better clinical outcome than triple negative breast cancers (TNBCs) with FEC (5-Fluorouracil, Epirubicin and Cyclophosphamide) the mainstay chemotherapy regiment. Owning to their negative expressions of estrogen (ER), progesterone (PR) and HER2 receptors, disease recurrence and metastasis befalls some patients indicating resistance to FEC. Involvement of epigenetic silencing through DNA methylation, histone methylation, acetylation and sumoylation may be the key player in FEC chemoresistance. Epigenetic and molecular profiling successfully classified breast cancer subtypes, indicating potential driver mechanisms to the progression of TNBCs but functional mechanisms behind chemoresistance of these molecular markers are not well defined. Several epigenetic inhibitors and drugs have been used in the management of cancers but these attempts are mainly beneficial in hematopoietic cancers and not specifically favourable in solid tumours. Hypothetically, upon administration of epigenetic drugs, recovery of tumour suppressor genes is expected. However, high tendency of switching on global metastatic genes is predicted. Polycomb repressive complex (PRC) such as EZH2, SETD1A, DNMT, is known to have repressive effects in gene regulation and shown to inhibit cell proliferation and invasion in breast cancers. Individual epigenetic regulators may be an option to improve chemo-drug delivery in cancers. This review discussed on molecular signatures of various breast cancer subtypes and on-going attempts in understanding underlying molecular mechanisms of epigenetic regulators as well as providing insights on possible ways to utilize epigenetic enzymes/inhibitors with responses to chemotherapeutic drugs to re-program cellular and biological outcome in TNBCs.

KRAB-containing zinc finger protein ZNF496 inhibits breast cancer cell proliferation by selectively repressing ERα activity

KRAB-containing zinc finger proteins (KZNF) constitute the largest family of transcriptional regulators in humans and play critical roles in normal development and tumorigenesis. However, the function and mechanism of most KZNFs remain unclear. Here, we report that ZNF496, a KZNF family member, interacts with the DNA binding domain (DBD) of estrogen receptor alpha (ERα) via its C2H2 domain. This interaction decreases ERα binding to chromatin DNA and results in the repression of ERα transactivation, the selective suppression of ERα target genes, and ultimately in a reduction of ERα-positive cell growth in the presence of E2. An analysis of clinical data revealed that the downregulation of ZNF496 expression is observed only in ERα-positive and not in ERα-negative breast cancer tissues when compared with that in matched adjacent tissues. Lastly, we also observed that the downregulation of ZNF496 is associated with poor recurrence-free survival among patients with breast cancer. Collectively, our findings demonstrate that ZNF496 is a novel ERα-binding protein that acts as a target gene-specific ERα corepressor and inhibits the growth of ERα-positive breast cancer cells.

The role of G-protein-coupled membrane estrogen receptor in mouse Leydig cell function-in vivo and in vitro evaluation

In this study, G-coupled estrogen receptor (GPER) was inactivated, by treatment with antagonist (G-15), in testes of C57BL/6 mice: immature (3 weeks old), mature (3 months old) and aged (1.5 years old) (50 μg/kg bw), as well as MA-10 mouse Leydig cells (10 nM/24 h) alone or in combination with 17β-estradiol or antiestrogen (ICI 182,780). In G-15-treated mice, overgrowth of interstitial tissue was found in both mature and aged testes. Depending on age, differences in structure and distribution of various Leydig cell organelles were observed. Concomitantly, modulation of activity of the mitochondria and tubulin microfibers was revealed. Diverse and complex GPER regulation at the mRNA level and protein of estrogen signaling molecules (estrogen receptor α and β; ERα, ERβ and cytochrome P450 aromatase; P450arom) in G-15 Leydig cells was found in relation to age and the experimental system utilized (in vivo and in vitro). Changes in expression patterns of ERs and P450arom, as well as steroid secretion, reflected Leydig cell heterogeneity to estrogen regulation throughout male life including cell physiological status.We show, for the first time, GPER with ERs and P450arom work in tandem to maintain Leydig cell architecture and supervise its steroidogenic function by estrogen during male life. Full set of estrogen signaling molecules, with involvement of GPER, is crucial for proper Leydig cell function where each molecule acts in a specific and/or complementary manner. Further understanding of the mechanisms by which GPER controls Leydig cells with special regard to male age, cell of origin and experimental system used is critical for predicting and preventing testis steroidogenic disorders based on perturbations in estrogen signaling.

Effects of Metformin on Cellular Proliferation and Steroid Hormone Receptors in Patient-Derived, Low-Grade Endometrial Cancer Cell Lines

Endometrial cancer (EC) is the most common gynecologic malignancy and is the result of disruption of the balance between estrogen-stimulated growth and progesterone-induced growth modulation. Metformin has been shown to inhibit EC proliferation; however, its role in early-stage EC and its effects on steroid hormone receptors have not been adequately explored. Our aim was to examine the effects of metformin on cellular proliferation in patient-derived, low-grade EC cell lines and to determine whether it directly modulates steroid hormone receptor expression. Two novel EC cell lines were produced (EM2 and 3) from endometrial tumor tissue obtained from women undergoing surgery. Cellular proliferation was determined by the 3-(4,5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide assay, and in both cell lines, metformin decreased cell proliferation in a dose-dependent (10-200 µmol/L) manner and induced apoptosis as measured by cleaved PARP. Furthermore, metformin abrogated the effects of E2 on cell proliferation. Using quantitative real-time polymerase chain reaction and Western immunoblotting, metformin significantly decreased estrogen receptor (ER) α messenger RNA abundance but did not consistently affect the expression of progesterone receptor. Estrogen receptor α protein levels significantly decreased across all metformin doses tested, which resulted in a significant decrease in the expression of the ER targets genes Keratin-19 and Wnt-1 inducible signaling pathway 2. In addition, metformin increased phosphorylation of AMPK in a dose-dependent manner (10-200 µmol/L) indicating an effect on mammalian target of rapamycin (mTOR) signaling. Our data suggest that metformin therapy represents a potential fertility-sparing option for women with early-stage EC, given its capacity to inhibit EC cell proliferation, ERα expression, and the mTOR cell proliferation pathway.

Effects of Cholinergic Lesions and Cholinesterase Inhibitors on Aromatase and Estrogen Receptor Expression in Different Regions of the Rat Brain

Cholinergic projections have been shown to interact with estrogens in ways that influence synaptic plasticity and cognitive performance. The mechanisms are not well understood. The goal of this study was to investigate whether cholinergic projections influence brain estrogen production by affecting aromatase (ARO), or influence estrogen signaling by affecting estrogen receptor expression. In the first experiment, ovariectomized rats received intraseptal injection of the selective immunotoxin 192IgG-saporin to destroy cholinergic inputs to the hippocampus. In the second experiment ovariectomized rats received daily intraperitoneal injections of the cholinesterase inhibitors donepezil or galantamine for 1 week. ARO activity and relative levels of ARO, ERα, ERß, and GPR30 mRNAs were quantified in the hippocampus, frontal cortex, amygdala and preoptic area. Results show that the cholinergic lesions effectively removed cholinergic inputs to the hippocampus, but had no significant effect on ARO or on relative levels of ER mRNAs. Likewise, injections of the cholinesterase inhibitors had no effect on ARO or ER expression in most regions of the brain. This suggests that effects of cholinergic inputs on synaptic plasticity and neuronal function are not mediated by effects on local estrogen production or ER expression. One exception was the amygdala where treating with galantamine was associated with a significant increase in ARO activity. The amygdala is a key structure involved in registering fear and anxiety. Hence this finding may be clinically relevant to elderly patients who are treated for memory impairment and who also struggle with fear and anxiety disorders.

Arctigenin inhibits the activation of the mTOR pathway, resulting in autophagic cell death and decreased ER expression in ER-positive human breast cancer cells

Arctigenin, a member of the Asteraceae family, is a biologically active lignan that is consumed worldwide due to its several health benefits. However, its use may pose a problem for patients with estrogen receptor (ER)α-positive breast cancer, since studies have shown that arctigenin is a phytoestrogen that exerts a proliferative effect by binding to the ER. Thus, in this study, we examined the effect of arctigenin on ERα-positive MCF-7 human breast cancer cells to determine whether the consumption of arctigenin is safe for patients with breast cancer. First, we found that arctigenin inhibited the viability of the MCF-7 cells, and colony formation assay confirmed that this effect was cytotoxic rather than cytostatic. The cytotoxic effects were not mediated by cell cycle arrest, apoptosis, or necroptosis, despite DNA damage, as indicated by poly(ADP-ribose) polymerase (PARP) cleavage and phosphorylated H2A.X. An increase in lipidated LC3, a marker of autophagosome formation, was observed, indicating that autophagy was induced by arctigenin, which was found to be triggered by the inhibition of the mechanistic target of rapamycin (mTOR) pathway. We then examined the effects of arctigenin on ERα expression and determined whether it affects the sensitivity of the cells to tamoxifen, as tamoxifen is commonly used against hormone-responsive cancers and is known to act via the ERα. We found that treatment with arctigenin effectively downregulated ERα expression, which was found to be a consequence of the inhibition of the mTOR pathway. However, treatment with arctigenin in combination with tamoxifen did not affect the sensitivity of the cells to tamoxifen, but instead, exerted a synergistic effect. On the whole, our data indicate that the phytoestrogen, arctigenin, mainly targeted the mTOR pathway in ERα-positive MCF-7 human breast cancer cells, leading to autophagy-induced cell death and the downregulation of ERα expression. Furthermore, the synergistic effects between arctigenin and tamoxifen suggest that the consumption of arctigenin is not only safe for patients with hormone-sensitive cancers, but may also be an effective co-treatment.

Potential interference of aluminum chlorohydrate with estrogen receptor signaling in breast cancer cells

Aluminum salts are widely used as the active antiperspirant in underarm cosmetic. Experimental observations indicate that its long term application may correlate with breast cancer development and progression. This action is proposed to be attributed, among others, to aluminum possible estrogen-like activities. In this study we showed that aluminum, in the form of aluminum chlorohydrate (ACH), caused increase in estrogen receptor alpha (ERα) protein levels, in ERα-positive MCF-7 cells. This effect was accompanied by moderate activation of Estrogen Response Elements (ERE)-driven reporter gene expression and 20%-50% increase in certain estrogen responsive, ERE-independent genes expression. Genes affected were ERα, p53, cyclin D1, and c-fos, crucial regulators of breast cancer development and progression. ACH-induced genes expression was eliminated in the presence of the estrogen antagonist: ICI 182780, in MCF-7 cells, whereas it was not observed in ERα-negative MDA-MB-231 breast cancer cells, indicating aluminum interference with estrogen signaling. Moreover, ACH caused increase in the perinuclear localization of estrogen receptor alpha in MCF-7 breast cancer cells and increase in the mitochondrial Bcl-2 protein, possibly affecting receptors-mediated mitochondrial actions and mitochondrial-dependent apoptosis. ACH-induced perinuclear localization of estrogen receptor beta was also observed in MDA-MB-231. Our findings indicate that aluminum actions on estrogen receptors protein level and subcellular localization possibly affect receptors-mediated actions and thus, aluminum interference with estrogen signaling.

Simple assay for screening phytoestrogenic compounds using the oestrogen receptor immobilised magnetite nanoparticles

With increasing interests of phytoestrogens for their potential applications, a rapid and simple tool for screening these phytochemicals is still required. In this study, a simple assay to detect phytoestrogens was developed based on the competition binding between the tested samples and the fluorescently labelled oestrogen (E2) to the human ligand binding domain of oestrogen receptor (LBD-ER) that was immobilised on the magnetite nanoparticles (MNPs). The 40-kDa LBD-ER peptide was produced in an Escherichia coli system. The synthesised 68.7-nm MNPs were silanised and subsequently covalently linked to the C-terminus of LBD-ER peptide. The LBD-ER immobilised MNPs demonstrated the specific binding for the standard E2 with the equilibrium dissociation constant of 9.56 nM and the binding capacity of 0.08 pmol/1 mg of the MNPs. The LBD-ER immobilised MNPs could evaluate oestrogenic activity of the extracts of Asparagus racemosus and Curcuma comosa, the reported phytoestrogenic plants, but not progesterone (P4) and Raphanus sativus extract, the negative controls. The results of this work clearly demonstrated a potential assay for detecting phytoestrogens of crude plant extracts, which is simple and easily adapted to a high throughput format.

Spatiotemporal expression analysis of nuclear estrogen receptors in the zebrafish ovary and their regulation in vitro by endocrine hormones and paracrine factors

Estradiol (E2) stimulates luteinizing hormone receptor (lhcgr) expression via nuclear estrogen receptors (nERs) in the zebrafish ovary. We have demonstrated that endocrine hormones such as gonadotropin (hCG) and paracrine factors such as epidermal growth factor (EGF) and pituitary adenylate cyclase-activating peptide (PACAP) can modulate E2-induced lhcgr expression in vitro. These observations raised a question on whether these hormones and factors exert their effects via regulating the expression of nERs. In this study, we first characterized the spatiotemporal expression profiles of three nER subtypes in the zebrafish ovary, including esr1 (ERα), esr2a (ERβ2) and esr2b (ERβ1). All three nERs increased their expression at the pre-vitellogenic stage and peaked at mid- (esr1 and esr2a) or late vitellogenic (esr2b) stage, followed by a significant decline at the full-grown stage. RT-PCR analysis showed that esr1 and esr2b were exclusively expressed in the follicle layer while esr2a was expressed in both compartments. We then examined how E2, hCG, PACAP and EGF regulated the expression of nERs in cultured zebrafish follicle cells. E2 quickly increased esr1 but reduced esr2a and esr2b expression from 1.5 to 12h of treatment. Similarly, EGF down-regulated esr2a significantly at 1.5h and this effect was further intensified at 24h. hCG decreased the expression of all three nER subtypes with similar potency throughout the 24-h time-course. Interestingly, PACAP exerted a biphasic regulation on esr2a. Our present study suggests that nERs, especially esr2a, provide potential target points for other hormones and factors to modulate E2 activity during folliculogenesis in the zebrafish.

The zinc-finger transcriptional factor Slug transcriptionally downregulates ERα by recruiting lysine-specific demethylase 1 in human breast cancer

Estrogen receptor α (ERα) is related with epithelial-mesenchymal transition, invasion and metastasis, and serves as an important therapeutic predictor and prognostic factor in breast cancer patients. The triple negative breast cancer (TNBC) is characterized by loss of hormone receptors and human epidermal growth factor receptor 2 (Her2), and lacks effective targeted therapy with poor prognosis. Unfortunately, the molecular mechanisms of ERα deficiency, which becomes hormone independent and results in resistance to endocrine therapy, remain to be elucidated in breast cancer. In this study, we observed an inverse correlation between Slug, a zinc-finger transcriptional repressor, and ERα expression in both human breast cancer tissues and cell lines. In ERα-negative breast cancer patients, high Slug messenger RNA expression showed obviously shorter relapse-free survival. We found that Slug binds to the E-box located in the promoter of estrogen receptor 1 gene (ESR1) to suppress its expression. More specifically, Slug recruits lysine-specific demethylase 1 (LSD1) to the E-box and thereby inhibits ERα expression by demethylating H3K4me2, which is evidenced by the interaction between Slug and LSD1. Moreover, the amount of H3K4me2 binding to the E-box was significantly increased after LSD1 knockdown in MDA-MB-231 cells. Functionally, the ability to proliferate, invade and metastasize was significantly suppressed after knockdown of either Slug or LSD1 alone, or both simultaneously. Taken together, these results suggest that Slug transcriptionally inhibits ERα expression by recruiting LSD1 to the ESR1 promoter in breast cancers. Thus, targeted inhibition of Slug and LSD1 may restore ERα and lead to resensitization to hormone therapy, providing a novel therapeutic strategy for ERα-negative breast cancer patients, especially for TNBC.

Downregulation of estrogen receptor and modulation of growth of breast cancer cell lines mediated by paracrine stromal cell signals

PURPOSE

Breast cancers have a poorer prognosis if estrogen receptor expression was lost during recurrence. It is unclear whether this conversion is cell autonomous or whether it can be promoted by the microenvironment during cancer dormancy. We explored the ability of marrow-derived stromal cell lines to arrest co-cultured breast cancer cells and suppress estrogen receptor alpha (ER) expression during arrest, facilitating the emergence of estrogen-independent breast cancer clones.

METHODS

Cancer cell growth, ER protein, microRNA, and mRNA levels were measured in breast cancer cell lines exposed to conditioned medium from marrow stromal lines in the presence and absence of estrogen and of signaling pathway modulators.

RESULTS

We demonstrate that paracrine signaling from the stromal cell line HS5 downregulated ER in T47D and MCF7 breast cancer cells. This occurred at the mRNA level and also through decreased ER protein stability. Additionally, conditioned medium (CM) from HS5 arrested the breast cancer cells in G0/G1 in part through interleukin-1 (IL1) and inhibited cancer cell growth despite the activation of proliferative pathways (Erk and AKT) by the CM. Similar findings were observed for CM from the hFOB 1.19 osteoblastic cell line but not from two other fibroblastic marrow lines, HS27A and KM101. HS5-CM inhibition of MCF7 proliferation could not be restored by exogenous ER, but was restored by the IL1-antagonist IL1RA. In the presence of IL1RA, HS5-CM activation of AKT and Erk enabled the outgrowth of breast cancer cells with suppressed ER that were fulvestrant-resistant and estrogen-independent.

CONCLUSIONS

We conclude that marrow-derived stromal cells can destabilize estrogen receptor protein to convert the ER status of growth-arrested ER+ breast cancer cell lines. The balance between stromal pro- and anti-proliferative signals controlled the switch from a dormant phenotype to estrogen-independent cancer cell growth.

Associations of persistent organic pollutants in serum and adipose tissue with breast cancer prognostic markers

This study aimed to evaluate associations between exposure to a group of persistent organic pollutants, measured in both adipose tissue and serum samples from breast cancer patients, and a set of tumor prognostic markers. The study population comprised 103 breast cancer patients recruited in Granada, Southern Spain. Data for tumor prognostic markers were retrieved from hospital clinical records and socio-demographic information was gathered by questionnaire. Persistent organic pollutants were quantified by gas chromatography with electron capture detection. Exposure levels were categorized in quartiles, and associations were evaluated using unconditional logistic regression. Adipose tissue HCB concentrations were associated positively with ER and PR expression (p-trends=0.044 and 0.005, respectively) and negatively with E-Cadherin and p53 expression (p-trends=0.012 and 0.027, respectively). PCB-180 adipose tissue concentrations were positively associated with HER2 expression (p-trend=0.036). Serum PCB-138 concentrations were positively associated with ER and PR expression (p-trends=0.052 and 0.042, respectively). The risk of p53 expression was higher among women in the lowest quartile of serum PCB-138 concentrations, but no significant trend was observed (p-trend=0.161). These findings indicate that human exposure to certain persistent organic pollutants might be related to breast cancer aggressiveness. We also highlight the influence on exposure assessment of the biological matrix selected, given that both serum and adipose tissue might yield relevant information on breast cancer prognosis.

Epigenetic regulation of estrogen receptor α contributes to age-related differences in transcription across the hippocampal regions CA1 and CA3

The expression of estrogen receptor alpha (ERα) varies across brain regions and changes with age and according to the previous history of estradiol exposure. ERα is regulated by a number of mechanisms including the level of mRNA (Esr1) expression. For this study, we took advantage of regional differences in hippocampal ERα expression to investigate DNA ERα promoter methylation at CpG dinucleotide sites as a potential epigenetic mechanism for regulating gene expression. Young and aged female Fischer 344 rats were ovariectomized, and Esr1 expression and ERα promoter methylation were examined in hippocampal regions CA1 and CA3, either 3 or 14 weeks following surgery. The results indicate that reduced Esr1 expression in region CA1 relative to CA3 was associated with an increase in DNA methylation in region CA1, particularly for the first CpG site. Additionally, differential methylation of distal CpG sites, 11-17, was associated with altered Esr1 expression during aging or following long-term hormone deprivation. The results support the idea that methylation of site 1 may be the primary regulatory region for cross-regional patterns in ERα expression, while distal sites are modifiable across the life span and may act as a feedback mechanism for ERα activity.

Beta protein 1 homeoprotein induces cell growth and estrogen-independent tumorigenesis by binding to the estrogen receptor in breast cancer

Expression of Beta Protein 1 (BP1), a homeotic transcription factor, increases during breast cancer progression and may be associated with tumor aggressiveness. In our present work, we investigate the influence of BP1 on breast tumor formation and size in vitro and in vivo. Cells overexpressing BP1 showed higher viability when grown in the absence of serum (p < 0.05), greater invasive potential (p < 0.05) and formed larger colonies (p < 0.004) compared with the controls. To determine the influence of BP1 overexpression on tumor characteristics, MCF-7 cells transfected with either empty vector (V1) or overexpressor plasmids (O2 and O4) were injected into the fat pads of athymic nude mice. Tumors grew larger in mice receiving O2 or O4 cells than in mice receiving V1 cells. Moreover, BP1 mRNA expression levels were positively correlated with tumor size in patients (p = 0.01). Interestingly, 20% of mice injected with O2 or O4 cells developed tumors in the absence of estrogen, while no mice receiving V1 cells developed tumors. Several mechanisms of estrogen independent tumor formation related to BP1 were established. These data are consistent with the fact that expression of breast cancer anti-estrogen resistance 1 (BCAR1) was increased in O2 compared to V1 cells (p < 0.01). Importantly, O2 cells exhibited increased proliferation when treated with tamoxifen, while V1 cells showed growth inhibition. Overall, BP1 overexpresssion in MCF-7 breast cancer cells leads to increased cell growth, estrogen-independent tumor formation, and increased proliferation. These findings suggest that BP1 may be an important biomarker and therapeutic target in ER positive breast cancer.

The Estrogen Receptor α-Cistrome Beyond Breast Cancer

Although many tissues express estrogen receptor (ER)α, most studies focus on breast cancer where ERα occupies just a small fraction of its total repertoire of potential DNA-binding sites, based on sequence. This raises the question: Can ERα occupy these other potential binding sites in a different context? Ligands, splice variants, posttranslational modifications, and acquired mutations of ERα affect its conformation, which may alter chromatin interactions. To date, literature describes the DNA-binding sites of ERα (the ERα cistrome) in breast, endometrium, liver, and bone, in which the receptor mainly binds to enhancers. Chromosomal boundaries provide distinct areas for dynamic gene regulation between tissues, where the usage of enhancers deviates. Interactions of ERα with enhancers and its transcriptional complex depend on the proteome, which differs per cell type. This review discusses the biological variables that influence ERα cistromics, using reports from human specimens, cell lines, and mouse tissues, to assess whether ERα genomics in breast cancer can be translated to other tissue types.

Oncogenic AKT1(E17K) mutation induces mammary hyperplasia but prevents HER2-driven tumorigenesis

One of the most frequently deregulated signaling pathways in breast cancer is the PI 3-K/Akt cascade. Genetic lesions are commonly found in PIK3CA, PTEN, and AKT, which lead to excessive and constitutive activation of Akt and downstream signaling that results in uncontrolled proliferation and increased cellular survival. One such genetic lesion is the somatic AKT1(E17K) mutation, which has been identified in 4-8% of breast cancer patients. To determine how this mutation contributes to mammary tumorigenesis, we constructed a genetically engineered mouse model that conditionally expresses human AKT1(E17K) in the mammary epithelium. Although AKT1(E17K) is only weakly constitutively active and does not promote proliferation in vitro, it is capable of escaping negative feedback inhibition to exhibit sustained signaling dynamics in vitro. Consistently, both virgin and multiparous AKT1(E17K) mice develop mammary gland hyperplasia that do not progress to carcinoma. This hyperplasia is accompanied by increased estrogen receptor expression, although exposure of the mice to estrogen does not promote tumor development. Moreover, AKT1(E17K) prevents HER2-driven mammary tumor formation, in part through negative feedback inhibition of RTK signaling. Analysis of TCGA breast cancer data revealed that the mRNA expression, total protein levels, and phosphorylation of various RTKs are decreased in human tumors harboring AKT1(E17K).

Regulation of gene expression by 17β-estradiol in the arcuate nucleus of the mouse through ERE-dependent and ERE-independent mechanisms

17β-Estradiol (E2) modulates gene expression in the hypothalamic arcuate nucleus (ARC) to control homeostatic functions. In the ARC, estrogen receptor (ER) α is highly expressed and is an important contributor to E2's actions, controlling gene expression through estrogen response element (ERE)-dependent and -independent mechanisms. The objective of this study was to determine if known E2-regulated genes are regulated through these mechanisms. The selected genes have been shown to regulate homeostasis and have been separated into three subsections: channels, receptors, and neuropeptides. To determine if ERE-dependent or ERE-independent mechanisms regulate gene expression, two transgenic mouse models, an ERα knock-out (ERKO) and an ERα knock-in/knock-out (KIKO), which lacks a functional ERE binding domain, were used in addition to their wild-type littermates. Females of all genotypes were ovariectomized and injected with oil or estradiol benzoate (E2B). Our results suggest that E2B regulates multiple genes through these mechanisms. Of note, Cacna1g and Kcnmb1 channel expression was increased by E2B in WT females only, suggesting an ERE-dependent regulation. Furthermore, the NKB receptor, Tac3r, was suppressed by E2B in WT and KIKO females but not ERKO females, suggesting that ERα-dependent, ERE-independent signaling is necessary for Tac3r regulation. The adrenergic receptor Adra1b was suppressed by E2B in all genotypes indicating that ERα is not the primary receptor for E2B's actions. The neuropeptide Tac2 was suppressed by E2B through ERE-dependent mechanisms. These results indicate that E2B activates both ERα-dependent and independent signaling in the ARC through ERE-dependent and ERE-independent mechanisms to control gene expression.

The Expanding Complexity of Estrogen Receptor Signaling in the Cardiovascular System

Estrogen has important effects on cardiovascular function including regulation of vascular function, blood pressure, endothelial relaxation, and the development of hypertrophy and cardioprotection. However, the mechanisms by which estrogen mediates these effects are still poorly understood. As detailed in this review, estrogen can regulate transcription by binding to 2 nuclear receptors, ERα and ERβ, which differentially regulate gene transcription. ERα and ERβ regulation of gene transcription is further modulated by tissue-specific coactivators and corepressors. Estrogen can bind to ERα and ERβ localized at the plasma membrane as well as G-protein-coupled estrogen receptor to initiate membrane delimited signaling, which enhances kinase signaling pathways that can have acute and long-term effects. The kinase signaling pathways can also mediate transcriptional changes and can synergize with the ER to regulate cell function. This review will summarize the beneficial effects of estrogen in protecting the cardiovascular system through ER-dependent mechanisms with an emphasis on the role of the recently described ER membrane signaling mechanisms.

Interplay of estrogen receptors and FOXA factors in the liver cancer

Liver cancer is the fifth most common cancer in human with male dominance. Sexual dimorphism of liver cancer is conserved from rodents to humans, which was firstly found in mice in late 1930s and female mice were resistant to liver cancer. Sex hormones were found to affect the incidence of liver cancer in rodents. Estrogen receptor alpha (ERα)-mediated estrogen signaling or androgen receptor-mediated androgen signaling prevents or promotes the growth of rodent liver tumors, respectively. Forkhead box protein A (Foxa) factors, Foxa1 and Foxa2, also known as pioneer transcription factors in liver specification, are essential for both estrogen and androgen signaling by acting as central regulators of sexual dimorphism in liver cancer. This review mainly focuses on the interplay between ERα and FOXA factors in liver cancer, and summarizes recent breakthrough studies in elucidating the mechanisms of sexual dimorphism in liver cancer.

An immunohistochemical study on the expression of sex steroid receptors, Ki-67 and cytokeratins 7 and 20 in feline endometrial adenocarcinomas

BACKGROUND

Endometrial adenocarcinomas are a rare type of tumour in cats. Though different morphologies have been reported, the most frequent histological type of feline endometrial adenocarcinoma (FEA) is the papillary serous. Characterization of molecular markers expression in FEA may contribute to clarify the pathogenesis of these tumours and to assess the differences between normal endometrium and FEA regarding the expression pattern of several proteins. Therefore, this study aimed to evaluate the immunohistochemical profile of a wide panel of antibodies (specific for ER-α, PR, Ki-67, CK7 and CK20) in twenty-four cases of FEA. Comparisons were made between FEA and feline normal cyclic endometrium in follicular (n = 13) and luteal (n = 10) stages. Except for Ki-67, all other molecular markers were assessed independently for the intensity of immunolabeling and for the percentage of cells expressing the protein.

RESULTS

This study showed that in FEA a loss of expression occurs for ER-α (P ≤ 0.0001) and less markedly also for PR. The lost in sex steroid receptors concerns a decrease in both the proportion of labelled cells and the intensity of immunolabelling (P = 0.002 and P = 0.024, respectively). Proliferative activity, estimated via Ki-67 immunoreaction, significantly increased in FEA as compared to normal endometrium (P ≤ 0.0001). Feline endometrial adenocarcinomas maintained the CK7+/CK20+ status of normal endometrium. However, FEA showed decreased CK7 intensity of labelling compared to normal endometria (P ≤ 0.0001) and loss of CK20 expression, both in intensity (P ≤ 0.0001) and in percentage of positive cells (P = 0.01), compared to normal tissues.

CONCLUSIONS

Data gathered in this study suggest that proliferation in FEA accompanies ER-α down-regulation, possibly following activation of pathways mediated by local growth factors. Moreover, FEA retains combined expression of CK7 and CK20, as evidenced in normal endometrial epithelia, although a decrease in CK7 expression was observed.

The BCL9-2 proto-oncogene governs estrogen receptor alpha expression in breast tumorigenesis

The majority of human breast cancers express estrogen receptor alpha (ER), which is important for therapy with anti-estrogens. Here we describe the role of BCL9-2, a proto-oncogene previously characterized as co-activator of Wnt/ß-catenin signaling, for mammary tumorigenesis in mice and human. ER positive human breast cancers showed overexpression of BCL9-2 and tamoxifen treated patients with high BCL9-2 demonstrated a better survival. BCL9-2 was upregulated during puberty and pregnancy in normal mammary epithelia, but downregulated in the involuted gland. BCL9-2 overexpression in vivo delayed the mammary involution and induced alveolar hyperplasia. Moreover, aged BCL9-2 transgenic mice developed ductal-like mammary tumors with high nuclear ER expression. We found, that primary cell cultures of BCL9-2 breast tumors responded to tamoxifen treatment. Moreover, BCL9-2 regulated the expression of ER and the proliferation of human breast cancer cells independently of ß-catenin. Finally, we describe a novel mechanism, how BCL9-2 regulates ER transcription by interaction with Sp1 through the proximal ESR1 gene promoter. In summary, BCL9-2 induces ER positive breast cancers in vivo, regulates ER expression by a novel ß-catenin independent mechanism in breast cancer cells, and might predict the therapy response to tamoxifen treatment.

Hypoxia Represses ER-α Expression and Inhibits Estrogen-Induced Regulation of Ca2+-Activated K+ Channel Activity and Myogenic Tone in Ovine Uterine Arteries: Causal Role of DNA Methylation

Previous in vivo study demonstrated that chronic hypoxia during gestation was associated with estrogen receptor-α (ER-α) gene repression in ovine uterine arteries. Yet, it remains undetermined whether hypoxia had a direct effect and if DNA methylation played a causal role in hypoxia-mediated ER-α gene repression. Thus, this study tested the hypothesis that prolonged hypoxia has a direct effect and increases promoter methylation resulting in ER-α gene repression and inhibition of estrogen-mediated adaptation of uterine vascular tone. Uterine arteries isolated from nonpregnant and pregnant sheep were treated ex vivo with 21.0% O2 and 10.5% O2 for 48 hours. Hypoxia significantly increased ER-α promoter methylation at both specificity protein-1 and upstream stimulatory factor binding sites, decreased specificity protein-1 and upstream stimulatory factor binding to the promoter, and suppressed ER-α expression in uterine arteries of pregnant animals. Of importance, the effects of hypoxia were blocked by a methylation inhibitor 5-aza-2'-deoxycytidine. In addition, hypoxia abrogated steroid hormone-mediated increase in ER-α expression and inhibited the hormone-induced increase in large-conductance Ca(2+)-activated K(+) channel activity and decrease in myogenic tone in uterine arteries of nonpregnant animals, which were reversed by 5-aza-2'-deoxycytidine. The results provide novel evidence of a direct effect of hypoxia on heightened promoter methylation that plays a causal role in ER-α gene repression and ablation of steroid hormone-mediated adaptation of uterine arterial large conductance Ca(2+)-activated K(+) channel activity and myogenic tone in pregnancy.

Estrogen receptor-α: molecular mechanisms and interactions with the ubiquitin proteasome system

Estrogen receptor-α (ERα) is a protein with a long history of study that precedes the advent of modern molecular biology. Over the course of 50 years, ERα has been increasingly recognized as a prominent model for the study of the mechanism of gene transcription in vertebrates. It also serves as a regulatory molecule for numerous physiological and disease states. Several fundamental insights have been made using ERα as a model protein, from the discovery that endocrine hormones elicit gene transcription to our understanding of the relationship between ERα-mediated transcription and transcription factor degradation by the ubiquitin proteasome system (UPS). Understanding of receptor protein degradation developed alongside other aspects of its molecular biology, from early observations in the 1960s that ERα is degraded on hormone treatment to the current understanding of ERα transcriptional regulation by the UPS. Here, we present the concept of ERα turnover from the perspective of the historical development of this notion and highlight some of the latest discoveries regarding this process. We discuss the logic and significance of ERα degradation pathways in the context of cell and whole-organism homeostasis.