Cloning and characterization of human estrogen receptor beta isoforms

Estrogen receptor beta expression and role in cancers

Estrogen drives the growth of some cancers, such as breast cancer, via estrogen receptor alpha (ERα). Estrogen also activates ERβ, but whether ERβ is expressed and has a role in different cancers is debated. The use of nonspecific antibodies has contributed to the confusion, and this review delves into ERβ's controversial role in cancer and focuses on tumor expression that can be supported by non-antibody-dependent assays. We discuss its expression at the transcript level and focus on its potential role in lymphoma, granulosa cell tumors, testicular, and adrenal cancers, emphasizing recent findings and the complexities that necessitate further research.

Estrogen Receptor α Isoforms Generated by Alternative Use of Cryptic Exons

Estrogen receptor α (ERα) regulates several physiological functions. In pathophysiological conditions, ERα is involved in the development and progression of estrogen-sensitive tumors. The ERα gene contains multiple 5'-untranslated exons and eight conventional coding exons and presents multiple isoforms generated by alternative promoter usage and alternative splicing. This gene also possesses non-conventional exons in the 3'- and intronic regions, and alternative use of cryptic exons contributes to further diversity of ERα mRNAs and proteins. Recently, the genomic organization of ERα genes and the splicing profiles of their transcripts were comparatively analyzed in humans, mice, and rats, and multiple ERα isoforms with distinct structures and functions were identified. These transcripts contain cryptic sequences that encode insertion-containing or truncated ERα proteins. In particular, alternative cryptic exons with in-frame stop codons yield transcripts encoding C-terminally-truncated ERα proteins. The C-terminally-truncated ERα isoforms lack part or all of the ligand-binding domain but possess an isoform-specific sequence. Some of these isoforms exhibit constitutive transactivation and resistance to estrogen receptor antagonists. Although numerous studies have reported conflicting results regarding their functions, the critical determinant for their gain-of-function has been identified structurally. Here we review recent progress in ERα variant research concerning the genomic organization of ERα genes, splicing profiles of ERα transcripts, and transactivation properties of ERα isoforms.

Divergent features of ERβ isoforms in triple negative breast cancer: progress and implications for further research

Estrogen receptor β (ERβ) was discovered more than 20 years ago. However, the extent and role of ERβ expression in breast cancer remain controversial, especially in the context of triple-negative breast cancer (TNBC). ERβ exists as multiple isoforms, and a series of studies has revealed an inconsistent role of ERβ isoforms in TNBC. Our recent results demonstrated contrasting functions of ERβ1 and ERβ2/β5 in TNBC. Additional research should be conducted to explore the functions of individual ERβ isoforms and develop targeted drugs according to the relevant mechanisms. Consequently, a systematic review of ERβ isoforms is necessary. In this review, we overview the structure of ERβ isoforms and detail what is known about the function of ERβ isoforms in normal mammary tissue and breast cancer. Moreover, this review highlights the divergent features of ERβ isoforms in TNBC. This review also provides insights into the implications of targeting ERβ isoforms for clinical treatment. In conclusion, this review provides a framework delineating the roles and mechanisms of different ERβ isoforms in TNBC and sheds light on future directions for basic and clinical research.

The increased risk of colorectal cancer in the women who underwent hysterectomy from the South Korean National Health Insurance Database

BACKGROUND

Several population-based studies and observational studies have shown that oophorectomy is associated with an increased risk of colorectal cancer (CRC), and hormone replacement therapy has been associated with a reduction in the risk of colorectal cancer. This study was carried out to investigate whether hysterectomy, which may affect the levels of female hormones, is associated with a risk of cancer of the specific gastrointestinal tract.

METHODS

This population-based retrospective cohort study was conducted using insurance data provided by the Health Insurance Review and Assessment Service (HIRA) from January 1, 2007, to December 31, 2020. The hysterectomy group included 40- to 59-year-old women who underwent hysterectomy with uterine leiomyoma or uterine endometriosis from January 1, 2011, to December 31, 2014. The control group included women aged 40 to 59 years who visited medical institutions for medical examination from January 1, 2011 to December 31, 2014.

RESULTS

The hysterectomy and non-hysterectomhy groups comprised 66,204 and 89,768 subjects, respectively. The median ages in the non-hysterectomy group and hysterectomy group were 48 (range: 43-53) and 46 (range: 44-49) years, respectively. In the unadjusted results of the analysis, all colorectal cancer (CRC) increased in the hysterectomy alone group (HR 1.222, 95% confidence interval (CI) 1.016-1.47, p = 0.033), sigmoid colon cancer increased in the hysterectomy alone group (HR 1.71, 95% CI 1.073-2.724, p = 0.024), and rectal cancer increased in the hysterectomy with adnexal surgery group (HR 1.924, 95% CI 1.073-2.724, p = 0.002). The adjusted results showed that all CRC increased in the hysterectomy alone group (HR 1.406, 95% CI 1.057-1.871, p = 0.019), colon cancer increased in the hysterectomy alone group (HR 1.523, 95% CI 1.068-2.17, p = 0.02), and rectal cancer increased in the hysterectomy with adnexal surgery group (HR 1.933, 95% CI 1.131-3.302, p = 0.016). The all-cause mortality of GI cancer increased in the hysterectomy alone group (HR 3.495, 95% CI 1.347-9.07, p = 0.001).

CONCLUSIONS

This study showed that the risk of all CRC increased in women who underwent hysterectomy compared with women who did not. In particular, the risk of rectal cancer was significantly higher in the women who underwent hysterectomy with adnexal surgery than in the controls. There was no association between hysterectomy and other GI cancers.

Estrogen Receptor Signaling in Breast Cancer

Estrogen receptor (ER) signaling is a critical regulator of cell proliferation, differentiation, and survival in breast cancer (BC) and other hormone-sensitive cancers. In this review, we explore the mechanism of ER-dependent downstream signaling in BC and the role of estrogens as growth factors necessary for cancer invasion and dissemination. The significance of the clinical implications of ER signaling in BC, including the potential of endocrine therapies that target estrogens' synthesis and ER-dependent signal transmission, such as aromatase inhibitors or selective estrogen receptor modulators, is discussed. As a consequence, the challenges associated with the resistance to these therapies resulting from acquired ER mutations and potential strategies to overcome them are the critical point for the new treatment strategies' development.

Nuclear Estrogen Receptors in Prostate Cancer: From Genes to Function

Estrogens are almost ubiquitous steroid hormones that are essential for development, metabolism, and reproduction. They exert both genomic and non-genomic action through two nuclear receptors (ERα and ERβ), which are transcription factors with disregulated functions and/or expression in pathological processes. In the 1990s, the discovery of an additional membrane estrogen G-protein-coupled receptor augmented the complexity of this picture. Increasing evidence elucidating the specific molecular mechanisms of action and opposing effects of ERα and Erβ was reported in the context of prostate cancer treatment, where these issues are increasingly investigated. Although new approaches improved the efficacy of clinical therapies thanks to the development of new molecules targeting specifically estrogen receptors and used in combination with immunotherapy, more efforts are needed to overcome the main drawbacks, and resistance events will be a challenge in the coming years. This review summarizes the state-of-the-art on ERα and ERβ mechanisms of action in prostate cancer and promising future therapies.

Trends in estrogen and progesterone receptors in prostate cancer: a bibliometric analysis

Introduction

The bibliometric analysis aims to identify research trends in estrogen receptor (ERs) and progesterone receptor (PRs) in prostate cancer (PCa), and also discuss the hotspots and directions of this field.

Methods

835 publications were sourced from the Web of Science database (WOS) from 2003 to 2022. Citespace, VOSviewer, and Bibliometrix were used for the bibliometric analysis.

Results

The number of published publications increased in early years, but declined in the last 5 years. The United States was the leading country in citations, publications, and top institutions. Prostate and Karolinska Institutet were the most publications of journal and institution, respectively. Jan-Ake Gustafsson was the most influential author based on the number of citations/publications. The most cited paper was "Estrogen receptors and human disease" by Deroo BJ, published in the Journal of Clinical Investigation. The most frequently used keywords were PCa (n = 499), gene-expression (n = 291), androgen receptor (AR) (n = 263), and ER (n = 341), while ERb (n = 219) and ERa (n = 215) further emphasized the importance of ER.

Conclusions

This study provides useful guidance that ERa antagonists, ERb agonists, and the combination of estrogen with androgen deprivation therapy (ADT) will potentially serve as a new treatment strategy for PCa. Another interesting topic is relationships between PCa and the function and mechanism of action of PRs subtypes. The outcome will assist scholars in gaining a comprehensive understanding of the current status and trends in the field, and provide inspiration for future research.

Estrogen Receptor β4 Regulates Chemotherapy Resistance and Induces Cancer Stem Cells in Triple Negative Breast Cancer

Triple Negative Breast Cancer (TNBC) has the worst prognosis among all breast cancers, and survival in patients with recurrence is rarely beyond 12 months due to acquired resistance to chemotherapy, which is the standard of care for these patients. Our hypothesis is that Estrogen Receptor β1 (ERβ1) increases response to chemotherapy but is opposed by ERβ4, which it preferentially dimerizes with. The role of ERβ1 and ERβ4 in influencing chemotherapy sensitivity has never been studied before. CRISPR/CAS9 was used to truncate ERβ1 Ligand Binding Domain (LBD) and knock down the exon unique to ERβ4. We show that the truncated ERβ1 LBD in a variety of mutant p53 TNBC cell lines, where ERβ1 ligand dependent function was inactivated, had increased resistance to Paclitaxel, whereas the ERβ4 knockdown cell line was sensitized to Paclitaxel. We further show that ERβ1 LBD truncation, as well as treatment with ERβ1 antagonist 2-phenyl-3-(4-hydroxyphenyl)-5,7-bis(trifluoromethyl)-pyrazolo[1,5-a] pyrimidine (PHTPP), leads to increase in the drug efflux transporters. Hypoxia Inducible Factors (HIFs) activate factors involved in pluripotency and regulate the stem cell phenotype, both in normal and cancer cells. Here we show that the ERβ1 and ERβ4 regulate these stem cell markers like SOX2, OCT4, and Nanog in an opposing manner; and we further show that this regulation is mediated by HIFs. We show the increase of cancer cell stemness due to ERβ1 LBD truncation is attenuated when HIF1/2α is knocked down by siRNA. Finally, we show an increase in the breast cancer stem cell population due to ERβ1 antagonist using both ALDEFLUOR^TM and SOX2/OCT4 response element (SORE6) reporters in SUM159 and MDA-MB-231 cell lines. Since most TNBC cancers are ERβ4 positive, while only a small proportion of TNBC patients are ERβ1 positive, we believe that simultaneous activation of ERβ1 with agonists and inactivation of ERβ4, in combination with paclitaxel, can be more efficacious and yield better outcome for chemotherapy resistant TNBC patients.

Estrogen Receptor-β Gene Cytosine-Adenine (ESR2-CA) Repeat Polymorphism in Postmenopausal Colon Cancer

The pathobiological role of estrogen is controversial in colorectal cancer. Cytosine-adenine (CA) repeat in the estrogen receptor (ER)-β gene (ESR2-CA) is a microsatellite, as well as representative of ESR2 polymorphism. Though its function is unknown, we previously showed that a shorter allele (germline) increased the risk of colon cancer in older women, whereas it decreased it in younger postmenopausal women. ESR2-CA and ER-β expressions were examined in cancerous (Ca) and non-cancerous (NonCa) tissue pairs from 114 postmenopausal women, and comparisons were made considering tissue types, age/locus, and the mismatch repair protein (MMR) status. ESR2-CA repeats <22/≥22 were designated as 'S'/'L', respectively, resulting in genotypes SS/nSS (=SL&LL). In NonCa, the rate of the SS genotype and ER-β expression level were significantly higher in right-sided cases of women ≥70 (≥70Rt) than in those in the others. A decreased ER-β expression in Ca compared with NonCa was observed in proficient-MMR, but not in deficient-MMR. In NonCa, but not in Ca, ER-β expression was significantly higher in SS than in nSS. ≥70Rt cases were characterized by NonCa with a high rate of SS genotype or high ER-β expression. The germline ESR2-CA genotype and resulting ER-β expression were considered to affect the clinical characteristics (age/locus/MMR status) of colon cancer, supporting our previous findings.

Human cell-based estrogen receptor beta dimerization assay

Estrogen is not only responsible for important functions in the human body, such as cell growth, reproduction, differentiation, and development, but it is also deeply related to pathological processes, such as cancer, metabolic and cardiovascular diseases, and neurodegeneration. Estrogens and other estrogenic compounds have transcriptional activities through binding with the estrogen receptor (ER) to induce ER dimerization. The two estrogen receptor subtypes, estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), show structural differences and have different expression ratios in specific cells and tissues. Currently, the methods for confirming the estrogenic properties of compounds are the binding (Test guideline no. 493) and transactivation (Test guideline no. 455) assays provided by the Organization for Economic Co-operation and Development (OECD). In a previous study, we developed an ERα dimerization assay based on the bioluminescence resonance energy transfer (BRET) system, but there are currently no available tests that can confirm the effect of estrogenic compounds on ERβ. Therefore, in this study, we developed a BRET-based ERβ dimerization assay to confirm the estrogenic prosperities of compounds. The BRET-based ERβ dimerization assay was verified using nine representative ER ligands and the results were compared with the dimerization activity of ERα. In conclusion, our BRET-based ERβ dimerization assay can provide information on the ERβ dimerization potential of estrogenic compounds.

An overview on Estrogen receptors signaling and its ligands in breast cancer

Estrogen governs the regulations of various pathological and physiological actions throughout the body in both males and females. Generally, 17β-estradiol an endogenous estrogen is responsible for different health problems in pre and postmenopausal women. The major activities of endogenous estrogen are executed by nuclear estrogen receptors (ERs) ERα and ERβ while non-genomic cytoplasmic pathways also govern cell growth and apoptosis. Estrogen accomplished a fundamental role in the formation and progression of breast cancer. In this review, we have hyphenated different studies regarding ERs and a thorough and detailed study of estrogen receptors is presented. This review highlights different aspects of estrogens ranging from receptor types, their isoforms, structures, signaling pathways of ERα, ERβ and GPER along with their crystal structures, pathological roles of ER, ER ligands, and therapeutic strategies to overcome the resistance.

The Isoforms of Estrogen Receptor Alpha and Beta in Thyroid Cancer

The incidence of thyroid cancer was predominant in women, indicating that the sex hormone may have a role in thyroid cancer development. Generally, the sex hormone exerts its function by binding to the correspondent nuclear receptors. Therefore, aberrant of these receptors may be involved in the development of thyroid cancer. Estrogen receptor alpha (ERα) and beta (ERβ), two main estrogen receptors, have been reported to have an important role in the pathogenesis of thyroid cancer. When the ERα and ERβ genes undergo the alternative RNA splicing, some ERα and ERβ isoforms with incomplete functional domains may be formed. To date, several isoforms of ERα and ERβ have been identified. However, their expression and roles in thyroid cancer are far from clear. In this review, we summarized the expressions and roles of ERα and ERβ isoforms in thyroid cancer, aiming to provide the perspective of modulating the alternative RNA splicing of ERα and ERβ against thyroid cancer.

Oestrogen Receptor Isoforms May Represent a Therapeutic Target in Oesophageal Adenocarcinoma

Simple Summary

Oesophageal adenocarcinoma is a lethal malignancy with limited treatment options. Recent studies have identified oestrogen receptors (ERs) in this cancer, which could represent a new target for therapy. In this study, we used laboratory models of oesophageal adenocarcinoma to look for the presence of variant forms of ERs. We also assessed the response to treatment with a drug that acts through these ERs. We found that variant forms of ERs do exist in this malignancy and that some of the variants appear to be important in order for the cells to respond to treatment. This could be due to interactions between different ERs, or between ERs and other molecules that are known to be important in cancer growth. Our findings are encouraging in that drugs that act through ERs might be useful for patients with oesophageal adenocarcinoma in the future.

Abstract

Oesophageal adenocarcinoma is a rapidly increasing problem in which treatment options are limited. Previous studies have shown that oesophageal adenocarcinoma cells and tissues express oestrogen receptors (ERs) and show growth suppression and apoptosis in response to ER modulator agents such as tamoxifen. ERs are known to be expressed in a number of isoforms that act together to regulate cell growth and cell death. In this study, we used western blotting to profile the expression of ERα and ERβ isoforms, and expression of the oncologically related molecules p53, HER2, and EGFR, in a panel of oesophageal adenocarcinoma cell lines. The cytotoxicity of tamoxifen in the cell lines was determined with Annexin V-FITC flow cytometry, and correlations between cytotoxicity and receptor expression were assessed using Spearman’s rank-order correlation. Oesophageal adenocarcinoma cell lines showed varying cytotoxicity in response to tamoxifen. The ER species ERα90, ERα50, and ERα46, as well as p53, were positively associated with a cytotoxic response. Conversely, ERα74, ERα70, and ERβ54 were associated with a lack of cytotoxic response. The ER species detected in oesophageal adenocarcinoma cells may work together to confer sensitivity to ER modulators in this disease, which could open up a new avenue for therapy in selected patients.

Estrogen Biosynthesis and Signal Transduction in Ovarian Disease

Estrogen mainly binds to estrogen receptors (ERs) to regulate menstrual cycles and reproduction. The expression of ERalpha (ERα), ERbeta (ERβ), and G-protein-coupled estrogen receptor (GPER) mRNA could be detected in ovary, suggesting that they play an important role in estrogen signal transduction in ovary. And many studies have revealed that abnormal expression of estrogen and its receptors is closely related to ovarian disease or malignant tumors. With the continuous development and research of animal models, tissue-specific roles of both ERα and ERβ have been demonstrated in animals, which enable people to have a deeper understanding of the potential role of ER in regulating female reproductive diseases. Nevertheless, our current understanding of ERs expression and function in ovarian disease is, however, incomplete. To elucidate the biological mechanism behind ERs in the ovary, this review will focus on the role of ERα and ERβ in polycystic ovary syndrome (PCOS), ovarian cancer and premature ovarian failure (POF) and discuss the major challenges of existing therapies to provide a reference for the treatment of estrogen target tissue ovarian diseases.

Estradiol Signaling at the Heart of Folliculogenesis: Its Potential Deregulation in Human Ovarian Pathologies

Estradiol (E2) is a major hormone controlling women fertility, in particular folliculogenesis. This steroid, which is locally produced by granulosa cells (GC) within ovarian follicles, controls the development and selection of dominant preovulatory follicles. E2 effects rely on a complex set of nuclear and extra-nuclear signal transduction pathways principally triggered by its nuclear receptors, ERα and ERβ. These transcription factors are differentially expressed within follicles, with ERβ being the predominant ER in GC. Several ERβ splice isoforms have been identified and display specific structural features, which greatly complicates the nature of ERβ-mediated E2 signaling. This review aims at providing a concise overview of the main actions of E2 during follicular growth, maturation, and selection in human. It also describes the current understanding of the various roles of ERβ splice isoforms, especially their influence on cell fate. We finally discuss how E2 signaling deregulation could participate in two ovarian pathogeneses characterized by either a follicular arrest, as in polycystic ovary syndrome, or an excess of GC survival and proliferation, leading to granulosa cell tumors. This review emphasizes the need for further research to better understand the molecular basis of E2 signaling throughout folliculogenesis and to improve the efficiency of ovarian-related disease therapies.

Transcriptional regulation of CYP19A1 expression in chickens: ESR1, ESR2 and NR5A2 form a functional network

Aromatase, encoded by CYP19A1, is responsible for the conversion of androgen to estrogen, which plays a vital role in the development and function of the ovary and functions in many other physiological processes in both sexes. Instead of being expressed in ovarian granulosa cells, as in mammals, CYP19A1 is expressed in chickens in the theca cells of ovarian follicles, and the mechanism of CYP19A1 expression regulation remains unknown. Here, using immunofluorescence and western blotting assay, we first confirmed that CYP19A1 and FOXL2 (Forkheadbox L2) were coexpressed in pre-granulosa cells of female chicken embryonic gonads, while FOXL2 did not affect aromatase expression at embryonic stages. Second, our research showed that CYP19A1, ESR1 (estrogen receptor alpha), ESR2 (estrogen receptor beta) and NR5A2 (liver receptor homologue-1) were coexpressed in the theca cell layers of chicken small yellow follicles. There was cross-talk between CYP19A1 and candidate transcription factors (ESR1, ESR2 and NR5A2), which was identified by generating a reliable theca cell culture model. Using luciferase assays in theca cells and chicken embryonic fibroblast (DF-1) cells, the results suggested that ESR1 and NR5A2 had potential effects on CYP19A1 promoter activity in chickens. Overexpression of ESR1, ESR2 and NR5A2 in chicken embryonic fibroblast (DF-1) cells upregulated the protein expression of CYP19A1, mutually restricted each other and formed a potential regulatory network to coordinate the expression of CYP19A1. To conclude, our results indicated that FOXL2 cannot regulate the expression of CYP19A1 at chicken embryonic stages and after sexual maturity, ESR1, ESR2 and NR5A2 form a functional network to affect the expression of CYP19A1. These results laid a foundation for further research on the transcriptional regulation of chicken aromatase.

Role of estrogen receptors in health and disease

Estrogen receptors (ERs) regulate multiple complex physiological processes in humans. Abnormal ER signaling may result in various disorders, including reproductive system-related disorders (endometriosis, and breast, ovarian, and prostate cancer), bone-related abnormalities, lung cancer, cardiovascular disease, gastrointestinal disease, urogenital tract disease, neurodegenerative disorders, and cutaneous melanoma. ER alpha (ERα), ER beta (ERβ), and novel G-protein-coupled estrogen receptor 1 (GPER1) have been identified as the most prominent ERs. This review provides an overview of ERα, ERβ, and GPER1, as well as their functions in health and disease. Furthermore, the potential clinical applications and challenges are discussed.

Estrogen Receptor β as a Possible Double-Edged Sword Molecule in Breast Cancer: A Mechanism of Alteration of Its Role by Exposure to Endocrine-Disrupting Chemicals

Estrogen is essential for the growth and development of mammary glands and its signaling is associated with breast cancer growth. Estrogen can exert physiological actions via estrogen receptors α/β (ERα/β). There is experimental evidence suggesting that in ERα/β-positive breast cancer, ERα promotes tumor cell proliferation and ERβ inhibits ERα-mediated transcriptional activity, resulting in abrogation of cell growth. Therefore, ERβ is attracting attention as a potential tumor suppressor, and as a biomarker and therapeutic target in the ERα/β-positive breast cancer. Based on this information, we have hypothesized that some endocrine-disrupting chemicals (EDCs) that can perturb the balance between ERα and ERβ expression levels in breast cancer cells might have effects on the breast cancer proliferation (i.e., down-regulation of the α-type of ER). We have recently reported that 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP), an active metabolite of bisphenol A, in ERα/β-positive human breast cancer significantly down-regulates ERα expression, yet stimulates cell proliferation through the activation of ERβ-mediated transcription. These results support our hypothesis by demonstrating that exposure to MBP altered the functional role of ERβ in breast cancer cells from suppressor to promoter. In contrast, some EDCs, such as Δ⁹-tetrahydrocannabinol and bisphenol AF, can exhibit anti-estrogenic effects through up-regulation of ERβ expression without affecting the ERα expression levels. However, there is no consensus on the correlation between ERβ expression levels and clinical prognosis, which might be due to differences in exposed chemicals. Therefore, elucidating the exposure effects of EDCs can reveal the reason for inconsistent functional role of ERβ in ERα/β-positive breast cancer.

Estrogenic hormones receptors in Alzheimer's disease

Estrogens are hormones that play a critical role during development and growth for the adequate functioning of the reproductive system of women, as well as for maintaining bones, metabolism, and cognition. During menopause, the levels of estrogens are decreased, altering their signaling mediated by their intracellular receptors such as estrogen receptor alpha and beta (ERα and ERβ), and G protein-coupled estrogen receptor (GPER). In the brain, the reduction of molecular pathways mediated by estrogenic receptors seems to favor the progression of Alzheimer's disease (AD) in postmenopausal women. In this review, we investigate the participation of estrogen receptors in AD in women during aging.

ERβ in Triple-Negative Breast Cancer: Emerging Concepts and Therapeutic Possibilities

Despite the improvements in diagnostic and therapeutic approaches, breast cancer still remains one of the world’s leading causes of death among women. Particularly, triple negative breast cancer (TNBC) is characterized by aggressiveness, metastatic spreading, drug resistance and a very high percentage of death in patients. Nowadays, identification of new targets in TNBC appears very compelling. TNBC are considered negative for the estrogen receptor alpha (ERα) expression. Nevertheless, they often express ERβ and its variants. As such, this TNBC subtype still responds to estrogens. While the ERβ1 variant seems to act as a tumor-suppressor, the two variants ERβ2 and 5 exhibit pro-oncogenic activities in TNBC. Thus, ERβ1 activation might be used to limit the growth and spreading as well as to increase the drug sensitivity of TNBC. In contrast, the pro-oncogenic properties of ERβ2 and ERβ5 suggest the possible development and clinical use of specific antagonists in TNBC treatment. Furthermore, the role of ERβ might be regarded in the context of the androgen receptor (AR) expression, which represents another key marker in TNBC. The relationship between AR and ERβ as well as the ability to modulate the receptor-mediated effects through agonists/antagonists represent a challenge to develop more appropriate therapies in clinical management of TNBC patients. In this review, we will discuss the most recent data in the field. Therapeutic implications of these findings are also presented in the light of the discovery of specific ERβ modulators.

Oestrogen receptors: A potential therapeutic target in oesophageal adenocarcinoma?

Oesophageal cancer is the seventh most common cancer in the world and adenocarcinoma is the dominant subtype in Western industrialised nations. The global 5-year relative survival rate for oesophageal adenocarcinoma is 12%. Chemotherapy is a standard treatment offered to patients with both resectable and unresectable disease. However, there are only a few established chemotherapeutic drug options and progress in this area is limited. Recent efforts have focused on targeted molecular therapies. Epidemiological evidence points towards hormonal influences on disease development, particularly sex hormones. Several research studies have demonstrated oestrogen receptor (ER) expression in oesophageal adenocarcinoma tissue, making them a possible option for targeting with ER modulating agents. ERs are also present in laboratory models of the disease and experiments in ER-positive cell lines suggest that ER modulator therapy may be effective. A deeper understanding of the roles of ERα and ERβ in this disease would be valuable for future translation into clinical practice. In this review, we discuss the association between oestrogens and the development of oesophageal adenocarcinoma and the potential to modulate ER signalling networks for therapeutic benefit.

Carcinogenesis of Triple-Negative Breast Cancer and Sex Steroid Hormones

Simple Summary

Triple-negative breast cancer (TNBC) lacks all of three treatment targets (estrogen receptor-α, ER-α; progesterone receptor, PgR; and human epidermal growth factor receptor 2, HER2) and is usually associated with a poor clinical outcome; however, several sex steroid receptors, such as androgen receptor (AR), ER-β, and G-protein-coupled estrogen receptor, are frequently expressed and their biological and clinical importance has been suggested. Despite the structural similarity between sex steroid hormones (androgens and estrogens) or receptors (AR and ER-β), similar signaling mechanisms of these hormones, and the coexistence of these hormones and their receptors in TNBC in a clinical setting, most studies or reviews focused on only one of these receptors, and rarely reviewed them in a comprehensive way. In this review, the carcinogenic or pathobiological role of sex steroid hormones in TNBC is considered, focusing on common and differing features of hormone actions.

Abstract

Triple-negative breast cancer (TNBC) lacks an effective treatment target and is usually associated with a poor clinical outcome; however, hormone unresponsiveness, which is the most important biological characteristic of TNBC, only means the lack of nuclear estrogenic signaling through the classical estrogen receptor (ER), ER-α. Several sex steroid receptors other than ER-α: androgen receptor (AR), second ER, ER-β, and non-nuclear receptors represented by G-protein-coupled estrogen receptor (GPER), are frequently expressed in TNBC and their biological and clinical importance has been suggested by a large number of studies. Despite the structural similarity between each sex steroid hormone (androgens and estrogens) or each receptor (AR and ER-β), and similarity in the signaling mechanisms of these hormones, most studies or reviews focused on one of these receptors, and rarely reviewed them in a comprehensive way. Considering the coexistence of these hormones and their receptors in TNBC in a clinical setting, a comprehensive viewpoint would be important to correctly understand the association between the carcinogenic mechanism or pathobiology of TNBC and sex steroid hormones. In this review, the carcinogenic or pathobiological role of sex steroid hormones in TNBC is considered, focusing on the common and divergent features of the action of these hormones.

Estradiol Regulates mRNA Levels of Estrogen Receptor Beta 4 and Beta 5 Isoforms and Modulates Human Granulosa Cell Apoptosis

Estrogen receptor beta (ERβ) plays a critical role in granulosa cell (GC) functions. The existence of four human ERβ splice isoforms in the ovary suggests their differential implication in 17β-estradiol (E2) actions on GC apoptosis causing follicular atresia. In this study, we investigated whether E2 can regulate ERβ isoforms expression to fine tune its apoptotic activities in human GC. For this purpose, we measured by RT-qPCR the expression of ERβ isoforms in primary culture of human granulosa cells (hGCs) collected from patients undergoing in vitro fertilization, before and after E2 exposure. Besides, we assessed the potential role of ERβ isoforms on cell growth and apoptosis after their overexpression in a human GC line (HGrC1 cells). We confirmed that ERβ1, ERβ2, ERβ4, and ERβ5 isoform mRNAs were predominant over that of ERα in hGCs, and found that E2 selectively regulates mRNA levels of ERβ4 and ERβ5 isoforms in these cells. In addition, we demonstrated that overexpression of ERβ1 and ERβ4 in HGrC1 cells increased cell apoptosis by 225% while ERβ5 or ERβ2 had no effect. Altogether, our study revealed that E2 may influence GC fate by specifically regulating the relative abundance of ERβ isoforms mRNA to modulate the balance between pro-apoptotic and non-apoptotic ERβ isoforms.

Interplay Between Endocrine Disruptors and Immunity: Implications for Diseases of Autoreactive Etiology

The sex-bias of disease susceptibility has remained a puzzling aspect of several autoimmune conditions, including post-infection viral autoimmunity. In the last half of the twentieth century, the incidence rate of female-biased autoimmunity has steadily increased independent of medical advances. This has suggested a role for environmental factors, such as endocrine disrupting chemicals, which have been described to interfere with endocrine signaling. Endocrine involvement in the proper function of innate and adaptive immunity has also been defined, however, these two areas have rarely been reviewed in correlation. In addition, studies addressing the effects of endocrine disruptors have reported findings resulting from a broad range of exposure doses, schedules and models. This experimental heterogeneity adds confusion and may mislead the translation of findings to human health. Our work will normalize results across experiments and provide a necessary summary relevant to human exposure. Through a novel approach, we describe how different categories of ubiquitously used environmental endocrine disruptors interfere with immune relevant endocrine signaling and contribute to autoimmunity. We hope this review will guide identification of mechanisms and concentration-dependent EDC effects important not only for the sex-bias of autoimmunity, but also for other conditions of immune dysfunction, including post-infection autoreactivity such as may arise following severe acute respiratory syndrome coronavirus 2, Epstein-Barr virus, Herpes Simplex virus.

Expression and clinical implications of estrogen receptors in thoracic malignancies: a narrative review

Thoracic malignancies represent a significant global health burden with incidence and mortality increasing year by year. Thoracic cancer prognosis and treatment options depend on several factors, including the type and size of the tumor, its location, and the overall health status of patients. Gender represents an important prognostic variable in thoracic malignancies. One of the greatest biological differences between women and men is the presence of female sex hormones, and an increasing number of studies suggest that estrogens may play either a causative or a protective role in thoracic malignancies. Over the past 60 years since the discovery of the first nuclear estrogen receptor (ER) isoform α and the almost 20 years since the discovery of the second estrogen receptor, ERβ, different mechanisms governing estrogen action have been identified and characterized. This literature review reports the published data regarding the expression and function of ERs in different thoracic malignancies and discuss sex disparity in clinical outcomes. From this analysis emerges that further efforts are warranted to better elucidate the role of sex hormones in thoracic malignancies, and to reduce disparities in care between genders. Understanding the mechanisms by which gender-related differences can affect and interfere with the onset and evolution of thoracic malignancies and impact on response to therapies could help to improve the knowledge needed to develop increasingly personalized and targeted treatments.

Optimization of immunohistochemical detection of rat ESR2 proteins with well-validated monoclonal antibody PPZ0506

Although there are few well-validated antibodies against ESR2 proteins, a recent validation assessment identified a specific monoclonal antibody against human ESR2 proteins (PPZ0506). Furthermore, our previous study confirmed its cross-reactivity and specificity against rodent ESR2 proteins, enabling the determination of true ESR2 distribution profiles in rodents. Therefore, we aimed to determine optimal conditions for ESR2 detection by PPZ0506 immunostaining and analyze ESR2 distribution in rats. We evaluated several staining conditions using paraffin-embedded and frozen ovary sections. Immunohistochemical staining with PPZ0506 antibody required strong antigen retrieval and appropriate antibody dilution. Subsequent immunohistochemical analysis in multiple tissues under optimized conditions revealed that rat ESR2 proteins are expressed in a more localized manner than previously assumed. Our results suggest that previous immunohistochemical studies using inadequately validated antibodies against ESR2 proteins overestimated their distribution profiles. We expect that optimized immunohistochemical detection with PPZ0506 antibody can help researchers solve several conflicting problems in ESR2 research.

Estrogen Receptors in Polycystic Ovary Syndrome

Female infertility is mainly caused by ovulation disorders, which affect female reproduction and pregnancy worldwide, with polycystic ovary syndrome (PCOS) being the most prevalent of these. PCOS is a frequent endocrine disease that is associated with abnormal function of the female sex hormone estrogen and estrogen receptors (ERs). Estrogens mediate genomic effects through ERα and ERβ in target tissues. The G-protein-coupled estrogen receptor (GPER) has recently been described as mediating the non-genomic signaling of estrogen. Changes in estrogen receptor signaling pathways affect cellular activities, such as ovulation; cell cycle phase; and cell proliferation, migration, and invasion. Over the years, some selective estrogen receptor modulators (SERMs) have made substantial strides in clinical applications for subfertility with PCOS, such as tamoxifen and clomiphene, however the role of ER in PCOS still needs to be understood. This article focuses on the recent progress in PCOS caused by the abnormal expression of estrogen and ERs in the ovaries and uterus, and the clinical application of related targeted small-molecule drugs.

Estrogen Receptor Beta: The Promising Biomarker and Potential Target in Metastases

The discovery of the Estrogen Receptor Beta (ERβ) in 1996 opened new perspectives in the diagnostics and therapy of different types of cancer. Here, we present a review of the present research knowledge about its role in endocrine-related cancers: breast, prostate, and thyroid, and colorectal cancers. We also discuss the reasons for the controversy of its role in carcinogenesis and why it is still not in use as a biomarker in clinical practice. Given that the diagnostics and therapy would benefit from the introduction of new biomarkers, we suggest ways to overcome the contradictions in elucidating the role of ERβ.

Estrogen Receptor β1 Expression Patterns Have Different Effects on Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors' Treatment Response in Epidermal Growth Factor Receptor Mutant Lung Adenocarcinoma

Estrogen receptor β (ERβ) can regulate cellular signaling through non-genomic mechanisms, potentially promoting resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). However, the mechanisms underlying the ERβ-mediated resistance to EGFR TKIs remain poorly understood. In this study, we investigated the role of the interaction between ERβ1 and ERβ5 in non-genomic signaling in lung adenocarcinoma. We established PC9 cell lines stably overexpressing ERβ1 or ERβ1/ERβ5. Immunofluorescence revealed that ERβ5 overexpression partly retained ERβ1 in the cytoplasm. Immunoblotting analyses revealed that EGFR pathway activation levels were higher in PC9/ERβ1/5 cells than those in PC9/ERβ1 or control PC9 cells. In the presence of estradiol, PI3K/AKT/mTOR pathway activation levels were higher in ERβ1/5-expressing cells than those in ERβ1-expressing cells. Additionally, PC9/ERβ1/5 cells were less prone to the cytotoxic and pro-apoptotic effects of gefitinib compared with PC9/ERβ1 or control PC9 cells. Cytoplasmic ERβ1 was associated with poor progression-free survival in lung cancer patients treated with EGFR TKIs. These results suggest that cytoplasmic ERβ1 was responsible for EGFR TKI resistance slightly through non-genomic mechanism in EGFR mutant lung adenocarcinoma.

Estrogen Receptor Beta (ERβ): A Ligand Activated Tumor Suppressor

Estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ) belong to a superfamily of nuclear receptors called steroid hormone receptors, which, upon binding ligand, dimerize and translocate to the nucleus where they activate or repress the transcription of a large number of genes, thus modulating critical physiologic processes. ERβ has multiple isoforms that show differing association with prognosis. Expression levels of the full length ERβ1 isoform are often lower in aggressive cancers as compared to normal tissue. High ERβ1 expression is associated with improved overall survival in women with breast cancer. The promise of ERβ activation, as a potential targeted therapy, is based on concurrent activation of multiple tumor suppressor pathways with few side effects compared to chemotherapy. Thus, ERβ is a nuclear receptor with broad-spectrum tumor suppressor activity, which could serve as a potential treatment target in a variety of human cancers including breast cancer. Further development of highly selective agonists that lack ERα agonist activity, will be necessary to fully harness the potential of ERβ.

Indole Derivative Interacts with Estrogen Receptor Beta and Inhibits Human Ovarian Cancer Cell Growth

Ovarian cancer remains the leading cause of mortality among gynecological tumors. Estrogen receptor beta (ERβ) expression has been suggested to act as a tumor suppressor in epithelial ovarian cancer by reducing both tumor growth and metastasis. ERβ expression abnormalities represent a critical step in the development and progression of ovarian cancer: for these reasons, its re-expression by genetic engineering, as well as the use of targeted ERβ therapies, still constitute an important therapeutic approach. 3-{[2-chloro-1-(4-chlorobenzyl)-5-methoxy-6-methyl-1H-indol-3-yl]methylene}-5-hydroxy-6-methyl-1,3-dihydro-2H-indol-2-one, referred to here as compound 3, has been shown to have cytostatic as well cytotoxic effects on various hormone-dependent cancer cell lines. However, the mechanism of its anti-carcinogenic activity is not well understood. Here, we offer a possible explanation of such an effect in the human ovarian cancer cell line IGROV1. Chromatin binding protein assay and liquid chromatography mass spectrometry were exploited to localize and quantify compound 3 in cells. Molecular docking was used to prove compound 3 binding to ERβ. Mass spectrometry-based approaches were used to analyze histone post-translational modifications. Finally, gene expression analyses revealed a set of genes regulated by the ERβ/3 complex, namely CCND1, MYC, CDKN2A, and ESR2, providing possible molecular mechanisms that underline the observed antiproliferative effects.

Estrogen Signaling and Its Potential as a Target for Therapy in Ovarian Cancer

The estrogen receptor (ER) has functionality in selected ovarian cancer subtypes and represents a potential target for therapy. The majority (>80%) of high grade serous, low grade serous and endometrioid carcinomas and many granulosa cell tumors express ER-alpha (ERα), and these tumor types have demonstrated responses to endocrine therapy (tamoxifen and aromatase inhibitors) in multiple clinical studies. Biomarkers of responses to these drugs are actively being sought to help identify responsive cancers. Evidence for both pro-proliferative and pro-migratory roles for ERα has been obtained in model systems. ER-beta (ERβ) is generally considered to have a tumor suppressor role in ovarian cancer cells, being associated with the repression of cell growth and invasion. The differential expression of the specific ERβ isoforms may determine functionality within ovarian cancer cells. The more recently identified G protein-coupled receptor (GPER1; GPR30) has been shown to mediate both tumor-suppressive and tumor-promoting action in ovarian cancer cells, suggesting a more complex role. This review will summarize recent findings in this field.

Insights into the Role of Estrogen Receptor β in Triple-Negative Breast Cancer

Estrogen receptors (ERα and ERβ) are ligand-activated transcription factors that play different roles in gene regulation and show both overlapping and specific tissue distribution patterns. ERβ, contrary to the oncogenic ERα, has been shown to act as an oncosuppressor in several instances. However, while the tumor-promoting actions of ERα are well-known, the exact role of ERβ in carcinogenesis and tumor progression is not yet fully understood. Indeed, to date, highly variable and even opposite effects have been ascribed to ERβ in cancer, including for example both proliferative and growth-inhibitory actions. Recently ERβ has been proposed as a potential target for cancer therapy, since it is expressed in a variety of breast cancers (BCs), including triple-negative ones (TNBCs). Because of the dependence of TNBCs on active cellular signaling, numerous studies have attempted to unravel the mechanism(s) behind ERβ-regulated gene expression programs but the scenario has not been fully revealed. We comprehensively reviewed the current state of knowledge concerning ERβ role in TNBC biology, focusing on the different signaling pathways and cellular processes regulated by this transcription factor, as they could be useful in identifying new diagnostic and therapeutic approaches for TNBC.

Small Non-Coding RNA Profiling Identifies miR-181a-5p as a Mediator of Estrogen Receptor Beta-Induced Inhibition of Cholesterol Biosynthesis in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a highly heterogeneous disease, representing the most aggressive breast cancer (BC) subtype with limited treatment options due to a lack of estrogen receptor alpha (ERα), progesterone receptor (PR), and Erb-B2 receptor tyrosine kinase 2 (HER2/neu) expression. Estrogen receptor beta (ERβ) is present in a fraction of TNBC patients, where its expression correlates with improved patient outcomes, supported by the fact that it exerts oncosuppressive effects in TNBC cell models in vitro. ERβ is involved in microRNA-mediated regulation of gene expression in hormone-responsive BC cells and could mediate its actions through small noncoding RNAs (sncRNAs) in TNBCs also. To verify this possibility, smallRNA sequencing was performed on three ERβ-expressing cell lines from different TNBC molecular subtypes. Several sncRNAs resulted modulated by ERβ, with a subset being regulated in a tumor subtype-independent manner. Interestingly, sncRNA profiling of 12 ERβ+and 32 ERβ− primary TNBC biopsies identified 7 microRNAs, 1 PIWI-interacting RNA (piRNA), and 1 transfer RNA (tRNA) differentially expressed in ERβ+ compared to ERβ− tumors and cell lines. Among them, miR-181a-5p was found to be overexpressed in ERβ+ tumors and predicted target key components of the cholesterol biosynthesis pathway previously found to be inhibited by ERβ in TNBC cells.

Sex differences on adipose tissue remodeling: from molecular mechanisms to therapeutic interventions

Sexual dimorphism greatly influences adipose tissue remodeling, which is characterized by changes in the activity, number, and/or size of adipocytes in response to distinct stimuli, including lifestyle and anti-obesity drugs. This sex dependence seems to be due to the anatomical and endocrine disparities between men and women. At the molecular level, sex hormones are believed to mediate such differences and involve estrogen and androgen receptor-induced gene expression. The signaling pathways that regulate adipose tissue metabolism and function include peroxisome proliferator-activated receptor gamma, uncoupling protein 1 (UCP1), 5' adenosine monophosphate-activated protein kinase (AMPK), and mitochondrial oxidative phosphorylation (OXPHOS), among other molecular players. Sex hormone-related pathways also interplay with adrenergic signaling, probably the most well-characterized molecular mechanism implicated in the remodeling of white adipose tissue. This review overviews and integrates the signaling pathways behind sexual dimorphism in adipose tissue remodeling, hoping to increase the knowledge on the pathogenesis of diseases, such as obesity and related comorbidities, and consequently, to drive future studies to investigate the regulation of this tissue homeostasis, either in men or women.

Role of 17β-Estradiol on Cell Proliferation and Mitochondrial Fitness in Glioblastoma Cells

Gliomas are the most common primary tumors of the central nervous system (CNS) in the adult. Previous data showed that estrogen affects cancer cells, but its effect is cell-type-dependent and controversial. The present study aimed to analyze the effects of estradiol (E2, 5 nM) in human glioblastoma multiforme U87-MG cells and how it may impact on cell proliferation and mitochondrial fitness. We monitored cell proliferation by xCELLigence technology and mitochondrial fitness by assessing the expression of genes involved in mitochondrial biogenesis (PGC1α, SIRT1, and TFAM), oxidative phosphorylation (ND4, Cytb, COX-II, COX IV, NDUFA6, and ATP synthase), and dynamics (OPA1, MNF2, MNF1, and FIS1). Finally, we evaluated Nrf2 nuclear translocation by immunocytochemical analysis. Our results showed that E2 resulted in a significant increase in cell proliferation, with a significant increase in the expression of genes involved in various mechanisms of mitochondrial fitness. Finally, E2 treatment resulted in a significant increase of Nrf2 nuclear translocation with a significant increase in the expression of one of its target genes (i.e., heme oxygenase-1). Our results suggest that E2 promotes proliferation in glioblastoma cells and regulate the expression of genes involved in mitochondrial fitness and chemoresistance pathway.

Applicability of Anti-Human Estrogen Receptor β Antibody PPZ0506 for the Immunodetection of Rodent Estrogen Receptor β Proteins

Several lines of controversial evidence concerning estrogen receptor β (ERβ) remain to be solved because of the unavailability of specific antibodies against ERβ. The recent validation analysis identified a monoclonal antibody (PPZ0506) with sufficient specificity against human ERβ. However, the specificity and cross-reactivity of PPZ0506 antibody against ERβ proteins from laboratory animals have not been confirmed. In the present study, we aimed to validate the applicability of PPZ0506 to rodent studies. The antibody exhibited specific cross-reactivity against mouse and rat ERβ proteins in immunoblot and immunocytochemical experiments using transfected cells. In immunohistochemistry for rat tissue sections, PPZ0506 showed immunoreactive signals in the ovary, prostate, and brain. These immunohistochemical profiles of rat ERβ proteins in rat tissues accord well with its mRNA expression patterns. Although the antibody was reported to show the moderate signals in human testis, no immunoreactive signals were observed in rat testis. Subsequent RT-PCR analysis revealed that this species difference in ERβ expression resulted from different expression profiles related to the alternative promoter usage between humans and rats. In conclusion, we confirmed applicability of PPZ0506 for rodent ERβ studies, and our results provide a fundamental basis for further examination of ERβ functions.

Sex steroid metabolism and actions in non-small cell lung carcinoma

Despite recent development in targeted therapies, lung cancer still remains the leading cause of cancer death. Therefore, a better understanding of its pathogenesis and progression could contribute to improving the eventual clinical outcome of the patients. Results of recently published several in vitro and clinical studies indicated the possible involvement of sex steroids in both development and progression of non-small cell lung carcinoma (NSCLC). Therefore we summarized the reported clinical relevant information of the sex steroids, their receptors and steroid metabolizing enzymes related to NSCLC in this mini-review. In addition, we also reviewed the potential "endocrine therapy", targeting sex steroid actions and/or metabolism in NSCLC patients.

Optimized immunohistochemical detection of estrogen receptor beta using two validated monoclonal antibodies confirms its expression in normal and malignant breast tissues

PURPOSE

Significant controversy exists regarding the expression patterns of estrogen receptor beta (ERβ) in normal and diseased breast tissue. To address this issue, we have validated two ERβ antibodies, optimized the IHC protocols for both antibodies and now report the expression patterns of ERβ in normal and malignant breast tissues.

METHODS

ERβ antibody specificity was determined using western blot and IHC analysis. ERβ protein expression patterns were assessed via IHC in normal breast tissue and invasive breast carcinoma. Further, we report the detailed protocol of the ERβ IHC assay developed in our CAP/CLIA certified laboratory to provide a standardized method for future studies.

RESULTS

We have confirmed the specificity of two independent ERβ monoclonal antibodies, one that detects total (i.e., full length plus splice variants 2-5, which do not include the ligand binding domain) ERβ protein (PPZ0506) and one that detects only the full-length form, which includes the ligand binding domain, of ERβ (PPG5/10). Using these two antibodies, we demonstrate that ERβ is highly expressed in normal human breast tissue as well as in 20-30% of invasive breast cancers. Further, these two antibodies exhibited similar staining patterns across multiple different tissues and were highly concordant with regard to determining ERβ positivity in breast cancers.

CONCLUSIONS

ERβ protein was shown to be abundant in the majority of normal breast epithelial cells and is present in 20-30% of breast cancers. Use of these two antibodies, along with their standardized IHC protocols, provide a reference for future studies aimed at determining the utility of ERβ as a prognostic and/or predictive biomarker in various tissues of benign or malignant states.

Estrogen Receptors in Epithelial-Mesenchymal Transition of Prostate Cancer

Prostate cancer (PC) remains a widespread malignancy in men. Since the androgen/androgen receptor (AR) axis is associated with the pathogenesis of prostate cancer, suppression of AR-dependent signaling by androgen deprivation therapy (ADT) still represents the primary intervention for this disease. Despite the initial response, prostate cancer frequently develops resistance to ADT and progresses. As such, the disease becomes metastatic and few therapeutic options are available at this stage. Although the majority of studies are focused on the role of AR signaling, compelling evidence has shown that estrogens and their receptors control prostate cancer initiation and progression through a still debated mechanism. Epithelial versus mesenchymal transition (EMT) is involved in metastatic spread as well as drug-resistance of human cancers, and many studies on the role of this process in prostate cancer progression have been reported. We discuss here the findings on the role of estrogen/estrogen receptor (ER) axis in epithelial versus mesenchymal transition of prostate cancer cells. The pending questions concerning this issue are presented, together with the impact of the available data in clinical management of prostate cancer patients.

Establishment of three estrogen receptors (esr1, esr2a, esr2b) knockout lines for functional study in Nile tilapia

Estrogens play fundamental roles in regulating reproductive activities and they act through estrogen receptors (ESRs) in all vertebrates. To date, distinct roles of estrogen receptors have been characterized only in human and model organisms, including mouse, rat, zebrafish and medaka. Physiological role of estrogen/receptor signaling in reproduction remains poorly defined in non-model organisms. In the present study, we successfully generated esr1, esr2a and esr2b mutant lines in tilapia by CRISPR/Cas9 and examined their phenotypes. Surprisingly, the esr1 mutants showed no phenotypes of reproductive development and function in both females and males. The esr2a mutant females showed significantly delayed ovarian development and follicle growth at 90 and 180 dah, and the development caught up later at 360 dah. The esr2a mutant males showed no phenotypes at 90 dah, and displayed smaller gonads and efferent ducts, less spermatogonia and more abnormal sperms at 180 dah. In contrast, the esr2b mutants displayed abnormal development of ovarian ducts and efferent ducts which failed to connect to the genital orifice, and which in turn, resulted in infertility in female and male, respectively, although they produced gametes in their gonads. Taken together, our study provides evidence for differential functions of esr1, esr2a and esr2b in fish reproduction.

17β-Estradiol protects the esophageal epithelium from IL-13-induced barrier dysfunction and remodeling

BACKGROUND

The incidence of eosinophilic esophagitis (EoE) is greater in male than female subjects, and the underlying molecular basis for this sex bias remains unclear.

OBJECTIVE

We sought to delineate the contribution of the sex hormone estrogen to the EoE phenotype and esophageal epithelial barrier function and remodeling.

METHODS

We performed demographic and incidence analyses of EoE in male and female subjects from a single-center pediatric cohort. Estrogen-responsive gene expression analyses and estrogen receptor (ESR) immunofluorescence staining of esophageal biopsy specimens from patients with EoE and control subjects were performed. The effect of 17β-estradiol (E2) on IL-13-induced signaling pathways, gene expression, and esophageal epithelial architecture and barrier function in a primary human esophageal keratinocyte cell (EPC2) culture system (EPC2-air-liquid interface) was examined.

RESULTS

We observed a male predominance in patients with EoE. Analyses of RNA sequencing data sets revealed a significant dysregulation of the estrogen-responsive gene network and expression of ESR1 and ESR2 in esophageal biopsy specimens from patients with EoE compared with control subjects. IL-13 stimulation of EPC2-air-liquid interface cells led to altered cellular architecture with induced dilation of intercellular spaces and barrier dysfunction. Pretreatment of EPC2s with E2 prior to IL-13 exposure abrogated IL-13-induced architectural changes and esophageal barrier dysfunction. Mechanistically, E2-protective effects were dependent on ESR2 and associated with diminishing of IL-13-induced tyrosine kinase 2 and signal transducer and activator of transcription 6 phosphorylation and EoE-dysregulated gene expression.

CONCLUSIONS

Estrogen-responsive genes are modified in patients with EoE compared with control subjects. E2 attenuated IL-13-induced architectural changes and esophageal epithelial barrier dysfunction through inhibition of the IL-13/tyrosine kinase 2/signal transducer and activator of transcription 6 pathway via ESR2-dependent process. Estrogen hormone signaling may protect against development of EoE in female subjects.

Expression of estrogen receptor beta isoforms in pancreatic adenocarcinoma

Limited studies have shown that some patients with pancreatic adenocarcinoma (PAC) may benefit from treatment with tamoxifen. PAC has been shown to be largely negative for estrogen receptor alpha (ER-alpha). The aim of this pilot study was to investigate ER-beta expression in human PAC. Sections of tissue microarray with 18 evaluable cases of human PAC were stained by immunohistochemistry (IHC) for ER-beta1, ER-beta2, ER-beta5, and Cyclin A. The levels of ER-beta isoform expression and the S-phase fraction (SPF) were determined using quantitative digital image analysis. Higher mean and median ER-beta2 levels correlated with male sex (p = 0.057 and p = 0.035, respectively), older age (p = 0.005 and p = 0.006, respectively), and lower pT stage (p = 0.008 and p = 0.009). Mean and median ER-beta5 levels correlated negatively with SPF (p = 0.021 and p = 0.047, respectively). Mean ER-beta1 expression did not correlate with any of the above mentioned clinicopathologic factors. The findings in this pilot study, although should be considered preliminary, suggest that some ER-beta isoforms may play a role in the biology of PAC. Additional larger studies are needed to confirm our findings, and to determine whether ER-beta may be considered for future targeted therapy.

Mechanisms for estrogen receptor expression in human cancer

Estrogen is a steroid hormone that has critical roles in reproductive development, bone homeostasis, cardiovascular remodeling and brain functions. However, estrogen also promotes mammary, ovarian and endometrial tumorigenesis. Estrogen antagonists and drugs that reduce estrogen biosynthesis have become highly successful therapeutic agents for breast cancer patients. The effects of estrogen are largely mediated by estrogen receptor (ER) α and ERβ, which are members of the nuclear receptor superfamily of transcription factors. The mechanisms underlying the aberrant expression of ER in breast cancer and other types of human tumors are complex, involving considerable alternative splicing of ERα and ERβ, transcription factors, epigenetic and post-transcriptional regulation of ER expression. Elucidation of mechanisms for ER expression may not only help understand cancer progression and evolution, but also shed light on overcoming endocrine therapy resistance. Herein, we review the complex mechanisms for regulating ER expression in human cancer.

Sexual dimorphism of cardiometabolic dysfunction: Gut microbiome in the play?

BACKGROUND

Sex is one of the most powerful modifiers of disease development. Clear sexual dimorphism exists in cardiometabolic health susceptibility, likely due to differences in sex steroid hormones. Changes in the gut microbiome have been linked with the development of obesity, type 2 diabetes, and atherosclerosis; however, the impact of microbes in sex-biased cardiometabolic disorders remains unclear. The gut microbiome is critical for maintaining a normal estrous cycle, testosterone levels, and reproductive function. Gut microbes modulate the enterohepatic recirculation of estrogens and androgens, affecting local and systemic levels of sex steroid hormones. Gut bacteria can also generate androgens from glucocorticoids.

SCOPE OF REVIEW

This review summarizes current knowledge of the complex interplay between sexual dimorphism in cardiometabolic disease and the gut microbiome.

MAJOR CONCLUSIONS

Emerging evidence suggests the role of gut microbiome as a modifier of disease susceptibility due to sex; however, the impact on cardiometabolic disease in this complex interplay is lacking. Elucidating the role of gut microbiome on sex-biased susceptibility in cardiometabolic disease is of high relevance to public health given its high prevalence and significant financial burden.

Bisphenol AF as an activator of human estrogen receptor β1 (ERβ1) in breast cancer cell lines

Bisphenol AF (BPAF) is now recognized as one of the replacements for bisphenol A (BPA). Although considerable experimental evidence suggests that BPA is an endocrine-disrupting chemical, the toxicological profile of BPAF has been investigated in less detail than that of BPA, even at the in vitro level. BPAF has been established as an activator of estrogen receptor α (ERα) in many cell lines; however, controversy surrounds its effects on the other isoform, ERβ (i.e., whether it functions as a stimulator). Five human ERβ isoforms have been cloned and characterized. Of these, we focused on the interactions between BPAF and the two isoforms, ERβ1 and ERβ2. We demonstrated that i) BPAF functioned as a stimulator of ERβ1 (and ERα), which is transiently expressed in the two types of human breast cancer cells (MDA-MB-231 and SK-BR-3 cells) (EC₅₀ values for ERβ: 6.87 nM and 2.58 nM, respectively, and EC₅₀ values for ERα: 24.7 nM and 181 nM, respectively), ii) the stimulation of ERβ1 by BPAF (1-25 nM) was abrogated by PHTPP (an ERβ selective antagonist), and iii) the expression of ERβ1 and ERβ2 was not modulated by BPAF at nanomolar concentrations up to 25 nM. These results indicate that BPAF activates not only human ERα, but also the ERβ1 isoform in breast cancer cells, and exhibits higher activation potency for ERβ1.

Oestrogen receptor β5 and epidermal growth factor receptor synergistically promote lung cancer progression

Oestrogen receptor beta (ERβ) and epidermal growth factor receptor (EGFR) pathway can synergistically promote the proliferation, invasion, and metastasis of non-small-cell lung cancer (NSCLC) cells. ERβ has five subtypes, and the selective splicing of exon 8 in ERβ5 transcription translational phase makes its biological function different from other subtypes. The following study investigates whether ERβ5 interacts with EGFR pathway in lung cancer. Briefly, we found that the overexpression of ERβ5 and EGFR is associated with poor prognosis and decreased overall survival in NSCLC patients. Furthermore, the effects of ERβ5 and EGFR on cell biological behaviour were investigated in vitro. These results indicated that the combination of ERβ5 and EGF induces cell proliferation and invasion, while the combination of ERβ5 and Gefitinib (EGFR inhibitors, Gef) induces cell apoptosis and promotes cell mitosis in A549 cell line. In addition, the combination of ERβ5 and EGF increases the expression of ERβ5, EGFR, and p-ERK1/2 in lung cancer cells. To sum up, the obtained results suggest that ERβ5 and EGFR synergistically promote the progression of lung cancer by activating MEK/ERK signalling pathway, which provides a theoretical basis for more accurate combined targeted therapy.

17β-estradiol upregulates IL6 expression through the ERβ pathway to promote lung adenocarcinoma progression

Background

In non-small cell lung cancer (NSCLC), estrogen (E2) significantly promotes NSCLC cell growth via estrogen receptor beta (ERβ). Discovery and elucidation of the mechanism underlying estrogen-promoted NSCLC progression is critical for effective preventive interventions. IL6 has been demonstrated to be involved in the development, progression and metastasis in several cancers and IL6 overexpression is associated with poor prognosis in NSCLC. However, the exact role played by IL6 in estrogen-promoted NSCLC progress remain unknown. Here, we evaluated the expression and biological effects of IL6 in NSCLC cells when treated with E2 and explored the underlying mechanism of IL6 in E2-promoted NSCLC progression.

Methods

Expression of ERβ/IL6 in 289 lung cancer samples was assessed by immunohistochemistry. Matched samples of metastatic lymph node and primary tumor tissues were used to quantify the expression of ERβ/IL6 by western blot. Expression levels of IL6 in NSCLC cells were quantified by western blotting, ELISA, and immunofluorescence staining. The effects of IL6 stimulated by E2 on cell malignancy were evaluated using CCK8, colony formation, wound healing and transwell. Furthermore, overexpression and knockdown ERβ constructs were constructed to measure the expression of IL6. The effects of IL6 stimulated by E2 on tumor growth were evaluated using a urethane-induced adenocarcinoma model. In addition, a xenograft mouse model was used to observe differences in ERβ subtype tumor growth with respect to IL6 expression.

Results

IL6/ERβ expression were significantly increased in lung cancer. Higher IL6/ERβ expression was associated with decreased differentiation or increased metastasis. IL6 was an independent prognostic factor for overall survival (OS), higher IL6 expression was associated with decreased OS. Furthermore, ERβ regulates IL6 expression via MAPK/ERK and PI3K/AKT pathways when stimulated by E2 and promotes cell malignancy in vitro and induced tumor growth in vivo. Finally we confirm that ERβ isolation 1/5 is essential for E2 promotion of IL6 expression, while ERβ2 not.

Conclusions

Our findings demonstrate that E2 stimulates IL6 expression to promote lung adenocarcinoma progression through the ERβ pathway. We also clarify the difference in each ERβ subtype for E2 promoting IL6 expression, suggesting that ERβ/IL6 might be potential targets for prognostic assessment and therapeutic intervention in lung cancer.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0804-5) contains supplementary material, which is available to authorized users.