Estrogen receptor ?1 and the ?2/?cx isoforms in nonneoplastic endometrium and in endometrioid carcinoma

Role of Estrogen Receptor β, G-Protein Coupled Estrogen Receptor and Estrogen-Related Receptors in Endometrial and Ovarian Cancer

Ovarian and endometrial cancers are affected by estrogens and their receptors. It has been long known that in different types of cancers, estrogens activate tumor cell proliferation via estrogen receptor α (ERα). In contrast, the role of ERs discovered later, including ERβ and G-protein-coupled ER (GPER1), in cancer is less well understood, but the current state of knowledge indicates them to have a considerable impact on both cancer development and progression. Moreover, estrogen related receptors (ERRs) have been reported to affect pathobiology of many tumor types. This article provides a summary and update of the current findings on the role of ERβ, GPER1, and ERRs in ovarian and endometrial cancer. For this purpose, original research articles on the role of ERβ, GPER1, and ERRs in ovarian and endometrial cancers listed in the PubMed database have been reviewed.

KLF3 and PAX6 are candidate driver genes in late-stage, MSI-hypermutated endometrioid endometrial carcinomas

Endometrioid endometrial carcinomas (EECs) are the most common histological subtype of uterine cancer. Late-stage disease is an adverse prognosticator for EEC. The purpose of this study was to analyze EEC exome mutation data to identify late-stage-specific statistically significantly mutated genes (SMGs), which represent candidate driver genes potentially associated with disease progression. We exome sequenced 15 late-stage (stage III or IV) non-ultramutated EECs and paired non-tumor DNAs; somatic variants were called using Strelka, Shimmer, SomaticSniper and MuTect. Additionally, somatic mutation calls were extracted from The Cancer Genome Atlas (TCGA) data for 66 late-stage and 270 early-stage (stage I or II) non-ultramutated EECs. MutSigCV (v1.4) was used to annotate SMGs in the two late-stage cohorts and to derive p-values for all mutated genes in the early-stage cohort. To test whether late-stage SMGs are statistically significantly mutated in early-stage tumors, q-values for late-stage SMGs were re-calculated from the MutSigCV (v1.4) early-stage p-values, adjusting for the number of late-stage SMGs tested. We identified 14 SMGs in the combined late-stage EEC cohorts. When the 14 late-stage SMGs were examined in the TCGA early-stage data, only Krüppel-like factor 3 (KLF3) and Paired box 6 (PAX6) failed to reach significance as early-stage SMGs, despite the inclusion of enough early-stage cases to ensure adequate statistical power. Within TCGA, nonsynonymous mutations in KLF3 and PAX6 were, respectively, exclusive or nearly exclusive to the microsatellite instability (MSI)-hypermutated molecular subgroup and were dominated by insertions-deletions at homopolymer tracts. In conclusion, our findings are hypothesis-generating and suggest that KLF3 and PAX6, which encode transcription factors, are MSI target genes and late-stage-specific SMGs in EEC.

Estrogen Receptors-Mediated Apoptosis in Hormone-Dependent Cancers

It is known that estrogen stimulates growth and inhibits apoptosis through estrogen receptor(ER)-mediated mechanisms in many cancer cell types. Interestingly, there is strong evidence that estrogens can also induce apoptosis, activating different ER isoforms in cancer cells. It has been observed that E2/ERα complex activates multiple pathways involved in both cell cycle progression and apoptotic cascade prevention, while E2/ERβ complex in many cases directs the cells to apoptosis. However, the exact mechanism of estrogen-induced tumor regression is not completely known. Nevertheless, ERs expression levels of specific splice variants and their cellular localization differentially affect outcome of estrogen-dependent tumors. The goal of this review is to provide a general overview of current knowledge on ERs-mediated apoptosis that occurs in main hormone dependent-cancers. Understanding the molecular mechanisms underlying the induction of ER-mediated cell death will be useful for the development of specific ligands capable of triggering apoptosis to counteract estrogen-dependent tumor growth.

Mitochondrial translocation of estrogen receptor β affords resistance to oxidative insult-induced apoptosis and contributes to the pathogenesis of endometriosis

Endometriosis is the major cause of female infertility and has been linked to the action of estrogen and estrogen receptor (ER). A new pool of ERβ locates within mitochondria, which regulates the endometriotic cell withstanding external insults, but its effect remains controversial. We hypothesize that mitochondrial estrogen receptor ERβ (mtERβ) is a pivotal regulator in estradiol-mediated cell protection leading to the endometriotic progression. We observed elevated levels of ERβ in the endometriotic tissues. A dramatic increase of ERβ in mitochondria (mtERβ) was found in the ectopic endometriotic tissues, or the estradiol-primed primary endometriotic cells. We analyzed the mtERβ-specific overexpressing clone (mtsERβ), which exhibited higher mitochondrial bioenergetics and lower reactive oxygen species (ROS) generation. The mtsERβ-overexpressed endometriotic cells displayed an enhanced migration phenotype, whereas significantly attenuated migration by mitochondrial respiratory inhibitor (oligomycin) or ERβ deficiency by shERβ. Further investigations revealed that ERβ directly modulated mitochondrial DNA (mtDNA) gene expression by interacting with mtDNA D-loop and polymerase γ. The mtsERβ afforded a resistance to oxidative insult-induced apoptosis through the induction of the ROS scavenger enzyme Mn-superoxide dismutase and anti-apoptotic protein Bcl-2. Collectively, the demonstration of mtERβ responses in restoration of mitochondrial bioenergetics and inhibition of mitochondria-dependent apoptotic events provides insight into the pathogenesis of endometriosis, suggesting ERβ-selective estrogen receptor modulator may serve as novel therapeutics of endometriosis in the future.

A Selective Estrogen Receptor Beta Agonist for the Treatment of Hot Flushes: Phase 2 Clinical Trial

OBJECTIVE

The aim of this study was to evaluate the safety, tolerability, and efficacy of a selective estrogen receptor beta (ERβ) agonist, Dr. Tagliaferri's Menopause Formula (MF102), to treat the symptoms of menopause.

METHODS

An open-label trial of MF102 taken for 12 weeks by 30 postmenopausal women aged 40-65 years, who experienced a minimum of five moderate to severe hot flushes per day. The primary efficacy outcome was a change in the frequency of moderate to severe hot flushes from baseline to week 12. A change in the frequency of hot flushes that woke participants from their sleep from baseline to 12 weeks was a secondary endpoint. Lipid profile and endometrial thickness were also evaluated.

RESULTS

Thirty postmenopausal women with an average of nine moderate to severe hot flushes per day were treated with MF102 4 g/day; 27 participants completed the study. The median percent reduction in moderate to severe hot flushes was 71% (p < 0.001). The median percent reduction in hot flushes that woke participants from their sleep was 54% (p < 0.001). Low-density lipoprotein (LDL-C) and total cholesterol both declined significantly from baseline. There were no serious adverse events, reports of abnormal uterine bleeding, or significant changes in double-wall endometrial thickness.

CONCLUSIONS

Treatment with MF102 resulted in a marked decrease in the frequency of moderate to severe hot flushes, was well-tolerated, and demonstrated no safety concerns.

ERβ-dependent neuroglobin up-regulation impairs 17β-estradiol-induced apoptosis in DLD-1 colon cancer cells upon oxidative stress injury

Besides other mechanism(s) 17β-estradiol (E2) facilitates neuronal survival by increasing, via estrogen receptor β (ERβ), the levels of neuroglobin (NGB) an anti-apoptotic protein. In contrast, E2 could exert protective effects in cancer cells by activating apoptosis when the ERβ level prevails on that of ERα as in colon cancer cell lines. These apparently contrasting results raise the possibility that E2-induced NGB up-regulation could regulate the ERβ activities shunning this receptor subtype to trigger an apoptotic cascade in neurons but not in non-neuronal cells. Here, human colorectal adenocarcinoma cell line (DLD-1) that only expresses ERβ and HeLa cells transiently transfected with ERβ encoding vector has been used to verify this hypothesis. In addition, neuroblastoma SK-N-BE cells were used as positive control. Surprisingly, E2 also induced NGB up-regulation, in a dose- and time-dependent manner, in DLD-1 cells. The ERβ-mediated activation of p38/MAPK was necessary for this E2 effect. E2 induced NGB re-allocation in mitochondria where, subsequently to an oxidative stress injury (i.e., 100μM H2O2), NGB interacted with cytochrome c preventing its release into the cytosol and the activation of an apoptotic cascade. As a whole, these results demonstrate that E2-induced NGB up-regulation could act as an oxidative stress sensor, which does not oppose to the pro-apoptotic E2 effect in ERβ-containing colon cancer cells unless a rise of oxidative stress occurs. These results support the concept that oxidative stress plays a critical role in E2-induced carcinogenesis and further open an important scenario to develop novel therapeutic strategies that target NGB against E2-related cancers.

Differential expression patterns of estrogen receptor (ER)-β splice variants between papillary thyroid cancer and nodular thyroid goiter

Background

The aim of this study was to investigate the expression patterns of estrogen receptor (ER) β1 (wild-type ERβ) and ERβ2 (ERβcx) in papillary thyroid cancer (PTC) and nodular thyroid goiter (NTG), and to explore the reasons for the higher incidence of PTC in women of reproductive age.

Material/Methods

ERβ1 and ERβ2 expression was examined immunohistochemically on paraffin-embedded thyroid tissues from 106 patients with PTC and 30 patients with NTG.

Results

There was significant difference in the subcellular localization of ERβ1 (P<0.001), but not in the positive percentage, between PTC and NTG specimens. No significant difference was found in the positive percentage or the subcellular distribution of ERβ2 expression between PTC and NTG specimens. Both nuclear and nucleocytoplasmic ERβ1 expressions were significantly lower in PTC lesions than in NTG tissue (P<0.001 and P<0.05, respectively), while ERβ2 expression was significantly higher in the former than the latter (P<0.05). ERβ1 expression in reproductive-aged (18~45 years) female patients with PTC was lower than that in age-matched male patients (P<0.05), while ERβ2 expression had the opposite expression profile (P<0.05). There was no significant difference in ERβ1 and ERβ2 expression between reproductive-aged and advanced reproductive-aged (>45 years) female patients with PTC.

Conclusions

This preliminary study indicates that the expression patterns of ERβ1 and ERβ2 differ between malignant PTC lesions and benign NTG tissue, and their expression might be involved in the female predominance of PTC during the reproductive years. The clinical and biological significance of these results await further investigation.

Insulin-like growth factors in endometrioid adenocarcinoma: correlation with clinico-pathological features and estrogen receptor expression

Background

Endometrial carcinoma is a common malignancy of female genital tract. Insulin-like growth factor is known to elicit estrogen-induced mitogenic activity and anti-apoptotic effect in endometrial tissues.

Methods

The retrospective study investigated the expression of insulin-like growth factors, estrogen receptors and their associations in endometrioid adenocarcinoma (EAC) from 80 EAC patients in immunohistochemistry, and 58 EAC patients and 42 control patients in quantitative RT-PCR. The Pearson correlation analysis was used to analyze their correlations with clinic-pathological parameters.

Results

Our results showed that insulin-like growth factor-1 and insulin-like growth factor-2 mRNA levels were higher in tumor tissues and tumor-adjacent tissues than those in control cells, and were inversely correlated with the malignancy of the tumor with a positive correlation with ERα and ERβ expression. Insulin-like growth factor-1R protein expression was correlated with clinical stage, and insulin-like growth factor-2R protein expression was inversely correlated with histological grade.

Conclusions

Insulin-like growth factor system plays an important role in estrogen-induced endometrial carcinogenesis, and overexpression of insulin-like growth factor-1R in the advanced endometrioid adenocarcinoma is not estrogen-dependent.

Estrogen receptor-beta and breast cancer: translating biology into clinical practice

Estrogen receptor (ER) β was discovered over a decade ago. The design of most studies on this receptor was based on knowledge of its predecessor, ERα. Although breast cancer (BCa) has been a main focus of ERβ research, its precise roles in breast carcinogenesis remain elusive. Data from in vitro models have not always matched those from observational or clinical studies. Several inherent factors may contribute to these discrepancies: (a) several ERβ spliced variants are expressed at the protein level, and isoform-specific antibodies are unavailable for some variants; (b) post-translational modifications of the receptor regulate receptor functions; (c) the role of the receptor differs significantly depending on the type of ligands, cis-elements, and co-regulators that interact with the receptor; and (d) the diversity of distribution of the receptor among intracellular organelles of BCa cells. This review addresses the gaps in knowledge in ERβ research as it pertains to BCa regarding the following questions: (1) is ERβ a tumor suppressor in BCa?; (2) do ERβ isoforms play differential roles in breast carcinogenesis?; (3) do nuclear signaling and extranuclear ERβ signaling differ in BCa?; (4) what are the consequences of post-translational modifications of ERβ in BCa?; (5) how do co-regulators and interacting proteins increase functional diversity of ERβ?; and (6) how do the types of ligand and regulatory cis-elements affect the action of ERβ in BCa?. Insights gained from these key questions in ERβ research should help in prevention, diagnosis/prognosis, and treatment of BCa.

Endometrial expression of estrogen receptor β and its splice variants in patients with and without endometriosis

BACKGROUND

The role of estrogen receptor beta (ERβ) in pathogenesis of endometriosis remains to be elucidated. In this study, we have examined the expression of the four main ERβ transcript isoforms in human endometrial tissue in women with or without endometriosis.

METHODS

Total RNA was isolated from native endometrial tissue and transcript levels of ERα, β1, β2, β4, β5 were analyzed by means of RT-PCR. We compared the results with regard to menstrual cycle phase as well as to presence or absence of endometriosis. We prospectively harvested the endometrium of ten women without endometriosis (five for each cycle phase) and eight patients with endometriosis (five in the proliferative phase, three in the secretory phase).

RESULTS

ERα, β1, β2, and β5 transcripts were detected in both cycle phases. During the proliferative phase, healthy women had a significantly higher ERα/ERβ1-ratio than patients with endometriosis. Irrespective of the cycle phase, ERα-mRNA level was significantly higher than transcript levels of ERβ isoforms.

CONCLUSIONS

ERα, β1, β2, and β5 are expressed in human endometrium. The individual receptors differed in terms of expression strength but there was no relevant change during the cycle. The decreased ERα/ERβ1-ratio in proliferative endometrium of endometriosis patients suggest that ERβ1 might be involved in the pathogenesis of endometriosis. Further studies should be undertaken to substantiate the role of ERβ in endometrial pathology.

Steroid receptors, HER2/neu and Ki-67, in endometrioid type of endometrial carcinoma: Correlation with conventional histomorphological features of prognosis

Endometrial proliferation is regulated by steroid receptors such as estrogen receptor alpha (ERalpha), estrogen receptor beta (ERbeta) and progesterone receptor (PR). HER2/neu is an important growth factor receptor which affects cell proliferation and Ki67 is a marker of cellular proliferation. Their interaction in endometrioid type of endometrial carcinoma is still not fully understood. In this study, we analyzed the immunolocalisation of ERalpha and ERbeta with particular attention to the ERbetacx isoform, PR, HER2/neu and Ki67 in endometrioid carcinoma. Their correlations with each other and with the conventional morphological prognostic parameters of myoinvasion and tumor grade were analyzed with respect to overall survival. Out of a total 54 cases, 14 showed evidence of local recurrence or metastatic disease within 5 years with poor outcome, whereas the rest had no evidence of disease. ERalpha, ERbeta, ERbetacx, PR, HER2/neu and Ki67 were detected using immunohistochemistry. The histological grade of the tumor correlated inversely with the intensity of immunolabelling of ERalpha and PR, and this was highly significant. The depth of myoinvasion showed an inverse correlation only with the ERbeta2/betacx immunopositivity and was not significantly associated with any other receptor evaluated. Analysis of the inter-relationship between receptor immunopositivity revealed a significant association of ERalpha immunolocalisation with ERbeta and with PR. Immunodetection of HER2/neu receptor correlated positively with both ERalpha and PR immunolabelling. The Ki-67 proliferation index correlated only with ERalpha immunopositivity. Preliminary observations suggested that with the exception of ERalpha, there was no correlation of any of the receptors evaluated with survival.

Expression of oestrogen receptors, ERalpha, ERbeta, and ERbeta variants, in endometrial cancers and evidence that prostaglandin F may play a role in regulating expression of ERalpha

Background

Endometrial cancer is the most common gynaecological malignancy; risk factors include exposure to oestrogens and high body mass index. Expression of enzymes involved in biosynthesis of oestrogens and prostaglandins (PG) is often higher in endometrial cancers when compared with levels detected in normal endometrium. Oestrogens bind one of two receptors (ERα and ERβ) encoded by separate genes. The full-length receptors function as ligand-activated transcription factors; splice variant isoforms of ERβ lacking a ligand-binding domain have also been described. PGs act in an autocrine or paracrine manner by binding to specific G-protein coupled receptors.

Methods

We compared expression of ERs, progesterone receptor (PR) and cyclooxygenase-2 (COX-2) in stage 1 endometrial adenocarcinomas graded as well (G1), moderately (G2) or poorly (G3) differentiated (n ≥ 10 each group) using qRTPCR, single and double immunohistochemistry. We used endometrial adenocarcinoma cell lines to investigate the impact of PGF2α on expression of ERs and PR.

Results

Full length ERβ (ERβ1) and two ERβ variants (ERβ2, ERβ5) were expressed in endometrial cancers regardless of grade and the proteins were immunolocalised to the nuclei of cells in both epithelial and stromal compartments. Immunoexpression of COX-2 was most intense in cells that were ERα^neg/low. Expression of PR in endometrial adenocarcinoma (Ishikawa) cell lines and tissues broadly paralleled that of ERα. Treatment of adenocarcinoma cells with PGF2α reduced expression of ERα but had no impact on ERβ1. Cells incubated with PGF2α were unable to increase expression of PR mRNA when they were incubated with E2.

Conclusion

We have demonstrated that ERβ5 protein is expressed in stage 1 endometrial adenocarcinomas. Expression of three ERβ variants, including the full-length protein is not grade-dependent and most cells in poorly differentiated cancers are ERβ^pos/ERα^neg. We found evidence of a link between COX-2, its product PGF2α, and expression of ERα and PR that sheds new light on the cross talk between steroid and PG signalling pathways in this disease.

MF101, a selective estrogen receptor beta modulator for the treatment of menopausal hot flushes: a phase II clinical trial

OBJECTIVE

To determine the optimal dose, safety, and efficacy of an estrogen receptor beta selective Chinese herbal extract, menopausal formula 101 (MF101), for treating hot flushes.

METHODS

A randomized, blinded trial in 217 postmenopausal women with hot flushes randomized to 5 or 10 g/day of MF101 or placebo for 12 weeks.

RESULTS

The effects of 5 g/day of MF101 did not differ from those of placebo. After 12 weeks, the mean percent decrease in frequency of hot flushes in the 10 g/day group was 12.9% greater than that in the placebo group (P = 0.15), the median percent decrease was 11.7% greater than that in the placebo group (P = 0.05), and the proportion of women with at least a 50% reduction in hot flushes was 16.2% greater than that in the placebo group (P = 0.03).

CONCLUSIONS

Treatment with 10 g/day of MF101 reduces the frequency of hot flushes. Trials with higher doses are planned.

Oestrogen receptor splice variants in the pathogenesis of disease

The full-length oestrogen receptor (ER) exists in most vertebrates as two separately encoded isoforms. ER splice variants represent truncated or otherwise modified versions of the full-length alpha or beta isoforms of the parent receptor. ERalpha is found on chromosome 6q and encodes a 595 amino acid protein, while ERbeta is found on chromosome 14q and encodes a 530 amino acid protein. These receptors possess differing ligand affinities, are differentially expressed in a tissue-specific fashion and may act antagonistically. Their altered expression has been implicated in the pathophysiology of a diverse range of conditions from cancer progression in hormone-responsive tissues to neurodegenerative disease. Variously co-expressed with full-length ERs, ER splice variants may have a positive or negative influence on transcription either by modifying the effect of the parent receptor or through their own intrinsic activity. To date, the vast majority of studies have used generic primers or antibodies against the full-length receptors and would not distinguish ER-mediated effects associated with various splice variants. Thus the evidence base of the influence of ER splice variants in normal developmental physiology and in the pathogenesis of disease is weak and greater understanding of their role will undoubtedly lead to new therapeutic strategies for disease intervention and treatment. This review aims to compile the current evidence for the presence of ER splice variants in humans, their physiological roles and clinical sequelae.

Estrogen receptor beta (ERbeta) in endometrial simple hyperplasia and endometrioid carcinoma

AIMS

The aim of this study was to analyze the expression of estrogen receptor (ER) beta in endometrioid carcinoma in comparison to non-neoplastic endometrium.

METHODS

Fifty-seven histopathologically confirmed non-neoplastic endometria (22 proliferative phase, 15 secretory phase, and 20 simple hyperplasia without atypia), and 26 cases of endometrioid carcinoma were studied. The ERbeta/ERalpha transcript ratio was determined by semiquantitative reverse transcription-polymerase chain reaction. The receptor protein expression was evaluated by immunohistochemistry using the Allred Scoring System.

RESULTS

Decreased expression of ERbeta, ERalpha, and progesterone receptor proteins was observed in endometrioid carcinoma compared with proliferative endometrium and simple hyperplasia (P<0.01, Mann-Whitney U test). Within the group of endometrioid carcinoma, a correlation of increased ERbeta expression with tumors exhibiting > or =50% myoinvasion (P=0.034) was observed, whereas there was no correlation with the grade of tumor (P=0.314). There was a significant association of ERbeta with ERalpha expression in both non-neoplastic and neoplastic endometrium indicating interdependence of expression. Progesterone receptor protein expression was influenced by ERalpha levels and not by ERbeta as shown by regression analysis in non-neoplastic and neoplastic endometrium.

CONCLUSIONS

Thus, ERbeta alterations are important in endometrioid carcinoma. The relationship of ERbeta expression to myoinvasion warrants further investigation.

Estrogen and its receptors in cancer

The involvement of estrogen and its receptors in the development of cancer has been known for years. However, the exact mechanism responsible is far from clear. The estrogen-mediated carcinogenic process is complicated by recent findings, which reveal that estrogens have multiple functions in cells, which can be either adverse or beneficial, and that the effects of estrogen may be cell-type or organ dependent. The estrogenic effect may be also greatly influenced by the state of two estrogen receptors, ERalpha and ERbeta. This review will discuss the role and function of estrogens and its receptors in cancers of three categories: (1) Breast cancer and gynecologic cancers, (2) Cancers of endocrine organs, (3) Lung cancer and cancers of digestive system. We will also review some novel treatments aiming to interfere with relevant pathways mediated by estrogens and its receptors.

Hormonal heterogeneity of endometrial cancer

Endometrial cancer is the most common malignant tumor of the female genital tract in the developed world. Increasing evidence suggests that the majority of cases can be divided into two different types ofendometrial cancer based on clinico-pathological and molecular characteristics. Type I is associated with an endocrine milieu of estrogen predominance. These tumors are ofendometroid histology and develop from endometrial hyperplasia. They have good prognosis and are sensitive to endocrine treatment. Type II endometrial cancers are not associated with a history of unopposed estrogens and develop from the atrophic endometrium of elderly women. Mainly, they are of serous papillary or clear cell morphology, have a poor prognosis and do not react to endocrine treatment. Both types of endometrial cancer probably differ markedly with regard to the molecular mechanisms of transformation. The transition from normal endometrium to a malignant tumor is thought to involve a stepwise accumulation of alterations in cellular mechanisms leading to dysfunctional cell growth. This chapter reviews the current knowledge of the molecular mechanisms commonly associated with development of type I and type II endometrial cancer.