The G protein-coupled receptor GPR30 mediates the proliferative and invasive effects induced by hydroxytamoxifen in endometrial cancer cells

Evaluation of the effects of estrogens on endometrial cancer cells of different grades

Endometrial cancer (EC) is the most common gynecological malignancy in the Western world. The molecular basis and effects of various agents are frequently studied in model EC cell lines, but the most commonly used cell lines Ishikawa, HEC-1-A, RL95-2 and KLE have not been thoroughly and systematically investigated. We characterized EC cell lines of different grades by reassessing the expression of estrogen receptors ERα, ERβ, and GPER by qPCR and Western blot and investigated the effects of estrogens, estrone-sulfate, estrone and estradiol on their proliferation, migration, and clonogenicity. Estradiol promoted the proliferation of grade 1 Ishikawa EC cells and grade 2 RL95-2 cells. Estrone and estrone sulfate also stimulated the proliferation of Ishikawa, showed a tendency to increase the proliferation of HEC-1-A and RL95-2 cells, but decreased the proliferation of KLE. Estrogens had no effect on the migration and clonogenicity of these four EC cell lines, however, there was a trend toward a smaller colony area for cells incubated with higher estrogen concentrations. We have previously shown that in EC estradiol forms from inactive estrone sulfate via the sulfatase pathway. This study showed that estrogens significantly promote the proliferation of grade 1 Ishikawa EC cells, and grade 2 RL95-2 and decrease the proliferation of grade 3 KLE cells. These differences in proliferation were associated with ERα positivity of Ishikawa cells and GPER expression in other cells.

Estrogen Promotes the Proliferation and Migration of Endometrial Cancer Through the GPER-Mediated NOTCH Pathway

This study aims to investigate the expression of GPER in EC, assess the impact of estrogen on the proliferation and migration of EC via GPER, and examine the potential role of GPER in mediating the NOTCH pathway to influence EC proliferation and migration. The expression of GPER and its correlation with clinicopathological features were investigated using clinical data. Cell proliferation was assessed through MTT and EdU assays, while cell migration ability was evaluated using wound healing and transwell assays. Western blot analysis was conducted to detect proteins associated with the GPER and NOTCH signaling pathways. Additionally, xenograft tumor models were established to investigate the potential role of estrogen in mediating the NOTCH pathway via GPER. The results demonstrated a significant upregulation of GPER expression in EC, which was associated with clinical stage and metastasis. In vitro experiments provided evidence that estrogen promotes EC cell proliferation and metastasis by enhancing the expression levels of GPER, Notch1, and Hes-1 proteins. Conversely, knocking down or suppressing GPER effectively reverses these effects. Furthermore, treatment with JAG-1, an agonist for the NOTCH pathway, counteracts si-GPER's inhibitory impact on both proliferation and migration abilities of EC cells while increasing Notch1 and Hes-1 protein expression levels; however, it does not alter GPER expression. In vivo experiments have substantiated that estrogen facilitates EC proliferation via the GPER-mediated NOTCH pathway.

Effect of Diosgenin in Suppressing Viability and Promoting Apoptosis of Human Prostate Cancer Cells: An Interplay with the G Protein-Coupled Oestrogen Receptor?

Diosgenin is a phytosteroid sapogenin with reported antitumoral activity. Despite the evidence indicating a lower incidence of prostate cancer (PCa) associated with a higher consumption of phytosteroids and the beneficial role of these compounds, only a few studies have investigated the effects of diosgenin in PCa, and its mechanisms of action remain to be disclosed. The present study investigated the effect of diosgenin in modulating PCa cell fate and glycolytic metabolism and explored its potential interplay with G protein-coupled oestrogen receptor (GPER). Non-neoplastic (PNT1A) and neoplastic (LNCaP, DU145, and PC3) human prostate cell lines were stimulated with diosgenin in the presence or absence of the GPER agonist G1 and upon GPER knockdown. Diosgenin decreased the cell viability, as indicated by the MTT assay results, which also demonstrated that castrate-resistant PCa cells were the most sensitive to treatment (PC3 > DU145 > LNCaP > PNT1A; IC50 values of 14.02, 23.21, 56.12, and 66.10 µM, respectively). Apoptosis was enhanced in diosgenin-treated cells, based on the increased caspase-3-like activity, underpinned by the altered expression of apoptosis regulators evaluated by Western blot analysis, which indicated the activation of the extrinsic pathway. Exposure to diosgenin also altered glucose metabolism. Overall, the effects of diosgenin were potentiated in the presence of G1. Moreover, diosgenin treatment augmented GPER expression, and the knockdown of the GPER gene suppressed the proapoptotic effects of diosgenin in PC3 cells. Our results support the antitumorigenic role of diosgenin and its interest in PCa therapy, alone or in combination with G1, mainly targeting the more aggressive stages of the disease.

The influence of sex hormones on renal cell carcinoma

Kidney cancer is a common malignancy that constitutes around 5% of all cancer cases. Males are twice as likely to acquire renal cell carcinoma (RCC) compared to females and experience a higher rate of mortality. These disparities indicate that sex hormone (SH)-dependent pathways may have an impact on the aetiology and pathophysiology of RCC. Examination of SH involvement in conventional signalling pathways, as well as genetics and genomics, especially the involvement of ribonucleic acid, reveal further insights into sex-related differences. An understanding of SHs and their influence on kidney cancer is essential to offer patients individualized medicine that would better meet their needs in terms of prevention, diagnosis and treatment. This review presents the understanding of sex-related differences in the clinical manifestation of kidney cancer patients and the underlying biological processes.

Targeting the crosstalk between estrogen receptors and membrane growth factor receptors in breast cancer treatment: Advances and opportunities

Estrogens play a critical role in the initiation and progression of breast cancer. Estrogen receptor (ER)α, ERβ, and G protein-coupled estrogen receptor are the primary receptors for estrogen in breast cancer. These receptors are mainly activated by binding with estrogens. The crosstalk between ERs and membrane growth factor receptors creates additional pathways that amplify the effects of their ligands and promote tumor growth. This crosstalk may cause endocrine therapy resistance in ERα-positive breast cancer. Furthermore, this may explain the resistance to anti-human epidermal growth factor receptor-2 (HER2) treatment in ERα-/HER2-positive breast cancer and chemotherapy resistance in triple-negative breast cancer. Accordingly, it is necessary to understand the complex crosstalk between ERs and growth factor receptors. In this review, we delineate the crosstalk between ERs and membrane growth factor receptors in breast cancer. Moreover, this review highlights the current progress in clinical treatment and discusses how pharmaceuticals target the crosstalk. Lastly, we discuss the current challenges and propose potential solutions regarding the implications of targeting crosstalk via pharmacological inhibition. Overall, the present review provides a landscape of the crosstalk between ERs and membrane growth factor receptors in breast cancer, along with valuable insights for future studies and clinical treatments using a chemotherapy-sparing regimen to improve patient quality of life.

The beneficial effects of tamoxifen on arteries: a key player for cardiovascular health of breast cancer patient

Breast cancer is the most common cancer in women. Over the past few decades, advances in cancer detection and treatment have significantly improved survival rate of breast cancer patients. However, due to the cardiovascular toxicity of cancer treatments (chemotherapy, anti-HER2 antibodies and radiotherapy), cardiovascular diseases (CVD) have become an increasingly important cause of long-term morbidity and mortality in breast cancer survivors. Endocrine therapies are prescribed to reduce the risk of recurrence and specific death in estrogen receptor-positive (ER+) early breast cancer patients, but their impact on CVD is a matter of debate. Whereas aromatase inhibitors and luteinizing hormone-releasing hormone (LHRH) analogs inhibit estrogen synthesis, tamoxifen acts as a selective estrogen receptor modulator (SERM), opposing estrogen action in the breast but mimicking their actions in other tissues, including arteries. This review aims to summarize the main clinical and experimental studies reporting the effects of tamoxifen on CVD. In addition, we will discuss how recent findings on the mechanisms of action of these therapies may contribute to a better understanding and anticipation of CVD risk in breast cancer patients.

G-protein couple receptor (GPER1) plays an important role during ovarian folliculogenesis and early development of the Chinese Alligator

The critical role of the G protein-coupled receptor 1 (GPER1), a member of the seven-transmembrane G protein-coupled receptor family, in the functional regulation of oocytes accumulated abundant theories in the early research on model animals. However, the full-length cDNA encoding GPER1 and its role in the folliculogenesis has not been illustrated in crocodilians. 0.5, 3, and 12 months old Alligator sinensis cDNA samples were used to clone the full-length cDNA encoding GPER1. Immunolocalization and quantitative analysis were performed using Immunofluorescence technique, RT-PCR and Western blot. Simultaneously, studies on GPER1's promoter deletion and cis-acting transcriptional regulation mechanism were conducted. Immunolocalization staining for the germline marker DDX4 and GPER1 demonstrated that DDX4-positive oocytes were clustered tightly together within the nests, whereas scarcely any detectable GPER1 was present in the oocytes nest in Stage I. After that, occasionally GPER1-positive immunosignal was observed in oocytes and somatic cells additional with the primordial follicles, and it was mainly located at the granulosa cells or thecal cells within the early PFs in the Stage III. The single mutation of the putative SP1 motif, double mutating of Ets/SP1 and SP1/CRE binding sites all depressed promoter activities. This result will help to investigate the role of GPER1 in the early folliculogenesis of A. sinensis.

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.

Estrogen and the Vascular Endothelium: The Unanswered Questions

Premenopausal women have a lower incidence of cardiovascular disease (CVD) compared with their age-matched male counterparts; however, this discrepancy is abolished following the transition to menopause or during low estrogen states. This, combined with a large amount of basic and preclinical data indicating that estrogen is vasculoprotective, supports the concept that hormone therapy could improve cardiovascular health. However, clinical outcomes in individuals undergoing estrogen treatment have been highly variable, challenging the current paradigm regarding the role of estrogen in the fight against heart disease. Increased risk for CVD correlates with long-term oral contraceptive use, hormone replacement therapy in older, postmenopausal cisgender females, and gender affirmation treatment for transgender females. Vascular endothelial dysfunction serves as a nidus for the development of many cardiovascular diseases and is highly predictive of future CVD risk. Despite preclinical studies indicating that estrogen promotes a quiescent, functional endothelium, it still remains unclear why these observations do not translate to improved CVD outcomes. The goal of this review is to explore our current understanding of the effect of estrogen on the vasculature, with a focus on endothelial health. Following a discussion regarding the influence of estrogen on large and small artery function, critical knowledge gaps are identified. Finally, novel mechanisms and hypotheses are presented that may explain the lack of cardiovascular benefit in unique patient populations.

Estrogen receptors as potential therapeutic target in endometrial cancer

Endometrial cancer (EC) is one of the most common gynecological carcinomas in both developed and developing countries. Majority of the gynecological malignancies are hormonally driven where estrogen signaling acts as an oncogenic signal. Estrogen's effects are mediated via classical nuclear estrogen receptors; estrogen receptor alpha and beta (ERα and ERβ) and a trans-membrane G protein-coupled estrogen receptor (GPR30 and GPER). ERs and GPER through ligand binding triggers multiple downstream signaling pathways causing cell cycle regulation, cell differentiation, migration, and apoptosis in various tissues including endometrium. Although the molecular aspect of estrogen function in ER-mediated signaling is now partly understood, the same is not true for GPER-mediated signaling in endometrial malignancies. Understanding the physiological roles of ERα and GPER in EC biology therefore leads to the identification of some novel therapeutic targets. Here we review the effect of estrogen signaling through ERα-and GPER in EC, major types, and some affordable treatment approaches for endometrial tumor patients which has interesting implications in understanding uterine cancer progression.

The immunohistochemical expression of GPER and classical sex hormone receptors differs in adenomyosis and eutopic endometrium

G protein-coupled estrogen receptor (GPER) has been found to be an important key regulator in the homeostasis of sex hormone-dependent human cells. The aim of this study was to compare the expression of GPER, estrogen receptor alpha (ER-α), estrogen receptor beta (ER-β) and progesterone receptor (PR) in adenomyosis, eutopic endometrium from the same patients, and eutopic endometrium from patients without adenomyosis. Immunohistochemical analysis of GPER, ER-α, ER-β and PR was performed to assess the expression levels on samples of hysterectomies using tissue microarrays. 73 adenomyotic tissue probes and corresponding eutopic endometrial specimens, as well as 48 samples of eutopic endometrial control specimens from patients without adenomyosis were included in this study. Mean age of the women with adenomyosis was 51.7 (SD ± 11.1) and 65.8% were premenopausal. We found a higher nuclear stromal expression of GPER in eutopic endometrium of patients with adenomyosis in comparison to control endometrium (p < 0.001). Comparing adenomyosis to eutopic endometrium of patients with adenomyosis and to control, there was a lower expression of nuclear GPER in epithelial cells (p < 0.001 and p = 0.048, respectively). Lower epithelial nuclear ER-α in adenomyosis and higher epithelial nuclear ER-β in eutopic endometrium of patients with adenomyosis was found in comparison to control endometrium (p = 0.008 and p = 0.017, respectively). This study showed a significant difference in the immunohistochemical expression of GPER in adenomyosis compared to eutopic endometrium of the same patients and to endometrium of control group. GPER in adenomyosis may be a potential therapeutic target for selective agonists and antagonists.

The Co-Expression of Estrogen Receptors ERα, ERβ, and GPER in Endometrial Cancer

Estrogens have important roles in endometrial cancer (EC) and exert biological effects through the classical estrogen receptors (ERs) ERα and ERβ, and the G-protein-coupled ER, GPER. So far, the co-expression of these three types of ERs has not been studied in EC. We investigated ERα, ERβ, GPER mRNA and protein levels, and their intracellular protein distributions in EC tissue and in adjacent control endometrial tissue. Compared to control endometrial tissue, immunoreactivity for ERα in EC tissue was weaker for nuclei with minor, but unchanged, cytoplasmic staining; mRNA and protein levels showed decreased patterns for ERα in EC tissue. For ERβ, across both tissue types, the immunoreactivity was unchanged for nuclei and cytoplasm, although EC tissues again showed lower mRNA and protein levels compared to adjacent control endometrial tissue. The immunoreactivity of GPER as well as mRNA levels of GPER were unchanged across cancer and control endometrial tissues, while protein levels were lower in EC tissue. Statistically significant correlations of estrogen receptor α (ESR1) versus estrogen receptor β (ESR2) and GPER variant 3,4 versus ESR1 and ESR2 was seen at the mRNA level. At the protein level studied with Western blotting, there was significant correlation of ERα versus GPER, and ERβ versus GPER. While in clinical practice the expression of ERα is routinely tested in EC tissue, ERβ and GPER need to be further studied to examine their potential as prognostic markers, provided that specific and validated antibodies are available.

Tetrachlorobisphenol A and bisphenol AF induced cell migration by activating PI3K/Akt signaling pathway via G protein-coupled estrogen receptor 1 in SK-BR-3 cells

Different subtypes of breast cancer express positively G protein-coupled estrogen receptor 1 (GPER1). Our previous studies found that tetrachlorobisphenol A (TCBPA) and bisphenol AF (BPAF) significantly promoted SK-BR-3 cell proliferation by activating GPER1-regulated signals. The present study further investigated the effects of TCBPA and BPAF on the migration of SK-BR-3 cells and examined the role of phosphatidylinositol 3-kinase-protein kinase B (PI3K/Akt) and its downstream signal targets in this process. We found that low-concentration BPAF and TCBPA markedly accelerated the migration of SK-BR-3 cells and elevated the mRNA levels of target genes associated with PI3K/Akt and mitogen-activated protein kinase (MAPK) signals. TCBPA- and BPAF-induced upregulation of target genes was significantly reduced by GPER1 inhibitor G15, the PI3K/Akt inhibitor wortmannin (WM), and the epidermal growth factor receptor (EGFR) inhibitor ZD1839 (ZD). G15 and WM also decreased cell migration induced by TCBPA and BPAF. The findings revealed that TCBPA and BPAF promoted SK-BR-3 cell migration ability by activating PI3K/Akt signaling pathway via GPER1-EGFR.

Therapeutic and prognostic potential of GPCRs in prostate cancer from multi-omics landscape

Prostate cancer (PRAD) is a common and fatal malignancy. It is difficult to manage clinically due to drug resistance and poor prognosis, thus creating an urgent need for novel therapeutic targets and prognostic biomarkers. Although G protein-coupled receptors (GPCRs) have been most attractive for drug development, there have been lack of an exhaustive assessment on GPCRs in PRAD like their molecular features, prognostic and therapeutic values. To close this gap, we herein systematically investigate multi-omics profiling for GPCRs in the primary PRAD by analyzing somatic mutations, somatic copy-number alterations (SCNAs), DNA methylation and mRNA expression. GPCRs exhibit low expression levels and mutation frequencies while SCNAs are more prevalent. 46 and 255 disease-related GPCRs are identified by the mRNA expression and DNA methylation analysis, respectively, complementing information lack in the genome analysis. In addition, the genomic alterations do not exhibit an observable correlation with the GPCR expression, reflecting the complex regulatory processes from DNA to RNA. Conversely, a tight association is observed between the DNA methylation and mRNA expression. The virtual screening and molecular dynamics simulation further identify four potential drugs in repositioning to PRAD. The combination of 3 clinical characteristics and 26 GPCR molecular features revealed by the transcriptome and genome exhibit good performance in predicting progression-free survival in patients with the primary PRAD, providing candidates as new biomarkers. These observations from the multi-omics analysis on GPCRs provide new insights into the underlying mechanism of primary PRAD and potential of GPCRs in developing therapeutic strategies on PRAD.

Membrane-Initiated Estrogen, Androgen, and Progesterone Receptor Signaling in Health and Disease

Rapid effects of steroid hormones were discovered in the early 1950s, but the subject was dominated in the 1970s by discoveries of estradiol and progesterone stimulating protein synthesis. This led to the paradigm that steroid hormones regulate growth, differentiation, and metabolism via binding a receptor in the nucleus. It took 30 years to appreciate not only that some cellular functions arise solely from membrane-localized steroid receptor (SR) actions, but that rapid sex steroid signaling from membrane-localized SRs is a prerequisite for the phosphorylation, nuclear import, and potentiation of the transcriptional activity of nuclear SR counterparts. Here, we provide a review and update on the current state of knowledge of membrane-initiated estrogen (ER), androgen (AR) and progesterone (PR) receptor signaling, the mechanisms of membrane-associated SR potentiation of their nuclear SR homologues, and the importance of this membrane-nuclear SR collaboration in physiology and disease. We also highlight potential clinical implications of pathway-selective modulation of membrane-associated SR.

The smoking estrogens - a potential synergy between estradiol and benzo(a)pyrene

According to recent statistics, Lung Cancer (LC) is one of the most frequently diagnosed tumor types, representing nearly 12% of all global cancer cases. Moreover, in recent years, an increased mortality rate and incidence of this cancer were observed, especially among nonsmokers. Lung cancer patients are often characterized by poor prognosis and low survival rates, which encourages the scientific community to investigate the biochemical and molecular processes leading to the development of this malignancy. Furthermore, the mechanisms of LC formation and progression are not yet fully elucidated due to their high complexity, as well as a multitude of environmental, genetic, and molecular factors involved. Even though LC's association with exposure to cigarette smoke is indisputable, current research provides evidence that the development of this cancer can also be affected by the presence of estrogens and their interaction with several tobacco smoke components. Hence, the main goal of this brief review was to investigate reports of a possible synergy between 17β estradiol (E2), the most biologically active estrogen, and benzo(a)pyrene (BaP), a strongly carcinogenic compound produced as a result of incomplete tobacco combustion. The literature sources demonstrate a possible carcinogenic synergy between estrogens, especially E2, and BaP, a toxic tobacco smoke component. Therefeore, the combined effect of disturbed estrogen production in cancer cells, as well as the molecular influence exerted by BaP, could explain the increased aggressiveness and rate of LC development. Summarizing, the synergistic effect of these risk factors is an interesting area of further research.

Molecular mechanism study of BPAF-induced proliferation of ERα-negative SKBR-3 human breast cancer cells in vitro/in vivo

Bisphenol AF (BPAF) is a known estrogen disruptor of the ERα pathway. The aim of the present study was to characterize the proliferation effects of BPAF on ERα-negative SKBR-3 breast cancer cells with mechanistic insights. BPAF at low concentrations (0.001-0.1 μM) significantly induced the proliferation of SKBR-3 cells. In a SKBR-3 tumor model in BALB/c nude mice, BPAF at 100 mg/kg body weight/day also significantly promoted the growth of SKBR-3 tumors. Low concentrations of BPAF markedly increased the expression of G protein-coupled estrogen receptor (GPER1), c-Myc, CyclinD1 and c-Fos proteins, and enhanced phosphorylation of extracellular signal-regulated kinase (Erk) and protein kinase B (Akt) in SKBR-3 cells. Further, BPAF significantly upregulated mRNA levels of related target genes in SKBR-3 cells and SKBR-3 tumor tissues in nude mice. The GPER1 inhibitor G15 and phosphatidylinositide 3-kinase (PI3K) inhibitor wortmannin (WM) inhibited phosphorylation of Erk and Akt. The specific signal inhibitors also markedly decreased the expression of target genes and weakened the cell proliferation induced by low-concentration BPAF. The findings showed that GPER1 could independently regulate BPAF-induced proliferation of SKBR-3 cells without requiring ERα. These results provide mechanistic insights into the effects of BPAF regarding ERα-negative human breast cancer development.

Insight into the mechanism of tetrachlorobisphenol A (TCBPA)-induced proliferation of breast cancer cells by GPER-mediated signaling pathways

Tetrachlorobisphenol A (TCBPA), a chlorinated derivative of bisphenol A, is an endocrine disruptor based on interaction with nuclear estrogen receptor alpha (ERα). However, there is only limited data on the mechanisms through which TCBPA-associated estrogenic activity is related to the membrane G protein-coupled estrogen receptor (GPER) pathway. In this study, three human breast cancer cell lines-MCF-7, SKBR3, and MDA-MB-231 cells were used to evaluate whether, as well as how, TCBPA at concentration range of 0.001-50 μM affect cell proliferation. The role of GPER signaling in TCBPA-induced cell proliferation was studied by analyzing the protein expression and mRNA levels of relevant signal targets. The results showed that low concentrations of TCBPA significantly induced the proliferation of MCF-7, SKBR3, and MDA-MB-231 cells, with MCF-7 cells being the most sensitive to TCBPA exposure. Low-concentration TCBPA also upregulated the expression of GPER, CyclinD1, c-Myc, and c-Fos proteins, as well as increased the phosphorylation of extracellular signal-regulated-kinase 1/2 (Erk1/2) and protein kinase B (Akt). Additionally, the mRNA levels of genes associated with estrogen signaling pathways also increased upon exposure to TCBPA. However, the phosphorylation of Erk1/2 and Akt decreased when the cells were treated with GPER inhibitor G15 and phosphatidylinositide 3-kinase (PI3K) inhibitor wortmannin (WM) prior to TCBPA exposure. Besides, the increased proliferation of breast cancer cells induced by TCBPA were also inhibited. In ERα-positive MCF-7 cells, TCBPA also upregulated ERα expression, and ERα was found to interact with GPER-mediated signaling. The results indicate that GPER activates the PI3K/Akt and Erk1/2 signal cascades to drive the cell proliferation observed for low concentrations of TCBPA. The presented results suggest a new mechanism by which TCBPA exerts estrogenic action in breast cancer cells, namely, GPER signaling in an ERα-independent manner, and also highlights the potential risks to human health of the usage of TCBPA.

GPER1 Signaling Initiates Migration of Female V-SVZ-Derived Cells

In the rodent ventricular-subventricular zone (V-SVZ) neurons are generated throughout life. They migrate along the rostral migratory stream (RMS) into the olfactory bulb before their final differentiation into interneurons and integration into local circuits. Estrogen receptors (ERs) are steroid hormone receptors with important functions in neurogenesis and synaptic plasticity. In this study, we show that the ER GPER1 is expressed in subsets of cells within the V-SVZ of female animals and provide evidence for a potential local estrogen source from aromatase-positive astrocytes surrounding the RMS. Blocking of GPER1 in Matrigel cultures of female animals significantly impairs migration of V-SVZ-derived cells. This outgrowth is accompanied by regulation of phosphorylation of the actin-binding protein cofilin by GPER1 signaling including an involvement of the p21-Ras pathway. Our results point to a prominent role of GPER1 in the initiation of neuronal migration from the V-SVZ to the olfactory bulb.

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GPER1 is expressed within all cell types of the stem cell lineage in the V-SVZ

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Blocking of GPER1 leads to a decrease in migration of V-SVZ-derived neuroblasts

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GPER1 signaling in V-SVZ Matrigel cultures involves Ras-induced p21

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Blocking of GPER1 signaling leads to an increase in the ratio of p-cofilin/cofilin

Synthesis and In Vitro Evaluation of Tetrahydroquinoline Derivatives as Antiproliferative Compounds of Breast Cancer via Targeting the GPER

BACKGROUND

Some reports have demonstrated the role of the G Protein-coupled Estrogen Receptor (GPER) in growth and proliferation of breast cancer cells.

OBJECTIVE

In an effort to develop new therapeutic strategies against breast cancer, we employed an in silico study to explore the binding modes of tetrahydroquinoline 2 and 4 to be compared with the reported ligands G1 and G1PABA.

METHODS

This study aimed to design and filter ligands by in silico studies determining their Lipinski's rule, toxicity and binding properties with GPER to achieve experimental assays as anti-proliferative compounds of breast cancer cell lines.

RESULTS

In silico studies suggest as promissory two tetrahydroquinoline 2 and 4 which contain a carboxyl group instead of the acetyl group (as is needed for G1 synthesis), which add low (2) and high hindrance (4) chemical moieties to explore the polar, hydrophobic and hindrance effects. Docking and molecular dynamics simulations of the target compounds were performed with GPER to explore their binding mode and free energy values. In addition, the target small molecules were synthesized and assayed in vitro using breast cancer cells (MCF-7 and MDA-MB-231). Experimental assays showed that compound 2 decreased cell proliferation, showing IC50 values of 50µM and 25µM after 72h of treatment of MCF-7 and MDA-MB-231 cell lines, respectively. Importantly, compound 2 showed a similar inhibitory effect on proliferation as G1 compound in MDA-MB-231 cells, suggesting that both ligands reach the GPER-binding site in a similar way, as was demonstrated through in silico studies.

CONCLUSION

A concentration-dependent inhibition of cell proliferation occurred with compound 2 in the two cell lines regardless of GPER.

Expression and Role of the G Protein-Coupled Estrogen Receptor (GPR30/GPER) in the Development and Immune Response in Female Reproductive Cancers

Cancer is a major public health issue and represents the second leading cause of death in women worldwide, as female reproductive-related neoplasms are the main cause of incidence and mortality. Female reproductive cancers have a close relationship to estrogens, the principal female sex steroid hormones. Estrogens exert their actions by the nuclear estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ). ERα, and ERβ act as transcription factors mediating genomic effects. Besides, the G protein-coupled estrogen receptor (GPER, formerly known as GPR30) was recently described as a seven-transmembrane receptor that mediates non-genomic estrogenic signaling, including calcium mobilization, cAMP synthesis, cleavage of matrix metalloproteinases, transactivation of epidermal growth factor receptor (EGFR), and the subsequent activation of PI3K and MAPK signaling pathways, which are the reasons why it is related to cellular processes, such as cell-cycle progression, cellular proliferation, differentiation, apoptosis, migration, and invasion. Since its discovery, selective agonists and antagonists have been found and developed. GPER has been implicated in a variety of hormone-responsiveness tumors, such as breast, endometrial, ovarian, cervical, prostate, and testicular cancer as well as lung, hepatic, thyroid, colorectal, and adrenocortical cancers. Nevertheless, GPER actions in cancer are still debatable due to the conflicting information that has been reported to date, since many reports indicate that activation of this receptor can modulate carcinogenesis. In contrast, many others show that its activation inhibits tumor activity. Besides, estrogens play an essential role in the regulation of the immune system, but little information exists about the role of GPER activation on its modulation within cancer context. This review focuses on the role that the stimulation of GPER plays in female reproductive neoplasms, specifically breast, endometrial, ovarian, and cervical cancers, in its tumor activity and immune response regulation.

Upregulation of G Protein-Coupled Estrogen Receptor by Chrysin-Nanoparticles Inhibits Tumor Proliferation and Metastasis in Triple Negative Breast Cancer Xenograft Model

Triple-negative breast cancer (TNBC) is associated with a high mortality rate among women globally. TNBC shows a high rate of recurrence and distant metastasis. Particularly, the chemotherapy is limited because hormone therapy of breast cancer is ineffective. Thus, an effective chemotherapeutic agent is needed for tumor suppression. Chrysin-nanoparticles (chrysin-NPs) were investigated for their inhibitory effect on a MDA-MB-231-derived xenograft model. To gain insight into the underlying mechanisms, we conducted human matrix metalloproteinase (MMP) array, western blot, and immunohistochemistry analysis. Furthermore, in vivo imaging was used to monitor the chemotherapeutic efficacy of chrysin-NPs in a metastasis mouse model. Chrysin-NPs significantly inhibited the proliferation of MDA-MB-231 cells via the PI3K/JNK pathway and induced cell death through the p53-apoptosis pathway, leading to delayed MDA-MB-231-derived tumor growth. Interestingly, chrysin-NPs significantly induced G protein-coupled estrogen receptor (GPER) expression, which suppresses MMPs and NF-κB expression. Chrysin-NPs acted as effective metastasis inhibitors. Our results suggest that chrysin-NPs may be used as an effective adjuvant formulation to inhibit TNBC progression.

Does GPER Really Function as a G Protein-Coupled Estrogen Receptor in vivo?

Estrogen can elicit pleiotropic cellular responses via a diversity of estrogen receptors (ERs)-mediated genomic and rapid non-genomic mechanisms. Unlike the genomic responses, where the classical nuclear ERα and ERβ act as transcriptional factors following estrogen binding to regulate gene transcription in estrogen target tissues, the non-genomic cellular responses to estrogen are believed to start at the plasma membrane, leading to rapid activation of second messengers-triggered cytoplasmic signal transduction cascades. The recently acknowledged ER, GPR30 or GPER, was discovered in human breast cancer cells two decades ago and subsequently in many other cells. Since its discovery, it has been claimed that estrogen, ER antagonist fulvestrant, as well as some estrogenic compounds can directly bind to GPER, and therefore initiate the non-genomic cellular responses. Various recently developed genetic tools as well as chemical ligands greatly facilitated research aimed at determining the physiological roles of GPER in different tissues. However, there is still lack of evidence that GPER plays a significant role in mediating endogenous estrogen action in vivo. This review summarizes current knowledge about GPER, including its tissue expression and cellular localization, with emphasis on the research findings elucidating its role in health and disease. Understanding the role of GPER in estrogen signaling will provide opportunities for the development of new therapeutic strategies to strengthen the benefits of estrogen while limiting the potential side effects.

GPER stabilizes F-actin cytoskeleton and activates TAZ via PLCβ-PKC and Rho/ROCK-LIMK-Cofilin pathway

Actin is a highly abundant cytoskeletal protein that is essential for all eukaryotic cells and participates in many structural and functional roles. It has long been noted that estrogen affects cellular morphology. However, recent studies observed that both estrogen and tamoxifen induce a remarkable cytoskeletal remodeling independent of ER. In addition to ER, G protein-coupled estrogen receptor 1 (GPER, also known as GPR30) also binds to estrogen with high affinity and mediates intracellular estrogenic signaling. Here, we show that activation of GPER by its specific agonist G-1 induces re-organization of F-actin cytoskeleton. We further demonstrate that GPER acts through PLCβ-PKC and Rho/ROCK-LIMK-Cofilin pathway, which are upstream regulators of F-actin cytoskeleton assembly, thereby enhancing TAZ nuclear localization and activation. Furthermore, we find that LIMK1/2 is critical for GPER activation-induced breast cancer cell migration. Together, our results suggest that GPER mediates G-1-induced cytoskeleton assembly and GPER promotes breast cancer cell migration via PLCβ-PKC and Rho/ROCK-LIMK-Cofilin pathway.

Bisphenol AF exerts estrogenic activity in MCF-7 cells through activation of Erk and PI3K/Akt signals via GPER signaling pathway

The negative health effects of bisphenol A (BPA) due to its estrogenic activity result in the increasing usage of alternative bisphenols (BPs) including bisphenol AF (BPAF). To comprehensive understand health effects of BPAF, the MCF-7 cells were used to investigate the effects of BPAF on cell proliferation, intracellular reactive oxygen species (ROS) formation, and calcium ion (Ca²⁺) level. The molecular mechanisms of cell biological responses caused by BPAF were investigated by analyzing target protein expression. The results showed that low-concentration BPAF induces significant effects on MCF-7 cells, including promoting cell proliferation and elevating intracellular ROS and Ca²⁺ levels. BPAF in low concentration significantly enhances the protein expression of estrogen receptor α (ERα), G protein-coupled receptor (GPER), c-Myc, and Cyclin D1, as well as increases phosphorylation levels of protein kinase B (Akt) and extracellular signal-regulated kinase (Erk) in MCF-7 cells. After the addition of ERα, GPER, and phosphatidylinositide 3-kinase (PI3K) inhibitors, phosphorylations of Erk and Akt were both inhibited. In addition, specific signal inhibitors significantly attenuated the effects of BPAF. Silencing of GPER also markedly decreased BPAF induced cell proliferation. The present results suggested that BPAF can activate PI3K/Akt and Erk signals via GPER, which, in turn, stimulate cellular biological effects induced by BPAF. ERα also plays a critical role in BPAF induced cellular biological effects.

GPER modulators: Opportunity Nox on the heels of a class Akt

The (patho)physiology of estrogen and its receptors is complex. It is therefore not surprising that therapeutic approaches targeting this hormone include stimulation of its activity through supplementation with either the hormone itself or natural or synthetic agonists, inhibition of its activity through the use of antagonists or inhibitors of its synthesis, and tissue-selective modulation of its activity with biased ligands. The physiology of this hormone is further complicated by the existence of at least three receptors, the classical nuclear estrogen receptors α and β (ERα and ERβ), and the 7-transmembrane G protein-coupled estrogen receptor (GPER/GPR30), with overlapping but distinct pharmacologic profiles, particularly of anti-estrogenic ligands. GPER-selective ligands, as well as GPER knockout mice, have greatly aided our understanding of the physiological roles of GPER. Such ligands have revealed that GPER activation mediates many of the rapid cellular signaling events (including Ca2+ mobilization, ERK and PI3K/Akt activation) associated with estrogen activity, as opposed to the nuclear ERs that are traditionally described to function as ligand-induced transcriptional factors. Many of the salutary effects of estrogen throughout the body are reproduced by the GPER-selective agonist G-1, which, owing to its minimal effects on reproductive tissues, can be considered a non-feminizing estrogenic compound, and thus of potential therapeutic use in both women and men. On the contrary, until recently GPER-selective antagonists had predominantly found preclinical application in cancer models where estrogen stimulates cell growth and survival. This viewpoint changed recently with the discovery that GPER is associated with aging, particularly that of the cardiovascular system, where the GPER antagonist G36 reduced hypertension and GPER deficiency prevented cardiac fibrosis and vascular dysfunction with age, through the downregulation of Nox1 and as a consequence superoxide production. Thus, similar to the classical ERs, both agonists and antagonists of GPER may be of therapeutic benefit depending on the disease or condition to be treated.

Activation of G protein coupled estrogen receptor (GPER) promotes the migration of renal cell carcinoma via the PI3K/AKT/MMP-9 signals

Renal cell carcinoma (RCC) is the third most frequent malignancy within urological oncology. However, the mechanisms responsible for RCC metastasis are still needed further illustration. Our present study revealed that a seven-transmembrane receptor G-protein coupled estrogen receptor (GPER) was highly detected in various RCC cell lines such as ACHN, OS-RC-2 and SW839. The activation of GPER by its specific agonist G-1 significantly promoted the in vitro migration and invasion of ACHN and OS-RC-2 cells. G-1 also up regulated the expression of matrix metalloproteinase-2 (MMP-2) and MMP-9. The inhibitor of MMP-9 (Cat-444278), but not MMP-2 (Sc-204092), abolished G-1 induced cell migration, which suggested that MMP-9 is the key molecule mediating G-1 induced RCC progression. Further, G-1 treatment resulted in phosphorylation of AKT and ERK in RCC cells. PI3K/AKT inhibitor (LY294002), while not ERK inhibitor (PD98059), significantly abolished G-1 induced up regulation of MMP-9 in both AHCN and OS-RC-2 cells. Generally, our data revealed that activation of GPER by its specific agonist G-1 promoted the metastasis of RCC cells through PI3K/AKT/MMP-9 signals, which might be a promising new target for drug discovery of RCC patients.

The activation of the G protein-coupled estrogen receptor (GPER) inhibits the proliferation of mouse melanoma K1735-M2 cells

The activation of the G protein-coupled estrogen receptor (GPER) by its specific agonist G-1 inhibits prostate cancer and 17β-estradiol-stimulated breast cancer cell proliferation. Tamoxifen (TAM), which also activates the GPER, decreases melanoma cell proliferation, but its action mechanism remains controversial. Here we investigated the expression and the effects of GPER activation by G-1, TAM and its key metabolite endoxifen (EDX) on melanoma cells. Mouse melanoma K1735-M2 cells expressed GPER and G-1 reduced cell biomass, and the number of viable cells, without increasing cell death. Rather, G-1 decreased cell division by blocking cell cycle progression in G2. Likewise, TAM and EDX exhibited an antiproliferative activity in melanoma cells due to decreased cell division. Both G-1 and the antiestrogens showed a trend to decrease the levels of phosphorylated ERK 1/2 after 1 h treatment, although only EDX, the most potent antiproliferative antiestrogen, induced significant effects. Importantly, the targeting of GPER with siRNA abolished the cytostatic activity of both G-1 and antiestrogens, suggesting that the antitumor actions of antiestrogens in melanoma cells involve GPER activation. Our results unveil a new target for melanoma therapy and identify GPER as a key mediator of antiestrogen antiproliferative effects, which may contribute to select the patients that benefit from an antiestrogen-containing regimen.

Baicalein, unlike 4-hydroxytamoxifen but similar to G15, suppresses 17β-estradiol-induced cell invasion, and matrix metalloproteinase-9 expression and activation in MCF-7 human breast cancer cells

Estrogen performs an important role in the growth and development of breast cancer. There are at least three major receptors, including estrogen receptor (ER)α and β, and G protein-coupled receptor 30 (GPR30), which mediate the actions of estrogen through using transcriptional and rapid non-genomic signaling pathways. Flavonoids have been considered candidates for chemopreventive agents in breast cancer. Baicalein, the primary flavonoid derived from the root of Scutellaria baicalensis Georgi, has been reported to exert an anti-estrogenic effect. In the present study, the effects of baicalein on 17β-estradiol (E2)-induced cell invasion, and matrix metalloproteinase-9 (MMP-9) expression and activation were investigated. Furthermore, its effects were compared with that of the active form of the ER modulator tamoxifen 4-hydroxytamoxifen (OHT) and the GPR30 antagonist G15 in ERα- and GPR30-positive MCF-7 breast cancer cells. The results demonstrated that OHT failed to prevent E2-induced cell invasion, upregulation and proteolytic activity of MMP-9. However, baicalein was able to significantly suppress these E2-induced effects. Furthermore, E2-stimulated invasion, and MMP-9 expression and activation were significantly attenuated following G15 treatment. In addition, baicalein significantly inhibited G-1, a specific GPR30 agonist, induced invasion, and reduced G-1 promoted expression and activity of MMP-9, consistent with effects of G15. The results of the present study suggest that baicalein is a therapeutic candidate for GPR30-positive breast cancer treatment, and besides ERα targeting the GPR30 receptor it may achieve additional therapeutic benefits in breast cancer.

Activation of G protein-coupled receptor 30 by thiodiphenol promotes proliferation of estrogen receptor α-positive breast cancer cells

Many studies have been shown that environmental estrogen bisphenol A (BPA) can activate nuclear receptor (estrogen receptor alpha, ERα) or membrane receptor (G-protein-coupled receptor, GPR30) in breast cancer cells and exerts genomic or nongenomic actions inducing cell proliferation. 4,4'-thiodiphenol (TDP) as one of BPA derivatives exhibits more potent estrogenic activity than BPA does. However, comparatively little is known about the ways in which TDP interferes with these signaling pathways and produces cell biological changes. This study evaluated the effect of TDP on cell viability, reactive oxygen species (ROS) formation, and intercellular calcium (Ca²⁺) fluctuation in MCF-7 breast cancer cells. The underlying molecular mechanism of cell proliferation induced by TDP was analyzed by examining the activation of ERα and GPR30-mediated phosphatidylinotidol 3-kinase/protein kinase B (PI3K/AKT) and extracellular-signa1regulated kinase (ERK1/2) signaling pathways. The results showed that exposure to 0.1-10 μM TDP for 24, 48, and 72 h significantly increased viability of MCF-7 cells. At the same concentration range, TDP exposure for 3 and 24 h markedly elevated ROS production and intracellular Ca²⁺ levels. In addition, 0.01-1 μM TDP significantly increased the expression of ERα, GPR30, p-AKT and p-ERK1/2 protein. Specific protein inhibitors blocked phosphorylation of ERK1/2 and AKT and decreased TDP-induced cell proliferation. These findings show that TDP activated the GPR30-PI3K/AKT and ERK1/2 pathways, and the resulting interaction with ERα stimulated MCF-7 cell proliferation. Our results indicate a novel mechanism through which TDP may exert relevant estrogenic action in ERα positive cancer cells.

Exploring estrogenic activity in lung cancer

It is well known that a connection between xenobiotics inhalation, especially tobacco combustion and Lung Cancer development is strongly significant and indisputable. However, recent studies provide evidence indicating that another factors such as, estrogens are also involved in lung carcinoma biology and metabolism. Although the status of estrogen receptors (ER), in both cancerous and healthy lung tissue has been well documented, there is still inconclusive data with respect of which isoform of the receptor is present in the lungs. However according to several studies, ERβ appears to be predominant form. Apart from ERs, estrogens can work through a recently discovered G-coupled estrogen receptor. Binding with both types of the receptors causes a signal, which leads to i.e. enhanced cell proliferation. There are many published reports which suggest that estrogen can be synthesized in situ in lung cancer. Some disturbances in the activity and expression levels of enzymes involved in estrogen synthesis were proved. This suggests that increased amounts of sex-steroid hormones can affect cells biology and be the reason of the accelerated development and pathogenesis of lung cancer. There also exist phenomena which associate estrogenic metabolism and tobacco combustion and its carcinogenic influence on the lungs. Compounds present in cigarette smoke induce the activity of CYP1B1, the enzyme responsible for estrogenic metabolism and synthesis of their cateholic derivatives. These structures during their redox cycle are able to release reactive oxygen species or form DNA adduct, which generally leads to destruction of genetic material. This process may explain the synergistic effect of smoking and estrogens on estrogen-dependent lung cancer development.

Double-edged role of G protein-coupled estrogen receptor 1 in breast cancer prognosis: an analysis of 167 breast cancer samples and online data sets

G protein-coupled estrogen receptor 1 (GPER1) is widely expressed in breast cancer; however, its prognostic significance in breast cancer patients remains controversial. In this study, expression levels of GPER1 were analyzed by using real-time polymerase chain reaction in 167 primary breast cancer samples, and overall survival (OS), recurrence-free survival (RFS), distant metastasis-free survival (DMFS), and disease-free survival (DFS) were analyzed by using Kaplan-Meier curves and multivariable Cox regression. In addition, a meta-analysis was conducted with all available online data sets found in the Web sites kmplot.com and www.prognoscan.org. The results showed that there was no significant correlation between GPER1 expression and OS, RFS, DMFS, and DFS in the total breast cancer patient population. In contrast, the meta-analysis of online data sets found that expression levels of GPER1 were slightly associated with better RFS in the total breast cancer population (P=0.021). Interestingly, higher expression of GPER1 was associated with poorer DFS in HER2-positive subtype of breast cancer (P=0.047) but with better DMFS (P=0.040) and DFS (P=0.035) in HER2-negative subtype of breast cancer. In addition, it was found that HER2 overexpression in MDA-MB-231 cell increased GPER1, which may help explain protumor effect of GPER1 in HER2-overexpressed patients. The overall results suggested that the expression of GPER1 has distinct prognostic values in HER2-positive and HER2-negative breast cancer patients.

Imbalance between proliferation and apoptosis-related impaired GPR30 expression is involved in preeclampsia

The proliferation and apoptosis of cells in the placenta play a critical role in preeclampsia (PE) in which estrogen has been implicated via estrogen receptors (ERs). A novel ER, G-protein-coupled receptor 30 (GPR30), has recently been shown to be involved in PE. We investigated the basic levels of proliferation and apoptosis in normal placentae and placentae with PE and compared GPR30 expression levels between the two groups. We demonstrated that low GPR30 expression levels, more apoptosis, and less proliferation were associated with PE. Moreover, our in vitro study showed that both the selective GPR30 agonist G1 and the general ER agonist 17-β-estradiol were able to protect the placenta from hypoxia-reoxygenation injuries, resulting in decreased apoptosis and increased proliferation. Furthermore, this protective effect was abolished by the addition of the selective GPR30 inhibitor G15. These results provide evidence that (1) GPR30 is involved in regulating cell proliferation and apoptosis; (2) pharmacologic upregulation of GPR30 is beneficial for PE management; (3) GPR30 may therefore be an interventional target for pregnancies complicated by PE.

The G protein-coupled estrogen receptor as a modulator of neoplastic transformation

Estrogens play a crucial role in the regulation of physiological and pathophysiological processes. These hormones act through specific receptors, most notably the canonical estrogen receptors α and β (ERα and ERβ) and their truncated forms as well as the G protein-coupled estrogen receptor (GPER). Several studies have shown that GPER is expressed in many normal and cancer cells, including those of the breast, endometrium, ovary, testis and lung. Hormonal imbalance is one possible cause of cancer development. An accumulating body of evidence indicates that GPER is involved in the regulation of cancer cell proliferation, migration and invasion, it may act as a mediator of microRNA, and is believed to modulate the inflammation associated with neoplastic transformation. Furthermore, used in various treatment regimens anti-estrogens such as tamoxifen, raloxifen and fulvestrant (ICI 182.780), antagonists/modulators of canonical estrogen receptors, were found to be GPER agonists. This review presents the current knowledge about the potential role of GPER in neoplastic transformation.

The cardiac electrogenic sodium/bicarbonate cotransporter (NBCe1) is activated by aldosterone through the G protein-coupled receptor 30 (GPR 30)

The sodium/bicarbonate cotransporter (NBC) transports extracellular Na⁺ and HCO₃^- into the cytoplasm upon intracellular acidosis, restoring the acidic pH_i to near neutral values. Two different NBC isoforms have been described in the heart, the electroneutral NBCn1 (1Na⁺:1HCO₃^-) and the electrogenic NBCe1 (1Na⁺:2HCO₃^-). Certain non-genomic effects of aldosterone (Ald) were due to an orphan G protein-couple receptor 30 (GPR30). We have recently demonstrated that Ald activates GPR30 in adult rat ventricular myocytes, which transactivates the epidermal growth factor receptor (EGFR) and in turn triggers a reactive oxygen species (ROS)- and PI3K/AKT-dependent pathway, leading to the stimulation of NBC. The aim of this study was to investigate the NBC isoform involved in the Ald/GPR30-induced NBC activation. Using specific NBCe1 inhibitory antibodies (a-L3) we demonstrated that Ald does not affect NBCn1 activity. Ald was able to increase NBCe1 activity recorded in isolation. Using immunofluorescence and confocal microscopy analysis we showed in this work that both NBCe1 and GPR30 are localized in t-tubules. In conclusion, we have demonstrated that NBCe1 is the NBC isoform activated by Ald in the heart.

Morphological and ultrasound characteristics of endometrium in patients with breast cancer and the risk of secondary tumors

The analysis of features of endometrial hyperplasia in patients with breast cancer (BC) receiving adjuvant tamoxifen therapy in the period from 2011 to 2014 inclusive. 196 patients with breast cancer with ultrasound criteria of endometrial hyperplasia were examined. A postoperative histopathologic examination revealed that the lesions were endometrial hyperplasias and with 4,1% malignant findings. Hyperplasia, polyps and endometrial cancer were diagnosed in patients receiving tamoxifen, which allowed a comparison clinicoanamnestic, ultrasound, morphological and genetic characteristics of the endometrium to recover a high risk of developing a second cancer, as well as offer a pathogenic variant of its prevention. The article can be interesting as for obstetrician-gynecologist, watching women after breast cancer treatment, and oncologists, choosing a drug for adjuvant therapy.

Hydroxychloroquine inhibits autophagy to potentiate antiestrogen responsiveness in ER+ breast cancer

PURPOSE

Estrogen receptor-α (ERα)-targeted therapies including tamoxifen (TAM) or Faslodex (ICI) are used to treat ER(+) breast cancers. Up to 50% of tumors will acquire resistance to these interventions. Autophagy has been implicated as a major driver of antiestrogen resistance. We have explored the ability of hydroxychloroquine (HCQ), which inhibits autophagy, to affect antiestrogen responsiveness.

EXPERIMENTAL DESIGN

TAM-resistant MCF7-RR and ICI-resistant/TAM cross-resistant LCC9 ER(+) breast cancer cells were injected into mammary fat pads of female athymic mice and treated with TAM and/or ICI in combination with oral low-dose HCQ.

RESULTS

We show that HCQ can increase antiestrogen responsiveness in MCF7-RR and LCC9 cells and tumors, likely through the inhibition of autophagy. However, the combination of ICI+HCQ was less effective than HCQ alone in vivo, unlike the TAM+HCQ combination. Antiestrogen treatment stimulated angiogenesis in tumors but did not prevent HCQ effectiveness. The lower efficacy of ICI+HCQ was associated with ICI effects on cell-mediated immunity within the tumor microenvironment. The mouse chemokine KC (CXCL1) and IFNγ were differentially regulated by both TAM and ICI treatments, suggesting a possible effect on macrophage development/activity. Consistent with these observations, TAM+HCQ treatment increased tumor CD68(+) cells infiltration, whereas ICI and ICI+HCQ reduced peripheral tumor macrophage content. Moreover, macrophage elimination of breast cancer target cells in vitro was reduced following exposure to ICI.

CONCLUSION

HCQ restores antiestrogen sensitivity to resistant tumors. Moreover, the beneficial combination of TAM+HCQ suggests a positive outcome for ongoing neoadjuvant clinical trials using this combination for the treatment of ER(+) ductal carcinoma in situ lesions.

The Selective Estrogen Receptor Modulator Raloxifene Regulates Arginine-Vasopressin Gene Expression in Human Female Neuroblastoma Cells Through G Protein-Coupled Estrogen Receptor and ERK Signaling

The selective estrogen receptor modulator raloxifene reduces blood pressure in hypertensive postmenopausal women. In the present study we have explored whether raloxifene regulates gene expression of arginine vasopressin (AVP), which is involved in the pathogenesis of hypertension. The effect of raloxifene was assessed in human female SH-SY5Y neuroblastoma cells, which have been recently identified as a suitable cellular model to study the estrogenic regulation of AVP. Raloxifene, within a concentration ranging from 10(-10) M to 10(-6) M, decreased the mRNA levels of AVP in SH-SY5Y cells with maximal effect at 10(-7) M. This effect of raloxifene was imitated by an agonist (±)-1-[(3aR*,4S*,9bS*)-4-(6-bromo-1,3-benzodioxol-5-yl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinolin-8-yl]-ethanone of G protein-coupled estrogen receptor-1 (GPER) and blocked by an antagonist (3aS*,4R*,9bR*)-4-(6-bromo-1,3-benzodioxol-5-yl)-3a,4,5,9b-3H-cyclopenta[c]quinoline of GPER and by GPER silencing. Raloxifene induced a time-dependent increase in the level of phosphorylated ERK1 and ERK2, by a mechanism blocked by the GPER antagonist. The treatment of SH-SY5Y cells with either a MAPK/ERK kinase 1/2-specific inhibitor (1,4-diamino-2, 3-dicyano-1,4-bis(2-aminophenylthio)butadine) or a protein kinase C inhibitor (sotrastaurin) blocked the effects of raloxifene on the phosphorylation of ERK1/2 and the regulation of AVP mRNA levels. These results reveal a mechanism mediating the regulation of AVP expression by raloxifene, involving the activation of GPER, which in turn activates protein kinase C, MAPK/ERK kinase, and ERK. The regulation of AVP by raloxifene and GPER may have implications for the treatment of blood hypertension(.).

The co-expression of GPER and Gankyrin in ovarian endometriosis and its correlation with the rASRM stages

OBJECTIVE

The aim of this study was to examine the expression of G protein-coupled estrogen receptor (GPER) and Gankyrin in ovarian endometriosis, analyze their clinicopathological significance, and investigate their correlation.

METHODS

Quantitative real-time polymerase chain reaction and Western blot were performed to testify mRNA and protein expression of GPER and Gankyrin in ovarian endometriosis. Immunohistochemical staining (streptavidin-peroxidase method) was conducted to determine the expression and distribution of GPER and Gankyrin protein in matched ectopic and eutopic endometrium of endometriosis and normal endometrium. We also investigated their associations with rASRM stages and the correlation between the two proteins.

RESULTS

GPER and Gankyrin were found overexpressed in ectopic endometrium of endometriosis compared with either its eutopic counterpart or endometrium from normal patients. The immunohistochemical analysis also revealed that higher expression was observed in eutopic endometrium with or without endometriosis during proliferative phase in comparison to secretory phase. These two proteins were positively correlated with the stages of endometriosis. Moreover, a significant positive correlation was found between GPER and Gankyrin both in ectopic and eutopic endometrium of the ovarian endometriosis.

CONCLUSION

GPER and Gankyrin might be implicated in the hormonal regulation of endometriosis and be associated with the severity of endometriosis. In addition, GPER and Gankyrin were found to be positively correlated, which could possibly serve as novel therapeutic targets for this disease.

Rethinking tamoxifen in the management of melanoma: New answers for an old question

The use of the antiestrogen tamoxifen in melanoma therapy is controversial due to the unsuccessful outcomes and a still rather unclarified mechanism of action. It seemed that the days of tamoxifen in malignant melanoma therapy were close to an end, but new evidence may challenge this fate. On one hand, it is now believed that metabolism is a major determinant of tamoxifen clinical outcomes in breast cancer patients, which is a variable that has yet to be tested in melanoma patients, since the tamoxifen active metabolite endoxifen demonstrated superior cytostatic activity over the parent drug in melanoma cells; on the other hand, new evidence has emerged regarding estrogen-mediated signaling in melanoma cells, including the methylation of the estrogen receptor-α gene promoter and the expression of the G protein coupled estrogen receptor. The expression of estrogen receptor-α and G protein coupled estrogen receptor, as well as the cytochrome P450 (CYP) 2D6 genotype, may be used as predictive biomarkers to select the patients that may respond to antiestrogens based on specific traits of their tumors. This review focused on these new evidences and how they may contribute to shed new light on this long-lasting controversy, as well as their possible implications for future investigations.

G protein-coupled estrogen receptor (GPER) mediates NSCLC progression induced by 17β-estradiol (E2) and selective agonist G1

Estrogen classically drives lung cancer development via estrogen receptor β (ERβ). However, fulvestrant, an anti-estrogen-based endocrine therapeutic treatment, shows limited effects for non-small cell lung cancer (NSCLC) in phase II clinical trials. G protein-coupled estrogen receptor (GPER), a third estrogen receptor that binds to estrogen, has been found to be activated by fulvestrant, stimulating the progression of breast, endometrial, and ovarian cancers. We here demonstrated that cytoplasm-GPER (cGPER) (80.49 %) and nucleus-GPER (53.05 %) were detected by immunohistochemical analysis in NSCLC samples. cGPER expression was related to stages IIIA-IV, lymph node metastasis, and poorly differentiated NSCLC. Selective agonist G1 and 17β-estradiol (E2) promoted the GPER-mediated proliferation, invasion, and migration of NSCLC cells. Additionally, in vitro administration of E2 and G1 increased the number of tumor nodules, tumor grade, and tumor index in a urethane-induced adenocarcinoma model. Importantly, the pro-tumorigenic effects of GPER induced by E2 were significantly reduced by co-administering the GPER inhibitor G15 and the ERβ inhibitor fulvestrant, as compared to administering fulvestrant alone both in vitro and in vivo. Moreover, the phosphorylation of MAPK and Akt was involved in E2/G1-induced GPER activation. In conclusion, our results indicated that a pro-tumor function of GPER exists that mediated E2-/G1-dependent NSCLC progression and showed better efficiency regarding the co-targeting of GPER and ERβ, providing a rationale for further investigation of anti-estrogen clinical therapy.

The endometrial cancer cell lines Ishikawa and HEC-1A, and the control cell line HIEEC, differ in expression of estrogen biosynthetic and metabolic genes, and in androstenedione and estrone-sulfate metabolism

Estrogens have important roles in the pathogenesis of endometrial cancer. They can have carcinogenic effects through stimulation of cell proliferation or formation of DNA-damaging species. To characterize model cell lines of endometrial cancer, we determined the expression profiles of the estrogen receptors (ERs) ESR1, ESR2 and GPER, and 23 estrogen biosynthetic and metabolic genes, and investigated estrogen biosynthesis in the control HIEEC cell line and the Ishikawa and HEC-1A EC cell lines. HIEEC and Ishikawa expressed all ERs to different extents, while HEC-1A cells lacked expression of ESR1. Considering the estrogen biosynthetic and metabolic enzymes, these cells showed statistically significant different gene expression profiles for SULT2B1, HSD3B2, CYP19A1, AKR1C3, HSD17B1, HSD17B7, HSD17B12, CYP1B1, CYP3A5, COMT, SULT1A1, GSTP1 and NQO2. In these cells, E2 was formed from E1S and E1, while androstenedione was not converted to estrogens. HIEEC and Ishikawa had similar profiles of androstenedione and E1 metabolism, but hydrolysis of E1S to E1 was weaker in Ishikawa cells. HEC-1A cells were less efficient for activation of E1 into the potent E2, but metabolized androstenedione to other androgenic metabolites better than HIEEC and Ishikawa cells. This study reveals that HIEEC, Ishikawa, and HEC-1A cells can all form estrogens only via the sulfatase pathway. HIEEC, Ishikawa, and HEC-1A cells expressed all the major genes in the production of hydroxyestrogens and estrogen quinones, and in their conjugation. Significantly higher CYP1B1 mRNA levels in Ishikawa cells compared to HEC-1A cells, together with lack of UGT2B7 expression, indicate that Ishikawa cells can accumulate more toxic estrogen-3,4-quinones than HEC-1A cells, as also for HIEEC cells. This study provides further characterization of HIEEC, Ishikawa, and HEC-1A cells, and shows that they differ greatly in expression of the genes investigated and in their capacity for E2 formation, and thus they represent different in vitro models.

The activation of G protein-coupled receptor 30 (GPR30) inhibits proliferation of estrogen receptor-negative breast cancer cells in vitro and in vivo

There is an urgent clinical need for safe and effective treatment agents and therapy targets for estrogen receptor negative (ER−) breast cancer. G protein-coupled receptor 30 (GPR30), which mediates non-genomic signaling of estrogen to regulate cell growth, is highly expressed in ER− breast cancer cells. We here showed that activation of GPR30 by the receptor-specific agonist G-1 inhibited the growth of ER− breast cancer cells in vitro. Treatment of ER− breast cancer cells with G-1 resulted in G2/M-phase arrest, downregulation of G2-checkpoint regulator cyclin B, and induction of mitochondrial-related apoptosis. The G-1 treatment increased expression of p53 and its phosphorylation levels at Serine 15, promoted its nuclear translocation, and inhibited its ubiquitylation, which mediated the growth arrest effects on cell proliferation. Further, the G-1 induced sustained activation and nuclear translocation of ERK1/2, which was mediated by GPR30/epidermal growth factor receptor (EGFR) signals, also mediated its inhibition effects of G-1. With extensive use of siRNA-knockdown experiments and inhibitors, we found that upregulation of p21 by the cross-talk of GPR30/EGFR and p53 was also involved in G-1-induced cell growth arrest. In vivo experiments showed that G-1 treatment significantly suppressed the growth of SkBr3 xenograft tumors and increased the survival rate, associated with proliferation suppression and upregulation of p53, p21 while downregulation of cyclin B. The discovery of multiple signal pathways mediated the suppression effects of G-1 makes it a promising candidate drug and lays the foundation for future development of GPR30-based therapies for ER− breast cancer treatment.

GPER-targeted, 99mTc-labeled, nonsteroidal ligands demonstrate selective tumor imaging and in vivo estrogen binding

Our understanding of estrogen (17β-estradiol, E2) receptor biology has evolved in recent years with the discovery and characterization of a 7-transmembrane-spanning G protein-coupled estrogen receptor (GPER/GPR30) and the development of GPER-selective functional chemical probes. GPER is highly expressed in certain breast, endometrial, and ovarian cancers, establishing the importance of noninvasive methods to evaluate GPER expression in vivo. Here, we developed (99m)Tc-labeled GPER ligands to demonstrate the in vivo status of GPER as an estrogen receptor (ER) and for GPER visualization in whole animals. A series of (99m)Tc(I)-labeled nonsteroidal tetrahydro-3H-cyclopenta[c]quinolone derivatives was synthesized utilizing pyridin-2-yl hydrazine and picolylamine chelates. Radioligand receptor binding studies revealed binding affinities in the 10 to 30 nmol/L range. Cell signaling assays previously demonstrated that derivatives retaining a ketone functionality displayed agonist properties, whereas those lacking such a hydrogen bond acceptor were antagonists. In vivo biodistribution and imaging studies performed on mice bearing human endometrial and breast cancer cell xenografts yielded significant tumor uptake (0.4-1.1%ID/g). Blocking studies revealed specific uptake in multiple organs (adrenals, uterus, and mammary tissue), as well as tumor uptake with similar levels of competition by E2 and G-1, a GPER-selective agonist. In conclusion, we synthesized and evaluated a series of first-generation (99m)Tc-labeled GPER-specific radioligands, demonstrating GPER as an estrogen-binding receptor for the first time in vivo using competitive binding principles, and establishing the utility of such ligands as tumor imaging agents. These results warrant further investigation into the role of GPER in estrogen-mediated carcinogenesis and as a target for diagnostic/therapeutic/image-guided drug delivery.

IMPLICATIONS

These studies provide a molecular basis to evaluate GPER expression and function as an ER through in vivo imaging.

Structural elucidation of new urinary tamoxifen metabolites by liquid chromatography quadrupole time-of-flight mass spectrometry

In this study, tamoxifen metabolic profiles were investigated carefully. Tamoxifen was administered to two healthy male volunteers and one female patient suffering from breast cancer. Urinary extracts were analyzed by liquid chromatography quadruple time-of-flight mass spectrometry using full scan and targeted MS/MS techniques with accurate mass measurement. Chromatographic peaks for potential metabolites were selected by using the theoretical [M + H](+) as precursor ion in full-scan experiment and m/z 72, 58 or 44 as characteristic product ions for N,N-dimethyl, N-desmethyl and N,N-didesmethyl metabolites in targeted MS/MS experiment, respectively. Tamoxifen and 37 metabolites were detected in extraction study samples. Chemical structures of seven unreported metabolites were elucidated particularly on the basis of fragmentation patterns observed for these metabolites. Several metabolic pathways containing mono- and di-hydroxylation, methoxylation, N-desmethylation, N,N-didesmethylation, oxidation and combinations were suggested. All the metabolites were detected in the urine samples up to 1 week.

Icariin and icaritin stimulate the proliferation of SKBr3 cells through the GPER1-mediated modulation of the EGFR-MAPK signaling pathway

Icariin (ICA) and icaritin (ICT), with a similar structure to genistein, are the important bioactive components of the genus Epimedium, and regulate many cellular processes. In the present study, using the estrogen receptor (ER)-negative breast cancer cell line, SKBr3, as a model, we examined the hypothesis that ICA and ICT at low concentrations stimulate SKBr3 cell proliferation in vitro through the functional membrane, G protein‑coupled estrogen receptor 1 (GPER1), mediated by the epithelial growth factor receptor (EGFR)‑mitogen-activated protein kinase (MAPK) signaling pathway. MTT assay revealed that ICA and ICT at doses of 1 nM to 1 µM markedly stimulated SKBr3 cell proliferation in a dose-dependent manner. The ICA- and ICT-stimulated cell growth was completely suppressed by the GPER1 antagonist, G-15, indicating that the ICA‑ and ICT-stimulated cell proliferation was mediated by GPER1 activation. Semi-quantitative RT-PCR analysis revealed that treatment with ICA and ICT enhanced the transcription of c-fos, a proliferation-related early gene. The ICA- and ICT-stimulated mRNA expression was markedly attenuated by G-15, AG-1478 (an EGFR antagonist) or PD98059 (a MAPK inhibitor). Our data also demonstrated that ICA and ICT increased the phosphorylation of ERK1/2. The ICA- and ICT-stimulated ERK1/2 phosphorylation was blocked by pre-treatment of the cells with G-15 and AG-1478 or PD 98059. Flow cytometric analysis confirmed that the ICA- and ICT-stimulated SKBr3 cell proliferation involved the GPER1-mediated modulation of the EGFR‑MAPK signaling pathway. To the best of our knowledge, our current findings demonstrate for the first time that ICA and ICT promote the progression of ER-negative breast cancer through the activation of membrane GPER1.

GPER functions as a tumor suppressor in MCF-7 and SK-BR-3 breast cancer cells

PURPOSE

The orphan, membrane-bound estrogen receptor (GPER) is expressed at high levels in a large fraction of breast cancer patients, and its expression is favorable for patients' survival. We investigated the role of GPER as a potential tumor suppressor in MCF-7 and SK-BR-3 breast cancer cells.

METHODS

The effect of GPER agonist G-1 in cell culture was used to determine whether GPER inhibit cell growth. The methylation status of GPER promoter was investigated by methylation-specific PCR.

RESULTS

GPER-specific agonist G-1 inhibited breast cancer cell proliferation in concentration-dependent manner via induction of the cell cycle arrest in M-phase, enhanced phosphorylation of histone 3 and cell apoptosis. Analysis of the methylation status of the GPER promoter in MCF-7 and SK-BR-3 cells revealed that GPER expression is regulated by epigenetic mechanisms and GPER expression is inactivated by promoter methylation. Overall, our results are consistent with our recent findings in triple-negative breast cancer cells, and the cell surface expression of GPER makes it an excellent potential therapeutic target for non-triple-negative breast cancer.

Estrogen and pure antiestrogen fulvestrant (ICI 182 780) augment cell-matrigel adhesion of MCF-7 breast cancer cells through a novel G protein coupled estrogen receptor (GPR30)-to-calpain signaling axis

Fulvestrant (ICI 182 780, ICI) has been used in treating patients with hormone-sensitive breast cancer, yet initial or acquired resistance to endocrine therapies frequently arises and, in particular, cancer recurs as metastasis. We demonstrate here that both 17-beta-estradiol (E2) and ICI enhance cell adhesion to matrigel in MCF-7 breast cancer cells, with increased autolysis of calpain 1 (large subunit) and proteolysis of focal adhesion kinase (FAK), indicating calpain activation. Additionally, either E2 or ICI induced down-regulation of estrogen receptor α without affecting G protein coupled estrogen receptor 30 (GPR30) expression. Interestingly, GPR30 agonist G1 triggered calpain 1 autolysis but not calpain 2, whereas ER agonist diethylstilbestrol caused no apparent calpain autolysis. Furthermore, the actions of E2 and ICI on calpain and cell adhesion were tremendously suppressed by G15, or knockdown of GPR30. E2 and ICI also induced phosphorylation of extracellular regulated protein kinases 1 and 2 (ERK1/2), and suppression of ERK1/2 phosphorylation by U0126 profoundly impeded calpain activation triggered by estrogenic and antiestrogenic stimulations indicating implication of ERK1/2 in the GPR30-mediated action. Lastly, the E2- or ICI-induced cell adhesion was dramatically impaired by calpain-specific inhibitors, ALLN or calpeptin, suggesting requirement of calpain in the GPR30-associated action. These data show that enhanced cell adhesion by E2 and ICI occurs via a novel GPR30-ERK1/2-calpain pathway. Our results indicate that targeting the GPR30 signaling may be a potential strategy to reduce metastasis and improve the efficacy of antiestrogens in treatment of advanced breast cancer.

The G protein-coupled estrogen receptor (GPER) is expressed in two different subcellular localizations reflecting distinct tumor properties in breast cancer

INTRODUCTION

The G protein-coupled estrogen receptor (GPER) is a novel estrogen receptor that mediates proliferative effects induced by estrogen but also by tamoxifen. The aim of our study was to analyze the frequency of GPER in a large collective of primary invasive breast carcinomas, with special emphasis on the subcellular expression and to evaluate the association with clinicopathological parameters and patient overall survival.

METHODS

The tissue microarrays from formalin-fixed, paraffin embedded samples of primary invasive breast carcinomas (n = 981) were analyzed for GPER expression using immunohistochemistry. Expression data were compared to the clinicopathological parameters and overall survival. GPER localization was also analyzed in two immortalized breast cancer cell lines T47D and MCF7 by confocal immunofluorescence microscopy.

RESULTS

A predominantly cytoplasmic GPER expression was found in 189 carcinomas (19.3%), whereas a predominantly nuclear expression was observed in 529 cases (53.9%). A simultaneous comparable positive expression of both patterns was found in 32 of 981 cases (3.2%), and negative staining was detected in 295 cases (30%). Confocal microscopy confirmed the occurrence of cytoplasmic and nuclear GPER expression in T47D and MCF7. Cytoplasmic GPER expression was significantly associated with non-ductal histologic subtypes, low tumor stage, better histologic differentiation, as well as Luminal A and B subtypes. In contrast, nuclear GPER expression was significantly associated with poorly differentiated carcinomas and the triple-negative subtype. In univariate analysis, cytoplasmic GPER expression was associated with better overall survival (p = 0.012).

CONCLUSION

Our data suggest that predominantly cytoplasmic and/or nuclear GPER expression are two distinct immunohistochemical patterns in breast carcinomas and may reflect different biological features, reason why these patterns should be clearly distinguished in histological evaluations. Prospective studies will be needed to assess whether the expression status of GPER in breast carcinomas should be routinely observed by clinicians, for instance, before implementing endocrine breast cancer treatment.