A role for G-protein coupled estrogen receptor (GPER) in estrogen-induced carcinogenesis: Dysregulated glandular homeostasis, survival and metastasis

Advances in immune regulation of the G protein-coupled estrogen receptor

Estrogen and related receptors have been shown to have a significant impact on human development, reproduction, metabolism and immune regulation and to play a critical role in tumor development and treatment. Traditionally, the nuclear estrogen receptors (nERs) ERα and ERβ have been thought to be involved in mediating the estrogenic effects. However, our group and others have previously demonstrated that the G protein-coupled estrogen receptor (GPER) is the third independent ER, and estrogen signaling mediated by GPER is known to play an important role in normal physiology and a variety of abnormal diseases. Interestingly, recent studies have progressively revealed GPER involvement in the maintenance of the normal immune system, abnormal immune diseases, and inflammatory lesions, which may be of significant clinical value primarily in the immunotherapy of tumors. In this article, we review current advances in GPER-related immunomodulators and provide a theoretical basis and potential clinical targets to ameliorate immune-related diseases and immunotherapy for tumors.

The G Protein Estrogen Receptor (GPER) is involved in the resistance to the CDK4/6 inhibitor palbociclib in breast cancer

BACKGROUND

The cyclin D1-cyclin dependent kinases (CDK)4/6 inhibitor palbociclib in combination with endocrine therapy shows remarkable efficacy in the management of estrogen receptor (ER)-positive and HER2-negative advanced breast cancer (BC). Nevertheless, resistance to palbociclib frequently arises, highlighting the need to identify new targets toward more comprehensive therapeutic strategies in BC patients.

METHODS

BC cell lines resistant to palbociclib were generated and used as a model system. Gene silencing techniques and overexpression experiments, real-time PCR, immunoblotting and chromatin immunoprecipitation studies as well as cell viability, colony and 3D spheroid formation assays served to evaluate the involvement of the G protein-coupled estrogen receptor (GPER) in the resistance to palbociclib in BC cells. Molecular docking simulations were also performed to investigate the potential interaction of palbociclib with GPER. Furthermore, BC cells co-cultured with cancer-associated fibroblasts (CAFs) isolated from mammary carcinoma, were used to investigate whether GPER signaling may contribute to functional cell interactions within the tumor microenvironment toward palbociclib resistance. Finally, by bioinformatics analyses and k-means clustering on clinical and expression data of large cohorts of BC patients, the clinical significance of novel mediators of palbociclib resistance was explored.

RESULTS

Dissecting the molecular events that characterize ER-positive BC cells resistant to palbociclib, the down-regulation of ERα along with the up-regulation of GPER were found. To evaluate the molecular events involved in the up-regulation of GPER, we determined that the epidermal growth factor receptor (EGFR) interacts with the promoter region of GPER and stimulates its expression toward BC cells resistance to palbociclib treatment. Adding further cues to these data, we ascertained that palbociclib does induce pro-inflammatory transcriptional events via GPER signaling in CAFs. Of note, by performing co-culture assays we demonstrated that GPER contributes to the reduced sensitivity to palbociclib also facilitating the functional interaction between BC cells and main components of the tumor microenvironment named CAFs.

CONCLUSIONS

Overall, our results provide novel insights on the molecular events through which GPER may contribute to palbociclib resistance in BC cells. Additional investigations are warranted in order to assess whether targeting the GPER-mediated interactions between BC cells and CAFs may be useful in more comprehensive therapeutic approaches of BC resistant to palbociclib.

Appraising the causal association between Crohn's disease and breast cancer: a Mendelian randomization study

Background

Previous research has indicated that there may be a link between Crohn's disease (CD) and breast cancer (BC), but the causality remains unclear. This study aimed to investigate the causal association between CD and BC using Mendelian randomization (MR) analysis.

Methods

The summary data for CD (5,956 cases/14,927 controls) was obtained from the International Inflammatory Bowel Disease Genetics Consortium (IIBDGC). And the summary data for BC (122,977 cases/105,974 controls) was extracted from the Breast Cancer Association Consortium (BCAC). Based on the estrogen receptor status, the cases were classified into two subtypes: estrogen receptor-positive (ER+) BC and estrogen receptor-negative (ER-) BC. We used the inverse variance weighted method as the primary approach for two-sample MR. MR-PRESSO method was used to rule out outliers. Heterogeneity and pleiotropy tests were carried out to improve the accuracy of results. Additionally, multivariable MR was conducted by adjusting for possible confounders to ensure the stability of the results.

Results

The two-sample MR indicated that CD increased the risks of overall (OR: 1.020; 95% CI: 1.010-1.031; p=0.000106), ER+ (OR: 1.019; 95%CI: 1.006-1.034; p=0.006) and ER- BC (OR: 1.019; 95%CI: 1.000-1.037; p=0.046) after removal of outliers by MR-PRESSO. This result was reliable in the sensitivity analysis, including Cochran's Q and MR-Egger regression. In multivariate MR analyses, after adjusting for smoking and drinking separately or concurrently, the positive association between CD and the risks of overall and ER+ BC remained, but it disappeared in ER- BC. Furthermore, reverse MR analysis suggested that BC did not have a significant impact on CD risk.

Conclusion

Our findings provide evidence for a possible positive association between CD and the risk of BC. However, further studies are needed to fully understand the underlying mechanisms and establish a stronger causal relationship.

Interplay between Estrogen, Kynurenine, and AHR Pathways: An immunosuppressive axis with therapeutic potential for breast cancer treatment

Breast cancer is one of the most common malignancies among women worldwide. Estrogen exposure via endogenous and exogenous sources during a lifetime, together with environmental exposure to estrogenic compounds, represent the most significant risk factor for breast cancer development. As breast tumors establish, multiple pathways are deregulated. Among them is the aryl hydrocarbon receptor (AHR) signaling pathway. AHR, a ligand-activated transcription factor associated with the metabolism of polycyclic aromatic hydrocarbons and estrogens, is overexpressed in breast cancer. Furthermore, AHR and estrogen receptor (ER) cross-talk pathways have been observed. Additionally, the Tryptophan (Trp) catabolizing enzymes indolamine-2,3-dioxygenase (IDO) and tryptophan-2,3-dioxygenase (TDO) are overexpressed in breast cancer. IDO/TDO catalyzes the formation of Kynurenine (KYN) and other tryptophan-derived metabolites, which are ligands of AHR. Once KYN activates AHR, it stimulates the expression of the IDO enzyme, increases the level of KYN, and activates non-canonical pathways to control inflammation and immunosuppression in breast tumors. The interplay between E2, AHR, and IDO/TDO/KYN pathways and their impact on the immune system represents an immunosuppressive axis on breast cancer. The potential modulation of the immunosuppressive E2-AHR-IDO/TDO/KYN axis has aroused great expectations in oncotherapy. The present article will review the mechanisms implicated in generating the immunosuppressive axis E2-AHR-IDO/TDO/KYN in breast cancer and the current state of knowledge as a potential therapeutic target.

The G Protein-Coupled Estrogen Receptor (GPER): A Critical Therapeutic Target for Cancer

Estrogens have been implicated in the pathogenesis of various cancers, with increasing concern regarding the overall rising incidence of disease and exposure to environmental estrogens. Estrogens, both endogenous and environmental, manifest their actions through intracellular and plasma membrane receptors, named ERα, ERβ, and GPER. Collectively, they act to promote a broad transcriptional response that is mediated through multiple regulatory enhancers, including estrogen response elements (EREs), serum response elements (SREs), and cyclic AMP response elements (CREs). Yet, the design and rational assignment of antiestrogen therapy for breast cancer has strictly relied upon an endogenous estrogen-ER binary rubric that does not account for environmental estrogens or GPER. New endocrine therapies have focused on the development of drugs that degrade ER via ER complex destabilization or direct enzymatic ubiquitination. However, these new approaches do not broadly treat all cancer-involved receptors, including GPER. The latter is concerning since GPER is directly associated with tumor size, distant metastases, cancer stem cell activity, and endocrine resistance, indicating the importance of targeting this receptor to achieve a more complete therapeutic response. This review focuses on the critical importance and value of GPER-targeted therapeutics as part of a more holistic approach to the treatment of estrogen-driven malignancies.

Connecting G protein-coupled estrogen receptor biomolecular mechanisms with the pathophysiology of preeclampsia: a review

BACKGROUND

Throughout the course of pregnancy, small maternal spiral arteries that are in contact with fetal tissue undergo structural remodeling, lose smooth muscle cells, and become less responsive to vasoconstrictors. Additionally, placental extravillous trophoblasts invade the maternal decidua to establish an interaction between the fetal placental villi with the maternal blood supply. When successful, this process enables the transport of oxygen, nutrients, and signaling molecules but an insufficiency leads to placental ischemia. In response, the placenta releases vasoactive factors that enter the maternal circulation and promote maternal cardiorenal dysfunction, a hallmark of preeclampsia (PE), the leading cause of maternal and fetal death. An underexplored mechanism in the development of PE is the impact of membrane-initiated estrogen signaling via the G protein-coupled estrogen receptor (GPER). Recent evidence indicates that GPER activation is associated with normal trophoblast invasion, placental angiogenesis/hypoxia, and regulation of uteroplacental vasodilation, and these mechanisms could explain part of the estrogen-induced control of uterine remodeling and placental development in pregnancy.

CONCLUSION

Although the relevance of GPER in PE remains speculative, this review provides a summary of our current understanding on how GPER stimulation regulates some of the features of normal pregnancy and a potential link between its signaling network and uteroplacental dysfunction in PE. Synthesis of this information will facilitate the development of innovative treatment options.

Breast cancer progression and kynurenine pathway enzymes are induced by hexachlorobenzene exposure in a Her2-positive model

Breast cancer is one of the leading cancers among women worldwide. Given the evidence that pesticides play an important role in breast cancer, interest has grown in pesticide impact on disease progression. Hexachlorobenzene (HCB), an aryl hydrocarbon receptor (AhR) ligand, promotes triple-negative breast cancer cell migration and invasion. Estrogen receptor β (ERβ) inhibits cancer motility, while G protein-coupled ER (GPER) modulates the neoplastic transformation. Tryptophan is metabolized through the kynurenine pathway by indoleamine-2,3-dioxygenase (IDO) and tryptophan-2,3-dioxygenase (TDO), with kynurenine signaling activation often predicting worse prognosis in cancer. In this context, we examined the HCB (0.005; 0.05; 0.5 and 5 μM) effect on LM3 cells, a human epidermal growth factor receptor 2 (HER2)-positive breast cancer model. Results show that HCB increases IDO and TDO mRNA levels and promotes cell viability, proliferation and migration through the AhR pathway. Moreover, HCB boosts mammosphere formation, vascular endothelial growth factor and cyclooxygenase-2 expression and reduces IL-10 levels. For some parameters, U-shaped or inverted U-shaped dose-response curves are shown. HCB alters ER levels, reducing ERβ while increasing GPER. These results demonstrate that exposure to environmentally relevant concentrations of HCB up-regulates the kynurenine pathway and dysregulates ERβ and GPER levels, collaborating in HER2-positive breast cancer progression.

Aberrant epigenetic regulation of estrogen and progesterone signaling at the level of endometrial/endometriotic tissue in the pathomechanism of endometriosis

Endometriosis is a term referring to a condition whereby the endometrial tissue is found outside the uterine cavity. This progressive and debilitating condition affects up to 15% of women of reproductive age. Due to the fact that endometriosis cells may express estrogen receptors (ERα, Erβ, GPER) and progesterone (P4) receptors (PR-A, PR-B), their growth, cyclic proliferation, and breakdown are similar to the processes occurring in the endometrium. The underlying etiology and pathogenesis of endometriosis are still not fully explained. The retrograde transport of viable menstrual endometrial cells with the retained ability to attach within the pelvic cavity, proliferate, differentiate and invade into the surrounding tissue explains the most widely accepted implantation theory. Endometrial stromal cells (EnSCs) with clonogenic potential constitute the most abundant population of cells within endometrium that resemble the properties of mesenchymal stem cells (MSCs). Accordingly, formation of the endometriotic foci in endometriosis may be due to a kind of EnSCs dysfunction. Increasing evidence indicates the underestimated role of epigenetic mechanisms in the pathogenesis of endometriosis. Hormone-mediated epigenetic modifications of the genome in EnSCs or even MSCs were attributed an important role in the etiopathogenesis of endometriosis. The roles of excess estrogen exposure and P4 resistance were also found to be crucial in the development of epigenetic homeostasis failure. Therefore, the aim of this review was to consolidate the current knowledge regarding the epigenetic background of EnSCs and MSCs and the changed properties due to estrogen/P4 imbalances in the context of the etiopathogenesis of endometriosis.

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.

Role of the G Protein-Coupled Receptors in Cancer and Stromal Cells: From Functions to Novel Therapeutic Perspectives

G protein-coupled receptors (GPCRs) are transmembrane signal transducers that regulate a plethora of physiological and pathological processes [...].

Implications of estrogen and its receptors in colorectal carcinoma

Estrogens have been implicated in the pathogenesis of various cancer types, including colorectal carcinoma (CRC). Estrogen receptors such as ERα and ERβ activate intracellular signaling cascades followed by binding to estrogen, resulting in important changes in cellular behaviors. The nuclear estrogen receptors, i.e. ERβ and ERα are responsible for the genomic actions of estrogens, whereas the other receptor, such as G protein-coupled estrogen receptor (GPER) regulates rapid non-genomic actions, which lead to secondary gene expression changes in cells. ERβ, the predominant estrogen receptor expressed in both normal and non-malignant colonic epithelium, has protective roles in colon carcinogenesis. ERβ may exert the anti-tumor effect through selective activation of pro-apoptotic signaling, increasing DNA repair, inhibiting expression of oncogenes, regulating cell cycle progression, and also by changing the micro-RNA pool and DNA-methylation. Thus, a better understanding of the underlying mechanisms of estrogen and its receptors in CRC pathogenesis could provide a new horizon for effective therapeutic development. Furthermore, using synthetic or natural compounds as ER agonists may induce estrogen-mediated anti-cancer activities against colon cancer. In this study, we report the most recent pre-clinical and experimental evidences related to ERs in CRC development. Also, we reviewed the actions of naturally occurring and synthetic compounds, which have a protective role against CRC development by acting as ER agonist.

Multifaceted Interplay between Hormones, Growth Factors and Hypoxia in the Tumor Microenvironment

Simple Summary

Hormones and growth factors impact many processes in the cell. Moreover, these molecules influence tumor growth, as does a lack of oxygen (hypoxia) that characterizes cancer progression. Proteins that are stabilized by low oxygen tension, known as hypoxia-inducible factors (HIFs), help tumor cells to adapt to their environment. Of note, hormones and growth factors regulate the activity of HIFs toward malignant aggressiveness, including the resistance to therapy. In this review, we summarize the current knowledge regarding the role of hormones and growth factors in cancer development with a particular focus on their interplay with hypoxia and HIFs and comment on how these factors influence the response to cancer immunotherapy.

Abstract

Hormones and growth factors (GFs) are signaling molecules implicated in the regulation of a variety of cellular processes. They play important roles in both healthy and tumor cells, where they function by binding to specific receptors on target cells and activating downstream signaling cascades. The stages of tumor progression are influenced by hormones and GF signaling. Hypoxia, a hallmark of cancer progression, contributes to tumor plasticity and heterogeneity. Most solid tumors contain a hypoxic core due to rapid cellular proliferation that outgrows the blood supply. In these circumstances, hypoxia-inducible factors (HIFs) play a central role in the adaptation of tumor cells to their new environment, dramatically reshaping their transcriptional profile. HIF signaling is modulated by a variety of factors including hormones and GFs, which activate signaling pathways that enhance tumor growth and metastatic potential and impair responses to therapy. In this review, we summarize the role of hormones and GFs during cancer onset and progression with a particular focus on hypoxia and the interplay with HIF proteins. We also discuss how hypoxia influences the efficacy of cancer immunotherapy, considering that a hypoxic environment may act as a determinant of the immune-excluded phenotype and a major hindrance to the success of adoptive cell therapies.

Syringaresinol attenuates sepsis-induced cardiac dysfunction by inhibiting inflammation and pyroptosis in mice

The mortality of sepsis-induced cardiac dysfunction (SICD) is very high due to the complex pathophysiological mechanism. Syringaresinol (SYR) is a natural abstract which possesses anti-inflammatory property. The present study aims was to identify the protective impact of SYR on sepsis-induced cardiac dysfunction and investigate the specific mechanisms. We found that SYR improved the cardiac function and alleviated myocardial injury in mice that subjected to cecal ligation and puncture, in addition, SIRT1 expression was significantly elevated after SYR treatment compared to sepsis group both in vivo and in vitro, along with suppression of NLRP3 activation and proinflammatory cytokines release. However, SIRT1 inhibitor EX427 abolished the impact of SYR on LPS-induced pyroptosis in cardiomyocytes. Furthermore, molecular docking analysis predicted that there is high affinity between SYR and estrogen receptor (ER), ER inhibitor ICI182780, the specific ERβ inhibitor PHTP and the specific ERαinhibitor AZD9496 were used to examine the role of ER in the protective effect of SYR against SICD, and the results suggested that ER activation was essential for the cardioprotective function of SYR. In conclusion, SYR ameliorates SICD via the ER/SIRT1/NLRP3/GSDMD pathway.

Kaempferol-induced GPER upregulation attenuates atherosclerosis via the PI3K/AKT/Nrf2 pathway

CONTEXT

The effect of kaempferol, a regulator of oestrogen receptors, on atherosclerosis (AS) and the underlying mechanism is elusive.

OBJECTIVE

To explore the effect and mechanism of kaempferol on AS.

METHODS AND MATERIALS

In vivo, C57BL/6 and apolipoprotein E (APOE)^-/- mice were randomly categorized into six groups (C57BL/6: control, ovariectomy (OVX), high-fat diet (HFD); APOE^-/-: OVX-HFD, OVX-HFD + kaempferol (50 mg/kg) and OVX-HFD + kaempferol (100 mg/kg) and administered with kaempferol for 16 weeks, intragastrically. Oil-Red and haematoxylin-eosin (HE) staining were employed to examine the effect of kaempferol. In vitro, human aortic endothelial cells (HAECs) were pre-treated with or without kaempferol (5, 10 or 20 μM), followed by administration with kaempferol and oxidized low-density lipoprotein (ox-LDL) (200 μg/mL). The effect of kaempferol was evaluated using flow cytometry, and TdT-mediated dUTP Nick-End Labelling (TUNEL).

RESULTS

In vivo, kaempferol (50 and 100 mg/kg) normalized the morphology of blood vessels and lipid levels and suppressed inflammation and apoptosis. It also activated the G protein-coupled oestrogen receptor (GPER) and PI3K/AKT/nuclear factor-erythroid 2-related factor 2 (Nrf2) pathways. In vitro, ox-LDL (200 μg/mL) reduced the cell viability to 50% (IC₅₀). Kaempferol (5, 10 or 20 μM) induced-GPER activation increased cell viability to nearly 10%, 19.8%, 30%, and the decreased cellular reactive oxygen species (ROS) generation (16.7%, 25.6%, 31.1%), respectively, consequently attenuating postmenopausal AS. However, the protective effects of kaempferol were blocked through co-treatment with si-GPER.

CONCLUSIONS

The beneficial effects of kaempferol against postmenopausal AS are associated with the PI3K/AKT/Nrf2 pathways, mediated by the activation of GPER.

Estrogen- and Progesterone (P4)-Mediated Epigenetic Modifications of Endometrial Stromal Cells (EnSCs) and/or Mesenchymal Stem/Stromal Cells (MSCs) in the Etiopathogenesis of Endometriosis

Endometriosis is a common chronic inflammatory condition in which endometrial tissue appears outside the uterine cavity. Because ectopic endometriosis cells express both estrogen and progesterone (P4) receptors, they grow and undergo cyclic proliferation and breakdown similar to the endometrium. This debilitating gynecological disease affects up to 15% of reproductive aged women. Despite many years of research, the etiopathogenesis of endometrial lesions remains unclear. Retrograde transport of the viable menstrual endometrial cells with retained ability for attachment within the pelvic cavity, proliferation, differentiation and subsequent invasion into the surrounding tissue constitutes the rationale for widely accepted implantation theory. Accordingly, the most abundant cells in the endometrium are endometrial stromal cells (EnSCs). These cells constitute a particular population with clonogenic activity that resembles properties of mesenchymal stem/stromal cells (MSCs). Thus, a significant role of stem cell-based dysfunction in formation of the initial endometrial lesions is suspected. There is increasing evidence that the role of epigenetic mechanisms and processes in endometriosis have been underestimated. The importance of excess estrogen exposure and P4 resistance in epigenetic homeostasis failure in the endometrial/endometriotic tissue are crucial. Epigenetic alterations regarding transcription factors of estrogen and P4 signaling pathways in MSCs are robust in endometriotic tissue. Thus, perspectives for the future may include MSCs and EnSCs as the targets of epigenetic therapies in the prevention and treatment of endometriosis. Here, we reviewed the current known changes in the epigenetic background of EnSCs and MSCs due to estrogen/P4 imbalances in the context of etiopathogenesis of endometriosis. Graphical Abstract.

Biased and allosteric modulation of bone cell-expressing G protein-coupled receptors as a novel approach to osteoporosis therapy

On the cellular level, osteoporosis (OP) is a result of imbalanced bone remodeling, in which osteoclastic bone resorption outcompetes osteoblastic bone formation. Currently available OP medications include both antiresorptive and bone-forming drugs. However, their long-term use in OP patients, mainly in postmenopausal women, is accompanied by severe side effects. Notably, the fundamental coupling between bone resorption and formation processes underlies the existence of an undesirable secondary outcome that bone anabolic or anti-resorptive drugs also reduce bone formation. This drawback requires the development of anti-OP drugs capable of selectively stimulating osteoblastogenesis and concomitantly reducing osteoclastogenesis. We propose that the application of small synthetic biased and allosteric modulators of bone cell receptors, which belong to the G-protein coupled receptors (GPCR) family, could be the key to resolving the undesired anti-OP drug selectivity. This approach is based on the capacity of these GPCR modulators, unlike the natural ligands, to trigger signaling pathways that promote beneficial effects on bone remodeling while blocking potentially deleterious effects. Under the settings of OP, an optimal anti-OP drug should provide fine-tuned regulation of downstream effects, for example, intermittent cyclic AMP (cAMP) elevation, preservation of Ca²⁺ balance, stimulation of osteoprotegerin (OPG) and estrogen production, suppression of sclerostin secretion, and/or preserved/enhanced canonical β-catenin/Wnt signaling pathway. As such, selective modulation of GPCRs involved in bone remodeling presents a promising approach in OP treatment. This review focuses on the evidence for the validity of our hypothesis.

A Clinicopathologic Study on the Role of Estrogen, Progesterone, and Their Classical and Nonclassical Receptors in Cutaneous Neurofibromas of Individuals With Neurofibromatosis 1

OBJECTIVES

To evaluate the expression of progesterone receptor (PR), estrogen receptor (ER), and G protein-coupled estrogen receptor 1 (GPER-1) in cutaneous neurofibromas (cNFs) and their correlation with demographic, clinical, and laboratory data of individuals with neurofibromatosis 1 (NF1). The association of PROGINS polymorphism and PR expression in cNFs, as well as the serum steroidal hormones and the number of cNFs, was investigated.

METHODS

The sample comprised 80 large and 80 small cNFs from 80 individuals with NF1. PR, ER, GPER-1, and Ki-67 expression were investigated by immunohistochemistry in tissue micro- and macroarrays and quantified using a digital computer-assisted method. The number of cNFs, the levels of serum 17β estradiol and progesterone, and the PROGINS polymorphism were identified.

RESULTS

Twelve (8.5%) small cNFs were weakly positive for ER, 131 (92.3%) cNFs expressed PR, and all (100%) cNFs expressed GPER-1. Large cNFs showed a higher expression of PR (P < .0001) and GPER-1 (P = .019) and had a higher intensity of staining for these receptors (P < .0001). The cell proliferation index was positively correlated with PR (P = .001). Persons with more cNFs had higher serum levels of progesterone (P = .001).

CONCLUSIONS

These findings emphasize the role of estrogen and progesterone in cNF development and suggest that these hormones may act on cNF cells via a noncanonical pathway through GPER-1.

Role of G Protein-Coupled Estrogen Receptor in Digestive System Carcinomas: A Minireview

Digestive system carcinomas are one of the leading causes of cancer-related deaths worldwide. G protein-coupled estrogen receptor (GPER), a novel estrogen receptor, has been recognized as an important mediator in numerous cancer types. Recently, the function and clinical significance of GPER in digestive system carcinomas has been a subject of interest. Increasing evidence has revealed that GPER plays an important role as a potential biomarker in digestive system carcinomas. This work summarizes the recent literature and focuses on the emerging functional role of GPER in digestive system carcinomas, including gastric cancer, hepatocellular carcinoma, pancreatic cancer, and colorectal cancer. The potential application of GPER in novel strategies for the diagnosis and treatment of digestive system carcinomas is discussed and highlighted.

Proteolytic Targeting Chimeras with Specificity for Plasma Membrane and Intracellular Estrogen Receptors

Decisions regarding the assignment of hormonal therapy for breast cancer are based solely upon the presence of nuclear estrogen receptors (ERs) in biopsied tumor tissue. This is despite the fact that the G-protein-coupled estrogen receptor (GPER) is linked to advanced breast cancer and is required for breast cancer stem cell survival, an observation that suggests that effective endocrine therapy should also target this receptor. Here, two ER/GPER-targeting proteolytic chimeras (UI-EP001 and UI-EP002) are described that effectively degrade ERα, ERβ, and GPER. These chimeras form high-affinity interactions with GPER and ER with binding dissociation constants of ∼30 nM and 10-20 nM, respectively. Plasma membrane and intracellular GPER and nuclear ER were degraded by UI-EP001 and UI-EP002, but not by a partial proteolytic targeting chimera (PROTAC) lacking its estrogen-targeting domain. Pretreatment of cells with the proteasomal inhibitor, MG132, blocked UI-EP001 and UI-EP002 proteolysis, while the lysosomotrophic inhibitor, chloroquine, had no effect. The off-target activity was not observed against recombinant β1-adrenergic receptor or CXCR4. Target specificity was further demonstrated in human MCF-7 cells where both drugs effectively degraded ERα, ERβ, and GPER, sparing the progesterone receptor (PR). UI-EP001 and UI-EP002 induced cytotoxicity and G2/M cell cycle arrest in MCF-7 breast cancer and human SKBR3 (ERα-ERβ-GPER+) breast cancer cells but not human MDA-MB-231 breast cancer cells that do not express functional GPER/ER. These results suggest that it is possible to develop a receptor-based strategy of antiestrogen treatment for breast cancer that targets both plasma membrane and intracellular estrogen receptors.

Cholesterol and Sphingolipid Enriched Lipid Rafts as Therapeutic Targets in Cancer

Lipid rafts are critical cell membrane lipid platforms enriched in sphingolipid and cholesterol content involved in diverse cellular processes. They have been proposed to influence membrane properties and to accommodate receptors within themselves by facilitating their interaction with ligands. Over the past decade, technical advances have improved our understanding of lipid rafts as bioactive structures. In this review, we will cover the more recent findings about cholesterol, sphingolipids and lipid rafts located in cellular and nuclear membranes in cancer. Collectively, the data provide insights on the role of lipid rafts as biomolecular targets in cancer with good perspectives for the development of innovative therapeutic strategies.

GPER1 Silencing Suppresses the Proliferation, Migration, and Invasion of Gastric Cancer Cells by Inhibiting PI3K/AKT-Mediated EMT

G protein coupled estrogen receptor (GPER1) is a membrane estrogen receptor, belonging to the seven-transmembrane G protein-coupled receptors family, and has important biological functions in cancer. However, the functional role of GPER1 in gastric cancer (GC) remain incompletely understood. In the present study, we employed gene set enrichment analysis and discovered that GPER1 expression was concomitant with EMT process and was positively correlated with activation of the PI3K/AKT pathway in GC. Knockdown of GPER1 with siRNA suppressed the proliferation, migration, and invasion of AGS and MGC-803 GC cells. Knockdown of GPER1 also downregulated the mesenchymal markers N-cadherin and vimentin, upregulated E-cadherin, an epithelial marker, and suppressed expression of the Snail, Slug and Twist1 transcription factors, indicating that knockdown of GPER1 inhibited EMT. Moreover, 740Y-P, a PI3K activator, reversed the effects of GPER1 knockdown on EMT processes. Overexpression of GPER1 with plasmid can further prove these findings. In summary, these data demonstrate that GPER1 inhibition suppresses the proliferation, migration, and invasion of gastric cancer cells by inhibiting PI3K/AKT-mediated EMT. Our study elucidated the function of GPER1 in gastric cancer, and we identified PI3K/AKT-mediated EMT as a novel mechanism by which GPER1 contributes to proliferation, migration, and invasion of gastric cancer. These data suggest that combining inhibition of GPER1 and PI3K may be a potential therapeutic approach to inhibit gastric cancer metastasis.

Therapeutic Perspectives on the Modulation of G-Protein Coupled Estrogen Receptor, GPER, Function

Estrogens exert their physiological and pathophysiological effects via cellular receptors, named ERα, ERβ, and G-protein coupled estrogen receptor (GPER). Estrogen-regulated physiology is tightly controlled by factors that regulate estrogen bioavailability and receptor sensitivity, while disruption of these control mechanisms can result in loss of reproductive function, cancer, cardiovascular and neurodegenerative disease, obesity, insulin resistance, endometriosis, and systemic lupus erythematosus. Restoration of estrogen physiology by modulating estrogen bioavailability or receptor activity is an effective approach for treating these pathological conditions. Therapeutic interventions that block estrogen action are employed effectively for the treatment of breast and prostate cancer as well as for precocious puberty and anovulatory infertility. Theoretically, treatments that block estrogen biosynthesis should prevent estrogen action at ERs and GPER, although drug resistance and ligand-independent receptor activation may still occur. In addition, blockade of estrogen biosynthesis does not prevent activation of estrogen receptors by naturally occurring or man-made exogenous estrogens. A more complicated scenario is provided by anti-estrogen drugs that antagonize ERs since these drugs function as GPER agonists. Based upon its association with metabolic dysregulation and advanced cancer, GPER represents a therapeutic target with promise for the treatment of several critical health concerns facing Western society. Selective ligands that specifically target GPER have been developed and may soon serve as pharmacological agents for treating human disease. Here, we review current forms of estrogen therapy and the implications that GPER holds for these therapies. We also discuss existing GPER targeted drugs, additional approaches towards developing GPER-targeted therapies and how these therapies may complement existing modalities of estrogen-targeted therapy.

Membrane Estrogen Receptor (GPER) and Follicle-Stimulating Hormone Receptor (FSHR) Heteromeric Complexes Promote Human Ovarian Follicle Survival

Classically, follicle-stimulating hormone receptor (FSHR)-driven cAMP-mediated signaling boosts human ovarian follicle growth and oocyte maturation. However, contradicting in vitro data suggest a different view on physiological significance of FSHR-mediated cAMP signaling. We found that the G-protein-coupled estrogen receptor (GPER) heteromerizes with FSHR, reprogramming cAMP/death signals into proliferative stimuli fundamental for sustaining oocyte survival. In human granulosa cells, survival signals are missing at high FSHR:GPER ratio, which negatively impacts follicle maturation and strongly correlates with preferential Gαs protein/cAMP-pathway coupling and FSH responsiveness of patients undergoing controlled ovarian stimulation. In contrast, FSHR/GPER heteromers triggered anti-apoptotic/proliferative FSH signaling delivered via the Gβγ dimer, whereas impairment of heteromer formation or GPER knockdown enhanced the FSH-dependent cell death and steroidogenesis. Therefore, our findings indicate how oocyte maturation depends on the capability of GPER to shape FSHR selective signals, indicating hormone receptor heteromers may be a marker of cell proliferation.

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G-protein-coupled estrogen receptor (GPER) interacts with FSH receptor (FSHR)

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FSHR/GPER heteromers reprogram FSH-induced death signals to proliferative stimuli

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Anti-apoptotic signaling of heteromers is via a GPER-Gαs inhibitory complex and Gβγ

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Heteromer formation impacts follicle maturation and FSH responses of IVF patients

G-protein Coupled Estrogen Receptor Expression in Growth Hormone Secreting and Non-Functioning Adenomas

PURPOSE

To evaluate the expression of G-protein coupled estrogen receptor (GPER1), aromatase, estrogen receptor α (ERα), estrogen receptor β (ERβ), pituitary tumor transforming gene (PTTG), and fibroblast growth factor 2 (FGF2) in GH-secreting and non-functioning adenomas (NFA).

METHODS

Thirty patients with acromegaly and 27 patients with NFA were included. Gene expression was determined via quantitative reverse transcription polymerase chain reaction (QRT-PCR). Protein expression was determined via immunohistochemistry.

RESULTS

There was no difference, in terms of gene expression of aromatase, ERα, PTTG, and FGF2 between the two groups (p>0.05 for all). ERβ gene expression was higher and GPER1 gene expression was lower in GH-secreting adenomas than NFAs (p<0.05 for all). Aromatase and ERβ protein expression was higher in GH-secreting adenomas than NFAs (p=0.01). None of the tumors expressed ERα. GPER1 expression was detected in 62.2% of the GH-secreting adenomas and 45% of NFAs. There was no difference in terms of GPER1, PTTG, FGF2 H scores between the two groups (p>0.05 for all). GPER1 gene expression was positively correlated to ERα, ERβ, PTTG, and FGF2 gene expression (p<0.05 for all). There was a positive correlation between aromatase and GPER1 protein expression (r=0.31; p=0.04).

CONCLUSIONS

GPER1 is expressed at both gene and protein level in a substantial portion of GH-secreting adenomas and NFAs. The finding of a positive correlation between GPER1 and ERα, ERβ, PTTG, and FGF2 gene expression and aromatase and GPER1 protein expression suggests GPER1 along with aromatase and classical ERs might mediate the effects of estrogen through upregulation of PTTG and FGF2.

The G Protein-Coupled Estrogen Receptor (GPER) Expression Correlates with Pro-Metastatic Pathways in ER-Negative Breast Cancer: A Bioinformatics Analysis

The G protein-coupled estrogen receptor (GPER, formerly known as GPR30) is a seven-transmembrane receptor that mediates estrogen signals in both normal and malignant cells. In particular, GPER has been involved in the activation of diverse signaling pathways toward transcriptional and biological responses that characterize the progression of breast cancer (BC). In this context, a correlation between GPER expression and worse clinical-pathological features of BC has been suggested, although controversial data have also been reported. In order to better assess the biological significance of GPER in the aggressive estrogen receptor (ER)-negative BC, we performed a bioinformatics analysis using the information provided by The Invasive Breast Cancer Cohort of The Cancer Genome Atlas (TCGA) project and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) datasets. Gene expression correlation and the statistical analysis were carried out with R studio base functions and the tidyverse package. Pathway enrichment analysis was evaluated with Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway on the Database for Annotation, Visualization and Integrated Discovery (DAVID) website, whereas gene set enrichment analysis (GSEA) was performed with the R package phenoTest. The survival analysis was determined with the R package survivALL. Analyzing the expression data of more than 2500 primary BC, we ascertained that GPER levels are associated with pro-migratory and metastatic genes belonging to cell adhesion molecules (CAMs), extracellular matrix (ECM)-receptor interaction, and focal adhesion (FA) signaling pathways. Thereafter, evaluating the disease-free interval (DFI) in ER-negative BC patients, we found that the subjects expressing high GPER levels exhibited a shorter DFI in respect to those exhibiting low GPER levels. Overall, our results may pave the way to further dissect the network triggered by GPER in the breast malignancies lacking ER toward a better assessment of its prognostic significance and the action elicited in mediating the aggressive features of the aforementioned BC subtype.

GPER and Testicular Germ Cell Cancer

The G protein-coupled estrogen receptor (GPER), also known as GPR30, is a widely conserved 7-transmembrane-domain protein which has been identified as a novel 17β-estradiol-binding protein that is structurally distinct from the classic oestrogen receptors (ERα and ERβ). There are still conflicting data regarding the exact role and the natural ligand of GPER/GPR30 in reproductive tracts as both male and female knock-out mice are fertile and have no abnormalities of reproductive organs. Testicular germ cell cancers (TGCCs) are the most common malignancy in young males and the most frequent cause of death from solid tumors in this age group. Clinical and experimental studies suggested that estrogens participate in the physiological and pathological control of male germ cell proliferation. In human seminoma cell line, while 17β-estradiol (E2) inhibits in vitro cell proliferation through an ERβ-dependent mechanism, an impermeable E2 conjugate (E2 coupled to BSA), in vitro cell proliferation is stimulated by activating ERK1/2 and protein kinase A through a membrane GPCR that we further identified as GPER/GPR30. The same effect was observed with low but environmentally relevant doses of BPA, an estrogenic endocrine disrupting compound. Furthermore, GPER/GPR30 is specifically overexpressed in seminomas but not in non-seminomas and this overexpression is correlated with an ERβ-downregulation. This GPER/GPR30 overexpression could be linked to some genetic variations, as single nucleotide polymorphisms, which was also reported in other hormone-dependent cancers. We will review here the implication of GPER/GPR30 in TGCCs pathophysiology and the arguments to consider GPER/GPR30 as a potential therapeutic target in humans.

G protein-coupled estrogen receptor in colon function, immune regulation and carcinogenesis

Estrogens play important roles in the development and progression of multiple tumor types. Accumulating evidence points to the significance of estrogen action not only in tumors of hormonally regulated tissues such as the breast, endometrium and ovary, but also in the development of colorectal cancer (CRC). The effects of estrogens in physiological and pathophysiological conditions are mediated by the nuclear estrogen receptors α and β, as well as the membrane-bound G protein-coupled estrogen receptor (GPER). The roles of GPER in CRC development and progression, however, remain poorly understood. Studies on the functions of GPER in the colon have shown that this estrogen receptor regulates colonic motility as well as immune responses in CRC-associated diseases, such as Crohn’s disease and ulcerative colitis. GPER is also involved in cell cycle regulation, endoplasmic reticulum stress, proliferation, apoptosis, vascularization, cell migration, and the regulation of fatty acid and estrogen metabolism in CRC cells. Thus, multiple lines of evidence suggest that GPER may play an important role in colorectal carcinogenesis. In this review, we present the current state of knowledge regarding the contribution of GPER to colon function and CRC.

Downregulation of G Protein-Coupled Estrogen Receptor (GPER) is Associated with Reduced Prognosis in Patients with Gastric Cancer

BACKGROUND This study is aimed to investigate the prognostic significance of the expression of G protein-coupled estrogen receptor (GPER) in gastric cancer tissue using bioinformatics data and immunohistochemistry. MATERIAL AND METHODS Expression of GPER mRNA in gastric cancer tissues and normal adjacent tissues was investigated using data from The Cancer Genome Atlas (TCGA), the Gene Expression Omnibus (GEO), and Oncomine database. Kaplan-Meier Plotter identified the association between GPER mRNA and prognosis. Correlation between GPER mRNA and DNA methylation used the cBioPortal for Cancer Genomics and the MethHC website. Genes co-expressed with GPER were identified from The Cancer Genome Atlas Stomach Adenocarcinoma (TCGA-STAD) underwent FunRich analysis. Immunohistochemistry and Western blot evaluated GPER protein expression in tissue microarrays (TMAs) and gastric cancer cell lines. RESULTS GPER mRNA and protein levels were significantly lower in gastric cancer tissue and cells lined when compared with normal tissues and cells. The results from GSE15459 showed that patients with low levels of GPER mRNA had a reduced overall survival (OS) (P=0.013) and disease-free survival (DFS) (P=0.019). A negative correlation (r=-0.611) between GPER mRNA and DNA methylation was found using the cBioPortal and MethHC. Co-expressed epithelial-mesenchymal transformation (EMT) genes were enriched with GPER (P<0.0001). Cox regression analysis showed that GPER protein expression was an independent prognostic factor (P=0.035) CONCLUSIONS Downregulation of GPER predicts poor prognosis in gastric cancer. GPER may act as a tumor suppressor through the regulation of EMT in gastric cancer.

Autocrine motility factor promotes endometrial cancer progression by targeting GPER-1

Background

Autocrine motility factor (AMF) is a critical factor regulating aggressiveness of endometrial cancer (EC). Multiple pieces of evidence indicate that it is through G protein coupled estrogen receptor (GPER) signaling pathway that some growth factors promoted the migration and proliferation of tumor cells. The aim of this study is to explore the role of GPER-1 in AMF mediated regulatory mechanisms of EC recurrence and progression.

Methods

Real-Time Cell Analysis (RTCA) assays were performed to assess whether AMF depends on Autocrine motility factor recepter (AMFR) signaling in EC cells. A genome-wide expression microarray and Yeast Two-Hybrid assay were used to detect AMF and GPER-1 interaction in the context of AMFR depletion, and co-immunoprecipitation and immunofluorescence experiments were performed to confirm the physical interaction. Isobaric Tags for Relative and Absolute Quantification (iTRAQ) analysis was used for the identification of the target pathway activated by AMF-GPER-1 interaction. Cohorts of mice harboring xenografts derived from modified SPEC2 cell lines were treated with or without exogenous AMF to validate the results of previous experiments. Immunohistochemistry was performed to assess AMF and GPER-1 expression in endometrial cancer specimens and normal endometrium.

Results

Our data showed that GPER-1 binds to AMF and the formed complex translocates from the plasma membrane to the cytoplasm. Mechanistic investigations demonstrated that interaction between AMF and GPER-1 triggers phosphoinositide-3-kinase signaling and promotes EC cell growth. More importantly, through animal experiments and human tissue experiments, we found that AMF contributes to GPER-1-mediated EC progression, which is consistent with the above observations.

Conclusions

Our work not only delineated the regulatory mechanisms of endometrial cancer progression by AMF-GPER-1-AKT signaling cascade but also laid the foundation of targeting this pathway for treating endometrial cancer.

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0336-4) contains supplementary material, which is available to authorized users.

G-Protein Coupled Estrogen Receptor in Breast Cancer

The G-protein coupled estrogen receptor (GPER), an alternate estrogen receptor (ER) with a structure distinct from the two canonical ERs, being ERα, and ERβ, is expressed in 50% to 60% of breast cancer tissues and has been presumed to be associated with the development of tamoxifen resistance in ERα positive breast cancer. On the other hand, triple-negative breast cancer (TNBC) constitutes 15% to 20% of breast cancers and frequently displays a more aggressive behavior. GPER is prevalent and involved in TNBC and can be a therapeutic target. However, contradictory results exist regarding the function of GPER in breast cancer, proliferative or pro-apoptotic. A better understanding of the GPER, its role in breast cancer, and the interactions with the ER and epidermal growth factor receptor will be beneficial for the disease management and prevention in the future.

Adenosine Attenuates LPS-Induced Cardiac Dysfunction by Inhibition of Mitochondrial Function via the ER Pathway

Sepsis is a life-threatening organ dysfunction syndrome with a high rate of mortality. It is caused by an abnormal immune response to infection, and the occurrence of sepsis-induced cardiomyopathy is the primary cause of death. The present study was designed to examine the effects of adenosine on lipopolysaccharide- (LPS-) induced cardiac anomalies and the underlying mechanisms involved. Adenosine (25, 50, and 100 mg/kg, i.g., 2 times/day) was administered for three days, followed by the induction of sepsis by intraperitoneal injection of LPS (10 mg/kg/2h). The effects of adenosine on inflammatory factors, LVEF, LVFS, and MAPK in septic rats (half male and half female) were observed. Subsequently, the effect of adenosine (10 μM) on the mitochondrial function of H9c2 cells stimulated with LPS (20 μg/mL, 24 h) was observed in the presence and absence of the estrogen receptor-specific antagonist ICI182,780. The results show that medium to high doses of adenosine can significantly promote cardiac function (LVEF and LVFS) and reduce the levels of inflammatory factors (TNF-α, IL-6, PCT, and cTnI) and p-JNK in septic rats, with a significant difference seen between male and female rats. The results of flow cytometry show that adenosine significantly inhibited increases in ROS levels, mitochondrial membrane potential, and the swelling degree of mitochondria in H9c2 cells stimulated with LPS, but this effect could be blocked by ICI182,780, indicating that adenosine attenuated LPS-induced cardiac dysfunction by inhibiting mitochondrial function via the ER pathway.

The role of menopausal hormone therapy in women with or at risk of ovarian and breast cancers: Misconceptions and current directions

For women who are candidates for menopausal hormone therapy (MHT), estrogen can provide relief from symptomatic menopause, decrease rates of chronic illnesses, and improve health-related quality of life. However, confusion surrounds the evidence regarding the impact of exogenous estrogen and progesterone on the breast and ovary. Available data regarding the risks of MHT (estrogen and/or progestin) related to the development of breast and ovarian cancer are often inconsistent or incomplete. Modern molecular and genetic techniques have improved our understanding of the heterogeneity of breast and ovarian cancer. This enhanced understanding of the disease has impacted our understanding of carcinogenesis. Treatment options have evolved to be more targeted toward hormonal therapy for certain subtypes of disease, whereas cytotoxic chemotherapy remains the standard for other histological and molecular subtypes. The role of MHT in the breast and ovarian cancer survivor, as well as women who are at high risk for the development of hereditary breast and ovarian cancer, remains controversial despite evidence that this treatment can improve quality of life and survival outcomes. Through this article, we examine the evidence for and against the use of MHT with a focus on women who have or are at high risk for breast and ovarian cancer.

GPCR Modulation in Breast Cancer

Breast cancer is the most prevalent cancer found in women living in developed countries. Endocrine therapy is the mainstay of treatment for hormone-responsive breast tumors (about 70% of all breast cancers) and implies the use of selective estrogen receptor modulators and aromatase inhibitors. In contrast, triple-negative breast cancer (TNBC), a highly heterogeneous disease that may account for up to 24% of all newly diagnosed cases, is hormone-independent and characterized by a poor prognosis. As drug resistance is common in all breast cancer subtypes despite the different treatment modalities, novel therapies targeting signaling transduction pathways involved in the processes of breast carcinogenesis, tumor promotion and metastasis have been subject to accurate consideration. G protein-coupled receptors (GPCRs) are the largest family of cell-surface receptors involved in the development and progression of many tumors including breast cancer. Here we discuss data regarding GPCR-mediated signaling, pharmacological properties and biological outputs toward breast cancer tumorigenesis and metastasis. Furthermore, we address several drugs that have shown an unexpected opportunity to interfere with GPCR-based breast tumorigenic signals.

miR-338-3p Is Regulated by Estrogens through GPER in Breast Cancer Cells and Cancer-Associated Fibroblasts (CAFs)

Estrogens acting through the classic estrogen receptors (ERs) and the G protein estrogen receptor (GPER) regulate the expression of diverse miRNAs, small sequences of non-coding RNA involved in several pathophysiological conditions, including breast cancer. In order to provide novel insights on miRNAs regulation by estrogens in breast tumor, we evaluated the expression of 754 miRNAs by TaqMan Array in ER-negative and GPER-positive SkBr3 breast cancer cells and cancer-associated fibroblasts (CAFs) upon 17β-estradiol (E2) treatment. Various miRNAs were regulated by E2 in a peculiar manner in SkBr3 cancer cells and CAFs, while miR-338-3p displayed a similar regulation in both cell types. By METABRIC database analysis we ascertained that miR-338-3p positively correlates with overall survival in breast cancer patients, according to previous studies showing that miR-338-3p may suppress the growth and invasion of different cancer cells. Well-fitting with these data, a miR-338-3p mimic sequence decreased and a miR-338-3p inhibitor sequence rescued the expression of genes and the proliferative effects induced by E2 through GPER in SkBr3 cancer cells and CAFs. Altogether, our results provide novel evidence on the molecular mechanisms by which E2 may regulate miR-338-3p toward breast cancer progression.

Activation of GPER suppresses the malignancy of osteosarcoma cells via down regulation of IL-6 and IL-8

Estrogenic signals can regulate the progression of osteosarcoma (OS) via classic estrogen receptor α/β (ERα/β). G protein-coupled estrogen receptor (GPER) can mediate the non-genomic effects of estrogen and regulate the progression of various cancers. Our present study revealed that the expression of GPER in OS cells and tissues was lower than that in their corresponding controls. Activation of GPER via its specific agonist G-1 can decrease the proliferation, migration, and invasion of OS cells. By screening the expression of cytokines involved in the progression of OS, we found that activation of GPER can inhibit the expression of interleukin-6 (IL-6) and IL-8 in OS cells. Recombinant IL-6 (rIL-6) or rIL-8 can attenuate G-1 suppressed migration of OS cells. Mechanically, activation of GPER can rapidly decease the phosphorylation and nuclear translocation of NF-κB in OS cells. While over expression of p65 significantly attenuated G-1 induced down regulation of IL-6/IL-8. Further, G-1 can decrease the activation of p38-MAPK, which can further shorten the half-life of IL-8 mRNA. Collectively, we revealed that GPER can suppress the migration and invasion of OS cells via inhibition of IL-6 and IL-8. It suggested that GPER might be a potential therapy target for OS treatment.

Intracellular GPCRs Play Key Roles in Synaptic Plasticity

The trillions of synaptic connections within the human brain are shaped by experience and neuronal activity, both of which underlie synaptic plasticity and ultimately learning and memory. G protein-coupled receptors (GPCRs) play key roles in synaptic plasticity by strengthening or weakening synapses and/or shaping dendritic spines. While most studies of synaptic plasticity have focused on cell surface receptors and their downstream signaling partners, emerging data point to a critical new role for the very same receptors to signal from inside the cell. Intracellular receptors have been localized to the nucleus, endoplasmic reticulum, lysosome, and mitochondria. From these intracellular positions, such receptors may couple to different signaling systems, display unique desensitization patterns, and/or show distinct patterns of subcellular distribution. Intracellular GPCRs can be activated at the cell surface, endocytosed, and transported to an intracellular site or simply activated in situ by de novo ligand synthesis, diffusion of permeable ligands, or active transport of non-permeable ligands. Current findings reinforce the notion that intracellular GPCRs play a dynamic role in synaptic plasticity and learning and memory. As new intracellular GPCR roles are defined, the need to selectively tailor agonists and/or antagonists to both intracellular and cell surface receptors may lead to the development of more effective therapeutic tools.

Cholesterol and Its Metabolites in Tumor Growth: Therapeutic Potential of Statins in Cancer Treatment

Cholesterol is essential for cell function and viability. It is a component of the plasma membrane and lipid rafts and is a precursor for bile acids, steroid hormones, and Vitamin D. As a ligand for estrogen-related receptor alpha (ESRRA), cholesterol becomes a signaling molecule. Furthermore, cholesterol-derived oxysterols activate liver X receptors (LXRs) or estrogen receptors (ERs). Several studies performed in cancer cells reveal that cholesterol synthesis is enhanced compared to normal cells. Additionally, high serum cholesterol levels are associated with increased risk for many cancers, but thus far, clinical trials with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) have had mixed results. Statins inhibit cholesterol synthesis within cells through the inhibition of HMG-CoA reductase, the rate-limiting enzyme in the mevalonate and cholesterol synthetic pathway. Many downstream products of mevalonate have a role in cell proliferation, since they are required for maintenance of membrane integrity; signaling, as some proteins to be active must undergo prenylation; protein synthesis, as isopentenyladenine is an essential substrate for the modification of certain tRNAs; and cell-cycle progression. In this review starting from recent acquired findings on the role that cholesterol and its metabolites fulfill in the contest of cancer cells, we discuss the results of studies focused to investigate the use of statins in order to prevent cancer growth and metastasis.