Recent Advances on the Role of G Protein-Coupled Receptors in Hypoxia-Mediated Signaling

Effects of free fatty acid receptor (FFAR) signaling on the modulation of cancer cell functions under hypoxic conditions

In the tumor environment, hypoxia promotes tumor progression, such as cancer cell growth, migration and chemoresistance. This study aimed to evaluate the roles of free fatty acid receptors (FFARs) in the regulation of cancer cell functions under hypoxic conditions, using fibrosarcoma HT1080 cells. HT1080 cells expressed FFAR1, FFAR2 and FFAR3 genes, but not FFAR4 gene. FFAR1, FFAR2 and FFAR3 expression levels in HT1080 cells cultured at 1 % O2 were elevated, compared with 21 % O2. The cell growth activities of HT1080 cells cultured at 21 % O2 were inhibited by acetic acid (AA) and propanoic acid (PA), but not 1 % O2. HT1080 cell motility was markedly reduced by culturing at 1 % O2. The cell growth and motility of HT1080 cells were enhanced by FFAR2 knockdown. The cell viability to cisplatin (CDDP) of HT1080 cells cultured at 1 % O2 was increased, compared with 21 % O2. FFAR2 knockdown suppressed the cell viability to CDDP of HT1080 cells. On the other hand, the cell motility and viability to CDDP of HT1080 cells cultured at 21 % O2 were suppressed by TUG-770. When HT1080 cells were cultured at 1 % O2, the cell motility and viability to CDDP were decreased, correlating with FFAR1 expression level. Moreover, FFAR1 knockdown increased the cell viability to CDDP of HT1080 cells cultured at 1 % O2. These results suggest that FFAR-mediated signaling plays an important role in the modulation of cellular functions of HT1080 cells under hypoxic conditions.

Positive correlation between the nuclear expression of GPER and pGLI3 in prostate cancer tissues from patients with different Gleason scores

Prostate cancer (PCa) is the most prevalent cause of death in the male population worldwide. The G Protein-Coupled Estrogen Receptor (GPER) has been gaining relevance in the development of PCa. Hedgehog (Hh) pathway activation is associated with aggressiveness, metastasis, and relapse in PCa patients. To date, no studies have evaluated the crosstalk between the GPER and the Hh pathway along different group grades in PCa. We conducted an analysis of paraffin-embedded tissues derived from patients with different prognostic grade of PCa using immunohistochemistry. Expression and correlation between GPER and glioma associated oncogene homologue (GLI) transcriptional factors in the parenchyma and stroma of PCa tumors were evaluated. Our results indicate that GPER is highly expressed in the nucleus and increases with higher grade groups. Additionally, GPER's expression correlates with pGLI3 nuclear expression across different grade groups in PCa tissues; however, whether the receptor induces the activation of GLI transcriptional factors, or the latter modulate the expression of GPER is yet to be discovered, as well as the functional consequence of this correlation.

GPER: An Estrogen Receptor Key in Metastasis and Tumoral Microenvironments

Estrogens and their role in cancer are well-studied, and some cancer types are classified in terms of their response to them. In recent years, a G protein-coupled estrogen receptor (GPER) has been described with relevance in cancer. GPER is a pleiotropic receptor with tissue-specific activity; in normal tissues, its activation is related to correct development and homeostasis, while in cancer cells, it can be pro- or anti-tumorigenic. Also, GPER replaces estrogen responsiveness in estrogen receptor alpha (ERα)-lacking cancer cell lines. One of the most outstanding activities of GPER is its role in epithelial-mesenchymal transition (EMT), which is relevant for metastasis development. In addition, the presence of this receptor in tumor microenvironment cells contributes to the phenotypic plasticity required for the dissemination and maintenance of tumors. These characteristics suggest that GPER could be a promising therapeutic target for regulating cancer development. This review focuses on the role of GPER in EMT in tumorigenic and associated cells, highlighting its role in relation to the main hallmarks of cancer and possible therapeutic options.

Obesity as a Risk Factor for Breast Cancer-The Role of miRNA

Breast cancer (BC) is the most common cancer diagnosed among women in the world, with an ever-increasing incidence rate. Due to the dynamic increase in the occurrence of risk factors, including obesity and related metabolic disorders, the search for new regulatory mechanisms is necessary. This will help a complete understanding of the pathogenesis of breast cancer. The review presents the mechanisms of obesity as a factor that increases the risk of developing breast cancer and that even initiates the cancer process in the female population. The mechanisms presented in the paper relate to the inflammatory process resulting from current or progressive obesity leading to cell metabolism disorders and disturbed hormonal metabolism. All these processes are widely regulated by the action of microRNAs (miRNAs), which may constitute potential biomarkers influencing the pathogenesis of breast cancer and may be a promising target of anti-cancer therapies.

Differential Expression of Hypoxia-Related Genes in Primary Brain Tumors and Correlation with Clinicopathologic Data

OBJECTIVE

Meningiomas and gliomas are common benign and malignant primary brain tumors, respectively. One of the most prominent features of aggressive malignancies contributing to their progression is their ability to cope with hypoxia. Therefore, glioma tumors are expected to better cope with adverse hypoxic conditions and, consequently, display significantly different expression levels of hypoxia-adaptive genes.

METHODS

Thirty-three glioma (17 glioblastoma multiforme [GBM], 16 low-grade glioma [LGG]) and 32 meningioma samples were investigated for expression of hypoxia adaptation- related genes by real-time polymerase chain reaction. The same investigation was carried out for GBM, the most malignant form of glioma, versus LGG. The findings were further checked by bioinformatics analysis of expression levels using RNA-seq data. Additional investigations conducted include receiver operating characteristic curve analysis to assess the power for each gene in differential diagnosis of glioma from meningioma.

RESULTS

A greater level of hypoxia-inducible factor (HIF) 1α expression in glioma samples compared with meningioma and greater expression levels of Yes-associated protein (YAP) 1 and G-protein-coupled receptor class C group 5 member A (GPRC5A) in meningioma were observed, with P values 0.0005, <0.0001, and <0.0001 for GPRC5A, HIF1α, and YAP1, respectively. Comparison of GBM with LGG also revealed GPRC5A to have significantly greater expression in GBM with P = 0.0381. The calculated area under the curve was 0.7536, 0.8438, and 0.8272 for GPRC5A, HIF1α, and YAP1, respectively, which represented acceptable power for these genes in differential diagnosis of glioma tumor types from meningioma and tumor subtypes GBM from LGG under study.

CONCLUSIONS

These results imply that these genes can possibly be implicated in brain tumor hypoxia-adaptation response with tumor-specific roles and patterns of expression.

Estrogens and Progestogens in Triple Negative Breast Cancer: Do They Harm?

Triple-negative breast cancers (TNBC) occur more frequently in younger women and do not express estrogen receptor (ER) nor progesterone receptor (PR), and are therefore often considered hormone-insensitive. Treatment of premenopausal TNBC patients almost always includes chemotherapy, which may lead to premature ovarian insufficiency (POI) and can severely impact quality of life. Hormone replacement therapy (HRT) is contraindicated for patients with a history of hormone-sensitive breast cancer, but the data on safety for TNBC patients is inconclusive, with a few randomized trials showing increased risk-ratios with wide confidence intervals for recurrence after HRT. Here, we review the literature on alternative pathways from the classical ER/PR. We find that for both estrogens and progestogens, potential alternatives exist for exerting their effects on TNBC, ranging from receptor conversion, to alternative receptors capable of binding estrogens, as well as paracrine pathways, such as RANK/RANKL, which can cause progestogens to indirectly stimulate growth and metastasis of TNBC. Finally, HRT may also influence other hormones, such as androgens, and their effects on TNBCs expressing androgen receptors (AR). Concluding, the assumption that TNBC is completely hormone-insensitive is incorrect. However, the direction of the effects of the alternative pathways is not always clear, and will need to be investigated further.

GPER1 and microRNA: Two Players in Breast Cancer Progression

Breast cancer is the main cause of morbidity and mortality in women worldwide. However, the molecular pathogenesis of breast cancer remains poorly defined due to its heterogeneity. Several studies have reported that G Protein-Coupled Estrogen Receptor 1 (GPER1) plays a crucial role in breast cancer progression, by binding to estrogens or synthetic agonists, like G-1, thus modulating genes involved in diverse biological events, such as cell proliferation, migration, apoptosis, and metastasis. In addition, it has been established that the dysregulation of short sequences of non-coding RNA, named microRNAs (miRNAs), is involved in various pathophysiological conditions, including breast cancer. Recent evidence has indicated that estrogens may regulate miRNA expression and therefore modulate the levels of their target genes, not only through the classical estrogen receptors (ERs), but also activating GPER1 signalling, hence suggesting an alternative molecular pathway involved in breast tumor progression. Here, the current knowledge about GPER1 and miRNA action in breast cancer is recapitulated, reporting recent evidence on the liaison of these two players in triggering breast tumorogenic effects. Elucidating the role of GPER1 and miRNAs in breast cancer might provide new tools for innovative approaches in anti-cancer therapy.

The IL1β-IL1R signaling is involved in the stimulatory effects triggered by hypoxia in breast cancer cells and cancer-associated fibroblasts (CAFs)

Background

Hypoxia plays a relevant role in tumor-related inflammation toward the metastatic spread and cancer aggressiveness. The pro-inflammatory cytokine interleukin-1β (IL-β) and its cognate receptor IL1R1 contribute to the initiation and progression of breast cancer determining pro-tumorigenic inflammatory responses. The transcriptional target of the hypoxia inducible factor-1α (HIF-1α) namely the G protein estrogen receptor (GPER) mediates a feedforward loop coupling IL-1β induction by breast cancer-associated fibroblasts (CAFs) to IL1R1 expression by breast cancer cells toward the regulation of target genes and relevant biological responses.

Methods

In order to ascertain the correlation of IL-β with HIF-1α and further hypoxia-related genes in triple-negative breast cancer (TNBC) patients, a bioinformatics analysis was performed 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, statistical analysis and gene set enrichment analysis (GSEA) were carried out with R studio packages. Pathway enrichment analysis was evaluated with Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway. TNBC cells and primary CAFs were used as model system. The molecular mechanisms implicated in the regulation of IL-1β by hypoxia toward a metastatic gene expression profile and invasive properties were assessed performing gene and protein expression studies, PCR arrays, gene silencing and immunofluorescence analysis, co-immunoprecipitation and ChiP assays, ELISA, cell spreading, invasion and spheroid formation.

Results

We first determined that IL-1β expression correlates with the levels of HIF-1α as well as with a hypoxia-related gene signature in TNBC patients. Next, we demonstrated that hypoxia triggers a functional liaison among HIF-1α, GPER and the IL-1β/IL1R1 signaling toward a metastatic gene signature and a feed-forward loop of IL-1β that leads to proliferative and invasive responses in TNBC cells. Furthermore, we found that the IL-1β released in the conditioned medium of TNBC cells exposed to hypoxic conditions promotes an invasive phenotype of CAFs.

Conclusions

Our data shed new light on the role of hypoxia in the activation of the IL-1β/IL1R1 signaling, which in turn triggers aggressive features in both TNBC cells and CAFs. Hence, our findings provide novel evidence regarding the mechanisms through which the hypoxic tumor microenvironment may contribute to breast cancer progression and suggest further targets useful in more comprehensive therapeutic strategies.

Cancer associated fibroblasts: role in breast cancer and potential as therapeutic targets

Introduction: Cancer associated fibroblasts (CAFs) are the largest population of stromal cells in breast tumors. Emerging evidence has suggested that CAFs are important players not only in fostering tumor growth and spread but also in altering the tumor response to therapeutic agents. On the basis of these observations, huge efforts have been made to exploit CAFs as potential targets for breast cancer therapy.Areas covered: The current understanding of the hallmarks and biology of CAFs, their multilayered interplay with various cell populations of breast tumor microenvironment toward cancer initiation, progression, metastasis and resistance to anticancer therapies are discussed. In addition, a comprehensive overview of the CAFs-based molecular druggable targets in breast tumors is provided. The most relevant literature, in particular the studies retrieved in Medline in the last 10 years, served for this purpose.Expert opinion: The interest on CAFs as a target to fight breast cancer has becoming a hot topic for drug discovery. Indeed, several CAFs-targeted approaches are emerging as appealing therapeutic strategies in breast cancer. At pre-clinical level, this research field is speedily advancing toward the assessment of successful tactics targeting CAFs in breast cancer. Therefore, anti-CAFs therapies may display an intriguing potential to be exploited in clinical studies.

Effects of Post-translational Modifications on Membrane Localization and Signaling of Prostanoid GPCR-G Protein Complexes and the Role of Hypoxia

G protein-coupled receptors (GPCRs) play a pivotal role in the adaptive responses to cellular stresses such as hypoxia. In addition to influencing cellular gene expression profiles, hypoxic microenvironments can perturb membrane protein localization, altering GPCR effector scaffolding and altering downstream signaling. Studies using proteomics approaches have revealed significant regulation of GPCR and G proteins by their state of post-translational modification. The aim of this review is to examine the effects of post-translational modifications on membrane localization and signaling of GPCR-G protein complexes, with an emphasis on vascular prostanoid receptors, and to highlight what is known about the effect of cellular hypoxia on these mechanisms. Understanding post-translational modifications of protein targets will help to define GPCR targets in treatment of disease, and to inform research into mechanisms of hypoxic cellular responses.

Non-canonical Estrogen Signaling in Endocrine Resistance

Breast cancer is one of the leading causes of cancer related deaths in women worldwide. The disease is extremely heterogenous. A large percentage of the breast cancers are dependent on estrogen signaling and hence respond to endocrine therapies which essentially block the estrogen signaling. However, many of these tumors emerge as endocrine resistant tumors. Many mechanisms have been proposed to explain the emergence of endocrine resistance, which include mutations in the estrogen receptors, cross-talk with other signaling pathways, cancer stem cells etc. This review is focused on the role of non-canonical estrogen receptor signaling in endocrine resistance. Most of the therapeutics which are used currently are targeting the major receptor of estrogen namely ER-α. Last two decades has witnessed the discovery of alternate forms of ER-α, as well as other receptors for estrogen such as ERRgamma, GPER-1 as well as ER-β, which are activated not only by estrogen, but also by the therapeutic agents such as tamoxifen that are routinely used in treatment of breast cancer. However, when the alternate receptors are activated, they result in activation of membrane signaling which subsequently activates pathways such as MAPK and GPCR leading to cell-proliferation. This renders the anticipated anti-estrogenic effects of tamoxifen less effective or ineffective. Future research in this area has to focus on the alternate mechanisms and develop a combinatorial strategy, which can complement the existing therapeutics to get better outcome of endocrine therapies.

Characterization of GPCR signaling in hypoxia

G protein-coupled receptors (GPCRs) signal in response to various external stimuli including stress. GPCR signaling has been shown to play a critical role in the adaptation of cell response to limited oxygen supply. Hypoxia has been implicated in cardiovascular diseases, human pulmonary arterial responses, and persistent pulmonary hypertension in newborns. One of the key GPCRs implicated in hypoxia is the prostanoid receptor, thromboxane A2 receptor (TP). Hypoxia can affect TP localization, stability, and activity both in vivo and in vitro. To elucidate hypoxia-mediated GPCR signaling in vitro, we lay out a general strategy to perform hypoxic experiments using both primary pulmonary artery smooth muscle cells and TP expressed in HEK293T cells. We describe assay for measuring moderate tissue hypoxia using static cell cultures, monitoring pericellular media oxygen content, and signaling of TP.

Gpr97 Exacerbates AKI by Mediating Sema3A Signaling

Background G protein-coupled receptors (GPCRs) participate in a variety of physiologic functions, and several GPCRs have critical physiologic and pathophysiologic roles in the regulation of renal function. We investigated the role of Gpr97, a newly identified member of the adhesion GPCR family, in AKI.Methods AKI was induced by ischemia-reperfusion or cisplatin treatment in Gpr97-deficient mice. We assessed renal injury in these models and in patients with acute tubular necrosis by histologic examination, and we conducted microarray analysis and in vitro assays to determine the molecular mechanisms of Gpr97 function.Results Gpr97 was upregulated in the kidneys from mice with AKI and patients with biopsy-proven acute tubular necrosis compared with healthy controls. In AKI models, Gpr97-deficient mice had significantly less renal injury and inflammation than wild-type mice. Gpr97 deficiency also attenuated the AKI-induced expression of semaphorin 3A (Sema3A), a potential early diagnostic biomarker of renal injury. In NRK-52E cells subjected to oxygen-glucose deprivation, siRNA-mediated knockdown of Gpr97 further increased the expression of survivin and phosphorylated STAT3 and reduced toll-like receptor 4 expression. Cotreatment with recombinant murine Sema3A protein counteracted these effects. Finally, additional in vivo and in vitro studies, including electrophoretic mobility shift assays and luciferase reporter assays, showed that Gpr97 deficiency attenuates ischemia-reperfusion-induced expression of the RNA-binding protein human antigen R, which post-transcriptionally regulates Sema3A expression.Conclusions Gpr97 is an important mediator of AKI, and pharmacologic targeting of Gpr97-mediated Sema3A signaling at multiple levels may provide a novel approach for the treatment of AKI.

G Protein-Coupled Receptors at the Crossroad between Physiologic and Pathologic Angiogenesis: Old Paradigms and Emerging Concepts

G protein-coupled receptors (GPCRs) have been implicated in transmitting signals across the extra- and intra-cellular compartments, thus allowing environmental stimuli to elicit critical biological responses. As GPCRs can be activated by an extensive range of factors including hormones, neurotransmitters, phospholipids and other stimuli, their involvement in a plethora of physiological functions is not surprising. Aberrant GPCR signaling has been regarded as a major contributor to diverse pathologic conditions, such as inflammatory, cardiovascular and neoplastic diseases. In this regard, solid tumors have been demonstrated to activate an angiogenic program that relies on GPCR action to support cancer growth and metastatic dissemination. Therefore, the manipulation of aberrant GPCR signaling could represent a promising target in anticancer therapy. Here, we highlight the GPCR-mediated angiogenic function focusing on the molecular mechanisms and transduction effectors driving the patho-physiological vasculogenesis. Specifically, we describe evidence for the role of heptahelic receptors and associated G proteins in promoting angiogenic responses in pathologic conditions, especially tumor angiogenesis and progression. Likewise, we discuss opportunities to manipulate aberrant GPCR-mediated angiogenic signaling for therapeutic benefit using innovative GPCR-targeted and patient-tailored pharmacological strategies.

GPER mediates the angiocrine actions induced by IGF1 through the HIF-1α/VEGF pathway in the breast tumor microenvironment

BACKGROUND

The G protein estrogen receptor GPER/GPR30 mediates estrogen action in breast cancer cells as well as in breast cancer-associated fibroblasts (CAFs), which are key components of microenvironment driving tumor progression. GPER is a transcriptional target of hypoxia inducible factor 1 alpha (HIF-1α) and activates VEGF expression and angiogenesis in hypoxic breast tumor microenvironment. Furthermore, IGF1/IGF1R signaling, which has angiogenic effects, has been shown to activate GPER in breast cancer cells.

METHODS

We analyzed gene expression data from published studies representing almost 5000 breast cancer patients to investigate whether GPER and IGF1 signaling establish an angiocrine gene signature in breast cancer patients. Next, we used GPER-positive but estrogen receptor (ER)-negative primary CAF cells derived from patient breast tumours and SKBR3 breast cancer cells to investigate the role of GPER in the regulation of VEGF expression and angiogenesis triggered by IGF1. We performed gene expression and promoter studies, western blotting and immunofluorescence analysis, gene silencing strategies and endothelial tube formation assays to evaluate the involvement of the HIF-1α/GPER/VEGF signaling in the biological responses to IGF1.

RESULTS

We first determined that GPER is co-expressed with IGF1R and with the vessel marker CD34 in human breast tumors (n = 4972). Next, we determined that IGF1/IGF1R signaling engages the ERK1/2 and AKT transduction pathways to induce the expression of HIF-1α and its targets GPER and VEGF. We found that a functional cooperation between HIF-1α and GPER is essential for the transcriptional activation of VEGF induced by IGF1. Finally, using conditioned medium from CAFs and SKBR3 cells stimulated with IGF1, we established that HIF-1α and GPER are both required for VEGF-induced human vascular endothelial cell tube formation.

CONCLUSIONS

These findings shed new light on the essential role played by GPER in IGF1/IGF1R signaling that induces breast tumor angiogenesis. Targeting the multifaceted interactions between cancer cells and tumor microenvironment involving both GPCRs and growth factor receptors has potential in future combination anticancer therapies.

Bisphenol A induces proliferative effects on both breast cancer cells and vascular endothelial cells through a shared GPER-dependent pathway in hypoxia

Based on the breast cancer cells and the vascular endothelial cells are both estrogen-sensitive, we proposed a close reciprocity existed between them in the tumor microenvironment, via shared molecular mechanism affected by environmental endocrine disruptors (EDCs). In this study, bisphenol A (BPA), via triggering G-protein estrogen receptor (GPER), stimulated cell proliferation and migration of bovine vascular endothelial cells (BVECs) and breast cancer cells (SkBr-3 and MDA-MB-231) and enhanced tumor growth in vivo. Moreover, the expression of both hypoxia inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF) were up-regulated in a GPER-dependent manner by BPA treatment under hypoxic condition, and the activated GPER induced the HIF-1α expression by competitively binding to caveolin-1 (Cav-1) and facilitating the release of heat shock protein 90 (HSP90). These findings show that in a hypoxic microenvironment, BPA promotes HIF-1α and VEGF expressions through a shared GPER/Cav-1/HSP90 signaling cascade. Our observations provide a probable hypothesis that the effects of BPA on tumor development are copromoting relevant biological responses in both vascular endothelial and breast cancer cells.

GPER-1/GPR30 a novel estrogen receptor sited in the cell membrane: therapeutic coupling to breast cancer

INTRODUCTION

Breast cancer is clinically classified as 'estrogen-positive' when at least 1% of cancer cells stain for the estrogen receptor alpha (ERα). However, recent research on both basic and clinical aspects of breast cancer suggests that GPER-1 (G protein-coupled estrogen receptor-1) may have an important role in breast cancer. Areas covered: This review provides a comprehensive and systematic literature search on GPER-1. We have focused on the role of GPER-1 in breast cancer and on resistance to endocrine therapy, an unsolved clinical issue still under discussion. Expert opinion: The discovery of GPER-1 as a novel estrogen receptor is unique and the signaling pathways activated by its stimulation, when compared to the classical nuclear ERα, indicate a potential role of GPER-1 in the genesis and mechanisms of drug resistance in breast cancer. Tumors expressing ERα represent the largest group of breast cancer patients indicating that more women eventually die from ERα-positive breast tumors than from other more malignant breast cancer subtypes such as HER2-positive and the triple negative groups. It is important to develop new strategies on endocrine therapy with regard to ERα and GPER-1 receptors to achieve innovative successful therapeutic tools.

The Glycolytic Enzyme PFKFB3 Is Involved in Estrogen-Mediated Angiogenesis via GPER1

The endogenous estrogen 17β-estradiol (E2) is a key factor in promoting endothelial healing and angiogenesis. Recently, proangiogenic signals including vascular endothelial growth factor and others have been shown to converge in endothelial cell metabolism. Because inhibition of the glycolytic enzyme activator phosphofructokinase-2/fructose-2,6-bisphosphatase 3 (PFKFB3) reduces pathologic angiogenesis and estrogen receptor (ER) signaling stimulates glucose uptake and glycolysis by inducing PFKFB3 in breast cancer, we hypothesized that E2 triggers angiogenesis in endothelial cells via rapid ER signaling that requires PFKFB3 as a downstream effector. We report that treatment with the selective G protein-coupled estrogen receptor (GPER1) agonist G-1 (10-10 to 10-7 M) mimicked the chemotactic and proangiogenic effect of E2 as measured in a number of short-term angiogenesis assays in human umbilical vein endothelial cells (HUVECs); in addition, E2 treatment upregulated PFKFB3 expression in a time- and concentration-dependent manner. Such an effect peaked at 3 hours and was also induced by G-1 and abolished by pretreatment with the GPER1 antagonist G-15 or GPER1 siRNA, consistent with engagement of membrane ER. Experiments with the PFKFB3 inhibitor 3-(3-pyridinyl)-1-(4-pyridinyl)-2-propen-1-one showed that PFKFB3 activity was required for estrogen-mediated HUVEC migration via GPER1. In conclusion, E2-induced angiogenesis was mediated at least in part by the membrane GPER1 and required upregulation of the glycolytic activator PFKFB3 in HUVECs. These findings unravel a previously unrecognized mechanism of estrogen-dependent endocrine-metabolic crosstalk in HUVECs and may have implications in angiogenesis occurring in ischemic or hypoxic tissues.

GPER-novel membrane oestrogen receptor

The recent discovery of the G protein-coupled oestrogen receptor (GPER) presents new challenges and opportunities for understanding the physiology, pathophysiology and pharmacology of many diseases. This review will focus on the expression and function of GPER in hypertension, kidney disease, atherosclerosis, vascular remodelling, heart failure, reproduction, metabolic disorders, cancer, environmental health and menopause. Furthermore, this review will highlight the potential of GPER as a therapeutic target.