The G-protein coupled estrogen receptor (GPER/GPR30) is a gonadotropin receptor dependent positive prognosticator in ovarian carcinoma patients

Exploring the physiological role of the G protein-coupled estrogen receptor (GPER) and its associations with human diseases

Estrogen is a group of hormones that collaborate with the nervous system to impact the overall well-being of all genders. It influences many processes, including those occurring in the central nervous system, affecting learning and memory, and playing roles in neurodegenerative diseases and mental disorders. The hormone's action is mediated by specific receptors. Significant roles of classical estrogen receptors, ERα and ERβ, in various diseases were known since many years, but after identifying a structurally and locationally distinct receptor, the G protein-coupled estrogen receptor (GPER), its role in human physiology and pathophysiology was investigated. This review compiles GPER-related information, highlighting its impact on homeostasis and diseases, while putting special attention on functions and dysfunctions of this receptor in neurobiology and biobehavioral processes. Understanding the receptor modulation possibilities is essential for therapy, as disruptions in receptors can lead to diseases or disorders, irrespective of correct estrogen levels. We conclude that studies on the GPER receptor have the potential to develop therapies that regulate estrogen and positively impact human health.

Synchronous profiling of mRNA N6-methyladenosine modifications and mRNA expression in high-grade serous ovarian cancer: a pilot study

This study aimed to synchronously determine epitranscriptome-wide RNA N6-methyladenosine (m6A) modifications and mRNA expression profile in high grade serous ovarian cancer (HGSOC). The methylated RNA immunoprecipitation sequencing (MeRIP-seq) was used to comprehensively examine the m6A modification profile and the RNA-sequencing (RNA-seq) was performed to analyze the mRNA expression profile in HGSOC and normal fallopian tube (FT) tissues. Go and KEGG analyses were carried out in the enrichment of those differentially methylated and expressed genes. MeRIP-seq data showed 53,794 m6A methylated peaks related to 19,938 genes in the HGSOC group and 51,818 m6A peaks representing 19,681 genes in the FT group. RNA-seq results revealed 2321 upregulated and 2486 downregulated genes in HGSOC. Conjoint analysis of MeRIP-seq and RNA-seq data identified differentially expressed genes in which 659 were hypermethylated (330 up- and 329 down-regulated) and 897 were hypomethylated (475 up- and 422 down-regulated). Functional enrichment analysis indicated that these differentially modulated genes are involved in pathways related to cancer development. Among methylation regulators, the m6A eraser (FTO) expression was significantly lower, but the m6A readers (IGF2BP2 and IGF2BP3) were higher in HGSOC, which was validated by the subsequent real-time PCR assay. Exploration through public databases further corroborated their possible clinical application of certain methylation regulators and differentially expressed genes. For the first time, our study screens the epitranscriptome-wide m6A modification and expression profiles of their modulated genes and signaling pathways in HGSOC. Our findings provide an alternative direction in exploring the molecular mechanisms of ovarian pathogenesis and potential biomarkers in the diagnosis and predicting the prognosis of the disease.

Selective Modulation of the Keratoconic Stromal Microenvironment by FSH and LH

Keratoconus (KC) affects the corneal structure, with thinning and bulging outward into a conelike shape. Irregular astigmatism and decreased visual acuity appear during puberty and progress into the mid-30s, with unpredictable disease severity. The cause of KC is recognized as multifactorial, but remains poorly understood. Hormone imbalances are a significant modulator of the onset of KC. This study sought to investigate the role of gonadotropins, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) in KC, using a three-dimensional, self-assembled matrix in vitro model. Healthy corneal fibroblasts and human KC cells in the corneal stroma were isolated, cultured, and stimulated with stable vitamin C to promote extracellular matrix assembly. Cultures were further stimulated with 2.5 or 10 mIU/mL FSH and 5 or 35 mIU/mL LH. Samples were evaluated for cell proliferation and morphology via BrdU assay and imaging; protein expression was assessed via Western blot analysis. Proliferation was significantly greater in human KC cells compared to healthy corneal fibroblasts with LH stimulation, but no changes were found with FSH stimulation. Additionally, in sex hormone receptors, fibrotic markers, proteoglycans, and members of the gonadotropin signaling pathway were significantly changed, largely driven by exogenous LH. The impact of exogenous FSH/LH in the KC stromal microenvironment was demonstrated. These results highlight the need to further examine the role of FSH/LH in KC and in human corneal homeostasis.

Increase of the T-reg-recruiting chemokine CCL22 expression in a progressive course of cervical dysplasia

PURPOSE

An increasing infiltration of FoxP3-positive T-regs is associated with a higher grade of cervical intraepithelial neoplasia. The T-reg-recruiting chemokine CCL22 is expressed in various tumour entities. Aim of our study was to investigate the role of CCL22 in the progression and regression of cervical intraepithelial neoplasias, especially in patients with intermediate cervical intraepithelial neoplasias (CIN II). Furthermore, our aim was to characterize the CCL22-producing cells and explore the role of innate immunity in the process of cells recruitment.

METHODS

CCL22 expression was analyzed immunohistochemically in 169 patient samples. The immunoreactive score as well as the median numbers of positive cells were calculated in each slide and correlated with the histological CIN grade and FoxP3 expression. Additionally, CD68/CCL22 as well as CD68/PPARγ and CD68/FoxP3 expression were examined by double immunofluorescence. Statistical analysis was performed by SPSS 26.

RESULTS

A significantly higher expression of epithelial CCL22 in CIN II with progression in comparison to CIN II with regression (p = 0.006) could be detected. CCL22 was correlated with FoxP3 (Spearman's Rho: 0.308; p < 0.01). In 88%, CCL22-positive cells were positive for CD68, and 71% of CD68-positive macrophages expressed PPARγ. Colocalization of CD68 and FoxP3 was detected in 12%.

CONCLUSION

We could demonstrate that increased expression of CCL22, mainly produced by macrophages, correlates with elevated potential of malignancy. CCL22 expression could act as a predictor for regression and progression in cervical intraepithelial neoplasia, and it may help in the decision process regarding surgical treatment versus watchful waiting strategy in order to prevent conisation-associated risks. Furthermore, our findings support the potential of CCL22-producing cells as a target for immune therapy in cervical cancer patients.

Nuclear receptor co-repressor NCOR2 and its relation to GPER with prognostic impact in ovarian cancer

PURPOSE

The significance of the non-classical G-protein-coupled estrogen receptor (GPER) as positive or negative prognostic factor for ovarian cancer patients remains still controversial. Recent results indicate that an imbalance of both co-factors and co-repressors of nuclear receptors regulates ovarian carcinogenesis by altering the transcriptional activity through chromatin remodeling. The present study aims to investigate whether the expression of the nuclear co-repressor NCOR2 plays a role in GPER signaling which thereby could positively impact overall survival rates of ovarian cancer patients.

METHODS

NCOR2 expression was evaluated by immunohistochemistry in a cohort of 156 epithelial ovarian cancer (EOC) tumor samples and correlated with GPER expression. The correlation and differences in clinical and histopathological variables as well as their effect on prognosis were analyzed by Spearman's correlation, Kruskal-Wallis test and Kaplan-Meier estimates.

RESULTS

Histologic subtypes were associated with different NCOR2 expression patterns. More specifically, serous and mucinous EOC demonstrated a higher NCOR2 expression (P = 0.008). In addition, high nuclear NCOR2 expression correlated significantly with high GPER expression (cc = 0.245, P = 0.008). A combined evaluation of both high NCOR2 (IRS > 6) and high GPER (IRS > 8) expression revealed an association of a significantly improved overall survival (median OS 50.9 versus 105.1 months, P = 0.048).

CONCLUSION

Our results support the hypothesis that nuclear co-repressors such as NCOR2 may influence the transcription of target genes in EOC such as GPER. Understanding the role of nuclear co-repressors on signaling pathways will allow a better understanding of the factors involved in prognosis and clinical outcome of EOC patients.

Immunohistochemical markers of prognosis in adult granulosa cell tumors of the ovary - a review

BACKGROUND

Granulosa cell tumors (GCT) are rare malignant ovarian tumors. The two subtypes, adult and juvenile granulosa cell tumors, differ in clinical and molecular characteristics. GCT are low-malignant tumors and are generally associated with favorable prognosis. However, relapses are common even years and decades after diagnosis. Prognostic and predictive factors are difficult to assess in this rare tumor entity. The purpose of this review is to provide a comprehensive overview of the current state of knowledge on prognostic markers of GCT to identify patients with a high risk of recurrence.

METHODS

Systematic research for adult ovarian granulosa cell tumors and prognosis revealed n = 409 English full text results from 1965 to 2021. Of these articles, n = 35 were considered for this review after title and abstract screening and topic-specific matching. A specific search for pathologic markers with prognostic relevance for GCT identified n = 19 articles that were added to this review.

RESULTS

FOXL2 mutation and FOXL2 mRNA were inverse and immunohistochemical (IHC) expression of CD56, GATA-4 and SMAD3 was associated with reduced prognosis. IHC analysis of estrogen receptor, Anti-Mullerian hormone (AMH) and inhibin was not associated with prognosis for GCT. Analyses of mitotic rate, Ki-67, p53, β-catenin and HER2 revealed inconsistent results.

Membrane estrogen receptor and follicle-stimulating hormone receptor

Follicle-stimulating hormone (FSH) and estrogens are fundamental to support reproductive functions. Beside the well-known FSH membrane receptor (FSHR), a G protein-coupled estrogen receptor (GPER) has been found, over the last two decades, in several tissues. It may trigger rapid, non-genomic responses of estradiol, activating proliferative and survival stimuli. The two receptors were co-characterized in the ovary, where they modulate different intracellular signaling cascades, according to the expression level and developmental stage of ovarian follicles. Moreover, they may physically interact to form heteromeric assemblies, suggestive of a new mode of action to regulate FSH-specific signals, and likely determining the follicular fate between atresia and dominance. The knowledge of FSH and estrogen membrane receptors provides a new, deeper level of comprehension of human reproduction.

Regulation of the aryl hydrocarbon receptor in cancer and cancer stem cells of gynecological malignancies: An update on signaling pathways

Gynecological malignancies are a female type of cancers that affects the reproductive system. Cancer metastasis or recurrence mediated by cellular invasiveness occurs at advanced stages of cancer progression. Cancer Stem Cells (CSCs) enrichment in tumors leads to chemoresistance, which results in cancer mortality. Exposure to environmental pollutants such as polycyclic aromatic hydrocarbons is associated with an increased the risk of CSC enrichment in gynecological cancers. One of the important pathways that mediates the metabolism and bioactivation of these environmental chemicals is the transcription factor, aryl hydrocarbon receptor (AhR). The present review explores the molecular mechanisms regulating the crosstalk and interaction of the AhR with cancer-related signaling pathways, such as apoptosis, epithelial-mesenchymal transition, immune checkpoints, and G-protein-coupled receptors in several gynecological malignancies such as ovarian, uterine, endometrial, and cervical cancers. The review also discusses the potential of targeting the AhR pathway as a novel chemotherapy for gynecological cancers.

Identification of Potential Active Ingredients and Mechanisms of Cattail Pollen for Treating Infertile Patients With Endometriosis Based on Bioinformatics and Molecular Docking

Introduction: Cattail Pollen is a commonly used Chinese medicine for promoting blood circulation and removing blood stasis in infertility patients with endometriosis, but its ingredients and mechanism of action are still unclear. The aims of this study were to explore the potential active ingredients, targets and mechanisms of Cattail Pollen in treating infertility patients with endometriosis based on bioinformatics and molecular docking. Methods: The GSE120103 dataset was downloaded from the Gene Expression Omnibus (GEO) database to screen out differentially expressed genes. Cytoscape software was constructed to construct the protein–protein interaction network and screen for hub proteins, and molecular docking was performed to identify the binding activity of Cattail Pollen active ingredients and infertility genes. Then, DAVID software was used to perform gene ontology (GO) functional analysis and KEGG pathway enrichment analysis on differentially expressed genes. Results: There were 1320 differentially expressed genes in patients with endometriosis. ADCY5, RLN3, and ADCY6 proteins encoded by genes that were upregulated in infertile patients with endometriosis. Eight active ingredients of Cattail Pollen were obtained from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform: naringenin ((2R)-5,7-dihydroxy-2-(4-hydroxyphenyl)chroman-4-one), arachidonic acid, isorhamnetin, β-sitosterol, kaempferol, Testosterone palmitate, kaempferol-3-O-α-L-rhamnosyl(1→2)-β-D-glucoside and quercetin. Molecular docking identified that the binding activity of arachidonic acid with ADCY5, RLN3, and ADCY6; and testosterone palmitate with ADCY5 and ADCY6 was strong. GO analysis suggested that differentially expressed genes were involved in multiple biological processes, cellular components, and molecular functions. KEGG enrichment analysis found that differentially expressed genes were enriched in neuroactive ligand–receptor interaction, cytokine–cytokine receptor interaction, chemokine signaling pathway, and Jak-STAT signaling pathway. Conclusions: This study discovered the differentially expressed genes of naturally conceived and infertile patients with endometriosis, and clarified the effective ingredients, targets, and potential signaling pathways of Cattail Pollen in the treatment of infertility patients with endometriosis.

Regulation of antral follicular growth by an interplay between gonadotropins and their receptors

Knowledge of the growth and maturation of human antral follicles is based mainly on concepts and deductions from clinical observations and animal models. To date, new experimental approaches and in vitro data contributed to a deep comprehension of gonadotropin receptors' functioning and may provide new insights into the mechanisms regulating still unclear physiological events. Among these, the production of androgen in the absence of proper LH levels, the programming of follicular atresia and dominance are some of the most intriguing. Starting from evolutionary issues at the basis of the gonadotropin receptor signal specificity, we draw a new hypothesis explaining the molecular mechanisms of the antral follicular growth, based on the modulation of endocrine signals by receptor-receptor interactions. The "heteromer hypothesis" explains how opposite death and life signals are delivered by gonadotropin receptors and other membrane partners, mediating steroidogenesis, apoptotic events, and the maturation of the dominant follicle.

Molecular Characterization of Membrane Steroid Receptors in Hormone-Sensitive Cancers

Cancer is one of the most common causes of death worldwide, and its development is a result of the complex interaction of genetic factors, environmental cues, and aging. Hormone-sensitive cancers depend on the action of one or more hormones for their development and progression. Sex steroids and corticosteroids can regulate different physiological functions, including metabolism, growth, and proliferation, through their interaction with specific nuclear receptors, that can transcriptionally regulate target genes via their genomic actions. Therefore, interference with hormones’ activities, e.g., deregulation of their production and downstream pathways or the exposition to exogenous hormone-active substances such as endocrine-disrupting chemicals (EDCs), can affect the regulation of their correlated pathways and trigger the neoplastic transformation. Although nuclear receptors account for most hormone-related biologic effects and their slow genomic responses are well-studied, less-known membrane receptors are emerging for their ability to mediate steroid hormones effects through the activation of rapid non-genomic responses also involved in the development of hormone-sensitive cancers. This review aims to collect pre-clinical and clinical data on these extranuclear receptors not only to draw attention to their emerging role in cancer development and progression but also to highlight their dual role as tumor microenvironment players and potential candidate drug targets.

Trace Amine-Associated Receptor 1 (TAAR1) Is a Positive Prognosticator for Epithelial Ovarian Cancer

Trace amine-associated receptor 1 (TAAR1) is a G_αs- protein coupled receptor that plays an important role in the regulation of the immune system and neurotransmission in the CNS. In ovarian cancer cell lines, stimulation of TAAR1 via 3-iodothyronamine (T₁AM) reduces cell viability and induces cell death and DNA damage. Aim of this study was to evaluate the prognostic value of TAAR1 on overall survival of ovarian carcinoma patients and the correlation of TAAR1 expression with clinical parameters. Ovarian cancer tissue of n = 156 patients who were diagnosed with epithelial ovarian cancer (serous, n = 110 (high-grade, n = 80; low-grade, n = 24; unknown, n = 6); clear cell, n = 12; endometrioid, n = 21; mucinous, n = 13), and who underwent surgery at the Department of Obstetrics and Gynecology, University Hospital of the Ludwig-Maximilians University Munich, Germany between 1990 and 2002, were analyzed. The tissue was stained immunohistochemically with anti-TAAR1 and evaluated with the semiquantitative immunoreactive score (IRS). TAAR1 expression was correlated with grading, FIGO and TNM-classification, and analyzed via the Spearman’s rank correlation coefficient. Further statistical analysis was obtained using nonparametric Kruskal-Wallis rank-sum test and Mann-Whitney-U-test. This study shows that high TAAR1 expression is a positive prognosticator for overall survival in ovarian cancer patients and is significantly enhanced in low-grade serous carcinomas compared to high-grade serous carcinomas. The influence of TAAR1 as a positive prognosticator on overall survival indicates a potential prognostic relevance of signal transduction of thyroid hormone derivatives in epithelial ovarian cancer. Further studies are required to evaluate TAAR1 and its role in the development of ovarian cancer.

The G-Protein-Coupled Estrogen Receptor (GPER) Regulates Trimethylation of Histone H3 at Lysine 4 and Represses Migration and Proliferation of Ovarian Cancer Cells In Vitro

Histone H3 lysine 4 trimethylation (H3K4me3) is one of the most recognized epigenetic regulators of transcriptional activity representing, an epigenetic modification of Histone H3. Previous reports have suggested that the broad H3K4me3 domain can be considered as an epigenetic signature for tumor-suppressor genes in human cells. G-protein-coupled estrogen receptor (GPER), a new membrane-bound estrogen receptor, acts as an inhibitor on cell growth via epigenetic regulation in breast and ovarian cancer cells. This study was conducted to evaluate the relationship of GPER and H3K4me3 in ovarian cancer tissue samples as well as in two different cell lines (Caov3 and Caov4). Silencing of GPER by a specific siRNA and two selective regulators with agonistic (G1) and antagonistic (G15) activity were applied for consecutive in vitro studies to investigate their impacts on tumor cell growth and the changes in phosphorylated ERK1/2 (p-ERK1/2) and H3K4me3. We found a positive correlation between GPER and H3K4me3 expression in ovarian cancer patients. Patients overexpressing GPER as well as H3K4me3 had significantly improved overall survival. Increased H3K4me3 and p-ERK1/2 levels and attenuated cell proliferation and migration were observed in Caov3 and Caov4 cells via activation of GPER by G1. Conversely, antagonizing GPER activity by G15 resulted in opposite effects in the Caov4 cell line. In conclusion, interaction of GPER and H3K4me3 appears to be of prognostic significance for ovarian cancer patients. The results of the in vitro analyses confirm the biological rationale for their interplay and identify GPER agonists, such as G1, as a potential therapeutic approach for future investigations.

G Protein-Coupled Estrogen Receptor Correlates With Dkk2 Expression and Has Prognostic Impact in Ovarian Cancer Patients

PURPOSE

Wnt pathway modulator Dickkopf 2 (Dkk2) and signaling of the G protein-coupled estrogen receptor (GPER) seem to have essential functions in numerous cancer types. For epithelial ovarian cancer (EOC), it has not been proven if either Dkk2 or the GPER on its own have an independent impact on overall survival (OS). So far, the correlation of both factors and their clinical significance has not systematically been investigated before.

METHODS

Expression levels of Dkk2 were immunohistochemically analyzed in 156 patient samples from different histologic subtypes of EOC applying the immune-reactivity score (IRS). Expression analyses were correlated with clinical and pathological parameters to assess for prognostic relevance. Data analysis was performed using Spearman's correlations, Kruskal-Wallis-test and Kaplan-Meier estimates.

RESULTS

Highest Dkk2 expression of all subtypes was observed in clear cell carcinoma. In addition, Dkk2 expression differed significantly (p<0.001) between low and high grade serous ovarian cancer. A significant correlation of Dkk2 with the cytoplasmic GPER expression was noted (p=0.001) but not for the nuclear estrogen receptor alpha (ERα) or beta (ERβ). Patients exhibiting both, high expression Dkk2 (IRS>4) and GPER (IRS>8), had a significantly better overall survival compared to patients with low expression (61 months vs. 33 months; p=0.024).

CONCLUSION

Dkk2 and GPER expression correlates in EOC and combined expression of both is associated with improved OS. These findings underline the clinical significance of both pathways and indicate a possible prognostic impact as well as a potential for treatment strategies addressing interactions between estrogen and Wnt signaling in ovarian cancer.

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 1 (GPER-1) and agonist G-1 inhibit growth of ovarian cancer cells by activation of anti-tumoral transcriptome responses: impact of GPER-1 mRNA on survival

PURPOSE

The present study intended to further elucidate the role of G protein-coupled estrogen receptor 1 (GPER-1) in ovarian cancer by comparing the effects of a GPER-1 knockdown and treatment with its agonist G-1 on cell growth, apoptosis, and the transcriptome of two ovarian cancer cell lines. Furthermore, the role of GPER-1 in ovarian cancer survival was examined.

METHODS

GPER-1 expression in OVCAR-3 and OAW-42 ovarian cancer cells was knocked down by RNAi. The effects on cell growth were measured by means of the fluorimetric cell titer blue assay and on the transcriptome by Affymetrix GeneChip analysis. The effect of GPER-1 on patient's survival was examined using open source mRNA and clinical data of 1657 ovarian cancer patients.

RESULTS

GPER-1 knockdown resulted in a significant growth stimulation of both cell lines, whereas treatment with agonist G-1 decreased growth of both cell lines in a dose-dependent manner. Transcriptome analyses revealed a set of 18 genes being conversely regulated after GPER-1 knockdown and G-1 treatment. Generally, treatment with G-1 led to a transcriptome response associated with growth inhibition. In contrast, knockdown of GPER-1 exerted opposite effects, stimulating pathways activating mitosis, but inhibiting pathways associated with apoptosis or interferon signaling. Further analyses using open-access mRNA and clinical data by bioinformatical online tools revealed a longer OS (HR = 0.86, p = 0.057) and PFS (HR = 0.81, p = 0.0035) of ovarian cancer patients with high GPER-1 mRNA expression.

CONCLUSIONS

The results of this study clearly support the hypothesis that GPER-1 acts as a tumor suppressor in ovarian cancer.

Cytoplasmic versus nuclear THR alpha expression determines survival of ovarian cancer patients

Purpose

Thyroid hormone receptors (THR) have manifold functions and are involved in the carcinogenesis of several tumor types. Within this study, we aimed to investigate the expression pattern (nuclear versus cytoplasmic) of the THR alpha and its impact on patients survival in ovarian cancer (OvCa).

Methods

The presence of the thyroid hormone receptors THRα, THRα1 and − 2 was investigated in 156 ovarian cancer samples using immunohistochemistry (IHC) using semi-quantitative immunoreactivity (IR) scores and correlated with clinical, pathological data, subtype of ovarian cancer, clinical data, staining of 20 already described OvCa marker proteins and overall survival (OS).

Results

Among all subtypes of OvCa, clear cell carcinomas showed the highest THRα expression. Furthermore, nuclear THRα was associated with a reduced survival in this subtype. However, nuclear expressed THRα1 turned out to be a positive prognosticator for all subtypes of OvCa patients. Nuclear THRα2 is a positive prognosticator for OvCa patients of the serous subtype. In contrast, cytoplasmic expression THRα2 was associated with a reduced OS in all subtypes of OvCa patients; while, cytoplasmic expression of THRα1 is associated with reduced OS in mucinous OvCa patients only. In addition, THRα expression correlates with gonadotropin receptors, steroid hormone receptors, TA-MUC1 and glycodelin.

Conclusion

Depending on nuclear or cytoplasmic expression, our study shows that THRα and its isoforms 1 and 2 provide different prognostic information for ovarian cancer patients. Further investigations should analyze if THRs may represent new endocrine targets for the treatment of ovarian cancer.

Electronic supplementary material

The online version of this article (10.1007/s00432-020-03241-7) contains supplementary material, which is available to authorized users.

β-arrestin 2 Is a Prognostic Factor for Survival of Ovarian Cancer Patients Upregulating Cell Proliferation

Establishing reliable prognostic factors as well as specific targets for new therapeutic approaches is an urgent requirement in advanced ovarian cancer. For several tumor entities, the ubiquitously spread scaffold protein β-arrestin 2, a multifunctional scaffold protein regulating signal transduction and internalization of activated G protein-coupled receptors (GPCRs), has been considered with rising interest for carcinogenesis. Therefore, we aimed to elucidate the prognostic impact of β-arrestin 2 and its functional role in ovarian cancer. β-arrestin 2 expression was analyzed in a subset of 156 samples of ovarian cancer patients by immunohistochemistry. Cytoplasmic expression levels were correlated with clinical as well as pathological characteristics and with prognosis. The biologic impact of β-arrestin 2 on cell proliferation and survival was evaluated, in vitro. Following transient transfection by increasing concentrations of plasmid encoding β-arrestin 2, different cell lines were evaluated in cell viability and death. β-arrestin 2 was detected in all histological ovarian cancer subtypes with highest intensity in clear cell histology. High β-arrestin 2 expression levels correlated with high-grade serous histology and the expression of the gonadotropin receptors FSHR and LHCGR, as well as the membrane estrogen receptor GPER and hCGβ. Higher cytoplasmic β-arrestin 2 expression was associated with a significantly impaired prognosis (median 29.88 vs. 50.64 months; P = 0.025). Clinical data were confirmed in transfected HEK293 cells, human immortalized granulosa cell line (hGL5) and the ovarian cancer cell line A2780 in vitro, where the induction of β-arrestin 2 cDNA expression enhanced cell viability, while the depletion of the molecule by siRNA resulted in cell death. Reflecting the role of β-arrestin 2 in modulating GPCR-induced proliferative and anti-apoptotic signals, we propose β-arrestin 2 as an important prognostic factor and also as a promising target for new therapeutic approaches in advanced ovarian cancer.

G Protein-Coupled Receptors (GPCRs)-Mediated Calcium Signaling in Ovarian Cancer: Focus on GPCRs activated by Neurotransmitters and Inflammation-Associated Molecules

G-coupled protein receptors (GCPR) involve several signaling pathways, some of them being coupled with intracellular calcium (Ca²⁺) mobilization. GPCRs were involved in migration, invasion and metastasis of different types of cancers, including ovarian cancer. Many studies have discussed the essential contribution of GPCRs activated by steroid hormones in ovarian cancer. However, ovarian cancer is also associated with altered signals coming from the nervous system, the immune system or the inflammatory environment, in which GPCRs are ‘sensing’ these molecular signals. Many studies have been oriented so far on ovarian cell lines (most of them being of human cell lines), and only few studies based on animal models or clinical studies have been devoted to the expression changes or functional role of GPCRs in ovarian cancer. In this paper, we review the alterations of GPCRs activated by neurotransmitters (muscarinic receptors, serotonin receptors, dopamine receptors, adrenoceptors) or inflammation-associated molecules (bradykinin receptors, histamine receptors, chemokine receptors) in ovarian cancer and we discuss their potential as histological biomarkers.

Role of G Protein-Coupled Estrogen Receptor in Cancer Progression

Cancer is the leading cause of mortality worldwide. In cancer progression, sex hormones and their receptors are thought to be major factors. Many studies have reported the effects of estrogen and estrogen receptors (ERs) in cancer development and progression. Among them, G protein-coupled estrogen receptor (GPER), a G proteincoupled receptor, has been identified as an estrogen membrane receptor unrelated to nuclear ER. The mechanism of GPER, including its biological action, function, and role, has been studied in various cancer types. In this review, we discuss the relation between GPER and estrogen or estrogen agonists/antagonists and cancer progression.

Extracapsular Lymph Node Involvement in Ovarian Carcinoma

Ovarian cancer (OC) spread to retro-peritoneal lymph nodes is detected in about one out of two patients at primary diagnosis. Whether the histologic pattern of lymph node involvement i.e., intra-(ICG) or extracapsular (ECG) cancer growth may affect patients’ prognosis remains unknown. The aim of the current study was to analyze the prevalence of ECG and ICG in lymph node positive ovarian cancer. We further investigated whether ECG may be related to patients’ prognosis and whether biomarkers expressed in the primary tumor may predict the pattern of lymph node involvement. Lymph node samples stemming from 143 OC patients were examined for presence of ECG. Capsular extravasation was tested for statistical association with clinico-pathological variables. We further tested 27 biomarkers that had been determined in primary tumor tissue for their potential to predict ECG in metastatic lymph nodes. ECG was detected in 35 (24.5%) of 143 lymph node positive patients. High grade (p = 0.043), histologic subtype (p = 0.006) and high lymph node ratio (LNR) (p < 0.001) were positively correlated with presence of ECG. Both ECG (p = 0.024) and high LNR (p = 0.008) were predictive for shortened overall survival. A four-protein signature determined from the primary tumor tissue was associated with presence of concomitant extracapsular spread in lymph nodes of the respective patient. This work found extracapsular spread of lymph node metastasis to be a common feature of lymph node positive ovarian cancer. Since ECG was positively associated with grade, LNR and shortened overall survival, we hypothesize that the presence of ECG may be interpreted as an indicator of tumor aggressiveness.

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.

Potential Interplay of the Gatipotuzumab Epitope TA-MUC1 and Estrogen Receptors in Ovarian Cancer

Anti-tumor efficacy of Gatipotuzumab, a therapeutic antibody targeting Tumor-Associated Mucin-1 (TA-MUC1), in relapsed ovarian cancer (OC) appeared to be rather heterogeneous. Whether adding a second anti-neoplastic drug may augment response towards Gatipotuzumab, has not been elucidated so far. Since it is known that anti-MUC1 antibodies may alter estrogen receptor activity in breast cancer, this potential interplay was investigated in OC. The correlation between TA-MUC1, estrogen receptors (ERs) and another 12 protein markers as well as their correlation with clinico-pathological parameters in 138 ovarian cancer cases was studied. Finally, Gatipotuzumab and 4-Hydroxy-TTamoxifen (4-OHT) as well as the combination of both was tested for its impact on cell viability in COV318, OV-90, OVCAR-3, and SKOV-3 cells. A strong positive correlation between TA-MUC1 and ERs was detected in OC tissue. Those cases missing ERs but staining positive for TA-MUC1 had significantly reduced overall survival. The combination of 4-OHT and Gatipotuzumab significantly reduced cell viability and was more effective than treatment with Gatipotuzumab alone. Co-stimulation with Gatipotuzumab enhanced the efficacy of 4-OHT in OVCAR-3 and SKOV-3. The data suggest an interplay of TA-MUC1 and ERs in OC. Whether the combination of Gatipotuzumab and TTamoxifen may enhance efficacy of either of the two drugs in vivo, or may even translate into a clinically relevant benefit over the respective monotherapies, remains to be investigated.

G Protein-Coupled Estrogen Receptor: A Potential Therapeutic Target in Cancer

The G protein-coupled estrogen receptor (GPER) is a seven-transmembrane-domain receptor that mediates non-genomic estrogen related signaling. After ligand activation, GPER triggers multiple downstream pathways that exert diverse biological effects on the regulation of cell growth, migration and programmed cell death in a variety of tissues. A significant correlation between GPER and the progression of multiple cancers has likewise been reported. Therefore, a better understanding of the role GPER plays in cancer biology may lead to the identification of novel therapeutic targets, especially among estrogen-related cancers. Here, we review cell signaling and detail the functions of GPER in malignancies.

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

Mechanisms of carcinogenesis by estrogen center on its mitogenic and genotoxic potential on tumor target cells. These models suggest that estrogen receptor (ER) signaling promotes expansion of the transformed population and that subsequent accumulation of somatic mutations that drive cancer progression occur via metabolic activation of cathecol estrogens or by epigenetic mechanisms. Recent findings that GPER is linked to obesity, vascular pathology and immunosuppression, key events in the development of metabolic syndrome and intra-tissular estrogen synthesis, provides an alternate view of estrogen-induced carcinogenesis. Consistent with this concept, GPER is directly associated with clinicopathological indices that predict cancer progression and poor survival in breast and gynecological cancers. Moreover, GPER manifests cell biological responses and a microenvironment conducive for tumor development and cancer progression, regulating cellular responses associated with glandular homeostasis and survival, invading surrounding tissue and attracting a vascular supply. Thus, the cellular actions attributed to GPER fit well with the known molecular mechanisms of G-protein coupled receptors, GPCRs, namely, their ability to transactivate integrins and EGF receptors and alter the interaction between glandular epithelia and their extracellular environment, affecting epithelial-to-mesenchymal transition (EMT) and allowing for tumor cell survival and dissemination. This perspective reviews the molecular and cellular responses manifested by GPER and evaluates its contribution to female reproductive cancers as diseases that progress as a result of dysregulated glandular homeostasis resulting in chronic inflammation and metastasis. This review is organized in sections as follows: I) a brief synopsis of the current state of knowledge regarding estrogen-induced carcinogenesis, II) a review of evidence from clinical and animal-based studies that support a role for GPER in cancer progression, and III) a mechanistic framework describing how GPER-mediated estrogen action may influence the tumor and its microenvironment.

The G protein-coupled estrogen receptor (GPER/GPR30) may serve as a prognostic marker in early-stage cervical cancer

BACKGROUND

Estrogen signalling is transmitted via various receptors and multiple intracellular signalling pathways. Estrogen receptor alpha (ERα)-mediated transcription of target genes has been demonstrated to be closely linked to human papilloma virus (HPV)-induced carcinogenesis in case of cervical cancer. So far, the role of non-genomic estrogen signals in cervical cancer, e.g. transmitted by the G protein-coupled estrogen receptor (GPER) remains to be rather elusive. Today's knowledge on the role of GPER in cervical cancer is sparse and-to the best of our knowledge-GPER has not been investigated in context with clinicopathological parameters or prognosis of cervical cancer. Therefore, the current study investigated whether GPER is expressed in cervical cancer tissue. Further, GPER was correlated to clinicopathological parameters, tissue markers of cervical carcinogenesis and to patient overall and recurrence-free survival.

MATERIALS AND METHODS

Cervical cancer tissue was collected from 156 patients during surgery between 1993 and 2002. GPER immunostaining was performed on all the cases and correlated to clinicopathological data. More than half of all patients were diagnosed at advanced stage (FIGO II-IV 93/156; 59.6%) of disease. The large majority of patients presented with tumours of intermediate or high grade (G2-3 140/152, 92.1%). 22 cervical cancer-related deaths (22/156, 14.1%) were documented during the follow-up period.

RESULTS

GPER was detected in various subcellular staining patterns. In 129/156 (82.7%) cases GPER was expressed in the tumour cell cytoplasm (GPER^cyt). GPER immunopositivity at the cell membrane (GPER^mem) was found in 114/156 (73.1%) cases. While co-occurrence of both membrane and cytoplasmic staining (GPER^cyt + GPER^mem) was detected in the majority of tissue samples (101/156; 64.7%), only few cases (14/156, 9.0%) were classified as not expressing GPER at all. GPER^cyt was positively correlated with tumour grade. Statistical associations of GPER and both p16 and p53 were detected. Finally, immunopositivity of GPER^cyt was predictive for favourable overall as well as recurrence-free survival in cervical cancer of early stage (FIGO I).

CONCLUSION

This retrospective study reports GPER^cyt to be associated with improved overall and recurrence-free survival in early-stage cervical cancer. Further investigations are needed thus to determine whether this observation may be of clinical impact. Interestingly, Raloxifene-a GPER-activating selective estrogen receptor modulator-has recently been demonstrated to be preventive for cervical cancer relapse in mice. Whether this effect is only reliant on raloxifene blocking ERα or may also be related to activation of GPER remains to be determined.

The Role of Endocrine G Protein-Coupled Receptors in Ovarian Cancer Progression

Ovarian cancer is the seventh most common cancer in women and the most lethal gynecological cancer, causing over 151,000 deaths worldwide each year. Dysregulated production of endocrine hormones, known to have pluripotent effects on cell function through the activation of receptor signaling pathways, is believed to be a high-risk factor for ovarian cancer. An increasing body of evidence suggests that endocrine G protein-coupled receptors (GPCRs) are involved in the progression and metastasis of ovarian neoplasms. GPCRs are attractive drug targets because their activities are regulated by more than 25% of all drugs approved by the Food and Drug Administration. Therefore, understanding the role of endocrine GPCRs during ovarian cancer progression and metastasis will allow for the development of novel strategies to design effective chemotherapeutic drugs against malignant ovarian tumors. In this review, we address the signaling pathways and functional roles of several key endocrine GPCRs that are related to the cause, progression, and metastasis of ovarian cancer.

β-arrestins regulate gonadotropin receptor-mediated cell proliferation and apoptosis by controlling different FSHR or LHCGR intracellular signaling in the hGL5 cell line

Gonadotropin signaling classically involves proliferative, steroidogenic and apoptotic stimuli. In this study, we used the human granulosa cell line hGL5 to demonstrate how follicle-stimulating hormone (FSH) and luteinizing hormone (LH) differently control proliferative or apoptotic signals, revealing novel intrinsic properties of their receptors (FSHR, LHCGR). We found that, in this tumor-like cell line, the expression of endogenous FSHR and LHCGR is serum-dependent, but both receptors were unable to activate the canonical cAMP/PKA pathway upon gonadotropin stimulation, failing to produce cAMP, progesterone and G protein-coupled receptor (GPCR)-mediated apoptosis in vitro. Conversely, ligand treatment resulted in FSHR- and LHCGR-mediated ERK1/2 phosphorylation and cell proliferation due to receptor coupling to β-arrestins. The inactive cAMP/PKA pathway was unlocked by siRNA-mediated knock-down of β-arrestin 1 and 2, leading to progesterone synthesis and apoptosis. Surprisingly, FSH, but not LH treatment accelerated the cAMP/PKA-mediated apoptosis after β-arrestin silencing, an effect which could be reproduced by overexpressing the FSHR, but not the LHCGR. This work demonstrates that the expression of FSHR and LHCGR can be induced in hGL5 cells but that the FSHR-dependent cAMP/PKA pathway is constitutively silenced, possibly to protect cells from FSHR-cAMP-PKA-induced apoptosis. Also, we revealed previously unrecognized features intrinsic to the two structurally similar gonadotropin receptors, oppositely resulting in the regulation of life and death signals in vitro.

Hormone Receptors in Serous Ovarian Carcinoma: Prognosis, Pathogenesis, and Treatment Considerations

A few breakthroughs have been accomplished for the treatment of ovarian cancer, the most deadly gynecologic carcinoma, in the current era of targeted oncologic treatment. The estrogen receptor was the first target of such treatments with the introduction of tamoxifen four decades ago in breast cancer therapeutics. Attempts to duplicate the success of hormonal therapies in ovarian cancer met with mixed results, which may be due to an inferior degree of hormone dependency in this cancer. Alternatively, this may be due to the failure to clearly identify the subsets of ovarian cancer with hormone sensitivity. This article reviews the expression of hormone receptors by ovarian cancer cells, the prognostic value of these expressions, and their predictive capacity for response to hormonal agents. The possible ways ahead are briefly discussed.

p53 determines prognostic significance of the carbohydrate stem cell marker TF1 (CD176) in ovarian cancer

INTRODUCTION

The oncofoetal Thomsen-Friedenreich (TF1, CD176) epitope is a carbohydrate cancer stem cell (CSC) antigen, and TF1-mediated cancer progression can be widely reversed by anti-TF1 antibodies. Particularly, CSC-like cells are regarded to be tumorigenic and chemoresistant. Aberrant p53 is probably the factor most closely associated with chemoresistance and tumour aggressiveness in ovarian tumours. We thus questioned whether TF1 in combination with p53 or as a single marker may be related to clinico-pathological features and survival of ovarian cancer patients.

PATIENTS AND METHODS

Both markers were quantified in ovarian cancer tissue (n = 151) by immunohistochemistry. p53 staining was subdivided into three subgroups [n (completely negative) = 57, n (moderately stained) = 28, n (overexpressing) = 66]. TF1 was scored as positive (n = 30) versus negative (n = 121).

RESULTS

Only in those cancers classified with moderate p53 staining-and thus most likely displaying with wild-type TP53-TF1 positivity turned out to be a predictor for shortened overall survival (univariate: p < 0.001, multivariate: p = 0.001). By screening 17 different protein markers for correlation with TF1, only mucin-1 emerged as a potential TF1 carrier protein.

CONCLUSION

It is hypothesized that TF1 may confer tumour-promoting features, especially in a TP53 wild-type genetic background. In addition, TF1 is an attractive immunotherapeutic target. Whether those cases classified as TF1 positive and at the same time as moderately stained for p53 might particularly benefit from a future anti-TF1 antibody treatment or from TF1 vaccination therapy remains to be determined.

Thyroid Hormone Receptors Predict Prognosis in BRCA1 Associated Breast Cancer in Opposing Ways

Since BRCA1 associated breast cancers are frequently classified as hormone receptor negative or even triple negative, the application of endocrine therapies is rather limited in these patients. Like hormone receptors that bind to estrogen or progesterone, thyroid hormone receptors (TRs) are members of the nuclear hormone receptor superfamily. TRs might be interesting biomarkers - especially in the absence of classical hormone receptors. The current study aimed to investigate whether TRs may be specifically expressed in BRCA1 associated cancer cases and whether they are of prognostic significance in these patients as compared to sporadic breast cancer cases. This study analyzed TRα and TRβ immunopositivity in BRCA1 associated (n = 38) and sporadic breast cancer (n = 86). Further, TRs were studied in MCF7 (BRCA1 wildtype) and HCC3153 (BRCA1 mutated) cells. TRβ positivity rate was significantly higher in BRCA1 associated as compared to sporadic breast cancers (p = 0.001). The latter observation remained to be significant when cases that had been matched for clinicopathological criteria were compared (p = 0.037). Regarding BRCA1 associated breast cancer cases TRβ positivity turned out to be a positive prognostic factor for five-year (p = 0.007) and overall survival (p = 0.026) while TRα positivity predicted reduced five-year survival (p = 0.030). Activation of TRβ resulted in down-modulation of CTNNB1 while TRα inhibition reduced cell viability in HCC3153. However, only BRCA1 wildtype MCF7 cells were capable of rapidly degrading TRα1 in response to T3 stimulation. Significantly, this study identified TRβ to be up-regulated in BRCA1 associated breast cancer and revealed TRs to be associated with patients’ prognosis. TRs were also found to be expressed in triple negative BRCA1 associated breast cancer. Further studies need to be done in order to evaluate whether TRs may become interesting targets of endocrine therapeutic approaches, especially when tumors are triple-negative.

Estrogen biosynthesis and action in ovarian cancer

Ovarian cancer is still the deadliest of all gynecologic malignancies in women worldwide. This is attributed to two main features of these tumors, namely, (i) a diagnosis at an advanced tumor stage, and, (ii) the rapid onset of resistance to standard chemotherapy after an initial successful therapy with platin- and taxol-derivatives. Therefore, novel targets for an early diagnosis and better treatment options for these tumors are urgently needed. Epidemiological data show that induction and biology of ovarian cancer is related to life-time estrogen exposure. Also experimental data reveal that ovarian cancer cells share a number of estrogen regulated pathways with other hormone-dependent cancers, e.g., breast and endometrial cancer. However, ovarian cancer is a heterogeneous disease and the subtypes are quite different with respect to mutations, origins, behaviors, markers, and prognosis and respond differently to standard chemotherapy. Therefore, a characterization of ovarian cancer subtypes may lead to better treatment options for the various subtypes and in particular for the most frequently observed high-grade serous ovarian carcinoma. For this intention, further studies on estrogen-related pathways and estrogen formation in ovarian cancer cells are warranted. The review gives an overview on ovarian cancer subtypes and explains the role of estrogen in ovarian cancer. Furthermore, enzymes active to synthesize and metabolize estrogens are described and strategies to target these pathways are discussed.

Estrogen signaling crosstalk: Implications for endocrine resistance in ovarian cancer

Resistance to anti-estrogen therapies is a prominent challenge in the treatment of ovarian cancer. Tumors develop endocrine resistance by acquiring adaptations that help them rely on alternative oncogenic signaling cascades, which crosstalk with estrogen signaling pathways. An understanding of estrogen signaling crosstalk with these growth promoting cascades is essential in order to maximize efficacy of anti-estrogen treatments in ovarian cancer. Herein, we provide an overview of estrogen signaling in ovarian cancer and discuss the major challenges associated with anti-estrogen therapies. We also review what is currently known about how genomic and non-genomic estrogen signaling pathways crosstalk with several major oncogenic signaling cascades. The insights provided here illustrate existing strategies for targeting endocrine resistant ovarian tumors and may help identify new strategies to improve the treatment of this disease.

The G-protein-coupled estrogen receptor (GPER/GPR30) in ovarian granulosa cell tumors

Ovarian granulosa cell tumors (GCTs) are thought to arise from cells of the ovarian follicle and comprise a rare entity of ovarian masses. We recently identified the G-protein-coupled estrogen receptor (GPER/GPR30) to be present in granulosa cells, to be regulated by gonadotropins in epithelial ovarian cancer and to be differentially expressed throughout folliculogenesis. Thus, supposing a possible role of GPER in GCTs, this study aimed to analyze GPER in GCTs. GPER immunoreactivity in GCTs (n = 26; n (primary diagnosis) = 15, n (recurrence) = 11) was studied and correlated with the main clinicopathological variables. Positive GPER staining was identified in 53.8% (14/26) of GCTs and there was no significant relation of GPER with tumor size or lymph node status. Those cases presenting with strong GPER intensity at primary diagnosis showed a significant reduced overall survival (p = 0.002). Due to the fact that GPER is regulated by estrogens, as well as gonadotropins, GPER may also be affected by endocrine therapies applied to GCT patients. Moreover, with our data supposing GPER to be associated with GCT prognosis, GPER might be considered as a possible confounder when assessing the efficacy of hormone-based therapeutic approaches in GCTs.