Isolation and functional characterization of a novel endogenous inverse agonist of estrogen related receptors (ERRs) from human pregnancy urine

Research Progress in Estrogen-related Receptor Gamma (ERRγ) Agonists and Inverse Agonists

Estrogen-related receptor gamma (ERRγ), one of three members of the ERR family, is an inducible transcription factor. ERRγ has dual functions in different tissues. The decreased expression of ERRγ in the brain, stomach, prostate, and fat cells can cause neuropsychological dysfunction, gastric cancer, prostate cancer, and obesity. However, when ERRγ is present in the liver, pancreas, and thyroid follicular cells, ERRγ overexpression is related to liver cancer, type II diabetes, oxidative liver injury, and anaplastic thyroid carcinoma. Signaling pathway studies have confirmed that ERRγ agonists or inverse agonists can regulate ERRγ expression to treat related diseases. The collision between residue Phe435 and the modulator is a key factor determining the activation or inhibition of ERRγ. Although more than 20 agonists and inverse agonists of ERRγ have been reported, no clinical studies have been found in the literature. This review summarizes the important relationship between ERRγ-related signaling pathways and diseases, research progress, and the structure-activity relationship of modulators. These findings provide guidance for further study on new ERRγ modulators.

The Role of the Estrogen-Related Receptor Alpha (ERRa) in Hypoxia and Its Implications for Cancer Metabolism

Under low oxygen conditions (hypoxia), cells activate survival mechanisms including metabolic changes and angiogenesis, which are regulated by HIF-1. The estrogen-related receptor alpha (ERRα) is a transcription factor with important roles in the regulation of cellular metabolism that is overexpressed in hypoxia, suggesting that it plays a role in cell survival in this condition. This review enumerates and analyses the recent evidence that points to the role of ERRα as a regulator of hypoxic genes, both in cooperation with HIF-1 and through HIF-1- independent mechanisms, in invertebrate and vertebrate models and in physiological and pathological scenarios. ERRα's functions during hypoxia include two mechanisms: (1) direct ERRα/HIF-1 interaction, which enhances HIF-1's transcriptional activity; and (2) transcriptional activation by ERRα of genes that are classical HIF-1 targets, such as VEGF or glycolytic enzymes. ERRα is thus gaining recognition for its prominent role in the hypoxia response, both in the presence and absence of HIF-1. In some models, ERRα prepares cells for hypoxia, with important clinical/therapeutic implications.

Benzotriazole Ultraviolet Stabilizers Promote Breast Cancer Cell Proliferation via Activating Estrogen-Related Receptors α and γ at Human-Relevant Levels

Benzotriazole ultraviolet stabilizers (BUVSs) are ubiquitous emerging pollutants that have been reported to show estrogenic disruption effects through interaction with the classic estrogen receptors (ERs) in the fashion of low activity. The present study aims at revealing the potential disruption mechanism via estrogen-related receptors α and γ (ERRα and ERRγ) pathways. By the competitive binding assay, we first found that BUVSs bond to ERRγ ligand binding domain (ERRγ-LBD) with Kd ranging from 0.66 to 19.27 μM. According to the results of reporter gene assays, the transcriptional activities of ERRα and ERRγ were promoted by most tested BUVSs with the lowest observed effective concentrations (LOEC) from 10 to 100 nM, which are in the range of human exposure levels. At 1 μM, most tested BUVSs showed higher agonistic activity toward ERRγ than ERRα. The most effective two BUVSs promoted the MCF-7 proliferation dependent on ERRα and ERRγ with a LOEC of 100 nM. The molecular dynamics simulation showed that most studied BUVSs had lower binding free energy with ERRγ than with ERRα. The structure-activity relationship analysis revealed that molecular polarizability, electron-donating ability, ionization potential, and softness were the main structural factors impacting the binding of BUVSs with ERRγ. Overall, our results provide novel insights into the estrogenic disruption effects of BUVSs.

[The effect of sex hormones and pregnancy on development and progression of uveal melanoma]

The analysis of literature revealed that men experience uveal melanoma (UM) more frequently and with worse prognosis. There are also descriptions of an aggressive course of UM in pregnant women. These facts prompted researchers to analyze the effect of sex hormones and pregnancy on the development and progression of UM. Many years of international experience have refuted the presence of a reliable difference between 5-year survival and 5-year survival without metastases between non-pregnant women with UM and pregnant women with UM. That data is regarded as level 3 evidence. The experts have concluded that UM is not a contraindication to current or future pregnancy, and exogenous hormones (oral contraceptives or hormone replacement therapy) do not affect the incidence and prognosis of UM. Publications provide evidence of expression of the receptors of certain sex hormones (ER, ERRα, LH and LHRH) in primary UM, as well as overexpression of the ESR1 and ESR2 genes in UM with poor predictive characteristics. Overall AR mRNA expression in UM was low, but it was higher in epithelial UMs. The fact of expression of estrogen receptors in UM gives grounds to experiment with them as a target for therapy.

Is Uveal Melanoma a Hormonally Sensitive Cancer? A Review of the Impact of Sex Hormones and Pregnancy on Uveal Melanoma

BACKGROUND

Despite a higher incidence and worse prognosis of uveal melanoma (UM) in men, there have been many case reports of pregnant patients with aggressive UM. This has led researchers to explore the influence of sex hormones and pregnancy on the development and progression of UM and hormones as potential therapeutic targets.

SUMMARY

A systematic literature review was conducted. More work is needed to elucidate the basis of sex differences in UM incidence and survival. The evaluation of germline BAP1 mutation would be beneficial in patients with UM presenting at a young age. Importantly, multiple studies reported no significant difference between the 5-year survival and 5-year metastasis-free survival rates between nonpregnant women with UM and pregnant women with UM. Multiple case-control studies disagree on how parity affects risk of UM. However, most studies agree that oral contraceptives and hormone replacement therapy have no effect on the incidence of UM. Current treatment strategies for pregnant patients with UM are discussed. Looking forward, this review reports recent research on targeted receptor-based chemotherapy, which is based on evidence of estrogen receptor (ER), estrogen-related receptor alpha (ERRα), and luteinizing hormone-releasing hormone (LHRH) receptor expression in UM.

KEY MESSAGES

Based on review of the literature, UM is not a contraindication to oral contraceptives, hormone replacement therapy, or pregnancy. Globe-sparing radiation can be used as a treatment option for pregnant patients. Due to the presence of ER on a subset of unselected UM, its potential for adjunctive targeted therapy with agents like tamoxifen should be explored. Lessons from cutaneous melanoma regarding tissue ratios of estrogen receptors (ERα:ERβ) should be applied to assess their therapeutic predictive value. In addition, ERRα-targeted therapeutics and LHRH analogs are worthy of further exploration in UM.

Cholesterol-Induced Metabolic Reprogramming in Breast Cancer Cells Is Mediated via the ERRα Pathway

Simple Summary

There is increasing evidence that obesity and high circulating cholesterol levels are associated with an increased risk of recurrence and a higher mortality rate in breast cancer patients via altering the metabolic programming in breast cancer cells. However, the underlying molecular mechanism by which high cholesterol levels reprogram the metabolic pathways in breast cancer cells is not well-understood. We have previously demonstrated that cholesterol acts as an endogenous agonist of estrogen-related receptor α (ERRα), a strong regulator of cellular metabolism. The aim of the current study is to demonstrate whether cholesterol/obesity mediates its pathogenic effect in breast cancer cells via altering metabolic pathways in an ERRα-dependent manner. The findings of this study provide mechanistic insights into the link between cholesterol/obesity and metabolic reprogramming in breast cancer patients and reveal the metabolic vulnerabilities in such breast cancer patients that could be therapeutically targeted.

Abstract

The molecular mechanism underlying the metabolic reprogramming associated with obesity and high blood cholesterol levels is poorly understood. We previously reported that cholesterol is an endogenous ligand of the estrogen-related receptor alpha (ERRα). Using functional assays, metabolomics, and genomics, here we show that exogenous cholesterol alters the metabolic pathways in estrogen receptor-positive (ER+) and triple-negative breast cancer (TNBC) cells, and that this involves increased oxidative phosphorylation (OXPHOS) and TCA cycle intermediate levels. In addition, cholesterol augments aerobic glycolysis in TNBC cells although it remains unaltered in ER+ cells. Interestingly, cholesterol does not alter the metabolite levels of glutaminolysis, one-carbon metabolism, or the pentose phosphate pathway, but increases the NADPH levels and cellular proliferation, in both cell types. Importantly, we show that the above cholesterol-induced modulations of the metabolic pathways in breast cancer cells are mediated via ERRα. Furthermore, analysis of the ERRα metabolic gene signature of basal-like breast tumours of overweight/obese versus lean patients, using the GEO database, shows that obesity may modulate ERRα gene signature in a manner consistent with our in vitro findings with exogenous cholesterol. Given the close link between high cholesterol levels and obesity, our findings provide a mechanistic explanation for the association between cholesterol/obesity and metabolic reprogramming in breast cancer patients.

Cholesterol as an Endogenous Ligand of ERRα Promotes ERRα-Mediated Cellular Proliferation and Metabolic Target Gene Expression in Breast Cancer Cells

Breast cancer is the 2nd leading cause of cancer-related death among women. Increased risk of breast cancer has been associated with high dietary cholesterol intake. However, the underlying mechanisms are not known. The nuclear receptor, estrogen-related receptor alpha (ERRα), plays an important role in breast cancer cell metabolism, and its overexpression has been linked to poor survival. Here we identified cholesterol as an endogenous ligand of ERRα by purification from human pregnancy serum using a GST-ERRα affinity column and liquid chromatography-tandem mass spectrometry (LC-MS/MS). We show that cholesterol interacts with ERRα and induces its transcriptional activity in estrogen receptor positive (ER+) and triple negative breast cancer (TNBC) cells. In addition, we show that cholesterol enhances ERRα-PGC-1α interaction, induces ERRα expression itself, augments several metabolic target genes of ERRα, and increases cell proliferation and migration in both ER+ and TNBC cells. Furthermore, the stimulatory effect of cholesterol on metabolic gene expression, cell proliferation, and migration requires the ERRα pathway. These findings provide a mechanistic explanation for the increased breast cancer risk associated with high dietary cholesterol and possibly the pro-survival effect of statins in breast cancer patients, highlighting the clinical relevance of lowering cholesterol levels in breast cancer patients overexpressing ERRα.