Antiproliferation activity of a small molecule repressor of liver receptor homolog 1

NR5A1 and NR5A2 regulate follicle development in chicken (Gallus gallus) by altering proliferation, apoptosis, and steroid hormone synthesis of granulosa cells

Chicken ovarian follicle development is regulated by complex and dynamic gene expression. Nuclear receptor 5A1 and 5A2 (NR5A1 and NR5A2, respectively) are key genes that regulate steroid hormone production and gonadal development in mammals; however, studies on follicular development in the chicken ovary are scarce. In this study, we investigated the functions of NR5A1 and NR5A2 on follicle development in chickens. The results showed that the expression of NR5A1 and NR5A2 was significantly higher in small yellow follicles and F5. Furthermore, the expression of NR5A1 and NR5A2 was significantly higher in follicular tissues of peak-laying hens (30 wk) than in follicular tissues of late-laying hens (60 wk), with high expression abundance in granulosa cells (GC). The overexpression of NR5A1 and NR5A2 significantly promoted proliferation and inhibited apoptosis of cultured GC; upregulated STAR, CYP11A1, and CYP19A1 expression and estradiol (E2) and progesterone (P4) synthesis in GC from preovulatory follicles (po-GC); and increased STAR, CYP11A1, and CYP19A1 promoter activities. In addition, follicle-stimulating hormone treatment significantly upregulated NR5A1 and NR5A2 expression in po-GC and significantly promoted FSHR, CYP11A1, and HSD3B1 expression in GC from pre-hierarchical follicles and po-GC. The core promoter region of NR5A1 was identified at the -1,095- to -483-bp and -2,054- to -1,536-bp regions from the translation start site (+1), and the core promoter region of NR5A2 was at -998 to -489 bp. Two single nucleotide polymorphisms (SNP) were identified in the core promoter region of the NR5A1 gene, which differed between high- and low-yielding chicken groups. Our study suggested that NR5A1 and NR5A2 promoted chicken follicle development by promoting GC proliferation and E2 and P4 hormone synthesis and inhibiting apoptosis. Moreover, we identified the promoter core region or functional site that regulates NR5A1 and NR5A2 expression.

Liver receptor homolog-1: structures, related diseases, and drug discovery

Liver receptor homolog-1 (LRH-1), a member of the nuclear receptor superfamily, is a ligand-regulated transcription factor that plays crucial roles in metabolism, development, and immunity. Despite being classified as an 'orphan' receptor due to the ongoing debate surrounding its endogenous ligands, recent researches have demonstrated that LRH-1 can be modulated by various synthetic ligands. This highlights the potential of LRH-1 as an attractive drug target for the treatment of inflammation, metabolic disorders, and cancer. In this review, we provide an overview of the structural basis, functional activities, associated diseases, and advancements in therapeutic ligand research targeting LRH-1.

Full-length nuclear receptor allosteric regulation

Nuclear receptors are a superfamily of transcription factors regulated by a wide range of lipids that include phospholipids, fatty acids, heme-based metabolites, and cholesterol-based steroids. Encoded as classic two-domain modular transcription factors, nuclear receptors possess a DNA-binding domain (DBD) and a lipid ligand-binding domain (LBD) containing a transcriptional activation function. Decades of structural studies on the isolated LBDs of nuclear receptors established that lipid-ligand binding allosterically regulates the conformation of the LBD, regulating transcriptional coregulator recruitment and thus nuclear receptor function. These structural studies have aided the development of several FDA-approved drugs, highlighting the importance of understanding the structure-function relationships between lipids and nuclear receptors. However, there are few published descriptions of full-length nuclear receptor structure and even fewer descriptions of how lipids might allosterically regulate full-length structure. Here, we examine multidomain interactions based on the published full-length nuclear receptor structures, evaluating the potential of interdomain interfaces within these nuclear receptors to act as inducible sites of allosteric regulation by lipids.

Nuclear receptor 5A2 regulation of Agrp underlies olanzapine-induced hyperphagia

Antipsychotic (AP) drugs are efficacious treatments for various psychiatric disorders, but excessive weight gain and subsequent development of metabolic disease remain serious side effects of their use. Increased food intake leads to AP-induced weight gain, but the underlying molecular mechanisms remain unknown. In previous studies, we identified the neuropeptide Agrp and the transcription factor nuclear receptor subfamily 5 group A member 2 (Nr5a2) as significantly upregulated genes in the hypothalamus following AP-induced hyperphagia. While Agrp is expressed specifically in the arcuate nucleus of the hypothalamus and plays a critical role in appetite stimulation, Nr5a2 is expressed in both the CNS and periphery, but its role in food intake behaviors remains unknown. In this study, we investigated the role of hypothalamic Nr5a2 in AP-induced hyperphagia and weight gain. In hypothalamic cell lines, olanzapine treatment resulted in a dose-dependent increase in gene expression of Nr5a2 and Agrp. In mice, the pharmacological inhibition of NR5A2 decreased olanzapine-induced hyperphagia and weight gain, while the knockdown of Nr5a2 in the arcuate nucleus partially reversed olanzapine-induced hyperphagia. Chromatin-immunoprecipitation studies showed for the first time that NR5A2 directly binds to the Agrp promoter region. Lastly, the analysis of single-cell RNA seq data confirms that Nr5a2 and Agrp are co-expressed in a subset of neurons in the arcuate nucleus. In summary, we identify Nr5a2 as a key mechanistic driver of AP-induced food intake. These findings can inform future clinical development of APs that do not activate hyperphagia and weight gain.

Zygotic genome activation by the totipotency pioneer factor Nr5a2

Life begins with a switch in genetic control from the maternal to the embryonic genome during zygotic genome activation (ZGA). Despite its importance, the essential regulators of ZGA remain largely unknown in mammals. On the basis of de novo motif searches, we identified the orphan nuclear receptor Nr5a2 as a key activator of major ZGA in mouse two-cell embryos. Nr5a2 is required for progression beyond the two-cell stage. It binds to its motif within SINE B1/Alu retrotransposable elements found in cis-regulatory regions of ZGA genes. Chemical inhibition suggests that 72% of ZGA genes are regulated by Nr5a2 and potentially other orphan nuclear receptors. Nr5a2 promotes chromatin accessibility during ZGA and binds nucleosomal DNA in vitro. We conclude that Nr5a2 is an essential pioneer factor that regulates ZGA.

Regulation of the Intestinal Extra-Adrenal Steroidogenic Pathway Component LRH-1 by Glucocorticoids in Ulcerative Colitis

Ulcerative colitis (UC) is an inflammatory bowel disease (IBD) and can be treated with glucocorticoids (GC), although some patients are unresponsive to this therapy. The transcription factor LRH-1/NR5A2 is critical to intestinal cortisol production (intestinal steroidogenesis), being reduced in UC patients. However, the relationship between LRH-1 expression and distribution with altered corticosteroid responses is unknown. To address this, we categorized UC patients by their steroid response. Here, we found that steroid-dependent and refractory patients presented reduced glucocorticoid receptor (GR)-mediated intestinal steroidogenesis compared to healthy individuals and responder patients, possibly related to increased colonic mucosa GR isoform beta (GRβ) content and cytoplasmic LRH-1 levels in epithelial and lamina propria cells. Interestingly, an intestinal epithelium-specific GR-induced knockout (GR^iKO) dextran sodium sulfate (DSS)-colitis mice model presented decreased epithelial LRH-1 expression, whilst it increased in the lamina propria compared to DSS-treated control mice. Mechanistically, GR directly induced NR5A2 gene expression in CCD841CoN cells and human colonic organoids. Furthermore, GR bound to two glucocorticoid-response elements within the NR5A2 promoter in dexamethasone-stimulated CCD841CoN cells. We conclude that GR contributes to intestinal steroidogenesis by inducing LRH-1 in epithelial cells, suggesting LRH-1 as a potential marker for glucocorticoid-impaired response in UC. However, further studies with a larger patient cohort will be necessary to confirm role of LRH-1 as a therapeutic biomarker.

The Medicinal Chemistry and Therapeutic Potential of LRH-1 Modulators

The ligand-activated transcription factor liver receptor homologue 1 (LRH-1, NR5A2) is involved in the regulation of metabolic homeostasis, including cholesterol and glucose balance. Preliminary evidence points to therapeutic potential of LRH-1 modulation in diabetes, hepatic diseases, inflammatory bowel diseases, atherosclerosis, and certain cancers, but because of a lack of suitable ligands, pharmacological control of LRH-1 has been insufficiently studied. Despite the availability of considerable structural knowledge on LRH-1, only a few ligand chemotypes have been developed, and potent, selective, and bioavailable tools to explore LRH-1 modulation in vivo are lacking. In view of the therapeutic potential of LRH-1 in prevalent diseases, improved chemical tools are needed to probe the beneficial and adverse effects of pharmacological LRH-1 modulation in sophisticated preclinical models and to further elucidate the receptor's molecular function.

Roles of NR5A1 and NR5A2 in the regulation of steroidogenesis by Clock gene and bone morphogenetic proteins by human granulosa cells

The functional role of the transcription factors NR5A1 and NR5A2 and their interaction with Clock gene and bone morphogenetic proteins (BMPs) were investigated in human granulosa KGN cells. Treatment with BMP-15 and GDF-9 suppressed forskolin (FSK)-induced steroidogenesis as shown by the mRNA expression levels of StAR and P450scc but not the mRNA expression level of P450arom. Of interest, treatment with BMP-15 and GDF-9 also suppressed FSK-induced NR5A2 mRNA expression. Treatment with BMP-15 suppressed NR5A2 mRNA and protein expression but increased Clock mRNA and protein expression levels by granulosa cells. The mRNA expression levels of NR5A1, but not those of NR5A2, were positively correlated with the levels of Clock mRNA, while the mRNA levels of Id-1, the target gene of BMP signaling, were positively correlated with those of NR5A1 but not with those of NR5A2. It was also demonstrated that the mRNA expression levels of NR5A1 were positively correlated with those of P450arom and 3βHSD, whereas the mRNA expression level of NR5A2 was correlated with those of StAR and P450scc. Furthermore, inhibition of Clock gene expression by siRNA attenuated the expression of NR5A1, and the mRNA levels of Clock gene were significantly correlated with those of NR5A1. Collectively, the results suggested a novel mechanism by which Clock gene expression induced by BMP-15 is functionally linked to the expression of NR5A1, whereas NR5A2 expression is suppressed by BMP-15 in granulosa cells. The interaction between Clock NR5A1/NR5A2 and BMP-15 is likely to be involved in the fine-tuning of steroidogenesis by ovarian granulosa cells.

Nuclear-mitochondrial crosstalk: On the role of the nuclear receptor liver receptor homolog-1 (NR5A2) in the regulation of mitochondrial metabolism, cell survival, and cancer

Liver receptor homolog-1 (LRH-1, NR5A2) is an orphan nuclear receptor with widespread activities in the regulation of development, stemness, metabolism, steroidogenesis, and proliferation. Many of the LRH-1-regulated processes target the mitochondria and associated activities. While under physiological conditions, a balanced LRH-1 expression and regulation contribute to the maintenance of a physiological equilibrium, deregulation of LRH-1 has been associated with inflammation and cancer. In this review, we discuss the role and mechanism(s) of how LRH-1 regulates metabolic processes, cell survival, and cancer in a nuclear-mitochondrial crosstalk, and evaluate its potential as a pharmacological target.

Development of a Versatile and Sensitive Direct Ligand Binding Assay for Human NR5A Nuclear Receptors

As regulators of steroidogenesis, development, and metabolism, the nuclear receptor 5A (NR5A) subfamily members steroidogenic factor 1 (SF-1) and liver receptor homologue 1 (LRH-1) are important pharmacological targets for cancers and metabolic diseases. Evaluation of small molecule modulators and candidate endogenous ligands for these orphan receptors has been hindered by the lack of accessible, robust direct-binding assays. Here, we leverage the potency of our new NR5A agonist (6N) to create a high-affinity probe for fluorescence polarization competition assays by conjugating 6N to fluorescein (FAM). The 6N-FAM probe tightly binds the NR5A receptors and detects direct binding of synthetic and phospholipid ligands. For 25 LRH-1 agonists, affinity predicts potency in cellular activation assays, demonstrating the potential for this assay in drug discovery. Moreover, phospholipids dilauroylphosphatidylcholine and phosphatidylinositol(4,5)phosphate bind with high affinity, demonstrating this assay is robust for evaluation of candidate endogenous ligands for human NR5A receptors.

Pharmacological LRH-1/Nr5a2 inhibition limits pro-inflammatory cytokine production in macrophages and associated experimental hepatitis

Liver receptor homolog-1 (LRH-1, Nr5a2) is an orphan nuclear receptor mainly expressed in tissues of endodermal origin, where its physiological role has been extensively studied. LRH-1 has been implicated in liver cell differentiation and proliferation, as well as glucose, lipid, and bile acid metabolism. In addition, increasing evidence highlights its role in immunoregulatory processes via glucocorticoid synthesis in the intestinal epithelium. Although the direct function of LRH-1 in immune cells is fairly elucidated, a role of LRH-1 in the regulation of macrophage differentiation has been recently reported. In this study, we aimed to investigate the role of LRH-1 in the regulation of pro-inflammatory cytokine production in macrophages. Our data demonstrate that pharmacological inhibition, along with LRH-1 knockdown, significantly reduced the lipopolysaccharide (LPS)-induced production of pro-inflammatory cytokines in the macrophage line RAW 264.7 cells, as well as in primary murine macrophages. This inhibitory effect was found to be independent of defects of LRH-1-regulated cell proliferation or toxic effects of the LRH-1 inhibitors. In contrast, LRH-1 inhibition reduced the mitochondrial ATP production and metabolism of macrophages through downregulation of the LRH-1 targets glucokinase and glutminase-2, and thus impairing the LPS-induced macrophage activation. Interestingly, in vivo pharmacological inhibition of LRH-1 also resulted in reduced tumor necrosis factor (TNF) production and associated decreased liver damage in a macrophage- and TNF-dependent mouse model of hepatitis. Noteworthy, despite hepatocytes expressing high levels of LRH-1, pharmacological inhibition of LRH-1 per se did not cause any obvious liver damage. Therefore, this study proposes LRH-1 as an emerging therapeutic target in the treatment of inflammatory disorders, especially where macrophages and cytokines critically decide the extent of inflammation.

Estrogen Receptor α (ERα)-targeting Compounds and Derivatives: Recent Advances in Structural Modification and Bioactivity

Breast cancer is the most common cancer suffered by female, and the second highest cause of cancer-related death among women worldwide. At present, hormone therapy is still the main treatment route and can be divided into three main categories: selective estrogen receptor modulators (SERMs), selective estrogen receptor downregulators (SERDs), and aromatase inhibitors (AIs). However, breast cancer is difficult to cure even after several rounds of anti-estrogen therapy and most drugs have serious side-effects. Here, we review the literature published over the past five years regarding the isolation and synthesis of analogs and their derivatives.

The orphan nuclear receptor LRH-1/NR5a2 critically regulates T cell functions

LRH-1 (liver receptor homolog-1/NR5a2) is an orphan nuclear receptor, which regulates glucose and lipid metabolism, as well as intestinal inflammation via the transcriptional control of intestinal glucocorticoid synthesis. Predominantly expressed in epithelial cells, its expression and role in immune cells are presently enigmatic. LRH-1 was found to be induced in immature and mature T lymphocytes upon stimulation. T cell-specific deletion of LRH-1 causes a drastic loss of mature peripheral T cells. LRH-1-depleted CD4⁺ T cells exert strongly reduced activation-induced proliferation in vitro and in vivo and fail to mount immune responses against model antigens and to induce experimental intestinal inflammation. Similarly, LRH-1-deficient cytotoxic CD8⁺ T cells fail to control viral infections. This study describes a novel and critical role of LRH-1 in T cell maturation, functions, and immopathologies and proposes LRH-1 as an emerging pharmacological target in the treatment of T cell-mediated inflammatory diseases.

Extra-Adrenal Glucocorticoid Synthesis in the Intestinal Mucosa: Between Immune Homeostasis and Immune Escape

Glucocorticoids (GCs) are steroid hormones predominantly produced in the adrenal glands in response to physiological cues and stress. Adrenal GCs mediate potent anti-inflammatory and immunosuppressive functions. Accumulating evidence in the past two decades has demonstrated other extra-adrenal organs and tissues capable of synthesizing GCs. This review discusses the role and regulation of GC synthesis in the intestinal epithelium in the regulation of normal immune homeostasis, inflammatory diseases of the intestinal mucosa, and the development of intestinal tumors.

The Orphan Nuclear Receptors Steroidogenic Factor-1 and Liver Receptor Homolog-1: Structure, Regulation, and Essential Roles in Mammalian Reproduction

Nuclear receptors are intracellular proteins that act as transcription factors. Proteins with classic nuclear receptor domain structure lacking identified signaling ligands are designated orphan nuclear receptors. Two of these, steroidogenic factor-1 (NR5A1, also known as SF-1) and liver receptor homolog-1 (NR5A2, also known as LRH-1), bind to the same DNA sequences, with different and nonoverlapping effects on targets. Endogenous regulation of both is achieved predominantly by cofactor interactions. SF-1 is expressed primarily in steroidogenic tissues, LRH-1 in tissues of endodermal origin and the gonads. Both receptors modulate cholesterol homeostasis, steroidogenesis, tissue-specific cell proliferation, and stem cell pluripotency. LRH-1 is essential for development beyond gastrulation and SF-1 for genesis of the adrenal, sexual differentiation, and Leydig cell function. Ovary-specific depletion of SF-1 disrupts follicle development, while LRH-1 depletion prevents ovulation, cumulus expansion, and luteinization. Uterine depletion of LRH-1 compromises decidualization and pregnancy. In humans, SF-1 is present in endometriotic tissue, where it regulates estrogen synthesis. SF-1 is underexpressed in ovarian cancer cells and overexpressed in Leydig cell tumors. In breast cancer cells, proliferation, migration and invasion, and chemotherapy resistance are regulated by LRH-1. In conclusion, the NR5A orphan nuclear receptors are nonredundant factors that are crucial regulators of a panoply of biological processes, across multiple reproductive tissues.

Targeting LRH‑1 in hepatoblastoma cell lines causes decreased proliferation

Hepatoblastoma is the most common malignant liver tumor in children. Since it is often unresectable and exhibits drug resistance, the treatment of advanced hepatoblastoma is challenging. The orphan nuclear receptor liver receptor homolog-1 (LRH-1) serves prominent roles in malignancy; however, to the best of our knowledge, the role of LRH-1 in hepatoblastoma remains unknown. In the present study, human hepatoblastoma cell lines were analyzed; the mRNA and protein expression levels of LRH-1 were significantly higher in HepG2 and HuH6 cells compared with those in HepT1 cells and control THLE-2 cells. Knockdown of LRH-1 resulted in decreased HepG2 and HuH6 cell proliferation via downregulation of cyclin D1 (CCND1) and c-Myc. Furthermore, treatment with an LRH-1 antagonist (LRA) inhibited the proliferation and colony formation of cell lines in a dose-dependent manner, and induced cell cycle arrest at G₁ phase through inhibition of CCND1 expression. Finally, LRA treatment enhanced the cytotoxic effects of doxorubicin on hepatoblastoma cells. Collectively, these findings suggested that LRH-1 may have an important role in the progression of hepatoblastoma and implicated LRA as a novel, potential therapeutic agent for the treatment of hepatoblastoma.

Development of Hybrid Phospholipid Mimics as Effective Agonists for Liver Receptor Homologue-1

The orphan nuclear receptor Liver Receptor Homologue-1 (LRH-1) is an emerging drug target for metabolic disorders. The most effective known LRH-1 modulators are phospholipids or synthetic hexahydropentalene compounds. While both classes have micromolar efficacy, they target different portions of the ligand binding pocket and activate LRH-1 through different mechanisms. Guided by crystallographic data, we combined aspects of both ligand classes into a single scaffold, resulting in the most potent and efficacious LRH-1 agonists to date.

MicroRNA-374b reduces the proliferation and invasion of colon cancer cells by regulation of LRH-1/Wnt signaling

Deregulation of microRNA (miRNA) has been suggested as a critical event in colon cancer development and progression. Recent studies have suggested that miR-374b is a novel cancer-related miRNA involved in several cancer types. Thus far, very little is known about the role of miR-374b in colon cancer; therefore, the goal of this study was to investigate the potential role of miR-374b in colon cancer. Here, we showed that miR-374b expression was significantly downregulated in colon cancer tissues and cell lines. Overexpression of miR-374b inhibited the proliferation and invasion of colon cancer cells, while miR-374b suppression promoted colon cancer cell proliferation and invasion. Liver receptor homolog-1 (LRH-1) was identified as a target of miR-374b in colon cancer cells. Both the mRNA and protein expression of LRH-1 were regulated by miR-374b. In addition, an inverse correlation between LRH-1 mRNA and miR-374b expression was evidenced in colon cancer specimens. Notably, overexpression of miR-374b also downregulated the Wnt signaling in colon cancer cells. Furthermore, restoration of LRH-1 expression significantly abolished the antitumor effect of miR-374b in colon cancer cells. These findings suggest that miR-374b inhibits colon cancer cell proliferation and invasion through downregulation of LRH-1 expression. Inhibiting LRH-1 by miR-374b may represent a novel therapeutic strategy for the treatment of colon cancer.

LRH-1 expression patterns in breast cancer tissues are associated with tumour aggressiveness

The significance and regulation of liver receptor homologue 1 (LRH-1, NR5A2), a tumour-promoting transcription factor in breast cancer cell lines, is unknown in clinical breast cancers. This study aims to determine LRH-1/NR5A2 expression in breast cancers and relationship with DNA methylation and tumour characteristics. In The Cancer Genome Atlas breast cancer cohort NR5A2 expression was positively associated with intragenic CpG island methylation (1.4-fold expression for fully methylated versus not fully methylated, p=0.01) and inversely associated with promoter CpG island methylation (0.6-fold expression for fully methylated versus not fully methylated, p=0.036). LRH-1 immunohistochemistry of 329 invasive carcinomas and ductal carcinoma in situ (DCIS) was performed. Densely punctate/coarsely granular nuclear reactivity was significantly associated with high tumour grade (p<0.005, p=0.033 in invasive carcinomas and DCIS respectively), negative estrogen receptor status (p=0.008, p=0.038 in overall cohort and invasive carcinomas, respectively), negative progesterone receptor status (p=0.003, p=0.013 in overall cohort and invasive carcinomas, respectively), HER2 amplification (overall cohort p=0.034) and non-luminal intrinsic subtype (p=0.018, p=0.038 in overall cohort and invasive carcinomas, respectively). These significant associations of LRH-1 protein expression with tumour phenotype suggest that LRH-1 is an important indicator of tumour biology in breast cancers and may be useful in risk stratification.

MicroRNA-136 inhibits colon cancer cell proliferation and invasion through targeting liver receptor homolog-1/Wnt signaling

An increasing number of studies have reported that microRNAs (miRNAs) are involved in the malignant behavior of colon cancer cells through directly targeting multiple tumor suppressors or oncogenes. The expression and role of miR-136 has been reported in several types of human cancer. However, the role of miR-136 in colon cancer remains unclear. In this study, we aimed to investigate the expression and function of miR-136 in colon cancer and the potential underlying mechanism. Here, we found that miR-136 was decreased in colon cancer cell lines and tissues. Overexpression of miR-136 inhibited the proliferation and invasion in SW480 and HCT116 cell lines while suppression of miR-136 exhibited the opposite effect. Liver receptor homolog-1 (LRH-1) was identified as a direct target gene of miR-136. Notably, miR-136 overexpression suppressed LRH-1 expression as well as Wnt signaling in SW480 and HCT116 cell lines. The miR-136 expression level inversely correlated with LRH-1 mRNA expression in colon cancer specimens. Moreover, overexpression of LRH-1 partially reversed the miR-136-induced antitumor effect in SW480 and HCT116 cell lines. Taken together, these findings suggest that miR-136 functions as a negative regulator in colon cancer progression by targeting LRH-1 and that miR-136 downregulation contributes to high expression of LRH-1 and aberrant activation of Wnt signaling, leaving open the possibility that miR-136 may serve as a potential therapeutic target for colon cancer.

LRH-1 senses signaling from phosphatidylcholine to regulate the expansion growth of digestive organs via synergy with Wnt/β-catenin signaling in zebrafish

Liver receptor homolog-1 (LRH-1) is an orphan nuclear receptor that is critical for the growth and proliferation of cancer cells and other biological processes, including lipid transportation and metabolism, sexual determination and steroidogenesis. However, because homozygous lrh-1^-/- mice die in utero, the regulatory mechanisms involved in embryonic development mediated by this receptor are poorly understood. In the present study, we performed transcription activator-like effector nuclease (TALEN)-mediated loss-of-function assays, taking advantage of zebrafish external fertilization, to investigate the function of lrh-1. The digestive organs were affected by lrh-1 depletion as a result of cell-cycle arrest (at the checkpoint of G1 to S phase), but not cell apoptosis. Biochemical analysis revealed that LRH-1 augments the transcriptional activity of β-catenin 1 and 2 via physical interactions. Screening the specific ligand(s) sensed by LRH-1 during organogenesis revealed that phosphatidylcholine (PC), a potential ligand, is the upstream target of LRH-1 during endoderm development. These data provide evidence for the crosstalk between the PC/LRH-1 and Wnt/β-catenin signaling pathways during the expansion growth of endoderm organs.

Liver receptor homolog-1 (NR5a2) regulates CD95/Fas ligand transcription and associated T-cell effector functions

CD95/Fas ligand (FasL) is a cell death-promoting member of the tumor necrosis factor family with important functions in the regulation of T-cell homeostasis and cytotoxicity. In T cells, FasL expression is tightly regulated on a transcriptional level involving a complex set of different transcription factors. The orphan nuclear receptor liver receptor homolog-1 (LRH-1/NR5a2) is involved in the regulation of development, lipid metabolism and proliferation and is predominantly expressed in epithelial tissues. However, its expression in T lymphocytes has never been reported so far. Based on in silico analysis, we identified potential LRH-1 binding sites within the FASLG promoter. Here, we report that LRH-1 is expressed in primary and secondary lymphatic tissues, as well as in CD4⁺ and CD8⁺ T cells. LRH-1 directly binds to its binding sites in the FASLG promoter, and thereby drives FASLG promoter activity. Mutations in the LRH-1 binding sites reduce FASLG promoter activity. Pharmacological inhibition of LRH-1 decreases activation-induced FasL mRNA expression, as well as FasL-mediated activation-induced T-cell apoptosis and T-cell cytotoxicity. In a mouse model of Concanavalin A-induced and FasL-mediated hepatitis pharmacological inhibition of LRH-1 resulted in decreased hepatic FasL expression and a significant reduction of liver damage. In summary, these data show for the first time LRH-1 expression in T cells, its role in FASLG transcription and the potential of pharmacological inhibition of LRH-1 in the treatment of FasL-mediated immunopathologies.

MicroRNA-219-5p Represses the Proliferation, Migration, and Invasion of Gastric Cancer Cells by Targeting the LRH-1/Wnt/β-Catenin Signaling Pathway

MicroRNAs (miRNAs) are reportedly involved in gastric cancer development and progression. In particular, miR-219-5p has been reported to be a tumor-associated miRNA in human cancer. However, the role of miR-219-5p in gastric cancer remains unclear. In this study, we investigated for the first time the potential role and underlying mechanism of miR-219-5p in the proliferation, migration, and invasion of human gastric cancer cells. miR-219-5p was found to be markedly decreased in gastric cancer tissues and cell lines compared with adjacent tissues and normal gastric epithelial cells. miR-219-5p mimics or anti-miR-219-5p was transfected into gastric cancer cell lines to overexpress or suppress miR-219-5p expression, respectively. Results showed that miR-219-5p overexpression significantly decreased the proliferation, migration, and invasion of gastric cancer cells. Conversely, miR-219-5p suppression demonstrated a completely opposite effect. Bioinformatics and luciferase reporter assays indicated that miR-219-5p targeted the 3′-untranslated region of the liver receptor homolog-1 (LRH-1), a well-characterized oncogene. Furthermore, miR-219-5p inhibited the mRNA and protein levels of LRH-1. LRH-1 mRNA expression was inversely correlated with miR-219-5p expression in gastric cancer tissues. miR-219-5p overexpression significantly decreased the Wnt/β-catenin signaling pathway in gastric cancer cells. Additionally, LRH-1 restoration can markedly reverse miR-219-5p-mediated tumor suppressive effects. Our study suggests that miR-219-5p regulated the proliferation, migration, and invasion of human gastric cancer cells by suppressing LRH-1. miR-219-5p may be a potential target for gastric cancer therapy.

The emerging roles of orphan nuclear receptors in prostate cancer

Orphan nuclear receptors are members of the nuclear receptor (NR) superfamily and are so named because their endogenous physiological ligands are either unknown or may not exist. Because of their important regulatory roles in many key physiological processes, dysregulation of signalings controlled by these receptors is associated with many diseases including cancer. Over years, studies of orphan NRs have become an area of great interest because their specific physiological and pathological roles have not been well-defined, and some of them are promising drug targets for diseases. The recently identified synthetic small molecule ligands, acting as agonists or antagonists, to these orphan NRs not only help to understand better their functional roles but also highlight that the signalings mediated by these ligand-independent NRs in diseases could be therapeutically intervened. This review is a summary of the recent advances in elucidating the emerging functional roles of orphan NRs in cancers, especially prostate cancer. In particular, some orphan NRs, RORγ, TR2, TR4, COUP-IFII, ERRα, DAX1 and SHP, exhibit crosstalk or interference with androgen receptor (AR) signaling in either normal or malignant prostatic cells, highlighting their involvement in prostate cancer progression as androgen and AR signaling pathway play critical roles in this process. We also propose that a better understanding of the mechanism of actions of these orphan NRs in prostate gland or prostate cancer could help to evaluate their potential value as therapeutic targets for prostate cancer.

Disulfide-Trapping Identifies a New, Effective Chemical Probe for Activating the Nuclear Receptor Human LRH-1 (NR5A2)

Conventional efforts relying on high-throughput physical and virtual screening of large compound libraries have failed to yield high-efficiency chemical probes for many of the 48 human nuclear receptors. Here, we investigated whether disulfide-trapping, an approach new to nuclear receptors, would provide effective lead compounds targeting human liver receptor homolog 1 (hLRH-1, NR5A2). Despite the fact that hLRH-1 contains a large ligand binding pocket and binds phospholipids with high affinity, existing synthetic hLRH-1 ligands are of limited utility due to poor solubility, low efficacy or significant off-target effects. Using disulfide-trapping, we identified a lead compound that conjugates with remarkably high-efficiency to a native cysteine residue (Cys³⁴⁶) lining the hydrophobic cavity in the ligand binding domain of hLRH-1. Guided by computational modeling and cellular assays, the lead compound was elaborated into ligands PME8 and PME9 that bind hLRH-1 reversibly (no cysteine reactivity) and increase hLRH-1 activity in cells. When compared with the existing hLRH-1 synthetic agonist RJW100, both PME8 and PME9 showed comparable induction of the LRH-1 dependent target gene CYP24A1 in human HepG2 cells, beginning as early as 3 h after drug treatment. The induction is specific as siRNA-mediated knock-down of hLRH-1 renders both PME8 and PME9 ineffective. These data show that PME8 and PME9 are potent activators of hLRH-1 and suggest that with further development this lead series may yield useful chemical probes for manipulating LRH-1 activity in vivo.

MicroRNA-376c suppresses non-small-cell lung cancer cell growth and invasion by targeting LRH-1-mediated Wnt signaling pathway

MicroRNAs (miRNAs) that negatively regulate gene expression have emerged as novel therapeutic tools for cancer treatment. In this study, we investigated the potential role of Liver receptor homolog-1 (LRH-1), a novel oncogene, in non-small-cell lung cancer (NSCLC), and examined the regulation of LRH-1 by miRNAs. We found that LRH-1 was highly overexpressed in NSCLC cell lines. Knockdown of LRH-1 by small interfering RNA significantly inhibited NSCLC cell growth and invasion. miR-376c directly targeted the 3'-untranslated region (UTR) of LRH-1 and negatively regulated LRH-1 expression, as detected by dual-luciferase reporter assay, real-time quantitative polymerase chain reaction and Western blot analysis. Further data showed that miR-376c expression was inversely correlated with LRH-1 expression in clinical cancer samples. Overexpression of miR-376c could inhibit NSCLC cell growth and invasion as well as Wnt signaling. In contrast, depletion of miR-376c exhibited the opposite effects. Moreover, these effects of miR-376c overexpression were partially abrogated by overexpression of LRH-1. Taken together, these results indicate that LRH-1 is involved in regulating the growth and invasion of NSCLC cells and that miR-376c inhibits NSCLC cell growth and invasion by targeting LRH-1, providing a novel insight into the potential for development of anti-cancer drugs for NSCLC.

LRH-1 drives colon cancer cell growth by repressing the expression of the CDKN1A gene in a p53-dependent manner

Liver receptor homologue 1 (LRH-1) is an orphan nuclear receptor that has been implicated in the progression of breast, pancreatic and colorectal cancer (CRC). To determine mechanisms underlying growth promotion by LRH-1 in CRC, we undertook global expression profiling following siRNA-mediated LRH-1 knockdown in HCT116 cells, which require LRH-1 for growth and in HT29 cells, in which LRH-1 does not regulate growth. Interestingly, expression of the cell cycle inhibitor p21 (CDKN1A) was regulated by LRH-1 in HCT116 cells. p21 regulation was not observed in HT29 cells, where p53 is mutated. p53 dependence for the regulation of p21 by LRH-1 was confirmed by p53 knockdown with siRNA, while LRH-1-regulation of p21 was not evident in HCT116 cells where p53 had been deleted. We demonstrate that LRH-1-mediated p21 regulation in HCT116 cells does not involve altered p53 protein or phosphorylation, and we show that LRH-1 inhibits p53 recruitment to the p21 promoter, likely through a mechanism involving chromatin remodelling. Our study suggests an important role for LRH-1 in the growth of CRC cells that retain wild-type p53.

MicroRNA-381 suppresses cell growth and invasion by targeting the liver receptor homolog-1 in hepatocellular carcinoma

MicroRNAs (miRs) have emerged as prospective tools for human cancer therapy, including hepatocellular carcinoma (HCC) therapy. Previous studies have suggested that miR-381 functions as oncogenic or tumor-suppressive miRs in other cancer types. However, the role of miR-381 in HCC remains unknown. The present study investigated the expression and functional role of miR-381 in HCC. miR-381 expression was significantly decreased in HCC tissues and cell lines. miR-381 overexpression significantly inhibited HCC cell proliferation and colony formation, induced G0/G1 cell cycle arrest and suppressed cell invasion. Conversely, suppression of miR-381 showed the opposite effect in HCC cells. Bioinformatics analysis and dual-luciferase reporter assay results showed that miR-381 directly targeted the 3'-untranslated region of liver receptor homolog-1 (LRH-1), and quantitative polymerase chain reaction and western blot analysis results showed that miR-381 negatively modulated LRH-1 expression. Data elucidated that miR-381 directly regulated HCC cell growth and invasion, as well as the Wnt signaling pathways, by targeting LRH-1. Clinical tissue detection data revealed an inverse correlation between miR-381 and LRH-1 expression in HCC tissues, further indicating the functional significance of miR-381-LRH-1 in regulating HCC tumorigenesis. The present study indicates that miR-381 may be a novel tumor suppressor that blocks HCC growth and invasion by targeting LRH-1. The results present novel insights into understanding the molecular mechanism underlying HCC tumorigenesis and provide a future direction to the development of therapeutic interventions for HCC.

Unexpected Allosteric Network Contributes to LRH-1 Co-regulator Selectivity

Phospholipids (PLs) are unusual signaling hormones sensed by the nuclear receptor liver receptor homolog-1 (LRH-1), which has evolved a novel allosteric pathway to support appropriate interaction with co-regulators depending on ligand status. LRH-1 plays an important role in controlling lipid and cholesterol homeostasis and is a potential target for the treatment of metabolic and neoplastic diseases. Although the prospect of modulating LRH-1 via small molecules is exciting, the molecular mechanism linking PL structure to transcriptional co-regulator preference is unknown. Previous studies showed that binding to an activating PL ligand, such as dilauroylphosphatidylcholine, favors LRH-1's interaction with transcriptional co-activators to up-regulate gene expression. Both crystallographic and solution-based structural studies showed that dilauroylphosphatidylcholine binding drives unanticipated structural fluctuations outside of the canonical activation surface in an alternate activation function (AF) region, encompassing the β-sheet-H6 region of the protein. However, the mechanism by which dynamics in the alternate AF influences co-regulator selectivity remains elusive. Here, we pair x-ray crystallography with molecular modeling to identify an unexpected allosteric network that traverses the protein ligand binding pocket and links these two elements to dictate selectivity. We show that communication between the alternate AF region and classical AF2 is correlated with the strength of the co-regulator interaction. This work offers the first glimpse into the conformational dynamics that drive this unusual PL-mediated nuclear hormone receptor activation.

Suppression of liver receptor homolog-1 by microRNA-451 represses the proliferation of osteosarcoma cells

Liver receptor homolog-1 (LRH-1) plays an important role in the onset and progression of many cancer types. However, the role of LRH-1 in osteosarcoma has not been well investigated. In this study, the critical role of LRH-1 in osteosarcoma cells was described. Quantitative polymerase chain reaction and Western blot analysis results revealed that LRH-1 was highly overexpressed in osteosarcoma cells. LRH-1 was knocked down by small interfering RNA (siRNA), and this phenomenon significantly inhibited osteosarcoma cell proliferation. Bioinformatics analysis results showed that LRH-1 contained putative binding sites of microRNA-451 (miR-451); this result was further validated through a dual-luciferase activity reporter assay. miR-451 was overexpressed in osteosarcoma cells through transfection of miR-451 mimics; miR-451 overexpression then significantly inhibited LRH-1 expression and cell proliferation. The loss of LRH-1 by siRNA or miR-451 mimics significantly impaired Wnt/β-catenin activity, leading to G0/G1 cell cycle arrest. Results showed that LRH-1 is implicated in osteosarcoma. Therefore, miR-451-induced suppression of LRH-1 can be a novel therapy to treat osteosarcoma.