Breast cancer susceptibility gene 1 (BRCA1) is a tumor suppressor protein that functions to maintain genomic stability through critical roles in DNA repair, cell-cycle arrest, and transcriptional control. The androgen receptor (AR) is expressed in more than 70% of breast cancers and has been implicated in breast cancer pathogenesis. However, little is known about the role of BRCA1 in AR-mediated cell proliferation in human breast cancer. Here, we report that a high expression of AR in breast cancer patients was associated with shorter overall survival (OS) using a tissue microarray with 149 nonmetastatic breast cancer patient samples. We reveal that overexpression of BRCA1 significantly inhibited expression of AR through activation of SIRT1 in breast cancer cells. Meanwhile, SIRT1 induction or treatment with a SIRT1 agonist, resveratrol, inhibits AR-stimulated proliferation. Importantly, this mechanism is manifested in breast cancer patient samples and TCGA database, which showed that low SIRT1 gene expression in tumor tissues compared with normal adjacent tissues predicts poor prognosis in patients with breast cancer. Taken together, our findings suggest that BRCA1 attenuates AR-stimulated proliferation of breast cancer cells via SIRT1 mediated pathway.

Vascular smooth muscle cells (VSMC) are the most abundant cell type in the artery's media layer and regulate vascular tone and lesion remodeling during atherogenesis. Like monocyte-derived macrophages, VSMCs accumulate excess lipids and contribute to the total intimal foam cell population in human coronary plaques and mouse aortic atheroma. While there are extensive studies characterizing the contribution of lipid metabolism in macrophage immunometabolic responses in atherosclerotic plaques, the role of VSMC lipid metabolism in regulating vascular function and lesion remodeling in vivo remains poorly understood. Here, we report that the liver X receptor (LXR) signaling pathway in VSMC is continuously activated during atherogenesis. Notably, we found that LXR deficiency in SMCs under hypercholesterolemic conditions influenced lesion remodeling by altering the fate of dedifferentiated SMCs and promoting the accumulation of VSMC-derived transitional cells. This phenotypic switching was accompanied by reduced indices of plaque stability, characterized by a larger necrotic core area and reduced fibrous cap thickness. Moreover, SMC-specific LXR deficiency impaired vascular function and caused visceral myopathy characterized by maladaptive bladder remodeling and gut lipid malabsorption. Mechanistically, we found that the expression of several genes involved in cholesterol efflux and FA synthesis including Abca1, Srebf1, Scd1, Scd2, Acsl3, and Mid1ip1 was downregulated in mice lacking LXRαβ in SMCs, likely contributing to the phenotypic switching of VSMC in the atherosclerotic lesions.

Microglia, the largest population of brain immune cells, play an essential role in regulating neuroinflammation by removing foreign materials and debris and in cognition by pruning synapses. Since liver X receptor β (LXRβ) has been identified as a regulator of microglial homeostasis, this study examined whether its removal from microglia affects neuroinflammation and cognitive function. We used a cell-specific tamoxifen-inducible Cre-loxP-mediated recombination to remove LXRβ from microglia specifically. We now report that ablation of LXRβ in microglia in early postnatal life led to a reduction in microglial numbers, distinct morphological changes indicative of microglial activation, and enhanced synapse engulfment accompanied by cognitive deficits. Removal of LXRβ from microglia in adult mice caused no cognitive defects. RNAseq analysis of microglia revealed that loss of LXRβ led to reduced expression of SAll1, a master regulator of microglial homeostasis, while increasing expression of genes associated with microglial activation and CNS disease. This study demonstrates distinctly different functions of microglial LXRβ in developing and adult mice and points to long-term consequences of defective LXRβ signaling in microglia in early life.

We have reported that mice in which the liver X receptor β (LXRβ) gene is inactivated lose dopaminergic neurons in the substantia nigra and motor neurons in the ventral horn of the spinal cord. These mice develop progressive hind limb paralysis starting at 6 months of age. Since LXRβ is not expressed in either dopaminergic neurons or motor neurons, we have focused on LXRβ-expressing cells whose function is essential for neuron survival. We now report defects in oligodendrocyte maturation in the absence of LXRβ. At 4 months of age, long before motor neuron loss occurs, there was reduction in expression of the four following genes in oligodendrocytes: The monocarboxylate transporter 1 (MCT1), which is essential for metabolic support of motor neurons; BDNF, a motor neuron trophic factor; 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR), a rate-limiting enzyme in cholesterol synthesis; glutamine synthetase (GS), an enzyme crucial for the elimination of neurotoxic glutamate from synapses. Differentiation of ES cells from WT and LXRβ−/− mice into motor neurons/oligodendrocytes revealed that LXRβ−/− cultures showed less arborization of motor neurons and a reduced proportion of mature oligodendrocytes. Our study suggests that defects in glial cells can have profound effects on neuronal survival and that early defective oligodendrocyte maturation can lead to motor neuron death. The expression of LXRβ in oligodendrocytes should be investigated as a target for preventing neuronal loss in diseases such as amyotrophic lateral sclerosis (ALS) and Parkinson’s disease.

Brown adipose tissue (BAT) plays a key role in metabolic homeostasis through its thermogenic effects and the secretion of regulatory molecules. Here we report that RAP250 haploinsufficiency stimulates BAT in mice, thus contributing to a decrease in fat accumulation. Local in vivo AAV-mediated RAP250 silencing in BAT reduces body weight and fat mass and enhances glucose oxidation, thereby indicating that RAP250 participates in the regulation of BAT metabolic activity. Analysis of the mechanisms led to the finding that Neuritin 1 is produced and released by brown adipocytes, it plays a key metabolic role, and it participates in the enhanced BAT metabolic activity under RAP250 deficiency. Forced overexpression of Neuritin 1 in UCP1-expressing cells markedly decreases fat mass and body weight gain in mice and induces the expression of thermogenic genes in BAT. Neuritin 1-deficient brown adipocytes also shows a reduced β-adrenergic response. We demonstrate a metabolic role of BAT-derived Neuritin 1 acting through an autocrine/paracrine mechanism. Based on our results, Neuritin-1 emerges as a potential target for the treatment of metabolic disorders.

Estrogen receptor β (ERβ) plays an important role in both the mouse and human prostate. The endogenous ligand for ERβ is the dihydrotestosterone metabolite, 5β-androstane-3β, 17β-diol (3β-Adiol). Thus, treatment with 5-α reductase inhibitor (5-ARI) should produce a phenotype similar to that seen in ERβ-/- mice. By comparing RNA-Seq of the ventral prostates (VP) of ERβ knockout mice (ERβcrispr-/-) and wild-type (WT) mice, we confirmed that ERβ modulates androgen receptor (AR) signaling indirectly by suppressing AR coactivators. Compared to WT mice, basal cell genes from ERβcrispr-/- mouse VP were significantly upregulated. A population of abnormal basal cells coexpressing P63 and AR was identified in the ERβcrispr-/- mouse VP by immunohistochemistry. In men treated with 5-ARI for treatment of benign prostatic hyperplasia (BPH), there was induction of a P63-positive intermediate cell population characterized by down regulation of Krt14 without significant change in the expression of Krt15, upregulation of AR and NKX3.1, and increased proliferation. In both VP of aging ERβcrispr-/- mice and in human prostates after 5-ARI treatment, there was substantial immune infiltration. Testosterone treatment inhibited immune infiltration in the VP of ERβcrispr-/- mice. We conclude that ERβ is a gene critical in maintaining normal basal cells and modulating immune environment in the prostate. Its loss leads to histological changes suggesting prostatitis and increases the number of intermediate cells, which are considered to be the cells of origin of prostate cancers. We suggest that an ERβ agonist could protect against 5-ARI-induced inflammatory cell infiltration and defects in the basal cell layer in BPH.

Triple-negative breast cancer (TNBC) is a subtype of breast cancer with aggressive behavior and poor prognosis. Current therapeutic options available for TNBC patients are primarily chemotherapy. With our evolving understanding of this disease, novel targeted therapies, including poly ADP-ribose polymerase (PARP) inhibitors, antibody-drug conjugates, and immune-checkpoint inhibitors, have been developed for clinical use. Previous reports have demonstrated the essential role of estrogen receptor β (ERβ) in TNBC, but the detailed molecular mechanisms downstream ERβ activation in TNBC are still far from elucidated. In this study, we demonstrated that a specific ERβ agonist, LY500307, potently induces R-loop formation and DNA damage in TNBC cells. Subsequent interactome experiments indicated that the residues 151 to 165 of U2 small nuclear RNA auxiliary factor 1 (U2AF1) and the Trp439 and Lys443 of ERβ were critical for the binding between U2AF1 and ERβ. Combined RNA sequencing and ribosome sequencing analysis demonstrated that U2AF1-regulated downstream RNA splicing of 5-oxoprolinase (OPLAH) could affect its enzymatic activity and is essential for ERβ-induced R-loop formation and DNA damage. In clinical samples including 115 patients from The Cancer Genome Atlas (TCGA) and 32 patients from an in-house cohort, we found a close correlation in the expression of ESR2 and U2AF1 in TNBC patients. Collectively, our study has unraveled the molecular mechanisms that explain the therapeutic effects of ERβ activation in TNBC, which provides rationale for ERβ activation-based single or combined therapy for patients with TNBC.

Uncontrolled regeneration leads to neoplastic transformation1-3. The intestinal epithelium requires precise regulation during continuous homeostatic and damage-induced tissue renewal to prevent neoplastic transformation, suggesting that pathways unlinking tumour growth from regenerative processes must exist. Here, by mining RNA-sequencing datasets from two intestinal damage models4,5 and using pharmacological, transcriptomics and genetic tools, we identified liver X receptor (LXR) pathway activation as a tissue adaptation to damage that reciprocally regulates intestinal regeneration and tumorigenesis. Using single-cell RNA sequencing, intestinal organoids, and gain- and loss-of-function experiments, we demonstrate that LXR activation in intestinal epithelial cells induces amphiregulin (Areg), enhancing regenerative responses. This response is coordinated by the LXR-ligand-producing enzyme CYP27A1, which was upregulated in damaged intestinal crypt niches. Deletion of Cyp27a1 impaired intestinal regeneration, which was rescued by exogenous LXR agonists. Notably, in tumour models, Cyp27a1 deficiency led to increased tumour growth, whereas LXR activation elicited anti-tumour responses dependent on adaptive immunity. Consistently, human colorectal cancer specimens exhibited reduced levels of CYP27A1, LXR target genes, and B and CD8 T cell gene signatures. We therefore identify an epithelial adaptation mechanism to damage, whereby LXR functions as a rheostat, promoting tissue repair while limiting tumorigenesis.

OBJECTIVE:To study the role of estrogen receptor β in follicle development and maturation and the response to gonadotropin stimulation aiming at superovulation. DESIGN:Experimental study and transcriptomic analysis. SETTING:Karolinka Institutet, medical university. ANIMAL(S):Healthy wild-type (WT) and estrogen receptor β knockout (Esr2-KO) female mice undergoing superovulation at 4 weeks, 7 weeks, and 6 months of age. INTERVENTION(S):Not applicable. MAIN OUTCOME MEASURE(S):Oocyte yield after superovulation, transcriptomic profiling of cumulus-granulosa cell complexes and oocytes, and immunohistochemical analyses. RESULT(S):Superovulation of estrogen receptor β (ERβ) knockout mice resulted in reduced oocyte yield at 6 months of age compared with WT mice, but younger mice had similar yields. RNA-seq analysis of cumulus cells from superovulated WT and Esr2-KO mice identified genes and pathways associated with among others adhesion, proliferation, Wnt-signaling, and placed ERβ in bipotential granulosa cell cluster. Loss of ERβ increased expression of the other estrogen receptors Esr1 and Gper1. CONCLUSION(S):Our results show that ERβ has an important role in regulating ovulation in response to exogenous gonadotropins in 6-month-old mice, but not in younger mice. Our transcriptomic and immunohistochemical observations suggest a dysregulation of the granulosa cell communication and lack of tight coordination between granulosa cell replication and antrum expansion. A significant upregulation of other estrogen receptors may support a compensatory mechanism sustaining fertility during younger age in Esr2-KO mice.

Liver X receptors (LXRs), particularly LXRβ, are emerging as crucial players in the translation of basic neuroscience to clinical psychiatry. These nuclear receptor transcription factors, initially known for their roles in cholesterol metabolism and inflammation, are now revealing promising connections between molecular mechanisms and psychiatric symptoms. This review highlights recent breakthroughs in understanding LXRβ's regulation and function in behaviors relevant to depression and anxiety, derived from studies using animal paradigms that capture specific features of these disorders. We explore how these preclinical findings are shaping our comprehension of mood-related behaviors at the molecular level and potentially paving the way for innovative therapeutic strategies. As a ligand-activated transcription factor, LXRβ represents a novel target for drug development, potentially bridging the gap between bench discoveries and bedside treatments for neuropsychiatric disorders. We discuss the challenges and opportunities in translating LXRβ research into clinical interventions, emphasizing the potential for personalized medicine approaches in psychiatry. This bench-to-bedside article underscores the importance of LXRβ research in advancing our understanding and treatment of complex mental health conditions, while acknowledging the nuanced interpretation required when extrapolating from animal studies to human disorders.

The role of thyroid hormone (TH) in the development and function of the central nervous system (CNS) has been known for many years. However, the role of liver X receptors (LXRs) in TH function and protection against neuronal degeneration was not recognized until recently. The relationship between thyroid hormone receptors (TRs) and LXRs became apparent with the cloning of steroid hormone receptors, leading to the discovery of the nuclear receptor superfamily. This family includes not only receptors for classical steroid hormones but also many newly discovered ligand-activated nuclear receptors. LXRs and TRs regulate overlapping pathways in lipid and carbohydrate metabolism, as well as in overall CNS development and function. These CNS pathways include neuronal migration during cortical and cerebellar layering, myelination, oligodendrocyte maturation, microglial activation, and astrocyte functions. Furthermore, LXRs likely have unique functions, as evidenced by the inability of TH to compensate for microglial activation, oligodendrocyte maturation, spinal motor neuron death, and degeneration of retinal and cochlear neurons in LXRβ knockout mice. The common and unique functions of these two receptors are the subject of this review. We analyzed some of the most relevant literature on the regulation and function of LXRs and TRs and investigated why both receptors are required in the human body. We conclude that LXRs and TRs do not represent parallel pathways but rather constitute a single pathway through which the TH endocrine system regulates cholesterol homeostasis. Subsequently, LXRs, activated by cholesterol metabolites, function as a paracrine/autocrine system that modulates the target cell response to TH.

Supplementary Methods and Figures 1-12 from Different Roles of Estrogen Receptors α and β in the Regulation of E-Cadherin Protein Levels in a Mouse Mammary Epithelial Cell Line

PDF file - 693K, S2. ERbeta1 reduces cell proliferation in NSCLC cells.

Renal fibrosis (RF) is a common pathway leading to chronic kidney disease (CKD), which lacks effective treatment. While estrogen receptor beta (ERβ) is known to be present in the kidney, its role in RF remains unclear. The present study aimed to investigate the role and underlying mechanism of ERβ during RF progression in patients and animal models with CKD. We found that ERβ was highly expressed in the proximal tubular epithelial cells (PTECs) in healthy kidneys but its expression was largely lost in patients with immunoglobin A nephropathy (IgAN) and in mice with unilateral ureter obstruction (UUO) and subtotal nephrectomy (5/6Nx). ERβ deficiency markedly exacerbated, whereas ERβ activation by WAY200070 and DPN attenuated RF in both UUO and 5/6Nx mouse models, suggesting a protective role of ERβ in RF. In addition, ERβ activation inhibited TGF-β1/Smad3 signaling, while loss of renal ERβ was associated with overactivation of the TGF-β1/Smad3 pathway. Furthermore, deletion or pharmacological inhibition of Smad3 prevented the loss of ERβ and RF. Mechanistically, activation of ERβ competitively inhibited the association of Smad3 with the Smad-binding element, thereby downregulating the transcription of the fibrosis-related genes without altering Smad3 phosphorylation in vivo and in vitro. In conclusion, ERβ exerts a renoprotective role in CKD by blocking the Smad3 signaling pathway. Thus, ERβ may represent as a promising therapeutic agent for RF.

Liver X receptors α and β are members of the nuclear receptor family, which comprise a flexible N-terminal domain, a DNA binding domain, a hinge linker, and a ligand binding domain. Liver X receptors are important regulators of cholesterol and lipid homeostasis by controlling the transcription of numerous genes. Key to their transcriptional role is synergetic interaction among the domains. DNA binding domain binds on DNA; ligand binding domain is a crucial switch to control the transcription activity through conformational change caused by ligand binding. The Liver X receptors form heterodimers with retinoid X receptor and then the liganded heterodimer may recruit other necessary transcription components to form an active transcription complex.

Supplementary Figures 1-4, Tables 1-2 from RBCK1 Drives Breast Cancer Cell Proliferation by Promoting Transcription of Estrogen Receptor α and Cyclin B1

Supplementary Table 1 from Tumor Repressive Functions of Estrogen Receptor β in SW480 Colon Cancer Cells

Liver X receptors (LXRαβ) play essential roles in the maintenance of the normal functions of macrophages, in modulation of immune system responses and cholesterol homeostasis. We have reported that LXRαβ-/- mice develop squamous cell lung cancer. We now report that those LXRαβ-/- mice, which live to 18-months of age, spontaneously develop a second type of lung cancer resembling a rare subtype of NSCLC (TTF-1 and P63-positive). The lesions are characterized as follows: a high proliferation rate; a marked accumulation of abnormal macrophages; an increase in the number of regulatory T cells; a remarkably low level of CD8+ cytotoxic T lymphocytes; enhanced TGFβ signaling; an increased expression of matrix metalloproteinases accompanied by degradation of lung collagen; and a loss of estrogen receptor β (ERβ). Because NSCLC is associated with cigarette smoking, we investigated the possible links between loss of LXRαβ and CS. A Kaplan-Meier Plotter database revealed reduced expression of LXRαβ and ERβ was correlated with low overall survival (OS). Thus, reduction of LXRαβ expression by cigarette smoking may be one mechanism through which CS causes lung cancer. The possibility that maintenance of LXRαβ and ERβ signaling could be used in the treatment of NSCLC needs further investigation.

Abstract Non–small cell lung cancer (NSCLC) is the leading cause of cancer-related deaths worldwide. In addition to the aberrant growth factor signaling, dysregulation of other pathways, such as those mediated by estrogens and their receptors, has been linked to NSCLC initiation and progression. Although the expression of wild-type estrogen receptor β (ERβ1) has been associated with prolonged disease-free survival in patients with NSCLC, the molecular mechanism that accounts for this correlation is unknown. Here, upregulation of ERβ1 reduced proliferation and enhanced apoptosis in the context of mutant RAS. ERβ1 was found to induce apoptosis by stimulating the intrinsic apoptotic pathway that involves BIM, a Bcl-2 proapoptotic family member that is regulated by the extracellular signal–regulated kinase (ERK). Downregulation of EGFR and inactivation of RAS and the downstream components ERK1/2 were found to be involved in the ERβ1-induced apoptosis. Manipulation of EGFR and RAS expression and activity in ERβ1-expressing cells revealed the central role of oncogenic RAS inhibition in the ERβ1-mediated proapoptotic phenotype and EGFR regulation. These results demonstrate that ERβ1 decreases the survival of NSCLC cells by regulating oncogenic RAS signaling. Implications: The ability of ERβ1 to regulate the oncogenic functions of RAS suggests its importance in the biology of NSCLC and its clinical management. Mol Cancer Res; 12(6); 843–54. ©2014 AACR.

Supplementary Table 3 from Genome-Wide Mapping of Estrogen Receptor-β–Binding Regions Reveals Extensive Cross-Talk with Transcription Factor Activator Protein-1