The nuclear receptor superfamily: the second decade

Structural study and expression of the androgen receptors during the reproductive cycle in the Harderian gland of the male Meriones libycus

The goal of this study was to evaluate for the first time the expression of the androgen receptors (AR) in Harderian glands (HG) of the male Meriones lybicus in relation to the reproductive cycle. Six male Harderian glands of the resting period and 6 of the breeding period were collected. The animals were trapped in the desert of Béni Abbès (Algeria). The morphology of the Harderian glands was studied by light microscopy and morphometry, whereas the expression of the androgen receptors was assessed and quantified based on immunohistochemistry techniques. We have shown that the Harderian glands of Meriones libycus are tubuloalveolar glands with wide lumen. The glandular epithelium is composed of two types of cells (types I and II) in the resting season and three types of cells (types I, II and III) in the breeding season. These three types of cells differ in size and shape. Type-I cells have a prismatic shape, an acidophilic cytoplasm, and small lipidic vacuoles, whereas type-II ones are pyramidal in shape, with basophilic cytoplasm. Type-III cells resemble those of type I, and so they are prismatic in shape and have an acidophilic cytoplasm with larger lipidic vacuoles. The immunoreactivity of type-I and type-III cells was mainly cytoplasmic and the intensity of the immunostaining was significantly higher during the breeding season. Among other functions, the Harderian gland seems to be involved in the production of pheromones under the effect of androgens.

iNR-2L: A two-level sequence-based predictor developed via Chou's 5-steps rule and general PseAAC for identifying nuclear receptors and their families

Nuclear receptor proteins (NRPs) perform a vital role in regulating gene expression. With the rapidity growth of NRPs in post-genomic era, it is highly recommendable to identify NRPs and their sub-families accurately from their primary sequences. Several conventional methods have been used for discrimination of NRPs and their sub-families, but did not achieve considerable results. In a sequel, a two-level new computational model "iNR-2 L" is developed. Two discrete methods namely: Dipeptide Composition and Tripeptide Composition were used to formulate NRPs sequences. Further, both the descriptor spaces were merged to construct hybrid space. Furthermore, feature selection technique minimum redundancy and maximum relevance was employed in order to select salient features as well as reduce the noise and redundancy. The experiential outcomes exhibited that the proposed model iNR-2 L achieved outstanding results. It is anticipated that the proposed computational model might be a practical and effective tool for academia and research community.

A Novel Discovery: Holistic Efficacy at the Special Organ Level of Pungent Flavored Compounds from Pungent Traditional Chinese Medicine

Pungent traditional Chinese medicines (TCMs) play a vital role in the clinical treatment of hepatobiliary disease, gastrointestinal diseases, cardiovascular diseases, diabetes, skin diseases and so on. Pungent TCMs have a vastness of pungent flavored (with pungent taste or smell) compounds. To elucidate the molecular mechanism of pungent flavored compounds in treating cardiovascular diseases (CVDs) and liver diseases, five pungent TCMs with the action of blood-activating and stasis-resolving (BASR) were selected. Here, an integrated systems pharmacology approach is presented for illustrating the molecular correlations between pungent flavored compounds and their holistic efficacy at the special organ level. First, we identified target proteins that are associated with pungent flavored compounds and found that these targets were functionally related to CVDs and liver diseases. Then, based on the phenotype that directly links human genes to the body parts they affect, we clustered target modules associated with pungent flavored compounds into liver and heart organs. We applied systems-based analysis to introduce a pungent flavored compound-target-pathway-organ network that clarifies mechanisms of pungent substances treating cardiovascular diseases and liver diseases by acting on the heart/liver organ. The systems pharmacology also suggests a novel systematic strategy for rational drug development from pungent TCMs in treating cardiovascular disease and associated liver diseases.

Activation of liver X receptor promotes fatty acid synthesis in goat mammary epithelial cells via modulation of SREBP1 expression

In bovine mammary tissue and cells, liver X receptor (LXR) regulates lipid synthesis mainly via transactivation of the transcription factor sterol regulatory element binding protein 1 (SREBP1). In the present work, we investigated the role of LXR in controlling lipid synthesis via transactivation of SREBP1 in goat primary mammary cells (GMEC). The GMEC were treated with a synthetic agonist of LXR, T0901317, and transactivation and transcription of SREBP1, expression of lipogenic genes, and fatty acid profiling and triacylglycerol (TAG) content of the cells were measured. A mild increase in the mRNA expression level of LXRα (NR1H3) was observed following treatment with different concentrations of T0901317, and a dose-dependent increase in mRNA and transactivation of SREBP1 was detected. Activation of LXR resulted in a significant increase in the mRNA expression of most of the measured genes related to de novo synthesis, desaturation, and transport of fatty acids; TAG synthesis; and transcription regulators. Compared with the control, total content of cellular TAG increased by more than 20% with T0901317 treatment. Furthermore, addition of T0901317 increased the proportion of unsaturated fatty acids (e.g., C16:1, C18:1, C20:1, and C22:1), and decreased the proportion of saturated fatty acids (e.g., C16:0, C18:0, C20:0, and C22:0). These results provide evidence that LXR regulates the expression and activity of SREBP1. Our results indicated that LXR participate in regulating the transcription of genes involved in milk fat synthesis in GMEC in an SREBP1-dependent fashion.

Enabling precision medicine by unravelling disease pathophysiology: quantifying signal transduction pathway activity across cell and tissue types

Signal transduction pathways are important in physiology and pathophysiology. Targeted drugs aim at modifying pathogenic pathway activity, e.g., in cancer. Optimal treatment choice requires assays to measure pathway activity in individual patient tissue or cell samples. We developed a method enabling quantitative measurement of functional pathway activity based on Bayesian computational model inference of pathway activity from measurements of mRNA levels of target genes of the pathway-associated transcription factor. Oestrogen receptor, Wnt, and PI3K-FOXO pathway assays have been described previously. Here, we report model development for androgen receptor, Hedgehog, TGFβ, and NFκB pathway assays, biological validation on multiple cell types, and analysis of data from published clinical studies (multiple sclerosis, amyotrophic lateral sclerosis, contact dermatitis, Ewing sarcoma, lymphoma, medulloblastoma, ependymoma, skin and prostate cancer). Multiple pathway analysis of clinical prostate cancer (PCa) studies showed increased AR activity in hyperplasia and primary PCa but variable AR activity in castrate resistant (CR) PCa, loss of TGFβ activity in PCa, increased Wnt activity in TMPRSS2:ERG fusion protein-positive PCa, active PI3K pathway in advanced PCa, and active PI3K and NFκB as potential hormonal resistance pathways. Potential value for future clinical practice includes disease subtyping and prediction and targeted therapy response prediction and monitoring.

Estradiol receptor profile and estrogen responsiveness in laryngeal cancer and clinical outcomes

There is growing evidence that laryngeal cancers are responsive to sex hormones, specifically 17β-estradiol (E₂), despite controversy regarding the presence and characterization of E₂ receptors (ER). Determination of sex hormone responsiveness impacts the prognosis of laryngeal cancer patients and the treatment modalities implemented by their clinicians. Discovery of membrane-associated steroid hormone receptors and rapid membrane signaling opened the possibility that cancers previously labeled 'non-hormone dependent' and 'ER negative' might in fact be susceptible to the effects of E₂ via these membrane receptors. ERα66 and ERβ, the classical nuclear receptors, are present in the membranes of different cancer cells via a mechanism referred to as trafficking. Novel splice variants of these traditional receptors, a key example being ERα36, have also been found in the caveolae of cancer cells. Previous work demonstrated that ERα36 has a role in the tumorigenesis of laryngeal cancer, enhancing both proliferation and the anti-apoptotic effect of E₂ against chemotherapeutics. The present study showed that expression of different membrane ERs in laryngeal cancer is not uniform, which may result in differential and even antagonistic responses to E₂. E₂ had protective or deleterious effects in different cancer cell lines, stimulating proliferation and conferring anti-apoptotic potential to the cancer cells according to their receptor profile. These findings stress the importance of establishing the molecular and clinical characterization of the specific laryngeal tumor in order to tailor treatment accordingly, thus optimizing care while reducing adverse effects for individual patients.

phyB Interacts with BES1 to Regulate Brassinosteroid Signaling in Arabidopsis

Light is an important environmental factor, which mainly inhibits hypocotyl elongation through various photoreceptors. In contrast, brassinosteroids (BRs) are major hypocotyl elongation-promoting hormones in plants, which could optimize photomorphogenesis concurrent with external light. However, the precise molecular mechanisms underlying the antagonism of light and BR signaling remain largely unknown. Here we show that the Arabidopsis red light receptor phyB is involved in inhibition of BR signaling via its direct interaction with the BR transcription factor BES1. In our study, the phyB mutant displays BR hypersensitivity, which is repressed in transgenic plants overexpressing phyB, suggesting that phyB negatively regulates the BR signaling pathway. In addition, protein interaction results show that phyB directly interacts with dephosphorylated BES1, the physiologically active form of BES1 induced by BR, in a red light-dependent manner. Genetic analyses suggest that phyB may act partially through BES1 to regulate BR signaling. Transcriptomic data and quantitative real-time PCR assay further show that phyB-mediated red light inhibits BR signaling by repressing expression of BES1 target genes, including the BR biosynthesis genes DWF4, the SAUR family and the PRE family genes required for promoting cell elongation. Finally, we found that red light treatment inhibits the DNA-binding activity of BES1 and photoactivated phyB represses the transcriptional activity of BES1 under red light. Taken together, we suggest that the interaction of phyB with dephosphorylated BES1 may allow plants to balance light and BR signaling by repressing transcriptional activity of BES1 to regulate expression of its target genes.

Important candidate genes for abdominal fat content identified by linkage disequilibrium and fixation index information

Selection for rapid growth in chickens has always been accompanied by increased fat deposition and excessive fat deposition, especially abdominal fat, cannot only decrease feed efficiency but also cause many diseases. Finding the candidate genes associated with abdominal fat deposition is essential for breeding. To identify these candidate genes, we applied linkage disequilibrium and selection signature analysis using chicken 60 k single nucleotide polymorphism (SNP) chips in two broiler lines divergently selected for abdominal fat content for 11 generations. After quality control, 46,033 SNPs were left for analysis. Using these SNPs, we found that r2 was 0.06 to 0.14 in the lean line and 0.07 to 0.13 in the fat line for all 28 chromosomes (except GGA16). Pairwise SNP distances <25 kb showed a mean r2 = 0.33 in the lean line and r2 = 0.32 in the fat line. The fixation index (FST) analysis was carried out and 46 SNPs with the top 0.1% of the FST value was detected as the loci with selection signatures. Besides FST, hapFLK was also used to detect selection signatures for abdominal fat content. A total of 11 genes, including transient receptor potential cation channel subfamily C member 4, estrogen related receptor gamma, fibroblast growth factor 13, G-protein-signaling modulator 2, RAR related orphan receptor A, phospholipase A2 group X, mitochondrial ribosomal protein L28, metadherin, calcitonin receptor like receptor, serine/threonine kinase 39, and nuclear factor I A, were detected as the important candidate genes for abdominal fat deposition based on their basic functions. The results of the present study may benefit the understanding of genetic mechanism of abdominal fat deposition in chicken.

Steroidal pheromones and their potential target sites in the vomeronasal organ

Steroids are important olfactory signals in most mammalian species. The vomeronasal organ has been suspected to be the primary target of pheromones. In rat vomeronasal sensory neurons express steroid binding proteins and nuclear receptors. Some binding globulins were found also in single ciliated cells of the non-sensory vomeronasal epithelium. Immunoelectron microscopy revealed VDR in olfactory microvilli and DPB in apical membrane protrusions of supporting sells within the sensory epithelium. Pilot behavioral studies with dogs showed increased sniffing duration upon exposure to low concentrations of vitamin D while higher concentrations were less effective. It has been shown that vitamin D has pheromone-like properties in lizards. Our histochemical and behavioral observations indicate that the mammalian vomeronasal organ may be a vitamin D target. Olfactory functions of vitamin D involve most likely rapid membrane mediated effects rather than actions through nuclear receptors.

Unraveling the Function of Lemur Tyrosine Kinase 2 Network

Lemur Tyrosine Kinase 2 (LMTK2) is a recently cloned transmembrane protein, actually a serine/threonine kinase named after the Madagascar primate lemur due to the long intracellular C-terminal tail. LMTK2 is relatively little known, compared to other kinases but its role has been increasingly recognized. Published data show that LMTK2 regulates key cellular events, including endocytic trafficking, nerve growth factor signaling, apoptosis, and Cl- transport. Abnormalities in the expression and function of LMTK2 are associated with human disease, such as neurodegeneration, cancer and infertility. We summarized the current state of knowledge on LMTK2 structure, regulation, interactome, intracellular localization, and tissue expression and point out future research directions to better understand the role of LMTK2.

Unraveling the Regulation of Hepatic Gluconeogenesis

Hepatic gluconeogenesis, de novo glucose synthesis from available precursors, plays a crucial role in maintaining glucose homeostasis to meet energy demands during prolonged starvation in animals. The abnormally increased rate of hepatic gluconeogenesis contributes to hyperglycemia in diabetes. Gluconeogenesis is regulated on multiple levels, such as hormonal secretion, gene transcription, and posttranslational modification. We review here the molecular mechanisms underlying the transcriptional regulation of gluconeogenesis in response to nutritional and hormonal changes. The nutrient state determines the hormone release, which instigates the signaling cascades in the liver to modulate the activities of various transcriptional factors through various post-translational modifications like phosphorylation, methylation, and acetylation. AMP-activated protein kinase (AMPK) can mediate the activities of some transcription factors, however its role in the regulation of gluconeogenesis remains uncertain. Metformin, a primary hypoglycemic agent of type 2 diabetes, ameliorates hyperglycemia predominantly through suppression of hepatic gluconeogenesis. Several molecular mechanisms have been proposed to be metformin's mode of action.

Nuclear Receptors in the Pathogenesis and Management of Inflammatory Bowel Disease

Nuclear receptors (NRs) are ligand-dependent transcription factors that regulate the transcription of target genes. Previous epidemiological and genetic studies have documented the association of NRs with the risk of inflammatory bowel disease (IBD). Although the mechanisms of action of NRs in IBD have not been fully established, accumulating evidence has demonstrated that NRs play complicated roles in regulating intestinal immunity, mucosal barriers, and intestinal flora. As one of the first-line medications for the treatment of IBD, 5-aminosalicylic acid (5-ASA) activates peroxisome proliferator-activated receptor gamma (PPARγ) to attenuate colitis. The protective roles of rifaximin and rifampicin partly depend on promoting pregnane X receptor (PXR) expression. The aims of this review are to discuss the roles of several important NRs, such as PPARγ, PXR, vitamin D receptor (VDR), farnesoid X receptor (FXR), and RAR-related orphan receptor gammat (RORγt), in the pathogenesis of IBD and management strategies based on targeting these receptors.

Involvement of epigenetic modifications in thyroid hormone-dependent formation of adult intestinal stem cells during amphibian metamorphosis

Amphibian metamorphosis has long been used as model to study postembryonic development in vertebrates, a period around birth in mammals when many organs/tissues mature into their adult forms and is characterized by peak levels of plasma thyroid hormone (T3). Of particular interest is the remodeling of the intestine during metamorphosis. In the highly-related anurans Xenopus laevis and Xenopus tropicalis, this remodeling process involves larval epithelial cell death and de novo formation of adult stem cells via dedifferentiation of some larval cells under the induction of T3, making it a valuable system to investigate how adult organ-specific stem cells are formed during vertebrate development. Here, we will review some studies by us and others on how T3 regulates the formation of the intestinal stem cells during metamorphosis. We will highlight the involvement of nucleosome removal and a positive feedback mechanism involving the histone methyltransferases in gene regulation by T3 receptor (TR) during this process.

A retinoid X receptor partial agonist attenuates pulmonary emphysema and airway inflammation

Background

Retinoid X receptors (RXRs) are members of the nuclear receptor (NR) superfamily that mediate signalling by 9-cis retinoic acid, a vitamin A derivative. RXRs play key roles not only as homodimers but also as heterodimeric partners, e.g., for retinoic acid receptors, vitamin D receptors, and peroxisome proliferator-activated receptors. The NR family may also play important roles in the development of emphysema. However, the role of RXRs in the pathogenesis of emphysema is not well defined.

Methods

We developed a novel RXR partial agonist (NEt-4IB) and investigated its effect and mechanism compared to a full agonist (bexarotene) in a murine model of emphysema. For emphysema induction, BALB/c mice received intraperitoneal cigarette smoke extract (CSE) or intratracheal porcine pancreas elastase (PPE). Treatment with RXR agonists was initiated before or after emphysema induction.

Results

Treatment with NEt-4IB significantly suppressed the increase in static lung compliance and emphysematous changes in CSE-induced emphysema and PPE-induced established and progressive emphysema. NEt-4IB significantly suppressed PPE-induced neutrophilic airway inflammation and the levels of keratinocyte chemoattractant (KC), C-X-C motif ligand5 (CXCL5), interferon (IFN)-γ and IL-17. NEt-4IB also improved the matrix metalloproteinase-9 (MMP-9)/tissue inhibitor of metalloproteinase-1 (TIMP-1) imbalance and the reduced anti-oxidant activity in bronchoalveolar lavage (BAL) fluid. NEt-4IB suppressed PPE-induced vascular endothelial growth factor (VEGF) expression in the airway. Treatment with NEt-4IB and bexarotene significantly suppressed the increase in static lung compliance and emphysematous changes. However, adverse effects of RXR agonists, including hypertriglyceridemia and hepatomegaly, were observed in bexarotene-treated mice but not in NEt-4IB-treated mice.

Conclusion

These data suggest that RXRs play crucial roles in emphysema and airway inflammation, and novel partial RXR agonists could be potential therapeutic strategies for the treatment of PPE- and CSE-induced emphysema.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0963-0) contains supplementary material, which is available to authorized users.

MicroRNA-449a Inhibits Tumor Metastasis through AKT/ERK1/2 Inactivation by Targeting Steroid Receptor Coactivator (SRC) in Endometrial Cancer

Endometrial cancer represents the leading frequency in gynecological malignancy in developed countries. Even with early detection, metastasis and recurrence remain the main reasons for a high death rate. MicroRNA-449a (miR-449a) has been reported to function as a tumor suppressor, yet the role of miR-449a in endometrial cancer metastasis has not been investigated. The present study identified that miR-449a was downregulated in advanced endometrial cancer. Overexpression of miR-449a decreased the migration and invasion of KLE and AN3CA endometrial cancer cells. Using luciferase reporter assays, we identified that miR-449a directly targeted the steroid receptor coactivator (SRC) by binding to sites in the 3' untranslated regions. Elevated expressions of SRC have been witnessed in advanced endometrial cancer tissues and have promoted tumor metastasis. We also identified that the suppressive effect of miR-449a on metastasis could be mediated by downregulating SRC and that miR-449a could suppress AKT and ERK1/2 pathway activation in endometrial cancer cells. These findings contribute to the current understanding of the function of miR-449a in endometrial cancer.

Ginger: A Novel Strategy to Battle Cancer through Modulating Cell Signalling Pathways: A Review

Numerous studies have been performed in understanding the development of cancer. Though, the mechanism of action of genes in the development of cancer remains to be explained. The current mode of treatment of cancer shows adverse effects on normal cells and also alter the cell signalling pathways. However, ginger and its active compound have fascinated research based on animal model and laboratories during the past decade due to its potentiality in killing cancer cells. Ginger is a mixture of various compounds including gingerol, paradol, zingiberene and shogaol and such compounds are the main players in diseases management. Most of the health-promoting effects of ginger and its active compound can be attributed due to its antioxidant and anti-tumour activity. Besides, the active compound of ginger has proven its role in cancer management through its modulatory effect on tumour suppressor genes, cell cycle, apoptosis, transcription factors, angiogenesis and growth factor. In this review, the role of ginger and its active compound in the inhibition of cancer growth through modulating cell signalling pathways will be reviewed and discussed.

The LPS/D-Galactosamine-Induced Fulminant Hepatitis Model to Assess the Role of Ligand-Activated Nuclear Receptors on the NLRP3 Inflammasome Pathway In Vivo

The NLRP3 inflammasome is a cellular sensor of danger signals such as extracellular ATP or abnormally accumulating molecules like crystals. Activation of NLRP3 by such compounds triggers a sterile inflammatory response that may be involved in numerous pathologies including rheumatoid arthritis, atherosclerosis, diabetes, and Alzheimer's disease. A better understanding of the mechanisms that govern NLRP3 inflammasome activation is an important step toward the development of novel therapeutic strategies to dampen over-activation of the immune system. Recent findings demonstrate that ligand-activated nuclear receptors regulate the NLRP3 inflammasome pathway, thus representing possible therapeutic targets. It is therefore important to assess the potential of these putative targets in the regulation of the NLRP3 inflammasome activation in the most appropriate pathophysiological models. Fulminant hepatitis (FH) results from massive hepatocyte apoptosis, hemorrhagic necrosis, and inflammation. Low doses of LPS in combination with the specific hepatotoxic agent D-galactosamine (D-GalN) promote liver injury in mice and induce the production of inflammatory cytokines associated with increased NLRP3 protein and caspase 1 activity, thus recapitulating the clinical picture of FH in humans. We provide a simple method to examine the involvement of nuclear receptors in NLRP3-driven fulminant hepatitis, consisting in the induction of FH, in the isolation of liver macrophages, and in the extraction and analysis of RNA content.

Proteomics to Predict Loss of RXR-γ During Progression of Epithelial Ovarian Cancer

Retinoid and rexinoid receptors are known to regulate key processes during development, differentiation, and cell death in vertebrates. However, their contributions to progression of malignant disease remain largely elusive although it is realized that transformed cancer cells, which essentially evade apoptosis, may display altered molecular expressions or functions associated with retinoid signaling. Here, using a progression model of ovarian cancer, we describe a proteomics-based approach including experimental procedures toward identification and validation of altered protein profiles during transformation. Effectively, this specifies loss of RXR-γ during progression of epithelial ovarian cancer.

Combined Androgen receptor blockade overcomes the resistance of breast cancer cells to palbociclib

The dysregulation of cyclin D -Cyclin-dependent kinase 4/6 (CDK4/6)-Rb axis has been implicated in breast cancer progression and the selective CDK4/6 inhibitors have shown effective activity in advanced breast cancer, especially in tumors driven by the estrogen receptor (ER). However, resistance to these small molecular inhibitors has become an inevitable clinical issue after their initial use. Here, we investigated the potential mechanism of resistance by establishing a CDK4/6 inhibitor palbociclib-resistant breast cancer cell line (MCF-7pR). After prolonged exposure to palbociclib, we detected the loss of the ER signaling and an increase in androgen receptor (AR). Moreover, we demonstrated more localization of AR in the cell nucleus of MCF-7pR compared to the parental cell (MCF-7). We also reported that AR could promote the progression of the cell cycle. Blockade of AR signaling could reduce the level of the relative G1-S cyclins, abolish Rb phosphorylation and inhibit the activation of transcriptional programs in S phase. Furthermore, dual inhibition of AR and CDK4/6 could reverse the resistance of palbociclib both in vitro and in vivo. In sum, our studies provide evidence that AR activation promotes cell cycle progression and cell proliferation in CDK4/6 inhibitor resistance, and identify AR inhibition as a putative novel therapeutic strategy to treat CDK4/6 inhibitor resistance in cancer.

Sex differences in the hypothalamic-pituitary-adrenal axis' response to stress: an important role for gonadal hormones

The hypothalamic-pituitary-adrenal (HPA) axis, a neuroendocrine network that controls hormonal responses to internal and external challenges in an organism's environment, exhibits strikingly sex-biased activity. In adult female rodents, acute HPA function following a stressor is markedly greater than it is in males, and this difference has largely been attributed to modulation by the gonadal hormones testosterone and estradiol. These gonadal hormones are produced by the hypothalamic-pituitary-gonadal (HPG) axis and have been shown to determine sex differences in adult HPA function after acute stress via their activational and organizational effects. Although these actions of gonadal hormones are well supported, the possibility that sex chromosomes similarly influence HPA activity is unexplored. Moreover, questions remain regarding sex differences in the activity of the HPA axis following chronic stress and the underlying contributions of gonadal hormones and sex chromosomes. The present review examines what is currently known about sex differences in the neuroendocrine response to stress, as well as outstanding questions regarding this sex bias. Although it primarily focuses on the rodent literature, a brief discussion of sex differences in the human HPA axis is also included.

Facial Sadness Recognition is Modulated by Estrogen Receptor Gene Polymorphisms in Healthy Females

Polymorphisms of the estrogen receptor ESR1 and ESR2 genes have been linked with cognitive deficits and affective disorders. The effects of these genetic variants on emotional processing in females with low estrogen levels are not well known. The aim was to explore the impact of the ESR1 and ESR2 genes on the responses to the facial emotion recognition task in females. Postmenopausal healthy female volunteers were genotyped for the polymorphisms Xbal and PvuII of ESR1 and the polymorphism rs1256030 of ESR2. The effect of these polymorphisms on the response to the facial emotion recognition of the emotions happiness, sadness, disgust, anger, surprise, and fear was analyzed. Females carrying the P allele of the PvuII polymorphism or the X allele of the Xbal polymorphism of ESR1 easily recognized facial expressions of sadness that were more difficult for the women carrying the p allele or the x allele. They displayed higher accuracy, fast response time, more correct responses, and fewer omissions to complete the task, with a large effect size. Women carrying the ESR2 C allele of ESR2 showed a faster response time for recognizing facial expressions of anger. These findings link ESR1 and ESR2 polymorphisms in facial emotion recognition of negative emotions.

The regulation of drug-metabolizing enzymes and membrane transporters by inflammation: Evidences in inflammatory diseases and age-related disorders

Drug-metabolizing enzymes (DMEs) and membrane transporters play important roles in the absorption, distribution, metabolism, and excretion processes that determine the pharmacokinetics of drugs. Inflammation has been shown to regulate the expression and function of these drug-processing proteins. Given that inflammation is a common feature of many diseases, in this review, the general mechanisms for inflammation-mediated regulation of DMEs and transporters are described. Also, evidences regarding the aberrant expression of these drug-processing proteins in several inflammatory diseases and age-related disorders are provided.

The evolving role of receptors as predictive biomarkers for metastatic breast cancer

INTRODUCTION

In breast cancer, estrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2) are essential biomarkers to predict response to endocrine and anti-HER2 therapies, respectively. In metastatic breast cancer, the use of these receptors and targeted therapies present additional challenges: temporal heterogeneity, together with limited sampling methodologies, hinders receptor status assessment, and the constant evolution of the disease invariably leads to resistance to treatment. Areas covered: This review summarizes the genomic abnormalities in ER and HER2, such as mutations, amplifications, translocations, and alternative splicing, emerging as novel biomarkers that provide an insight into underlying mechanisms of resistance and hold potential predictive value to inform treatment selection. We also describe how liquid biopsies for sampling of circulating markers and ultrasensitive detection technologies have emerged which complement ongoing efforts for biomarker discovery and analysis. Expert commentary: While evidence suggests that genomic aberrations in ER and HER2 could contribute to meeting the pressing need for better predictive biomarkers, efforts need to be made to standardize assessment methods and better understand the resistance mechanisms these markers denote. Taking advantage of emerging technologies, research in upcoming years should include prospective trials incorporating these predictors into the study design to validate their potential clinical value.

Current status of androgen receptor-splice variant 7 inhibitor niclosamide in castrate-resistant prostate-cancer

Castrate-Resistant Prostate-Cancer (CRPC) is one of the most common malignancies occurring in men. Unfortunately, even if several recently approved agents clinically improved the outcome of CRPC patients, none of these is curative especially for a splice version of the Androgen Receptor (AR) AR-V7, which is a variant of the receptor constitutively activated and does not require the presence of androgens for the activation AR down-stream pathways. Since high AR-V7 expression is one of the most common features of CRPC, targeting this receptor variant is considered as one of the most promising strategies for treating this disease. Therefore anti-AR-V7 molecules could lead to a potential shift in paradigm in the treatment of CRPC. Niclosamide, an already FDA-approved anti-helminthic drug, was identified as a potent AR-V7 inhibitor in prostate cancer cells. Due to the recent positive preclinical results, niclosamide may be an interesting and novel type of targeted treatments for CRPC. This mini-review outlines the most recent pre- and clinical- data on the current status of niclosamide in the treatment of ARV7-positive CRPC patients.

TLX knockdown in the dorsal dentate gyrus of juvenile rats differentially affects adolescent and adult behaviour

The orphan nuclear receptor TLX is predominantly expressed in the central nervous system and is an important factor regulating the maintenance and self-renewal of neural stem cells from embryonic development through adulthood. In adolescence and adulthood, TLX expression is restricted to the neurogenic niches of the brain: the dentate gyrus of the hippocampus and the subventricular zone. The adolescent period is critical for maturation of the hippocampus with heightened levels of neurogenesis observed in rodents. Therefore, we investigated whether lentiviral silencing of TLX expression (TLX knockdown) in the dorsal dentate gyrus of juvenile rats incurred differential impairments in behaviour during late adolescence and adulthood. Our results showed that knockdown of TLX in the dorsal dentate gyrus led to a decrease in cell proliferation in the dorsal but not ventral dentate gyrus. At a behavioural level we observed differential effects in adolescence and adulthood across a number of parameters. A hyperactive phenotype was present in adolescent but not adult TLX knockdown rats, and an increase in immobility during adolescence and in swimming frequency during adulthood was observed in the forced swim test. There was an increased defecation frequency in the open field during adulthood but not adolescence. There were no changes in cognitive performance on hippocampus-dependent tasks or in anxiety-related behaviours. In conclusion, silencing of TLX in the dorsal dentate gyrus led to impairments in hippocampal-independent behaviours which either did not persist or were reversed during adulthood. The current data highlight the temporal importance and function of the nuclear receptor TLX during development.

Molecular dynamics and free energy studies on the Drosophila melanogaster and Leptinotarsa decemlineata ecdysone receptor complexed with agonists: Mechanism for binding and selectivity

The ecdysone receptor is a nuclear hormone receptor that plays a pivotal role in the insect metamorphosis and development. To address the molecular mechanisms of binding and selectivity, the interactions of two typical agonists Ponasterone A and 20-Hydroxyecdysone with Drosophila melanogaster (DME) and Leptinotarsa decemlineata ecdysone (LDE) receptors were investigated by homology modeling, molecular docking, molecular dynamic simulation, and thermodynamic analysis. We discover that 1) the L5-loop, L11-loop, and H12 helix for DME, L7-loop, and L11-loop for LDE are more flexible, which affect the global dynamics of the ligand-binding pocket, thus facilitating the ligand recognition of ecdysone receptor; 2) several key residues (Thr55/Thr37, Phe109/Phe91, Arg95/Arg77, Arg99/Arg81, Phe108/Leu90, and Ala110/Val92) are responsible for the binding of the proteins; 3) the binding-free energy is mainly contributed by the van der Waals forces as well as the electrostatic interactions of ligand and receptor; 4) the computed binding-free energy difference between DME-C1 and LDE-C1 is -4.65 kcal/mol, explains that C1 can form many more interactions with the DME; 5) residues Phe108/Leu90 and Ala110/Val92 have relatively position and orientation difference in the two receptors, accounting most likely for the ligand selectivity of ecdysone receptor from different orders of insects. This study underscores the expectation that different insect pests should be able to discriminate among compounds from different as yet undiscovered compounds, and the results firstly show a structural and functional relay between the agonists and receptors (DME and LDE), which can provide an avenue for the development of target-specific insecticides. Communicated by Ramaswamy H. Sarma.

A Membrane Transporter Is Required for Steroid Hormone Uptake in Drosophila

Steroid hormones are a group of lipophilic hormones that are believed to enter cells by simple diffusion to regulate diverse physiological processes through intracellular nuclear receptors. Here, we challenge this model in Drosophila by demonstrating that Ecdysone Importer (EcI), a membrane transporter identified from two independent genetic screens, is involved in cellular uptake of the steroid hormone ecdysone. EcI encodes an organic anion transporting polypeptide of the evolutionarily conserved solute carrier organic anion superfamily. In vivo, EcI loss of function causes phenotypes indistinguishable from ecdysone- or ecdysone receptor (EcR)-deficient animals, and EcI knockdown inhibits cellular uptake of ecdysone. Furthermore, EcI regulates ecdysone signaling in a cell-autonomous manner and is both necessary and sufficient for inducing ecdysone-dependent gene expression in culture cells expressing EcR. Altogether, our results challenge the simple diffusion model for cellular uptake of ecdysone and may have wide implications for basic and medical aspects of steroid hormone studies.

Impairments in the reproductive axis of female mice lacking estrogen receptor β in GnRH neurons

The effect of estrogen on the differentiation and maintenance of reproductive tissues is mediated by two nuclear estrogen receptors (ERs), ERα, and ERβ. Lack of functional ERα and ERβ genes in vivo significantly affects reproductive function; however, the target tissues and signaling pathways in the hypothalamus are not clearly defined. Here, we describe the generation and reproductive characterization of a complete-ERβ KO (CERβKO) and a GnRH neuron-specific ERβKO (GERβKO) mouse models. Both ERβKO mouse models displayed a delay in vaginal opening and first estrus. Hypothalamic gonadotropin-releasing hormone (GnRH) mRNA expression levels in both ERβKO mice were similar to control mice; however female CERβKO and GERβKO mice had lower basal and surge serum gonadotropin levels. Although a GnRH stimulation test in both female ERβKO models showed preserved gonadotropic function in the same animals, a kisspeptin stimulation test revealed an attenuated response by GnRH neurons, suggesting a role for ERβ in normal GnRH neuron function. No alteration in estrogen-negative feedback was observed in either ERβKO mouse models after ovariectomy and estrogen replacement. Further, abnormal development of ovarian follicles with low serum estradiol levels and impairment of fertility were observed in both ERβKO mouse models. In male ERβKO mice, no differences in the timing of pubertal onset or serum luteinizing hormone and follicle-stimulating hormone levels were observed as compared with controls. Taken together, these data provide in vivo evidence for a role of ERβ in GnRH neurons in modulating puberty and reproduction, specifically through kisspeptin responsiveness in the female hypothalamic-pituitary-gonadal axis.

Conservation of DNA and ligand binding properties of retinoid X receptor from the placozoan Trichoplax adhaerens to human

Nuclear receptors are a superfamily of transcription factors restricted to animals. These transcription factors regulate a wide variety of genes with diverse roles in cellular homeostasis, development, and physiology. The origin and specificity of ligand binding within lineages of nuclear receptors (e.g., subfamilies) continues to be a focus of investigation geared toward understanding how the functions of these proteins were shaped over evolutionary history. Among early-diverging animal lineages, the retinoid X receptor (RXR) is first detected in the placozoan, Trichoplax adhaerens. To gain insight into RXR evolution, we characterized ligand- and DNA-binding activity of the RXR from T. adhaerens (TaRXR). Like bilaterian RXRs, TaRXR specifically bound 9-cis-retinoic acid, which is consistent with a recently published result and supports a conclusion that the ancestral RXR bound ligand. DNA binding site specificity of TaRXR was determined through protein binding microarrays (PBMs) and compared with human RXRɑ. The binding sites for these two RXR proteins were broadly conserved (∼85% shared high-affinity sequences within a targeted array), suggesting evolutionary constraint for the regulation of downstream genes. We searched for predicted binding motifs of the T. adhaerens genome within 1000 bases of annotated genes to identify potential regulatory targets. We identified 648 unique protein coding regions with predicted TaRXR binding sites that had diverse predicted functions, with enriched processes related to intracellular signal transduction and protein transport. Together, our data support hypotheses that the original RXR protein in animals bound a ligand with structural similarity to 9-cis-retinoic acid; the DNA motif recognized by RXR has changed little in more than 1 billion years of evolution; and the suite of processes regulated by this transcription factor diversified early in animal evolution.

The nuclear receptor superfamily: A structural perspective

Nuclear receptors (NRs) are a family of transcription factors that regulate numerous physiological processes such as metabolism, reproduction, inflammation, as well as the circadian rhythm. NRs sense changes in lipid metabolite levels to drive differential gene expression, producing distinct physiologic effects. This is an allosteric process whereby binding a cognate ligand and specific DNA sequences drives the recruitment of diverse transcriptional co-regulators at chromatin and ultimately transactivation or transrepression of target genes. Dysregulation of NR signaling leads to various malignances, metabolic disorders, and inflammatory disease. Given their important role in physiology and ability to respond to small lipophilic ligands, NRs have emerged as valuable therapeutic targets. Here, we summarize and discuss the recent progress on understanding the complex mechanism of action of NRs, primarily from a structural perspective. Finally, we suggest future studies to improve our understanding of NR signaling and better design drugs by integrating multiple structural and biophysical approaches.

Effects of the synthetic estrogen 17-α-ethinylestradiol on Drosophila melanogaster: Dose and gender dependence

17-a-ethinylestradiol (EE2) belongs to the increasing list of Endocrine Disruptors Chemicals (EDCs), able to interfere with the endocrine system in both vertebrates and invertebrates. Regardless of its great dispersion in the environment, to date there is still little knowledge about its action mechanisms and harmful effects in invertebrates. To better evaluate its potential role in invertebrates, we used the model system Drosophila melanogaster, an insect in which the hormonal response has been widely described. The effects of EE2 in D.melanogaster adults have been evaluated by using life traits as well as molecular endpoints. It was found that EE2 significantly decreases survival and fertility in both sexes, with a higher effect in female flies, as well as affects the expression of the Ecdysone Receptor (EcR), Estrogen Related Receptor (ERR), Yolk protein2 (Yp2) and yolkless (yl) genes. In conclusion, our results suggest that EE2 treatment may have potential toxic and endocrine effects on Drosophila melanogaster adults of both sexes. In particular, our data provide an indication that, after EE2 treatment, two of the genes involved in the vitellogenesis process (yl and Yp2) are transcribed in adult males where are mostly silent, and suggest future studies forward their use as potential molecular markers to EDCs exposure in Drosophila male.

NR2F1 mediated down-regulation of osteoblast differentiation was rescued by bone morphogenetic protein-2 (BMP-2) in human MSC

Endochondral ossification is the process by which long bones are formed; the process of long bone formation is regulated by numerous factors such as transcription factors, cytokines, and extracellular matrix molecules. Human hormone Nuclear receptors (hHNR) are a family of ligand-regulated transcription factors that are activated by steroid hormones, such as estrogen and progesterone, and various lipid-soluble signals, including retinoic acid, oxysterols, and thyroid hormone. Whole genome microarray data from our previous study revealed that most hHNR's are up-regulated during osteoblast differentiation in hMSCS. NR2F1 was among the highest expressed hHNR during osteogenesis, NR2F1 belongs to the steroid/thyroid hormone nuclear receptor superfamily. NR2F1 is designated as an orphan nuclear receptor because its ligands are unknown. NR2F1 plays a wide range of roles, including cell differentiation, cancer progression, and central and peripheral neurogenesis. Identifying signaling networks involved in osteoblast differentiation is important in orchestrating new therapeutic and clinical applications in bone biology. This study aimed to identify alterations in signaling networks mediated by NR2F1 in osteoblast differentiation. siRNA-mediated down-regulation of NR2F1 leads to impairment in the differentiation of hBMSC-TERT to osteoblast; gene-expression results confirmed the down-regulation of osteoblast markers such as RUNX2, ALPL, OSC, and BSP. Global whole gene expression analysis revealed that most down-regulated genes were associated with osteoblast differentiation (DDIT3, BMP2). Pathway analysis revealed prominent signaling pathways that were down-regulated, including the TGFβ pathway and MAPK pathway. Functional studies on NR2F1 transfected cells, during osteoblast differentiation in combination with TGFβ1 and BMP-2, showed that TGFβ1 does not recover osteoblast differentiation, whereas BMP-2 rescues osteoblast differentiation in NR2F1 siRNA transfected cells. Thus, our results showed that BMP-2 could intervene in NR2F1 down-regulated signaling pathways to recover osteoblast differentiation.

Estrogenic regulation of social behavior and sexually dimorphic brain formation

It has long been known that the estrogen, 17β-estradiol (17β-E), plays a central role for female reproductive physiology and behavior. Numerous studies have established the neurochemical and molecular basis of estrogenic induction of female sexual behavior, i.e., lordosis, in animal models. In addition, 17β-E also regulates male-type sexual and aggressive behavior. In males, testosterone secreted from the testes is irreversibly aromatized to 17β-E in the brain. We discuss the contribution of two nuclear receptor isoforms, estrogen receptor (ER)α and ERβ to the estrogenic regulation of sexually dimorphic brain formation and sex-typical expression of these social behaviors. Furthermore, 17β-E is a key player for social behaviors such as social investigation, preference, recognition and memory as well as anxiety-related behaviors in social contexts. Recent studies also demonstrated that not only nuclear receptor-mediated genomic signaling but also membrane receptor-mediated non-genomic actions of 17β-E may underlie the regulation of these behaviors. Finally, we will discuss how rapidly developing research tools and ideas allow us to investigate estrogenic action by emphasizing behavioral neural networks.

The Modulating Role of Sex and Anabolic-Androgenic Steroid Hormones in Cannabinoid Sensitivity

Cannabis is the most commonly used illicit drug worldwide. Although its use is associated with multiple adverse health effects, including the risk of developing addiction, recreational and medical cannabis use is being increasing legalized. In addition, use of synthetic cannabinoid drugs is gaining considerable popularity and is associated with mass poisonings and occasional deaths. Delineating factors involved in cannabis use and addiction therefore becomes increasingly important. Similarly to other drugs of abuse, the prevalence of cannabis use and addiction differs remarkably between males and females, suggesting that sex plays a role in regulating cannabinoid sensitivity. Although it remains unclear how sex may affect the initiation and maintenance of cannabis use in humans, animal studies strongly suggest that endogenous sex hormones modulate cannabinoid sensitivity. In addition, synthetic anabolic-androgenic steroids alter substance use and further support the importance of sex steroids in controlling drug sensitivity. The recent discovery that pregnenolone, the precursor of all steroid hormones, controls cannabinoid receptor activation corroborates the link between steroid hormones and the endocannabinoid system. This article reviews the literature regarding the influence of endogenous and synthetic steroid hormones on the endocannabinoid system and cannabinoid action.

C2H2-Type Zinc Finger Proteins: Evolutionarily Old and New Partners of the Nuclear Hormone Receptors

Nuclear hormone receptors (NRs) are evolutionarily conserved ligand-dependent transcription factors. They are essential for human life, mediating the actions of lipophilic molecules, such as steroid hormones and metabolites of fatty acid, cholesterol, and external toxic compounds. The C2H2-type zinc finger proteins (ZNFs) form the largest family of the transcription factors in humans and are characterized by multiple, tandemly arranged zinc fingers. Many of the C2H2-type ZNFs are conserved throughout evolution, suggesting their involvement in preserved biological activities, such as general transcriptional regulation and development/differentiation of organs/tissues observed in the early embryonic phase. However, some C2H2-type ZNFs, such as those with the Krüppel-associated box (KRAB) domain, appeared relatively late in evolution and have significantly increased family members in mammals including humans, possibly modulating their complicated transcriptional network and/or supporting the morphological development/functions specific to them. Such evolutional characteristics of the C2H2-type ZNFs indicate that these molecules influence the NR functions conserved through evolution, whereas some also adjust them to meet with specific needs of higher organisms. We review the interaction between NRs and C2H2-type ZNFs by focusing on some of the latter molecules.

Hormone Therapy and Breast Cancer: Emerging Steroid Receptor Mechanisms

Although hormone therapy is widely used by millions of women to relieve symptoms of menopause, it has been associated with several side-effects such as coronary heart disease, stroke and increased invasive breast cancer risk. These side-effects have caused many women to seek alternatives to conventional hormone therapy, including the controversial custom-compounded bioidentical hormone therapy suggested to not increase breast cancer risk. Historically estrogens and the estrogen receptor were considered the principal factors promoting breast cancer development and progression, however, a role for other members of the steroid receptor family in breast cancer pathogenesis is now evident, with emerging studies revealing an interplay between some steroid receptors. In this review, we discuss examples of hormone therapy used for the relief of menopausal symptoms, highlighting the distinction between conventional hormone therapy and custom-compounded bioidentical hormone therapy. Moreover, we highlight the fact that not all hormones have been evaluated for an association with increased breast cancer risk. We also summarize the current knowledge regarding the role of steroid receptors in mediating the carcinogenic effects of hormones used in menopausal hormone therapy, with special emphasis on the influence of the interplay or crosstalk between steroid receptors. Unraveling the intertwined nature of steroid hormone receptor signaling pathways in breast cancer biology is of utmost importance, considering that breast cancer is the most prevalent cancer among women worldwide. Moreover, understanding these mechanisms may reveal novel prevention or treatment options, and lead to the development of new hormone therapies that does not cause increased breast cancer risk.

Fat-specific protein 27 is a novel target gene of liver X receptor α

Fat-specific protein 27 (FSP27) is highly expressed in the fatty liver of genetically obese ob/ob mice and promotes hepatic triglyceride (TG) accumulation. The nuclear hormone receptor liver X receptor α (LXRα) also plays a critical role in the control of TG levels in the liver. The present study demonstrated transcriptional regulation of Fsp27a and Fsp27b genes by LXRα. Treatment with the LXR ligand T0901317 markedly increased Fsp27a and Fsp27b mRNAs in wild-type C57BL/6J and ob/ob mouse livers. A reporter assay indicated that two LXR-responsive elements (LXREs) are necessary for LXRα-dependent induction of Fsp27a and Fsp27b promoter activities. Furthermore, the LXRα/retinoid X receptor α complex is capable of directly binding to the two LXREs both in vitro and in vivo. These results suggest that LXRα positively regulates Fsp27a and Fsp27b expression through two functional LXREs. Fsp27a/b are novel LXR target genes in the ob/ob fatty liver.

Androgen receptor transcriptional activity and chromatin modifications on the ABCB1/MDR gene are critical for taxol resistance in ovarian cancer cells

We report here that the androgen receptor (AR) and ABCB1 are upregulated in a model of acquired taxol resistance (txr) in ovarian carcinoma cells. AR silencing sensitizes txr cells to taxol threefold, whereas ectopic AR expression in AR-null HEK293 cells induces resistance to taxol by 1.7-fold. AR activation using the agonist dihydrotestosterone (DHT) or sublethal taxol treatment upregulates ABCB1 expression in both txr cells and AR-expressing HEK293 cells. In contrast, AR inactivation using the antagonist bicalutamide downregulates ABCB1 expression and enhances cytotoxicity to taxol. A functional ABCB1 promoter containing five predicted androgen-response elements (AREs) is cloned. Deletion assays reveal a taxol-responsive promoter segment which harbors ARE4. Notably, DHT- or taxol-activated AR potentiates binding of the AR to ARE4 as revealed by the chromatin immunoprecipitation. On the other hand, txr cells display an increase in chromatin remodeling. AR/H3K9ac and AR/H3K14ac complexes bind specifically to ARE4 in response to taxol. Furthermore, acetyltransferase protein levels (p300 and GCN5) are upregulated in txr cells. Silencing of p300 or GCN5 reduces chromatin modification and enhances cytotoxicity in both parental and txr SKOV3 cells. While the phosphatidylinositol 3-kinase (PI3K)/serine/threonine protein kinase (AKT) pathway is significantly activated by taxol, taxol-induced ABCB1 expression, histone posttranslational modifications, and p300 binding to ARE4 are suppressed following inhibition of the PI3K/AKT cellular pathway. These results demonstrate that the AKT/p300/AR axis can be activated to target ABCB1 gene expression in response to taxol, thus revealing a new treatment target to counter taxol resistance.

Sphingosine kinase 1 activation by estrogen receptor α36 contributes to tamoxifen resistance in breast cancer

In breast cancer, 17β-estradiol (E2) plays critical roles mainly by binding to its canonical receptor, estrogen receptor (ER) α66, and eliciting genomic effects. E2 also triggers rapid, nongenomic responses. E2 activates sphingosine kinase 1 (SphK1), increasing sphingosine-1-phosphate (S1P) that binds to its receptors, leading to important breast cancer signaling. However, the E2 receptor responsible for SphK1 activation has not yet been identified. Here, we demonstrate in triple-negative breast cancer cells, which lack the canonical ERα66 but express the novel splice variant ERα36, that ERα36 is the receptor responsible for E2-induced activation of SphK1 and formation and secretion of S1P and dihydro-S1P, the ligands for S1PRs. Tamoxifen, the first-line endocrine therapy for breast cancer, is an antagonist of ERα66, but an agonist of ERα36, and, like E2, activates SphK1 and markedly increases secretion of S1P. A major problem with tamoxifen therapy is development of acquired resistance. We found that tamoxifen resistance correlated with increased SphK1 and ERα36 expression in tamoxifen-resistant breast cancer cells, in patient-derived xenografts, and in endocrine-resistant breast cancer patients. Our data also indicate that targeting this ERα36 and SphK1 axis may be a therapeutic option to circumvent endocrine resistance and improve patient outcome.

Molecular mechanisms underlying sexual differentiation of the nervous system

A long-standing goal in developmental neuroscience is to understand the mechanisms by which steroid sex hormones pattern the mammalian central nervous system along male or female pathways to enable subsequent displays of sexually dimorphic behaviors. In this article, we review recent advances in understanding the epigenetic and transcriptional mechanisms mediating sexual differentiation of the brain in mammals, flies, and worms. These studies suggest a model of sexual differentiation wherein master regulators of sex determination initiate a cascade of sexually dimorphic gene expression that controls development of neural pathways and behavioral displays in a strikingly modular manner. With these advances in molecular genetics, it is now feasible to disassemble different components of sexually dimorphic social behaviors without disrupting other behavioral interactions. Such experimental tractability promises rapid advances in this exciting field.

The success and the challenge of all-trans retinoic acid in the treatment of cancer

All-trans retinoic acid (ATRA), an active metabolite of vitamin A, plays important roles in cell proliferation, cell differentiation, apoptosis, and embryonic development. The effects of ATRA are mediated by nuclear retinoid receptors as well as non-genomic signal pathway, such as MAPK and PKA. The great success of differentiation therapy with ATRA in acute promyelocytic leukemia (APL) not only improved the prognosis of APL but also spurred the studies of ATRA in the treatment of other tumors. Since the genetic and physiopathological simplicity of APL is not common in human malignancies, the combination of ATRA with other agents (chemotherapy, epigenetic modifiers, and arsenic trioxide, etc) had been extensively investigated in a variety of tumors. In this review, we will discuss in details about ATRA and its role in cancer treatment.

Sex and seasonal differences in mRNA expression of estrogen receptor α (ESR1) in red-sided garter snakes (Thamnophis sirtalis parietalis)

Estrogens are important regulators of reproductive physiology including sexual signal expression and vitellogenesis. For the regulation to occur, the hormone must bind and activate receptors in target tissues, and expression of the receptors can vary by sex and/or season. By simultaneously comparing circulating hormone levels with receptor expression, a more complete understanding of hormone action can be gained. Our study species, the red-sided garter snake (Thamnophis sirtalis parietalis), provides an excellent opportunity to study the interaction between sex steroid hormones and receptor expression in addition to sexual dimorphism and seasonality. During the spring mating season, male garter snakes rely exclusively on the female's skin-based, estrogen-dependent sex pheromone to direct courtship. Males can be stimulated to produce this sexual attractiveness pheromone by treatment with estradiol (E₂), which also induces male vitellogenesis. Estrogen receptors (ESRs) are required to transduce the effects of estrogens, thus we used quantitative RT-PCR to analyze expression of ESR alpha (ERα; gene ESR1) mRNA in the skin and liver of wild caught male and female garter snakes across simulated spring and fall conditions in the laboratory. While ESR1 was present in the skin of both sexes, there were no sex or seasonal differences in expression levels. Liver expression of ESR1, however, was sexually dimorphic, with females showing greatest expression in fall when circulating E₂ concentrations were lowest. There were no statistically significant correlations between E₂ and ESR1 expression. Our data suggest that the skin of both sexes is sensitive to estrogen signaling and thus the production of sex pheromone is dependent on bioavailable levels of E₂. Female expression of ESR1 in the liver may increase in the fall to prime energy storage mechanisms required for vitellogenesis the following year.

Characterization and Expression Dynamics of Key Genes Involved in the Gilthead Sea Bream (Sparus aurata) Cortisol Stress Response during Early Ontogeny

The present study identified and characterized six key genes involved in the hypothalamic-pituitary-interrenal (HPI) axis of gilthead sea bream (Sparus aurata), a commercially important European aquaculture species. The key genes involved in the HPI axis for which gene structure and synteny analysis was carried out, comprised of two functional forms of glucocorticoid receptors (GR), as well as three forms of pro-opiomelanocortin (POMC) genes and one form of mineralocorticoid receptor (MR) gene. To explore their functional roles during development but also in the stress response, the expression profiles of gr1, gr2, mr, pomc_aI, pomc_aII, and pomc_β were examined during early ontogeny and after an acute stress challenge. The acute stress challenge was applied at the stage of full formation of all fins, where whole body cortisol was also measured. Both the cortisol and the molecular data implied that sea bream larvae at the stage of the full formation of all fins at 45 dph are capable of a response to stress of a similar profile as observed in adult fish.

A phase 1, open-label, dose escalation study of intravenous paricalcitol in combination with gemcitabine in patients with advanced malignancies

BACKGROUND

Calcitriol, the active analogue of vitamin D, is antiproliferative and enhances the cytotoxicity of several anticancer agents, including gemcitabine. The vitamin D receptor (VDR) is expressed in the tumor stroma and treatment with VDR ligands results in stromal remodeling and increased intratumoral gemcitabine delivery. Furthermore, calcitriol can decrease the activity of the gemcitabine deactivating enzyme cytidine deaminase (CDD). Because hypercalcemia has been the most worrisome calcitriol-related adverse event, the less hypercalcemic agent paricalcitol may be preferred for further investigation.

METHODS

The authors undertook a phase 1 study of gemcitabine in combination with escalating doses of paricalcitol administered weekly intravenously in patients with advanced cancers. A standard 3+3 dose escalation schema was used. Pharmacokinetic assessment of gemcitabine and its metabolite 2',2'-difluorodeoxyuridine (dFdU) was performed. Pharmacodynamic assessment of paricalcitol was performed by measurement of CDD activity in peripheral blood mononuclear cells.

RESULTS

A total of 44 patients were enrolled. Somnolence was the main dose-limiting toxicity. The highest dose of paricalcitol administered was 10.5 µg/kg. Hypercalcemia was infrequent and mild in severity. Paricalcitol did not appear to affect the pharmacokinetics of gemcitabine and dFdU. Evaluation of CDD activity was available for 9 patients; no clear trend for CDD activity after treatment with paricalcitol was established. The overall response rate was 4%; the rate of disease control was 67% in patients who were pretreated with gemcitabine. Progression-free and overall survival were 3.4 months and 6.5 months, respectively.

CONCLUSIONS

Paricalcitol can be administered safely in doses up to 7 µg/kg weekly with fixed dose rate gemcitabine without dose-limiting hypercalcemia. To the best of the authors' knowledge, the maximum tolerated dose has not been formally established to date. Preliminary clinical activity deserves further exploration.

Feedback control of the CXCR7/CXCL11 chemokine axis by estrogen receptor α in ovarian cancer

Ovarian cancer (OC) is one of the most intractable diseases, exhibiting tremendous molecular heterogeneity and lacking reliable methods for screening, resulting in late diagnosis and widespread peritoneal dissemination. Menopausal estrogen replacement therapy is a well-recognized risk factor for OC, but little is known about how estrogen might contribute to this disease at the cellular level. This study identifies chemokine receptor CXCR7/ACKR3 as an estrogen-responsive gene, whose expression is markedly enhanced by estrogen through direct recruitment of ERα and transcriptional active histone modifications in OC cells. The gene encoding CXCR7 chemokine ligand I-TAC/CXCL11 was also upregulated by estrogen, resulting in Ser-118 phosphorylation, activation, and recruitment of estrogen receptor ERα at the CXCR7 promoter locus for positive feedback regulation. Both CXCR7 and CXCL11, but not CXCR3 (also recognized to interact with CXCL11), were found to be significantly increased in stromal sections of microdissected tumors and positively correlated in mesenchymal subtype of OC. Estrogenic induction of mesenchymal markers SNAI1, SNAI2, and CDH2 expression, with a consequent increase in cancer cell migration, was shown to depend on CXCR7, indicating a key role for CXCR7 in mediating estrogen upregulation of mesenchymal markers to induce invasion of OC cells. These findings identify a feed-forward mechanism that sustains activation of the CXCR7/CXCL11 axis under ERα control to induce the epithelial-mesenchymal transition pathway and metastatic behavior of OC cells. Such interplay underlies the complex gene profile heterogeneity of OC that promotes changes in tumor microenvironment and metastatic acquisition.