Molecular chaperones throughout the life cycle of the androgen receptor

QSPRmodeler - An open source application for molecular predictive analytics

The drug design process can be successfully supported using a variety of in silico methods. Some of these are oriented toward molecular property prediction, which is a key step in the early drug discovery stage. Before experimental validation, drug candidates are usually compared with known experimental data. Technically, this can be achieved using machine learning approaches, in which selected experimental data are used to train the predictive models. The proposed Python software is designed for this purpose. It supports the entire workflow of molecular data processing, starting from raw data preparation followed by molecular descriptor creation and machine learning model training. The predictive capabilities of the resulting models were carefully validated internally and externally. These models can be easily applied to new compounds, including within more complex workflows involving generative approaches.

Polyglutamine disease proteins: Commonalities and differences in interaction profiles and pathological effects

Currently, nine polyglutamine (polyQ) expansion diseases are known. They include spinocerebellar ataxias (SCA1, 2, 3, 6, 7, 17), spinal and bulbar muscular atrophy (SBMA), dentatorubral-pallidoluysian atrophy (DRPLA), and Huntington's disease (HD). At the root of these neurodegenerative diseases are trinucleotide repeat mutations in coding regions of different genes, which lead to the production of proteins with elongated polyQ tracts. While the causative proteins differ in structure and molecular mass, the expanded polyQ domains drive pathogenesis in all these diseases. PolyQ tracts mediate the association of proteins leading to the formation of protein complexes involved in gene expression regulation, RNA processing, membrane trafficking, and signal transduction. In this review, we discuss commonalities and differences among the nine polyQ proteins focusing on their structure and function as well as the pathological features of the respective diseases. We present insights from AlphaFold-predicted structural models and discuss the biological roles of polyQ-containing proteins. Lastly, we explore reported protein-protein interaction networks to highlight shared protein interactions and their potential relevance in disease development.

Determination of the androgen receptor status of disseminated tumor cells in primary breast cancer patients

PURPOSE

Androgen receptor (AR) can serve as a new therapeutic target since it was shown to play a proliferative role in several breast cancer (BC) subtypes. Moreover, AR positivity has been suggested to reflect the metastatic potential of tumor cells in some BC subtypes. The aim of this study was to determine the AR expression on disseminated tumor cells (DTCs) as a surrogate marker of minimal residual disease (MRD) and potential precursor of metastasis in early BC.

METHODS

Bone marrow (BM) aspirates from 62 DTC-positive early BC patients were included into this study and analyzed by immunofluorescence staining for the presence of AR-positive DTCs. CK-positive, CD45-negative cells containing an intact nucleus (DAPI positive) were identified as DTCs. AR expression of the primary tumor (PT) was assessed by immunohistochemistry on formalin-fixed, paraffin-embedded (FFPE) tumor sections from core biopsies and surgical specimens.

RESULTS

AR status of DTCs could be determined in 21 patients. We detected AR-positive DTCs in nine samples (43%). AR expression of DTCs and corresponding PT showed a concordance rate of 33%. The DTC-AR status did not correlate with clinicopathological factors, nor did we observe a significant correlation between the AR status of the PT and other established prognostic factors for BC.

CONCLUSION

AR-positive DTCs can be detected in BM of early BC patients with a marked discordance of the AR status between DTCs and corresponding PTs. The clinical significance of these findings needs further investigation.

Immune Cells, Gut Microbiota, and Vaccines: A Gender Perspective

The development of preventive and therapeutic vaccines has played a crucial role in preventing infections and treating chronic and non-communicable diseases, respectively. For a long time, the influence of sex differences on modifying health and disease has not been addressed in clinical and preclinical studies. The interaction of genetic, epigenetic, and hormonal factors plays a role in the sex-related differences in the epidemiology of diseases, clinical manifestations, and the response to treatment. Moreover, sex is one of the leading factors influencing the gut microbiota composition, which could further explain the different predisposition to diseases in men and women. In the same way, differences between sexes occur also in the immune response to vaccines. This narrative review aims to highlight these differences, focusing on the immune response to vaccines. Comparative data about immune responses, vaccine effectiveness, and side effects are reviewed. Hence, the intricate interplay between sex, immunity, and the gut microbiota will be discussed for its potential role in the response to vaccination. Embracing a sex-oriented perspective in research may improve the efficacy of the immune response and allow the design of tailored vaccine schedules.

Testosterone Replacement Therapy and Cardiovascular Disease: Balancing Safety and Risks in Hypogonadal Men

PURPOSE OF REVIEW: The purpose of this review is to analyze the link between testosterone replacement therapy (TRT) and adverse cardiovascular (CV) events. RECENT FINDINGS: A few published studies suggest a link between TRT and CV events. These studies contained flaws, and many other studies reveal a reduction in CV events. Hypogonadism is associated with increased mortality in men with CVD. TRT in hypogonadal men can improve many CVD risk factors, reduce QT interval prolongation, lead to better outcomes in heart failure patients, and slow the progression of atherosclerosis. The use of TRT to achieve physiologic testosterone concentrations in men does not pose a threat to CV health and has demonstrated a cardioprotective effect.

Current status and future perspective on the management of metastatic castration-sensitive prostate cancer

Since 1941, the standard treatment for metastatic castration-sensitive prostate cancer (mCSPC) was androgen deprivation therapy (ADT) by surgical or medical castration with or without first-generation antiandrogen. However, the efficacy of ADT does not last in most cases. In the 2010s, de-intensification by intermittent ADT was evaluated by RCTs for mCSPC to mitigate the treatment-emerged burdens. However, intermittent ADT failed to show non-inferiority in OS for mCSPC and is an optional treatment for selected patients with mCSPC. The treatment for patients with mCSPC has improved in the last years. Currently, based on the evidence from RCTs, intensification treatment by adding docetaxel, novel androgen receptor pathway inhibitors and multimodal treatment using radiotherapy to the primary have become new standard treatments for mCSPC. Furthermore, ongoing RCTs have been investigating the clinical values of more intensified treatments by combining multiple effective treatment for mCSPC. In addition, novel treatment using immunotherapeutics such as anti-PD-1 antibody and precision medicine approach using novel imaging and genomic marker has been investigated vigorously. Thus, we review current treatment evidence obtained by RCTs that included patients with mCSPC. The future key to mCSPC treatment could be personalized medicine including translational and clinical medicine aspects, with molecular testing to assess the biological tumor behavior to optimize clinical decision-making.

A New Old Target: Androgen Receptor Signaling and Advanced Prostate Cancer

Owing to the development of multiple novel therapies, there has been major progress in the treatment of advanced prostate cancer over the last two decades; however, the disease remains invariably fatal. Androgens and the androgen receptor (AR) play a critical role in prostate carcinogenesis, and targeting the AR signaling axis with abiraterone, enzalutamide, darolutamide, and apalutamide has improved outcomes for men with this lethal disease. Targeting the AR and elucidating mechanisms of resistance to these agents remains central to drug development efforts. This review provides an overview of the evolution and current approaches for targeting the AR in advanced prostate cancer. It describes the biology of AR signaling, explores AR-targeting resistance mechanisms, and discusses future perspectives and promising novel therapeutic strategies. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Functional Effects In Silico Prediction for Androgen Receptor Ligand-Binding Domain Novel I836S Mutation

Over 1000 mutations are described in the androgen receptor (AR) gene. Of those, about 600 were found in androgen insensitivity syndrome (AIS) patients, among which 400 mutations affect the ligand-binding domain (LBD) of the AR protein. Recently, we reported a novel missense mutation c.2507T>G I836S (ClinVarID: 974911) in a patient with complete AIS (CAIS) phenotype. In the present study, we applied a set of computational approaches for the structural analysis of the ligand-binding domains in a wild-type and mutant AR to evaluate the functional impact of the novel I836S mutation. We revealed that the novel I836S substitution leads to a shorter existence time of the ligand's gating tunnel and internal cavity, occurring only in the presence of S836 phosphorylation. Additionally, the analysis of phosphorylation of the 836 mutant residues explained the negative impact on AR homodimerization, since monomer surface changes indirectly impacted the binding site. Our analyses provide evidence that I836S causes disruptions of AR protein functionality and development of CAIS clinical features in patients.

Influence of Androgens on Immunity to Self and Foreign: Effects on Immunity and Cancer

It is well-known that sex hormones can directly and indirectly influence immune cell function. Different studies support a suppressive role of androgens on different components of the immune system by decreasing antibody production, T cell proliferation, NK cytotoxicity, and stimulating the production of anti-inflammatory cytokines. Androgen receptors have also been detected in many different cells of hematopoietic origin leading to direct effects of their ligands on the development and function of the immune system. The immunosuppressive properties of androgens could contribute to gender dimorphisms in autoimmune and infectious disease and thereby also hamper immune surveillance of tumors. Consistently, females generally are more prone to autoimmunity, while relatively less susceptible to infections, and have lower incidence and mortality of the majority of cancers compared to males. Some studies show that androgen deprivation therapy (ADT) can induce expansion of naïve T cells and increase T-cell responses. Emerging clinical data also reveal that ADT might enhance the efficacy of various immunotherapies including immune checkpoint blockade. In this review, we will discuss the potential role of androgens and their receptors in the immune responses in the context of different diseases. A particular focus will be on cancer, highlighting the effect of androgens on immune surveillance, tumor biology and on the efficacy of anti-cancer therapies including emerging immune therapies.

Is There Room for SERMs or SARMs as Alternative Therapies for Adult Male Hypogonadism?

Hypogonadotropic hypogonadism (HH) can be sustained by organic or functional alterations of the hypothalamic-pituitary-testicular axis. Functional HH is related to systemic alterations, such as obesity or chronic inflammatory diseases, but could contribute to a negative course of the illness. For such situation, according to results obtained in infertile women, the administration of selective estrogen receptor modulators (SERMs) has been proposed in males too, with positive results on both metabolic and sexual function. This class of medications increases gonadotropin levels via antagonism to the estrogenic receptor; similar biological effects are also exerted by aromatase inhibitors (AIs), despite different mechanism of action. After a brief review of trials regarding SERMs and AIs use in male HH, we describe the structure and function of the androgen receptor (AR) as a basis for clinical research about compounds able to bind to AR, in order to obtain specific effects (SARMs). The tissue selectivity and different metabolic fate in comparison to testosterone can potentiate anabolic versus androgenic effects; therefore, they might be a valid alternative to testosterone replacement therapy avoiding the negative effects of testosterone (i.e., on prostate, liver, and hematopoiesis). Trials are still at an early phase of investigation and, at the moment, the application seems to be more useful for chronic disease with catabolic status while the validation as replacement for hypogonadism requires further studies.

Determination of the androgen receptor status of circulating tumour cells in metastatic breast cancer patients

BACKGROUND

The prognostic relevance of circulating tumour cells (CTCs) in metastatic breast cancer (MBC) patients has been confirmed by several clinical trials. However, predictive blood-based biomarkers for stratification of patients for targeted therapy are still lacking. The DETECT studies explore the utility of CTC phenotype for treatment decisions in patients with HER2 negative MBC. Associated with this concept is a plethora of translational projects aiming to identify potential predictive biomarkers. The androgen receptor (AR) is expressed in over 70% of hormone receptor-positive and up-to 45% of triple-negative tumours. Studies has indicated the promising nature of AR as a new therapy target with a clinical benefit rate for anti-AR treatment in MBC patients up to 25% The aim of this analysis was the characterization of CTCs regarding the expression of the AR using immunofluorescence.

METHODS

MBC patients were screened for the HER2-status of CTCs in the DETECT studies. In a subset of CTC-positive patients (n = 67) an additional blood sample was used for immunomagnetic enrichment of CTCs using the CellSearch® Profile Kit prior to transfer of the cells onto cytospin slides. Establishment of immunofluorescence staining for the AR was performed using prostate cancer cell lines LNCaP and DU145 as positive and negative control, respectively. Staining of DAPI, pan-cytokeratin (CK) and CD45 was applied to identify nucleated epithelial cells as CTCs and to exclude leucocytes.

RESULTS

Co-staining of the AR, CK and CD45 according to the above mentioned workflow has been successfully established using cell lines with known AR expression spiked into the blood samples from healthy donors. For this translational project, samples were analysed from 67 patients participating in the DETECT studies. At least one CTC was detected in 37 out of 67 patients (56%). In 16 of these 37 patients (43%) AR-positive CTCs were detected. In eight out of 25 patients (32%) with more than one CTC, AR-positive and AR-negative CTCs were observed.

CONCLUSION

In 43% of the analysed CTC samples from patients with MBC the AR expression has been detected. The predictive value of AR expression in CTCs remains to be evaluated in further trials.

Hsp70 and Hsp40 inhibit an inter-domain interaction necessary for transcriptional activity in the androgen receptor

Molecular chaperones such as Hsp40 and Hsp70 hold the androgen receptor (AR) in an inactive conformation. They are released in the presence of androgens, enabling transactivation and causing the receptor to become aggregation-prone. Here we show that these molecular chaperones recognize a region of the AR N-terminal domain (NTD), including a FQNLF motif, that interacts with the AR ligand-binding domain (LBD) upon activation. This suggests that competition between molecular chaperones and the LBD for the FQNLF motif regulates AR activation. We also show that, while the free NTD oligomerizes, binding to Hsp70 increases its solubility. Stabilizing the NTD-Hsp70 interaction with small molecules reduces AR aggregation and promotes its degradation in cellular and mouse models of the neuromuscular disorder spinal bulbar muscular atrophy. These results help resolve the mechanisms by which molecular chaperones regulate the balance between AR aggregation, activation and quality control.

Hsp chaperones stabilize the inactive conformation of androgen receptor (AR) and are released upon hormone-induced AR activation. Here, the authors locate the Hsp binding region on AR, and show that Hsp70 reduces AR aggregation and promotes AR degradation in cellular and mouse models of a neuromuscular disorder.

Role of androgen receptor splice variants, their clinical relevance and treatment options

PURPOSE

In this review, we summarize the importance of AR variants with a particular focus on clinically relevant members of this family.

METHODS

A non-systematic literature review was performed based on Medline and PubMed.

RESULTS

Endocrine therapy represents the central paradigm for the management of prostate cancer. Eventually, in response to androgen ablation therapy, several resistance mechanisms against the endocrine therapy might develop that can circumvent the therapy approaches. One specific resistance mechanism that has gained increasing attention is the generation of alternatively spliced variants of the androgen receptor, with AR-V7 being the most prominent. More broadly, AR-V7 is one member of a group of alternatively spliced AR variants that share a common feature, the missing ligand-binding domain. These ΔLBD androgen receptor variants have shown the capability to induce androgen receptor-mediated gene transcription even under conditions of androgen deprivation and to drive cancer progression.

CONCLUSION

The methods used for detecting AR-Vs, at least on the mRNA level, are well-advanced and harbor the potential to be introduced into clinical diagnostics. It is important to note, that the testing, especially of AR-V7 has its limitations in predicting treatment response. More promising is the great number of active clinical trials aimed at reducing the AR-Vs, and using this to re-sensitize CRPC towards endocrine treatment might provide additional treatment options for CRPC patients in the future.

Targeting the Hsp40/Hsp70 Chaperone Axis as a Novel Strategy to Treat Castration-Resistant Prostate Cancer

Castration-resistant prostate cancer (CRPC) is characterized by reactivation of androgen receptor (AR) signaling, in part by elevated expression of AR splice variants (ARv) including ARv7, a constitutively active, ligand binding domain (LBD)-deficient variant whose expression has been correlated with therapeutic resistance and poor prognosis. In a screen to identify small-molecule dual inhibitors of both androgen-dependent and androgen-independent AR gene signatures, we identified the chalcone C86. Binding studies using purified proteins and CRPC cell lysates revealed C86 to interact with Hsp40. Pull-down studies using biotinylated-C86 found Hsp40 present in a multiprotein complex with full-length (FL-) AR, ARv7, and Hsp70 in CRPC cells. Treatment of CRPC cells with C86 or the allosteric Hsp70 inhibitor JG98 resulted in rapid protein destabilization of both FL-AR and ARv, including ARv7, concomitant with reduced FL-AR- and ARv7-mediated transcriptional activity. The glucocorticoid receptor, whose elevated expression in a subset of CRPC also leads to androgen-independent AR target gene transcription, was also destabilized by inhibition of Hsp40 or Hsp70. In vivo, Hsp40 or Hsp70 inhibition demonstrated single-agent and combinatorial activity in a 22Rv1 CRPC xenograft model. These data reveal that, in addition to recognized roles of Hsp40 and Hsp70 in FL-AR LBD remodeling, ARv lacking the LBD remain dependent on molecular chaperones for stability and function. Our findings highlight the feasibility and potential benefit of targeting the Hsp40/Hsp70 chaperone axis to treat prostate cancer that has become resistant to standard antiandrogen therapy.Significance: These findings highlight the feasibility of targeting the Hsp40/Hsp70 chaperone axis to treat CRPC that has become resistant to standard antiandrogen therapy. Cancer Res; 78(14); 4022-35. ©2018 AACR.

Endocrine Disrupting Chemicals Mediated through Binding Androgen Receptor Are Associated with Diabetes Mellitus

Endocrine disrupting chemicals (EDCs) can mimic natural hormone to interact with receptors in the endocrine system and thus disrupt the functions of the endocrine system, raising concerns on the public health. In addition to disruption of the endocrine system, some EDCs have been found associated with many diseases such as breast cancer, prostate cancer, infertility, asthma, stroke, Alzheimer’s disease, obesity, and diabetes mellitus. EDCs that binding androgen receptor have been reported associated with diabetes mellitus in in vitro, animal, and clinical studies. In this review, we summarize the structural basis and interactions between androgen receptor and EDCs as well as the associations of various types of diabetes mellitus with the EDCs mediated through androgen receptor binding. We also discuss the perspective research for further understanding the impact and mechanisms of EDCs on the risk of diabetes mellitus.

A Tale of Two Signals: AR and WNT in Development and Tumorigenesis of Prostate and Mammary Gland

Prostate cancer (PCa) is one of the most common cancers and among the leading causes of cancer deaths for men in industrialized countries. It has long been recognized that the prostate is an androgen-dependent organ and PCa is an androgen-dependent disease. Androgen action is mediated by the androgen receptor (AR). Androgen deprivation therapy (ADT) is the standard treatment for metastatic PCa. However, almost all advanced PCa cases progress to castration-resistant prostate cancer (CRPC) after a period of ADT. A variety of mechanisms of progression from androgen-dependent PCa to CRPC under ADT have been postulated, but it remains largely unclear as to when and how castration resistance arises within prostate tumors. In addition, AR signaling may be modulated by extracellular factors among which are the cysteine-rich glycoproteins WNTs. The WNTs are capable of signaling through several pathways, the best-characterized being the canonical WNT/β-catenin/TCF-mediated canonical pathway. Recent studies from sequencing PCa genomes revealed that CRPC cells frequently harbor mutations in major components of the WNT/β-catenin pathway. Moreover, the finding of an interaction between β-catenin and AR suggests a possible mechanism of cross talk between WNT and androgen/AR signaling pathways. In this review, we discuss the current knowledge of both AR and WNT pathways in prostate development and tumorigenesis, and their interaction during development of CRPC. We also review the possible therapeutic application of drugs that target both AR and WNT/β-catenin pathways. Finally, we extend our review of AR and WNT signaling to the mammary gland system and breast cancer. We highlight that the role of AR signaling and its interaction with WNT signaling in these two hormone-related cancer types are highly context-dependent.

Discovery Proteomics Identifies a Molecular Link between the Coatomer Protein Complex I and Androgen Receptor-dependent Transcription

Aberrant androgen receptor (AR)-dependent transcription is a hallmark of human prostate cancers. At the molecular level, ligand-mediated AR activation is coordinated through spatial and temporal protein-protein interactions involving AR-interacting proteins, which we designate the “AR-interactome.” Despite many years of research, the ligand-sensitive protein complexes involved in ligand-mediated AR activation in prostate tumor cells have not been clearly defined. Here, we describe the development, characterization, and utilization of a novel human LNCaP prostate tumor cell line, N-AR, which stably expresses wild-type AR tagged at its N terminus with the streptavidin-binding peptide epitope (streptavidin-binding peptide-tagged wild-type androgen receptor; SBP-AR). A bioanalytical workflow involving streptavidin chromatography and label-free quantitative mass spectrometry was used to identify SBP-AR and associated ligand-sensitive cytosolic proteins/protein complexes linked to AR activation in prostate tumor cells. Functional studies verified that ligand-sensitive proteins identified in the proteomic screen encoded modulators of AR-mediated transcription, suggesting that these novel proteins were putative SBP-AR-interacting proteins in N-AR cells. This was supported by biochemical associations between recombinant SBP-AR and the ligand-sensitive coatomer protein complex I (COPI) retrograde trafficking complex in vitro. Extensive biochemical and molecular experiments showed that the COPI retrograde complex regulates ligand-mediated AR transcriptional activation, which correlated with the mobilization of the Golgi-localized ARA160 coactivator to the nuclear compartment of prostate tumor cells. Collectively, this study provides a bioanalytical strategy to validate the AR-interactome and define novel AR-interacting proteins involved in ligand-mediated AR activation in prostate tumor cells. Moreover, we describe a cellular system to study how compartment-specific AR-interacting proteins influence AR activation and contribute to aberrant AR-dependent transcription that underlies the majority of human prostate cancers.

Structures of androgen receptor bound with ligands: advancing understanding of biological functions and drug discovery

INTRODUCTION

Androgen receptor (AR) is a ligand-dependent transcription factor and a member of the nuclear receptor superfamily. It plays a vital role in male sexual development and regulates gene expression in various tissues, including prostate. Androgens are compounds that exert their biological effects via interaction with AR. Binding of androgens to AR initiates conformational changes in AR that affect binding of co-regulator proteins and DNA. AR agonists and antagonists are widely used in a variety of clinical applications (i.e. hypogonadism and prostate cancer therapy).

AREAS COVERED

This review provides a close look at structures of AR-ligand complexes and mutations in the receptor that have been revealed, discusses current challenges in the field, and sheds light on future directions.

EXPERT OPINION

AR is one of the primary targets for the treatment of prostate cancer, as AR antagonists inhibit prostate cancer growth. However, these drugs are not effective for long-term treatment and lead to castration-resistant prostate cancer. The structures of AR-ligand complexes are an invaluable scientific asset that enhances our understanding of biological functions and mechanisms of androgenic and anti-androgenic chemicals as well as promotes the discovery of superior drug candidates.

Corepressive function of nuclear receptor coactivator 2 in androgen receptor of prostate cancer cells treated with antiandrogen

BACKGROUND

Recruitment of cofactors in the interaction of the androgen receptor (AR) and AR ligands plays a critical role in determining androgenic/antiandrogenic effects of the AR ligand on signaling, but the functions of key cofactors, including nuclear receptor coactivator (NCOA), remain poorly understood in prostate cancer cells treated with AR ligands.

METHODS

We examined prostate cancer cell lines LNCaP and VCaP expressing mutated and wild-type ARs, respectively, to clarify the significance of NCOAs in the effect of antiandrogens. Hydroxyflutamide showed antagonistic activity against VCaP and an agonistic effect on LNCaP. Bicalutamide served as an antagonist for both. We analyzed mRNA transcription and protein expression of NCOAs in these cells pretreated with dihydrotestosterone and thereafter treated with the mentioned antiandrogens. Transcriptional silencing of candidate NCOAs and AR was performed using small interfering RNA (siRNA). Cell proliferation was evaluated with MTT assay.

RESULTS

LNCaP treated with bicalutamide showed an about four-fold increase in the expression of NCOA2 mRNA compared to those pretreated with dihydrotestosterone alone (P <0.01). In VCaP pretreated with dihydrotestosterone, transcriptions of NCOA2 and NCOA7 were slightly increased with bicalutamide (1.96- and 2.42-fold, respectively) and hydroxyflutamide (1.33-fold in both). With Western blotting, the expression of NCOA2 protein also increased in LNCaP cells treated with bicalutamide compared with that in control cells pretreated with dihydrotestosterone alone. Following silencing with siRNA for NCOA2, PSA levels in media with LNCaP receiving bicalutamide were elevated compared with those in non-silencing controls (101.6 ± 4.2 vs. 87.8 ± 1.4 ng/mL, respectively, P =0.0495). In LNCaP cells treated with dihydrotestosterone and bicalutamide, NCOA2-silencing was associated with a higher proliferation activity compared with non-silencing control and AR-silencing.

CONCLUSION

NCOA2, which has been thought to be recruited as a coactivator, possibly plays a corepressive role in AR of prostate cancer cells when treated with antiandrogens, suggesting its potential as a therapeutic target.

Extranuclear Actions of the Androgen Receptor Enhance Glucose-Stimulated Insulin Secretion in the Male

Although men with testosterone deficiency are at increased risk for type 2 diabetes (T2D), previous studies have ignored the role of testosterone and the androgen receptor (AR) in pancreatic β cells. We show that male mice lacking AR in β cells (βARKO) exhibit decreased glucose-stimulated insulin secretion (GSIS), leading to glucose intolerance. The AR agonist dihydrotestosterone (DHT) enhances GSIS in cultured male islets, an effect that is abolished in βARKO(-/y) islets and human islets treated with an AR antagonist. In β cells, DHT-activated AR is predominantly extranuclear and enhances GSIS by increasing islet cAMP and activating the protein kinase A. In mouse and human islets, the insulinotropic effect of DHT depends on activation of the glucagon-like peptide-1 (GLP-1) receptor, and accordingly, DHT amplifies the incretin effect of GLP-1. This study identifies AR as a novel receptor that enhances β cell function, a finding with implications for the prevention of T2D in aging men.

Second-Generation HSP90 Inhibitor Onalespib Blocks mRNA Splicing of Androgen Receptor Variant 7 in Prostate Cancer Cells

Resistance to available hormone therapies in prostate cancer has been associated with alternative splicing of androgen receptor (AR) and specifically, the expression of truncated and constitutively active AR variant 7 (AR-V7). The transcriptional activity of steroid receptors, including AR, is dependent on interactions with the HSP90 chaperone machinery, but it is unclear whether HSP90 modulates the activity or expression of AR variants. Here, we investigated the effects of HSP90 inhibition on AR-V7 in prostate cancer cell lines endogenously expressing this variant. We demonstrate that AR-V7 and full-length AR (AR-FL) were depleted upon inhibition of HSP90. However, the mechanisms underlying AR-V7 depletion differed from those for AR-FL. Whereas HSP90 inhibition destabilized AR-FL and induced its proteasomal degradation, AR-V7 protein exhibited higher stability than AR-FL and did not require HSP90 chaperone activity. Instead, HSP90 inhibition resulted in the reduction of AR-V7 mRNA levels but did not affect total AR transcript levels, indicating that HSP90 inhibition disrupted AR-V7 splicing. Bioinformatic analyses of transcriptome-wide RNA sequencing data confirmed that the second-generation HSP90 inhibitor onalespib altered the splicing of at least 557 genes in prostate cancer cells, including AR. These findings indicate that the effects of HSP90 inhibition on mRNA splicing may prove beneficial in prostate cancers expressing AR-V7, supporting further clinical investigation of HSP90 inhibitors in malignancies no longer responsive to androgen deprivation. Cancer Res; 76(9); 2731-42. ©2016 AACR.

Intracellular kinetics of the androgen receptor shown by multimodal Image Correlation Spectroscopy (mICS)

The androgen receptor (AR) pathway plays a central role in prostate cancer (PCa) growth and progression and is a validated therapeutic target. In response to ligand binding AR translocates to the nucleus, though the molecular mechanism is not well understood. We therefore developed multimodal Image Correlation Spectroscopy (mICS) to measure anisotropic molecular motion across a live cell. We applied mICS to AR translocation dynamics to reveal its multimodal motion. By integrating fluorescence imaging methods we observed evidence for diffusion, confined movement, and binding of AR within both the cytoplasm and nucleus of PCa cells. Our findings suggest that in presence of cytoplasmic diffusion, the probability of AR crossing the nuclear membrane is an important factor in determining the AR distribution between cytoplasm and the nucleus, independent of functional microtubule transport. These findings may have implications for the future design of novel therapeutics targeting the AR pathway in PCa.

Association study of androgen signaling pathway genes in polycystic ovary syndrome

OBJECTIVE

To evaluate genes involved in androgen receptor (AR) signaling as candidate genes for polycystic ovary syndrome (PCOS).

DESIGN

Two groups of women with PCOS and control women (discovery and replication cohorts), were genotyped for single-nucleotide polymorphisms (SNPs) in eight genes for AR chaperones and co-chaperones: HSPA1A, HSPA8, ST13, STIP1, PTGES3, FKBP4, BAG1, and STUB1. Single-nucleotide polymorphisms were tested for association with PCOS status and with androgenic and metabolic parameters.

SETTING

Tertiary referral center.

PATIENT(S)

Discovery cohort: 354 women with PCOS and 161 control women. Replication cohort: 397 women with PCOS and 306 control women.

INTERVENTION(S)

Phenotypic and genotypic assessment.

MAIN OUTCOME MEASURE(S)

Single-nucleotide polymorphism genotypes, association with PCOS status, and androgenic and metabolic parameters.

RESULT(S)

In the discovery cohort, FKBP4 SNPs rs2968909 and rs4409904 were associated with lower odds of PCOS. This finding was not confirmed in the replication cohort analysis; however, when combining the two cohorts, rs4409904 was associated with lower odds of PCOS. In subjects with PCOS in the replication cohort as well as in the combined cohort, rs2968909 was associated with lower body mass index.

CONCLUSION(S)

Single-nucleotide polymorphisms in FKBP4, which codes for the AR co-chaperone FKBP52, may be associated with PCOS and body mass index in patients with PCOS. The remaining genes studied do not seem to be major contributors to the development of PCOS. These findings warrant confirmation in future studies, and genes encoding other androgen pathway components remain to be studied.

Trinucleotide repeats and protein folding and disease: the perspective from studies with the androgen receptor

The androgen receptor (AR), a ligand activated transcription factor plays a number of roles in reproduction, homeostasis and pathogenesis of disease. It has two major polymorphic sequences; a polyglutamine and a polyglycine repeat that determine the length of the protein and influence receptor folding, structure and function. Here, we review the role the folding of the AR plays in the pathogenesis of spinal-bulbar muscular atrophy (SBMA), a neuromuscular degenerative disease arising from expansion of the polyglutamine repeat. We discuss current management for SBMA patients and how research on AR structure function may lead to future drug treatments.

Targeting the androgen receptor pathway in castration-resistant prostate cancer: progresses and prospects

Androgen receptor (AR) signaling is a critical pathway for prostate cancer cells, and androgen-deprivation therapy (ADT) remains the principal treatment for patients with locally advanced and metastatic disease. However, over time, most tumors become resistant to ADT. The view of castration-resistant prostate cancer (CRPC) has changed dramatically in the last several years. Progress in understanding the disease biology and mechanisms of castration resistance led to significant advancements and to paradigm shift in the treatment. Accumulating evidence showed that prostate cancers develop adaptive mechanisms for maintaining AR signaling to allow for survival and further evolution. The aim of this review is to summarize molecular mechanisms of castration resistance and provide an update in the development of novel agents and strategies to more effectively target the AR signaling pathway.

The NLR-related protein NWD1 is associated with prostate cancer and modulates androgen receptor signaling

Prostate cancer (PCa) is among the leading causes of cancer-related death in men. Androgen receptor (AR) signaling plays a seminal role in prostate development and homeostasis, and dysregulation of this pathway is intimately linked to prostate cancer pathogenesis and progression. Here, we identify the cytosolic NLR-related protein NWD1 as a novel modulator of AR signaling. We determined that expression of NWD1 becomes elevated during prostate cancer progression, based on analysis of primary tumor specimens. Experiments with cultured cells showed that NWD1 expression is up-regulated by the sex-determining region Y (SRY) family proteins. Gene silencing procedures, in conjunction with transcriptional profiling, showed that NWD1 is required for expression of PDEF (prostate-derived Ets factor), which is known to bind and co-regulate AR. Of note, NWD1 modulates AR protein levels. Depleting NWD1 in PCa cell lines reduces AR levels and suppresses activity of androgen-driven reporter genes. NWD1 knockdown potently suppressed growth of androgen-dependent LNCaP prostate cancer cells, thus showing its functional importance in an AR-dependent tumor cell model. Proteomic analysis suggested that NWD1 associates with various molecular chaperones commonly related to AR complexes. Altogether, these data suggest a role for tumor-associated over-expression of NWD1 in dysregulation of AR signaling in PCa.

The ubiquitin-proteasome system in neurodegenerative diseases: precipitating factor, yet part of the solution

The ubiquitin-proteasome system (UPS) has been implicated in neurodegenerative diseases based on the presence of deposits consisting of ubiquitylated proteins in affected neurons. It has been postulated that aggregation-prone proteins associated with these disorders, such as α-synuclein, β-amyloid peptide, and polyglutamine proteins, compromise UPS function, and delay the degradation of other proteasome substrates. Many of these substrates play important regulatory roles in signaling, cell cycle progression, or apoptosis, and their inadvertent stabilization due to an overloaded and improperly functioning UPS may thus be responsible for cellular demise in neurodegeneration. Over the past decade, numerous studies have addressed the UPS dysfunction hypothesis using various model systems and techniques that differ in their readout and sensitivity. While an inhibitory effect of some disease proteins on the UPS has been demonstrated, increasing evidence attests that the UPS remains operative in many disease models, which opens new possibilities for treatment. In this review, we will discuss the paradigm shift that repositioned the UPS from being a prime suspect in the pathophysiology of neurodegeneration to an attractive therapeutic target that can be harnessed to accelerate the clearance of disease-linked proteins.

Shikonin inhibits the growth of human prostate cancer cells via modulation of the androgen receptor

Shikonin, a natural naphthoquinone isolated from the traditional Chinese medicine Zi Cao (gromwell), has been shown to possess tumor cell killing activity. The human androgen receptor (AR) is a nuclear transcription factor that serves as a major therapeutic target for prostate cancer. However, AR regulation by shikonin has not been reported. We investigated the effects of shikonin on the growth of prostate cancer cells. We observed that shikonin decreased the expression of AR at both the mRNA and the protein levels in LNCaP and 22RV1 human prostate cancer cells. The results from a luciferase assay showed that shikonin decreased the transcriptional activity of AR. Moreover, shikonin treatment inhibited AR target gene expression, PSA and growth inhibition of prostate cancer cells. In conclusion, the present study shows for the first time that shikonin treatment causes transcriptional repression of AR and inhibition of its nuclear localization in human prostate cancer cells. We propose that shikonin, an anticancer drug extracted from natural sources, induces inhibition of cell growth through modulation of AR in androgen-responsive prostate cancer cells and is a candidate for use in cancer chemotherapy for human prostate cancer.

Androgen induces a switch from cytoplasmic retention to nuclear import of the androgen receptor

The androgen receptor (AR) has critical functions as a transcription factor in both normal and cancer cells, but the specific mechanisms that regulate its nuclear localization are not well defined. We found that an AR mutation commonly reported in prostate cancer generates an androgen-independent gain of function for nuclear import. The substitution, Thr877Ala, is within the ligand-binding domain, but the nuclear import gain of function is mediated by the bipartite nuclear localization signal (NLS) spanning the DNA-binding domain (DBD) and hinge region. Bipartite NLS activity depends on the structure provided by the DBD, and protein interactions with the bipartite NLS are repressed by the hinge region. The bipartite NLS is recognized by importin 7, a nuclear import receptor for several proteins. Importin 7 binding to AR, however, inhibits import by shielding the bipartite NLS. Androgen binding relieves the inhibition by inducing a switch that promotes exchange of importin 7 for karyopherin alpha import receptors. Importin 7 contributes to the regulation of AR import by restraining import until androgen is detected in the cytoplasm.

Knockdown of the cochaperone SGTA results in the suppression of androgen and PI3K/Akt signaling and inhibition of prostate cancer cell proliferation

Solid tumors have an increased reliance on Hsp70/Hsp90 molecular chaperones for proliferation, survival and maintenance of intracellular signaling systems. An underinvestigated component of the chaperone system is the tetratricopeptide repeat (TPR)-containing cochaperone, which coordinates Hsp70/Hsp90 involvement on client proteins as well as having diverse individual actions. A potentially important cochaperone in prostate cancer (PCa) is small glutamine-rich TPR-containing protein alpha (SGTA), which interacts with the androgen receptor (AR) and other critical cancer-related client proteins. In this study, the authors used small interfering RNA coupled with genome-wide expression profiling to investigate the biological significance of SGTA in PCa and its influence on AR signaling. Knockdown of SGTA for 72 hr in PCa C4-2B cells significantly altered expression of >1,900 genes (58% decreased) and reduced cell proliferation (p < 0.05). The regulation of 35% of 5α-dihydrotestosterone (DHT) target genes was affected by SGTA knockdown, with gene-specific effects on basal or DHT-induced expression or both. Pathway analysis revealed a role for SGTA in p53, generic PCa and phosphoinositol kinase (PI3K) signaling pathways; the latter evident by a reduction in PI3K subunit p100β levels and decreased phosphorylated Akt. Immunohistochemical analysis of 64 primary advanced PCa samples showed a significant increase in the AR:SGTA ratio in cancerous lesions compared to patient-matched benign prostatic hyperplasia tissue (p < 0.02). This study not only provides insight into the biological actions of SGTA and its effect on genome-wide AR transcriptional activity and other therapeutically targeted intracellular signaling pathways but also provides evidence for PCa-specific alterations in SGTA expression.

Proteomic profiling of rabbit embryonic stem cells derived from parthenotes and fertilized embryos

Rabbit embryonic stem (rES) cells can be derived from various sources of embryos. However, understanding of the gene expression profile, which distincts embryonic stem (ES) cells from other cell types, is still extremely limited. In this study, we compared the protein profiles of three independent lines of rabbit cells, i.e., fibroblasts, fertilized embryo-derived stem (f-rES) cells, and parthenote-derived ES (p-rES) cells. Proteomic analyses were performed using two-dimensional gel electrophoresis (2-DE) and mass spectrometry. Collectively, the expression levels of 100 out of 284 protein spots differed significantly among these three cell types (p<0.05). Of those differentially expressed spots, 91% were identified in the protein database and represented 63 distinct proteins. Proteins with known identities are mainly localized in the cytoplasmic compartments (48%), nucleus (14%), and cytoskeletal machineries (13%). These proteins were majorly involved in biological functions of energy and metabolic pathways (25%), cell growth and maintenance (25%), signal transduction (14%), and protein metabolisms (10%). When protein expression levels among cell types were compared, six proteins associated with a variety of cellular activities, including structural constituents of the cytoskeleton (tubulins), structural molecule (KRT8), catalytic molecules (α-enolase), receptor complex scaffold (14-3-3 protein sigma), microfilament motor proteins (Myosin-9), and heat shock protein (HSP60), were found highly expressed in p-rES cells. Two proteins related to HSP activity and structural constituent of cytoskeleton in f-rES cells, and one structural molecule activity protein in fibroblasts showed significantly higher expression levels (p<0.05). Marker protein expressions in f-rES and p-rES cells were further confirmed by Western blotting and immunocytochemical staining. This study demonstrated unique proteomic profiles of the three rabbit cell types and revealed some novel proteins differentially expressed between f-rES and p-rES cells. These analyses provide insights into rES cell biology and would invite more in-depth studies toward rES cell applications.

Targeting alternative sites on the androgen receptor to treat castration-resistant prostate cancer

Recurrent, metastatic prostate cancer continues to be a leading cause of cancer-death in men. The androgen receptor (AR) is a modular, ligand-inducible transcription factor that regulates the expression of genes that can drive the progression of this disease, and as a consequence, this receptor is a key therapeutic target for controlling prostate cancer. The current drugs designed to directly inhibit the AR are called anti-androgens, and all act by competing with androgens for binding to the androgen/ligand binding site. Unfortunately, with the inevitable progression of the cancer to castration resistance, many of these drugs become ineffective. However, there are numerous other regulatory sites on this protein that have not been exploited therapeutically. The regulation of AR activity involves a cascade of complex interactions with numerous chaperones, co-factors and co-regulatory proteins, leading ultimately to direct binding of AR dimers to specific DNA androgen response elements within the promoter and enhancers of androgen-regulated genes. As part of the family of nuclear receptors, the AR is organized into modular structural and functional domains with specialized roles in facilitating their inter-molecular interactions. These regions of the AR present attractive, yet largely unexploited, drug target sites for reducing or eliminating androgen signaling in prostate cancers. The design of small molecule inhibitors targeting these specific AR domains is only now being realized and is the culmination of decades of work, including crystallographic and biochemistry approaches to map the shape and accessibility of the AR surfaces and cavities. Here, we review the structure of the AR protein and describe recent advancements in inhibiting its activity with small molecules specifically designed to target areas distinct from the receptor’s androgen binding site. It is anticipated that these new classes of anti-AR drugs will provide an additional arsenal to treat castration-resistant prostate cancer.

Nuclear receptors and their selective pharmacologic modulators

Nuclear receptors are ligand-activated transcription factors and include the receptors for steroid hormones, lipophilic vitamins, sterols, and bile acids. These receptors serve as targets for development of myriad drugs that target a range of disorders. Classically defined ligands that bind to the ligand-binding domain of nuclear receptors, whether they are endogenous or synthetic, either activate receptor activity (agonists) or block activation (antagonists) and due to the ability to alter activity of the receptors are often termed receptor "modulators." The complex pharmacology of nuclear receptors has provided a class of ligands distinct from these simple modulators where ligands display agonist/partial agonist/antagonist function in a tissue or gene selective manner. This class of ligands is defined as selective modulators. Here, we review the development and pharmacology of a range of selective nuclear receptor modulators.

Anti-Tumor Effects and Pharmacokinetics of S-40542, a Novel Non-Steroidal Anti-Androgen, in Mice

OBJECTIVES

The current study was undertaken to explore novel anti-androgens. We investigated a series of tetrahydroquinoline compounds and identified 1-(8-nitro-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinolin-4-yl)ethane-1,2-diol (S-40542).

METHODS

Affinity for androgen receptor of S-40542 was evaluated in receptor binding assay. Effects of repeated treatment with S-40542 and bicalutamide on prostate weight were examined in mice subcutaneously treated for 14days. Efficacy of S-40542 and bicalutamide against prostate cancer was evaluated in an androgen-dependent prostate cancer xenograft model using KUCaP-2 cell line. Plasma concentrations of these agents in mice after oral and subcutaneous administration were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) system.

RESULTS

S-40542 displayed twofold higher affinity to androgen receptor than bicalutamide in vitro. Subcutaneous repeated administration of S-40542 (10-100 mg/kg) significantly reduced the prostate weight. Oral repeated treatment with S-40542 (30, 100 mg/kg) for 28 days significantly suppressed growth of KUCaP-2 tumor. Similar administration of bicalutamide also exerted significantly anti-tumor effect in the model. The serum prostate-specific antigen level was little influenced by the S-40542 treatment, while significantly decreased by bicalutamide. Oral treatment with S-40542 resulted in a dose-dependent elevation of the plasma concentration, and its Cmax and AUC were much lower than those of bicalutamide. The pharmacokinetic study showed that this agent had relatively short plasma half-life and low oral bioavailability.

CONCLUSION

S-40542 as well as bicalutamide has shown as an anti-androgen by reducing the prostate weight of mice. Repeated oral treatment with S-40542 was shown to significantly suppress tumor growth in the KUCaP-2 xenograft model.

The androgen receptor in health and disease

Androgens play pivotal roles in the regulation of male development and physiological processes, particularly in the male reproductive system. Most biological effects of androgens are mediated by the action of nuclear androgen receptor (AR). AR acts as a master regulator of downstream androgen-dependent signaling pathway networks. This ligand-dependent transcriptional factor modulates gene expression through the recruitment of various coregulator complexes, the induction of chromatin reorganization, and epigenetic histone modifications at target genomic loci. Dysregulation of androgen/AR signaling perturbs normal reproductive development and accounts for a wide range of pathological conditions such as androgen-insensitive syndrome, prostate cancer, and spinal bulbar muscular atrophy. In this review we summarize recent advances in understanding of the epigenetic mechanisms of AR action as well as newly recognized aspects of AR-mediated androgen signaling in both men and women. In addition, we offer a perspective on the use of animal genetic model systems aimed at eventually developing novel therapeutic AR ligands.

Anti-androgenic effects of S-40542, a novel non-steroidal selective androgen receptor modulator (SARM) for the treatment of benign prostatic hyperplasia

BACKGROUND

Selective androgen receptor modulators (SARMs) would provide alternative therapeutic agent for androgen-related diseases. We identified a tetrahydroquinoline (THQ) derivative, 1-(8-nitro-3a, 4, 5, 9b-tetrahydro-3H-cyclopenta[c]quinolin-4-yl) ethane-1, 2-diol (S-40542) as a novel SARM antagonist.

METHODS

Affinity for nuclear receptors of S-40542 was evaluated in receptor-binding studies. Androgen receptor (AR) transcriptional activity of S-40542 was investigated by luciferase reporter assay in DU145AR cells. Normal and benign prostatic hyperplasia (BPH) model rats were repeatedly treated with S-40542 and flutamide. The tissue weights of prostate and levator ani muscle as well as blood levels of testosterone and luteinizing hormone were measured.

RESULTS

S-40542 bound to the AR with high affinity. S-40542 at relatively high concentrations increased the transcriptional activity. This agent also showed a concentration-dependent AR antagonistic action in the presence of 1 nM 5α-dihydrotestosterone. Repeated treatment with S-40542 and flutamide decreased dose-dependently the weights of the prostate to a similar extent. In contrast, the tissue weight-reducing effect by S-40542 treatment on the levator ani muscle was much weaker than that of flutamide. S-40542 had little effect on the blood level of testosterone and luteinizing hormone, whereas flutamide increased the level of both hormones. Furthermore, S-40542 decreased dose-dependently prostate weight of BPH rats.

CONCLUSIONS

The current results indicate that S-40542 possesses the prostate-selective SARM activity, suggestive of clinical benefit against benign prostate hyperplasia. THQ compounds may be useful for the research of mode of action of SARMs and for the development of safe SARM antagonists.

Putting the brakes on continued androgen receptor signaling in castration-resistant prostate cancer

Patients with advanced prostate cancer initially respond very well to medical or surgical castration. Despite a good initial response, the disease progresses to a castration-resistant state. Castration-resistant prostate cancer (CRPC) remains addicted to androgen receptor signaling. The addition of conventional anti-androgen agents, such as bicalutamide, only provides a transient benefit. This has led to a search for further drug targets. Cytochrome P450 17 (CYP17) is an enzyme that is vital for the adrenal biosynthesis of androgens. The CYP17 inhibitor abiraterone acetate has a proven benefit in a phase III randomized trial and other CYP17 inhibitors are currently being evaluated. The novel antiandrogen MDV3100 is a small molecule androgen receptor antagonist with promising activity. Heat shock proteins (HSPs) bind to the androgen receptor and modify its activity. Several HSP inhibitors are under evaluation in clinical trials. This review explores the role of CYP17 inhibitors, MDV3100, and HSP inhibitors.

Biology of castration-recurrent prostate cancer

Although androgen-deprivation therapy is the standard therapy for advanced and metastatic prostate cancer, this treatment is only palliative. Prostate cancer recurs then grows despite low circulating testicular androgens, using several mechanisms that remain dependent on androgen-receptor signaling in most cases. This article reviews the diversity of mechanisms used for growth by castration-recurrent prostate cancer.

Molecular chaperoning by glucose-regulated protein 170 in the extracellular milieu promotes macrophage-mediated pathogen sensing and innate immunity

Recognition of pathogen-associated molecular patterns by innate immune receptors is essential for host defense responses. Although extracellular stress proteins are considered as indicators of the stressful conditions (e.g., infection or cell injury), the exact roles of these molecules in the extracellular milieu remain less defined. We found that glucose-regulated protein 170 (Grp170), the largest stress protein and molecular chaperone, is highly efficient in binding CpG oligodeoxynucleotides (CpG-ODN), the microbial DNA mimetic sensed by toll-like receptor 9 (TLR9). Extracellular Grp170 markedly potentiates the endocytosis and internalization of CpG-ODN by mouse bone marrow-derived macrophages and directly interacts with endosomal TLR9 on cell entry. These molecular collaborations result in the synergistic activation of the MyD88-dependent signaling and enhanced production of proinflammatory cytokines and nitric oxide in mouse primary macrophages as well as human THP-1 monocyte-derived macrophages, suggesting that Grp170 released from injured cells facilitates the sensing of pathogen-associated "danger" signals by intracellular receptors. This CpG-ODN chaperone complex-promoted innate immunity confers increased resistance in mice to infection of Listeria monocytogenes compared with CpG-ODN treatment alone. Our studies reveal a previously unrecognized attribute of Grp170 as a superior DNA-binding chaperone capable of amplifying TLR9 activation on pathogen recognition, which provides a conceptual advance in understanding the dynamics of ancient chaperoning functions inside and outside the cell.

Proteomic analysis of the androgen receptor via MS-compatible purification of biotinylated protein on streptavidin resin

The strength of the streptavidin/biotin interaction poses challenges for the recovery of biotinylated molecules from streptavidin resins. As an alternative to high-temperature elution in urea-containing buffers, we show that mono-biotinylated proteins can be released with relatively gentle heating in the presence of biotin and 2% SDS/Rapigest, avoiding protein carbamylation and minimizing streptavidin dissociation. We demonstrate the utility of this mild elution strategy in two studies of the human androgen receptor (AR). In the first, in which formaldehyde cross-linked complexes are analyzed in yeast, a mass spectrometry-based comparison of the AR complex using SILAC reveals an association between the androgen-activated AR and the Hsp90 chaperonin, while Hsp70 chaperonins associate specifically with the unliganded complex. In the second study, the endogenous AR is quantified in the LNCaP cell line by absolute SILAC and MRM-MS showing approximately 127,000 AR copies per cell, substantially more than previously measured using radioligand binding.

Evidence that lack of ligand-binding domain correlates with nuclear distribution of unliganded human androgen receptor and loss of transactivation activity

Androgen receptor (AR) is one of the large superfamily of nuclear hormone receptors. AR consists of distinct domains including an N-terminal DNA-binding domain and a C-terminal ligand-binding domain (LBD). Regulation of AR nuclear import and subsequent transactivation activity represent essential steps in androgen action. Mutations in the AR gene are known to cause different degrees of androgen insensitivity syndrome (AIS). This study aimed to identify the possible contribution of LBD of AR to cellular distribution, ligand binding, and transactivation activities using mutant AR clone lacking the entire LBD that we previously observed in an AIS patient. Subcellular distribution was assessed by green fluorescence protein-tagged vector and transcriptional activity was analyzed by luciferase assay. Wild-type AR had ligand-dependent transcriptional activation and nuclear import activities. On the other hand, mutant AR had no transcriptional activity regardless of the presence of ligand, 5-α-dihydroxytestosterone (DHT). These mutants were presented predominantly in the nucleus even without DHT. The observation of no transactivation in the mutant receptor must be due to the loss of complex formation between androgen and AR protein. The C-terminal domain has the critical role in the cellular localization and transactivation as well as on the ligand binding.

Oxidative stress and androgen receptor signaling in the development and progression of castration-resistant prostate cancer

Aberrant androgen receptor (AR) signaling plays a critical role in androgen-dependent prostate cancer (PCa), as well as in castration-resistant PCa (CRPC). Oxidative stress seems to contribute to the tumorigenesis and progression of PCa, as well as the development of CRPC, via activation of AR signaling. This notion is supported by the fact that there is an aberrant or improper regulation of the redox status in these disorders. Additionally, androgen-deprivation-induced oxidative stress seems to be involved in the pathogenesis of several disorders caused by androgen-deprivation therapy (ADT), including osteoporosis, neurodegenerative disease, and cardiovascular disease. Oxidative stress can be suppressed with antioxidants or via a reduction in reactive oxygen species production. Thus, developing new therapeutic agents that reduce oxidative stress might be useful in preventing the conversion of androgen-dependent PCa into CRPC, as well as reducing the adverse effects associated with ADT. The objective of this review is to provide an overview regarding the relationship between oxidative stress and AR signaling in the context of PCa and especially CRPC. Additionally, we discuss the potential use of antioxidant therapies in the treatment of PCa.

Biological properties of androgen receptor pure antagonist for treatment of castration-resistant prostate cancer: optimization from lead compound to CH5137291

BACKGROUND

Castration-resistant prostate cancer (CRPC) is still dependent on androgen receptor (AR) signaling. We previously reported that a novel nonsteroidal AR pure antagonist, CH4933468, which is a thiohydantoin derivative with a sulfonamide side chain, provided in vitro proof of concept but did not in vivo.

METHODS

We developed other derivatives, CH5137291, CH5138514, and CH5166623, and their pharmacological properties were compared with CH4933468 and bicalutamide. Agonist/antagonist activities in AR-mediated transactivation, cell proliferation against LNCaP and LNCaP-BC2, and AR translocation were evaluated. Agonist metabolite was monitored in liver microsomes and in pharmacokinetics experiments. Antitumor activities in CRPC xenograft models were examined using LNCaP-BC2 and VCaP-CRPC.

RESULTS

All CH compounds completely inhibited AR-mediated transactivation and proliferation of LNCaP and LNCaP-BC2. In contrast bicalutamide showed a partial inhibition of AR-mediated transactivation and a proliferation of LNCaP-BC2. AR translocation to nucleus was inhibited by CH compounds, but stimulated by bicalutamide. In the LNCaP-BC2 xenograft model, however, only CH5137291 showed significant inhibition of plasma PSA level and antitumor activity. The other three CH compounds were metabolized to their core structure which had agonist activity. CH5137291 also exhibited antitumor activity in a VCaP-CRPC xenograft model, but bicalutamide did not.

CONCLUSIONS

The molecular mechanism of the CH compounds, inhibition of AR translocation, was different from bicalutamide and this action could contribute to AR pure antagonist activity. Agonist metabolite diminished the antitumor activity of AR pure antagonist. CH5137291 exhibited antitumor activity in LNCaP-BC2 and VCaP-CRPC xenograft models, suggesting that the compound has potential for the treatment of CRPC.

The role of stress proteins in prostate cancer

The development of therapeutic resistance, after hormone or chemotherapy for example, is the underlying basis for most cancer deaths. Exposure to anticancer therapies induces expression of many stress related proteins, including small heat shock proteins (HSPs). HSPs interact with various client proteins to assist in their folding and enhance the cellular recovery from stress, thus restoring protein homeostasis and promoting cell survival. The vents of cell stress and cell death are linked, as the induction of molecular chaperones appears to function at key regulatory points in the control of apoptosis. On the basis of these observations and on the role of molecular chaperones in the regulation of steroid receptors, kinases, caspases, and other protein remodelling events involved in chromosome replication and changes in cell structure, it is not surprising that molecular chaperones have been implicated in the control of cell growth and in resistance to various anticancer treatments that induce apoptosis. Recently, several molecular chaperones such as Clusterin and HSP27 have been reported to be involved in development and progression of hormone-refractory prostate cancer. In this review, we address some of the molecular and cellular events initiated by treatment induced stress, and discuss the potential role of chaperone proteins as targets for prostate cancer treatment.

Influence of dosing time on the efficacy and safety of finasteride in rats

Finasteride (FIN), a widely used medication for the treatment of androgen-dependent diseases, blocks the conversion of testosterone to a more potent androgen, dihydrotestosterone (DHT). In this study, we investigated a dosing time-dependent effect and safety of FIN in rats. Androgen receptor (AR) mRNA and nuclear protein levels exhibited clear daily rhythms with the peak during the dark period in the prostate and during the light period in the liver. Repeated oral administration of FIN (5 or 100 mg/kg) at 3 h after lights on (HALO) for 2 weeks decreased serum DHT concentration throughout a 24-h period, whereas the dosing of the agent at 15 HALO decreased its level only transiently even in the higher dose group. FIN caused laboratory abnormalities in the 3 HALO group but not in the 15 HALO group. However, the effect of FIN on the prostate weight was not influenced by the dosing time. These results suggest that the safety, but not effect, of FIN depends on its dosing time in rats. The dosing of FIN in the active period might be a rational dosage regimen, which is needed to be confirmed in human subjects.

Harnessing expression data to identify novel candidate genes in polycystic ovary syndrome

Novel pathways in polycystic ovary syndrome (PCOS) are being identified in gene expression studies in PCOS tissues; such pathways may contain key genes in disease etiology. Previous expression studies identified both dickkopf homolog 1 (DKK1) and DnaJ (Hsp40) homolog, subfamily B, member 1 (DNAJB1) as differentially expressed in PCOS tissue, implicating them as candidates for PCOS susceptibility. To test this, we genotyped a discovery cohort of 335 PCOS cases and 198 healthy controls for three DKK1 single nucleotide polymorphisms (SNPs) and four DNAJB1 SNPs and a replication cohort of 396 PCOS cases and 306 healthy controls for 1 DKK1 SNP and 1 DNAJB1 SNP. SNPs and haplotypes were determined and tested for association with PCOS and component phenotypes. We found that no single nucleotide polymorphisms were associated with PCOS risk; however, the major allele of rs1569198 from DKK1 was associated with increased total testosterone (discovery cohort P = 0.0035) and dehydroepiandrosterone sulfate (replication cohort P = 0.05). Minor allele carriers at rs3962158 from DNAJB1 had increased fasting insulin (discovery cohort P = 0.003), increased HOMA-IR (discovery cohort P = 0.006; replication cohort P = 0.036), and increased HOMA-%B (discovery cohort P = 0.004). Carriers of haplotype 2 at DNAJB1 also had increased fasting insulin, HOMA-IR, and HOMA-%B. These findings suggest that genetic variation in DKK1 and DNAJB1 may have a role in the hyperandrogenic and metabolic dysfunction of PCOS, respectively. Our results also demonstrate the utility of gene expression data as a source of novel candidate genes in PCOS, a complex and still incompletely defined disease, for which alternative methods of gene identification are needed.

Steroid signaling activation and intracellular localization of sex steroid receptors

In addition to stimulating gene transcription, sex steroids trigger rapid, non-genomic responses in the extra-nuclear compartment of target cells. These events take place within seconds or minutes after hormone administration and do not require transcriptional activity of sex steroid receptors. Depending on cell systems, activation of extra-nuclear signaling pathways by sex steroids fosters cell cycle progression, prevents apoptosis, leads to epigenetic modifications and increases cell migration through cytoskeleton changes. These findings have raised the question of intracellular localization of sex steroid receptors mediating these responses. During the past years, increasing evidence has shown that classical sex steroid receptors localized in the extra-nuclear compartment or close to membranes of target cells induce these events. The emerging picture is that a process of bidirectional control between signaling activation and sex steroid receptor localization regulates the outcome of hormonal responses in target cells. This mechanism ensures cell cycle progression in estradiol-treated breast cancer cells, and its derangement might occur in progression of human proliferative diseases. These findings will be reviewed here together with unexpected examples of the relationship between sex steroid receptor localization, signaling activation and biological responses in target cells. We apologize to scientists whose reports are not mentioned or extensively discussed owing to space limitations.