Androgen receptor (AR) coregulators: an overview

Androgen regulation of gene expression

The biological action of androgenic male sex steroid hormones in prostate tissue is mediated by the androgen receptor, a nuclear transcription factor. The transcriptional program of androgenic signaling in the prostate consists of thousands of gene targets whose products play a role in almost all cellular functions, including cellular proliferation, survival, lipid metabolism, and differentiation. This review will provide a summary of the most recent data regarding androgen-regulated target genes and modulation of androgen receptor activity, especially with regard to androgen-dependent and castration-recurrent prostate cancer.

Structural and functional analysis of amino-terminal enhancer of split in androgen-receptor-driven transcription

We previously demonstrated that the Groucho protein AES (amino-terminal enhancer of split) functions as a co-repressor of the AR (androgen receptor). It physically interacts with the N-terminal domain of AR and inhibits AR-driven transcription, but the molecular mechanism of its action remained unclear. In the present paper we report that the AES protein contains one inhibitory domain, and one positive and one negative regulatory domain. The negative regulatory domain inhibits AES dimerization and AES-mediated inhibition of AR-driven transcription through an interaction with the inhibitory domain. The positive regulatory domain blocked this interaction and relieved the inhibitory effect. In addition, we discovered mechanisms by which AES regulates AR transcriptional activity, which included disruption of the interaction between the AR N-terminal and C-terminal domains, and inhibition of AR-DNA interaction. Although AES broadly inhibited the activity of androgen-dependent luciferase reporters in a transient transfection assay, it selectively regulated the expression of endogenous androgen-dependent genes in prostate cancer cells.

Age-related changes in the expression of 11beta-hydroxysteroid dehydrogenase type 2 in rat Leydig cells

Previous studies in rats have shown that the ability of Leydig cells (LCs) to produce testosterone significantly declines with age. To address the possible mechanisms by which aging LCs lose their steroidogenic function, we determined the effect of aging on the expression of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) type 2. The enzyme plays a protective role in blunting the suppressive effects of glucocorticoids on LCs steroidogenesis. Our immunohistochemical analysis revealed progressive decline in 11beta-HDS type 2 expression in LCs of the 18 months of age rats and the most significant reduction in 11beta-HSD2 immunoreactivity was evident in the testicular interstitium of 24- month-old rats. The decrease in the 11beta-HDS type 2 immunostaining in LCs during aging coincided with decline in insulin-like 3/relaxin-like factor (INSL3/RLF) expression, an independent marker for LCs differentiation status. Concomitant with the age-related decrease of 11beta-HDS type 2 immunoreactivity in the LCs population, the immunoexpression of 3beta-hydroxysteroid dehydrogenase (3beta-HSD), marker for LCs steroidogenic activity, was greatly reduced at 24 months compared to 3-month-old control. Similar pattern of expression exhibited also androgen receptor (AR) which is localized in the nuclei of Sertoli cells (SCs), LCs, and peritubular cells. During ages we observed progressive decrease in the immunoreactivity for AR in the testicular types and there was a loss of stage specificity in SCs at age of 24 months. It now seems evident that a variety of factors are likely to be involved in age-related decreases in LCs steroidogenesis, including 11beta-HSD type 2. The observed reduction in 11beta-HSD type 2 expression in aging LCs reflects the decline in their protection ability, opposing the suppressive effect of glucocorticoids on testosterone production.

Variable expression of nuclear receptor coactivator 4 (NcoA4) during mouse embryonic development

Human nuclear receptor coactivator 4 (NcoA4) amplifies the activity of several ligand-activated nuclear transcription factors, including the aryl hydrocarbon receptor (AhR) and androgen receptor (AR). Because these receptors exert important regulatory effects during development, with AhR ubiquitously expressed after embryonic day 9.5 (E9.5) and AR expressed from E12 onward, we examined NcoA4 expression in mouse embryos from E9.5 to E17.5. Full-length NcoA4 transcript was detected by RT-PCR at all embryonic stages and in all adult mouse tissues examined, although a novel splice variant was also detected. Western blot analysis indicated the expression of full-length NcoA4 protein, which was more highly expressed at later (E15.5-E17.5) embryonic stages. NcoA4 protein was also present at varying levels in all adult mouse tissues examined. A dynamic expression profile for NcoA4 during early development was indicated by immunohistochemistry in cardiac, hepatic, and lung tissue. Unlike human NcoA4, murine NcoA4 lacks an LXXLL motif, which has been implicated in the interaction with AR. Overexpression of murine NcoA4 augmented the transcriptional activity of AhR by 5-fold and AR by only 1.5-fold in COS cells. These studies demonstrate ubiquitous NcoA4 expression throughout development and suggest that this coactivator may play a role in modulating nuclear receptor activity, particularly that of the AhR, during development.

TAF1 differentially enhances androgen receptor transcriptional activity via its N-terminal kinase and ubiquitin-activating and -conjugating domains

Aberrant expression of androgen receptor (AR) coregulators has been linked to progression of prostate cancers to castration resistance. Using the repressed transactivator yeast two-hybrid system, we found that TATA binding protein-associated factor 1 (TAF1) interacted with the AR. In tissue microarrays, TAF1 was shown to steadily increase with duration of neoadjuvant androgen withdrawal and with progression to castration resistance. Glutathione S-transferase pulldown assays established that TAF1 bound through its acetylation and ubiquitin-activating/conjugating domains (E1/E2) directly to the AR N terminus. Coimmunoprecipitation and ChIP assays revealed colocalization of TAF1 and AR on the prostate-specific antigen promoter/enhancer in prostate cancer cells. With respect to modulation of AR activity, overexpression of TAF1 enhanced AR activity severalfold, whereas small interfering RNA knockdown of TAF1 significantly decreased AR transactivation. Although full-length TAF1 showed enhancement of both AR and some generic gene transcriptional activity, selective AR coactivator activity by TAF1 was demonstrated in transactivation experiments using cloned N-terminal kinase and E1/E2 functional domains. In keeping with AR coactivation by the ubiquitin-activating and -conjugating domain, TAF1 was found to greatly increase the cellular amount of polyubiquitinated AR. In conclusion, our results indicate that increased TAF1 expression is associated with progression of human prostate cancers to the lethal castration-resistant state. Because TAF1 is a coactivator of AR that binds and enhances AR transcriptional activity, its overexpression could be part of a compensatory mechanism adapted by cancer cells to overcome reduced levels of circulating androgens.

Suppression of the androgen receptor function by quercetin through protein-protein interactions of Sp1, c-Jun, and the androgen receptor in human prostate cancer cells

We have previously reported that the increase in c-Jun expression induced by quercetin inhibited androgen receptor (AR) transactivation, and Sp1 was involved in quercetin-mediated downregulation of AR activity. Transient transfection assays in this work revealed that co-expression of c-Jun quenched Sp1-induced production of luciferase activity driven by AR promoter or three copies of Sp1 binding elements in the AR promoter. Moreover, c-Jun repressed AR-mediated luciferase activity via androgen-response elements (AREs) of the hK2 gene, while this suppression could be restored partially by cotransfection of Sp1 expression plasmid. The physical associations of c-Jun, Sp1, and AR induced by quercetin were further demonstrated by co-immunoprecipitation experiments. In addition, quercetin-mediated repression of AR expression and activity was partially reversed by blocking of JNK signaling pathway. These results suggested that c-Jun might play an important role in the suppression of AR expression and activity in the presence of quercetin, and association of a c-Jun/Sp1/AR protein complex induced by quercetin represented a novel mechanism that was involved in down-regulation of the AR function in prostate cancer cells.

Transgelin induces apoptosis of human prostate LNCaP cells through its interaction with p53

The androgen receptor (AR) and its coregulators have important roles in the carcinogenesis of prostate cancer. p53 is an important tumour suppressor gene, and the absence of a fundamental p53 response may predispose to cancer. Transgelin, known as an ARA54-associated AR inhibitor, can suppress AR function in LNCaP cells. In addition to these effects, we aimed to elucidate the proapoptotic effects of the protein on LNCaP and its underlying mechanisms, especially the interaction between transgelin and p53. Cell counting, flow cytometric analysis and terminal deoxynucleotidyl transferase-dUTP nick-end labelling assays were applied to measure the proapoptotic effect of transgelin. Using western blotting of p53 and double immunofluorescence staining of p53 with transgelin, we show that transfection of transgelin results in increasing cytoplasmic translocation of p53 and upregulation of p53 expression. We also found an interaction between transgelin and p53 in vivo by mammalian two-hybrid and coimmunoprecipitation assays. The activation of the mitochondria-associated apoptosis pathway was observed in LNCaP cells after transfection with transgelin. These results are indicative of p53-mediated mitochondria-associated apoptotic effects of transgelin on LNCaP cells in addition to its known suppressive effects on the AR pathway.

Gene expression profile of androgen modulated genes in the murine fetal developing lung

BACKGROUND

Accumulating evidences suggest that sex affects lung development. Indeed, a higher incidence of respiratory distress syndrome is observed in male compared to female preterm neonates at comparable developmental stage and experimental studies demonstrated an androgen-related delay in male lung maturation. However, the precise mechanisms underlying these deleterious effects of androgens in lung maturation are only partially understood.

METHODS

To build up a better understanding of the effect of androgens on lung development, we analyzed by microarrays the expression of genes showing a sexual difference and those modulated by androgens. Lungs of murine fetuses resulting from a timely mating window of 1 hour were studied at gestational day 17 (GD17) and GD18, corresponding to the period of surge of surfactant production. Using injections of the antiandrogen flutamide to pregnant mice, we hunted for genes in fetal lungs which are transcriptionally modulated by androgens.

RESULTS

Results revealed that 1844 genes were expressed with a sexual difference at GD17 and 833 at GD18. Many genes were significantly modulated by flutamide: 1597 at GD17 and 1775 at GD18. Datasets were analyzed by using in silico tools for reconstruction of cellular pathways. Between GD17 and GD18, male lungs showed an intensive transcriptional activity of proliferative pathways along with the onset of lung differentiation. Among the genes showing a sex difference or an antiandrogen modulation of their expression, we specifically identified androgen receptor interacting genes, surfactant related genes in particularly those involved in the pathway leading to phospholipid synthesis, and several genes of lung development regulator pathways. Among these latter, some genes related to Shh, FGF, TGF-beta, BMP, and Wnt signaling are modulated by sex and/or antiandrogen treatment.

CONCLUSION

Our results show clearly that there is a real delay in lung maturation between male and female in this period, the latter pursuing already lung maturation while the proper is not yet fully engaged in the differentiation processes at GD17. In addition, this study provides a list of genes which are under the control of androgens within the lung at the moment of surge of surfactant production in murine fetal lung.

Androgen receptor-dependent transactivation of growth arrest-specific gene 6 mediates inhibitory effects of testosterone on vascular calcification

Recent epidemiological studies have found that androgen deficiency is associated with a higher incidence of cardiovascular disease in men. However, little is known about the mechanism underlying the cardioprotective effects of androgens. Here we show the inhibitory effects of testosterone on vascular calcification and a critical role of androgen receptor (AR)-dependent transactivation of growth arrest-specific gene 6 (Gas6), a key regulator of inorganic phosphate (P(i))-induced calcification of vascular smooth muscle cells (VSMC). Testosterone and nonaromatizable androgen dihydrotestosterone inhibited P(i)-induced calcification of human aortic VSMC in a concentration-dependent manner. Androgen inhibited P(i)-induced VSMC apoptosis, an essential process for VSMC calcification. The effects on VSMC calcification were mediated by restoration of P(i)-induced down-regulation of Gas6 expression and a subsequent reduction of Akt phosphorylation. These effects of androgen were blocked by an AR antagonist, flutamide, but not by an estrogen receptor antagonist, ICI 182,780. We then explored the mechanistic role of the AR in Gas6 expression and found an abundant expression of AR predominantly in the nucleus of VSMC and two consensus ARE sequences in the Gas6 promoter region. Dihydrotestosterone stimulated Gas6 promoter activity, and this effect was abrogated by flutamide and by AR siRNA. Site-specific mutation revealed that the proximal ARE was essential for androgen-dependent transactivation of Gas6. Furthermore, chromatin immunoprecipitation assays demonstrated ligand-dependent binding of the AR to the proximal ARE of Gas6. These results indicate that AR signaling directly regulates Gas6 transcription, which leads to inhibition of vascular calcification, and provides a mechanistic insight into the cardioprotective action of androgens.

Synthesis, structure-activity relationships, and characterization of novel nonsteroidal and selective androgen receptor modulators

Herein we describe the discovery of ACP-105 (1), a novel and potent nonsteroidal selective androgen receptor modulator (SARM) with partial agonist activity relative to the natural androgen testosterone. Compound 1 was developed from a series of compounds found in a HTS screen using the receptor selection and amplification technology (R-SAT). In vivo, 1 improved anabolic parameters in a 2-week chronic study in castrated male rats. In addition to compound 1, a number of potent antiandrogens were discovered from the same series of compounds whereof one compound, 13, had antagonist activity at the AR T877A mutant involved in prostate cancer.

Dihydrotestosterone activates the MAPK pathway and modulates maximum isometric force through the EGF receptor in isolated intact mouse skeletal muscle fibres

It is generally believed that steroid hormones have both genomic and non-genomic (rapid) actions. Although the latter form an important component of the physiological response of these hormones, little is known about the cellular signalling pathway(s) mediating these effects and their physiological functions in adult mammalian skeletal muscle fibres. Therefore, the primary aim of this study was to investigate the non-genomic actions of dihydrotestosterone (DHT) and their physiological role in isolated intact mammalian skeletal muscle fibre bundles. Our results show that treating the fibre bundles with physiological concentrations of DHT increases both twitch and tetanic contractions in fast twitch fibres. However, it decreases them in slow twitch fibres. These changes in force are accompanied by an increase in the phosphorylation of MAPK/ERK1/2 in both fibre types and that of regulatory myosin light chains in fast twitch fibres. Both effects were insensitive to inhibitors of Src kinase, androgen receptor, insulin-like growth factor 1 receptor and platelet-derived growth factor receptor. However, they were abolished by the MAPK/ERK1/2 kinase inhibitor PD98059 and the epidermal growth factor (EGF) receptor inhibitor tyrphostin AG 1478. In contrast, testosterone had no effect on force and increased the phosphorylation of ERK1/2 in slow twitch fibres only. From these results we conclude that sex steroids have non-genomic actions in isolated intact mammalian skeletal muscle fibres. These are mediated through the EGF receptor and one of their main physiological functions is the enhancement of force production in fast twitch skeletal muscle fibres.

Expression, purification and primary crystallographic study of human androgen receptor in complex with DNA and coactivator motifs

The androgen receptor (AR) is a DNA-binding and hormone-activated transcription factor that plays critical roles in the development and progression of prostate cancer. The transcriptional function of AR is modulated by intermolecular interactions with DNA elements and coactivator proteins, as well as intramolecular interactions between AR domains; thus, the structural information from the full-length AR or a multi-domain fragment is essential for understanding the molecular basis of AR functions. Here we report the expression and purification of full-length AR protein and of a fragment containing its DNA-binding and ligand-binding domains connected by the hinge region in the presence of its natural ligand, dihydrotestosterone. Crystals of ligand-bound full-length AR and of the AR fragment in complex with DNA elements and coactivator motifs have been obtained and diffracted to low resolutions. These results help establish a foundation for pursuing further crystallographic studies of an AR/DNA complex.

TRIM24 mediates ligand-dependent activation of androgen receptor and is repressed by a bromodomain-containing protein, BRD7, in prostate cancer cells

The androgen receptor (AR) is a ligand-dependent transcription factor that belongs to the family of nuclear receptors, and its activity is regulated by numerous AR coregulators. AR plays an important role in prostate development and cancer. In this study, we found that TRIM24/transcriptional intermediary factor 1alpha (TIF1alpha), which is known as a ligand-dependent nuclear receptor co-regulator, interacts with AR and enhances transcriptional activity of AR by dihydrotestosterone in prostate cancer cells. We showed that TRIM24 functionally interacts with TIP60, which acts as a coactivator of AR and synergizes with TIP60 in the transactivation of AR. We also showed that TRIM24 binds to bromodomain containing 7 (BRD7), which can negatively regulate cell proliferation and growth. A luciferase assay indicated that BRD7 represses the AR transactivation activity upregulated by TRIM24. These findings indicate that TRIM24 regulates AR-mediated transcription in collaboration with TIP60 and BRD7.

Identification of epidermal growth factor receptor (EGFR) exon 20 single nucleotide polymorphism in Chinese squamous cell carcinoma of head and neck (SCCHN)

CONCLUSION

The 78th single nucleotide polymorphism (SNP) in exon 20 of epidermal growth factor receptor (EGFR) might be a predictor of the clinical course of squamous cell carcinoma of the head and neck (SCCHN), and genetic predisposition could influence the progression of SCCHN in Chinese subjects.

OBJECTIVE

To analyze the clinical significance of EGFR SNP in Chinese SCCHN patients.

MATERIALS AND METHODS

Direct sequencing of exons 18-21 was used to analyze somatic mutations of EGFR. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to evaluate the expression level of EGFR. The chi-square test and Kaplan-Meier method were the main statistical methods used to analyze the correlation of the investigated variables and prognostic significance.

RESULTS

In analyzing exons 18-21 of EGFR in 96 patients with SCCHN, only one SNP was found in the 78th site of exon 20 and it mostly existed in specimens coming from the hypopharynx. Further statistical analysis showed that among the clinical or histopathologic parameters, the 78th SNP had a close relationship with earlier stage and more localized primary carcinoma, while at present the analysis did not support the proposition that the SNP was an independent prognostic factor.

Retinoblastoma protein plays multiple essential roles in the terminal differentiation of Sertoli cells

Retinoblastoma protein (RB) plays crucial roles in cell cycle control and cellular differentiation. Specifically, RB impairs the G(1) to S phase transition by acting as a repressor of the E2F family of transcriptional activators while also contributing towards terminal differentiation by modulating the activity of tissue-specific transcription factors. To examine the role of RB in Sertoli cells, the androgen-dependent somatic support cell of the testis, we created a Sertoli cell-specific conditional knockout of Rb. Initially, loss of RB has no gross effect on Sertoli cell function because the mice are fertile with normal testis weights at 6 wk of age. However, by 10-14 wk of age, mutant mice demonstrate severe Sertoli cell dysfunction and infertility. We show that mutant mature Sertoli cells continue cycling with defective regulation of multiple E2F1- and androgen-regulated genes and concurrent activation of apoptotic and p53-regulated genes. The most striking defects in mature Sertoli cell function are increased permeability of the blood-testis barrier, impaired tissue remodeling, and defective germ cell-Sertoli cell interactions. Our results demonstrate that RB is essential for proper terminal differentiation of Sertoli cells.

Increased expression of androgen receptor sensitizes prostate cancer cells to low levels of androgens

Androgen receptor (AR) is known to be overexpressed in castration-resistant prostate cancer. To interrogate the functional significance of the AR level, we established two LNCaP cell sublines expressing in a stable fashion two to four times (LNCaP-ARmo) and four to six times (LNCaP-ARhi) higher level of AR than the parental cell line expressing the empty vector (LNCaP-pcDNA3.1). LNCaP-ARhi cell line grew faster than the control line in low concentrations, especially in 1 nmol/L 5alpha-dihydrotestosterone (DHT). Microarray-based transcript profiling and subsequent unsupervised hierarchical clustering showed that LNCaP-ARhi cells clustered together with VCaP cells, containing endogenous AR gene amplification and overexpression, indicating the central role of AR in the overall regulation of gene expression in prostate cancer cells. Two hundred forty genes showed >2-fold changes on DHT treatment in LNCaP-ARhi at 4 h time point, whereas only 164 and 52 showed changes in LNCaP-ARmo and LNCaP-pcDNA3.1, respectively. Many androgen-regulated genes were upregulated in LNCaP-ARhi at 10-fold lower concentration of DHT than in control cells. DHT (1 nmol/L) increased expression of several cell cycle-associated genes in LNCaP-ARhi cells. ChIP-on-chip assay revealed the presence of chromatin binding sites for AR within +/-200 kb of most of these genes. The growth of LNCaP-ARhi cells was also highly sensitive to cyclin-dependent kinase inhibitor, roscovitine, at 1nmol/L DHT. In conclusion, our results show that overexpression of AR sensitizes castration-resistant prostate cancer cells to the low levels of androgens. The activity of AR signaling pathway is regulated by the levels of both ligand and the receptor.

Functional screening of FxxLF-like peptide motifs identifies SMARCD1/BAF60a as an androgen receptor cofactor that modulates TMPRSS2 expression

Androgen receptor (AR) transcriptional activity is tightly regulated by interacting cofactors and cofactor complexes. The best described cofactor interaction site in the AR is the hormone-induced coactivator binding groove in the ligand-binding domain, which serves as a high-affinity docking site for FxxLF-like motifs. This study aimed at identifying novel AR cofactors by in silico selection and functional screening of FxxLF-like peptide motifs. Candidate interacting motifs were selected from a proteome-wide screening and from a supervised screening focusing on components of protein complexes involved in transcriptional regulation. Of the 104 peptides tested, 12 displayed moderate to strong in vivo hormone-dependent interactions with AR. For three of these, ZBTB16/PLZF, SMARCA4/BRG1, and SMARCD1/BAF60a, the full-length protein was tested for interaction with AR. Of these, BAF60a, a subunit of the SWI/SNF chromatin remodeling complex, displayed hormone-dependent interactions with AR through its FxxFF motif. Vice versa, recruitment of BAF60a by the AR required an intact coactivator groove. BAF60a depletion by small interfering RNA in LNCaP cells demonstrated differential effects on expression of endogenous AR target genes. AR-driven expression of TMPRSS2 was almost completely blocked by BAF60a small interfering RNA. In summary, our data demonstrate that BAF60a directly interacts with the coactivator groove in the AR ligand-binding domain via its FxxFF motif, thereby selectively activating specific AR-driven promoters.

Dose-dependent effects of androgens on outcome after focal cerebral ischemia in adult male mice

Males exhibit greater histologic and behavioral impairment after stroke than do age-matched females. However, the contribution of androgens to stroke outcome remains unclear. We compared outcomes from middle cerebral artery occlusion (MCAO) in castrated mice with those in testosterone- or dihydrotestosterone (DHT)-replaced castrated mice. Castrates treated with 1.5 mg testosterone or 0.5 mg DHT before MCAO showed smaller infarct volumes (hemisphere: 27 or 26%) at 24 h after 90 mins MCAO than did untreated castrates (37%), whereas 5 mg testosterone or 1.5 mg DHT exacerbated infarcts (53 or 51%). These outcomes were blocked by the androgen receptor antagonist, flutamide, suggesting that androgen receptors mediate these responses to ischemia. We further evaluated long-term outcomes with a milder 60-min MCAO in castrates treated with the protective 1.5 mg testosterone dose. Consistent with data obtained at 24 h reperfusion, the infarct volume was decreased at 9 days reperfusion. Neurobehavioral analysis showed that motor functional recovery was improved during the first 3 days of reperfusion, but not improved at 7 days. We conclude that testosterone exhibits dose-dependent and time-sensitive effects after ischemia and that testosterone is likely to be an important factor in sex-linked differences in cerebrovascular disease.

Kinetic and thermodynamic characterization of dihydrotestosterone-induced conformational perturbations in androgen receptor ligand-binding domain

Ligand-induced conformational perturbations in androgen receptor (AR) are important in coactivator recruitment and transactivation. However, molecular rearrangements in AR ligand-binding domain (AR-LBD) associated with agonist binding and their kinetic and thermodynamic parameters are poorly understood. We used steady-state second-derivative absorption and emission spectroscopy, pressure and temperature perturbations, and 4,4'-bis-anilinonaphthalene 8-sulfonate (bis-ANS) partitioning to determine the kinetics and thermodynamics of the conformational changes in AR-LBD after dihydrotestosterone (DHT) binding. In presence of DHT, the second-derivative absorption spectrum showed a red shift and a change in peak-to-peak distance. Emission intensity increased upon DHT binding, and center of spectral mass was blue shifted, denoting conformational changes resulting in more hydrophobic environment for tyrosines and tryptophans within a more compact DHT-bound receptor. In pressure perturbation calorimetry, DHT-induced energetic stabilization increased the Gibbs free energy of unfolding to 8.4 +/- 1.3 kcal/mol from 3.5 +/- 1.6 kcal/mol. Bis-ANS partitioning studies revealed that upon DHT binding, AR-LBD underwent biphasic rearrangement with a high activation energy (13.4 kcal/mol). An initial, molten globule-like burst phase (k approximately 30 sec(-1)) with greater solvent accessibility was followed by rearrangement (k approximately 0.01 sec(-1)), leading to a more compact conformation than apo-AR-LBD. Molecular simulations demonstrated unique sensitivity of tyrosine and tryptophan residues during pressure unfolding with rearrangement of residues in the coactivator recruitment surfaces distant from the ligand-binding pocket. In conclusion, DHT binding leads to energetic stabilization of AR-LBD domain and substantial rearrangement of residues distant from the ligand-binding pocket. DHT binding to AR-LBD involves biphasic receptor rearrangement including population of a molten globule-like intermediate state.

Degradation and beyond: control of androgen receptor activity by the proteasome system

The androgen receptor (AR) is a transcription factor belonging to the family of nuclear receptors which mediates the action of androgens in the development of urogenital structures. AR expression is regulated post-translationally by the ubiquitin/proteasome system. This regulation involves more complex mechanisms than typical degradation. The ubiquitin/proteasome system may regulate AR via mechanisms that do not engage in receptor turnover. Given the critical role of AR in sexual development, this complex regulation is especially important. Deregulation of AR signalling may be a causal factor in prostate cancer development. AR is the main target in prostate cancer therapies. Due to the critical role of the ubiquitin/proteasome system in AR regulation, current research suggests that targeting AR degradation is a promising approach.

A novel androgen receptor-binding element modulates Cdc6 transcription in prostate cancer cells during cell-cycle progression

The androgen receptor (AR) plays a pivotal role in the onset and progression of prostate cancer by promoting cellular proliferation. Recent studies suggest AR is a master regulator of G1-S progression and possibly a licensing factor for DNA replication yet the mechanisms remain poorly defined. Here we report that AR targets the human Cdc6 gene for transcriptional regulation. Cdc6 is an essential regulator of DNA replication in eukaryotic cells and its mRNA expression is inversely modulated by androgen or antiandrogen treatment in androgen-sensitive prostate cancer cells. AR binds at a distinct androgen-response element (ARE) in the Cdc6 promoter that is functionally required for androgen-dependent Cdc6 transcription. We found that peak AR occupancy at the novel ARE occurs during the G1/S phase concomitant with peak Cdc6 mRNA expression. We also identified several of the coactivators and corepressors involved in AR-dependent Cdc6 transcriptional regulation in vivo and further characterized ligand-induced alterations in histone acetylation and methylation at the Cdc6 promoter. Significantly, AR silencing in prostate cancer cells markedly decreases Cdc6 expression and androgen-dependent cellular proliferation. Collectively, our results suggest that Cdc6 is a key regulatory target for AR and provide new insights into the mechanisms of prostate cancer cell proliferation.

Amino-terminus domain of the androgen receptor as a molecular target to prevent the hormonal progression of prostate cancer

Prostate cancer has a propensity to metastasize to the bone. Currently the only effective systemic treatment for these patients is androgen ablation therapy. However, the tumor will invariably progress to an androgen-independent stage and the patient will succumb to his disease within approximately 2 years. The earliest indication of hormonal progression is the rising titer of serum prostate specific antigen. Current evidence implicates the androgen receptor (AR) as a key factor in maintaining the growth of prostate cancer cells in an androgen-depleted state. Under normal conditions, binding of ligand activates the receptor, allowing it to effectively bind to its respective DNA element. However, AR is also transformed in the absence of androgen (ligand-independent activation) in prostate cells via multiple protein kinase pathways and the interleukin-6 (IL-6) pathway that converge upon the N-terminal domain of the AR. This domain is the main region for phosphorylation and is also critical for normal coregulator recruitment. Here we discuss evidence supporting the role of the AR, IL-6 and other protein kinase pathways in the hormonal progression of prostate cancer to androgen independence and the mechanisms involved in activation of the AR by these pathways. Receptor-targeted therapy, especially potential drugs targeting the N-terminal domain, may effectively prevent or delay the hormonal progression of AR-dependent prostate cancer.

Selective androgen receptor modulators as function promoting therapies

PURPOSE OF REVIEW

The past decade has witnessed an unprecedented discovery effort to develop selective androgen receptor modulators (SARMs) that improve physical function and bone health without adversely affecting the prostate and cardiovascular outcomes. This review describes the historical evolution, the rationale for SARM development, and the mechanisms of testosterone action and SARM selectivity.

RECENT FINDINGS

Although steroidal SARMs have been around since the 1940s, a number of nonsteroidal SARMs that do not serve as substrates for CYP19 aromatase or 5alpha-reductase, act as full agonists in muscle and bone and as partial agonists in prostate are in development. The differing interactions of steroidal and nonsteroidal compounds with androgen receptor (AR) contribute to their unique pharmacologic actions. Ligand binding induces specific conformational changes in the ligand-binding domain, which could modulate surface topology and protein-protein interactions between AR and coregulators, resulting in tissue-specific gene regulation. Preclinical studies have demonstrated the ability of SARMs to increase muscle and bone mass in preclinical rodent models with varying degree of prostate sparing. Phase I trials of SARMs in humans have reported modest increments in fat-free mass.

SUMMARY

SARMs hold promise as a new class of function promoting anabolic therapies for a number of clinical indications, including functional limitations associated with aging and chronic disease, frailty, cancer cachexia, and osteoporosis.

Nuclear actin and actin-binding proteins in the regulation of transcription and gene expression

Nuclear actin is involved in the transcription of all three RNA polymerases, in chromatin remodeling and in the formation of heterogeneous nuclear ribonucleoprotein complexes, as well as in recruitment of the histone modifier to the active gene. In addition, actin-binding proteins (ABPs) control actin nucleation, bundling, filament capping, fragmentation and monomer availability in the cytoplasm. In recent years, more and more attention has focused on the role of actin and ABPs in the modulation of the subcellular localization of transcriptional regulators. This review focuses on recent developments in the study of transcription and transcriptional regulation by nuclear actin, and the regulation of muscle-specific gene expression, nuclear receptor and transcription complexes by ABPs. Among the ABPs, striated muscle activator of Rho signaling and actin-binding LIM protein regulate actin dynamics and serum response factor-dependent muscle-specific gene expression. Functionally and structurally unrelated cytoplasmic ABPs interact cooperatively with nuclear receptor and regulate its transactivation. Furthermore, ABPs also participate in the formation of transcription complexes.

Care of women with XY karyotype: a clinical practice guideline

OBJECTIVE

To provide an evidence-based guideline for professionals working with XY women.

DESIGN

Review including patient cases from a Danish fertility clinic.

SETTING

University-associated scientific unit and fertility clinic.

PATIENT(S)

Three selected cases.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Evaluation of etiology, diagnosis, treatment, and associated disorders in XY women.

RESULT(S)

Many gene mutations can cause abnormal fetal development leading to androgen insensitivity syndrome or gonadal dysgenesis disorders. Females with these disorders have an XY karyotype but look like girls. They are mostly diagnosed at puberty, and the condition will often lead to serious psychological problems. Increased risk of malignancies and problems with pregnancy and infertility are other aspects that should be considered. This guideline will aid doctors in caring for XY females.

CONCLUSION(S)

A precise diagnosis is important, because the treatment possibilities (e.g., use of allogenic oocytes) depend on the subgroup to which the XY female belongs.

Androgen receptor roles in spermatogenesis and fertility: lessons from testicular cell-specific androgen receptor knockout mice

Androgens are critical steroid hormones that determine the expression of the male phenotype, including the outward development of secondary sex characteristics as well as the initiation and maintenance of spermatogenesis. Their actions are mediated by the androgen receptor (AR), a member of the nuclear receptor superfamily. AR functions as a ligand-dependent transcription factor, regulating expression of an array of androgen-responsive genes. Androgen and the AR play important roles in male spermatogenesis and fertility. The recent generation and characterization of male total and conditional AR knockout mice from different laboratories demonstrated the necessity of AR signaling for both external and internal male phenotype development. As expected, the male total AR knockout mice exhibited female-typical external appearance (including a vagina with a blind end and a clitoris-like phallus), the testis was located abdominally, and germ cell development was severely disrupted, which was similar to a human complete androgen insensitivity syndrome or testicular feminization mouse. However, the process of spermatogenesis is highly dependent on autocrine and paracrine communication among testicular cell types, and the disruption of AR throughout an experimental animal cannot answer the question about how AR in each type of testicular cell can play roles in the process of spermatogenesis. In this review, we provide new insights by comparing the results of cell-specific AR knockout in germ cells, peritubular myoid cells, Leydig cells, and Sertoli cells mouse models that were generated by different laboratories to see the consequent defects in spermatogenesis due to AR loss in different testicular cell types in spermatogenesis. Briefly, this review summarizes these results as follows: 1) the impact of lacking AR in Sertoli cells mainly affects Sertoli cell functions to support and nurture germ cells, leading to spermatogenesis arrest at the diplotene primary spermatocyte stage prior to the accomplishment of first meiotic division; 2) the impact of lacking AR in Leydig cells mainly affects steroidogenic functions leading to arrest of spermatogenesis at the round spermatid stage; 3) the impact of lacking AR in the smooth muscle cells and peritubular myoid cells in mice results in similar fertility despite decreased sperm output as compared to wild-type controls; and 4) the deletion of AR gene in mouse germ cells does not affect spermatogenesis and male fertility. This review tries to clarify the useful information regarding how androgen/AR functions in individual cells of the testis. The future studies of detailed molecular mechanisms in these in vivo animals with cell-specific AR knockout could possibly lead to useful insights for improvements in the treatment of male infertility, hypogonadism, and testicular dysgenesis syndrome, and in attempts to create safe as well as effective male contraceptive methods.

Deleted in breast cancer 1, a novel androgen receptor (AR) coactivator that promotes AR DNA-binding activity

Androgen receptor (AR) plays a critical role in development and maintenance of male reproductive functions and the etiology of prostate cancer. As a ligand-regulated transcription factor, identification and characterization of AR coregulators are essential for understanding the molecular mechanisms underlying its diverse biological functions. Here we reported the identification of a novel AR coactivator, deleted in breast cancer 1 (DBC1), through a biochemical approach. DBC1 interacts with AR in a ligand-stimulated manner and facilitates AR transcriptional activation in transfected cells as well as in Xenopus oocytes. In in vitro gel shift experiments, recombinant DBC1 drastically enhanced AR DNA-binding activity. Expression of DBC1 also enhanced the binding of AR to chromatinized template in vivo, whereas knockdown of DBC1 impaired the binding of AR to endogenous prostate-specific antigen (PSA) gene in the prostate cancer cell line LNCaP. Thus, our data identify DBC1 as a novel AR coactivator.

Oestradiol-induced spermatogenesis requires a functional androgen receptor

Spermatogenesis requires androgen but, paradoxically, oestradiol (E2) treatment stimulates spermatogenic development in gonadotrophin- and androgen-deficient hypogonadal (hpg) mice. The mechanisms of E2-induced spermatogenesis were investigated by determining intratesticular E2 levels and testis cell populations in E2-treated hpg male mice, and E2 spermatogenic actions were determined in androgen receptor-knockout (ARKO) mice. Despite increased serum E2 concentrations (150-300 pmol L(-1)), intratesticular E2 concentrations declined fivefold (P < 0.001) in E2-treated v. untreated hpg male mice. Serum FSH reached 40% of normal and total testicular numbers of known FSH-responsive Sertoli, spermatogonia and meiotic spermatocyte populations were significantly (P < 0.001) elevated 1.7-, 4- and 13-fold, respectively. However, E2 administration also increased androgen-dependent pachytene spermatocytes and post-meiotic spermatids to levels comparable with testosterone-treated hpg testes. Selective investigation of androgen receptor involvement used E2-treated ARKO mice, which were found to exhibit increased (1.6-fold; P < 0.05) intratesticular E2 concentrations and suppression of the elevated serum gonadotrophins, although FSH remained twofold higher than normal. However, testis size and total Sertoli, spermatogonia and spermatocyte numbers were not increased in E2-treated ARKO male mice. Therefore, E2-stimulated murine spermatogenic development occurs with markedly suppressed and not elevated intratesticular E2 levels and displays an absolute requirement for functional androgen receptors. We propose that this paradoxical E2 spermatogenic response is explained by predominantly extratesticular E2 actions, increasing FSH to combine with residual androgen activity in hpg testes to stimulate pre- to post-meiotic development.

Androgen modulation of coregulator expression in prostate cancer cells

Aberrant coregulator expression that occurs during prostate cancer (PCa) progression correlates with poor prognosis and aggressive disease. This has been attributed to the ability to regulate androgen receptor-mediated transcription. We have shown previously that the androgenic milieu regulates the expression of the coactivators p300 and FHL2, with severe consequences for PCa cell proliferation and androgen receptor transcriptional activity. To determine the extent of androgen dependency of coregulator genes, we designed a cDNA-mediated annealing, selection, extension, and ligation RNA profiling array that probes the expression of 186 coregulators. Using this assay, we demonstrated androgen control over approximately 30% of coregulator genes in PCa cells. For a subset of 15 functionally diverse coregulators, androgen regulation was confirmed using real-time RT-PCR and immunoblotting. The extent, dose dependency, and kinetics by which androgens affect coregulator expression differed widely, indicating diverse molecular mechanisms underlying these effects. Moreover, differences in coregulator expression were observed between isogenic androgen-dependent and castration-recurrent PCa cells. Small interfering RNA-mediated changes in coregulator expression had profound effects on cell proliferation, which were most pronounced in castration-recurrent cells. Taken together, our integrated approach combining expression profiling, characterization of androgen-dependent coregulator expression, and validation of the importance of altered coregulator expression for cell proliferation identified several potential novel therapeutic targets for PCa treatment.

Inhibition of androgen receptor transcriptional activity as a novel mechanism of action of arsenic

Environmental sodium arsenite is a toxin that is associated with male infertility due to decreased and abnormal sperm production. Arsenic trioxide (ATO), another inorganic trivalent semimetal, is an effective therapy for acute promyelocytic leukemia, and there is investigation of its possible efficacy in prostate cancer. However, the mechanism of arsenic action in male urogenital tract tissues is not clear. Because the androgen receptor (AR) plays an important role in spermatogenesis and prostate cancer, we explored the possibility that trivalent arsenic regulates AR function. We found that arsenic inhibited AR transcriptional activity in prostate cancer and Sertoli cells using reporter gene assays testing several androgen response element-containing regions and by assessing native target gene expression. Arsenic inhibition of AR activity was not due to down-regulation of AR protein levels, decreased hormone binding to AR, disruption of AR nuclear translocation, or interference with AR-DNA binding in vitro. However, chromatin immunoprecipitation studies revealed that arsenic inhibited AR recruitment to an AR target gene enhancer in vivo. Consistent with a deficiency in AR-chromatin binding, arsenic disrupted AR amino and carboxyl termini interaction. Furthermore, ATO caused a significant decrease in prostate cancer cell proliferation that was more pronounced in cells expressing AR compared with cells depleted of AR. In addition, inhibition of AR activity by ATO and by the AR antagonist, bicalutamide, was additive. Thus, arsenic-induced male infertility may be due to inhibition of AR activity. Further, because AR is an important target in prostate cancer therapy, arsenic may serve as an effective therapeutic option.

Identification and characterization of the minimal androgen-regulated kidney-specific kidney androgen-regulated protein gene promoter

The kidney androgen-regulated protein (Kap) gene is tissue specific and regulated by androgen in mouse kidney proximal tubule cells (PTCs). In the present study, we aimed to identify the minimal PTC-specific androgen-regulated Kap promoter and analyze its androgen response elements (AREs). A deletion series of the Kap1542 promoter/luciferase constructs were assayed in opossum kidney (OK) PTCs in the presence or absence of 15 nM dihydrotestosterone (DHT). Kap1542 and Kap637 had low activity and no androgen induction; Kap224 had a basal activity that was 4- to 5-fold higher than that of Kap1542, but was only slightly induced by DHT. Kap147 had a basal activity that was 2- to 3-fold higher than that of Kap1542 and was induced by DHT 4- to 6-fold. Kap77 abolished basal promoter activity but was still induced by DHT. Results showed that, in vitro, Kap147 was a minimal androgen-regulated promoter. Transient transfection in different cells demonstrated that Kap147 specifically initiated reporter gene expression in PTCs. Sequence analysis revealed two potential AREs located at positions -124 and -39 of Kap147. Mutational assays showed that only the ARE at -124 was involved in androgen response in OK cells. Electrophoretic mobility shift assay also verified -124 ARE bound specifically to androgen receptor. In conclusion, we defined the minimal Kap147 promoter that may be a good model for the study of kidney PTC-specific expression and molecular mechanisms that lead to an androgen-specific responsiveness in vivo.

Crystallization and preliminary X-ray analysis of the human androgen receptor ligand-binding domain with a coactivator-like peptide and selective androgen receptor modulators

The ligand-binding domain of the human androgen receptor has been cloned, overproduced and crystallized in the presence of a coactivator-like 11-mer peptide and two different nonsteroidal ligands. The crystals of the two ternary complexes were isomorphous and belonged to space group P2(1)2(1)2(1), with one molecule in the asymmetric unit. They diffracted to 1.7 and 1.95 A resolution, respectively. Structure determination of these two complexes will help in understanding the mode of binding of selective nonsteroidal androgens versus endogenous steroidal ligands and possibly the origin of their tissue selectivity.

Androgenic control of transforming growth factor-beta signaling in prostate epithelial cells through transcriptional suppression of transforming growth factor-beta receptor II

The androgen receptor cross-talks with transforming growth factor-beta (TGF-beta) through mechanisms that remain poorly understood. Here we provide strong evidence that 5alpha-dihydrotestosterone (DHT) intercepts the ability of prostate epithelial cells to undergo TGF-beta-induced apoptosis, and present a new model for this androgenic effect. We report that DHT decreases the level of TGF-beta receptor II (TbetaRII) through a transcriptional mechanism, leading to suppression of the ability of TGF-beta to down-regulate expression of Bcl-xL and cyclin Ds, activate caspase-3, and induce apoptosis. Promoter analysis, DNA pulldown, and electrophoretic mobility shift assays support that transcriptional down-regulation of TbetaRII by DHT occurs through Sp1/Sp3 response elements, with the binding of Sp1 to the TbetaRII promoter being suppressed by DHT, largely driven by loss of Sp1 protein and/or activity. These results provide fresh insight on the mechanism of growth control by androgens and the progression of prostate cancer to androgen independence. [Cancer Res 2008;68(19):8173-82].

Selective androgen receptor modulators in preclinical and clinical development

Androgen receptor (AR) plays a critical role in the function of several organs including primary and accessory sexual organs, skeletal muscle, and bone, making it a desirable therapeutic target. Selective androgen receptor modulators (SARMs) bind to the AR and demonstrate osteo- and myo-anabolic activity; however, unlike testosterone and other anabolic steroids, these nonsteroidal agents produce less of a growth effect on prostate and other secondary sexual organs. SARMs provide therapeutic opportunities in a variety of diseases, including muscle wasting associated with burns, cancer, or end-stage renal disease, osteoporosis, frailty, and hypogonadism. This review summarizes the current standing of research and development of SARMs, crystallography of AR with SARMs, plausible mechanisms for their action and the potential therapeutic indications for this emerging class of drugs.

DNA dependent recruitment of DDX17 and other interacting proteins by the human androgen receptor

An oligonucleotide-based assay (OBA) was used to identify novel co-factors that can be recruited by the deoxyribonucleic acid (DNA)-bound androgen receptor (AR). Nuclear extracts obtained from LNCaP cells, after incubation with R1881, were incubated with biotinylated oligonucleotides bound to streptavidin coated beads. The oligonucleotides contain 3 copies in tandem of the androgen responsive element ARE1 from the prostate specific antigen (PSA) gene promoter. As control incubation, a scrambled version of the tandem ARE1 was used. Immunoblots of the eluents revealed that the AR was bound to the ARE1 oligonucleotide and to a much lesser extent to the scrambled oligonucleotide. Proteins eluted from the oligonucleotides, were separated on a 5-15% sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) gradient gel, followed by identification using mass spectrometry. Identified proteins were scored for having one or more of the following known properties: nuclear localization, involved in transcription regulation, involvement in steroid hormone receptor (SHR) function, or specifical involvement in AR function. A total number of 85 nuclear proteins were found in two separate OBAs. Based on peptide counting, we found enrichment of 7 proteins eluted from the ARE1 oligonucleotide, compared to the scrambled oligonucleotide. Taken together with the obtained scores, these proteins are considered putative AR co-factors. One of these proteins, DDX17, is known to be a co-factor for estrogen receptor alpha (ERalpha), but has never been associated with AR function. The results indicate that the ARE oligonucleotide-based assay may allow enrichment of new candidate DNA-bound AR interacting proteins.

SUMOylation and De-SUMOylation: wrestling with life's processes

The small ubiquitin-like modifier (SUMO) is a ubiquitin-like protein that covalently modifies a large number of cellular proteins. SUMO modification has emerged as an important regulatory mechanism for protein function and localization. SUMOylation is a dynamic process that is mediated by activating (E1), conjugating (E2), and ligating (E3) enzymes and readily reversed by a family of ubiquitin-like protein-specific proteases (Ulp) in yeast and sentrin/SUMO-specific proteases (SENP) in human. This review will focus on the de-SUMOylating enzymes with special attention to their biological function.

Expression of the muscle atrophy factor muscle atrophy F-box is suppressed by testosterone

The ubiquitin ligase muscle atrophy F-box (MAFbx; also called atrogin-1) is thought to play important roles in muscle loss. Conversely, testosterone reduces atrophy from glucocorticoids or denervation associated with repression of MAFbx. To characterize mechanisms of such repression, the effects of testosterone on MAFbx expression in C2C12 cells were tested. Testosterone reduced MAFbx mRNA levels as well as expression of a reporter gene under the control of 3.1 kb of the human MAFbx promoter. Repression required the androgen receptor (AR) as well as sequences within the first 208 bases upstream of the first codon of the MAFbx gene. This sequence is downstream of known forkhead transcription factor binding sites and testosterone did not alter Forkhead box O 3A phosphorylation. The AR associated with sequences conferring repression in a manner that was stimulated by testosterone and was independent of DNA binding. In gel shift studies, octamer binding transcription factor (Oct)-1 bound two predicted Oct-1 sites within these sequences. Deletion of Oct-1 sites from reporter genes prevented repression by testosterone. Gene knockdown of Oct-1 blocked repression of MAFbx reporter gene activity by testosterone and binding of AR to sequences conferring repression. In conclusion, testosterone represses MAFbx expression via interactions of the AR with Oct-1 that are associated with sequences within the 5' untranslated region of the MAFbx promotor located just upstream of the first codon. This action of testosterone may contribute to beneficial actions of testosterone on muscle.

Modulation of aryl hydrocarbon receptor activity by four and a half LIM domain 2

The aryl hydrocarbon receptor (AhR) mediates transcriptional effects of a diverse array of ligands including environmental contaminants that have been linked to various cancers. The transcriptional activity of the AhR is modulated by different coregulators such as the p160 family members of coactivators and nuclear receptor coactivator 4 (NcoA4). In this study, we provide novel evidence that four and a half LIM only protein 2 (FHL2) interacts with and differentially modulates the transcriptional activity of AhR. Co-immunoprecipitation studies indicate that FHL2 interacts with AhR in a ligand-independent manner but not with its heterodimeric partner, AhR nuclear translocator (ARNT). Overexpression of FHL2 enhanced AhR-mediated expression of a luciferase reporter gene in a dose- and ligand-dependent manner in COS cells. Furthermore, FHL2 cooperated with NcoA4 to synergistically enhance AhR transcriptional activity in these cells. However, the impact of FHL2 on AhR transcriptional activity was cell-specific: FHL2 facilitated AhR action in MCF-7 and PC-3 cells, whereas it suppressed AhR activity in T47D and LNCaP cells. These results of reporter gene studies were corroborated by the impact of FHL2 overexpression on, an established target gene of AhR, cytochrome P450 (CYP1A1) expression. We also demonstrated a potential competition of AhR and androgen receptor (AR) for FHL2 availability in COS cells, as FHL2-facilitation was significantly decreased in the presence of liganded AR. These findings indicate a functional interaction between AhR and FHL2 that modulates the activity of AhR and therefore could affect its role in cancer progression or development.

Altered TNSALP expression and phosphate regulation contribute to reduced mineralization in mice lacking androgen receptor

While androgen receptor (AR)-deficient mice developed osteopenia in endochondral bones due to the high bone turnover with increased bone resorption by osteoclasts, little is known about the mechanism of intramembranous bone loss contributed by AR in osteoblasts. Here, we discovered a dramatic decrease in the area of calcification, new bone, and the number of osteocytes in calvaria from AR-deficient mice related to a reduction in mineralization caused, in part, by the diminished activity of AR-deficient osteoblasts. Enforced AR expression in differentiated osteoblasts boosts mineralization while knockdown of AR expression prevents androgen-induced mineralization. We identified the tissue-nonspecific alkaline phosphatase (TNSALP) and several members of small integrin binding ligand N-linked glycoprotein (SIBLING) gene family as androgen target genes required for AR-mediated bone formation. We show that inorganic phosphate (P(i)) levels and TNSALP activity increased in response to androgen/AR and P(i) signals increase the expression and translocation of AR. The ectopic expression of TNSALP or P(i) partially rescued the bone loss due to AR deficiency. Thus, androgen/AR signaling plays an essential role in bone formation by coordinating the expression of genes associated with phosphate regulation.

Androgen receptor is a new potential therapeutic target for the treatment of hepatocellular carcinoma

BACKGROUND & AIMS

Androgen effects on hepatocellular carcinoma (HCC) remain controversial and androgen ablation therapy to treat HCC also leads to inconsistent results. Here we examine androgen receptor (AR) roles in hepatocarcinogenesis using mice lacking AR in hepatocytes.

METHODS

By using the Cre-Lox conditional knockout mice model injected with carcinogen, we examined the AR roles in hepatocarcinogenesis. We also tested the possible roles of AR in cellular oxidative stress and DNA damage sensing/repairing systems. By using AR degrading compound, ASC-J9, or AR-small interference RNA, we also examined the therapeutic potentials of targeting AR in HCC.

RESULTS

We found AR expression was increased in human HCC compared with normal livers. We also found mice lacking hepatic AR developed later and less HCC than their wild-type littermates with comparable serum testosterone in both male and female mice. Addition of functional AR in human HCC cells also resulted in the promotion of cell growth in the absence or presence of 5alpha-dihydrotestosterone. Mechanistic dissection suggests that AR may promote hepatocarcinogenesis via increased cellular oxidative stress and DNA damage, as well as suppression of p53-mediated DNA damage sensing/repairing system and cell apoptosis. Targeting AR directly via either AR-small interference RNA or ASC-J9 resulted in suppression of HCC in both ex vivo cell lines and in vivo mice models.

CONCLUSIONS

Our data point to AR, but not androgens, as a potential new and better therapeutic target for the battle of HCC.

Joint effects of inflammation and androgen metabolism on prostate cancer severity

Multiple pathways of prostate carcinogenesis have been proposed, including those involving androgen metabolism and inflammation. These pathways are not independent, and may act together in prostate cancer etiology: androgens promote both inflammatory processes and serve as mitogens in prostate tumor growth. To explore the possible joint effects of these pathways in prostate cancer severity, we studied 1,090 Caucasian prostate cancer cases to evaluate whether tumor severity is influenced by a history of benign prostatic hyperplasia (BPH) interacting with genotypes involved in inflammation or androgen metabolism including MSR1, RNASEL, AR, CYP3A4, CYP3A43, CYP3A5 and SRD5A2. We observed a statistically significant interaction between a number of genotypes and BPH. After considering the potential for false positive associations, the only remaining significant associations involved CYP3A43 P340A genotypes and history of BPH on both Gleason grade (interaction p-value = 0.026) and tumor stage (interaction p-value = 0.017). These results suggest that androgen metabolism may act in concert with inflammatory phenotypes such as BPH in determining prostate cancer severity.