Androgen-mediated Androgen Receptor Research Articles

Synthesis of dihydrotestosterone derivatives modified in the A-ring with (hetero)arylidene, pyrazolo[1,5-a]pyrimidine and triazolo[1,5-a]pyrimidine moieties and their targeting of the androgen receptor in prostate cancer

One of the main directions of steroid research is the preparation of modified derivatives in which, in addition to changes in physicochemical properties, receptor binding is significantly altered, thus a bioactivity different from that of the parent compound predominates. In the frame of this work, 2-arylidene derivatives were first synthesized by regioselective modification of the A-ring of natural sex hormone, 5α-dihydrotestosterone (DHT). After Claisen-Schmidt condensations of DHT with (hetero)aromatic aldehydes in alkaline EtOH, heterocyclizations of the α,β-enones were performed with 3-amino-1,2,4-triazole, 3-aminopyrazole and 3-amino-5-methylpyrazole in the presence of t-BuOK in DMF to afford 7′-epimeric mixtures of A-ring-fused azolo-dihydropyrimidines, respectively. Depending on the electronic demand of the substituents of the arylidene moiety, spontaneous or 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ)-induced oxidation of the heteroring led to triazolo[1,5-a]pyrimidines and pyrazolo[1,5-a]pyrimidines in good yields, while, using the Jones reagent as a strong oxidant, 17-oxidation also occurred. The crystal structures of an arylidene and a triazolopyrimidine product have been determined by single crystal X-ray diffraction and both were found to crystallize in the monoclinic crystal system at P21 space group. Most derivatives were found to diminish the transcriptional activity of androgen receptor (AR) in reporter cell line. The candidate compound (17β-hydroxy-2-(4-chloro)benzylidene-5α-androstan-3-one, 2f) showed to suppress androgen-mediated AR transactivation in a dose-dependent manner. We confirmed the cellular interaction of 2f with AR, described the binding in AR-binding cavity by the flexible docking and showed the ability of the compound to suppress the expression of AR-regulated genes in two prostate cancer cell lines.

Inhibition of autophagy enhances the anticancer effect of enzalutamide on bladder cancer

BackgroundEmerging preclinical evidence suggests a critical role for androgen-mediated androgen receptor (AR) signaling in bladder cancer progression. However, researchers have not determined whether autophagy modulates the efficacy of an enzalutamide (ENZ) treatment in subjects with advanced bladder cancer. In this study, we investigated the synergistic effect of ENZ and autophagy inhibitors on bladder cancer. MethodsENZ was used as an anti-AR drug, and chloroquine (CQ), 3-methyladenine (3-MA), and bafilomycin A1 (BAF) were used as autophagy inhibitors. J82, T24, and UMUC3 cell lines were used as models of bladder cancer. A bifluorescence autophagy system with the mRFP-GFP-LC3 plasmid was used to evaluate autophagy flux. Protein and mRNA levels were detected using Western blotting and qPCR, respectively. A Cell Counting Kit-8 (CCK-8) assay, colony assay, and flow cytometry analysis were used to evaluate cell proliferation and apoptosis. Four-week-old BALB/c athymic nude mice were used in the in vivo assay. ResultsBased on the results obtained using the bifluorescence autophagy system, ENZ (10–20 μM) significantly facilitated the accumulation of autophagosomes and autolysosomes in the cytoplasm of J82 and T24 cells. Additionally, ENZ significantly increased the expression of autophagy-related genes (AMP-dependent protein kinase (AMPK), autophagy-related gene 5 (ATG5), microtubule-associated protein light chain 3B (LC3B), and UNC-51-like kinase 1 (ULK1)) and proteins (microtubule-associated protein 1 light chain 3-II/I (LC3-II/I), ATG5, and phosphorylated AMP-dependent protein kinase α (p-AMPKα)). The administration of ENZ monotherapy (10–20 μM) to J82 and T24 cells failed to alter proliferation and apoptosis. Concurrent treatment with ENZ and autophagy inhibitors distinctly triggered apoptosis and inhibited proliferation. Genetic inhibition of autophagy by specifically blocking ATG5 with siRNA also increased ENZ-induced apoptosis in J82 and T24 cells. In vivo, concurrent treatment with ENZ (25 mg/kg/day) and CQ (10 mg/kg/day) improved the therapeutic sensitivity by decreasing tumor growth and apoptosis. Additionally, overexpression of AR suppressed ENZ-induced autophagy-related genes (LC3-II/I, ATG5, and p-AMPKα) in T24 cells, and CQ exerted synergistic effects with ENZ to suppressed AR-responsive genes expression (KLK2 and KLK3) in bladder cancer. In UMUC3 cells, ENZ monotherapy directly induced anticancer effects, and concurrent treatment with ENZ and CQ also had a synergistic effect on proliferation and apoptosis. ConclusionsAutophagy may be a potential mechanism underlying ENZ-resistant bladder cancer. Blockade of autophagy significantly increased ENZ-induced apoptosis in bladder cancer. Thus, concurrent treatment with autophagy inhibitors and ENZ may be a novel therapeutic strategy for bladder cancer.

The interaction between androgen receptor and semenogelin I: a synthetic LxxLL peptide antagonist inhibits the growth of prostate cancer cells

Background:We previously demonstrated that a seminal plasma protein, semenogelin I (SgI), functioned as an androgen receptor (AR) coactivator. Meanwhile, several short sequence motifs in AR coregulators, such as LxxLL (L=leucine), have been shown to mediate specific interactions with AR.Methods:We investigated the role of the LxxLL motif within SgI in the interactions with AR and cell growth in prostate cancer lines in vitro.Results:A full-length SgI with mutations in the motif (i.e., LxxAA; A=alanine) failed to significantly increase cell proliferation/migration as well as androgen-mediated AR transcription. Co-immunoprecipitation showed no physical interactions between AR and the mutant SgI. In addition, transfection of an 18-amino acid peptide of SgI containing LxxLL, but not LxxAA, resulted in considerable reduction in cell growth and prostate-specific antigen expression in LNCaP and C4-2 lines.Conclusions:The LxxLL motif of SgI could be a novel therapeutic target for both androgen-sensitive and castration-resistant prostate cancers.

Androgen Receptor Signaling in Bladder Cancer.

Emerging preclinical findings have indicated that steroid hormone receptor signaling plays an important role in bladder cancer outgrowth. In particular, androgen-mediated androgen receptor signals have been shown to correlate with the promotion of tumor development and progression, which may clearly explain some sex-specific differences in bladder cancer. This review summarizes and discusses the available data, suggesting the involvement of androgens and/or the androgen receptor pathways in urothelial carcinogenesis as well as tumor growth. While the precise mechanisms of the functions of the androgen receptor in urothelial cells remain far from being fully understood, current evidence may offer chemopreventive or therapeutic options, using androgen deprivation therapy, in patients with bladder cancer.

The activation of OR51E1 causes growth suppression of human prostate cancer cells.

The development of prostate cancer (PCa) is regulated by the androgen-dependent activity of the androgen receptor (AR). Androgen-deprivation therapy (ADT) is therefore the gold standard treatment to suppress malignant progression of PCa. Nevertheless, due to the development of castration resistance, recurrence of disease after initial response to ADT is a major obstacle to successful treatment. As G-protein coupled receptors play a fundamental role in PCa physiology, they might represent promising alternative or combinatorial targets for advanced diseases. Here, we verified gene expression of the olfactory receptors (ORs) OR51E1 [prostate-specific G-protein coupled receptor 2 (PSGR2)] and OR51E2 (PSGR) in human PCa tissue by RNA-Seq analysis and RT-PCR and elucidated the subcellular localization of both receptor proteins in human prostate tissue. The OR51E1 agonist nonanoic acid (NA) leads to the phosphorylation of various protein kinases and growth suppression of the PCa cell line LNCaP. Furthermore, treatment with NA causes reduction of androgen-mediated AR target gene expression. Interestingly, NA induces cellular senescence, which coincides with reduced E2F1 mRNA levels. In contrast, treatment with the structurally related compound 1-nonanol or the OR2AG1 agonist amyl butyrate, neither of which activates OR51E1, did not lead to reduced cell growth or an induction of cellular senescence. However, decanoic acid, another OR51E1 agonist, also induces cellular senescence. Thus, our results suggest the involvement of OR51E1 in growth processes of PCa cells and its impact on AR-mediated signaling. These findings provide novel evidences to support the functional importance of ORs in PCa pathogenesis.

Enzalutamide inhibits androgen receptor–positive bladder cancer cell growth

PurposeEmerging preclinical evidence suggests that androgen-mediated androgen receptor (AR) signals promote bladder cancer progression. However, little is known about the efficacy of an AR signaling inhibitor, enzalutamide, in the growth of bladder cancer cells. In this study, we compared the effects of enzalutamide and 2 other classic antiandrogens, flutamide and bicalutamide, on androgen-induced bladder cancer cell proliferation, migration, and invasion as well as tumor growth in vivo. MethodsThiazolyl blue cell viability assay, flow cytometry, scratch wound-healing assay, transwell invasion assay, real-time polymerase chain reaction, and reporter gene assay were performed in AR-positive (e.g., UMUC3, TCCSUP, and 647V-AR) and AR-negative (e.g., UMUC3-AR-short hairpin RNA [shRNA], TCCSUP-AR-shRNA, 647V) bladder cancer lines treated with dihydrotestosterone and each AR antagonist. We also used a mouse xenograft model for bladder cancer. ResultsDihydrotestosterone increased bladder cancer cell proliferation, migration, and invasion indicating that endogenous or exogenous AR was functional. Enzalutamide, hydroxyflutamide, and bicalutamide showed similar inhibitory effects, without significant agonist activity, on androgen-mediated cell viability/apoptosis, cell migration, and cell invasion in AR-positive lines. No significant effects of dihydrotestosterone as well as AR antagonists on the growth of AR-negative cells were seen. Correspondingly, in UMUC3 cells, these AR antagonists down-regulated androgen-induced expression of AR, matrix metalloproteinase-2, and interleukin-6. Androgen-enhanced AR-mediated transcriptional activity was also blocked by each AR antagonist exhibiting insignificant agonist activity. In UMUC3 xenograft-bearing mice, oral gavage treatment with each antiandrogen retarded tumor growth, and only enzalutamide demonstrated a statistically significant suppression compared with mock treatment. ConclusionsOur current data support recent observations indicating the involvement of the AR pathway in bladder cancer growth and further suggest that AR antagonists, including enzalutamide, are of therapeutic benefit in AR-positive bladder cancer.

Androgen receptor activity modulates responses to cisplatin treatment in bladder cancer.

Cisplatin (CDDP)-based combination chemotherapy remains the mainstream treatment for advanced bladder cancer. However, its efficacy is often limited due to the development of resistance for which underlying mechanisms are poorly understood. Meanwhile, emerging evidence has indicated the involvement of androgen-mediated androgen receptor (AR) signals in bladder cancer progression. In this study, we aimed to investigate whether AR signals have an impact on sensitivity to CDDP in bladder cancer cells. UMUC3-control-short hairpin RNA (shRNA) cells with endogenous AR and AR-negative 647V/5637 cells stably expressing AR were significantly more resistant to CDDP treatment at its pharmacological concentrations, compared with UMUC3-AR-shRNA and 647V-vector/5637-vector control cells, respectively. A synthetic androgen R1881 significantly reduced CDDP sensitivity in UMUC3, 647V-AR, or 5637-AR cells, and the addition of an anti-androgen hydroxyflutamide inhibited the effect of R1881. In these AR-positive cells, R1881 treatment also induced the expression levels of NF-κB, which is known to involve CDDP resistance, and its phosphorylated form, as well as nuclear translocation of NF-κB. In CDDP-resistant bladder cancer sublines established following long-term culture with CDDP, the expression levels of AR as well as NF-κB and phospho-NF-κB were considerably elevated, compared with respective control sublines. In bladder cancer specimens, there was a strong trend to correlate between AR positivity and chemoresistance. These results suggest that AR activation correlates with CDDP resistance presumably via modulating NF-κB activity in bladder cancer cells. Targeting AR during chemotherapy may thus be a useful strategy to overcome CDDP resistance in patients with AR-positive bladder cancer.

MP83-20 ENZALUTAMIDE AS AN ANDROGEN RECEPTOR INHIBITOR PREVENTS UROTHELIAL TUMORIGENESIS

You have accessJournal of UrologyBladder Cancer: Basic Research & Pathophysiology IV1 Apr 2016MP83-20 ENZALUTAMIDE AS AN ANDROGEN RECEPTOR INHIBITOR PREVENTS UROTHELIAL TUMORIGENESIS Takashi Kawahara, Hiroki Ide, Eiji Kashiwagi, Yi Li, Satoshi Inoue, Yichun Zheng, and Hiroshi Miyamoto Takashi KawaharaTakashi Kawahara More articles by this author , Hiroki IdeHiroki Ide More articles by this author , Eiji KashiwagiEiji Kashiwagi More articles by this author , Yi LiYi Li More articles by this author , Satoshi InoueSatoshi Inoue More articles by this author , Yichun ZhengYichun Zheng More articles by this author , and Hiroshi MiyamotoHiroshi Miyamoto More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2016.02.2202AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Emerging preclinical evidence suggests the critical role of androgen-mediated androgen receptor (AR) signals in the development of bladder cancer. However, little is known about the efficacy of enzalutamide, an AR signaling inhibitor that not only blocks androgen binding to AR but also prevents AR nuclear translocation, DNA binding, and coactivator recruitment, in urothelial tumorigenesis. In the current study, we aimed to assess the effects of enzalutamide as well as other anti-androgens, such as flutamide and bicalutamide, on androgen-induced neoplastic transformation of urothelial cells. METHODS An immortalized normal urothelial cell line SVHUC stably expressing wild-type AR (SVHUC-AR) was exposed to a chemical carcinogen 3-methylcholanthrene (MCA) 3 times, to induce neoplastic transformation, and subsequently cultured for 6 weeks in the presence or absence of anti-androgens. Tumorigenesis was then monitored, using plate and soft agar colony formation assays as well as mouse xenograft models. In the SVHUC-AR cells with the carcinogen challenge, quantitative real-time polymerase chain reaction analysis was also performed to determine the expression levels of tumor suppressor genes and oncogenes. RESULTS In SVHUC-AR cells, each anti-androgen was found to inhibit AR-mediated transcriptional activity. In vitro transformation showed that treatment with each anti-androgen during the process of neoplastic transformation similarly reduced the efficiency of colony formation in vitro. Compared with mock treatment, culture with enzalutamide (P = 0.028), hydroxyflutamide (P = 0.033), or bicalutamide (P = 0.038) also resulted in prevention/retardation of tumor formation in male NOD-SCID mice. Additionally, anti-androgens up-regulated the expression of several molecules that play a protective role in bladder tumorigenesis, including p53, p21, p27, and PTEN, and down-regulated that of several oncogenic genes, such as c-myc, cyclin D1, cyclin D3, and cyclin E, in MCA-exposed SVHUC-AR cells. However, significant effects of anti-androgens on the expression of these genes were not observed in SVHUC-AR cells without the carcinogen challenge. CONCLUSIONS Enzalutamide, flutamide, and bicalutamide similarly prevent neoplastic transformation of urothelial cells. These findings offer a potential chemopreventive approach for urothelial tumors using AR antagonists. © 2016FiguresReferencesRelatedDetails Volume 195Issue 4SApril 2016Page: e1088-e1089 Advertisement Copyright & Permissions© 2016MetricsAuthor Information Takashi Kawahara More articles by this author Hiroki Ide More articles by this author Eiji Kashiwagi More articles by this author Yi Li More articles by this author Satoshi Inoue More articles by this author Yichun Zheng More articles by this author Hiroshi Miyamoto More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Compound A Inhibits Bladder Cancer Growth Predominantly via Glucocorticoid Receptor Transrepression.

Recent evidence indicates that glucocorticoids (GCs) suppress bladder cancer cell invasion through the GC receptor (GR) pathway, whereas androgen-mediated androgen receptor (AR) signals induce bladder tumor progression. In this study, we assessed the effects of 2-(4-acetoxyphenyl)-2-chloro-N-methyl-ethylammonium chloride (compound A [CpdA]), which was shown to function as not only a GR modulator but also an AR antagonist, on the growth of bladder cancer. In GR/AR-positive cells, CpdA strongly inhibited cell proliferation and colony formation as well as increased G1 phase-arrested cell population and apoptosis. Specifically, CpdA at 1μM decreased cell viability of TCCSUP/UMUC3-control-short hairpin RNA (shRNA), TCCSUP/UMUC3-GR-shRNA, and TCCSUP/UMUC3-AR-shRNA by 50%/67%, 25%/26%, and 38%/58%, respectively. CpdA also inhibited cell migration and invasion of GR/AR-positive (up to 61% decrease) and GR-positive/AR-silencing (up to 51% decrease) lines and, less strongly, those of GR-silencing/AR-positive lines (up to 35% decrease). Additionally, in UMUC3-control xenograft-bearing male mice, CpdA more strongly suppressed tumor growth than dexamethasone or hydroxyflutamide. In reporter gene assays, CpdA failed to induce GR transactivation, whereas it antagonized dihydrotestosterone-enhanced AR transactivation. In contrast, CpdA reduced nuclear factor (NF)-κB and activator protein 1 transcriptional activities, indicating induction of GR-mediated transrepression. Correspondingly, the expression of NF-κB-related molecules, matrix metalloproteinase-2, matrix metalloproteinase-9, interleukin-6, and vascular endothelial growth factor, was significantly down-regulated by CpdA in control lines but not in GR-silencing cells. Moreover, coimmunoprecipitation showed that CpdA promoted the interactions between GR and NF-κB. Thus, CpdA likely inhibits bladder cancer growth predominantly via inducing GR transrepression and at least partially mediated through the AR pathway, suggesting its effects more beneficial than GCs/pure GR ligands or AR antagonists.

MP49-16 ENZALUTAMIDE INHIBITS ANDROGEN RECEPTOR-POSITIVE BLADDER CANCER CELL GROWTH

You have accessJournal of UrologyBladder Cancer: Basic Research III1 Apr 2015MP49-16 ENZALUTAMIDE INHIBITS ANDROGEN RECEPTOR-POSITIVE BLADDER CANCER CELL GROWTH Takashi Kawahara, Hiroki Ide, Eiji Kashiwagi, Leonardo Reis, Yichun Zheng, and Hiroshi Miyamoto Takashi KawaharaTakashi Kawahara More articles by this author , Hiroki IdeHiroki Ide More articles by this author , Eiji KashiwagiEiji Kashiwagi More articles by this author , Leonardo ReisLeonardo Reis More articles by this author , Yichun ZhengYichun Zheng More articles by this author , and Hiroshi MiyamotoHiroshi Miyamoto More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2015.02.2811AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Emerging preclinical evidence suggests the involvement of androgen-mediated androgen receptor (AR) signals in bladder cancer progression. However, little is known about the efficacy of enzalutamide, an AR signaling inhibitor that not only blocks androgen binding to AR but also prevents AR nuclear translocation, DNA binding, and coactivator recruitment, in the growth of bladder cancer cells. In this study, we compared the effects of enzalutamide and 2 other anti-androgens, flutamide and bicalutamide, on androgen-induced bladder cancer cell proliferation, migration, and invasion. METHODS MTT assay, colony formation assay, scratch wound healing assay, transwell invasion assay, real-time polymerase chain reaction, and reporter gene assay were performed in AR-positive (e.g. UMUC3, TCCSUP, 5637-AR, 647V-AR) and AR-negative (e.g. UMUC3-AR-shRNA, TCCSUP-AR-shRNA, 5637, 647V) bladder cancer lines treated with dihydrotestosterone and/or each anti-androgen. We also used a mouse xenograft model for bladder cancer. RESULTS Dihydrotestosterone increased cell viability, colony formation, cell migration, and cell invasion, indicating that endogenous or exogenous AR was functional. Enzalutamide, hydroxyflutamide, and bicalutamide showed similar inhibitory effects, without significant agonist activity, on androgen-induced cell proliferation/migration/invasion in AR-positive lines. No significant effects of dihydrotestosterone as well as anti-androgens on the growth were seen in AR-negative cells. Correspondingly, in UMUC3 cells, these anti-androgens down-regulated androgen-induced expression of MMP-2 and IL-6. Androgen-enhanced AR-mediated transcriptional activity was also blocked by each anti-androgen exhibiting marginal agonist activity. In UMUC3 xenograft-bearing mice, oral gavage treatment with each anti-androgen retarded tumor growth, and enzalutamide showed more significant suppressive effects, compared with flutamide or bicalutamide treatment. CONCLUSIONS These findings support recent findings indicating that androgens promote bladder cancer progression via the AR pathway and further suggest that anti-androgens, including enzalutamide, are of therapeutic benefit in AR-positive bladder cancer. © 2015 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 193Issue 4SApril 2015Page: e608-e609 Advertisement Copyright & Permissions© 2015 by American Urological Association Education and Research, Inc.MetricsAuthor Information Takashi Kawahara More articles by this author Hiroki Ide More articles by this author Eiji Kashiwagi More articles by this author Leonardo Reis More articles by this author Yichun Zheng More articles by this author Hiroshi Miyamoto More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

The Role of the Androgen Receptor in the Development and Progression of Bladder Cancer

Men are at a higher risk of developing bladder cancer than women. Since bladder cancer cell lines and tissues were found to express the androgen receptor, efforts have been made to inspect whether androgen-mediated androgen receptor signals are implicated in bladder carcinogenesis as well as cancer progression. Mounting evidence supports the view that bladder cancer is a member of the endocrine-related tumors and may clearly explain the gender-specific difference in the incidence. However, the underlying mechanisms of how androgen receptor signals regulate bladder cancer growth are still far from fully characterized. Moreover, it remains controversial whether the androgen receptor pathway always plays a dominant role in bladder cancer progression. In this review, we summarize the available data on the involvement of androgen receptor signaling in bladder cancer. In particular, current evidence demonstrating the stimulatory effects of androgens on tumor progression or, more convincingly, tumorigenesis via the androgen receptor pathway may offer great potential for androgen deprivation as a therapeutic or chemopreventive option in patients with bladder cancer.

Combination Therapy of Antiandrogen and XIAP Inhibitor for Treating Advanced Prostate Cancer

Overexpression of the androgen receptor (AR) and anti-apoptotic genes including X-linked inhibitor of apoptosis protein (XIAP) provide tumors with a proliferative advantage. Therefore, our objective was to determine whether novel antiandrogen (CBDIV17) and XIAP inhibitor based combination therapy can treat advanced prostate cancer. CBDIV17 and embelin-6g were synthesized and their effect on cell proliferation, apoptosis, cell cycle and AR and XIAP gene silencing determined. CBDIV17 was more potent than bicalutamide and inhibited proliferation of C4-2 and LNCaP cells, IC(50) for CBDIV17 was ≈ 12 μM and ≈ 21 μM in LNCaP and C4-2 cells, respectively, whereas bicalutamide had IC(50) of ≈ 46 μM in LNCaP cells and minimal effect in C4-2 cells. CBDIV17 induced apoptosis more effectively compared to bicalutamide and significantly inhibited DNA replication. Combination of CBDIV17 and embelin resulted in supra-additive antiproliferative and apoptotic effects. Embelin downregulated AR expression and decreased androgen-mediated AR phosphorylation at Ser(81). These hydrophobic drugs were solubilized using micelles prepared with polyethylene glycol-b-poly (carbonate-co-lactide) (PEG-b-p(CB-co-LA)) copolymer. Combination therapy inhibited prostate tumor growth more effectively compared to control or monotherapy in vivo. Our results demonstrated that CBDIV17 in combination with embelin can potentially treat advanced prostate cancer.

Nuclear Hormone Receptor Signals as New Therapeutic Targets for Urothelial Carcinoma

Unlike prostate and breast cancers, urothelial carcinoma of the urinary bladder is not yet considered as an endocrine-related neoplasm, and hormonal therapy for bladder cancer remains experimental. Nonetheless, there is increasing evidence indicating that nuclear hormone receptor signals are implicated in the development and progression of bladder cancer. Androgen-mediated androgen receptor (AR) signals have been convincingly shown to induce bladder tumorigenesis. Androgens also promote the growth of AR-positive bladder cancer cells, although it is controversial whether AR plays a dominant role in bladder cancer progression. Both stimulatory and inhibitory functions of estrogen receptor signals in bladder cancer have been reported. Various studies have also demonstrated the involvement of other nuclear receptors, including progesterone receptor, glucocorticoid receptor, vitamin D receptor, and retinoid receptors, as well as some orphan receptors, in bladder cancer. This review summarizes and discusses available data suggesting the modulation of bladder carcinogenesis and cancer progression via nuclear hormone receptor signaling pathways. These pathways have the potential to be an extremely important area of bladder cancer research, leading to the development of effective chemopreventive/therapeutic approaches, using hormonal manipulation. Considerable uncertainty remains regarding the selection of patients who are likely to benefit from hormonal therapy and optimal options for the treatment.

Androgen receptor signals regulate UDP‐glucuronosyltransferases in the urinary bladder: A potential mechanism of androgen‐induced bladder carcinogenesis

UDP-glucuronosyltransferases (UGTs), major phase II drug metabolism enzymes, play an important role in urinary bladder cancer initiation by detoxifying carcinogens. We aimed to determine if androgens regulate UGT expression via the androgen receptor (AR) pathway in the bladder. Real-time reverse transcription-polymerase chain reaction and Western blot analyses were used to assess UGT1A levels in the normal urothelium SVHUC cell line stably expressed with AR and in bladder tissues from AR knockout (ARKO) and castrated male mice. Immunohistochemistry was also performed in radical cystectomy specimens. Dihydrotestosterone (DHT) treatment in SVHUC-AR reduced mRNA expression of all the UGT1A subtypes (19-75% decrease), and hydroxyflutamide antagonized the DHT effects. In contrast, DHT showed only marginal effects on UGT1A expression in SVHUC-Vector. Of note were higher expression levels of UGT1As in SVHUC-Vector than in SVHUC-AR. In ARKO mice, all the Ugt1a subtypes were up-regulated, compared to wild-type littermates. In wild-type male mice, castration increased the expression of Ugt1a8, Ugt1a9, and Ugt1a10. Additionally, wild-type female mice had higher levels of Ugt1a than wild-type males. Immunohistochemical studies showed strong (3+) UGT1A staining in 11/24 (46%) cancer tissues, which was significantly lower than in corresponding benign tissues [17/18 (94%) cases (P = 0.0009)]. These results suggest that androgen-mediated AR signals promote bladder carcinogenesis by down-regulating the expression of UGTs in the bladder.

Camptothecin disrupts androgen receptor signaling and suppresses prostate cancer cell growth

The androgen receptor (AR) is the main therapeutic target for treatment of metastatic prostate cancers. The present study demonstrates that the topoisomerase I inhibitor camptothecin selectively inhibits androgen-responsive growth of prostate cancer cells. Camptothecin strikingly inhibited mutated and wild-type AR protein expression in LNCaP and PC-3/AR cells. This inhibition coincided with decreased androgen-mediated AR phosphorylation at Ser 81 and reduced androgen-mediated AR transcriptional activity in a dose-dependent manner. Additionally, camptothecin disrupted the association between AR and heat shock protein 90 and impeded binding of the synthetic androgen [ 3H]R1881 to AR in LNCaP cells. Camptothecin also blocked androgen-induced AR nuclear translocation, leading to downregulation of the AR target gene PSA. In addition to decreasing the intracellular and secreted prostate-specific antigen (PSA) levels, camptothecin markedly inhibited androgen-stimulated PSA promoter activity. Collectively, our data reveal that camptothecin not only serves as a traditional genotoxic agent but, by virtue of its ability to target and disrupt AR, may also be a novel candidate for the treatment of prostate cancer.

<b>Crosstalk between the epidermal growth factor receptor and androgen receptor signaling pathways in prostate cancer</b>

Malignant cells are characterized by complex and often overlapping signaling pathways that modulate uncontrolled proliferation, leading to tumor growth and cancer progression. Prostate cancer is characterized by a dependence on androgens for growth initiation, and androgen deprivation is the standard treatment for advanced disease. Invariably, progression to castration-resistant prostate cancer (CRPC) occurs. Effective treatment options are currently limited to cytotoxic chemotherapy. In addition to androgen-mediated androgen receptor (AR) signaling in CRPC, multiple growth factor pathways are active, including the epidermal growth factor (EGF) receptor family of tyrosine kinases. Crosstalk between these two pathways has been studied in prostate cancer cell lines, xenograft tumor models, and in prostate cancer patients. This manuscript will focus on EGFR signaling, AR signaling, EGFR-AR crosstalk, and therapies targeted at these receptor-mediated regulatory pathways in CRPC

Dihydrotestosterone interacts with EGFR/MAPK signalling and modulates EGFR levels in androgen receptor-positive LNCaP prostate cancer cells

Androgen receptor (AR) signalling plays a pivotal role in prostate cancer pathogenesis and progression. However, androgen-mediated AR signalling is yet to be fully understood. EGFR and MAP kinase signalling pathways play predominant roles in AR function. Therefore, we investigated the interaction of EGFR signalling and AR activity in AR-positive LNCaP cells. We found that 5alpha-dihydrotestosterone (DHT) and EGF had a synergistic effect on AR activity as detected by a luciferase reporter system, although EGF alone did not activate AR. Both ERK1/2 and p38 were involved in DHT and DHT/EGF-induced AR activation as detected by specific MEK and p38 inhibitors. Furthermore, 24-h treatment of the cells with DHT resulted in ubiquitination and down-regulation of the EGFR. This effect could be inhibited by the anti-androgen flutamide, suggesting an androgen-dependent mechanism. On the other hand, DHT-treatment strongly increased AR levels in LNCaP cells. These data suggest a complex regulatory loop between activated AR and EGFR. In conclusion, activation of AR by both DHT and EGF/DHT involves the MAP kinase pathway. Long-term activation of AR results in increase of AR levels, which through so far unknown regulatory mechanisms results in ubiquitination and degradation of the EGFR.