Aberrant Androgen Receptor Expression Research Articles

Depletion of high-mobility group box 2 causes seminiferous tubule atrophy via aberrant expression of androgen and estrogen receptors in mouse testis†.

High-mobility group box 2, a chromatin-associated protein that interacts with deoxyribonucleic acid, is implicated in multiple biological processes, including gene transcription, replication, and repair. High-mobility group box 2 is expressed in several tissues, including the testis; however, its functional role is largely unknown. Here, we elucidated the role of high-mobility group box 2 in spermatogenesis. Paraffin-embedded testicular tissues were obtained from 8-week-old and 1-year-old wild-type and knock-out mice. Testis weight and number of seminiferous tubules were decreased, whereas atrophic tubules were increased in high-mobility group box 2-depleted mice. Immunohistochemistry revealed that atrophic tubules contained Sertoli cells, but not germ cells. Moreover, decreased cell proliferation and increased apoptosis were demonstrated in high-mobility group box 2-depleted mouse testis. To elucidate the cause of tubule atrophy, we examined the expression of androgen and estrogen receptors, and the results indicated aberrant expression of androgen receptor and estrogen receptor alpha in Sertoli and Leydig cells. Southwestern histochemistry detected decreased estrogen response element-binding sites in high-mobility group box 2-depleted mouse testis. High-mobility group box 1, which has highly similar structure and function as high-mobility group box 2, was examined by immunohistochemistry and western blotting, which indicated increased expression in testis. These findings indicate a compensatory increase in high-mobility group box 1 expression in high-mobility group box 2 knock-out mouse testis. In summary, depletion of high-mobility group box 2 induced aberrant expression of androgen receptor and estrogen receptor alpha, leading to decreased germ cell proliferation and increased apoptosis which resulted in focal seminiferous tubule atrophy.

Gene amplification of YB-1 in castration-resistant prostate cancer in association with aberrant androgen receptor expression.

Although Y‐box binding protein‐1 (YB‐1) is known to be overexpressed in prostate cancer, especially castration‐resistant prostate cancer (CRPC), the mechanism of its overexpression remains unclear. We aimed to elucidate the mechanism of YB‐1 overexpression in CRPC. Gene amplification in CRPC cells and tissues was examined by public database analysis, and digital PCR. The significance of YB‐1 amplification for the YB‐1/androgen receptor (AR) axis and prognosis was examined by public database analysis and immunohistochemistry. YB‐1 amplification was mainly observed in CRPC tissues by public database analysis and confirmed in CRPC cells and tissues by digital PCR. Expression of YB‐1 was increased in CRPC tissues compared with treatment‐naïve tissues. Furthermore, YB‐1 and phosphorylated YB‐1 levels were associated with AR and AR V7 expression levels. Finally, YB‐1 amplification was associated with poor outcomes in CRPC. Taken together, the present findings suggest that YB‐1 amplification contributes to progression to CRPC through regulation of AR and AR V7 expressions, and that YB‐1 is a promising therapeutic target in CRPC.

Androgen receptor gene mutations in 258 Han Chinese patients with polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) affects 8-13% of reproductive-age females worldwide and mutations or aberrant expression of androgen receptor (AR) may cause the onset of this disease. In the present study, 258 samples from Han Chinese patients with PCOS were analyzed for the presence of AR mutations via sequencing of all coding exons of the AR gene. A total of five heterozygous missense mutations, namely p.V3M, p.Q72R, p.S158L, p.S176R and p.G396R, were identified in five of the patients. Among these, p.S158L was a novel mutation that, to the best of our knowledge, has not been reported previously. Although the remaining four mutations have been reported previously, they existed at low frequencies or were absent in the control subjects and in the Exome Aggregation Consortium database. The results of evolutionary conservation and in silico analysis revealed that the p.V3M, p.S158L and p.S176R mutations were pathogenic, whereas the p.Q72R and p.G396R mutations were benign. Compared with the patients with PCOS without AR mutations or with benign AR mutations, markedly lower estrogen levels on the day of human chorionic gonadotropin injection were observed in the three patients with PCOS with potentially pathogenic mutations. In addition, patients with PCOS with pathogenic mutations had lower numbers of oocytes; however, the difference was not statistically significant. Of note, these observations should be interpreted with caution due to the relatively small sample size in the present study. Therefore, a larger number of samples should be collected to validate the results of the present study in future studies. In summary, the present study identified three potential pathogenic mutations in 258 Han Chinese patients with PCOS and these mutations may have an implication in the pathogenesis of PCOS.

Aberrant Expression of Androgen Receptor Associated with High Cancer Risk and Extrathyroidal Extension in Papillary Thyroid Carcinoma

Male gender is a risk factor for mortality in patients with papillary thyroid carcinoma (PTC). This study investigated the impact of androgen receptor (AR) gene expression on the clinical features and progression of PTC. The levels of AR mRNA and protein in frozen, formalin-fixed, paraffin-embedded tissue samples from PTC and adjacent normal thyroid tissue were assessed by quantitative real-time polymerase chain reaction and immunohistochemical staining, respectively, and the relationships between AR expression and clinical features were analyzed. The thyroid cancer cell lines, BCPAP and TPC-1, were used to evaluate the effects of AR on the regulation of cell migration, and key epithelial–mesenchymal transition (EMT) markers. AR mRNA expression was significantly higher in normal thyroid tissue from men than women. The sex difference in AR mRNA expression diminished during PTC tumorigenesis, as AR mRNA expression levels were lower in PTC than normal thyroid tissues from both men and women. AR mRNA expression was significantly decreased in PTC patients with higher risk and in those with extrathyroidal extension. Overexpression of AR in BCPAP cells decreased cell migration and repressed the EMT process by down-regulating mRNA expression of N-cadherin, Snail1, Snail2, Vimentin, and TWIST1 and up-regulating E-cadherin gene expression. These results suggest that suppression of the androgen–AR axis may lead to aggressive tumor behavior in patients with PTC.

Abstract B038: Dimethylaminoparthenolide-mediated inhibition of NF-κB decreases resistance to ADT by targeting AR variants in lethal prostate cancer

Abstract Background: Inflammation, mediated by NF-κB, is linked to prostate cancer (PCa) progression and is commonly observed in castrate-resistant disease. We have previously shown that low expression of tristetraprolin (TTP), which modulates the NF-κB pathway and inflammation, is prognostic for lethal PCa after surgery. It has been suggested that NF-κB-driven resistance in PCa cells may be mediated by aberrant androgen receptor (AR) activation and AR splice variant production. Reversal of resistance to androgen deprivation therapy (ADT) may therefore be achieved by utilizing NF-κB inhibitors, such as dimethylaminoparthenolide (DMAPT). Materials and Methods: To examine clinical correlations between TTP/NF-κB and AR-V7, gene-expression profiling data and clinical data was obtained from several publicly available PCa cohorts (TCGA, SU2C, Taylor et. al.). Quantitative immunofluorescence for TTP and PTEN was performed on tissue microarrays from a clinical cohort of patients treated by radical prostatectomy with known time to biochemical recurrence (BCR). In vitro, mouse (MYC-CaP) and human (VCaP-CR, LNCaP-95) PCa cell lines were treated with TNF-α (20 ng/mL) to stimulate NF-κB expression, DMAPT (5-10 μM) to inhibit NF-κB and Enzalutamide (10 μM) in various combinations. Cell lines stably expressing the IκBα super repressor (MUT IκBα) were generated for comparison to DMAPT-mediated inhibition of NF-κB. Expression of AR and AR variants was measured by western blot and qPCR. For in vivo experiments, SCID mice bearing VCaP-CR xenograft tumors were treated with surgical castration, DMAPT (100 mg/kg, oral gavage, QD), surgical castration plus DMAPT or water vehicle control (n = 7-8 per group). Xenograft tumors were measured thrice weekly until they reached an ethical endpoint or after 80 days of treatment. Time-to-progression of tumors was assessed by Kaplan-Meier analysis and molecular differences within tumors analyzed by qPCR and immunohistochemistry (IHC). Results: In multiple clinical PCa cohorts, reduced TTP expression correlated with an increased AR-V7 signature. In a cohort of patients with localized PCa, decreased TTP expression reduced time to BCR and co-loss of TTP and PTEN (a known PCa tumor suppressor) further decreased time to BCR. Activation of NF-κB in PCa cell lines resulted in a significant increase in AR variant expression and minor upregulation of AR. Chemical (DMAPT) and genetic (MUT IκBα) inhibition of NF-κB slowed tumor proliferation and decreased AR variant expression. Treatment of PCa cell lines with Enzalutamide resulted in AR variant upregulation, which was blocked by DMAPT. Castration of mice bearing VCaP-CR tumors significantly increased AR and AR-V7 tumor expression. DMAPT treatment reduced NF-κB and AR-V7 expression in xenograft tumors, but did not significantly alter tumor growth compared to vehicle treatment. The combination of castration and DMAPT slowed median time-to-progression of xenograft tumors compared to vehicle-treated tumors (79 and 36 days respectively, p < 0.001). Combination therapy decreased Ki-67 (IHC), AR-V7 and AR (IHC and qPCR) expression in xenograft tumors. Conclusions: Current treatments for PCa mainly target AR; however, despite initial response, these treatments commonly fail. Our data highlight the relationship between NF-κB and AR variant expression in aggressive PCa and support the rationale for clinical use of DMAPT to treat castrate-resistant tumors in combination with AR antagonists. Citation Format: Katherine L Morel, Anis A Hamid, Leigh Ellis, Christopher J Sweeney. Dimethylaminoparthenolide-mediated inhibition of NF-κB decreases resistance to ADT by targeting AR variants in lethal prostate cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B038. doi:10.1158/1535-7163.TARG-19-B038

Delayed endometrial decidualisation in polycystic ovary syndrome; the role of AR-MAGEA11

Polycystic ovary syndrome (PCOS) is a common gynaecological disorder, with a prevalence of up to 12% of women of reproductive age, and is in part characterised by elevated circulating androgens and aberrant expression of androgen receptor (AR) in the endometrium. A high percentage of PCOS patients suffer from infertility, a condition that appears to be linked to mistimed and incomplete decidualisation critically affecting events surrounding embryo implantation. The aim of this study was to examine the involvement of MAGEA11, and the genome-wide role of AR in PCOS. We determined that elevated androgen levels on PCOS cells had an impact on the delayed and incomplete decidual transformation of endometrial cells. The AR co-regulator MAGEA11, a known enhancer of AR function, was constitutively overexpressed throughout the menstrual cycle of PCOS patients, co-localised in the nucleus of PCOS stromal tissue and cells and formed a molecular complex with AR. Genome-wide AR analysis in PCOS stromal cells revealed that AR targets included genes involved in cell death and apoptosis, as well as genes commonly dysregulated in endometrial cancer. Enhanced MAGEA11 and AR-mediated transcriptional regulation may impact on a correct endometrial decidualisation response, subsequently affecting endometrial receptivity in these infertile women.Key messagesMAGEA11 and AR are overexpressed in hyperandrogenic PCOS patients.MAGEA11-AR overexpression in PCOS correlates with delayed decidualisation.AR and MAGEA11 associate in a molecular complex.AR directly regulates a unique set of genes controlling gene differentiation.

Dehydroepiandrosterone in metastatic castration-resistant prostate cancer: Preliminary results from the SU2C-PCF West Coast Dream Team (WCDT).

179 Background: Aberrant androgen receptor (AR) phenotypes (e.g. splice variants, amplification) are strongly correlated with abiraterone (Abi) and enzalutamide (Enz) resistance. Low serum dehydroepiandrosterone (DHEA) is also associated with poor outcomes to AR-targeted therapy. Here, we investigate the relationship between serum DHEA, AR phenotype, and treatment efficacy in the WCDT. Methods: Patients (pts) with progressive mCRPC enrolled to the WCDT from UCSF, OHSU, UCLA, UBC, and UCD were included in this analysis. Serum DHEA was analyzed via high-pressure liquid chromatography and tandem mass spectrometry. Limit of quantitation (LQ) of DHEA was 0.2ng/mL. Full-length AR (AR-FL) and AR-v7 expression, obtained via RNAseq of metastatic tumor biopsies, was expressed as total reads mapped to gene. PSA response (PSAr) was defined as ≥ 50% PSA decline. Results: 35 pts were included in this analysis: 15 had treatment-naïve mCRPC, and 20 had prior AR-targeted therapy (14 Abi, 6 Enz). All pts were docetaxel-naïve. 11 pts had DHEA < LQ; of these, 10 had received prior AR-targeted therapy. 12 pts received subsequent chemotherapy, and 23 received subsequent Abi/Enz (7 Abi, 16 Enz). In pts with DHEA < LQ, 4/5 (80%) chemotherapy-treated pts had PSAr, while 1/6 (17%) Abi/Enz-treated pts had PSAr. In pts with DHEA ≥ LQ, 2/7 (27%) chemotherapy-treated pts had PSAr, while 9/16 (56%) Abi/Enz-treated pts had PSAr. The relationship between DHEA and PSAr was significantly different between the treatment groups (p = 0.0285). DHEA was higher in patients with PSAr to Abi/Enz versus those without PSAr (median, 0.871 versus 0.275ng/mL, p = 0.006). In an analysis of 27 pts with RNAseq data, the AR-v7/AR-FL ratio was significantly higher in those with DHEA < LQ (median ratio 8.91, versus 3.38 in DHEA ≥ LQ, p = 0.032). Conclusions: In this exploratory analysis, there is a significant difference in the relationship between DHEA and PSAr in chemotherapy- versus Abi/Enz-treated patients. DHEA < LQ was also associated with a higher AR-v7/AR-FL ratio, a potential avenue for further exploration of tumor biology. These results support a larger study to evaluate DHEA as a potential biomarker in mCRPC. Clinical trial information: NCT02432001.

Research Resource: Androgen Receptor Activity Is Regulated Through the Mobilization of Cell Surface Receptor Networks.

The aberrant expression of androgen receptor (AR)-dependent transcriptional programs is a defining pathology of the development and progression of prostate cancers. Transcriptional cofactors that bind AR are critical determinants of prostate tumorigenesis. To gain a deeper understanding of the proteins linked to AR-dependent gene transcription, we performed a DNA-affinity chromatography-based proteomic screen designed to identify proteins involved in AR-mediated gene transcription in prostate tumor cells. Functional experiments validated the coregulator roles of known AR-binding proteins in AR-mediated transcription in prostate tumor cells. More importantly, novel coregulatory functions were detected in components of well-established cell surface receptor-dependent signal transduction pathways. Further experimentation demonstrated that components of the TNF, TGF-β, IL receptor, and epidermal growth factor signaling pathways modulated AR-dependent gene transcription and androgen-dependent proliferation in prostate tumor cells. Collectively, our proteomic dataset demonstrates that the cell surface receptor- and AR-dependent pathways are highly integrated, and provides a molecular framework for understanding how disparate signal-transduction pathways can influence AR-dependent transcriptional programs linked to the development and progression of human prostate cancers.

Androgen receptor as a driver of therapeutic resistance in advanced prostate cancer.

The role of the androgen receptor (AR) signaling axis in the progression of prostate cancer is a cornerstone to our understanding of the molecular mechanisms causing castration-resistant prostate cancer (CRPC). Resistance of advanced prostate cancer to available treatment options makes it a clinical challenge that results in approximately 30,000 deaths of American men every year. Since the historic discovery by Dr. Huggins more than 70 years ago, androgen deprivation therapy (ADT) has been the principal treatment for advanced prostate cancer. Initially, ADT induces apoptosis of androgen-dependent prostate cancer epithelial cells and regression of androgen-dependent tumors. However, the majority of patients with advanced prostate cancer progress and become refractory to ADT due to emergence of androgen-independent prostate cancer cells driven by aberrant AR activation. Microtubule-targeting agents such as taxanes, docetaxel and paclitaxel, have enjoyed success in the treatment of metastatic prostate cancer; although new, recently designed mitosis-specific agents, such as the polo-kinase and kinesin-inhibitors, have yielded clinically disappointing results. Docetaxel, as a first-line chemotherapy, improves prostate cancer patient survival by months, but tumor resistance to these therapeutic agents inevitably develops. On a molecular level, progression to CRPC is characterized by aberrant AR expression, de novo intraprostatic androgen production, and cross talk with other oncogenic pathways. Emerging evidence suggests that reactivation of epithelial-mesenchymal-transition (EMT) processes may facilitate the development of not only prostate cancer but also prostate cancer metastases. EMT is characterized by gain of mesenchymal characteristics and invasiveness accompanied by loss of cell polarity, with an increasing number of studies focusing on the direct involvement of androgen-AR signaling axis in EMT, tumor progression, and therapeutic resistance. In this article, we discuss the current knowledge of mechanisms via which the AR signaling drives therapeutic resistance in prostate cancer metastatic progression and the novel therapeutic interventions targeting AR in CRPC.

Constitutively-active androgen receptor variants function independently of the HSP90 chaperone but do not confer resistance to HSP90 inhibitors

The development of lethal, castration resistant prostate cancer is associated with adaptive changes to the androgen receptor (AR), including the emergence of mutant receptors and truncated, constitutively active AR variants. AR relies on the molecular chaperone HSP90 for its function in both normal and malignant prostate cells, but the requirement for HSP90 in environments with aberrant AR expression is largely unknown. Here, we investigated the efficacy of three HSP90 inhibitors, 17-AAG, HSP990 and AUY922, against clinically-relevant AR missense mutants and truncated variants. HSP90 inhibition effectively suppressed the signaling of wild-type AR and all AR missense mutants tested. By contrast, two truncated AR variants, AR-V7 and ARv567es, exhibited marked resistance to HSP90 inhibitors. Supporting this observation, nuclear localization of the truncated AR variants was not affected by HSP90 inhibition and AR variant:HSP90 complexes could not be detected in prostate cancer cells. Interestingly, HSP90 inhibition resulted in accumulation of AR-V7 and ARv567es in both cell lines and human tumor explants. Despite the apparent independence of AR variants from HSP90 and their treatment-associated induction, the growth of cell lines with endogenous or enforced expression of AR-V7 or ARv567es remained highly sensitive to AUY922. This study demonstrates that functional AR variant signaling does not confer resistance to HSP90 inhibition, yields insight into the interaction between AR and HSP90 and provides further impetus for the clinical application of HSP90 inhibitors in advanced prostate cancer.