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Androgen receptor splice variants

Zachery R Reichert, Maha Hussain
The development of metastatic castration-resistant prostate cancer (mCRPC) signals the terminal disease phase. The preceding hormone-dependent disease setting is effectively managed with androgen deprivation therapy. This foundation of treatment has a high rate of biochemical and clinical response and meaningful clinical benefit but is finite in duration as most cancers will progress to castration resistance. Historically, treatment for mCRPC entailed androgen receptor (AR) inhibitors (nilutamide, flutamide, bicalutamide), nonspecific steroidal biosynthesis inhibitors (ketoconazole, itraconazole), steroids (prednisone, diethylstilbesterol, dexamethasone), or palliative chemotherapy (mitoxantrone, estramustine), but none of these strategies impacted survival...
September 2016: Cancer Journal
Marzia Del Re, Elisa Biasco, Stefania Crucitta, Lisa Derosa, Eleonora Rofi, Cinzia Orlandini, Mario Miccoli, Luca Galli, Alfredo Falcone, Guido W Jenster, Ron H van Schaik, Romano Danesi
BACKGROUND: The androgen receptor splice variant 7 (AR-V7) is associated with resistance to hormonal therapy in castration-resistant prostate cancer (CRPC). Due to limitations of the methods available for AR-V7 analysis, the identification of a reliable detection method may facilitate the use of this biomarker in clinical practice. OBJECTIVE: To confirm AR-V7 as a predictor of resistance to hormonal therapy and develop a new approach to assess AR-V7 by highly sensitive digital droplet polymerase chain reaction (ddPCR) in plasma-derived exosomal RNA...
August 26, 2016: European Urology
Edel McCrea, Tristan M Sissung, Douglas K Price, Cindy H Chau, William D Figg
Significant therapeutic progress has been made in treating prostate cancer in recent years. Drugs such as enzalutamide, abiraterone, and cabazitaxel have expanded the treatment armamentarium, although it is not completely clear which of these drugs are the most-effective option for individual patients. Moreover, such advances have been tempered by the development of therapeutic resistance. The purpose of this review is to summarize the current literature pertaining to the biochemical effects of AR variants and their consequences on prostate cancer therapies at both the molecular level and in clinical treatment...
October 7, 2016: Pharmacological Research: the Official Journal of the Italian Pharmacological Society
Pradeep S Jadhavar, Sreekanth A Ramachandran, Eduardo Riquelme, Ashu Gupta, Kevin P Quinn, Devleena Shivakumar, Soumya Ray, Dnyaneshwar Zende, Anjan K Nayak, Sandeep K Miglani, Balaji D Sathe, Mohd Raja, Olivia Farias, Ivan Alfaro, Sebastián Belmar, Javier Guerrero, Sebastián Bernales, Sarvajit Chakravarty, David T Hung, Jeffrey N Lindquist, Roopa Rai
While enzalutamide and abiraterone are approved for treatment of metastatic castration-resistant prostate cancer (mCRPC), approximately 20-40% of patients have no response to these agents. It has been stipulated that the lack of response and the development of secondary resistance to these drugs may be due to the presence of AR splice variants. HDAC6 has a role in regulating the androgen receptor (AR) by modulating heat shock protein 90 (Hsp90) acetylation, which controls the nuclear localization and activation of the AR in androgen-dependent and independent scenarios...
October 4, 2016: Bioorganic & Medicinal Chemistry Letters
Emily J Faivre, Denise Wilcox, Xiaoyu Lin, Paul Hessler, Maricel Torrent, Wei He, Tamar Uziel, Daniel H Albert, Keith McDaniel, Warren Kati, Yu Shen
: Competitive inhibitors of acetyl-lysine binding to the bromodomains of the BET (bromodomain and extra terminal) family are being developed for the treatment of solid and hematologic malignancies. The function of BET family member BRD4 at enhancers/super-enhancers has been shown to sustain signal-dependent or pathogenic gene expression programs. Here the hypothesis was tested that the transcription factor drivers of castration-resistant prostate cancer (CRPC) clinical progression, including the Androgen Receptor (AR), are critically dependent on BRD4 and thus represent a sensitive solid tumor indication for the BET inhibitor ABBV-075...
October 5, 2016: Molecular Cancer Research: MCR
Subing Cao, Yang Zhan, Yan Dong
Androgen receptor splice variants are alternatively spliced variants of androgen receptor that are C-terminally truncated and lack the canonical ligand-binding domain. Accumulating evidence has indicated a significant role of androgen receptor splice variants in mediating resistance of castration-resistant prostate cancer to current therapies and in predicting therapeutic responses. As such, there is an urgent need to target androgen receptor splicing variants for more effective treatment of castration-resistant prostate cancer...
October 4, 2016: Endocrine-related Cancer
Adam T Szafran, Cliff Stephan, Michael Bolt, Maureen G Mancini, Marco Marcelli, Michael A Mancini
BACKGROUND: AR-V7 is an androgen receptor (AR) splice variant that lacks the ligand-binding domain and is isolated from prostate cancer cell lines. Increased expression of AR-V7 is associated with the transition from hormone-sensitive prostate cancer to more advanced castration-resistant prostate cancer (CRPC). Due to the loss of the ligand-binding domain, AR-V7 is not responsive to traditional AR-targeted therapies, and the mechanisms that regulate AR-V7 are still incompletely understood...
October 4, 2016: Prostate
T Uo, H Dvinge, C C Sprenger, R K Bradley, P S Nelson, S R Plymate
The presence of intact ligand-binding domain (LBD) ensures the strict androgen-dependent regulation of androgen receptor (AR): binding of androgen induces structural reorganization of LBD resulting in release of AR from HSP90, suppression of nuclear export which otherwise dominates over import and nuclear translocation of AR as a transcription factor. Thus, loss or defects of the LBD abolish constraint from un-liganded LBD as exemplified by constitutively active AR variants (AR-Vs), which are associated with emerging resistance mechanism to anti-AR therapy in castration-resistant prostate cancer (mCRPC)...
October 3, 2016: Oncogene
Mary-Ellen Taplin, Rana R McKay, Lillian Werner, Elahe A Mostaghel, Rosina T Lis, Olga Voznesensky, Zhenwei Zhang, Brett Marck, Alvin M Matsumoto, Liran Domachevsky, Katherine A Zukotynski, Manoj K Bhasin, Glenn J Bubley, Bruce Montgomery, Philip W Kantoff, Steven P Balk
PURPOSE: Despite the efficacy of abiraterone, a CYP17A1 inhibitor, in metastatic castration-resistant prostate cancer (CRPC), nearly all patients develop resistance. The purpose of this phase II study was to evaluate mechanisms of resistance to more complete androgen synthesis inhibition with abiraterone and dutasteride. EXPERIMENTAL DESIGN: Eligible metastatic CRPC patients underwent a baseline metastasis biopsy. Patients received abiraterone and prednisone for two 4-week cycles...
September 28, 2016: Clinical Cancer Research: An Official Journal of the American Association for Cancer Research
Tsui-Ting Ho, Jianguo Huang, Nanjiang Zhou, Ziqiang Zhang, Pratirodh Koirala, Xinchun Zhou, Fangting Wu, Xianfeng Ding, Yin-Yuan Mo
PCGEM1 is a long non-coding RNA (lncRNA) that is often upregulated in prostate cancer. However, little is known how PCGEM1 is regulated. In the present study, we show transcriptional regulation of PCGEM1 in response to androgen deprivation by p54/nrb. While ectopic expression of p54/nrb increases, suppression of p54/nrb by RNAi or knockout (KO) reduces PCGEM1. Moreover, rescue experiments indicate that re-expression of p54/nrb in KO cells restores the ability to induce PCGEM1, leading to upregulation of the androgen receptor splice variant AR3 which has been shown to play a role in castration resistance...
September 29, 2016: Scientific Reports
Yang Zhan, Guanyi Zhang, Xiaojie Wang, Yangfeng Qi, Dongyi Li, Shanshan Bai, Tianfang Ma, Erik K Flemington, Haitao Zhang, Oliver Sartor, Peng Lee, Yan Dong
: Androgen receptor splice variants (AR-Vs) are implicated in resistance of prostate cancer to androgen-directed therapies. When expressed alone in cells, some AR-Vs (e.g., AR-V7) localize primarily to the nucleus, whereas others (e.g., AR-V1, AR-V4, and AR-V6) localize mainly to the cytoplasm. Significantly, the latter are often co-expressed with the nucleus-predominant AR-Vs and the full-length AR (AR-FL). An important question to be addressed is whether the cytoplasmic-localized AR-Vs play a role in castration-resistant prostate cancer (CRPC) through interaction with the nucleus-predominant AR-Vs and AR-FL...
September 26, 2016: Molecular Cancer Research: MCR
Giulia Baciarello, Cora N Sternberg
Prostate cancer is initially responsive to androgen deprivation therapy, but most patients eventually develop castration-resistant disease. Enzalutamide is an androgen receptor (AR) inhibitor that targets several steps in the AR signaling pathway and has shown significant efficacy in the treatment of metastatic castration-resistant prostate cancer in patients with or without prior chemotherapy. To provide optimal treatment, it is important to understand the implications of enzalutamide use in the context of other therapies, as recent findings have suggested cross-resistance occurs between and within drug classes...
October 2016: Critical Reviews in Oncology/hematology
Emmanuel S Antonarakis, Chandtip Chandhasin, Erica Osbourne, Jun Luo, Marianne D Sadar, Frank Perabo
: : Despite the recent approval and widespread use of abiraterone acetate and enzalutamide for the treatment of castration-resistant prostate cancer (CRPC), this disease still poses significant management challenges because of various tumor escape mechanisms, including those that allow androgen receptor (AR) signaling to remain active. These AR-related resistance mechanisms include AR gene amplification or overexpression, constitutively active ligand-independent AR splice variants, and gain-of-function mutations involving the AR ligand-binding domain (LBD), among others...
September 14, 2016: Oncologist
Stephen Wilson, Jianfei Qi, Fabian V Filipp
Sequence motifs are short, recurring patterns in DNA that can mediate sequence-specific binding for proteins such as transcription factors or DNA modifying enzymes. The androgen response element (ARE) is a palindromic, dihexameric motif present in promoters or enhancers of genes targeted by the androgen receptor (AR). Using chromatin immunoprecipitation sequencing (ChIP-Seq) we refined AR-binding and AREs at a genome-scale in androgen-insensitive and androgen-responsive prostate cancer cell lines. Model-based searches identified more than 120,000 ChIP-Seq motifs allowing for expansion and refinement of the ARE...
2016: Scientific Reports
Emmanuel S Antonarakis, Jun Luo
No abstract text is available yet for this article.
September 9, 2016: Journal of Urology
Andrew K Kwegyir-Afful, Robert D Bruno, Puranik Purushottamachar, Francis N Murigi, Vincent C O Njar
Metastatic castration-resistant prostate cancer (mCRPC) accounts for a high percentage of prostate cancer mortality. The proprietary compound galeterone (gal) was designed to inhibit proliferation of androgen/androgen receptor (AR)-dependent prostate cancer cell in vitro and in vivo and is currently in phase III clinical development. Additionally, clinical studies with gal revealed its superb efficacy in four different cohorts of patients with mCRPC, including those expressing splice variant AR-V7. Preclinical studies with gal show that it also exhibits strong antiproliferative activities against AR-negative prostate cancer cells and tumors through a mechanism involving phosphorylation of eIF2α, which forms an integral component of the eukaryotic mRNA translation complex...
September 12, 2016: FEBS Journal
Johanna Känsäkoski, Jarmo Jääskeläinen, Tiina Jääskeläinen, Johanna Tommiska, Lilli Saarinen, Rainer Lehtonen, Sampsa Hautaniemi, Mikko J Frilander, Jorma J Palvimo, Jorma Toppari, Taneli Raivio
Mutations in the X-linked androgen receptor (AR) gene underlie complete androgen insensitivity syndrome (CAIS), the most common cause of 46,XY sex reversal. Molecular genetic diagnosis of CAIS, however, remains uncertain in patients who show normal coding region of AR. Here, we describe a novel mechanism of AR disruption leading to CAIS in two 46,XY sisters. We analyzed whole-genome sequencing data of the patients for pathogenic variants outside the AR coding region. Patient fibroblasts from the genital area were used for AR cDNA analysis and protein quantification...
2016: Scientific Reports
Carmen A Banuelos, Iran Tavakoli, Amy H Tien, Daniel P Caley, Nasrin R Mawji, Zhenzhen Li, Jun Wang, Yu Chi Yang, Yusuke Imamura, Luping Yan, Jian Guo Wen, Raymond J Andersen, Marianne D Sadar
Androgen receptor (AR) is a validated drug target for all stages of prostate cancer including metastatic castration-resistant prostate cancer (CRPC). All current hormone therapies for CRPC target the C-terminal ligand-binding domain of AR and ultimately all fail with resumed AR transcriptional activity. Within the AR N-terminal domain (NTD) is activation function-1 (AF-1) that is essential for AR transcriptional activity. Inhibitors of AR AF-1 would potentially block most AR mechanisms of resistance including constitutively active AR splice variants that lack the ligand-binding domain...
October 14, 2016: Journal of Biological Chemistry
Hogyoung Kim, Amrita Datta, Sudha Talwar, Sarmad N Saleem, Debasis Mondal, Asim B Abdel-Mageed
Estrogen receptor beta (ERβ) splice variants are implicated in prostate cancer (PC) progression; however their underlying mechanisms remain elusive. We report that non-canonical activation of estradiol (E2)-ERβ2 signaling axis primes growth, colony-forming ability and migration of the androgen receptor (AR)-null castration-resistant PC (CRPC) cells under androgen-deprived conditions (ADC). The non-classical E2-ERβ2 mediates phosphorylation and activation of Src-IGF-1R complex, which in turn triggers p65-dependent transcriptional upregulation of the androgen-regulated serine protease TMPRSS2:ETV5a/TMPRSS2:ETV5b gene fusions under ADC...
August 17, 2016: Oncotarget
Jingbo Qiao, Magdalena M Grabowska, Ingrid S Forestier-Roman, Janni Mirosevich, Thomas C Case, Dai H Chung, Justin M M Cates, Robert J Matusik, H Charles Manning, Renjie Jin
Numerous studies indicate that androgen receptor splice variants (ARVs) play a critical role in the development of castration-resistant prostate cancer (CRPC), including the resistance to the new generation of inhibitors of androgen receptor (AR) action. Previously, we demonstrated that activation of NF-κB signaling increases ARVs expression in prostate cancer (PC) cells, thereby promoting progression to CRPC. However, it is unclear how NF-κB signaling is activated in CRPC. In this study, we report that long-term treatment with anti-androgens increases a neuroendocrine (NE) hormone - gastrin-releasing peptide (GRP) and its receptor (GRP-R) expression in PC cells...
August 17, 2016: Oncotarget
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