title: Generation 2.5 antisense oligonucleotides targeting the androgen receptor and its splice variants suppress enzalutamide-resistant prostate cancer cell growth.
abstract: OBJECTIVE
  Enzalutamide (ENZ) is a potent androgen receptor (AR) antagonist with activity in castration-resistant prostate cancer (CRPC); however, progression to ENZ-resistant (ENZ-R) CRPC frequently occurs with rising serum PSA levels, implicating AR full-length (ARFL) or variants (AR-Vs) in disease progression.
  
  
  METHODS
  To define functional roles of ARFL and AR-Vs in ENZ-R CRPC, we designed 3 antisense oligonucleotides (ASO) targeting exon-1, intron-1, and exon-8 in AR pre-mRNA to knockdown ARFL alone or with AR-Vs, and examined their effects in three CRPC cell lines and patient-derived xenografts.
  
  
  RESULTS
  ENZ-R-LNCaP cells express high levels of both ARFL and AR-V7 compared with CRPC-LNCaP; in particular, ARFL levels were approximately 12-fold higher than AR-V7. Both ARFL and AR-V7 are highly expressed in the nuclear fractions of ENZ-R-LNCaP cells even in the absence of exogenous androgens. In ENZ-R-LNCaP cells, knockdown of ARFL alone, or ARFL plus AR-Vs, similarly induced apoptosis, suppressed cell growth and AR-regulated gene expression, and delayed tumor growth in vivo. In 22Rv1 cells that are inherently ENZ-resistant, knockdown of both ARFL and AR-Vs more potently suppressed cell growth, AR transcriptional activity, and AR-regulated gene expression than knockdown of ARFL alone. Exon-1 AR-ASO also inhibited tumor growth of LTL-313BR patient-derived CRPC xenografts.
  
  
  CONCLUSIONS
  These data identify the AR as an important driver of ENZ resistance, and while the contributions of ARFL and AR-Vs can vary across cell systems, ARFL is the key driver in the ENZ-R LNCaP model. AR targeting strategies against both ARFL and AR-Vs is a rational approach for AR-dependent CRPC.
authors: The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada. Department of Urology, Graduate School of Medicine, Yamaguchi University, Ube, Japan.
authors: Yoshiaki
authors: Y
authors: Yamamoto
authors: The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Yohann
authors: Y
authors: Loriot
authors: The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Eliana
authors: E
authors: Beraldi
authors: The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Fan
authors: F
authors: Zhang
authors: The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Alexander W
authors: AW
authors: Wyatt
authors: The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Nader
authors: N
authors: Al Nakouzi
authors: The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Fan
authors: F
authors: Mo
authors: Department of Antisense Drug Discovery, Isis Pharmaceuticals Inc., Carlsbad, California.
authors: Tianyuan
authors: T
authors: Zhou
authors: Department of Antisense Drug Discovery, Isis Pharmaceuticals Inc., Carlsbad, California.
authors: Youngsoo
authors: Y
authors: Kim
authors: Department of Antisense Drug Discovery, Isis Pharmaceuticals Inc., Carlsbad, California.
authors: Brett P
authors: BP
authors: Monia
authors: Department of Antisense Drug Discovery, Isis Pharmaceuticals Inc., Carlsbad, California.
authors: A Robert
authors: AR
authors: MacLeod
authors: The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Ladan
authors: L
authors: Fazli
authors: The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Yuzhuo
authors: Y
authors: Wang
authors: The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Colin C
authors: CC
authors: Collins
authors: The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Amina
authors: A
authors: Zoubeidi
authors: The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada. m.gleave@ubc.ca.
authors: Martin
authors: M
authors: Gleave
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001549:Benzamides; D015153:Blotting, Western; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D009570:Nitriles; D016376:Oligonucleotides, Antisense / Q000494:pharmacology*; D010669:Phenylthiohydantoin / Q000031:analogs & derivatives* / Q000494:pharmacology; D064129:Prostatic Neoplasms, Castration-Resistant / Q000188:drug therapy / Q000235:genetics*; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D011944:Receptors, Androgen / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D023041:Xenograft Model Antitumor Assays
chemical_list: C410798:AR protein, human; D000970:Antineoplastic Agents; D001549:Benzamides; D009570:Nitriles; D016376:Oligonucleotides, Antisense; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D011944:Receptors, Androgen; D010669:Phenylthiohydantoin; C540278:enzalutamide