Generation 2.5 antisense oligonucleotides targeting the androgen receptor and its splice variants suppress enzalutamide-resistant prostate cancer cell growth

  • Clin Cancer Res. 2015 Apr 1;21(7):1675-87. doi: 10.1158/1078-0432.CCR-14-1108.
Yoshiaki Yamamoto  1 ,  Yohann Loriot  2 ,  Eliana Beraldi  2 ,  Fan Zhang  2 ,  Alexander W Wyatt  2 ,  Nader Al Nakouzi  2 ,  Fan Mo  2 ,  Tianyuan Zhou  3 ,  Youngsoo Kim  3 ,  Brett P Monia  3 ,  A Robert MacLeod  3 ,  Ladan Fazli  2 ,  Yuzhuo Wang  2 ,  Colin C Collins  2 ,  Amina Zoubeidi  2 ,  Martin Gleave  4
Affiliations
  • 1. 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.
  • 2. The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
  • 3. Department of Antisense Drug Discovery, Isis Pharmaceuticals Inc., Carlsbad, California.
  • 4. The Vancouver Prostate Centre and Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada. [email protected].
PMID: 25634993 DOI: 10.1158/1078-0432.CCR-14-1108
Abstract

Purpose: 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.

Experimental design: 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.

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