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

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.

• Authors: Yoshiaki Yamamoto, Yohann Loriot, Eliana Beraldi, Fan Zhang, Alexander W Wyatt, Nader Al Nakouzi, Fan Mo, Tianyuan Zhou, Youngsoo Kim, Brett P Monia, A Robert MacLeod, Ladan Fazli, Yuzhuo Wang, Colin C Collins, Amina Zoubeidi, Martin Gleave
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 21 Issue 7 Pg. 1675-87 (Apr 01 2015) ISSN: 1557-3265 [Electronic] United States
• PMID: 25634993 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: ©2015 American Association for Cancer Research.

Chemical References

• AR protein, human
• Antineoplastic Agents
• Benzamides
• Nitriles
• Oligonucleotides, Antisense
• Protein Isoforms
• RNA, Small Interfering
• Receptors, Androgen
• Phenylthiohydantoin
• enzalutamide

Topics

• Animals
• Antineoplastic Agents (pharmacology)
• Benzamides
• Blotting, Western
• Drug Resistance, Neoplasm (genetics)
• Humans
• Immunohistochemistry
• Male
• Mice
• Nitriles
• Oligonucleotides, Antisense (pharmacology)
• Phenylthiohydantoin (analogs & derivatives, pharmacology)
• Prostatic Neoplasms, Castration-Resistant (drug therapy, genetics)
• Protein Isoforms
• RNA, Small Interfering
• Receptors, Androgen (genetics)
• Reverse Transcriptase Polymerase Chain Reaction
• Transfection
• Xenograft Model Antitumor Assays