Reduced expression of the androgen receptor by third generation of antisense shows antitumor activity in models of prostate cancer.
The androgen receptor (AR) is a member of a unique class of transcription factors because it contains a ligand-binding domain that, when activated, results in nuclear translocation and the transcriptional activation of genes associated with prostate cancer development. Although androgen deprivation therapies are effective initially for the treatment of prostate cancer, the disease eventually relapses and progresses to castration-resistant prostate cancer (CRPC). Nonetheless, the AR still plays a critical role because late-stage investigational agents that deplete testosterone (abiraterone) or block ligand binding (MDV3100) can still control tumor growth in patients with CRPC. These findings indicate that downmodulation of AR expression may provide a complementary strategy for treating CRPC. In this article, we describe a novel, locked, nucleic acid-based antisense oligonucleotide, designated EZN-4176. When administered as a single agent, EZN-4176 specifically downmodulated AR mRNA and protein, and this was coordinated with inhibition of the growth of both androgen-sensitive and CRPC tumors in vitro as well as in animal models. The effect was specific because no effect on growth was observed with a control antisense oligonucleotide that does not recognize AR mRNA, nor on tumors derived from the PC3, AR-negative, tumor cell line. In addition, EZN-4176 reduced AR luciferase reporter activity in a CRPC model derived from C4-2b cells that were implanted intratibially, indicating that the molecule may control prostate cancer that has metastasized to the bone. These data, together with the continued dependency of CRPC on the AR signaling pathway, justify the ongoing phase I evaluation of EZN-4176 in patients with CRPC.
Department of Pharmacology, Enzon Pharmaceuticals, Inc., 20 Kingsbridge Road, Piscataway, NJ 08854, USA. yixian.zhang@enzon.com
Yixian
Y
Zhang
Stephen
S
Castaneda
Melissa
M
Dumble
Maoliang
M
Wang
Mary
M
Mileski
Zhengxing
Z
Qu
Steven
S
Kim
Victoria
V
Shi
Patricia
P
Kraft
Ying
Y
Gao
Jenny
J
Pak
Puja
P
Sapra
Raj
R
Bandaru
Hong
H
Zhao
Robert L
RL
Vessella
Ivan D
ID
Horak
Lee M
LM
Greenberger
D000726:Androgen Antagonists / Q000494:pharmacology / Q000627:therapeutic use; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D002277:Carcinoma / Q000188:drug therapy / Q000235:genetics / Q000473:pathology*; D045744:Cell Line, Tumor; D004247:DNA / Q000494:pharmacology / Q000627:therapeutic use; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology* / Q000627:therapeutic use; D009919:Orchiectomy; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000473:pathology*; D011944:Receptors, Androgen / Q000235:genetics* / Q000378:metabolism; D017211:Treatment Failure; D023041:Xenograft Model Antitumor Assays
C571998:5'-ACCaagtttcttcAGC-3'; C410798:AR protein, human; D000726:Androgen Antagonists; D000970:Antineoplastic Agents; D020319:Oligodeoxyribonucleotides, Antisense; D011944:Receptors, Androgen; D004247:DNA