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Clin Cancer Res. 2013 Oct 15;19(20):5658-74. doi: 10.1158/1078-0432.CCR-13-0422. Epub 2013 Aug 13.

Pharmacologic inhibition of Jak2-Stat5 signaling By Jak2 inhibitor AZD1480 potently suppresses growth of both primary and castrate-resistant prostate cancer.

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  • 1Authors' Affiliations: Departments of Cancer Biology, Urology, Pathology, and Medical Oncology, Kimmel Cancer Center; Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania; and Oncology iMED, AstraZeneca R&D Boston, Waltham, Massachusetts.

Abstract

PURPOSE:

Progression of prostate cancer to the lethal castrate-resistant stage coincides with loss of responsiveness to androgen deprivation and requires development of novel therapies. We previously provided proof-of-concept that Stat5a/b is a therapeutic target protein for prostate cancer. Here, we show that pharmacologic targeting of Jak2-dependent Stat5a/b signaling by the Jak2 inhibitor AZD1480 blocks castrate-resistant growth of prostate cancer.

EXPERIMENTAL DESIGN:

Efficacy of AZD1480 in disrupting Jak2-Stat5a/b signaling and decreasing prostate cancer cell viability was evaluated in prostate cancer cells. A unique prostate cancer xenograft mouse model (CWR22Pc), which mimics prostate cancer clinical progression in patients, was used to assess in vivo responsiveness of primary and castrate-resistant prostate cancer (CRPC) to AZD1480. Patient-derived clinical prostate cancers, grown ex vivo in organ explant cultures, were tested for responsiveness to AZD1480.

RESULTS:

AZD1480 robustly inhibited Stat5a/b phosphorylation, dimerization, nuclear translocation, DNA binding, and transcriptional activity in prostate cancer cells. AZD1480 reduced prostate cancer cell viability sustained by Jak2-Stat5a/b signaling through induction of apoptosis, which was rescued by constitutively active Stat5a/b. In mice, pharmacologic targeting of Stat5a/b by AZD1480 potently blocked growth of primary androgen-dependent as well as recurrent castrate-resistant CWR22Pc xenograft tumors, and prolonged survival of tumor-bearing mice versus vehicle or docetaxel-treated mice. Finally, nine of 12 clinical prostate cancers responded to AZD1480 by extensive apoptotic epithelial cell loss, concurrent with reduced levels of nuclear Stat5a/b.

CONCLUSIONS:

We report the first evidence for efficacy of pharmacologic targeting of Stat5a/b as a strategy to inhibit castrate-resistant growth of prostate cancer, supporting further clinical development of Stat5a/b inhibitors as therapy for advanced prostate cancer.

©2013 AACR.

PMID:
23942095
[PubMed - indexed for MEDLINE]
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