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¹ Molecular Oncology and Experimental Therapeutics Programs, H. Lee Moffitt Cancer Center and Research Institute; Departments of ² Interdisciplinary Oncology and ³ Pathology, University of South Florida College of Medicine, Tampa, Florida; ⁴ Department of Urology, University of Kansas Medical Center, Kansas City, Kansas; and ⁵ Department of Oncology, Novartis Institutes for Biomedical Research, East Hanover, New Jersey

Requests for reprints: Jie Wu, Molecular Oncology Program, SRB-3, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612. Phone: 813-745-6713; Fax: 813-745-3829. E-mail: wu{at}moffitt.usf.edu

Androgen receptor plays a critical role in the development of primary as well as advanced hormone-refractory prostate cancer. Therefore, ablation of androgen receptor from prostate cancer cells is an interesting concept for developing a new therapy not only for androgen-dependent prostate cancer but also for metastatic hormone-refractory prostate cancer, for which there is no effective treatment available. We report here that LAQ824, a cinnamyl hydroxamatic acid histone deacetylase inhibitor currently in human clinical trials, effectively depleted androgen receptor in prostate cancer cells at nanomolar concentrations. LAQ824 seemed capable of depleting both the mutant and wild-type androgen receptors in either androgen-dependent and androgen-independent prostate cancer cells. Although LAQ824 may exert its effect through multiple mechanisms, several lines of evidence suggest that inactivation of the heat shock protein-90 (Hsp90) molecular chaperone is involved in LAQ824-induced androgen receptor depletion. Besides androgen receptor, LAQ824 reduced the level of Hsp90 client proteins HER-2 (ErbB2), Akt/PKB, and Raf-1 in LNCaP cells. Another Hsp90 inhibitor, 17-allyamino-17-demethoxygeldanamycin (17-AAG), also induced androgen receptor diminution. LAQ824 induced Hsp90 acetylation in LNCaP cells, which resulted in inhibition of its ATP-binding activity, dissociation of Hsp90-androgen receptor complex, and proteasome-mediated degradation of androgen receptor. Consequently, LAQ824 blocked androgen-induced prostate-specific antigen production in LNCaP cells. LAQ824 effectively inhibited cell proliferation and induced apoptosis of these prostate cancer cells. These results reveal that LAQ824 is a potent agent for depletion of androgen receptor and a potential new drug for prostate cancer.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Note: L. Chen and S. Meng contributed equally to this work.

⁶ Novagen, Innovations Newsletter 2004;19:6–9.

Received 10/28/04; revised 7/15/05; accepted 7/15/05.