AT-101 (R-()-Gossypol Acetic Acid) Enhances the Effectiveness of Androgen Deprivation Therapy in the VCaP Prostate Cancer Model Natalie McGregor, 1 Lalit Patel, 1 Matthew Craig, 1 Savannah Weidner, 1 Shaomeng Wang, 1,2 and Kenneth J. Pienta 1,2,3,4 * 1 Department of Internal Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan 2 University of Michigan Comprehensive Cancer Center, Ann Arbor, Michigan 3 Department of Urology, University of Michigan School of Medicine, Ann Arbor, Michigan 4 Michigan Center for Translational Pathology, Ann Arbor, Michigan ABSTRACT Prostate cancer remains a leading cause of cancer death in American men. Androgen deprivation therapy (ADT) is the most common treatment for advanced prostate cancer patients; however, ADT fails in nearly all cases resulting in castration resistant or androgen-insensitive (AI) disease. In many cases, this progression results from dysregulation of the pro-survival Bcl-2 family proteins. Inhibition of pro-survival Bcl-2 family proteins, therefore, may be an effective strategy to delay the onset of AI disease. Gossypol, a small molecule inhibitor of pro-survival Bcl-2 family proteins, has been demonstrated to inhibit AI prostate cancer growth. The apoptotic effect of gossypol, however, has been demonstrated to be attenuated by the presence of androgen in a prostate cancer xenograft mouse model (Vertebral Cancer of Prostate [VCaP]) treated with AT-101 (R-()-gossypol acetic acid). This study was undertaken to better understand the in vitro effects of androgen receptor (AR) on AT-101-induced apoptosis. VCaP cells treated with AT-101 demonstrated an increase in apoptosis and downregulation of Bcl-2 pro- survival proteins. Upon AR activation in combination with AT-101 treatment, apoptosis is reduced, cell survival increases, and caspase activation is attenuated. Akt and X inhibitor of apoptosis (XIAP) are downregulated in the presence of AT-101, and AR stimulation rescues protein expression. Combination treatment of bicalutamide and AT-101 increases apoptosis by reducing the expression of these pro-survival proteins. These data suggest that combination therapy of AT-101 and ADT may further delay the onset of AI disease, resulting in prolonged progression-free survival of prostate cancer patients. J. Cell. Biochem. 110: 1187–1194, 2010. ß 2010 Wiley-Liss, Inc. KEY WORDS: PROSTATE CANCER; GOSSYPOL; APOPTOSIS; BCL-2; ANDROGEN DEPRIVATION THERAPY P rostate cancer is the second leading cause of cancer death in men, second only to lung cancer in the US. It is estimated that in 2009 prostate cancer will have accounted for 25% of malignancies in men, with 192,280 new cases in the US. In addition, 9% of all estimated cancer deaths of men will be due to prostate cancer in the US [Jemal et al., 2009]. Localized disease is highly curable through local therapies including radiation therapy and/or radical prostatectomy; however, 20% of men diagnosed will have a relapse of disease at metastatic sites [Fujimoto et al., 2005; Taichman et al., 2007; Walczak and Carducci, 2007]. Huggins and Hodges [1941] reported that reducing circulating testosterone levels via surgical castration resulted in a dramatic palliation of cancer symptoms and an overall improvement in quality of life [Perlmutter and Lepor, 2007]. Soon after these reports, reductions in testosterone levels through androgen deprivation therapy (ADT) became widely used as the first-line treatment for advanced prostate cancer. Unfortunately, the patients on ADT progress to castration-resistant or androgen-independent (AI) disease within 2–3 years [Pienta and Bradley, 2006; Walczak and Carducci, 2007]. The onset of this advanced state heralds a patient life expectancy of approximately 16–18 months [Pienta and Bradley, 2006]. Androgens are important regulators of growth and differentiation in the prostate gland [Miyamoto et al., 2004; Perlmutter and Lepor, Journal of Cellular Biochemistry ARTICLE Journal of Cellular Biochemistry 110:1187–1194 (2010) 1187 Grant sponsor: NCI Grant U-19; Grant number: CA113317; Grant sponsor: NIH SPORE in Prostate Cancer Grant P50; Grant number: CA46592. *Correspondence to: Kenneth J. Pienta, MD, 1500 E. Medical Center Drive, 7303 Cancer Center, Ann Arbor, MI 48109- 5946. E-mail: kpienta@umich.edu Received 25 March 2010; Accepted 29 March 2010  DOI 10.1002/jcb.22633  ß 2010 Wiley-Liss, Inc. Published online 29 June 2010 in Wiley InterScience (www.interscience.wiley.com).