Abstract 851: Interactions among transcription factors as a potential mechanism for inhibiting castrate-resistant prostate cancer (CRPCa) in transgenic adenocarcinoma of mouse prostate (TRAMP) through regulation of FLIP

Abstract

Abstract Androgens are critical regulators of prostate differentiation and function as well as prostate cancer growth and survival. Prostate tumors initially regress in response to androgen-ablation therapy. However, most cancers eventually relapse with an androgen-depletion-independent phenotype that is often more aggressive than the original androgen-dependent tumor. Studies from our laboratory demonstrated that intervention with 2-ME2[2-methoxyestradiol] prevents early stage prostate cancer development and causes regression of established prostate tumors in the transgenic adenocarcinoma of mouse prostate model. Although 2-ME2 was found to be safe, well tolerated, reduce or stabilize PSA levels when given to hormone refractory prostate cancer patients who had failed other treatments including hormone therapy, it was found to be less bioavailable. Accordingly second generation 2-ME2 was developed using nanocrystal colloidal dispersion technology and has increased its bioavailability by 5-10 fold (EntreMed, Inc, Rockville, MD). In the current study we tested the ability of this newly formulated 2-ME2 on the development and progression of castrate-resistant prostate cancer in TRAMP mice. 10-12 week old TRAMP mice were castrated and fed water containing different amounts of 2-ME2 for 6 weeks. Efficacy was evaluated by magnetic resonance imaging, determining the prostate seminal vesicle complex volume and histological analysis of prostate tumor or tissue. Our results also show that 2-ME2 inhibited development of CRPCa in these mice. Further molecular analysis using cell lines demonstrated 2-ME2 treatment significantly inhibited DHT-stimulated cell proliferation in androgen-responsive LNCaP cells (p<0.001). Further DHT-induced FLIP, PSA and AR transcriptional activity (as measured by promoter activities) were also reduced by 2-ME2 (p<0.001). Transient expression assays coupled with gel-shift and ChIP assays show binding of multiple transcription factors including Sp1, Sp3, NFκB and AR to the FLIP promoter. 2-ME2 treatment reduced such binding to the FLIP promoter as evidenced by ChIP. 2-ME2 treatment also modulated the interactions among these transcription factors as evidenced by Re-ChIP assays. Interestingly transcription factor CREB but not Sp1 seems to play a predominant role in androgen regulation of FLIP expression. Our findings suggest that 2-ME2 affects androgen induced survival of prostate cancer cells through regulation of FLIP involving potential interactions between multiple transcription factors. Supported by ACS RSG-04-169 and NIH CA 135451 (APK). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 851. doi:10.1158/1538-7445.AM2011-851