Abstract 2583: Targeting a novel pathway for prostate cancer therapy
Authors: Kegel Stacy , Mehraein-Ghomi Farideh , Reuter Quentin , Schmidt Joseph , Church Dawn , Hoffmann F. Michael , Basu Hirak , Wilding George 
Published: June 2012

Development of an effective therapy to prevent prostate cancer (PCa) progression to castrate-resistant PCa (CRPCa) remains an unmet medical need, mainly due to a poor understanding of the mechanism of PCa progression. Reactive oxygen species (ROS) are produced in high amounts in PCa cells and play a major role in PCa development and progression. We have published that activated androgen receptor (AR)-JunD complex induces spermidine/spermine N1-acetyl transferase (SSAT), the first and regulatory enzyme in a major polyamine catabolism pathway that yields over-production of ROS specifically in the polyamine-rich PCa cells. Our recent data further suggest an intriguing mechanism of PCa progression, where AR-JunD induced SSAT expression and consequent upregulation of the transcription factor NF-κB may set up an autocrine feed forward loop of SSAT-ROS-NFκB-SSAT that can sustain ROS production and PCa cell proliferation in the absence of androgen. A focus of our current research is to identify compounds that specifically target and block steps in this novel pathway downstream to AR activation and thereby have potential to be new targeted therapeutic agents to prevent PCa progression to CRPCa in early stage progressing PCa patients with minimal side effects. In the research presented here we utilized a novel high throughput screen (HTS) assay to find compounds that prevent the initiating AR-JunD interaction step in this ROS generating pathway and tested their efficacy in PCa cells.

A high throughput assay based on Gaussia Luciferase enzyme reconstitution via protein-protein interaction was used to screen the NCI diversity set library of drug like molecules to identify inhibitors of the AR-JunD interaction. Selected hits were further screened to determine their ability to bind to the AR using a published fluorescence polarization assay in order to categorize the molecules as non-antiandrogens or antiandrogens. As we intend to target the pathway downstream of AR activation, we focused on non-antiandrogens, further testing them for efficacy against androgen induced ROS generation and effect on cell growth in PCa cells in vitro by our published DCFH dye oxidation and DNA fluorescence assays.

Of the 14 hits from the HTS assay of the NCI diversity set library, nine small molecules were chosen based on their drug-like chemical characteristics for further studies along with two synthesized analogs of one of the selected small molecules. We have categorized six agents as non-antiandrogens and five as having some antiandrogenic activity. Our ROS assay identified a lead non-antiandrogen compound that blocks androgen induced ROS production in PCA cells at less than 1uM concentration. This agent also significantly inhibited androgen-independent growth of PCa cells at 4uM. Data for all compounds will be presented.

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 2583. doi:10.1158/1538-7445.AM2011-2583