Abstract 3846: A metabolic pathway targeted inhibitor for precision therapy of castrate-resistant prostate cancer
Authors: Basu Hirak S. , Wilgonowski Nathaniel L. , Lieblich Jessica L. , Wu Grace T. , Fokt Izabela , Ramachandran Sumankalai , Yu Jiaquin , Titus Mark , Priebe Waldemar , Beebe David J. , Wilding George 
Published: August 2018

Background: We have previously reported that an AP-1 factor JunD is overexpressed in PCa. It complexes with androgen receptor (AR) to induce spermidine/spermine acetyl transferase (SSAT). SSAT initiates polyamine oxidation that generates copious amounts of reactive oxygen species (ROS) production in polyamine-rich PCa cells. ROS activate NF-κB. NF-κB also induces SSAT and activates AR. This sets-up a feed-forward loop for PCa growth at low androgen. An IHC assay for SSAT can be utilized to identify PCa patients with this loop activated. AR-N-terminal targeted inhibitors that block AR interactions with JunD and NF-κB can be developed as a precision therapy for these patients. Method: We applied Immunocytochemistry (ICC), proteomic and metabolomic techniques to analyze stationary and invading cells that are separated in a novel micro-scale dvice to understand the mechanism of invasion. Gaussia luciferase reconstitution assay in a high throughput screen (HTS) to identify inhibitors of AR-JunD and AR-NF-κB interactions. In vitro cell growth assay along with in vivo pharmacokinetic (PK), maximum tolerated dose (MTD) and enzalutamide-resistant CRPC cell xenograft growth in nude mice are used to optimize the lead. Unpublished data: Immunocytochemistry (ICC) data show that in cultured enzalutamide-resistant C4-2 and -sensitive LNCaP cells as well as in some patient PCa cells, more SSAT positive cells are in the migratory than in the stationary section of the microscale device. Screening of 27,000+ compounds from 2 different chemical libraries detected a single compound that specifically inhibits both AR-JunD and AR-NF-κB2 (p52) interactions. We have synthesized several of its analogs. Lead analogs inhibit growth of AR-positive C4-2 and LNCaP cells at nanomolar concentration, but have little effect on the growth of AR-negative PC-3 and SSAT silent siSSAT cells in culture. Co-immunoprecipitation (co-IP) assay shows its efficacy in inhibiting AR-JunD and AR-p52 interactions in situ. It has been formulated in 25% ethanol:water and administered orally. PCa tumor bearing nude mice tolerated it at 50 mg/kg p.o. daily for more than 28 days and has a serum Cmax of ~ 3 μM within 30 minutes and a plasma t1/2 of ~1 h after a single oral dose of 100 mg/kg. Twenty four hours after dosing it is found in the flank tumor (1.5 ng/mg tissue; ~450 nM) and in the prostate tissues (10 ng/mg tissue; ~3 μM) in addition to liver and kidney and inhibited growth of C4-2 xenografts in nude mice.

Citation Format: Hirak S. Basu, Nathaniel L. Wilgonowski, Jessica L. Lieblich, Grace T. Wu, Izabela Fokt, Sumankalai Ramachandran, Jiaquin Yu, Mark Titus, Waldemar Priebe, David J. Beebe, George Wilding. A metabolic pathway targeted inhibitor for precision therapy of castrate-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3846.