Abstract A58: High Throughput Search for a Combination Cancer Preventive Treatment

Abstract

Abstract Identification of safer chemopreventive drugs is essential for the future of cancer preventive treatment. Although the feasibility for chemoprevention of estrogen receptor (ER) -positive breast cancers has been exemplified by the use of selective estrogen response modifiers (SERMs), we are still lacking preventive options for many other disease types, including breast cancers not dependent on ER status. Rexinoids are a class of agents that effectively reduce the incidence of both ER-positive and -negative tumors in animal models of breast cancer and thus may be better cancer preventive drugs than the current standard SERMs. However, significant side-effects at the effective clinical dose, including hypertriglyceridemia and weight gain, limit its generalized use. A phase II biomarker trial of the synthetic rexinoid, bexarotene (Targretin, LGD1069) demonstrated that bexarotene reduces expression of the proliferation markers Ki67 and Cyclin D1 in normal breast epithelium of postmenopausal women, suggesting that the cancer preventive effects of bexarotene are associated with its ability to elicit cell cycle blockade and inhibit proliferation of premalignant mammary epithelial cells. Here we hypothesize that the combination of repurposed drugs and some small molecule compounds with low dose rexinoid will minimize toxicity and result in effective anti-proliferative in premalignant cells. Therefore, we designed an image-based in vitro assay system to conduct high throughput screens to identify existing drugs and drug-like small molecules which enhance the growth suppressive effect of cancer preventive rexinoids. We used an automated 96 well platform to test the NIH clinical collection of drugs and a library of structurally diverse compounds (MayBridge Hitfinder) alone or in combination with 100nM bexarotene. Through multiparametric determination of cell counts, DNA content and cellular toxicity, we identified combination treatments of premalignant breast cells that fit the above criteria and report on dose-response studies and secondary screens for optimal dose and cell health. Validation of some of the candidate agents and plans for in vivo testing of their chemopreventive activity will be discussed. Citation Format: Ivan P. Uray, Powel H. Brown. High-throughput search for a combination cancer preventive treatment. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr A58.