Abstract 5509: A drug-screening model to identify compounds active in cells under metabolic stress

Abstract

Abstract Background and aim: Promising anticancer compounds often fail in vivo due to lack of efficacy. Drug screenings to identify anticancer agents are usually performed in culture conditions that very poorly represent the complex metabolic tumor environment. Tumor tissues are characterised by low oxygen (hypoxia) and acidic extracellular pH (acidosis). A screen of a drug-library for compounds able to induce cell death in acidic/hypoxic conditions may lead to discover effective drugs targeting quiescent/hypoxic cells, normally considered responsible for tumor relapses after therapy. Methods: The colon carcinoma cell line HCT-116 has been adapted to grow in low pH conditions (pH 6.8). The Prestwick compound library (1200 FDA-approved compounds) was used to validate the assay. Cell viability was measured using the acid phosphatase assay after 48 hours exposure to test compounds. The assay was validated in HCT-116 cells cultured in normoxic and hypoxic conditions. Multicellular spheroids (MCS) were used to evaluate the sensitivity to hit compounds confirmed at least three times in 2D culture conditions. Results: The assay was optimized to perform the screening at pH 6.8 in normoxic and hypoxic conditions. Experiments have demonstrated the ability of cells to survive and grow in hypoxic conditions (1% oxygen) for at least 4 days. The test was optimized in terms of number of plated cells and serum concentration. Hit compounds were identified based on the mean values for quality control plus 3 standard deviations of untreated samples. The screen led to identify 20 hits for both conditions and 11 hits were further confirmed for hypoxic/acidic conditions. Auranofin and Verteporfin showed to better induce cell death in cells adapted or acutely exposed to low pH compared to parental cells and immortalized epithelial cells (RPE1). Both drugs showed cytotoxic effects on cells grown as MCS, suggesting a potential good efficacy of the therapeutic agent in vivo. In addition, the screening of about 10000 compounds of the LCBKI library is ongoing and about 100 hits have been identified. Conclusions: The screening validation on the Prestwick library will hopefully lead to identify potential “off-label” effects of already approved drugs. The screening of larger drug-libraries will hopefully lead to find and characterize more compounds able to target slow proliferating and therapy resistant cells. Citation Format: Paola Pellegrini, Martin Haraldsson, Annika Jenmalm Jensen, Thomas Lundbäck, Angelo De Milito. A drug-screening model to identify compounds active in cells under metabolic stress. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5509. doi:10.1158/1538-7445.AM2015-5509