Abstract 4073: Effects of metabolic and mitochondrial-targeted compounds on ovarian cancer cells

Abstract

Abstract Ovarian cancer has the highest mortality rate of all the gynecological cancers in the United States, and is highly resistant to current forms of treatment. Metformin, a type II diabetes drug, and phenethyl isothiocyanate (PEITC), a component of cruciferous vegetables, were examined for their effects on ovarian cancer cell growth and survival. Although the exact mechanism of both drugs is not known, both have been found to inhibit complexes within the electron transport chain. Metformin is also known to activate the AMPK-LKB1 pathway, possibly downstream of complex I inhibition. We examined the effects of these compounds in vitro to evaluate the potential of electron transport chain inhibitors as novel therapies for ovarian cancer. To assess cell growth and death, hemacytometry with trypan blue exclusion was used in the ovarian cancer cell lines: SKOV3, OVCAR3, CAOV3, and PA-1. Induction of apoptosis was measured by Western blotting for intact and cleaved poly-ADP ribose polymerase (PARP). Western blotting was also used to determine endogenous levels of enzymes responsible for clearing reactive oxygen species (ROS). Levels of mitochondrial ROS production were measured by flow cytometry and confocal microscopy using the fluorescent probe MitoSOX. Metformin treatment was found to induce cell death in PA-1, arrest growth in OVCAR3 and CAOV3, and slow growth in SKOV3. PEITC treatment induced cell death through apoptosis in all tested cell lines at low micromolar concentrations. Metformin's inhibitory effects were partially reversed when growth medium was supplemented with succinate to bypass complex I. Low expression levels of anti-oxidant enzymes were also found to correspond with higher sensitivity to metformin and PEITC. Additionally, levels of mitochondrial ROS increased with treatment. Metformin and PEITC both show potential as ovarian cancer therapies. Complex I inhibition likely contributes to metformin's anti-cancer effects, as succinate supplementation was able to reverse growth inhibition. Additional work is necessary to determine if the increase in mitochondrial ROS is caused by electron transport chain complex inhibition and whether it is essential to the anti-cancer effects observed. 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 4073. doi:10.1158/1538-7445.AM2011-4073