Abstract 4334: Greater resistance of mutant p53 tumor cells to hypoxia or chloroquine with glucose or pyruvate supplementation is diminished under glucose starvation

Abstract

Abstract BACKGROUND. Poorly vascularized solid tumors are exposed to regions of low oxygen and glucose deprivation. These restrictions may promote either defensive autophagy or cell death through excessive reactive oxygen species (ROS), mediated by activated NADPH oxidases (NOX) which transport electrons from NADPH on the cytoplasmic side of plasma membranes to reduce molecular oxygen at the extracellular space, increasing superoxide anion radical (O2•-). .OBJECTIVES. To investigate in genetically-matched human melanoma cells with wt or mutant p53, responses to: a) autophagy inhibitor chloroquine and to glucose-lowering metformin or to hypoxia in glucose-supplemented medium; b) pyruvate in glucose-free medium under normoxia or hypoxia; c) sub-physiological glucose. EXPERIMENTAL. Responses to normoxia or hypoxia were assesed by live-dead fluorometric assays, or by crystal violet staining of surviving cells. Mechanisms influencing response to glucose limitation were studied by specific immune blotting. RESULTS. Lower susceptibility to chloroquine ± metformin involving greater basal AMPK activation was seen in physiological 5 mM glucose in mutant p53 cells. These cells were also preferentially protected from prolonged hypoxia by glucose supplementation or by pyruvate supplementation of glucose-free medium under normoxia, but not under hypoxia. Sub-physiological glucose without pyruvate induced apoptosis-associated PARP cleavage irrespective of p53 status. However, treatment with impermeable exogenous superoxide dismutase (SOD) to remove extracellular superoxide signalling across cell membranes, preferentially counteracted PARP cleavage only in wt p53 cells with lower LDHA expression after 48 hr in 2.5 mM glucose. CONCLUSIONS. Glucose availability increases resistance to hypoxia or to chloroquine ± metformin in mutant p53 cells. However, glucose starvation promotes toxicity linked to extracellular (O2•-), preferentially in mutant p53 cells. Citation Format: Manuel Rieber. Greater resistance of mutant p53 tumor cells to hypoxia or chloroquine with glucose or pyruvate supplementation is diminished under glucose starvation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4334. doi:10.1158/1538-7445.AM2014-4334