Abstract 1852: Pyruvate dehydrogenase kinase expression and metabolic changes following dichloroacetate exposure in anoxia in human colorectal cancer cells.

Abstract

Abstract Introduction: While glycolysis is a suboptimal metabolic strategy used by cells under hypoxic conditions, many cancer cells preferentially utilize glycolysis for energy production in the presence of abundant oxygen, a phenomenon known as the “Warburg Effect”. Dichloroacetate (DCA) is a small molecule metabolic modulator that shifts cellular metabolism to glucose oxidation by inhibition of pyruvate dehydrogenase kinase (PDK), an enzymatic inhibitor of pyruvate dehydrogenase (PDH). Furthermore, DCA has been shown to induce apoptosis in cancer but not normal cells. Our previous work showed that some human colorectal cancer (CRC) cells are protected from anoxia-induced apoptosis upon exposure to DCA, through as yet unclear mechanisms. Hypothesis: It is hypothesized that differential expression of PDK isoforms will correlate with the ability of different cancer cells to withstand the apoptotic effects of DCA in anoxia. Methods: SW480, LS174T (CRC) and IEC-18 (normal intestinal epithelial) cell lines were exposed to 10 mM DCA in either normoxic (20% O2) or anoxic (< 0.1% O2) conditions for 24 hours. Following treatment, expression of different PDK isoforms was determined through qRT-PCR and western blotting. Phosphorylation of PDH at Ser293 and Ser300 was assessed through western blotting. Glucose consumption and lactate production was determined using a colorimetric-based assay. Changes in mitochondrial function were quantified through Mitotracker staining and subsequent flow cytometry. Cell viability was assessed using the neutral red assay. Results: In all three cell lines: A) PDK isoforms 1 and 3 are highly expressed relative to isoforms 2 and 4, B) DCA and/or anoxic treatment induced a greater effect on PDH phosphorylation at Ser300 than Ser293, and C) DCA had minimal effect on glucose consumption in either normoxia or anoxia. Conclusions: Altered PDK expression and PDH activation may not fully explain the differences in resistance to DCA-induced apoptosis observed in human CRC cells. Investigating the mechanisms by which certain cancer cells are protected from DCA-induced apoptosis will lead to a better understanding of cancer metabolism and thus provide better therapeutic opportunities. Citation Format: Nelson Ho, Brenda L. Coomber. Pyruvate dehydrogenase kinase expression and metabolic changes following dichloroacetate exposure in anoxia in human colorectal cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1852. doi:10.1158/1538-7445.AM2013-1852