Abstract 5155: Suppression of gluconeogenesis in hepatocellular carcinoma by miR-23 directed downregulation of key gluconeogenic enzymes and the transcription factor <i>PGC-1α</i>
Authors: Bo Wang, Shuhao Hsu, Wendy Frankel, Kalpana Ghoshal, Samson T. Jacob
Journal: Cancer Research (2012)

Abstract Although the mechanism and functional significance of high levels of aerobic glycolysis in cancer cells (Warburg effect) have been extensively studied, the possibility of altered gluconeogenesis that could potentially facilitate glycolytic pathway has not been explored. To examine this possibility, we investigated the potential alteration in expression of the key enzymes in gluconeogenesis pathway and its underlying mechanism using a mouse HCC model and primary human HCC. In the mouse model, C57/BL6 mice fed choline deficient and amino acid defined (CDAA) diet progressively develop nonalcoholic steatohepatitis (NASH), foci of altered hepatocytes (FAH) and ultimately hepatocellular carcinoma (HCC). The expression of genes encoding glucose-6-phosphatase (G6PC), phosphoenolpyruvate carboxykinase (PEPCK), fructose-1,6-bisphosphatase (FBP1), and pyruvate carboxylase (PC), key enzymes involved in gluconeogenesis, as well as PGC-1α, a transcription factor that regulates G6PC and PEPCK expression, was drastically reduced in the tumors. Increased serum ALT and decreased serum glucose levels correlated well with the liver damage and inhibition of gluconeogenesis in the tumor bearing mice. The mRNA levels G6PC, PEPCK, FBP1 and PGC-1α were also curtailed by ∼80% in the majority of primary human HCCs compared to matching peritumoral livers. Further, the glucose 6-phosphatase activity was markedly diminished in the mouse liver tumors and human primary HCCs, and G6PC expression correlated with tumor grade in human primary HCCs. The expression of miR-23a, a candidate microRNA targeting PGC-1α and G6PC, was significantly elevated in mouse and human HCCs. We established that PGC-1α and G6PC are direct targets of miR-23a and demonstrated that their expressions are inversely related to miR-23a expression in human HCCs. Furthermore, miR-23a negatively regulates glucose production in mouse hepatocytes in culture. The miR-23a level was upregulated following treatment of hepatic cells with IL-6 and significantly reduced by phospho-Stat3 inhibitor or siRNA-mediated depletion of Stat3, demonstrating the involvement of IL-6 signaling pathway in miR-23a expression. Positive regulation of miR-23a expression by IL-6-Stat3 signaling was further confirmed by ChIP analysis and miR-23a promoter-luciferase assay. This study has convincingly demonstrated severe compromise of gluconeogenesis in hepatocellular carcinoma in both mouse HCC model and primary HCC and elucidated its mechanism involving IL-Stat3-mediated activation of miR-23a, resulting in hypoglycemia (supported, in part, by the grant CA 086978-10 from the National Institutes of Health). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5155. doi:1538-7445.AM2012-5155