Abstract B97: Dichloroacetate (DCA) enhances activities of sorafenib against hepatocellular carcinoma (HCC) via modulation of aberrant cellular metabolism of HCC cells

Abstract

Abstract To meet high energy demand for proliferation, cancer cells rely more on aerobic glycolysis than on oxidative phosphorylation (OXPHOS). This aberrant cellular metabolism of cancer, well-known as the “Warburg effect”, may confer survival advantages and drug resistance to cancer cells. Pyruvate dehydrogenase (PDH) is the gatekeeper of OXPHOS, and is inhibited by pyruvate dehyrogenase kinase (PDK) through phosphorylation. Dichloroacetate (DCA), a synthetic PDK inhibitor, can reverse glycosis to OXPHOS through PDH activation, and has been used for the treatment of congenital lactic acidosis for more than 30 years. The present study explored whether modulating the Warburg effect by DCA can improve the efficacy of sorafenib (a multi-kinase inhibitor of Raf, VEGFR and PDGFR), the current standard systemic therapy for HCC. Modulation of the Warburg effect was evaluated by measurement of lactate in culture medium and PDH activity. In vitro growth-inhibitory effects were measured by median-effect analyses in a panel of human HCC cell-lines (Hep3B, Huh-7, Sk-hep1, HCC36 and HA22T) cultured in normoxic condition. In vivo growth-inhibitory effects were measured in both subcutaneous and orthotopic murine HCC xenograft models. Apoptosis was evaluated by flow cytometry (annexin V staining and subG1 fraction analysis) and the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Expression of apoptosis-related proteins was analyzed by Western blotting. We found that DCA reduced lactate production and increased PDH activity in HCC cells in a dose-dependent manner, indicating switching glucose metabolism from glycolysis to OXPHOS. DCA (10–60 mM) induced synergistic growth-inhibitory and apoptotic effects with sorafenib in most HCC cell-lines tested. Nude mice carrying subcutaneously or intrahepatically implanted Hep3B cells were treated with vehicle, DCA 100 mg/kg /day (equivalent to the dosage used to treat lactic acidosis in human), sorafenib 10 mg/kg /day, and DCA plus sorafenib, via gavage for 21 days. DCA-sorafenib combination synergistically suppressed the tumor growth without advertently affecting the body weight of mice. Synergistic induction of apoptosis was shown by TUNEL assay. Our data suggest that modulation of aberrant cellular metabolism of HCC cells by DCA may improve the clinical efficacy of sorafenib. (Supported by grants NSC97-3112-B-002-012, NSC98-3112-B-002-007, and NSC98-3112-B-002-037) Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B97.