title: Mitochondria-targeted antioxidant and glycolysis inhibition: synergistic therapy in hepatocellular carcinoma.
abstract: Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide. Mito-carboxy proxyl (Mito-CP), a lipophilic cationic nitroxide, accumulates in the mitochondria because of the large negative transmembrane potential. Studies have shown that these agents act by disrupting the energy-producing mechanism, inducing mitochondrial-mediated apoptosis, and also enhancing the action of other chemotherapeutic agents in cancer cells. We hypothesized that the combination of Mito-CP and glycolysis inhibitor, 2-deoxyglucose (2-DG), would synergistically inhibit HCC in vitro. HepG2 cells and primary hepatocytes were treated with various combinations of Mito-CP and 2-DG. Cell cytotoxicity was measured using the methylthiazolyldiphenyl-tetrazolium bromide assay and ATP bioluminescence assay. In addition, caspase 3/7 enzymatic activity was examined after treatment. Mito-CP and 2-DG induced synergistic cytotoxicity in HepG2 cells in a dose-dependent and time-dependent manner, whereas primary cells remained viable and unaffected after treatment. The intracellular ATP levels of HepG2 cells were suppressed within 6 h of combination treatment, whereas primary cells maintained higher levels of ATP. Dose-dependent increases in caspase 3/7 activity occurred in HepG2 cells in a time-dependent manner, showing the initiation of cell death through the apoptotic pathway. These findings indicate that a combination of Mito-CP and 2-DG effectively inhibits HCC growth in vitro. The increase in caspase 3/7 activity supports the occurrence of 2-DG-induced and Mito-CP-induced apoptotic death in HCC. The inability of the compounds to induce cytotoxicity or suppress the production of ATP in primary hepatocytes provides a selective and synergistic approach for the treatment of HCC.
authors.affiliation: Department of Surgery, Division of Surgical Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors.forename: Archana
authors.initials: A
authors.lastname: Dilip
authors.forename: Gang
authors.initials: G
authors.lastname: Cheng
authors.forename: Joy
authors.initials: J
authors.lastname: Joseph
authors.forename: Selvi
authors.initials: S
authors.lastname: Kunnimalaiyaan
authors.forename: Balaraman
authors.initials: B
authors.lastname: Kalyanaraman
authors.forename: Muthusamy
authors.initials: M
authors.lastname: Kunnimalaiyaan
authors.forename: Thomas Clark
authors.initials: TC
authors.lastname: Gamblin
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000970:Antineoplastic Agents / Q000009:adverse effects / Q000494:pharmacology*; D000975:Antioxidants / Q000009:adverse effects / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003497:Cyclic N-Oxides / Q000009:adverse effects / Q000494:pharmacology; D003847:Deoxyglucose / Q000009:adverse effects / Q000494:pharmacology; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000009:adverse effects / Q000494:pharmacology*; D006019:Glycolysis / Q000187:drug effects*; D056945:Hep G2 Cells; D006801:Humans; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D058990:Molecular Targeted Therapy; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000009:adverse effects / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D000975:Antioxidants; D003497:Cyclic N-Oxides; D004791:Enzyme Inhibitors; D009363:Neoplasm Proteins; D009943:Organophosphorus Compounds; C571715:mito-carboxy proxyl; D000255:Adenosine Triphosphate; D003847:Deoxyglucose