title: Synergistic effects of ascorbate and sorafenib in hepatocellular carcinoma: New insights into ascorbate cytotoxicity.
abstract: We investigated the mechanism of selective ascorbate-induced cytotoxicity in tumor cells, including Hep G2 cells, compared to primary hepatocytes. H2O2 formation was required for ascorbate cytotoxicity, as extracellular catalase treatment protected tumor cells. H2O2 generated by glucose oxidase treatment also caused cell killing, but treatment with a pharmacologic dose (5-20mM) of ascorbate was significantly more cytotoxic at comparable rates of H2O2 production, suggesting that ascorbate enhanced H2O2 cytotoxicity. This was further supported by the finding that ascorbate at a non-cytotoxic dose (1mM) enhanced cell killing caused by glucose oxidase. Consistent with this conclusion, ascorbate treatment caused deregulation of cellular calcium homeostasis, resulting in massive mitochondrial calcium accumulation. Ascorbate acted synergistically with the chemotherapeutic sorafenib in killing Hep G2 cells, but not primary hepatocytes, suggesting adjuvant ascorbate treatment can broaden sorafenib's therapeutic range. Sorafenib caused mitochondrial depolarization and prevented mitochondrial calcium sequestration. Subsequent ascorbate addition further deregulated cellular calcium homeostasis promoting cell death. Additionally, we present the case of a patient with hepatocellular carcinoma (HCC) who had prolonged regression of a rib metastasis upon combination treatment with ascorbate and sorafenib, indicating that these studies have direct clinical relevance.
authors.affiliation: MitoCare Center, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Lauren
authors.initials: L
authors.lastname: Rouleau
authors.affiliation: MitoCare Center, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Anil Noronha
authors.initials: AN
authors.lastname: Antony
authors.affiliation: MitoCare Center, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Sara
authors.initials: S
authors.lastname: Bisetto
authors.affiliation: Jefferson-Myrna Brind Center of Integrative Medicine, Thomas Jefferson University Hospital, Philadelphia, PA 19107, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Newberg
authors.affiliation: Division of Transplantation, Liver Tumor Center, Thomas Jefferson University Hospital, Philadelphia, PA 19107, USA.
authors.forename: Cataldo
authors.initials: C
authors.lastname: Doria
authors.affiliation: Molecular and Clinical Nutrition Section, Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Levine
authors.affiliation: Jefferson-Myrna Brind Center of Integrative Medicine, Thomas Jefferson University Hospital, Philadelphia, PA 19107, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Monti
authors.affiliation: MitoCare Center, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Jan B
authors.initials: JB
authors.lastname: Hoek
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001205:Ascorbic Acid / Q000008:administration & dosage*; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D004357:Drug Synergism; D056945:Hep G2 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009536:Niacinamide / Q000008:administration & dosage / Q000031:analogs & derivatives*; D010671:Phenylurea Compounds / Q000008:administration & dosage*; D000077157:Sorafenib
chemical_list: D010671:Phenylurea Compounds; D009536:Niacinamide; D000077157:Sorafenib; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid
keywords: Ascorbate; Calcium homeostasis; Glucose oxidase; Hep G2; Hepatocellular carcinoma; Hydrogen peroxide; Mitochondrial membrane potential; Sorafenib; Synergy; Vitamin C