title: Inhibitors of hydroperoxide metabolism enhance ascorbate-induced cytotoxicity.
abstract: Pharmacological ascorbate, via its oxidation, has been proposed as a pro-drug for the delivery of H(2)O(2) to tumors. Pharmacological ascorbate decreases clonogenic survival of pancreatic cancer cells, which can be reversed by treatment with scavengers of H(2)O(2). The goal of this study was to determine if inhibitors of intracellular hydroperoxide detoxification could enhance the cytotoxic effects of ascorbate. Human pancreatic cancer cells were treated with ascorbate alone or in combination with inhibitors of hydroperoxide removal including the glutathione disulfide reductase inhibitor 1,3 bis (2-chloroethyl)-1-nitrosurea (BCNU), siRNA targeted to glutathione disulfide reductase (siGR), and 2-deoxy-D-glucose (2DG), which inhibits glucose metabolism. Changes in the intracellular concentration of H(2)O(2) were determined by analysis of the rate of aminotriazole-mediated inactivation of endogenous catalase activity. Pharmacological ascorbate increased intracellular H(2)O(2) and depleted intracellular glutathione. When inhibitors of H(2)O(2) metabolism were combined with pharmacological ascorbate the increase in intracellular H(2)O(2) was amplified and cytotoxicity was enhanced. We conclude that inclusion of agents that inhibit cellular peroxide removal produced by pharmacological ascorbate leads to changes in the intracellular redox state resulting in enhanced cytotoxicity.
authors.affiliation: Department of Radiation Oncology, University of Iowa , Iowa City, IA 52242, USA.
authors.forename: K E
authors.initials: KE
authors.lastname: Olney
authors.forename: J
authors.initials: J
authors.lastname: Du
authors.forename: T J
authors.initials: TJ
authors.lastname: van 't Erve
authors.forename: J R
authors.initials: JR
authors.lastname: Witmer
authors.forename: Z A
authors.initials: ZA
authors.lastname: Sibenaller
authors.forename: B A
authors.initials: BA
authors.lastname: Wagner
authors.forename: G R
authors.initials: GR
authors.lastname: Buettner
authors.forename: J J
authors.initials: JJ
authors.lastname: Cullen
mesh_terms: D000640:Amitrole / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology*; D002330:Carmustine / Q000494:pharmacology; D002374:Catalase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D055785:Gene Knockdown Techniques; D019803:Glutathione Disulfide / Q000378:metabolism; D005980:Glutathione Reductase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: D000970:Antineoplastic Agents; D034741:RNA, Small Interfering; D006861:Hydrogen Peroxide; D002374:Catalase; D005980:Glutathione Reductase; D001205:Ascorbic Acid; D002330:Carmustine; D019803:Glutathione Disulfide; D000640:Amitrole