title: The apurinic/apyrimidinic endonuclease activity of Ape1/Ref-1 contributes to human glioma cell resistance to alkylating agents and is elevated by oxidative stress.
abstract: Alkylating agents are standard components of adjuvant chemotherapy for gliomas. We provide evidence here that Ape1/Ref-1, the major mammalian apurinic/apyrimidinic endonuclease (Ap endo), contributes to alkylating agent resistance in human glioma cells by incising DNA at abasic sites. We show that antisense oligonucleotides directed against Ape1/Ref-1 in SNB19, a human glioma cell line lacking O(6)-methylguanine-DNA-methyltransferase, mediate both reduction in Ape1/Ref-1 protein and Ap endo activity and concurrent reduction in resistance to methyl methanesulfonate and the clinical alkylators temozolomide and 1,3-(2-chloroethyl)-1-nitrosourea. An accompanying increase in the level of abasic sites indicates that the DNA repair activity of Ape1/Ref-1 contributes to resistance. Conversely, we also show that exposure of SNB19 cells to HOCl, a generator of reactive oxygen species (ROS), results in elevated Ape1/Ref-1 protein and Ap endo activity, enhanced alkylator resistance, and reduced levels of abasic sites. Given current evidence that heightened oxidative stress prevails within brain tumors, the finding that ROS increase resistance to clinical alkylators in glioma cells may have significance for the response of gliomas to alkylating agent-based chemotherapy. Our results may also be relevant to the design of therapeutic regimens using concurrent ionizing radiation (a generator of ROS) and alkylating agent-based chemotherapy.
authors.affiliation: Department of Neurological Surgery, University of Washington, Seattle, Washington 98195, USA. jrsilber@u.washington.edu
authors.forename: John R
authors.initials: JR
authors.lastname: Silber
authors.forename: Michael S
authors.initials: MS
authors.lastname: Bobola
authors.forename: A
authors.initials: A
authors.lastname: Blank
authors.forename: Kathryn D
authors.initials: KD
authors.lastname: Schoeler
authors.forename: Peter D
authors.initials: PD
authors.lastname: Haroldson
authors.forename: Mary B
authors.initials: MB
authors.lastname: Huynh
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Kolstoe
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D001080:Apurinic Acid / Q000032:analysis; D001932:Brain Neoplasms / Q000201:enzymology* / Q000473:pathology; D019757:Carbon-Oxygen Lyases / Q000096:biosynthesis / Q000502:physiology*; D002330:Carmustine / Q000494:pharmacology; D018736:DNA Adducts; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000032:analysis / Q000378:metabolism; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D004790:Enzyme Induction; D005909:Glioblastoma / Q000201:enzymology* / Q000473:pathology; D006801:Humans; D006997:Hypochlorous Acid / Q000494:pharmacology; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000172:deficiency / Q000502:physiology*; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000172:deficiency; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000494:pharmacology; D000077204:Temozolomide; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology
chemical_list: D018906:Antineoplastic Agents, Alkylating; D018736:DNA Adducts; D004273:DNA, Neoplasm; D009363:Neoplasm Proteins; D017382:Reactive Oxygen Species; D001080:Apurinic Acid; D006997:Hypochlorous Acid; D003606:Dacarbazine; D008741:Methyl Methanesulfonate; D019853:O(6)-Methylguanine-DNA Methyltransferase; D019757:Carbon-Oxygen Lyases; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D002330:Carmustine; D000077204:Temozolomide