title: Overexpression of isocitrate dehydrogenase mutant proteins renders glioma cells more sensitive to radiation.
abstract: Mutations in isocitrate dehydrogenase 1 (IDH1) or 2 (IDH2) are found in a subset of gliomas. Among the many phenotypic differences between mutant and wild-type IDH1/2 gliomas, the most salient is that IDH1/2 mutant glioma patients demonstrate markedly improved survival compared with IDH1/2 wild-type glioma patients. To address the mechanism underlying the superior clinical outcome of IDH1/2 mutant glioma patients, we investigated whether overexpression of the IDH1(R132H) protein could affect response to therapy in the context of an isogenic glioma cell background. Stable clonal U87MG and U373MG cell lines overexpressing IDH1(WT) and IDH1(R132H) were generated, as well as U87MG cell lines overexpressing IDH2(WT) and IDH2(R172K). In vitro experiments were conducted to characterize baseline growth and migration and response to radiation and temozolomide. In addition, reactive oxygen species (ROS) levels were measured under various conditions. U87MG-IDH1(R132H) cells, U373MG-IDH1(R132H) cells, and U87MG-IDH2(R172K) cells demonstrated increased sensitivity to radiation but not to temozolomide. Radiosensitization of U87MG-IDH1(R132H) cells was accompanied by increased apoptosis and accentuated ROS generation, and this effect was abrogated by the presence of the ROS scavenger N-acetyl-cysteine. Interestingly, U87MG-IDH1(R132H) cells also displayed decreased growth at higher cell density and in soft agar, as well as decreased migration. Overexpression of IDH1(R132H) and IDH2(R172K) mutant protein in glioblastoma cells resulted in increased radiation sensitivity and altered ROS metabolism and suppression of growth and migration in vitro. These findings provide insight into possible mechanisms contributing to the improved outcomes observed in patients with IDH1/2 mutant gliomas.
authors.affiliation: Department of Neurology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, Los Angeles, California 90095, USA.
authors.forename: Sichen
authors.initials: S
authors.lastname: Li
authors.forename: Arthur P
authors.initials: AP
authors.lastname: Chou
authors.forename: Weidong
authors.initials: W
authors.lastname: Chen
authors.forename: Ruihuan
authors.initials: R
authors.lastname: Chen
authors.forename: Yuzhong
authors.initials: Y
authors.lastname: Deng
authors.forename: Heidi S
authors.initials: HS
authors.lastname: Phillips
authors.forename: Julia
authors.initials: J
authors.lastname: Selfridge
authors.forename: Mira
authors.initials: M
authors.lastname: Zurayk
authors.forename: Jerry J
authors.initials: JJ
authors.lastname: Lou
authors.forename: Richard G
authors.initials: RG
authors.lastname: Everson
authors.forename: Kuan-Chung
authors.initials: KC
authors.lastname: Wu
authors.forename: Kym F
authors.initials: KF
authors.lastname: Faull
authors.forename: Timothy
authors.initials: T
authors.lastname: Cloughesy
authors.forename: Linda M
authors.initials: LM
authors.lastname: Liau
authors.forename: Albert
authors.initials: A
authors.lastname: Lai
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D002448:Cell Adhesion; D002465:Cell Movement; D049109:Cell Proliferation; D003606:Dacarbazine / Q000031:analogs & derivatives / Q000494:pharmacology; D060733:Electromagnetic Radiation; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects; D005910:Glioma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D007521:Isocitrate Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D050505:Mutant Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D011836:Radiation Tolerance / Q000235:genetics*; D017382:Reactive Oxygen Species / Q000378:metabolism; D000077204:Temozolomide; D014407:Tumor Cells, Cultured
chemical_list: D018906:Antineoplastic Agents, Alkylating; D050505:Mutant Proteins; D017382:Reactive Oxygen Species; D003606:Dacarbazine; C538784:IDH2 protein, human; D007521:Isocitrate Dehydrogenase; C543588:IDH1 protein, human; D000077204:Temozolomide