title: Induction of radioresistance by a nitric oxide-mediated bystander effect.
abstract: To elucidate whether nitric oxide secreted from irradiated cells affects cellular radiosensitivity, we examined the accumulation of inducible nitric oxide synthase, TP53 and HSP72, the concentration of nitrite in the medium of cells after X irradiation, and cellular radiosensitivity using two human glioblastoma cell lines, A-172, which has a wild-type TP53 gene, and a transfectant of A-172 cells, A-172/mp53, bearing a mutated TP53 gene. Accumulation of inducible nitric oxide synthase was caused by X irradiation of the mutant TP53 cells but not of the wild-type TP53 cells. Accumulation of TP53 and HSP72 in the wild-type TP53 cells was observed by cocultivation with irradiated mutant TP53 cells, and the accumulation was abolished by the addition of an inhibitor for inducible nitric oxide synthase, aminoguanidine, to the medium. Likewise, accumulation of these proteins was observed in the wild-type TP53 cells after exposure to conditioned medium from irradiated mutant TP53 cells, and the accumulation was abolished by the addition of a specific nitric oxide scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide, to the medium. The radiosensitivity of wild-type TP53 cells was reduced when the cells were cultured in conditioned medium from irradiated mutant TP53 cells compared to conventional fresh growth medium. Collectively, these findings indicate the potential importance of an intercellular signal transduction pathway initiated by nitric oxide in the cellular response to ionizing radiation.
authors.affiliation: Department of Experimental Radiology and Health Physics, Fukui Medical University, Matsuoka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Matsumoto
authors.forename: S
authors.initials: S
authors.lastname: Hayashi
authors.forename: M
authors.initials: M
authors.lastname: Hatashita
authors.forename: K
authors.initials: K
authors.lastname: Ohnishi
authors.forename: H
authors.initials: H
authors.lastname: Shioura
authors.forename: T
authors.initials: T
authors.lastname: Ohtsubo
authors.forename: R
authors.initials: R
authors.lastname: Kitai
authors.forename: T
authors.initials: T
authors.lastname: Ohnishi
authors.forename: E
authors.initials: E
authors.lastname: Kano
mesh_terms: D002460:Cell Line; D018920:Coculture Techniques; D017077:Culture Media, Conditioned; D050884:HSP72 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D009569:Nitric Oxide / Q000096:biosynthesis / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011836:Radiation Tolerance / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014965:X-Rays
chemical_list: D017077:Culture Media, Conditioned; D050884:HSP72 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D020030:Nitric Oxide Donors; C110881:S-nitro-N-acetylpenicillamine; D016159:Tumor Suppressor Protein p53; D009569:Nitric Oxide; D010396:Penicillamine