PURPOSE: Low-dose hyper-radiosensitivity (HRS) and the later appearing radioresistance (termed induced radioresistance [IRR]) was mainly studied in low linear energy transfer (LET) radiation with survival observation. The aim of this study was to find out whether equivalent hypersensitivity occurred in high LET radiation, and the roles of ataxia telangiectasia mutated (ATM) kinase. METHODS AND MATERIALS: Survival and mutation were measured by clonogenic assay and HPRT mutation assay. ATM Ser1981 activation was detected by Western blotting and immunofluorescent staining. Pretreatment of specific ATM inhibitor (10 microM KU55933) and activator (20 microg/mL chloroquine) before carbon radiation were adopted to explore the involvement of ATM. The roles of ATM were also investigated in its G2/M checkpoint function with histone H3 phosphorylation analysis and flow cytometric assay, and DNA double strand break (DSB) repair function measured using gamma-H2AX foci assay. RESULTS: HRS/IRR was observed with survival and mutation in normal human skin fibroblast cells by carbon ions, while impaired in cells with intrinsic ATM deficiency or normal cells modified with specific ATM activator or inhibitor before irradiation. The dose-response pattern of ATM kinase activation was concordant with the transition from HRS to IRR. The ATM-dependent "early" G2 checkpoint arrest and DNA DSB repair efficiency could explain the difference between HRS and IRR. CONCLUSIONS: These data demonstrate that the HRS/IRR by carbon ion radiation is an ATM-dependent phenomenon in the cellular response to DNA damage.
PURPOSE: Low-dose hyper-radiosensitivity (HRS) and the later appearing radioresistance (termed induced radioresistance [IRR]) was mainly studied in low linear energy transfer (LET) radiation with survival observation. The aim of this study was to find out whether equivalent hypersensitivity occurred in high LET radiation, and the roles of ataxia telangiectasia mutated (ATM) kinase. METHODS AND MATERIALS: Survival and mutation were measured by clonogenic assay and HPRT mutation assay. ATMSer1981 activation was detected by Western blotting and immunofluorescent staining. Pretreatment of specific ATM inhibitor (10 microM KU55933) and activator (20 microg/mL chloroquine) before carbon radiation were adopted to explore the involvement of ATM. The roles of ATM were also investigated in its G2/M checkpoint function with histone H3 phosphorylation analysis and flow cytometric assay, and DNA double strand break (DSB) repair function measured using gamma-H2AX foci assay. RESULTS:HRS/IRR was observed with survival and mutation in normal human skin fibroblast cells by carbon ions, while impaired in cells with intrinsic ATM deficiency or normal cells modified with specific ATM activator or inhibitor before irradiation. The dose-response pattern of ATM kinase activation was concordant with the transition from HRS to IRR. The ATM-dependent "early" G2 checkpoint arrest and DNA DSB repair efficiency could explain the difference between HRS and IRR. CONCLUSIONS: These data demonstrate that the HRS/IRR by carbon ion radiation is an ATM-dependent phenomenon in the cellular response to DNA damage.
Authors: Christopher D Sproul; Shangbang Rao; Joseph G Ibrahim; William K Kaufmann; Marila Cordeiro-Stone Journal: Cell Cycle Date: 2013-09-25 Impact factor: 4.534
Authors: Qin Zhou; Michelle E Howard; Xinyi Tu; Qian Zhu; Janet M Denbeigh; Nicholas B Remmes; Michael G Herman; Chris J Beltran; Jian Yuan; Patricia T Greipp; Judy C Boughey; Liewei Wang; Neil Johnson; Matthew P Goetz; Jann N Sarkaria; Zhenkun Lou; Robert W Mutter Journal: Cancer Res Date: 2021-02-17 Impact factor: 12.701