Xue Lian, Yu Dong, Furusawa Yoshiya, Cao Jianping, Okayasu Ryuichi, Fan Saijun
School of Radiation Medicine and Public Health, Medical College of Soochow University, Suzhou, China.
Int J Radiat Oncol Biol Phys. 2009 Sep 1;75(1):235-43. doi: 10.1016/j.ijrobp.2009.04.088.
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.
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.
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.
These data demonstrate that the HRS/IRR by carbon ion radiation is an ATM-dependent phenomenon in the cellular response to DNA damage.
低剂量超放射敏感性（HRS）以及随后出现的放射抗性（称为诱导放射抗性[IRR]）主要是在低线性能量转移（LET）辐射下通过存活观察进行研究的。本研究的目的是探究在高LET辐射中是否会出现等效的超敏感性，以及共济失调毛细血管扩张突变（ATM）激酶的作用。
通过克隆形成试验和次黄嘌呤-氨基蝶呤-胸腺嘧啶核苷（HPRT）突变试验测量细胞存活和突变情况。通过蛋白质免疫印迹法和免疫荧光染色检测ATM Ser1981的激活情况。在碳离子辐射前采用特异性ATM抑制剂（10微摩尔/升KU55933）和激活剂（20微克/毫升氯喹）进行预处理，以探究ATM的参与情况。还通过组蛋白H3磷酸化分析和流式细胞术检测ATM在其G2/M期检查点功能中的作用，并使用γ-H2AX焦点试验测量DNA双链断裂（DSB）修复功能。
在正常人皮肤成纤维细胞中，通过碳离子辐射观察到了HRS/IRR现象，而在具有内在ATM缺陷的细胞或在辐射前用特异性ATM激活剂或抑制剂处理的正常细胞中，该现象受到损害。ATM激酶激活的剂量反应模式与从HRS到IRR的转变一致。ATM依赖性的“早期”G2期检查点停滞和DNA DSB修复效率可以解释HRS和IRR之间的差异。
这些数据表明，碳离子辐射引起的HRS/IRR是细胞对DNA损伤反应中一种依赖ATM的现象。
