The major DNA repair pathway after both proton and carbon-ion radiation is NHEJ, but the HR pathway is more relevant in carbon ions.
The major DNA repair pathway after both proton and carbon-ion radiation is NHEJ, but the HR pathway is more relevant in carbon ions.
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DOI：
10.1667/rr13904.1
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发表时间：
2015-03
影响因子：
3.4
通讯作者：
Tsuboi K
中科院分区：
文献类型：
--
作者：
Gerelchuluun A;Manabe E;Ishikawa T;Sun L;Itoh K;Sakae T;Suzuki K;Hirayama R;Asaithamby A;Chen DJ;Tsuboi K
本研究的目的是确定非同源末端连接 (NHEJ) 或同源重组 (HR) 途径在修复中国仓鼠细胞中暴露于高能质子和碳离子 (C 离子) 与伽马射线诱导的 DNA 双链断裂 (DSB) 中的作用。两种中国仓鼠细胞系，卵巢 AA8 和肺成纤维细胞 V79，以及缺乏 DNA-PKcs (V3)、X 射线修复交叉互补蛋白 4 [XRCC4 (XR1)、XRCC3 (irs1SF) 和 XRCC2 (irs1)] 的各种突变亚系暴露于伽马射线 (137Cs)、质子 (200 MeV; 2.2) keV/μm）和 C 离子（290 MeV；50 keV/μm）。 V3和XR1细胞缺乏NHEJ途径，而irs1和irs1SF细胞缺乏HR途径。每次暴露后，使用克隆存活测定法测量存活率，通过丝氨酸 139（γ-H2AX 焦点）处组蛋白 H2AX 磷酸化的免疫细胞化学分析评估原位 DSB 诱导，并使用固体染色检查染色体畸变。这项研究的结果表明，克隆存活显然取决于 NHEJ 和 HR 通路状态，并且 DNA-PKcs−/− 细胞 (V3) 对所有辐射类型最敏感。虽然质子和 γ 射线产生几乎相同的生物效应，但 C 离子暴露大大增强了野生型和 HR 缺陷细胞的敏感性。然而，对 NHEJ 缺陷细胞进行 C 离子照射后，没有观察到细胞杀伤敏感性的显着增强。在 NHEJ 缺陷细胞中，照射后 γ-H2AX 病灶数量的减少发生得更慢。特别是，V3 细胞在 C 离子照射后 24 小时时残留的 γ-H2AX 焦点数量最多。对于所有辐射类型的反应，NHEJ 和 HR 缺陷细胞系的染色体畸变均显着高于野生型细胞系。质子和伽马射线在每个细胞系中诱导相同的像差水平，而 C 离子引入更高但不显着不同的像差水平。我们的结果表明 NHEJ 通路在修复临床质子束和 C 离子束诱导的 DSB 中发挥着重要作用。此外，与伽马射线和质子相比，C 离子中的 HR 途径似乎更大程度地参与 DSB 的修复。
The purpose of this study was to identify the roles of non-homologous end-joining (NHEJ) or homologous recombination (HR) pathways in repairing DNA double-strand breaks (DSBs) induced by exposure to high-energy protons and carbon ions (C ions) versus gamma rays in Chinese hamster cells. Two Chinese hamster cell lines, ovary AA8 and lung fibroblast V79, as well as various mutant sublines lacking DNA-PKcs (V3), X-ray repair cross-complementing protein-4 [XRCC4 (XR1), XRCC3 (irs1SF) and XRCC2 (irs1)] were exposed to gamma rays (137Cs), protons (200 MeV; 2.2 keV/μm) and C ions (290 MeV; 50 keV/μm). V3 and XR1 cells lack the NHEJ pathway, whereas irs1 and irs1SF cells lack the HR pathway. After each exposure, survival was measured using a clonogenic survival assay, in situ DSB induction was evaluated by immunocytochemical analysis of histone H2AX phosphorylation at serine 139 (γ-H2AX foci) and chromosome aberrations were examined using solid staining. The findings from this study showed that clonogenic survival clearly depended on the NHEJ and HR pathway statuses, and that the DNA-PKcs−/− cells (V3) were the most sensitive to all radiation types. While protons and γ rays yielded almost the same biological effects, C-ion exposure greatly enhanced the sensitivity of wild-type and HR-deficient cells. However, no significant enhancement of sensitivity in cell killing was seen after C-ion irradiation of NHEJ deficient cells. Decreases in the number of γ-H2AX foci after irradiation occurred more slowly in the NHEJ deficient cells. In particular, V3 cells had the highest number of residual γ-H2AX foci at 24 h after C-ion irradiation. Chromosomal aberrations were significantly higher in both the NHEJ- and HR-deficient cell lines than in wild-type cell lines in response to all radiation types. Protons and gamma rays induced the same aberration levels in each cell line, whereas C ions introduced higher but not significantly different aberration levels. Our results suggest that the NHEJ pathway plays an important role in repairing DSBs induced by both clinical proton and C-ion beams. Furthermore, in C ions the HR pathway appears to be involved in the repair of DSBs to a greater extent compared to gamma rays and protons.