BACKGROUND Radiation is an important therapeutic tool. However, radiotherapy has the potential to promote co-evolution of genetic and epigenetic changes that can drive tumour heterogeneity, formation of radioresistant cells and tumour relapse. There is a clinical need for a better understanding of DNA methylation alterations that may follow radiotherapy to be able to prevent the development of radiation-resistant cells. METHODS We examined radiation-induced changes in DNA methylation profiles of paediatric glioma stem cells (GSCs) in vitro. Five GSC cultures were irradiated in vitro with repeated doses of 2 or 4 Gy. Radiation was given in 3 or 15 fractions. DNA methylation profiling using Illumina DNA methylation arrays was performed at 14 days post-radiation. The cellular characteristics were studied in parallel. RESULTS Few fractions of radiation did not result in significant accumulation of DNA methylation alterations. However, extended dose fractionations changed DNA methylation profiles and induced thousands of differentially methylated positions, specifically in enhancer regions, sites involved in alternative splicing and in repetitive regions. Radiation induced dose-dependent morphological and proliferative alterations of the cells as a consequence of the radiation exposure. CONCLUSIONS DNA methylation alterations of sites with regulatory functions in proliferation and differentiation were identified, which may reflect cellular response to radiation stress through epigenetic reprogramming and differentiation cues.

中文翻译：

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分次剂量照射后小儿神经胶质瘤干细胞中DNA甲基化变化的积累。

背景技术放射线是重要的治疗工具。然而，放疗具有促进遗传和表观遗传学变化共同发展的潜力，这些变化可以驱动肿瘤异质性，放射抗性细胞的形成和肿瘤复发。临床上需要更好地理解放射治疗后DNA甲基化的改变，从而能够防止抗辐射细胞的发育。方法我们研究了辐射诱导的儿童神经胶质瘤干细胞（GSC）DNA甲基化谱的变化。在体外以重复剂量2或4 Gy辐照了五种GSC培养物。辐射分为3或15个部分。放射后14天使用Illumina DNA甲基化阵列进行DNA甲基化分析。并行研究细胞特性。结果很少部分辐射不会导致DNA甲基化改变的大量积累。然而，延长剂量分级改变了DNA甲基化分布并诱导了数千个差异甲基化位置，特别是在增强子区域，替代剪接和重复区域中。辐射引起细胞辐射的剂量依赖性形态和增殖变化。结论鉴定了在增殖和分化中具有调控功能的位点的DNA甲基化改变，这可能反映了通过表观遗传重编程和分化提示细胞对辐射胁迫的反应。延长剂量分级改变了DNA甲基化谱并诱导了成千上万的差异甲基化位置，特别是在增强子区域，参与可变剪接的位点和重复区域。辐射引起细胞辐射的剂量依赖性形态和增殖变化。结论鉴定了在增殖和分化中具有调控功能的位点的DNA甲基化改变，这可能反映了通过表观遗传重编程和分化提示细胞对辐射胁迫的反应。延长剂量分级改变了DNA甲基化谱并诱导了成千上万的差异甲基化位置，特别是在增强子区域，参与可变剪接的位点和重复区域。辐射引起细胞辐射的剂量依赖性形态和增殖变化。结论鉴定了在增殖和分化中具有调控功能的位点的DNA甲基化改变，这可能反映了通过表观遗传重编程和分化提示细胞对辐射胁迫的反应。辐射引起细胞辐射的剂量依赖性形态和增殖变化。结论鉴定了在增殖和分化中具有调控功能的位点的DNA甲基化改变，这可能反映了通过表观遗传重编程和分化提示细胞对辐射胁迫的反应。辐射引起细胞辐射的剂量依赖性形态和增殖变化。结论鉴定了在增殖和分化中具有调控功能的位点的DNA甲基化改变，这可能反映了通过表观遗传重编程和分化提示细胞对辐射胁迫的反应。