Estimation of Biologic and Molecular Aspects of Heavy Charged Particle Therapy for Cancer Cells

碳离子辐照对肿瘤具有良好的双重作用：由于尖锐的半影和剂量的远端拖尾而产生的有效剂量定位，以及由于高的相对生物效应（RBE）而产生的强生物抗癌效应。然而，碳离子辐照的生物学和分子机制尚未阐明。本研究主要探讨了碳离子辐照的生物学机制，特别是DNA双链断裂（DSB）及其修复的机制，并采用集落形成实验评价了X射线和碳离子辐照对细胞的杀伤作用。通过comat分析评估双链断裂量和修复率。在碳离子辐照和X射线辐照对DSB修复的比较中，碳离子辐照细胞的DSB残留程度较重。Westem blot分析DSB修复相关蛋白的表达水平。DNA修复蛋白Rad51的亚核定位通过epi进行化学标记 ...更多信息 荧光显微术。X射线照射和碳离子照射后，观察到Rad51核灶形成。这些核灶在用碳离子处理的细胞中持续到照射后24小时，而在用X射线照射处理的细胞中，超过一半的核灶在照射后24小时消失。Rad51反义寡核苷酸转染并用碳离子照射。转染后的克隆形成实验表明，Rad51反义寡核苷酸增加放射敏感性非常小的碳离子照射，而ti增加约1.7倍，在X射线照射。彗星试验也用于定量分析DSB诱导和修复。在经Rad51反义寡核苷酸处理的细胞中，与对照寡核苷酸相比，碳离子照射后DSB的诱导和修复率没有差异。这些结果可能表明，碳离子诱导的DSB很难通过同源重组修复。少

Carbon ion irradiation has well-balanced dual actions on cancers : efficient doselocalization due to sharp penumbra and distal taill off in dose, and potent biological anticancer effect due to high relative biological effect (RBE). However, biological and molecular mechanisms of carbon ion irradiation have not been clarified. In this study, we focused on the biologic mechanisms of carbon ion irradiation, especially assessing DNA double strand breaks (DSBs) and repair.Cell-killing effect of X-ray and carbon ion irradiation was assessed using a colony-formation assay. The amount of double strand breaks and repair rate was assessed by comat assay. In the comparison of DSBs repair between carbon ion irradiation and X-ray irradiation, the degree of residual DSBs was severe in carbon ion irradiated cells. The expression level of DSB repair associated protein was assessed by Westem blot analysis. Sub-nuclear localization of DNA repair protein Rad51 were immunohistochemically evaluated via epi … More tluorescence microscopy. Rad51 nuclear foci formation was observed after X-ray irradiation and carbon ion irradiation. These nuclear foci in the cells treated with carbon ion were sustained to 24 hours after irradiation, whereas in the cells treated with X-ray irradiation more than half of nuclear foci were disappeared at 24 hours after irradiation. Rad51 antisense oligonucleotides was transfected and irradiated with carbonions. Clonogenic assay after transfection revealed that Rad51 antisense oligonucleotides increased radiosensitivity very little carbon ion irradiation, whereas ti increased about 1.7 fold in X-irradiation. Comet assay was also performed for quantitative analysis of DSB induction and repair. There was no difference of DSB induction and repair rate after carbon ion irradiation in the cells treated with Rad51 antisense oligonucleotides and with control oligos. These results may suggest that carbon-ion-induced DSBs are difficult to be repaired by homologous recombination. Less