The Defect of Ku70 Affects Sensitivity to X-Ray and Radiation-Induced Caspase-Dependent Apoptosis in Lung Cells
The Defect of Ku70 Affects Sensitivity to X-Ray and Radiation-Induced Caspase-Dependent Apoptosis in Lung Cells
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DOI：
10.1292/jvms.12-0333
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发表时间：
2013-04-01
影响因子：
1.2
通讯作者：
Koike, Aki
中科院分区：
文献类型：
--
作者：
Koike, Manabu;Yutoku, Yasutomo;Koike, Aki
DNA修复蛋白Ku70是对抗癌药物（如依托泊苷）或放射耐药的化学耐药的关键参与者。不同器官对辐射的反应差异很大，可能取决于器官中的细胞群。此前，我们建立并鉴定了Ku70缺陷小鼠肺上皮细胞（Ku70 -/- MLE），发现这些细胞比Ku70 +/- MLE细胞（对照细胞）对x射线更敏感，这是通过克隆生存试验确定的；然而，这种敏感性背后的机制尚不清楚。在这项研究中，我们研究了x射线照射引发Ku70 -/- MLE细胞死亡的机制。我们的研究结果表明，尽管x辐射激活了两种细胞系的caspase-3和caspase-7，并切割了PARP，但Ku70 -/- MLE细胞对辐射诱导的凋亡比对照细胞更敏感。我们还检测了磷酸化的H2AX （γ H2AX）的表达水平，这是DSB的标记物，并观察了x照射后两种细胞系中H2AX的磷酸化和γ H2AX的消除。Ku70 -/- MLE细胞中DSB的消除速度比对照细胞慢，表明Ku70 -/- MLE细胞中的DSB修复活性低于对照细胞。这些发现提示Ku70可能通过肺上皮细胞DSB修复通路在抑制细胞凋亡中发挥关键作用。我们的研究结果还表明，这些细胞系可能有助于研究肺上皮细胞中Ku70的功能和Ku70依赖的DSB修复途径。
The DNA repair protein Ku70 is a key player in chemoresistance to anticancer agents (e.g., etoposide) or radioresistance. The responses of different organs to radiation vary widely and likely depend on the cell population in the organs. Previously, we established and characterized Ku70-deficient murine lung epithelial (Ku70 -/- MLE) cells and found that these cells are more sensitive than Ku70 +/- MLE cells (control cells) to X-irradiation, as determined by clonogenic survival assay; however, the mechanism underlying this sensitivity remains unclear. In this study, we examined the mechanism by which X-irradiation triggers the death of Ku70 -/- MLE cells. Our results showed that Ku70 -/- MLE cells were more sensitive to radiation-induced apoptosis than control cells, although X-irradiation activated caspase-3 and caspase-7, and cleaved PARP in both cell lines. We also examined the expression level of phosphorylated H2AX (gamma H2AX), which is a marker of DSB, and observed the phosphorylation of H2AX and the elimination of gamma H2AX in both cell lines after X-irradiation. The elimination in Ku70 -/- MLE cells was slower than that in control cells, suggesting that DSB repair activity in the Ku70 -/- MLE cells is lower than that in control cells. These findings suggest that Ku70 might play a key role in the inhibition of apoptosis through the DSB repair pathway in lung epithelial cells. Our findings also suggest that these cell lines might be useful for the study of Ku70 functions and the Ku70-dependent DSB repair pathway in lung epithelial cells.