Takahashi Akihisa, Matsumoto Hideki, Yuki Kazue, Yasumoto Jun-Ichi, Kajiwara Atsuhisa, Aoki Mizuho, Furusawa Yoshiya, Ohnishi Ken, Ohnishi Takeo
Department of Biology, Nara Medical University, Nara, Japan.
Int J Radiat Oncol Biol Phys. 2004 Oct 1;60(2):591-7. doi: 10.1016/j.ijrobp.2004.05.062.
We analyzed the death pattern of human lung cancer cells harboring different p53 statuses after irradiation with different levels of linear energy transfer (LET).
We used three kinds of human lung cancer cell lines with identical genotypes, except for the p53 gene. These cells were exposed to X-rays or accelerated carbon-ion beams. The cellular sensitivities were determined by a colony-forming assay. The detection and quantification of cell death (apoptosis and necrosis) were evaluated and compared by acridine orange/ethidium bromide double staining for fluorescence microscopy.
We found that (1) there was no significant difference in cellular sensitivity to LET radiation >70 KeV/microm, although wild-type p53 cell sensitivity to X-rays was higher than that of mutated p53 or p53-null cells; (2) low-LET radiation effectively induced apoptosis in wild-type p53 cells as compared with mutated p53 and p53-null cells; and (3) high-LET radiation induced p53-independent apoptosis.
Our findings suggest that high-LET radiotherapy is expected to be a valid application for patients carrying mutated p53 cancer cells. We proposed that the elucidation of the p53-independent apoptosis-related genes might provide new insights into radiotherapy for cancer.
我们分析了具有不同p53状态的人肺癌细胞在不同线性能量传递（LET）水平照射后的死亡模式。
我们使用了三种除p53基因外基因型相同的人肺癌细胞系。这些细胞暴露于X射线或加速碳离子束下。通过集落形成试验确定细胞敏感性。通过吖啶橙/溴化乙锭双重染色进行荧光显微镜检查来评估和比较细胞死亡（凋亡和坏死）的检测和定量。
我们发现：（1）尽管野生型p53细胞对X射线的敏感性高于突变型p53或p53缺失细胞，但对LET>70 KeV/μm的辐射，细胞敏感性没有显著差异；（2）与突变型p53和p53缺失细胞相比，低LET辐射能有效诱导野生型p53细胞凋亡；（3）高LET辐射诱导不依赖p53的凋亡。
我们的研究结果表明，高LET放射治疗有望成为携带突变型p53癌细胞患者的有效治疗方法。我们提出，阐明与p53无关的凋亡相关基因可能为癌症放射治疗提供新的见解。
