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目的：研究及探讨快中子及X射线诱导人直肠癌细胞凋亡及其相关基因表达。方法：不同剂量X射线（0、2、4、6、8、10Gy）及具有同等放射生物学效应的相当于X射线1／3剂量的不同剂量快中子（0、0．67、1．34、2．01、2．68、3．34Gy）照射细胞，于37℃孵育6小时24小时48小时72小时后，进行Hoechest 33 342荧光染色，观察细胞凋亡形态并计数凋亡指数AI（凋亡细胞的百分数）；用电子显微镜观察凋亡细胞特有的形态学特征；此外，我们分别对不同剂量（0、2、4、6、8、10Gy） X射线及快中子（0、0．67、1．34、2．01、2．68、3．34Gy）照射后24小时的细胞用免疫组化方法进行基因表达（p53及bcl－2）的检测。结果：不同剂量X射线和快中子照射的细胞凋亡指数随着照射剂量和受照时间的延长而逐渐增加，在同一时间点，快中子诱导的细胞凋亡水平明显高于X射线；不同剂量X射线照射后的细胞，较阳性对照组，p53基因表达下调明显，bcl－2基因表达下调不明显；不同剂量快中子照射后的细胞，p53及bcl－2基因表达下调均不明显。结论：高能X射线和快中子诱导人直肠癌细胞的凋亡具有明确的时间－剂量相关性，随着受照后时间的延长和剂量的逐渐增大，凋亡指数渐趋升高，无明显变缓之势；快中子照射人直肠癌细胞，与X射
Objective: To study and explore the apoptosis of human rectal cancer cells induced by fast neutrons and X-rays and their related gene expression. Methods: Different doses of X-rays (0, 2, 4, 6, 8, 10 Gy) and equivalent radiobiological effects were equivalent to X-ray 1/3 doses of different doses of fast neutrons (0, 0.67, 1. 34, 2.01, 2.68, 3.34 Gy) irradiated cells, incubated at 37 °C for 6 hours, 24 hours, 48 hours, 72 hours, followed by Hoechst 33 342 fluorescence staining to observe the apoptotic morphology and count apoptosis. Index AI (percentage of apoptotic cells); electron microscopic observation of the characteristic morphological features of apoptotic cells; in addition, we used different doses (0, 2, 4, 6, 8, 10 Gy) of X-rays and fast neutrons ( Cells at 0, 0.67, 1.34, 2.01, 2.68, 3.34 Gy) 24 h after irradiation were tested for gene expression (p53 and bcl-2) by immunohistochemistry. RESULTS: Apoptosis index of different doses of X-rays and fast neutrons increased gradually with the irradiation dose and exposure time. At the same time point, the apoptosis induced by fast neutrons was significantly higher than that of X-rays. Different doses of X-irradiated cells, compared with the positive control group, p53 gene expression was down-regulated, bcl-2 gene expression was down-regulated; cells after different doses of fast neutron irradiation, p53 and bcl-2 gene expression were not down-regulated obvious. Conclusion: The apoptosis of human rectal cancer cells induced by high-energy X-rays and fast neutrons has a definite time-dose correlation. With the prolongation of exposure time and the gradual increase of dose, the apoptotic index gradually increases. Significantly slowed down; fast neutrons illuminate human rectal cancer cells, and X-rays