照射时间延长对小鼠LEWIS肺癌细胞杀伤作用影响

IMPACT OF PROLONGED RADIATION ON LEWIS LUNG CANCER CELLS IN MICE

目的模拟调强适形放射治疗(IMRT)模式,观察照射时间延长对小鼠LEWIS肺癌细胞杀伤作用的影响及凋亡相关基因蛋白Bcl-2、Bax表达的变化。方法荷LEWIS肺癌的C57BL/6雄性小鼠40只,随机分成假照组、常规照射组(A组)及IMRT模拟组(B1组、B2组)。按设计要求对各个照射剂量点进行照射,每个剂量点分5次照射,其间分别间隔7.0、10.5 min,照射后取出肿瘤,用末端标记法(TUNEL法)检测细胞凋亡指数,并采用免疫组化技术检测凋亡相关基因蛋白Bcl-2、Bax的表达水平。结果各组凋亡指数的差别有显著性(F=161.54,P<0.01),其中假照组的凋亡指数最低,A组的凋亡指数最高。各组间Bcl-2蛋白的半定量测定结果比较差别有统计学意义(F=737.40,P<0.01),其中假照组的Bcl-2蛋白含量最高,A组的含量最低。各组Bax蛋白的半定量测定结果比较差别有统计学意义(F=161.45,P<0.01),其中假照组的Bax蛋白含量最低。结论在一定的范围内,随着照射时间延长,小鼠LEWIS肺癌细胞Bax表达降低,而Bcl-2表达升高,凋亡指数下降。照射时间延长可导致高能X线对小鼠LEWIS肺癌细胞杀伤作用降低。

Objective To investigate the effects of prolonged fraction close-delivery time on LEWIS lung cancer cell apoptosis in mice. Methods LEWIS lung-cancer models were set up with C57BL/6 in 40 male mice, which were randomly divided into four groups： sham-irradiated group, conventional radiotherapy group （group A）, two IMRT mimicking groups （group B1, group B2） with different prolonged fraction delivery time for five times in 7.0-and 10. 5-min interval, and the tumours were then removed, the changes of apoptosis index （AI） and level of Bcl-2 were detected Using TUNEL and immunohistochemical staining. Results The differences of apoptosis index between different groups were statistically significant （P〈0. 01）. In sham-irradiated group, apoptosis index was the lowest, while in group A, the apoptosis index was the highest. Differences of the expression of Bcl- 2 protein between different groups had statistical significance （P〈0.01）. In sham-irradiated group, the expression of Bcl-2 protein was the lowest. Conclusion In definite extent, with the prolongation of irradiatation, the expression of Bax in LEWIS ceils declines, of Bcl-2 rises, and apoptosis decreases. Prolonged radiation may lead to decrease of killing efficiency of high-energy x-ray for LEWIS lung ceils in mice.