Effect of low dose radiation on apoptosis of transplantation tumor cells of human glioma(U251)-bearing nude mice

Objective To study the effects of low dose radiation(LDR)on apoptosis of transplantation tumor cells of human glioma (U251)-bearing nude mice. Methods Thirty-five tumor-bearing nude mice were divided into seven groups(n=5):sham-irradiated group,0 mGy;D_1 group,75 mGy;D_2 group,4 Gy;D_1-12 h+D_2 group,the time between D_1 and D_2 was 12 h; D_1-24 h+D_2 group,the time between D_1 and D_2 was 24 h;D_1-48 h+D_2 group,the time between D_1 and D_2 was 48 h;D_1-72 h+D_2 group,the time between D_1 and D_2 was 72 h. The apoptosis of transplantation tumor cells of tumor(U251)- bearing nude mice was detected by TUNEL. Results There were TUNEL positive cells in all groups. The apoptotic index (AI) in 75 mGy group(0.19±0.07) was slightly increased, but the difference was not significant compared with sham-irradiated group(0.17±0.07)(P0.05). While in D_2 and D_1+D_2 groups, the AI (0.54±0.05,0.64±0.04,0.63±0.04,0.65±0.11, 0.67±0.07) were increased, and the latter was more obviously. There were significant differences compared with sham-irradiated group(P0.01). Conclusion LDR may promote apoptosis of transplantation tumor cells to some extent ,and could enhance high dose radiation to induce apoptosis of transplantation tumor cells.