Abstract: 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；D₁ group,75 mGy；D₂ group,4 Gy；D₁-12 h+D₂ group,the time between D₁ and D₂ was 12 h; D₁-24 h+D₂ group,the time between D₁ and D₂ was 24 h；D₁-48 h+D₂ group,the time between D₁ and D₂ was 48 h；D₁-72 h+D₂ group,the time between D₁ and D₂ 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)（P>0.05）.While in D₂ and D₁+D₂ 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（P＜0.01）.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.

Key words: glioma, mice, nud, apoptosis