ObjectiveTo investigate the efficacy of 125 I in treatment of nude mice implanted with human glioma cell line U251 and the related mechanism.MethodsThe animal models of human malignant glioma were established with nude mice.125 I was implanted into tumors and the tumor growth was observed.The ultrastructural change was observed by electron microscopy.The apoptosis of the tumor tissue was examined by in situ end-labelling technique; expression of Bax/Bcl-2 was detected by flow cytometer.Blood vessel density and expression of VEGF,bFGF were observed by immunohistochemistry.ResultsNude mouse models of human malignant glioma were successfully established.Compared with control group,125 I significantly inhibited tumor growth in nude mice(P<0.05,P<0.01).Electron microscopy demonstrated that the tumor cells displayed apoptosis characteristics such as nuclear fragmentation,margination of condensed chromatin.The expression of Bax/Bcl-2 in the 125I implanting group (1.88±0.47)was significantly increased compared with that in the control group (1.11±0.52,P<0.01),and the apoptosis rate of tumor tissues in the 125I implanting group (3.64±0.89) was significantly higher(0.81±0.45,P<0.01).The blood vessel density in the 125I implanting group was significantly lower than that in the control group (1.40±0.55 vs 3.23±0.87,P<0.01).The expression of VEGF,bFGF in 125I implanting group was significantly lower than that in the control group (1.58±0.55 vs 4.19±0.45 for VEGF,P＜0.01; 2.44±0.89 vs 3.52±0.79 for bFGF,P<0.05).Conclusion125I has prominent inhibitory effect against human gliomas,and the main mechanism might be the promotion of apoptosis and decrease of blood vessel density.