Abstract: To explore the effects of arsenic trioxide on radiosensitivity and the possible mechanism in lung cancer xenografts. METHODS: The tumor-bearing C57BL/6 mouse model was established by injecting Lewis lung cancer cells into right infra-axillary dermis. 40 mice were randomized into 4 groups: control group(peritoneal injection 0.9％NS,0.2 ml); As2O3 group(peritoneal injection,2.0 mg/kg,0.2 ml As2O3); irradiation group(peritoneal injection 0.9％NS,0.2 ml＋6MeV Electron Beam,10 Gy); As2O3＋irradiation group(peritoneal injection, 2.0 mg/kg, 0.2 ml As2O3＋6MeV Electron Beam,10 Gy). After experiments, mice were sacrificed, then the tumors were separated and weighed. Response to irradiation was evaluated by tumor- inhibiting rate. The expressions of VEGF and Ku70 mRNA were evaluated by RT-PCR. The protein levels of VEGF and Ku70 were measured by immunohistochemical staining. RESULTS: The Lewis lung cancer-bearing model was successfully established in mice. As2O3＋irradiation could significantly increase the tumor-inhibiting rate and downregulate the expression of VEGF and Ku70 of irradiated carcinoma xenografts, (Compared with As2O3 group or irradiation group, P＜0.05). CONCLUSION: Arsenic trioxide could sensitize lung cancer xenografts to ionizing irradiation. This effect was probably mediated by downregulating the expressions of VEGF and Ku70.

Key words: arsenic trioxide, lung cancer, radiosensitivity