Abstract: Objective To investigate CA Ⅸ and HIF-1α mRNA expression changes in tumor-bearing mice using anti-angiogenic drugs in conjunction with radiation therapy.To explore the possible mechanism of expression changes.Methods We established the model of Lewis lung carcinoma.32 tumor bearing mices which were randomly divided into blank control group,the Endostar group,the radiotherapy group and ES + RT group,respectirely.From the day of treatment,tumors were measured every other day.Then,we would describe the tumor growth curve.After treatment,we would peel the tumor,using Real-time PCR method to detect the expression of CA Ⅸ and HIF-1αmRNA in the treated tumor tissues.Results From tumor growth curves,the difference was statistically significant,between ES+ RT group and the remaining three groups(P＜0.05).As a reference to the blank group,CA Ⅸ mRNA amplification factor of the ES group,RT group and ES+RT group were decreased.ES + RT group of HIF-1α mRNA amplification factor was decreased.HIF-1αmRNA and CA Ⅸ mRNA expressions were positively correlated(r=0.68,P＜0.01).Conclusion Endostar combined with radiotherapy significantly inhibit the growth of mice with Lewis lung tumor;improving the status of tumor hypoxia.Inhibition of HIF-1α and CA Ⅸ mRNA expression may be one of the mechanisms of radiation sensitizing effect.