Abstract: Objective To study the effects of TK adenovirus vector-Ad.HRE.CArG.HSV-TK regulated by hypoxia and radiation combined with radiotherapy on the growth of transplanted tumors of breast cancer Bcap37 in nude mice. Methods The models of transplanted tumors in BALB/C(nu/nu) nude mice were established by subcutaneous inoculation cells.When tumor diameter increased to 8~10mm,the mice were allocated to be control group,vector group（Ad）,radiation group(RT) and vector plus radiation group(Ad+RT).Day 1 was defined as treatment outset.On day 1 and day 5,0.2ml adenovirus vector was offered by tumor multi-point injection.The next day of injection,GCV(40mg/kg) was given using intraperitoneal injection,once on everyday for 14 days.X-ray irradiation of 2Gy was rendered on day 2,day 4 and day 6.The size of the tumor was measured every 3 days,and the volume of the tumor was calculated.After 30 days,the mice were killed,and the tumor was weighed and inhibition rate was calculated.HE staining and Annexin V detection were proceded to detect the apotosis of cancer cells in tumor tissues. Results The average volume and weight in experimental group were smaller than that in the control group（P<0.05）.Necrosis and apoptosis were observed from the HE staining tissue.The rate of apoptosis in experimental group was significantly higher than that in the control group（P<0.05）. ConclusionAdenovirus vector combined with radiotherapy had significant inhibition to the Bcap37 transplanted tumor in nude mice and induced cell.This provided the foundation for further gene radiation therapy of breast cancer.