Objective To study the radiosensitization effect of Angelica-Radix Hedysari ultrafiltration membrane extract in TM40D human breast tumor-bearing mice and its possible mechanism.Methods Forty TM40D human breast tumor-bearing mice were randomized into the control group

drug group

radiation group and combination group

with 10 in each.The control group was gavaged with 0.3 ml / d of normal saline

drug group was gavaged with1.44 g / kg of Angelica-Radix Hedysari ultrafiltration membrane extract

radiation group was given a one-time 6Gy ray

and combination group was given 1.44 g / kg of Angelica-Radix Hedysari ultrafiltration membrane extract and a onetime 6Gy ray when the tumor volume in mice was 120mm3.The tumor weight

tumor-inhibition rate

tumor-growth delay（ TGD）

time required for tumor volume growth to 3 times as before radiation（ TGT3） and enhancement factor（ EF） in the combination group was observed after 30 days of administration.The expressions of p53 mRNA and its protein were detected.Results The tumor weight in the combination group was significantly lower than that in the control group

drug group and radiation group（ P < 0.05 or P < 0.01）.The tumor-inhibition rate in the combination group was significantly higher than that in the drug group and radiation group（ P < 0.01）.The TGT3 and TGD in the combination group was significantly increased as compared with the drug group and radiation group（ P < 0.05 or P <0.01）.The EF in the combination group was 1.95.The expressions of p53 mRNA and its protein in the combination group were significantly higher than those in the drug group and radiation group（ P < 0.05）.Conclusion Angelica-Radix Hedysari ultrafiltration membrane extract can enhance the radiosensitivity of TM40D human breast tumor-bearing mice probably by upregulating the expression of p53 mRNA and its protein.