Background and purpose: Thalidomide can enhance the radiation sensitivity on tumor effectively

but the mechanism of radiosensitization is still unclear. The present study aimed to investigate whether thalidomide could enhance the radiation sensitivity on colon cancer transplanted tumor of mouse

and to investigate the underlying mechanism. Methods: We established the model of colon26 colonic carcinoma

and the mice were divided into 4 groups: Control group

the thalidomide group

the radiotherapy group and thalidomide+radiotherapy group. From the day of treatment

tumors were measured every other day. Then

the xenograft tumor growth curve was depicted. Tumor volumes were measured in different treatment groups

then

the inhibitory rates of tumor growth were calcutated. Using immunohistochemical method in to detect the expression of microvessel density (MVD) in tumor tissue. Results: The mean tumor volumes at day 22 were (4.97±1.20)cm3 (control group)

(2.90±0.92)cm3 (T group)

(2.66±0.88)cm3 (R group)

and (1.89±0.76)cm3 (T+R group). The tumor inhibition rate in the combination group (61.9%) was significantly higher than the other groups (41.7%

46.5%

P0.05). The radiotherapy sensitization enhancement ratio of the combined treatment group was 2.27 times than in the radiotherapy group. Thalidomide combined with radiation therapy can significantly inhibit microvessel density of tumor: The decreasing MVD of T+R group

T group and R group were respectively 46.8%

40.7% and 37.7%

and there was statistical significance between T+R group and T group (P0.05 )

so as between T+R group and R group. It could be found more necrotic cells in tumor of group

and there was statistical significance between T+R group and control group (P0.05). Conclusion: Thalidomide can enhance the radiosensitivity mice of colonic carcinoma

and its mechanism may be related to the inhibition of tumor angiogenesis related.