Objective: To study the effect and mechanism of arsenic trioxide (As2O3 ) with vitamin C(Vit C) on the subcutaneously transplanted tumor of drug resistant human lung tumors in nude mice. Method : The subcutaneously transplanted tumor models of drug resistant human lung tumors in nude mice were established and then were divided at random into 5 groups: NS

Vit C(250 mg ·kg-1)

As2O3 (1.5

3.0 mg ·kg-1)

and combining As2O3 with Vit C. They were injected intraperitoneally for two weeks. The weight of mice and volume of tumor pre- and post-administration were measured. All mice were killed after administration

and measured the mass of tumor and calculated the tumor inhibition. Tumor tissue was examined by pathological method. RT-PCR and Western blot were used to detect the vascular endothelial growth factor and survivin. Result : The tumor inhibitory rate of Vit C

As2O3 (1.5

3.0 mg ·kg-1)

and combining As2O3 with Vit C were 3.42％

42.3％

66.25％

79.93％ accordingly

and the volume

mass of tumor were decreased after treatment

in contrast to the saline group

the differences were significant (P<0.01). The tumor mass and volume were decreased in the test groups

more markedly in the combined drug group than single-drug groups. Moderate necrosis was found in tumor tissues.The expression of survivin mRNA and VEGF mRNA in the combination group was markedly lower than those in the other groups. The result of Western blot was also support RT-PCR's. Conclusion : Combined As2O3 and Vit C has stronger inhibition effect on tumor growth than single use of each drug

with a synergic anticancer effect on transplanted lung cancer in nude mice. Possible mechanism is related to the down-regulation of the expression of survivin and VEGF. Application of vitamin C and As2O3 might be a chemotherapy combination with low toxicity and efficient.