Abstract: Objective To investigate antitumor effect of ergosterol and its mechanism in S180 tumor-bearing mice.Methods S180 tumor-bearing model was established in 50 mice(half male and female)and the mice were randomly divided into five groups(10 in each group):model group,cytoxan (CTX) group,high-,medium-,and low-dose ergosterol groups.The tumor inhibition rate in the mice of different groups was calculated 21 days after continuous treatment.Hematoxylin-eosin staining was used to observe proliferation of the tumors.The levels of superoxide dismutase(SOD),glutathion peroxidase(GSH-Px)and malondialdehyde(MDA) in liver tissues were evaluated.Western blot was used to determine the expression of survivin protein in tumors.Results Compared with the model group,the inhibitory rates of CTX group,high-,medium-,and low-dose ergosterol group were 53.96%,41.64%,29.90%,and 19.52%,with a statistically significant difference(P<0.05).Different extents of decreased capillaries and a variety of morphological apoptosis changes in tumor tissues were observed in the mice of ergosterol groups.Compared with the model group,the contents of SOD(69.19±12.18,66.30±8.80 U/mg prot) and GSH-Px(6982.69±1141.96,6414.43±932.96 U/mg prot)in the liver tissues of high-and medium-dose ergosterol groups were significantly increased(all P<0.05),while the content of MDA(24.59±6.87,31.43±7.05 nmol/mg prot)was significantly decreased(P<0.05).Compared with the model group,the expression level of survivin protein was significantly decreased(P<0.05)in tumors of the mice with high-and medium-dose ergosterol treatment.Conclusion Ergosterol has antitumor effect in S180 tumor-bearing mice and the mechanism of the effect may relate to the upregulation of antioxidant capacity in liver and downregulation of survivin protein expression in tumor.