Abstract: Objective: To study the inhibitory mechanism of polypeptide extract from scorpion venom (PESV) on W256 sarcocarcinoma and its influence on T subsets in rats. Methods: Tumor models were established by subcutaneously implanting W256 tumor cells into thirty Wistar rats. The tumor-bearing rats were randomly divided into three groups: the model group, the 5-fluorouracil(5-FU) group, and the PESV group. PESV was intragastrically subjected to the rats of the experimental group for 7 days. Then, the tumor-bearing rats were killed, and T subsets in the peripheral blood were determined by flow cytometry (FCM). The presence of interferon-gamma (INF-γ) and interleukin-4 (IL-4) were screened by an enzyme-linked immunosorbent assay (ELISA). Results： PESV had an inhibitory effect on tumor growth, and the growth inhibitory rate was 55.2%. The number of CD4+T and the CD4+T/CD8+T ratio of W256-bearing rats treated with PESV significantly increased compared with the model group (P＜0.05). The expression level of interferon-gamma (INF-γ) was up-regulated and of interleukin-4 (IL-4) down-regulated. Compared with the control group, the difference was significant(P＜0.05). Conclusion: PESV has an inhibitory effect on tumor growth by strengthening the immunocellular function. It could be regarded as a candidate of tumor inhibition.

Key words: Scorpion venom, Immunocompetence, CD4+T/CD8+T, Th1/Th2 shift