Abstract: OBJECTIVE: To observe the anticancer effect of the serum thymic factor(FTS) 9 peptide on human colon cancer HT-29 transplantation model in nude mice. METHODS： Nude mice were inoculated subcutaneously with human colon cancer HT-29 cells，grouping was performed when tumor reach a volume of approximately 100 mm3. Tumor-bearing nude mice were divided into 5 groups：FTS 9 peptide high，medium and low dose group (1.25， 0.625，0.312 mg/kg，respectively)，positive control (cyclophosphamide，30 mg/kg) and blank control (saline)，10 mice in each group. Mice were treated subcutaneously once a day for 28 days. Body weight，length and width of tumor were measured twice a week. Mice were sacrificed 24 h after the last treatment，body weight，length，width，volume and weight of tumor were measured，the relative tumor proliferation and inhibition rates were calculated. Experiment was repeated 3 times. RESULTS：Relative tumor volumes of FTS 9 peptide groups were significantly reduced compared with blank control (P<0.01 or P<0.05)，relative tumor proliferation rates of FTS 9 peptide high，medium and low dose groups were 50%± 20%，62%±20% and 77% ± 35%， respectively. Tumor weights of FTS 9 peptide groups were significantly reduced compared with blank control (P<0.01)， inhibition rate of FTS 9 peptide high，medium and low doses group were 45% ± 3%，35% ± 1% and 27 %±3%， respectively. Body weights of nude mice in each group were not significantly different (compared with blank control，P>0.05). CONCLUSION：The results showed that the FTS 9 peptide had an obvious inhibitory effect on transplanted tumor of human colon cancer HT-29.

Key words: anticancer effect, serum thymic factor 9 peptide, human colon cancer HT-29, nude mice test