Objective To explore the effects and possible mechanisms of Qizhu Kangai Formula（芪术抗癌方） on colon carcinoma. Methods A total of 90 male BALB/c mice were randomly divided into a blank group

a model group

a 5-fluorouracil（5-Fu） group

Qizhu Kangai Formula high

medium and low dose group

combined high

medium and low dose group

with 10 mice in each group. Except for the blank group

CT26.WT colon cancer orthotopic transplantation models of mice were established. Twenty-four hours after operation

the blank group and the model group were given 10 ml/（kg·d） of normal saline for gavage; the 5-Fu group was given intraperitoneal injection of 5-fluorouracil 25 mg/（kg·d） once every other day; Qizhu Kangai Formula high-dose

medium-dose

and low-dose groups were fed with Qizhu Kangai Fang 24

12

6 g/（kg·d） liquid solution once a day; Combined high-dose

middle-dose

and low-dose groups

were administered the corresponding doses of Qizhu Kangai Fang and 5-fluorouracil intraperitoneally. The dosages and methods were the same as above. Three weeks after intervention

the mice in all groups were killed and tumor tissues were taken to weigh and calculate the tumor inhibition rate; Caspase-3 and B lymphoma 2（Bcl-2） and blymphoma2 related Bax protein（Bax） and mRNA expression in each group were detected. Results Compared with the model group

the tumor mass weight of the mice in other groups decreased（P<0.01）; the combined high-dose group had the highest tumor inhibition rate

reaching 82.700%. All administration groups up-regulated the expression of Caspase-3

Bax protein and mRNA in tumor tissue to varying degree

while the expression of Bcl-2 protein and mRNA was down-regulated. The inhibition and regulation effect of Qizhu Kangai Formula and combination with 5-fluorouracil on Caspase-3

Bax

Bcl-2 protein and mRNA expression was dose-dependent（P<0.05 or P<0.01）. Conclusion Qizhu Kangai Formula could inhibit the proliferation of CT26.WT orthotopic transplanted tumors

and it has a synergistic effects with 5-Fu. The mechanisms may be related to up-regulation of Caspase-3 and Bax expression and down-regulation of Bcl-2 expression in tumor tissues.