OBJECTIVE To investigate the effect of clopidogrel(Clog),a platelet aggregation inhibitor,on the development of colitis-associated colon cancer(CAC)and its possible mechanism. METHODS To establish a CAC model,male BALB/c mice were treated with single azoxymethane(AOM) 10 mg · kg-1 by ip. One week later,the mice drank 2.5% dextran sulfate sodium(DSS)for one week and water for two weeks,which lasted three cycles. From the first day mice received 2.5%DSS water, Clog 12.5,25.0 and 50.0 mg · kg-1 was ig administered once a day. Body mass,clinical symptoms,the number of colon tumor and tumor size in colon tissue were recorded. Hyperplasia of tumors was analyzed by HE staining. In the early inflammatory phase of the CAC model,the length of colons was measured, histological structure and epithelium cell proliferation of colon tissues were evaluated by HE staining and Ki67 staining,respectively. In the tumorigenesis and progression phase of the CAC model,epithe?lium cell proliferation of colon tissues was evaluated by Ki67 staining. The mRNA expression of tumor necrosis factor-α(TNF-α)was detected by real-time quantitative PCR. The expression of chemokine(C-X-C motif)ligand 2(CXCL2)and its receptor 2(CXCR2)in colon tissues was detected by PCR and immu?nohistochemistry. RESULTS Compared with model group,clinical symptoms of mice in Clog 12.5 mg · kg-1 group were alleviated,the size of colon tumors was decreased(P<0.05),and hyperplasia of tumors was reduced(P<0.05). During the inflammatory phase,the clinical symptoms of mice in Clog 12.5 mg·kg-1 group were significantly alleviated(P<0.05),the decrease of body mass was reduced(P<0.01),the colon shrinkage was ameliorated(P<0.01),the inflammatory injury and epithelium cell proliferation in colon tissues were reduced(P<0.05). During the tumorigenesis and progression phase,epithelium cell prolif?eration in colon tissues in Clog 12.5 mg·kg-1 group was reduced(P<0.01),and the mRNA and protein expression of TNF-α,CXCL2 and CXCR2 of colon tissues was decreased(P<0.05). CONCLUSION Clog can alleviate inflammation during the CAC early inflammatory phase and inhibit the formation of CAC. The antitumor effect of Clog may be related to the decrease in expression of CXCL2 and CXCR2.