AIM:To study the relationship between the cyclooxy-genase(COX)-2 gene and the proliferation and apopto-sis of esophageal squamous carcinoma EC109 cells.METHODS:The techniques of RNA interference(RNAi)and cell transfection,as well as the levels of oncogenic-ity in nude mice,were used to study the role of COX-2 in the esophageal squamous carcinoma cell(ESCC)line EC109.Following RNAi and transfection,Western blot-ting analysis was used to determine the expression of the COX-2 protein.The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide(MTT)reduction assay was used to evaluate cell growth,and flow cytometry was used to detect cell apoptosis.RESULTS:Western blotting analysis demonstrated that COX-2 expression was significantly reduced in EC109 cells treated with COX-2-specif ic short interfering RNA(siRNA)but was increased in EC109 cells transfected with COX-2.Furthermore,COX-2 siRNA treatment in-hibited cell proliferation(P < 0.01)and induced apop-tosis in EC109 cells,as determined by an MTT assay and by flow cytometry,respectively.In contrast,trans-fected COX-2 led to increased cell proliferation(P < 0.05)and decreased apoptosis in EC109 cells.In addition,combination treatment of cells with COX-2 siRNA and aspirin had a synergistic effect(P < 0.01).For experi-ments measuring tumorigenicity,xenograft tumors of a greater volume and weight were found in the COX-2 group compared with other groups(P < 0.05).A large dose of aspirin inhibited tumor growth in nude mice ef-fectively(P < 0.05),and the rate of tumor suppression was 51.8% in the high-dose aspirin group.CONCLUSION:COX-2 plays a very critical role in ESCC carcinogenesis,and COX-2 siRNA combined with aspirin has the potential to be an anticancer therapy for the treatment of ESCC. AIM: To study the relationship between the cyclooxygenase (COX) -2 gene and the proliferation and apopto-sis of esophageal squamous carcinoma EC109 cells. METHODS: The techniques of RNA interference (RNAi) and cell transfection, as well as the levels of oncogenic-ity in nude mice, were used to study the role of COX-2 in the esophageal squamous carcinoma cell (ESCC) line EC 109. Folio RNAi and transfection, Western blot-ting analysis was used to determine the expression of the COX- 2 protein.The 3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyl-tetrazolium bromide (MTT) reduction assay was used to evaluate cell growth, and flow cytometry was used to detect cell apoptosis. Western blotting analysis demonstrated that COX-2 expression was significantly reduced in EC109 cells treated with COX-2-specif ic short interfering RNA (siRNA) but was increased in EC109 cells transfected with COX-2.Furthermore, COX-2 siRNA treatment in- hibited cell proliferation (P <0.01) and induced apoposis in EC109 cells, as deter Mined by an MTT assay and by flow cytometry, respectively. In contrast, trans-fected COX-2 led to increased cell proliferation (P <0.05) and decreased apoptosis in EC109 cells. In addition, combination treatment of cells with COX- 2 siRNA For experi-ments measuring tumorigenicity, xenograft tumors of a greater volume and weight were found in the COX-2 group compared with other groups (P <0.05). A large dose of aspirin inhibited tumor growth in nude mice ef-fectively (P <0.05), and the rate of tumor suppression was 51.8% in the high-dose aspirin group. CONCLUSION: COX-2 plays a very critical role in ESCC carcinogenesis, and COX-2 siRNA combined with aspirin has the potential to be an anticancer therapy for the treatment of ESCC.