Objective To transfect antisense vector of human cyclooxygenase-2 （COX-2） gene into COX-2 highly expressing chol-angiocarcinoma cell line QBC939 and explore its biological activities and role in carcinogenesis. Methods QBC939 cells were transfected with antisense vector of human COX-2 gene using LipoVecTM transfecting te-chnique. Transfected cells were selected with G418; COX-2 mRNA was examined using reverse transcription polymerase chain reaction （RT-PCR） and COX-2 protein expression was detected by immunocytochemistry using isozyme selective anti-bodies. The proliferative status of transfected cells was measured by using methabenzthiazuron （MTT） assay; Cell cycle and apoptosis were analyzed by using flow cytometry. Results RT-PCR showed a lower COX-2 mRNA level in antisense vector transfected cells and immunocytochemistry showed a weaker COX-2 protein expression in antisense vector transfected cells. The antisense vector transfected cells proli-ferative index decreased significantly （P< 0.01）

the percentage of S phase decreased remarkably （P< 0.05） in antisense vec-tor transfected cells （9.27% ±1.91%） compared with that in QBC939 cells without transfection（16.35% ±2.87%）

and the percentage of G0/G1 phase increased remarkably （P< 0.05） in antisense vector transfected cells （75.16%±4.13%） compared with that in QBC939 cells without transfection （57.31% ±10.16%）. Transfection with antisense vector of human COX-2 gene had no significant influence on the apoptosis in QBC939 cells （P> 0.05）. Conclusion Transfection with antisense vector of human COX-2 gene could inhibit the proliferation of human cholan-giocarcinoma QBC939 cells.