【Abstract】Objective To investigate the effects of selective cyclooxygenase-2 (COX-2) inhibitor nimesulide on the proliferation of colon adenocarcinoma cells in vitro and the expression of matrix metalloproteinase-2 (MMP-2). Methods The human colon cancer cell lines HT-29 and HCT-116 were employed in the study, grouped as nimesulide group, DMSO control group and blank control group. After treatment with nimesulide, the inhibitory effect of nimesulide on the proliferation of cancer cells was quantified by MTT assay, and the expression of MMP-2 in the cells was detected by quantitative zymography. Results Nimesulide inhibited the proliferation of HT-29 and HCT-116 cells in time and dosedependent manners. The inhibitory effect on HT-29 cells was ber than that on HCT-116 cells. Nimesulide downregulated the MMP-2 expression in HT-29 cells, whereas the expression in HCT-116 cells remained unchanged. Conclusion Nimesulide can obviously inhibit the growth of colon cancer HT-29 cells with positive COX-2 protein, suggesting that nimesulide may downregulate the expression of MMP-2 by inhibiting the activity of COX-2.