Objective To investigate the effect of berberine on inhibiting HT-29 human colon cancer cell proliferation induced by deoxycholic acid(DCA).Methods The berberine with concentration of 1,5,10 or 20?mol/L were added into the HT-29 human colon cancer cell culture media containing 200?mol/L DCA.The effects of berberine on cell proliferation were studied by the method of MTT.RT-PCR was applied to measure the expression of cyclooxygenase-2(COX-2)mRNA.Cellular immunochemical stain was applied to label COX- 2 protein expression.Concentration of prostaglandin E2(PGE2)was measured by radioimmunoassay. Results HT-29 cells were incubated with DCA for 6 h,COX2 expression of cells were increased prominent compared to controls(65.5%?5.6% vs.6.2%?1.1%).The level of PGE2 were increased(24.1 ng/L?1.4 ng/L vs.10.6 ng/L?0.8 ng/L).One?mol/L berberine reduced the proliferation rate of HT-29 in- duced by DCA over 6 h,the proliferation rate was 7.4?3.5%.Both COX-2 mRNA expression and the level of PGE2 were inhibited when the concentration of berberine was over 1?mol/L,and in a concentration-time dependent manner.Conclusions Berberine can inhibit the proliferation of HT-29 human colon cancer cell in- duced by DCA.Berberine can also suppress the expression of COX-2,and decrease the production of PGE2. These data provide new insights into the mechanism of its anti-cancer properties.