Objective To explore the effects of morphine on growth of human esophageal cancer cell Ec109 and elucidate its possible molecular mechanism. Methods Ec109 cells were randomly divided into four groups: three groups of cells were treated with different concentrations of morphine （0.1，10 and 1 000 umol/L），and a control group was treated with normovolemic RPMI-l640 nutrient solution. Cells were incubated for 24，48 and 72 h，and rates of proliferation inhibition were determined by CCK-8 assay. Flow cytometry was performed after 48-h incubation to assess apoptosis and cell cycle distribution in the four groups. We also quantified the levels of p53 and caspase-3 mRNA using real-time PCR. Results Rates of proliferation inhibition were significantly higher in the three morphine-treated groups than in the control group（P<0.01）；they were higher with higher morphine concentration and longer incubation（P<0.05）. Proportions of apoptotic cells and cells in G1 phase were also higher in the morphine-treated cells at 48 h（P<0.05），and these proportions were higher with increasing morphine concentration（P<0.05）. Levels of p53 and caspase-3 mRNAs were also up-regulated by morphine in a concentration-dependent manner（P<0.05）. Conclusion These results suggest that morphine can inhibit proliferation of Ec109 cells by inducing apoptosis. Morphine may exert these effects，in part，by up-regulating p53 and caspase-3 expression.
