Objective:To study the potential effects of heme oxygenase-1(HO-1)on the sensitivity of human gastric cancer cell line SGC7901 to 5-FU in vitro and the possible mechanisms involved. Methods:All cells were treated with various concentrations of hemin,ZnPP and 5-FU combination or alone at different times. The inhibition rate of cells was evaluated by MTT assay. Western blot was used for the detection of HO-1 expression. Flow cytometry was performed to detect cell apoptosis. ROS activity was examined by ROS colorimetric assay. Results:The application of ZnPP or 5-FU significantly inhibited the proliferation of human gastric cancer cells and the effect was dose-dependent.ZnPP(10 μmol/L)combined with 5-FU led to more inhibition and cell apoptosis than ZnPP or 5-FU alone(P < 0.05).On the other hand,hemin(10 μmol/L)markedly increased the resistance of SGC7901 cells to 5-FU-mediated cytotoxicity(P < 0.05). 5-FU or hemin increased HO-1 protein expression compared with control group,and the increase was reversed by the use of ZnPP. The activity of ROS in 5-FU plus ZnPP group had a significant increase compared with other groups(P < 0.05),and the increase was reversed by the addition of hemin. Conclusion:ZnPP can enhance the chemosensitivity of SGC7901 cells to 5-FU,in which the inhibition of HO-1 expression and elevation of intracellular ROS activity may be involved.