Abstract: Objective To explore the effects of gastrin-17 and its antagonist PGL on cell proliferation and the expression of trefoil factor1(TFF1), trefoil factor3(TFF3) in human gastric cancer line MKN-45, and to analyze the function of TFF1 and TFF3 in the development of gastric lesions. Methods MKN45 cells were incubated in the medium with Gas-17 (1~1000 nmo1/L), proglumide (1~10 mmol/L) and the combination of these two agents (100nmo1/L Gas-17 and 1~10 mmol/L proglumide). Medium with no drug was used as control. Cell growth and proliferation of MKN45 were analyzed with MTT assay. The expression of TFF1 and TFF3 were determined by Western blot in MKN45 cells which were incubated with Gas-17 (1~100nmo1/L), proglumide (10 mmol/L), the combination (100nmo1/L Gas-17 and 10mmol/L proglumide) and the control group. Results MTT showed Gas-17 signifi cantly promoted cell proliferation at the concentration of 1~1000 nmo1/L (P<0.05); PGL signifi cantly inhibited cell proliferation at the concentration of 1～10mmol/L (P<0.05); In the combination group, PGL (1~10mmol/L) signifi cantly blocked and inhibited cell proliferation induced by Gas-17 (P<0.05). Meanwhile, Western blot showed the expression of TFF1 and TFF3 protein was found in gastric cancer cell line MKN45; Gas-17 signifi cantly increased TFF3 while inhibited TFF1 (P<0.05); PGL signifi cantly up-regulated TFF1 while inhibited TFF3. In the combination group, PGL signifi cantly inhibited the down-regulation of TFF1 and up-regulation of TFF3 stimulated by Gas-17 (P<0.05). Conclusion Gas-17 would induce cell proliferation in human gastric cancer line MKN45 while its antagonist PGL could signifi cantly block and inhibit this effect. Gas-17 could inhibit TFF1 and increase TFF3 which may be one of the mechanisms of Gas-17 inducing the development of gastric carcinoma.