| Objective: Gastrin and cyclooxygenase-2 (COX-2) play very important roles in occurrence and progression of tumor, but the effects and mechanisms of gastrin receptor antagonist and special COX-2 inhibitor on the prevention and cure of gastric cancer have not been fully elucidated. The present study investigated the effects of a gastrin receptor antagonist (proglumide) and a special COX-2 inhibitor (NS-398) on the proliferation and apoptosis of gastric cancer MKN-45 cell line to examine whether the two non-celltoxicity agents have synergistic anticancer role, so as to establish the experimental bases for application gastrin receptor antagonist associating with special COX-2 inhibitor in treating gastric cancer.Methods: MKN-45 cells were incubated in the medium with proglumide[(1,3,5,6,8,10)×10-3 mol/L], NS-398[(1×10-8～1×10-3) mol/L] and the combination of these two agents(5×10-3 mol/L proglumide and 1×10-5 mol/L NS-398), respectively. Cell growth and proliferation of MKN-45 were analyzed with MTT assay; apoptosis was detected with flow cytometry assay; expression of bcl-2 and PPARγgene was determined by RT-PCR. Expression of COX-2 protein in MKN-45 cells treated with proglumide was detected by immunocytochemistry.Results: Both of proglumide and NS-398 inhibited MKN-45 cell proliferation in a dose dependent manner. Combination with proglumide and NS-398 inhibited the proliferation more remarkably than either agent applied singly (P<0.01), suggesting that combination with two agents synergetically inhibits the proliferation of gastric cancer cells. Apoptosis rates were (24.72±3.19)%, (26.69±3.35)% and (36.11±4.57)% in MKN-45 cells treated with 5×10-3 mol/L proglumide, 1×10-5 mol/L NS-398 and combination group, respectively, which were significantly higher than that in control group [(1.57±0.55)%, P<0.01]. The apoptosis rate of combination group was greater than that of the two agents applied singly (P<0.05). Proglumide and NS-398 down-regulated bcl-2 mRNA expression respectively (P<0.01 or P<0.05); expression of bcl-2 mRNA in the cells treated with proglumide and NS-398 was much lower than that with the two agents applied singly (P<0.05). Proglumide up-regulated the expression of PPARγmRNA (P<0.05); the expression of PPARγmRNA was much higher in the cells treated with proglumide and NS-398 than proglumide applied singly (P<0.05).Whereas NS-398 did not affect PPARγmRNA expression (P>0.05). Proglumide inhibited the expression of COX-2 protein in MKN-45 cell.Conclusion: Both of proglumide and NS-398 are able to inhibit cell proliferation and induce apoptosis in MKN-45 cell. This apoptosis may be mediated by down-expression of apoptosis-inhibited gene bcl-2. Co-treatment with proglumide and NS-398 may have synergistic anticancer role.
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