K19-C2mE transgenic (Tg) mice, simultaneously expressing
cyclooxygenase-2 (COX-2) and microsomal
prostaglandin E synthase-1 (mPGES-1) in the gastric mucosa under the
cytokeratin 19 gene promoter, were here treated with
N-methyl-N-nitrosourea (MNU) and inoculated with Helicobacter pylori (H. pylori) to investigate gastric
carcinogenesis. Wild-type (WT) and Tg mice undergoing MNU treatment frequently developed
tumors in the pyloric region (100% and 94.7%, respectively); multiplicity in Tg was higher than that in WT (P < 0.05) with H. pylori
infection. Larger pyloric
tumors were more frequently observed in Tg than in WT (P < 0.05). In addition, Tg developed fundic
tumors, where WT did not. No gastric
tumors were observed without MNU treatment. Transcripts of
TNF-alpha, iNOS, IL-1beta, and CXCL14 were up-regulated with H. pylori
infection in both genotypes and were also increased more in Tg than in WT within H. pylori-inoculated animals. Immunohistochemical analysis demonstrated significantly greater
beta-catenin accumulation in pyloric
tumors, compared with those in the fundus (P < 0.01) with mutations of exon 3; 18.2% and 31.6% in MNU-alone and MNU + H. pylori-treated WT, whereas 21.4% and 62.5% was observed in the Tg, respectively; the latter significantly higher (P < 0.05), suggesting the role of H. pylori in Wnt activation. In conclusion, K19-C2mE mice promoted
gastric cancer in both fundic and pyloric regions. Furthermore
beta-catenin activation may play the important role of pyloric
carcinogenesis especially in H. pylori-infected Tg. Induction of various inflammatory
cytokines in addition to overexpression of COX-2/mPGES-1 could be risk factors of gastric
carcinogenesis and may serve as a better gastric
carcinogenesis model.