Relationship of novel genetically engineered mouse and the epithelial-mesenchymal transition in the metastastic progression of gastric cancers.

Abstract

3 Background: By creating mice deficient in E-cadherin, Smad4, and p53, we evaluated whether and how Cdh1 heterozygosity may accelerate the development and progression of gastric cancer, in combination with loss of Smad4 and p53. Methods: Compound conditional knockout mice of Smad4, p53, and E-cadherin were mated with Pdx-1-Cre transgenic mice. Offsprings were monitored for the development of gastric adenocarcinomas. Results: Gastric adenocarcinomas spontaneously arose in Pdx-1-Cre;Smad4F/F;Trp53F/F;Cdh1F/+ mice and recapitulated human diffuse type gastric cancers in histopathology. Gastric adenocarcinoma was more frequent in Pdx-1-Cre;Smad4F/F;Trp53F/F;Cdh1F/+ mice than in Pdx-1-Cre;Smad4F/F;Trp53F/F mice. When compared to Pdx-1-Cre;Trp53F/F;Cdh1F/F mice, Pdx-1-Cre;Smad4F/F;Trp53F/F;Cdh1F/+ mice developed gastric adenocarcinomas more rapidly, suggesting that Smad4 and E-cadherin cooperate to constrain the development of gastric adenocarcinomas. Lung metastases were identified in three Pdx-1-Cre;Smad4F/F;Trp53F/F;Cdh1F/+ mice, but not in the other genotypes. The epithelial-to-mesenchymal transition (EMT), characterized by increased vimentin expression, was identified at the invasive tumor front of gastric adenocarcinomas arising in Pdx-1-Cre;Smad4F/F;Trp53F/F;Cdh1F/+ mice. This phenotype was less prominent in mice with intact E-cadherin or Smad4, indicating that the suppression of EMT by E-cadherin or Smad4 may reduce metastatic signaling pathways in Pdx-1-Cre;Smad4F/F;Trp53F/F;Cdh1F/+ mice. Conclusions: Loss of E-cadherin and Smad4 cooperate with p53 loss to promote the development and metastatic progression of gastric adenocarcinomas, with similarities to human diffuse type gastric cancer. Thus, our novel genetically-engineered mouse models reveal the importance of EMT in the metastatic progression of gastric cancers, providing a unique model to test agents targeting the metastatic progression in gastric cancers.