Cooperativity of E-cadherin and Smad4 Loss to Promote Diffuse-type Gastric Adenocarcinoma and Metastasis
Menée à l'aide de modèles murins, cette étude met en évidence des mécanismes par lesquels la bêta-caténine favorise le processus métastatique d'un cancer gastrique
Loss of E-cadherin (CDH1), Smad4 and p53 have all been shown to play an integral role in gastric, intestinal and breast cancer formation. Compound conditional knockout mice for Smad4, p53, and Ecadherin were generated to define and compare the roles of these genes in gastric, intestinal and breast cancer development by crossing with Pdx-1-Cre, Villin-Cre and MMTV-Cre transgenic mice. Interestingly, gastric adenocarcinoma was significantly more frequent in Pdx-1-Cre;Smad4F/F;Trp53F/F;Cdh1F/+ mice than in Pdx-1-Cre;Smad4F/F;Trp53F/F;Cdh1+/+ mice, demonstrating that Cdh1 heterozygosity accelerates the development and progression of gastric adenocarcinoma, in combination with loss of Smad4 and p53. Pdx-1-Cre;Smad4F/F;Trp53F/F;Cdh1F/+ mice developed gastric adenocarcinomas without E-cadherin expression. However, intestinal and mammary adenocarcinomas with the same genetic background retained E-cadherin expression and were phenotypically similar to mice with both wild-type Cdh1 alleles. Lung metastases were identified in Pdx-1-Cre;Smad4F/F;Trp53F/F;Cdh1F/+ mice, but not in the other genotypes. Nuclear beta-catenin accumulation 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 Ecadherin or Smad4, indicating that the inhibition of beta-catenin signaling by E-cadherin or Smad4 downregulates signaling pathways involved in metastases in Pdx-1-Cre;Smad4F/F;Trp53F/F;Cdh1F/+ mice. Knockdown of Beta-catenin significantly inhibited migratory activity of Pdx-1- Cre;Smad4F/F;Trp53F/F;Cdh1F/+ cell lines. Thus, loss of E-cadherin and Smad4 cooperate with p53 loss to promote the development and metastatic progression of gastric adenocarcinomas, with similarities to human gastric adenocarcinoma. Implications: This study demonstrates that inhibition of beta-catenin is a converging node for the antimetastatic signaling pathways driven by E-cadherin and Smad4 in Pdx-1-Cre;Smad4F/F;Trp53F/F;Cdh1F/+ mice, providing novel insights into mechanisms for gastric cancer metastasis.