The relationship between Cdx2 and Cdx1 in intestinal metaplastic mucosa

Cdx 1和Cdx 2是调节正常肠发育的转录因子，已被研究为人胃癌前肠上皮化生发病机制中的潜在关键分子。然而，Cdx 1在肠上皮化生中的表达调控知之甚少。Cdx 2转基因小鼠胃的Cdx 2表达胃粘膜被肠化生粘膜所取代。本研究的目的是：（a）Cdx 1在Cdx 2转基因小鼠胃粘膜肠化生中的表达;（B）Cdx 1和Cdx 2之间的关系。通过亚硫酸氢盐测序进行DNA甲基化谱分析，并通过染色质免疫沉淀试验、电泳迁移率变动试验和荧光素酶报告基因试验检查Cdx 2与Cdx 1启动子的相互作用。Cdx 2基因转基因小鼠胃中有Cdx 2 mRNA表达。然而，内源性Cdx 2 mRNA不表达的Cdx 2转基因小鼠胃的肠上皮化生。另一方面，内源性Cdx 1的mRNA和蛋白质表达的Cdx 2转基因小鼠胃的肠上皮化生。Cdx 2转基因小鼠胃的肠上皮化生中Cdx 1启动子未甲基化。染色质免疫沉淀法和电泳迁移率变动分析表明，Cdx 2在肠化生和正常肠组织中与Cdx 1启动子区结合。Cdx 2上调和siRNA-Cdx 2下调人胃癌细胞系AGS、MKN 45和MKN 74中Cdx 1基因的转录活性。结论：在Cdx 2转基因小鼠胃肠上皮化生中，Cdx 2通过与Cdx 1启动子区的非甲基化结合诱导内源性Cdx 1的表达。

Cdx1 and Cdx2, which are transcription factors regulating normal intestinal development, have been studied as potential key molecules in the pathogenesis of the precancerous intestinal metaplasia of the human stomach. However, the regulation of Cdx1 expression in the intestinal metaplasia is poorly understood. Cdx2-expressing gastric mucosa of Cdx2-transgenic mouse stomach was replaced by intestinal metaplastic mucosa. The aim of this study was to investigate the following :(a) Cdx1 expression in the intestinal metaplastic mucosa of the Cdx2-transgenic mouse stomach ; and(b) the relationship between Cdx1 and Cdx2.A mouse model of intestinal metaplasia, the Cdx2-transgenic mouse, was used to investigate Cdx1 gene expression by RT-PCR. DNA methylation profile analysis was performed by bisulfite sequencing, and the interaction of Cdx2 with the Cdx1 promoter was examined by chromatin immunoprecipitation assay, electrophoretic mobility shift assay, and luciferase reporter assays. Cdx2 mRNA was expressed in the Cdx2-transgenic mouse stomach. However, endogenous Cdx2 mRNA was not expressed in the intestinal metaplasia of the Cdx2-transgenic mouse stomach. On the other hand, endogenous Cdx1 mRNA and protein were expressed in the intestinal metaplasia of the Cdx2-transgenic mouse stomach. The Cdx1 promoter was unmethylated in the intestinal metaplasia of the Cdx2-transgenic mouse stomach. Chromatin immunoprecipitation assay and electrophoretic mobility shift assay showed that Cdx2 was bound to the Cdx1 promoter region in the intestinal metaplasia and the normal intestine. Cdx2 upregulated and siRNA-Cdx2 downregulated the transcriptional activity of the Cdx1 gene in the human gastric carcinoma cell lines AGS, MKN45, and MKN74.In conclusion, transgenic Cdx2 induced endogenous Cdx1 through the binding of Cdx2 to the unmethylated Cdx1 promoter region in the intestinal metaplasia of the Cdx2-transgenic mouse stomach.