The relationship between Cdx2 and Cdx1 in intestinal metaplastic mucosa

Cdx1和Cdx2是调节肠道正常发育的转录因子，已被研究为人胃癌前肠化生发病机制的潜在关键分子。然而，Cdx1在肠化生中的表达调控尚不清楚。表达cdx2的转基因小鼠胃粘膜被肠化生黏膜所取代。本研究的目的是：(a) Cdx1在cdx2转基因小鼠胃肠化生黏膜中的表达；(b) Cdx1和Cdx2的关系。以小鼠肠化生模型cdx2转基因小鼠为研究对象，采用RT-PCR技术检测Cdx1基因的表达。DNA甲基化谱分析通过亚硫酸酯测序进行，Cdx2与Cdx1启动子的相互作用通过染色质免疫沉淀法、电泳迁移率转移法和荧光素酶报告基因法检测。Cdx2转基因小鼠胃中表达Cdx2 mRNA。然而，Cdx2转基因小鼠胃肠化生中不表达内源性Cdx2 mRNA。另一方面，cdx2转基因小鼠胃肠化生中表达了内源性Cdx1 mRNA和蛋白。Cdx1启动子在cdx2转基因小鼠胃的肠化生中未甲基化。染色质免疫沉淀试验和电泳迁移量转移试验表明，Cdx2在肠化生和正常肠中与Cdx1启动子区结合。Cdx2在人胃癌细胞系AGS、MKN45、MKN74中上调，siRNA-Cdx2下调Cdx1基因的转录活性。综上所述，在Cdx2转基因小鼠胃肠化生中，Cdx2通过与未甲基化的Cdx1启动子区结合诱导内源性Cdx1。

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.