Research On The Role And Regulation Of CDX2 In The Development Of Gastric Intestinal Metaplasia And Gastric Adenocarcinoma

Objective: (1) To investigate the expression of caudal-type homeobox transcription factor-2 (CDX2) protein and mRNA in gastric carcinoma (GC) and precancerous lesions and its correlation with clinicopathological features. To study the role of CDX2 in development of intestinal metaplaisa of gastric mucosa and GC. (2) To explore the role of CDX2 promoter methylation in regulating the gene expression. Methods: (1) The expression of CDX2 protein in GC and precancerous lesions were detected by using immunohistochemistry method (S-P method). Alcian blue-periodic acid-schiff (AB/PAS) and high iron diamine/alcian blue (HID/AB) staining were used to classify intestinal metaplasia (IM). (2) Semi-quantitative RT-PCR assay was used to detect the relationship between CDX2 mRNA expression and clinicopathological features. (3) RT - PCR and MSP methods were used to detect the expression of CDX2 mRNA and methylation status of Cdx2 gene in SGC-7901 and BGC-823 cells before and after treatment with DAC. Results: (1) CDX2 protein was not detected in normal gastric mucosa and chronic superficial gastritis. The positive rates of CDX2 protein in IM, dysplasia and GC (81.7%, 50%, 48.2%) were higher than that of normal mucosa (P<0.05). The positive rates of CDX2 protein in IM was much higher than that of dysplasia and GC (P<0.05). There was no significant difference between dysplasia and carcinoma(P>0.05). There was no relationship between CDX2 protein expression and the classification of IM or the degree of dysplasia. The expression of CDX2 protein was significantly higher in intestinal-type carcinoma (67.4%) than in diffuse and mixed type carcinoma (25.7%, 42.9%, P<0.05). Positive expression of CDX2 protein was mainly found in moderately to well differentiated GC. There was a negative association between nuclear CDX2 protein expression and lymph node metastasis and TNM stage of gastric carcinoma , the difference was statistically significant(P<0.05). The patients with CDX2 protein positive expression showed higher survival rate than those with CDX2-negative expression (P=0.038). Multivariate analysis revealed that the expression of CDX2 protein and lymph node metastasis were independent prognostic indicators of GC (P<0.05). (2) The results of RT-PCR showed that CDX2 mRNA expression in gastric cancer tissues was obviously higher than that in normal adjacent tissues (P<0.05). The expression of CDX2 mRNA in GC was related to lauren classification of gastric cancer. The expression of CDX2 mRNA was significantly higher in intestinal-type carcinoma than in diffuse and mixed type carcinoma (P<0.05). (3) CDX2 is hypermethylated in extracorporeal cultured gastric carcinoma cell lines. CDX2 re-expressed after the effect of the demethylating agent 5-Aza- 2'- deoxycytidine on the growth of human gastric carcinoma cell lines. Conclusions: (1) CDX2 protein was not detected in normal gastric mucosa. CDX2 protein was high expressed in most of IM. The expression of CDX2 protein and mRNA were related to the lauren classification. These findings suggested that the abnormal expression of CDX2 protein and mRNA might play an important role in the development gastric carcinoma and especially the occurrence of intestinal-type gastric carcinoma. It may induce the transformation of the gastric mucosa into intestinal metaplasia. (2) The positive rate of CDX2 protein in IM was higher than those in dysplasia and GC. Positive expression of CDX2 protein was mainly found in moderately to well differentiated GC. There was a negative association between CDX2 protein expression and lymph node metastasis and TNM stage of gastric carcinoma. The patients with CDX2 protein positive expression showed higher survival rate than those with CDX2-negative expression. These results suggested CDX2 might be a anti-oncogene gene. (3) The down-regulation of CDX2 gene was associated with the hypermethylation of its promoter.