| Background activation-induced cytidine deaminase (AID) is the only human enzyme known to induce DNA mutation in human genomes, inappropriate expression of AID acts as a genomic mutator that contributes to tumorigenesis. Helicobacter pylori (Hp) was a carcinogen of human gastric carcinoma, Hp-mediated aberrant AID expression may play an important role in gastric cancer carcinogenesis through the accumulation of mutations in tumor-associated genes.However, there are the lack of studies on AID in gastric carcinoma, in particular, a comprehensive analysis of AID and p53 expression, Hp infection and clinicopathological parameters.Objective To study the expression of AID, p53 in gastric carcinoma and their relationship between Hp infection,to investigate the potentially carcinogenic mechanism of Hp.Methods 50 positive and 50 negative cases of gastric carcinoma diagnosed by the rapid urease test(RUT), who underwent RUT in gastroscopy before operation and surgical resection at the Department of Surgery, the First Affiliated Hospital of Anhui Medical University and confirmed by pathology, were analyzed in the study group. 20 RUT-positive and 20 RUT-negative cases of intraepithelial neoplasia and chronic gastritis respective, who underwent endoscopy at the Department of Endoscopy Room, the First Affiliated Hospital of Anhui Medical University and confirmed by pathology, and 20 cases of RUT-negative normal gastric mucosa tissue in endoscopic diagnosis were analyzed in the control group. Hp were detected by Warthin-Starry stain in all of the cases. The gastric tissue cases, who were double-positive and double-negative of RUT and Warthin-Starry stain regarded as Hp-positive and Hp-negative respectively, were involved in the study. The gastric tissue cases, who were single positive regarded as suspected Hp infection cases , were removed from in the study. The cases of RUT-negative normal gastric mucosa tissues in endoscopic diagnosis were assessed by HE staining.The cases who were diagnosised as normal gastric mucosa by pathology were involved in the study,the others were removed from in the study. The expression of AID and p53 which were assessed by SP immunohistochemistry in gastric carcinoma, intraepithelial neoplasia and chronic gastritis were analyzed with normal gastric mucosa. The results were analysed for the relations with Hp infection. The relationship between expression of AID, p53 and clinicopathological parameters in gastric carcinomas and the correlation between expression of AID and p53 were both statistically analysised. Theχ2 test or Fisher's exact test was used to assess the significant difference between the groups. Correlation analysis between variables were used by Spearsman correlation analysis, and calculated Pearson contingency coefficient(r). A p value <0.05 was considered statistically significant.Results There were 81 cases of gastric carcinoma including 38 Hp-positive and 43 Hp-negative cases, 32 cases of intraepithelial neoplasia including 14 Hp-positive and 18 Hp-negative cases, 37 cases of chronic gastritis including 18 Hp-positive and 19 Hp-negative cases and 10 cases of Hp-negative normal gastric mucosa involved in the study. The positive rates of AID in gastric carcinoma, intraepithelial neoplasia and chronic gastritis were 60.5%, 75.0% and 64.9%, respectively. And they were statistical difference with that in normal gastric mucosa(0.0%)(p<0.05). The positive rates of p53 in gastric carcinoma and intraepithelial neoplasia were 55.6% and 65.6%, were both significantly higher than that of chronic gastritis and normal gastric mucosa (0.0%) (P<0.05).The positive rates of AID in Hp-positive gastric carcinoma, intraepithelial neoplasia and chronic gastritis were 73.7%,85.7% and 83.3%, respectively, significantly higher than that in Hp-negative normal gastric mucosa(0.0%)(p<0.05).The positive rates of AID in Hp-positive gastric carcinoma and chronic gastritis were, respectively, significantly higher than that in Hp-negative gastric carcinoma and chronic gastritis (73.7% vs. 48.8%, P=0.022; 83.3% vs. 47.4%,P=0.038). The positive expression rates of AID and p53 were 60.5% and 55.6% in gastric carcinoma, and there was significantly positive correlation between them (P<0.001,r=0.395). The expression of AID in intestinal type gastric carcinoma was significantly higher than that in diffuse type gastric carcinoma (80.6% vs. 47.4%, P=0.005). The expression of p53 in gastric carcinoma were had no significant statistical difference with Lauren grouping. (P>0.05).The expression of AID and p53 in gastric carcinoma had no significant statistical difference with patient's sex, age, tumor size, tumor location, Lymph node metastasis, clinical TNM stage, respectively(P>0.05).Conclusion 1.There were aberrant AID expression in gastric cancer, intraepithelial neoplasia and chronic gastritis tissues, The aberrant expression of AID were positively correlated with the expression of p53 in gastric carcinoma.2. There had no positive expression in Hp-negative normal gastric mucosas.The positive rates of AID in Hp-positive gastric carcinoma and chronic gastritis mucosas were, respectively, significantly higher than that in Hp-negative gastric carcinoma and chronic gastritis mucosas.3. AID expression in intestinal type gastric cancer was significantly higher than that in diffuse type gastric cancer. AID may be related to the occurrence of intestinal type gastric cancer.Accordingly, our results suggest that aberrant AID expression in gastric tissues may play an important role in gastric cancer, especially, intestinal type gastric cancer carcinogenesis by resulting in p53 and other gene mutations accumulation. Hp may be one of factors promoted aberrant expression of AID in gastric mucosa tissues,and lead to the development of gastric cancer by the way told above.
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