Different microRNA expressions in gastric cancer depending on Helicobacter pylori infection

Abstract

Background and aim: Helicobacter pylori (H. pylori) infection increases the risk of gastric cancer through inducing aberrant gene expression regulation of cell. The microRNA (miRNA) regulate downstream target gene which can control cell proliferation and differentiation. The expressions of miRNA are usually analyzed with microarray and FFPE (formalin fixed paraffin embedded) sample can be used for microarray demanding high quality RNA. The study was undertaken to identify microRNAs differently expressed by H. pylori infection in patients with intestinal type of gastric cancer using miRNA microarray, and to confirm the candidate miRNAs expression levels. Methods: Total RNA was extracted from cancerous region and non-cancerous regions in formalin fixed paraffin embedded tissues of intestinal type gastric cancer patients who were H. pylori-positive (n=8) or -negative (n=8). The RNA was analyzed with a 3,523 miRNA profiling microarray based on the Sanger miRBase. Validation analysis was performed using TaqMan miRNA assays. Results: 219 miRNAs in the aberrant miRNA profiles across the miRNA microarray showed at least two-fold changed different expression in H. pylori-positive and -negative cancer tissue. Seven statistically significant candidate miRNAs were selected with online miRNA databases

miRWalk and HMDD. TaqMan miRNA assays confirmed that three miRNAs (miR-99b-3p, miR-564 and miR-638) were significantly increased in H. pylori-positive cancer than H. pylori-negative. In addition, four miRNAs (miR-204-5p, miR-338-5p, miR-375 and miR-548c-3p) were significantly increased in H. pylori-negative cancer than H. pylori-positive. Conclusion: The miRNA expression in the intestinal type of gastric cancer depending on H. pylori infection suggest that different gastric cancer pathogenesis could be exist between H. pylori-positive and -negative gastric cancer. FFPE specimens can be used for investigating the miRNA expression patterns. Further study which focused on miRNA function in gastric carcinogenesis is needed.