Similarly up-regulated microRNA-106a in matched formalin-fixed paraffin-embedded and fresh frozen samples and the dynamic changes during gastric carcinogenesis and development

Evidence increasingly suggests that miR-106a is always elevated in gastric cancer; however, little is known about the expression trend and clinical significance in the whole process of gastric carcinogenesis and development. To investigate the dynamic changes of miR-106a in each stage during gastric carcinogenesis, we used formalin-fixed, paraffin-embedded (FFPE) tissues which had been reported to have valuable information for miRNA research in our previous studies. Here, we compared the expression of miR-106a in FFPE and fresh frozen tissues using real-time polymerase chain reaction. On the basis of the high correlation of miR-106a quantitative data from the two resources, FFPE samples were subsequently performed to elucidate the location and expression of miR-106a using in situ hybridization in sequential tissues, including normal gastric mucosa, chronic atrophic gastritis combined with various degrees of dysplasia, early and advanced gastric cancer. Finally, we found that miR-106a was similarly up-regulated in gastric cancer regardless of sample types although fragmentation existed inevitably in FFPE tissues. Notably, the frequency and extent of miR-106a expression gradually increased during the transition from atypical hyperplasia to advanced carcinoma and had already had positive signals in early precancerous lesions but negative signals in normal gastric mucosal epithelial cells. Our research, according to these results, indicated that FFPE samples can serve as an important research tool for miRNA field, and the early changes of miR-106a detected in such samples may have clinical application as a potential biomarker for the discovery and diagnosis of gastric cancer.