Differential expression of microRNA species in human gastric cancer versus non-tumorous tissues

MicroRNAs (miRNAs) play important roles in carcinogenesis. The global miRNA expression profile of gastric cancer has not been reported. The purpose of the present study was to determine the miRNA expression profile of gastric cancer. Total RNA were first extracted from primary gastric cancer tissues and adjacent non-tumorous tissues and then small isolated RNAs (< 300 nt) were 3'-extended with a poly(A) tail. Hybridization was carried out on a mu Paraflo (TM) microfluidic chip (LC Sciences, Houston, TX, USA). After hybridization detection by fluorescence labeling using tag-specific Cy3 and Cy5 dyes, hybridization images were collected using a laser scanner and digitized using Array-Pro image analysis software (Media Cybernetics, Silver Spring, MD, USA). To validate the results and investigate the biological meaning of differential expressed miRNAs, immunohistochemistry was used to detect the differential expression of target genes. The most highly expressed miRNAs in non-tumorous tissues were miR-768-3p, miR-139-5p, miR-378, miR-31, miR-195, miR-497 and miR-133b. Three of them, miR-139-5p, miR-497 and miR-768-3p, were first found in non-tumorous tissues. The most highly expressed miRNAs in gastric cancer tissues were miR-20b, miR-20a, miR-17, miR-106a, miR-18a, miR-21, miR-106b, miR-18b, miR-421, miR-340*, miR-19a and miR-658. Among them, miR-340*, miR-421 and miR-658 were first found highly expressed in cancer cells. The expression of some target genes (such as Rb and PTEN) in cancer tissues was found to be decreased. To our knowledge, this is the first report about these miRNAs associated with gastric cancer. This new information may suggest the potential roles of these miRNAs in the diagnosis of gastric cancer.