BACKGROUND AND AIM: 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.
METHODS: 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 microParaflo 
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.
RESULTS: 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.
CONCLUSION: 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.