MicroRNA expression profile of gastric cancer stem cells in the MKN-45 cancer cell line.

MicroRNAs (miRNAs) play important roles in post-transcriptional gene silencing of target messenger RNAs, which are involved in virtually all biological processes. Previously, we have demonstrated that spheroid body-forming cells from the MKN-45 cancer cell line possessed gastric cancer stem cell (CSC) properties. In this study, we aimed to determine the miRNA profile of the gastric CSCs and to explore the role of miRNAs in gastric CSCs. Human miRNA microarrays, which contain probes specific for 1887 human miRNAs were used to determine the expression profiles of the gastric CSCs. A total of 182 miRNAs with a more than 2-fold change were identified to be differentially expressed between the spheroid body-forming cells and the parental cells. Of these miRNAs, 9 miRNAs were over-expressed in the spheroid body-forming cells, while the other 173 miRNAs were all under-expressed, indicating that the role of most miRNAs in human gastric CSCs may be tumor suppressors. The results of microarray analysis were validated by quantitative real-time polymerase chain reaction, and the consistence rate is 70% (7 out of 10). The target genes for the validated miRNAs were predicted by using three online software programs, miRanda, PicTar, and TargetScan. Most of the potential targets of the miRNAs were relevant to the regulation of actin cytoskeleton, focal adhesion, extracellular matrix-receptor interaction, and the pathways in cancer. Especially, several genes are associated with some pivotal signaling pathways of the 'stem cell genes'. Evaluating the characteristic miRNAs of the gastric CSCs may be a new method for studying gastric cancer and developing therapeutic strategies, which aimed at eradicating the subpopulation of CSCs in gastric cancer.