MicroRNA profiling of gastric cancer patients from formalin-fixed paraffin-embedded samples

MicroRNA (miRNA) is a small non-coding RNA that targets specific mRNA. Recent progress in the extraction of RNA from formalin-fixed paraffin-embedded (FFPE) tissues has facilitated miRNA profiling using samples stored in laboratories worldwide. In the present study, miRNA profiling of gastric cancer patients is determined using FFPE samples. First, criteria were established for determining evaluable RNA from the FFPE samples. miRNA profiling was then undertaken using miRNA oligo chips with 885 featured genes. The FFPE samples were obtained from 47 gastric cancer patients who underwent operations between 1997 and 2007. Results showed that out of 47 paired samples, 37 pairs (78.8%) were evaluable by our criteria. A total of 30 miRNAs were significantly up-regulated and 11 miRNAs were down-regulated in gastric cancer compared with those in normal gastric tissue. Among these, 14 miRNAs, including miR-21, were identified as prognostic factors of gastric cancer patients. Furthermore, miR-34a was selected as an independent prognostic factor. In conclusion, we identified miRNAs that are associated with the prognosis of gastric cancer patients. miRNA profiling using FFPE samples is a useful and promising method of evaluation for samples stored in laboratories worldwide, and can generate extremely valuable clinical data.