MicroRNAs in gastric cancer: from benchtop to bedside

Gastric carcinogenesis represents a stepwise progression from chronic inflammation to invasive adenocarcinomas and distant metastasis. It has been widely accepted that these pathologic changes are contributed by aberrant activation or inactivation of protein-coding proto-oncogenes and tumor suppressor genes. However, recent discoveries in microRNA research have reshaped our understanding of the role of non-protein-coding genes in carcinogenesis. MicroRNAs (miRNAs) are a family of 18-25-nucleotide small RNAs that negatively regulate gene expression at the post-transcriptional level during various crucial cell processes such as apoptosis, differentiation and development. Changes in miRNA expression profiles have been observed in a variety of human tumors, including gastric cancer. Further studies demonstrated that miRNAs may function as tumor suppressors and oncogenes. These findings have shown great potential of miRNAs as a novel class of therapeutic targets. In addition, it was found that some miRNAs were directly involved in patients with gastric cancer, including prognosis prediction, treatment selection, and in the search for unknown primary sites. MiRNAs have also been proved to be detectable in serum and plasma. In this review, we summarize the function of miRNAs in gastric cancer. Furthermore, we describe the pathophysiological roles of these miRNAs and their clinical potential as diagnostic biomarkers and therapeutic targets.