MicroRNA Expression in Selected Carcinomas of the Gastrointestinal Tract

MicroRNAs (miRNAs) comprise a recently discovered class of small, 18–25 nucleotide, noncoding RNA sequences that regulate gene expression at the posttranscriptional level by binding to and inhibiting the translation of target messenger RNAs (mRNAs). Characteristic patterns of miRNA expression have been described in several malignancies of the gastrointestinal tract, and numerous investigators have demonstrated interactions between specific miRNA species and target oncogenes or tumor-suppressor genes. It is clear that miRNAs play an important role in regulating expression of a number of genes involved in gastrointestinal carcinogenesis, and, thus, these molecules may represent either diagnostic markers of, or therapeutic targets for, some types of malignancy. This paper summarizes the literature regarding miRNA expression in carcinomas of the colon, pancreas, and liver and discusses some of the mechanisms by which these molecules participate in gastrointestinal oncogenesis.