The role of microRNAs in gastrointestinal cancers.

MicroRNAs (miRNAs) are small noncoding RNAs that function as endogenous silencers of numerous target genes. Hundreds of human miRNAs have been identified in the human genome, and they are expressed in a tissue-specific manner and play important roles in cell proliferation, apoptosis, and differentiation. Links between miRNAs and human diseases are increasingly apparent, and aberrant expression of miRNAs may contribute to the development and progression of human malignancies. Recent studies have shown that some miRNAs play roles as tumor suppressors or oncogenes in gastrointestinal cancers. miRNA expression is regulated by different mechanisms including transcription factor binding, epigenetic alterations, and chromosomal abnormalities. miRNA expression profiling may be a powerful clinical tool for cancer diagnosis, and regulation of miRNA expression could be a novel strategy for the chemoprevention of human gastrointestinal cancers. In this article, the biological importance of miRNAs in human gastrointestinal cancers is summarized.