ABSTRACT
The eubaryotic complexity involves the expression and regulation of genes via RNA-DNA, RNA-RNA, DNA-protein and RNA-protein interactions. Recently, the role of RNA molecules in the regulation of genes in higher organisms has become more evident especially with the discovery that about 97% of the transcriptional output in higher organisms are represented as noncoding RNAs: rRNA, snoRNAs, tRNA, transposable elements, 5' and 3' untranslated regions, introns, intergenic regions and microRNAs. MicroRNAs function by negatively regulating gene expression via degradation or translational inhibition of their target mRNAs and thus participate in a wide variety of physiological and pathological cellular processes including: development, cell proliferation, differentiation, and apoptosis pathways. MicroRNA expression profiles in many types of cancers have been identified. Recent reports have revealed that the expression profiles of microRNAs change in various human cancers and appear to function as oncogenes or tumor suppressors. Abnormal microRNA expression has increasingly become a common feature of human cancers. In this review, we summarize the latest progress on the involvement of microRNAs in different types of cancer and their potential use as potential diagnostic and prognostic tumor biomarhers in the future