MicroRNAs: Potential biomarkers in cancer.

microRNAs (miRNAs) are evolutionarily conserved small noncoding RNAs, also known as micromanagers of gene expression. Polymorphisms in the miRNA pathway (miR-polymorphisms) are emerging as powerful tools to study the biology of a disease and have the potential to be used in disease prognosis and diagnosis. Advancements in the miRNA field also indicate a clear involvement of deregulated miRNA gene signatures in cancers, and several polymorphisms in pre-miRNA, miRNA binding sites or targets have been found to be associated with various cancers. The miRNA polymorphisms have also been reported to influence tumor aggressiveness as well as survival of cancer patients. miRNAs have a revolutionary impact on cancer research over recent years. They emerge as important players in tumorigenesis, leading to a paradigm shift in oncology. The extensive and comprehensive use of miRNA microarrays has enabled the identification of a number of miRNAs as potential biomarkers for cancer. Many miRNAs have been identified to act as oncogenes, tumor suppressors, or even modulators of cancer stem cells and metastasis. Some studies not only reported the identified miRNA biomarkers, but also deciphered their target genes and the underlying mechanisms. The rapid discovery of many miRNA targets and their relevant pathways has contributed to the development of miRNA-based therapeutics.