[Oncogenic and tumour suppressor microRNAs]

Abstract

microRNAs constitute one of the most important discovery in the past few years in the field of gene expression regulation. They can precisely regulate the expression of a specific protein by inhibiting its translation and/or promoting the degradation of its mRNA. In several cancers, the expression of some microRNAs is misregulated, pointing toward the existence of microRNAs with oncogenic or tumour suppressor properties. The miR-17-92 miRNA cluster has been reported to have a pro-oncogenic role in a mouse model system of Myc-induced B cell lymphoma. Some of its targets mRNAs code for proteins with pro-apoptotic or anti-proliferative functions, which shed some light on the mechanism of action of this cluster. On the other hand, a tumour suppressor miRNA like let-7 targets mRNAs coding for oncogenes and is frequently down-regulated in cancers. The finding that c-Myc controls the expression of several of these microRNAs reveals new information on how misregulation of this proto-oncogene can promote tumorigenesis.