title: miR-21: a small multi-faceted RNA.
abstract: More than 1000 microRNAs (miRNAs) are expressed in human cells, some tissue or cell type specific, others considered as house-keeping molecules. Functions and direct mRNA targets for some miRNAs have been relatively well studied over the last years. Every miRNA potentially regulates the expression of numerous protein-coding genes (tens to hundreds), but it has become increasingly clear that not all miRNAs are equally important; diverse high-throughput screenings of various systems have identified a limited number of key functional miRNAs over and over again. Particular miRNAs emerge as principal regulators that control major cell functions in various physiological and pathophysiological settings. Since its identification 3 years ago as the miRNA most commonly and strongly up-regulated in human brain tumour glioblastoma [1], miR-21 has attracted the attention of researchers in various fields, such as development, oncology, stem cell biology and aging, becoming one of the most studied miRNAs, along with let-7, miR-17-92 cluster ('oncomir-1'), miR-155 and a few others. However, an miR-21 knockout mouse has not yet been generated, and the data about miR-21 functions in normal cells are still very limited. In this review, we summarise the current knowledge of miR-21 functions in human disease, with an emphasis on its regulation, oncogenic role, targets in human cancers, potential as a disease biomarker and novel therapeutic target in oncology.
authors.affiliation: Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA. akrichevsky@rics.bwh.harvard.edu
authors.forename: Anna M
authors.initials: AM
authors.lastname: Krichevsky
authors.forename: Galina
authors.initials: G
authors.lastname: Gabriely
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001483:Base Sequence; D014408:Biomarkers, Tumor; D002453:Cell Cycle / Q000502:physiology; D004194:Disease / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology* / Q000628:therapy; D012323:RNA Processing, Post-Transcriptional; D014158:Transcription, Genetic
chemical_list: D014408:Biomarkers, Tumor; C524940:MIRN21 microRNA, human; D035683:MicroRNAs