Noncoding microRNAs act as posttranscriptional repressors of gene function and are often deregulated in cancers and other diseases. Here we review recent findings on microRNA roles in tumorigenesis and report a microRNA profiling screen in transforming growth factor-beta1 (TGF-beta)-induced epithelial-mesenchymal transition (EMT) in human keratinocytes, a model of epithelial cell plasticity underlying epidermal injury and skin carcinogenesis. We describe a novel EMT-specific microRNA signature that includes induction of miR-21, a candidate oncogenic microRNA associated with carcinogenesis. By integrating the microRNA screen results with target prediction algorithms and gene expression profiling data, we outline a framework for TGF-beta-directed microRNA:messenger RNA (mRNA) regulatory circuitry and discuss its biological relevance for tumor progression.
2007 S. Karger AG, Basel