MicroRNAs as Critical Regulators Involved in Regulating Epithelial-Mesenchymal Transition

The epithelial-mesenchymal transition (EMT) is a fundamental biological process that is involved in normal embryogenesis, would healing, and tissue repair, as well as numerous pathologies, including organ fibrosis, malignant transformation, and cancer progression. Both transcriptional and post-transcriptional regulatory mechanisms contribute to a complex and tightly controlled regulatory network during the EMT process, and a growing body of evidence now demonstrates that microRNAs (miRNAs) are crucial regulators of this network. miRNAs are a class of small non-coding RNAs that regulate gene expression through translational repression or mRNA degradation. A set of miRNAs have been discovered that have the potential to target multiple components of the signaling pathways and downstream effectors of the EMT. Our understanding of the roles that miRNAs play during the EMT process suggests that these miRNAs may eventually serve as novel biomarkers and therapeutic targets for various EMT-based pathological conditions. This review summarizes the current knowledge concerning how miRNAs mechanistically regulate the EMT and discusses the specific roles that miRNAs play in three EMT subtypes. We hope that a more comprehensive understanding of the functions of miRNAs in the EMT process will lead to the rapid development of novel diagnostic techniques and molecular-based strategies for controlling EMT.