Expression, regulation and mechanism of action of the miR-17-92 cluster in tumor cells (Review)

MicroRNAs (miRNAs), a class of short, single-stranded non-coding RNAs, regulate and control gene expression in eukaryotes by degrading mRNA at the post-transcriptional level. Regulation by miRNAs involves a plethora of biological processes, such as cell differentiation, proliferation, metastasis, metabolism, apoptosis, tumorigenesis and others. miRNAs also represent a powerful tool in disease diagnosis and prognosis. The miR-17-92 cluster, one of the most extensively investigated microRNA clusters, comprises six mature miRNA members, including miR-17, miR-18a, miR-19a, miR-19b, miR-20a and miR-92a. Originally identified as being involved in tumorigenesis, it is currently evident that the expression of the miR-17-92 cluster is upregulated in a wide range of tumor cells and cancer types; thus, this cluster has been identified as a potential oncogene. Considering the growing interest in the field of miR-17-92 research, we herein review recent advances in the expression and regulation of this cluster in various cancer cells, discuss the proposed mechanism of action for tumorigenesis and tumor development, and propose clinical and therapeutic applications for miR-17-92 cluster members, such as potential cancer biomarkers.