microRNAs: a new emerging class of players for disease diagnostics and gene therapy

microRNAs (miRNAs) are a new class of non-protein-coding small RNAs, which regulate the expression of more than 30% protein-coding genes. The unique expression profiles of different miRNAs in different types of cancers and at different stages in one cancer type suggest that miRNAs can function as novel biomarkers for disease diagnostics and may present a new strategy for miRNA gene therapy. Anti-miRNAs and antisense oligonucleotides (ASO) have been employed to inhibit specific miRNA expression in vitro and in vivo for investigational and clinical purposes. Although miRNA-based diagnostics and gene therapy are still in their infancy, their huge potentials will meet our need for future disease diagnostics and gene therapy. High efficient delivery of miRNAs into targeted sites, designing accurate anti-miRNA/ASOs, and related biosafety issues are three major challenges in this field.