miRNAs, cancer, and unconventional miRNA functions

Abstract

MicroRNAs are non-protein-coding RNA molecules that control and fine-tune gene expression at the post-transcriptional level by negatively regulating their target genes. MicroRNAs mature into 22-nucleotide-long RNA transcripts that negatively regulate gene expression by inducing either inhibition of translation or degradation of mRNAs. Increasing evidence suggests that distinct signatures of microRNAs are a feature of human cancers. MicroRNA expression patterns have been linked to tumor development, progression, and response to therapies, implying that they could be used as prognostic and diagnostic biomarkers. Moreover, based on a growing body of research indicating that microRNAs may serve as tumor suppressive or tumor promoter functions, miRNA-based therapy against cancer has lately been utilized, either alone or in conjunction with current targeted strategies. One of the advantages of microRNA-based therapeutics is that they can target numerous components of signaling circuits involved in cell differentiation, proliferation, and survival. In this review, the current available evidence about miRNAs and their diagnostic, prognostic, and therapeutic potential will be discussed. miRNAs may play chief roles in the development and progression of human cancers, offer great advantages in differential diagnosis, and can be therapeutically targeted.