Circulating MicroRNAs in Cancer: Potential and Challenge

Abstract

MicroRNAs (miRNAs) are endogenous non-coding small RNA molecules that can be secreted into the circulation and exist in remarkably stable forms. Like intercellular miRNAs, circulating miRNAs participate in numerous regulations of biological process and expressed aberrantly under abnormal or pathological status. The quality and quantity changes of circulating miRNAs are associated with the initiation and progression of cancer and can be easily detected by basic molecular biology techniques. Consequently, considerable effort has been devoted to identify suitable extracellular miRNAs for noninvasive biomarkers in cancer. However, several challenges need to be overcome before the practical application. In this review, we discuss several issues of circulating miRNAs: biological function and basic transport carriers; extracellular cell communication process; roles as reliable cancer biomarkers and usage in targeted cancer therapy; and challenges for clinical application.

Keywords: biomarker; cancer; challenge; circulating; communication; miRNAs; therapy.

Figure 1

(1) Biological functions and transportation carriers of circulating miRNA; (2) Diverse ways of miRNAs in cell communication: direct fusion and endocytosis of extracellular vesicles (exosomes orMVs) (red arrow) or direct transfer through cell gap junction (green arrow) or the indirect identification of specific surface receptor (blue arrow). Abbreviations: Pre-miRNA, precursor miRNA; Pri-miRNA, primary miRNA; AGO, Argonaute; TRBP, transactivation-responsive RNA-binding protein; DGCR8, DiGeorge Syndrome Critical Region Gene 8; MVBs, multivesicular bodies; NPM1, nucleophosmin 1.