The emerging roles of circRNAs in cancer and oncology

Over the past decade, circular RNAs (circRNAs) have emerged as a large class of primarily non-coding RNA molecules, many of which have key roles in cancer development and progression through diverse mechanisms of action. CircRNAs often have tissue-restricted and cancer-specific expression patterns, and accumulating data suggest that these molecules are of potential clinical relevance and utility. In particular, circRNAs have strong potential as diagnostic, prognostic and predictive biomarkers, which is underscored by their detectability in liquid biopsy samples such as in plasma, saliva and urine. However, technical issues in the detection and assessment of circRNAs as well as biological knowledge gaps need to be addressed to move this relatively young field of research forward and bring circRNAs to the forefront of clinical practice. Herein, we review the current knowledge regarding circRNA biogenesis, regulation and functions in cancer as well as their clinical potential as biomarkers, therapeutic agents and drug targets. Circular RNAs (circRNAs) are a novel class of primarily non-coding RNAs with increasingly recognized roles in cancer development and progression through diverse mechanisms of action. Herein, the authors review the current understanding of circRNA biogenesis, regulation, physiological functions and pathophysiological roles in cancer. They also discuss the clinical potential of circRNAs as biomarkers, therapeutic agents and drug targets in oncology as well as research controversies, technical issues and biological knowledge gaps that need to be addressed before this promise can be realized.