Novel insights into exosomal circular RNAs: Redefining intercellular communication in cancer biology

Exosomes, a special type of membrane‐bound extracellular vesicle regarded as an ideal carrier for intercellular messages, play an essential role in intercellular communication both locally and systematically. Recent studies have reported that circular RNAs (circRNAs), members of the noncoding RNA family, are abundant and stable in exosomes. As an essential mediator of intercellular communication within cancer cells or between cancer cells and noncancerous cells, exosomal circRNAs participate in multiple aspects of cancer. In this review, we summarize the biogenesis, properties and functions of exosomal circRNAs. In particular, we describe their intercellular transfer in the tumour microenvironment and associate their biological functions with different phenotypes of cancer. Finally, we discuss potential clinical applications in the future.