Exosomal circRNAs: A new star in cancer

As a disease that seriously endangers human health, cancer still lacks effective treatment because of its complicated mechanism of action. Currently, an emerging class of RNAs, named circular RNAs (circRNAs), has been found to be closely related to cancer. CircRNAs have a stable closed loop structure which would be hardly degraded in blood or body fluids. Exosomes are found naturally in a variety of cells, mediating cell-to-cell communication, or participating in multiple processes of tumor development. Researchers have found that abnormally expressed circRNAs may be associated with the occurrence and development of malignancies. As a kind of exosome-derived non-coding RNAs, exosomal circRNAs have also played important roles in cancer progression and acted as diagnostic and prognostic biomarkers for cancer, and thus arousing more and more attention. This article reviews the functions, mechanisms and values of the exosomal circRNAs in tumors in order to provide new ideas and novel biomarkers for the diagnosis and treatment of cancer.