Regulatory mechanisms and clinical perspectives of circRNA in digestive system neoplasms

A new star, circular RNA (circRNA), is a class of noncoding RNA with a stable cyclic structure. Exonic circRNA mainly exists in the eukaryotic cytoplasm. Intronic circRNAs (ciRNA) and exonic circRNAs with introns (EIciRNA) are found in the nucleus. Recent evidences showed the functional diversity of circRNAs, which could be microRNA (miRNA) sponges, interact with protein or translate into small peptide. Due to the change of human eating habits, digestive cancer remains one of the most common cancers worldwide and it is prone to metastasis. Increasing studies have found a number of circRNAs using RNA sequencing technology and displayed double roles of circRNA in digestive cancer. In this review, we surveyed the biogenesis and regulation of circRNAs, discussed circRNA functions and clinical applications (especially circRNAs in exosome) in digestive cancers, which implied that circRNAs could be as potential biomarkers in diagnosis and treatment of digestive cancers in the future.