[Circular RNAs and their roles in tumorigenesis].

Recently, with the development of RNA research techniques, a wide variety of circular RNAs (circRNAs) have been discovered and some of them are confirmed to have crucial biological functions. CircRNAs arise from exons (i.e. exonic circRNAs) or introns (i.e. intronic circRNAs). Acting as microRNA sponges or combining with proteins, circRNAs participate in the regulation of gene expression and influence the activity of some proteins. In addition, some circRNAs even encode proteins. More importantly, several circRNAs play a key role in the occurrence and progression of some tumors, including stomach, liver, colon, breast, cervical, and ovarian cancers. Therefore, circRNAs may be a novel type of diagnostic marker and therapeutic target of cancers.