Circular RNA: A promising new star for the diagnosis and treatment of colorectal cancer

BACKGROUND: Colorectal cancer (CRC) is one of the most common malignant tumors of the digestive tract. According to the research of circular RNAs in the CRC field, compared with linear RNAs, circular RNAs are a special type of noncoding RNA that are covalently closed circular structures, which have no 5' cap structure and 3' polyA tail and are not affected by RNA exonuclease and actinomycin D. BIOLOGICAL FUNCTIONS: Notably, circular RNAs have a high degree of stability and potential effect on gene regulation. Meanwhile, circular RNAs are involved in the sponge action of microRNAs and mediate protein translation and direct binding, alternative splicing, and histone modification. RELATIONSHIPS WITH CRC: Studies have shown that circular RNAs are related to the proliferation, invasion, recurrence, metastasis, ferroptosis, apoptosis, and chemotherapy resistance of CRC. CONCLUSIONS: This article provides a brief review based on the source, structural characteristics, mechanisms, biological functions of circular RNAs, and the relationships between CRC.