The function and mechanism of circular RNAs in gastrointestinal tumours.

Gastrointestinal tumours are tumours that originate in the digestive tract and have extremely high morbidity and mortality. The main categories include: oesophageal, gastric, and colorectal cancers. Circular RNAs are a new class of non-coding RNAs with a covalent closed-loop structure without a 5' cap or a 3' poly A tail, which can encode a small amount of polypeptide. Recent studies have shown that circRNAs are involved in multiple biological processes during the development of gastrointestinal tumours including proliferation, invasion and metastasis, radio- and chemoresistance, and inflammatory responses. Also, the clinical and pathological characteristics of the patient, such as staging and lymph node metastasis, are closely associated with the expression level of circRNAs. Further investigation of the function and the role of circRNAs in the development of gastrointestinal tumours will provide new directions for its clinical diagnosis and treatment.