In the past few decades, the roles of miRNAs in regulating the expression of the PD-1/PD-L1 immune checkpoint and the sensitivity of tumours to chemotherapy drugs have been well studied [87, 88], revealing that circRNAs contribute to immune escape through a circRNA-miRNA-PD-1/PD-L1 axis (Fig. 1c). This evidence concerns the gene CD274 and neoplasm.