CTLA4 and cancer: CircWDR25 (hsa_circ_004310) and circQSOX1 (hsa_circ_0015497) could also promote the increased expression of CTLA-4 and PD-L1 through the sponge mechanism in hepatocellular carcinoma and colorectal cancer, respectively, thus driving tumor immune escape and promoting cancer progression [293, 294].