PDCD1 and hepatocellular carcinoma: Targeting this axis with a DPP4 inhibitor like sitagliptin, combined with anti-PD-1 therapy, may enhance immune responses in HCC patients.232 Similarly, circNCOA3 in CRC sponges miR-203a-3p to increase CXCL1 expression, leading to immune escape and PD-1 blockade resistance.