In summary, we demonstrated for the first time that the DPP4 inhibitor, anagliptin, plays an anti-tumor role as an ROS scavenger by inhibiting macrophage differentiation and M2 macrophage polarization, and it can potentiate the anti-tumor effect of PD-L1 blockade in NSCLC. The gene discussed is CD274; the disease is non-small cell lung carcinoma.