PDCD1 and neoplasm: In order to improve the efficacy of tumor immunotherapy, ICB-based combination therapies have been developed and have demonstrated promising activity, including combinations of anti-PD1/PD-L1 with chemotherapy, other immune checkpoint inhibitors (such as CTLA4, LAG3, and TIM3), cetuximab, CAR-T, EZH2 inhibitors, TGF-β inhibitors, and cancer vaccines [41,42,43,44].