PDCD1 and neoplasm: Immune checkpoint blockade therapy is an emerging antitumor therapy in recent years that targets and blocks suppressive immune checkpoints in tumors, such as CTLA4 and PD1, and their ligands PD-L1 and CD86 in tumors to break the negative feedback inhibition of immune checkpoints against tumor immunity, thereby inducing the immune system to kill tumors, and has achieved excellent therapeutic effects in a variety of cancers (50).