PDCD1 and cancer: When anti-PD-1 binds with PD-1 on the T cell membrane surface, or anti-PD-L1 binds with PD-L1 on the tumour cell and antigen-presenting cell (APC) membrane surface, naïve T cell will be activated, expanded, and released perforin and granzyme which causing enhanced tumour killing.42 In parallel, conditional deletion or blockade of PD-1 in Treg cells can enhance antitumour immunity through weakening Treg cell proliferation and infiltration in the tumour microenvironment.43 The evidence of ICB efficacy targeting PD-1/PD-L1 in clinical trials has become discussed among multiple cancers.