PDCD1 and lung cancer: Moreover, polymorphisms observed at several T cell immune checkpoints, such as B- and T-lymphocyte attenuator (BTLA), CTLA-4, and PD-1, which are known for their immunosuppressive roles, have been implicated in modulating susceptibility to lung cancer (Wang J. et al., 2021; Andrzejczak et al., 2022).