Common inhibitory receptors such as programmed cell death-1 (PD-1), programmed cell death-ligand 1 (PD-L1), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), lymphocyte-activation gene 3 (LAG-3), and T cell immunoglobulin and mucin-domain containing-3 (TIM-3) play pivotal roles in dampening T cell activity within GBM [72]. Here, PDCD1 is linked to glioblastoma.