PDCD1 and neoplasm: The lack of effector function and the upregulation of inhibitory receptors, such as programmed cell death-1 (PD-1), T cell immunoglobulin and mucin domain-3 protein (TIM-3), lymphocyte-activation gene 3 (LAG-3) and CD39, are signs of T cell failure in tumor-infiltrating T cells that are exhaustion (McLane, Abdel-Hakeem & Wherry, 2019; Miller et al., 2019; Schietinger et al., 2016).