PDCD1 and cancer: This concept suggests that the ability of cancers to progress and grow could be impaired by loss of immunogenicity; however, this perception alone contradicts another evidence that T-cells are adequately activated to enhance their cancer recognition by the administration of immune-activating cytokines or immune checkpoints releases such as programmed cell death-1 (PD-1) or cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) that leads to robust tumor responses in patients and mice (Chambers et al., 2001; Pardoll, 2012).