PDCD1 and neoplasm: These factors are related to tumor cell escape mechanisms, for example, through the skewed regulation of the programmed death-ligand 1/programmed cell death 1 (PD-L1/PD-1) axis (Garcia-Diaz et al., 2017); this immune checkpoint promotes a break in T lymphocyte activation, leading to immune response suppression and culminating in the impairment of cytokine production and lymphocyte cytolytic activity (Garcia-Diaz et al., 2017).