This includes immunosuppressive cytokines and immune checkpoint molecules that are expressed on T cells such as programmed cell death 1 (PD-1), programmed death ligand 1 (PD-L1), cytotoxic T- lymphocyte-associated protein 4 (CTLA-4), T cell immunoglobulin and mucin domain 3 (TIM3), and lymphocyte-activation gene 3 (LAG3), are found to be upregulated in cancer and are responsible for tumor immune evasion [6]. Here, PDCD1 is linked to cancer.