Their novel mechanism is rooted in targeting small proteins, cytotoxic T-lymphocyte antigen 4 (CTLA-4)/programmed cell death protein 1 (PD-1), which are expressed on T cells, B cells, and innate immune cells and programmed cell death ligand-1 protein (PD-L1), which is expressed on cancer cells [3,4]. This evidence concerns the gene PDCD1 and cancer.