Recently, immune checkpoint inhibitors, including CTLA-4 and programmed cell death protein 1 (PD-1)/programmed cell death 1 ligand 1 (PD-L1) inhibitors, which reverse the signals from the immunosuppressive tumor microenvironment (TME), are being investigated as potential treatment modalities (8, 9). The gene discussed is PDCD1; the disease is neoplasm.