Immune checkpoint blockade by targeting the programmed death-ligand 1 (PD-L1)/programmed cell death protein 1 (PD-1) pathway has demonstrated remarkable effectiveness in treating different types of cancer, such as melanoma, non-small cell lung cancer, renal cell carcinoma, and bladder cancer [1,2,3,4,5,6,7]. The gene discussed is PDCD1; the disease is cancer.