Key immune checkpoints in ESCC, such as Programmed cell death protein 1 (PD-1), programmed death-ligand 1 (PD-L1), and cytotoxic T-lymphocyte antigen-4 (CTLA-4), are targeted by monoclonal antibodies, producing therapeutic effects (15). The gene discussed is PDCD1; the disease is esophageal squamous cell carcinoma.