While PD-L1 expression correlates with response in cancers such as NSCLC, ESCC, and urothelial carcinoma, it has shown inconsistent or no correlation in others, including breast cancer, glioblastoma, and HNSCC (105, 106, 114, 136, 139, 146, 164). The gene discussed is CD274; the disease is head and neck squamous cell carcinoma.