CD274 and nasopharyngeal carcinoma: In this study, we evaluated expression of cancer cell-intrinsic PD-1, PD-L1 and p-S6 proteins in 281 cases of NPC and 51 cases of non-cancerous nasopharyngeal epithelia, as well as in 24 primary NPC and their matched metastases, to illustrate the relationship between expression of cancer cell-intrinsic PD-1, PD-L1 and p-S6 proteins and their clinical significances in NPC.