CD8A and nasopharyngeal carcinoma: To find the mechanism of resistance to PD-1/PD-L1 inhibitors in NPC, we studied the co-expression status of the NKG2D ligand family, a group of activating molecules expressing on the surface of activated CD8+ T-lymphocytes, when IFN-γ is up-regulating the expression of PD-L1 in NPC.