CD8A and neoplasm: PD-L1 binding to PD-1 results in a pattern of inhibitory signals, which inhibits CD8+ T cells’ proliferation, thus blocking the antitumor immune response and hence favoring tumor growth and metastasis.27 PD-1 has been detected in tumor-infiltrating lymphocytes (TILs) present in the tumor microenvironment, where PD-L1 aberrant expression is associated with a poor prognosis in several human tumors.28, 29 Taube et al.30 demonstrated that the expression of PD-L1 in tumor cells and tumor-infiltrating immune cells was highly correlated with PD-1 expression in infiltrating lymphocytes.