IFN-γ secreted by the infiltrated CD8+ CTLs was required for PD-L1 induction, indicating that overexpression of PD-L1 within the tumor microenvironment functioned as a negative feedback mechanism, which represents a compensatory immune response by CD8+ CTLs and IFN-γ within the tumor microenvironment [34,35]. Here, CD274 is linked to neoplasm.