CD274 and neoplasm: Despite that intrinsic cellular changes in tumorigenesis may be the prime mover of constitutive expression of PD-L1 followed by immune evasion [14], increasing evidence indicates that upregulation of PD-L1 expression is inducible by infiltrative immune signals, including TILs, chemokines and pro-inflammatory/anti-inflammatory cytokines, as an adaptive response to anti-tumor immunity [15].