PD-L1 is a diverse molecule regulating both tumor-intrinsic signaling and adaptive immunosuppression

PD-L1 expression can be constitutive and inducible. Constitutive expression is dependent upon cell genomics. Deleterious gene mutations influence cell signaling with downstream effects on PD-L1 expression levels. Inducible PD-L1 expression is dependent upon exposure of cells to IFNγ, TNFα, IL-1α, and IL-1β via TLRs or IFN receptors in the ERK and IFNγ signaling networks (1,4).