Subverting the adaptive immune resistance mechanism to improve clinical responses to immune checkpoint blockade therapy.

The correlation between tumor-infiltrating lymphocyte (TIL)-expression of programmed cell death ligand 1 (PD-L1) and clinical responsiveness to the PD-1 blocking antibody nivolumab implicates adaptive immune evasion mechanisms in cancer. We review our findings that tumor cell PD-L1 expression is induced by interferon γ (IFNγ) producing TILs. We provide a mechanistic rationale for combining IFNγ ⁺ T helper type 1 (Th1)-inducing cancer vaccines with PD-1 immune checkpoint blockade.