Four recent publications reported the role of PD-L1 expression on host versus malignant cells within the tumor for PD-1/PD-L1 checkpoint blockade therapy. All four research groups harmoniously report: PD-L1 expressed by both host as well as tumor cells are capable of suppressing T cell functions. Thus, checkpoint therapy can be effective, if malignant cells do not express PD-L1.
Keywords: Biomarker; PD-1; PD-L1; checkpoint blockade; expression; immunotherapy.