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.
Kleinovink, J. W., van Hall, T., Ossendorp, F., & Fransen, M. F. (2017). PD-L1 immune suppression in cancer: Tumor cells or host cells? OncoImmunology, 6(7), [e1325982]. https://doi.org/10.1080/2162402X.2017.1325982