The interaction of programmed death-1 (PD-1) and it's ligands (PD-L1) is an important immune checkpoint and blockade of PD-1/PD-L1 axis with antibodies against PD-L1 showed promising anti-tumor activity in clinical practice. However, only a small percentage of patients can benefit from PD-L1 mAbs. Small molecular kinase inhibitors have been widely used as antitumor drugs for many years, and several kinase inhibitors were recently reported to inhibit the expression of PD-L1. However, the connections between PD-L1 expression and kinase inhibitors were not thoroughly elucidated. Herein, we set up a novel and robust screening system to identify small molecular compounds which downregulate the PD-L1 level of tumor cell based on Odyssey on/in cell quantitative immunoblots technology. A collected kinase inhibitor library was screened and 14 hits were further confirmed by western blot and flow cytometry. System biological analysis and further bio-assay identified a synergy combination between KU-60019 and Vacquinol-1 in downregulation of PD-L1. Taken together, the work established a novel method to screen the PD-L1 down-regulators using kinase inhibitors library, thus providing new clues for the application of kinase inhibitors in cancer immunotherapy.
Keywords: Combination therapy; Immunotherapy; Kinase inhibitor; PD-L1.
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