Programmed cell death protein 1 (PD-1)/PD-1 ligand 1 (PD-L1) blockade is a promising therapy for various cancer types, but most patients are still resistant. Therefore, a larger number of predictive biomarkers is necessary. In this study, we assessed whether a loss-of-function mutation of the interferon (IFN)-γ receptor 1 (IFNGR1) in tumor cells can interfere with anti-PD-L1 therapy. For this purpose, we used the mouse oncogenic TC-1 cell line expressing PD-L1 and major histocompatibility complex class I (MHC-I) molecules and its TC-1/A9 clone with reversibly downregulated PD-L1 and MHC-I expression. Using the CRISPR/Cas9 system, we generated cells with deactivated IFNGR1 (TC-1/dIfngr1 and TC-1/A9/dIfngr1). In tumors, IFNGR1 deactivation did not lead to PD-L1 or MHC-I reduction on tumor cells. From potential inducers, mainly IFN-α and IFN-β enhanced PD-L1 and MHC-I expression on TC-1/dIfngr1 and TC-1/A9/dIfngr1 cells in vitro. Neutralization of the IFN-α/IFN-β receptor confirmed the effect of these cytokines in vivo. Combined immunotherapy with PD-L1 blockade and DNA vaccination showed that IFNGR1 deactivation did not reduce tumor sensitivity to anti-PD-L1. Thus, the impairment of IFN-γ signaling may not be sufficient for PD-L1 and MHC-I reduction on tumor cells and resistance to PD-L1 blockade, and thus should not be used as a single predictive marker for anti-PD-1/PD-L1 cancer therapy.

Department of Genetics and Microbiology Faculty of Science Charles University BIOCEV 252 50 Vestec Czech Republic

Department of Genetics and Microbiology Faculty of Science Charles University BIOCEV 252 50 Vestec Czech Republic Department of Cell Biology Faculty of Science Charles University BIOCEV 252 50 Vestec Czech Republic

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