Cell-intrinsic PD-L1 signaling drives immunosuppression by myeloid-derived suppressor cells through IL-6/Jak/Stat3 in PD-L1-high lung cancer

BACKGROUND: Some patients with non-small-cell lung cancer (NSCLC) benefit from immune checkpoint inhibitors (ICIs) despite programmed death-ligand 1 (PD-L1) expression. To address the mechanism of ICI resistance in PD-L1-positive NSCLC, we investigated the role of tumor-cell-intrinsic function of PD-L1 in interleukin (IL)-6-mediated immunosuppression. METHODS: Cohorts of NSCLC patients treated with ICI and public datasets were analyzed. PD-L1-overexpressing and PD-L1-knockdown NSCLC cells were submitted to RNA-seq, in vitro analyses, chromatin immunoprecipitation-qPCR, CUT&Tag, and biochemical assays. Human myeloid-derived suppressor cells (MDSCs) sorted from peripheral blood mononuclear cells were co-cultured with NSCLC cells and then assessed for their immunosuppressive activity on T-cells. Mouse Lewis lung carcinoma (LLC) cells with PD-L1 overexpression or knockdown were subcutaneously injected into wild-type or PD-1-knockout C57BL/6 mice in the presence of IL-6 and/or PD-1 blockade. RESULTS: CD8 T-cells. CONCLUSIONS: The tumor-cell-intrinsic function of PD-L1 drives immunosuppression and tumor progression through the PD-L1/Jak/Stat3/IL-6/MDSC axis. This pathway represents a potential therapeutic target to improve ICI efficacy in PD-L1-high NSCLC.