IFN??-induced Immunosuppression in Lung Carcinoma is Mediated by an Environmental Chemical Receptor (AhR) through PD-L1 and IDO Control (cmt167 scRNA)

While immunotherapy has shown efficacy in non-small cell lung cancer (NSCLC) patients, many respond only partially or not at all. One limitation in improving outcomes is the lack of a complete understanding of factors regulating immune checkpoint targets. Here, we sought to address a possible link between an environmental chemical receptor implicated in NSCLC and immune regulation, the aryl hydrocarbon receptor (AhR), and a known but counterintuitive mediator of immunosuppression, IFN??, in regulation of two immune checkpoints, PD-L1 and the IDO1, in lung adenocarcinoma (LUAD). To this end we used AhR, PD-L1, and IFN??R gene-edited LUAD cell lines, a syngeneic LUAD mouse model, bulk- and single cell-RNA sequencing of LUADs and tumor-infiltrating leukocytes, and existing human transcriptomic databases. The data demonstrate that: 1) the AhR regulates both PD-L1 and IDO1 in murine and human LUAD cells, 2) AhR-driven IDO1 results in production of Kyn which likely mediates an AhR?IDO1?Kyn?AhR amplification loop, 3) the previously characterized induction by IFN??of PD-L1 and IDO is mediated by the AhR, 4) transplantation of LUAD cells in which the AhR is deleted results in long-term tumor immunity in approximately half of the mice; slow growing tumors in the other half exhibit significantly higher densities of CD4+ and CD8+ T cells expressing immunocompetence markers, and 5) deletion of either IFN??R1 or PD-L1 does not provide the same level of immune protection as AhR deletion. The data definitively link IFN??- mediated immunosuppression to the AhR and support the targeting of the AhR in the context of LUAD. Overall design: To investigate the presence or absence of Ahr in malignant cells of the lung in regards to the functions related to tumorogenicity and immune signalling using an average of 5,792 viable cells from wildtype tumors from two mice and an average of 3,173 viable cells from AhR-KO tumors