Understanding the molecular pathways driving the acute antiviral and inflammatory response to SARS‐CoV‐2 infection is critical for developing treatments for severe COVID‐19. Here, we find decreasing number of circulating plasmacytoid dendritic cells (pDCs) in COVID‐19 patients early after symptom onset, correlating with disease severity. pDC depletion is transient and coincides with decreased expression of antiviral type I IFNα and of systemic inflammatory cytokines CXCL10 and IL‐6. Using an in vitro stem cell‐based human pDC model, we further demonstrate that pDCs, while not supporting SARS‐CoV‐2 replication, directly sense the virus and in response produce multiple antiviral (interferons: IFNα and IFNλ1) and inflammatory (IL‐6, IL‐8, CXCL10) cytokines that protect epithelial cells from de novo SARS‐CoV‐2 infection. Via targeted deletion of virus‐recognition innate immune pathways, we identify TLR7‐MyD88 signaling as crucial for production of antiviral interferons (IFNs), whereas Toll‐like receptor (TLR)2 is responsible for the inflammatory IL‐6 response. We further show that SARS‐CoV‐2 engages the receptor neuropilin‐1 on pDCs to selectively mitigate the antiviral interferon response, but not the IL‐6 response, suggesting neuropilin‐1 as potential therapeutic target for stimulation of TLR7‐mediated antiviral protection.

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Non-small cell lung carcinoma patients with epidermal growth factor receptor (EGFR) mutations are offered EGFR tyrosine kinase inhibitors (TKI) as first line treatment, but 20–40% of these patients do not respond. High expression of alternative receptor tyrosine kinases, such as Fibroblast growth factor receptor 1 (FGFR1), potentially mediates intrinsic EGFR TKI resistance. To study this in molecular detail, we used CRISPR-dCas9 Synergistic Activation Mediator (SAM) for up-regulation of FGFR1 in physiological relevant levels in the EGFR mutated NSCLC cell lines HCC827 and PC9 thereby generating HCC827gFGFR1 and PC9gFGFR1. The sensitivity to the TKI erlotinib was investigated in vitro and in a BALBc nu/nu mouse xenograft model. FGFR1 up-regulation decreased TKI-sensitivity in both NSCLC cell lines in the presence of the ligand fibroblast growth factor 2 (FGF2). Xenografts were established with PC9gFGFR1 cells and it was demonstrated that there was no significant difference in tumor size between TKI- and vehicle-treated PC9gFGFR1 tumors. This supports decreased TKI-sensitivity in NSCLC cells with FGFR1 up-regulation. Our study points to FGFR1 signaling being an intrinsic resistance mechanism abolishing TKI response in EGFR mutated NSCLC.

Background: Disease recurrence in localized lung adenocarcinoma is a major obstacle for improving the overall outcome of lung cancer. Thus, better prognostic biomarkers are needed to identify patients at risk. In order to clear cancer, immune detection of tumor cells is of vital importance. DNA-leakage into the cytosol and tumor environment is one important tumor-associated danger signal and cGAS is a pivotal DNAsensor that detects misplaced DNA and initiates an innate immune response. In this study, we investigate the cGAS-STING-pathway expression in tumor tissue and circulating immune cells from lung adenocarcinoma patients in relation to stage of disease and overall survival (OS).Methods: Gene expression was measured using target specific droplet digital polymerase chain reaction (ddPCR) assays in a cohort of 80 patients with lung adenocarcinoma and 45 patients suspected of lung cancer, but determined to be cancer-free. The expression values were correlated to stage of disease. For further exploration of stage dependent expression, we used a publicly available gene expression data set to stratify patients by stage and correlate gene expression to OS. Results:In both tumor tissue and peripheral blood mononuclear cells (PBMCs) from cancer patients, we observed differential expression of cGAS-STING pathway components compared to cancer-free individuals. Furthermore, cGAS-STING pathway expression was elevated in PBMCs from patients with localized disease (stage I and II) compared to patients with metastatic disease (stage III and IV). Survival analysis based on publicly available gene expression data sets demonstrated a superior OS for patients with localized disease and high levels of cGAS, STING and TBK1. Conclusions:The expression of the cGAS-STING pathway is stage dependent and high expression is correlated with localized adenocarcinoma. For patients with localized disease, high cGAS, STING and TBK1 expression correlated with improved OS and may be a potential biomarker for this patient subgroup.

Purpose: Checkpoint inhibitors have significantly improved treatment of metastatic melanoma. However, 40–60% of patients do not respond to therapy, emphasizing the need for better predictive biomarkers for treatment response to immune checkpoint inhibitors. Prorammed death-ligand 1(PD-L1) expression in tumor cells is currently used as a predictive biomarker; however, it lacks specificity. Therefore, it is of utmost importance to identify other novel biomarkers that can predict treatment outcome. Experimental design: We studied a small cohort of 16 patients with advanced-stage melanoma treated with first-line checkpoint inhibitors. Plasma samples were collected prior to treatment initiation and continuously during the first year of treatment. Circulating tumor DNA (ctDNA) level and the expression of ten inflammatory cytokines were analyzed. Results: We found that the ctDNA-level in a blood sample collected after 6–8 weeks of therapy is predictive for response to checkpoint inhibitors. Patients with undetectable ctDNA had significantly longer progression-free survival (PFS) compared with patients with detectable ctDNA (median 26.3 vs. 2.1 months, p = 0.006). In parallel, we identified that high levels of the cytokines monocyte chemoattractant protein 1 (MCP1) and tumor necrosis factor α(TNFα) in baseline blood samples were significantly associated with longer PFS compared to low level of these cytokines (median not reached vs. 8.2 months p = 0.0008). Conclusions: These findings suggest that the levels of ctDNA, MCP1, and TNFα in baseline and early follow-up samples can predict disease progression in metastatic melanoma patients treated with checkpoint inhibitors. Potentially, these minimally invasive biomarkers may identify responders from non-responders.