Blockade of CD93 in pleural mesothelial cells fuels anti-lung tumor immune responses

Background: CD93 reportedly facilitates tumor angiogenesis.However, whether CD93 regulates antitumor immunity remains undeciphered.Methods: Lung tumor tissues, malignant pleural effusions (MPEs) were obtained from lung cancer patients.Blood was obtained from healthy volunteers and lung cancer patients with anti-PD-1 therapy.Furthermore, p53 fl/fl LSL-Kras G12D , Ccr7 -/-, Cd93 -/-mice and CD11c-DTR mice were generated.Specifically, EM, NTA and western blotting were utilized to identify Tumor extracellular vesicles (TEVs).EV labeling, detection of EV uptake in vitro and in vivo, degradation of EV proteins and RNAs were performed to detect the role of TEVs in tumor progression.Pleural mesothelial cells (pMCs) were isolated to investigate related signaling pathways.Recombinant proteins and antibodies were generated to test which antibody was the most effective one to increase CCL21a in p-pMCs.RNA-Seq, MiRNA array, luciferase reporter assay, endothelial tube formation assay, protein labeling and detection, transfection of siRNAs and the miRNA mimic and inhibitor, chemotaxis assay, immunohistochemical staining, flow cytometry, Real-time PCR, and ELISA experiments were performed.Results: We show that CD93 of pMCs reduced lung tumor migration of dendritic cells by preventing pMCs from secreting CCL21, thereby suppressing systemic anti-lung tumor T-cell responses.TEV-derived miR-5110 promotes CCL21 secretion by downregulating pMC CD93, whereas C1q, increasing in tumor individuals, suppresses CD93-mediated CCL21 secretion.CD93-blocking antibodies (anti-CD93) inhibit lung tumor growth better than VEGF receptor-blocking antibodies because anti-CD93 inhibit tumor angiogenesis and promote CCL21 secretion from pMCs.Anti-CD93 also overcome lung tumor resistance to anti-PD-1 therapy.Furthermore, lung cancer patients with higher serum EV-derived miR-5193 (human miR-5110 homolog) are more sensitive to anti-PD-1 therapy, while patients with higher serum C1q are less sensitive, consistent with their regulatory functions on CD93.Conclusions: Our study identifies a crucial role of CD93 in controlling anti-lung tumor immunity and suggests a promising approach for lung tumor therapy.