ILT4 facilitates angiogenesis in non‐small cell lung cancer

Abstract Antiangiogenic therapy targeting VEGF‐A has become the standard of first‐line therapy for non‐small cell lung cancer (NSCLC). However, its clinical response rate is still less than 50%, and most patients eventually develop resistance, even when using combination therapy with chemotherapy. The major cause of resistance is the activation of complex bypass signals that induce angiogenesis and tumor progression. Therefore, exploring novel proangiogenic mechanisms and developing promising targets for combination therapy are crucial for improving the efficacy of antiangiogenic therapy. Immunoglobulin‐like transcript (ILT) 4 is a classic immunosuppressive molecule that inhibits myeloid cell activation. Recent studies have shown that tumor cell‐derived ILT4 drives tumor progression via the induction of malignant biologies and creation of an immunosuppressive microenvironment. However, whether and how ILT4 participates in NSCLC angiogenesis remain elusive. Herein, we found that enriched ILT4 in NSCLC is positively correlated with high microvessel density, advanced disease, and poor overall survival. Tumor cell‐derived ILT4 induced angiogenesis both in vitro and in vivo and tumor progression and metastasis in vivo. Mechanistically, ILT4 was upregulated by its ligand angiopoietin‐like protein 2 (ANGPTL2). Their interaction subsequently activated the ERK1/2 signaling pathway to increase the secretion of the proangiogenic factors VEGF‐A and MMP‐9, which are responsible for NSCLC angiogenesis. Our study explored a novel mechanism for ILT4‐induced tumor progression and provided a potential target for antiangiogenic therapy in NSCLC.