Exosomal <scp>HMGB1</scp> Orchestrates <scp>NSCLC</scp> Progression and Immunosuppressive Macrophage Polarisation Through the <scp>TLR4</scp> / <scp>NF</scp> ‐ <scp>κB</scp> / <scp>IL</scp> ‐6/ <scp>STAT3</scp> Signalling Cascade

High mobility group box 1 (HMGB1), a prototypical alarmin and chromatin-binding protein, has emerged as a critical mediator of tumour-associated inflammation and immune regulation. Although its soluble form has been implicated in various malignancies, the functional contribution of HMGB1 encapsulated within exosomes remains incompletely understood, particularly in the context of non-small-cell lung cancer (NSCLC). We profiled exosomal HMGB1 levels in the peripheral blood of 80 clinically annotated NSCLC patients and correlated its abundance with metastatic burden and survival outcomes. Functional experiments using HMGB1-overexpressing NSCLC cell lines were conducted to assess proliferative, migratory and stemness-associated phenotypes in vitro, alongside tumorigenicity and drug responsiveness in vivo. Mechanistic interrogation of the TLR4/NF-κB/IL-6/STAT3 signalling axis was performed via western blotting, ELISA, immunofluorescence and targeted pharmacologic inhibition. The impact of exosomal HMGB1 on macrophage plasticity was evaluated using THP-1-derived macrophage models, and therapeutic relevance was validated in murine tumour models under immunotherapy and chemotherapy regimens. Circulating exosomal HMGB1 levels were significantly elevated in patients with metastatic NSCLC and strongly correlated with poor prognosis. Exosomal HMGB1 markedly enhanced tumour cell proliferation, motility and self-renewal capacity, while promoting chemoresistance and immune evasion. Mechanistically, HMGB1-enriched exosomes activated the TLR4/NF-κB axis, elevating IL-6 secretion and subsequent STAT3 phosphorylation. These effects were further linked to the polarisation of macrophages towards an immunosuppressive M2 phenotype. Therapeutically, cotargeting STAT3 signalling overcame exosomal HMGB1-mediated resistance to paclitaxel in vivo. Our findings delineate a previously unrecognised exosome-mediated mechanism by which HMGB1 drives NSCLC progression and modulates the tumour immune microenvironment. Exosomal HMGB1 not only serves as a potential prognostic biomarker but also represents a tractable target for enhancing the efficacy of immuno- and chemotherapeutic strategies in NSCLC.