Epstein-Barr viral product-containing exosome facilitates LIF-associated immunosuppressive polarization of macrophage in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is characterized by Epstein-Barr virus (EBV) infection and severe immune cell infiltration. How tumor-derived EBV or viral products regulate macrophage polarization within NPC microenvironment remains to be explored. Here, we investigated the exosome-mediated intercellular communications between EBV ⁺ NPC cells and tumor-associated macrophages (TAMs). We demonstrate that leukemia inhibitory factor (LIF) expression correlates with poorer metastasis/recurrence-free survival in NPC patients. Immunohistochemical analyses revealed that LIF is highly expressed by both tumor cells and macrophages. The uptake of NPC-derived exosomes by human monocyte-derived macrophages induced an immunosuppressive polarization and enhanced LIF expression, exhibiting a reduced cytotoxicity against primary cancer cells. Blocking LIF suppressed the pro-tumor functions mediated by tumor-derived exosomes, in both in vitro and in vitro zebrafish xenografts model. Furthermore, single-cell transcriptomic analysis (scRNA-seq) suggested that tumor- derived exosomes remodeled the NPC microenvironment by increasing the proportion of a pro-tumoral TAM subtype, CCL18-MΦ. Intercellular analysis revealed that exosome-treated macrophages could modulate T cell cytotoxicity and promoting Treg-mediated immunosuppression. Collectively, EBV shapes the tumor microenvironment by driving macrophage toward an immunosuppressive phenotype via exosome cargos, facilitating a pro-tumoral niche and contribute to NPC progression.