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

Abstract

Epstein-Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC) is characterized by a highly infiltrated, yet immunosuppressive, tumor microenvironment (TME) in which tumor-associated macrophages (TAMs) play a central role in tumor progression. In this study, we identified exosome-mediated delivery of the EBV oncoprotein LMP1, which acts via induction of leukemia inhibitory factor (LIF), as a key mechanism driving immunosuppressive macrophage polarization. Immunohistochemistry revealed that, in addition to tumor cells, LIF is primarily expressed by stromal TAMs and correlates with poor prognosis. We demonstrated that LMP1-containing exosomes are internalized by macrophages, leading to NF-{kappa}B-dependent upregulation of LIF and polarization toward an immunosuppressive M2d-like phenotype. These macrophages exhibit impaired anti-tumor activity and promote tumor proliferation and vascular dissemination in a LIF-dependent manner. Single-cell transcriptomic analyses of exosome-treated NPC biopsies revealed transcriptional reprogramming across tumor, myeloid, and lymphoid compartments impacting epithelial-mesenchymal transition (EMT); extracellular matrix (ECM) remodeling in tumor cells; immunosuppressive signaling (e.g., CD163 anti-inflammatory and VEGF signaling in macrophages); and enrichment of immune checkpoints and pathways, including PD-1, TGF{beta}-SMAD, and NF-{kappa}B-associated pathways in T cells. Exosome treatment increased expansion of CCL18+-TAMs and expression of CTLA4 in regulatory T cells and exhausted T cells. Immunohistochemistry further confirmed a positive correlation between expression of LIF and CTLA4 in NPC tumors and an inverse correlation between LIF and GZMB/CD8A. These findings define an exosome-driven LMP1-LIF axis that orchestrates immune suppression in NPC and suggest potential targets for restoring anti-tumor immunity.