Abstract

Background Tumor-associated macrophage (TAM) polarization is a central determinant of head and neck squamous cell carcinoma (HNSC) progression. However, whether direct mitochondrial transfer governs TAM functional reprogramming in the tumor microenvironment (TME) remains unclear. Methods By integrating bioinformatics analyses with in vitro co-culture systems, in vivo tumor models, and clinical specimens, we systematically investigated intercellular mitochondrial transfer between squamous carcinoma cells and macrophages. Functional, metabolic, and molecular assays were performed following genetic and pharmacological inhibition of tunneling nanotubes (TNTs). Results We demonstrated that squamous carcinoma cells transfer mitochondria to macrophages via TNTs, driving their polarization toward an immunosuppressive M2 phenotype. Mechanistically, the transferred mitochondria reprogram TAM metabolism by promoting citrate-dependent lipid biosynthesis, leading to lipid accumulation. Reciprocally, lipid-laden TAMs potentiated epithelial–mesenchymal transition and malignant progression of tumor cells, forming a feed-forward pro-tumor circuit. Disruption of TNT formation effectively abrogated mitochondrial transfer, reversed TAM immunosuppression, and restored anti-tumor immunity. Notably, TNT blockade exhibited a synergistic therapeutic effect when combined with anti-PD-1 immunotherapy in vivo . Conclusions In this study, we identifine TNT-mediated mitochondrial transfer as a previously underappreciated mechanism driving TAM metabolic and phenotypic reprogramming in HNSC. Targeting this intercellular organelle communication axis represents a compelling and translationally relevant strategy to enhance immunotherapeutic efficacy.