Role of Tunneling Nanotubes in Arachidonic Acid Transfer and Macrophage Function Reprogramming in Intrahepatic Cholangiocarcinoma.

Tumor-associated macrophages (TAMs) play a crucial role in tumor progression within the tumor microenvironment (TME) through phenotypic plasticity and functional modulation. While tunneling nanotubes (TNTs) mediate intercellular communication, their role in shaping TAMs phenotypes and function remains unclear. This study explores how TNTs facilitate the transfer of tumor-derived materials, particularly fatty acids, to TAMs, affecting macrophage polarization and function. Single-cell RNA sequencing identified heterogeneous macrophage subpopulations in the TME. Enrichment analysis pinpointed key substances transferred via TNTs. Lipidomics and metabolomics analyzed the fatty acids involved. In vitro and in vivo experiments validated TNTs-mediated material transfer, and transcriptomic analysis revealed the associated signaling pathways. TNTs are the primary route for transferring tumor-derived fatty acids, notably arachidonic acid (AA), to macrophages. This transfer reprogrammed TAMs from anti-tumor CD5L(+) to pro-tumor TREM2(+) phenotypes, increasing CCL18 secretion, reducing phagocytic activity, and impairing CD8(+) T cell proliferation. Mechanistically, AA activated the PI3K-AKT pathway, driving TAMs polarization. These findings are confirmed in xenograft models, where TNTs-induced TAMs exhibited enhanced pro-tumor properties. TNTs-mediated transfer of tumor-derived AA reprograms TAMs via PI3K-AKT activation, promoting immune suppression and tumor progression, highlighting TNTs and PI3K-AKT as potential therapeutic targets in iCCA.