HAAO and nasopharyngeal carcinoma: In summary, we discovered that EVs secreted by NPC could alter macrophage function and promote metastasis; EVs secreted by NPC with high SCARB1 expression increased HAAO expression in M1 macrophages, leading to increased ferroptosis of M1 macrophages and decreased infiltration in the tumor microenvironment; meanwhile, SCARB1 in EVs increased CYP1B1 expression in M2 macrophages, reducing phagocytosis, and both promoted metastasis synergistically (Table 1).