Ferroptosis-dependent small extracellular vesicles ULK1 enhances mitophagy and suppresses breast cancer migration.

backgroundBreast cancer progression is closely influenced by the tumor microenvironment, including macrophage polarization. Small extracellular vesicles (sEVs) derived from tumor cells serve as key mediators of intercellular communication that regulate immune responses. Ferroptosis, characterized by iron-dependent lipid peroxidation, plays a role in tumor progression. However, whether ferroptosis alters the cargo of breast cancer cell-derived sEVs and affects macrophage function remains largely unknown.

resultsIn this study, we identify that sEVs derived from ferroptotic breast cancer cells (Fer-sEVs) are enriched in ULK1 and functionally suppress macrophage M2 polarization. Mechanistically, Fer-sEVs-delivered ULK1 promotes mitophagy in macrophages, thereby inhibiting M2-associated pro-tumoral phenotypes. Knockdown of ULK1 in donor cells abrogated this effect, while autophagy induction by rapamycin reversed consequences of ULK1 depletion. Co-culture experiments revealed that Fer-sEVs-educated macrophages significantly suppressed breast cancer cell migration, whereas ULK1-deficient Fer-sEVs restored migratory capacity. Furthermore, hnRNPA2B1 was identified as the key RNA-binding protein that recognizes EXO-motifs within the ULK1 3’ UTR and mediates its selective packaging into sEVs during ferroptosis. Silencing hnRNPA2B1 reduced ULK1 expression in sEVs.

conclusionTogether, our findings reveal a novel ferroptosis-sEVs-mitophagy axis, in which hnRNPA2B1-mediated sEVs ULK1 delivery enhances mitophagy and reprograms macrophage polarization, ultimately restraining breast cancer migration. This mechanism providing new insights into ferroptosis-based intercellular communication and identifying potential therapeutic targets for breast cancer metastasis.