Macrophages and macrophage extracellular vesicles confer cancer ferroptosis resistance via PRDX6-mediated mitophagy inhibition.

Ferroptosis has emerged as a promising therapeutic target in cancer therapy, with the tumor microenvironment (TME) playing a pivotal role in regulating ferroptosis. Although macrophages contribute to ferroptosis regulation within TME, the underlying mechanisms remain unclear. In this study, we demonstrate that macrophages consistently attenuate GPX4 inhibitor-induced lipid peroxidation and cell death in various tumor cell lines, whereas their resistance to cysteine transport inhibitor-triggered ferroptosis varies across cell types. This tumor protection from ferroptosis is mediated through macrophage-tumor cell contact and the delivery of macrophage-derived extracellular vesicles (Mφ-EV). Transcriptomic and proteomic analyses revealed that macrophages and Mφ-EV enhance glutathione metabolism in tumor cells. Notably, Mφ-EV are uniquely enriched with the glutathione metabolism-related protein PRDX6. Mechanistically, the glutathione peroxidase activity of PRDX6 elevates intracellular reduced glutathione, suppresses lipid peroxidation, and thereby mitigates ferroptosis. Furthermore, macrophage-derived PRDX6 reduces mitochondrial superoxide accumulation, alleviates ferroptosis-induced mitophagy, and enhances tumor cell viability, ultimately promoting tumor growth. Together, our findings provide a novel mechanism of ferroptosis resistance in TME, wherein macrophages confer tumor cell resilience by bypassing GPX4 inhibition.