A copper-based RNAi nanocomplex unleashes immunogenic ferroptosis by reversing metabolic adaptation and suppressing extracellular GPX4

Copper exerts opposing effects on immunogenic ferroptosis. • Driving PUFA remodeling, siC@CuPP overcomes copper-induced metabolic ferroptosis resistance. • Copper-mediated inhibition of extracellular GPX4 release is preserved in siC@CuPP. • siC@CuPP-mediated potent antitumor immunity suppresses primary tumors and distant metastasis. Ferroptosis is an immunogenic form of regulated cell death with considerable potential for cancer immunotherapy, yet its efficacy is frequently limited by adaptive resistance mechanisms. Here, we uncover a previously unrecognized bidirectional role of copper-based ferroptosis inducers in breast cancer. On the one hand, copper suppresses the release of extracellular GPX4, an immunosuppressive damage-associated molecular pattern, preserving the immunostimulatory effects of ferroptotic cell death. On the other hand, copper-induced ferroptotic stress activates carnitine palmitoyltransferase 1A (CPT1A)-dependent fatty acid oxidation, which limits polyunsaturated fatty acid (PUFA) availability and reduces ferroptosis susceptibility. To overcome this adaptive metabolic resistance, we developed siC@CuPP, a polyethylenimine-modified copper-doped polypyrrole nanocomplex that delivers Cpt1a siRNA while retaining the intrinsic ferroptosis-inducing activity of the CuPPy core. siC@CuPP efficiently silenced Cpt1a , inhibited fatty acid oxidation-driven PUFA consumption, promoted lipid remodeling, and impaired NADPH replenishment, thereby enhancing oxidative stress and ferroptosis sensitivity. Concurrently, copper-mediated suppression of extracellular GPX4 relieved ferroptosis-associated immunosuppression and facilitated dendritic cell activation. These coordinated effects established a positive feedback loop between immunogenic ferroptosis and antitumor immunity through interferon-γ–ACSL4 signaling. In an orthotopic 4T1 triple-negative breast cancer model, systemic administration of siC@CuPP elicited robust antitumor immune responses, significantly suppressing primary tumor growth and pulmonary metastasis. Collectively, this work identifies CPT1A-dependent metabolic adaptation and extracellular GPX4-mediated immunosuppression as two notable barriers to immunogenic ferroptosis and provides a coordinated strategy for overcoming both, thereby amplifying ferroptosis-driven cancer immunotherapy. Download: Download high-res image (577KB) Download: Download full-size image