Glutathione-depleting mitochondria-targeting nanodrugs for stress amplification and immune activation via synergistic photodynamic therapy and cuproptosis

Multiple mitochondrial stress dysregulation represents an emergent mechanism for inducing tumor cell death. While photodynamic (PDT) and cuproptosis therapies can generate oxidative and proteotoxic stress respectively, their cooperativity and effects are hampered by the uncontrolled spatiotemporal interaction with glutathione (GSH) overexpressed in the tumor microenvironment. Here, we developed a GSH-depleting nanodrug for synergistic mitochondria-targeting PDT and cuproptosis, by co-loading mitochondria-targeting photosensitizer PpIX-TPP with copper ionophore elesclomol (ES) into GSH-responsive dextran-based nanoassemblies. The interaction between GSH in tumor cells and disulfide bonds in nanodrugs led to GSH depletion, thereby triggering the responsive release of the loaded drugs and reducing the limitation of GSH on therapeutic effectiveness. The released PpIX-TPP effectively targeted mitochondria, inducing PDT effects under laser irradiation, causing oxidative stress and further reducing GSH levels. ES carried copper ions into tumor cells and selectively released them in mitochondria, inducing proteotoxic stress through cuproptosis and generating hydroxyl radicals via a Fenton-like reaction to cause extra oxidative stress. The orchestration of multiple mitochondrial stress pathways led to mitochondrial dysfunction, immunogenic cell death, and subsequent immune activation both in vitro and in vivo. This study provides a strategy for enhanced antitumor efficacy through mitochondrial stress amplification and immune activation. STATEMENT OF SIGNIFICANCE: Combining light-activated photodynamic therapy (PDT) with copper-dependent cell death (cuproptosis) is promising for treating melanoma. However, tumors often overexpress glutathione (GSH), which neutralizes reactive oxygen species generated by PDT and blocks the cancer-killing effects of copper, thus compromising both therapeutic modalities. Poor targeting further impairs the treatment effectiveness. Herein, we developed a smart drug delivery system that combines mitochondria-targeting PDT with elesclomol-induced cuproptosis to improve the precision of treatment while depleting GSH to eliminate its negative impact on the therapeutic effect. Our nanodrugs induce abnormal amplification of mitochondrial stress in cancer cells, triggering their self-destruction and activating the immune system to attack tumors. This work provides a new strategy to enhance melanoma treatment through mitochondrial stress amplification and immune activation.