Zn2+/Ca2+ co-overloaded nano-modulator amplifies reactive oxygen species to potentiate shikonin-induced necroptosis against triple‑negative breast cancer.

Triple‑negative breast cancer (TNBC) poses substantial therapeutic challenges due to its innate resistance to apoptosis and lack of clearly characterized targets. Since necroptosis is the alternate pathway when apoptotic resistance develops, inducing necroptosis in tumor cells has become a promising therapeutic approach. Herein, this study proposes a calcium ions (Ca2+) and zinc ions (Zn2+) co-loaded biodegradable carrier designed to deliver shikonin (SKN) for enhancing necroptosis of TNBC based on amorphous calcium carbonate nanoparticles (Zn‑Ca@SKN NPs). Under the acidic microenvironment of TNBC, Zn-Ca@SKN NPs quickly degrade to boost the level of intracellular Ca2+, Zn2+, and SKN. The overloaded Ca2+ in mitochondria efficiently causes the extra H2O2 generation through the TCA cycle. Then, released Zn2+ ions catalyze H2O2 into hazardous hydroxyl radical (•OH) through Fenton-like reaction. On the one hand, the increased high level of intracellular reactive oxygen species (ROS) enhances the efficacy of SKN-triggered necroptosis to generate the necroptotic body. Conversely, ROS activates NOD-like receptors (NLRs) to release damage-associated molecular patterns (DAMPs). Subsequently, in-situ produced necroptotic bodies and DAMPs promote dendritic cells (DCs) maturation, antigen presentation, and cytotoxic CD8+ T cells activation, resulting in an efficient anti-tumor immune response for TNBC. Collectively, this study demonstrates a viable nanoplatform to overcome the apoptotic resistance of TNBC via combined necroptosis-immunotherapy.