Metabolic-Immune Reprogramming via CuZnS@BSA Nanoregulators to Overcome Resistance in Triple-Negative Breast Cancer.

RATIONALE: Since the therapeutic resistance of triple-negative breast cancer (TNBC) is mainly attributable to excessive glutathione (GSH) accumulation and its 'cold' immune landscape, we designed biomimetic CuZnS@BSA nanoregulators that exploit a pH-triggered 'disarm-and-attack' cascade, thereby initiating a well-defined, sequential therapeutic process in the acidic tumor microenvironment. METHODS: Biomimetic CuZnS@BSA nanoclusters were synthesized via a self-assembly method. Their pH-responsive release kinetics and synergistic therapeutic mechanisms (GSH depletion, ROS generation, and cuproptosis) were systematically evaluated in vitro using 4T1 cells. In vivo anti-tumor efficacy, immune microenvironment remodeling, and anti-metastatic effects were investigated in subcutaneous and lung metastasis TNBC mouse models, both alone and in combination with PD-L1 blockade. RESULTS: The platform first releases H2S to deplete intracellular GSH, thus removing the major antioxidant defenses of the tumor, then follows with the release of Cu2+ to induce cuproptosis, which effectively bypasses the apoptosis resistance commonly seen in TNBC. In addition, the released Zn2+ acts as an immune modulator by promoting the recognition of leaked mitochondrial DNA. This activates the cGAS-STING signaling pathway, and in vivo experiments clearly showed that it remodels the tumor microenvironment in a highly favorable manner, characterized by increased CD8+ T cell infiltration and enhanced dendritic cell maturation. CONCLUSION: Combining this nanoregulator with PD-L1 blockade led to potent suppression of both subcutaneous tumor growth and lung metastasis, thus providing a direct, elegant link between metabolic reprogramming and systemic immune activation for TNBC therapy.