Mitochondria-targeted manganese-based mesoporous silica nanoplatforms trigger cGAS-STING activation and sensitize anti PD-L1 therapy in triple-negative breast cancer.

Activation of the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway could effectively initiate antitumor immunity in triple-negative breast cancer. However, current nuclear DNA-mediated activation of STING pathway remains constrained by the tight protection of nuclear membrane and histones, highlighting the need for new strategies to enhance its efficacy. Mitochondrial DNA (mtDNA), in contrast, is more vulnerable to damage. Herein, our nanoplatforms exploited the high glutathione (GSH) environment characteristic of tumors to release abundant Mn^b+, which induced mitochondrial dysfunction and the release of endogenous mtDNA. The released mtDNA, in conjunction with Mn^b+ itself functioning as a strong cGAS agonist, effectively activated cGAS-STING pathway. Consequently, the cGAS-STING-dependent secretion of type I interferon successively enhanced the maturation of dendritic cells and cross-priming of CD8⁺ T cells. In a poorly immunogenic 4T1 tumor model, TPP-MMONs efficiently primed systemic antitumor immunity and significantly enhanced the therapeutic efficacy of αPD-L1 therapy, suppressing tumor growth in both localized and metastatic tumor models. These findings provided an innovative and straightforward strategy to enhance TNBC immunogenicity by targeting mitochondrial damage to induce mtDNA-mediated cGAS-STING activation, thereby sensitizing tumors to immune checkpoint inhibitor therapy. STATEMENT OF SIGNIFICANCE: The cGAS-STING pathway is a promising target for overcoming immunoresistance in TNBC. However, current nuclear DNA-based activation strategies are limited by the tight protection of nuclear membrane and histones. Herein, we reported novel manganese-rich, mitochondria-targeting nanoplatforms (TPP-MMONs), which can release abundant Mn²⁺ and significantly induce mitochondrial dysfunction, leading to the release of mtDNA. As a result, the nanoplatforms can effectively stimulate the cGAS-STING pathway, thereby enhancing immune responses and improving the therapeutic efficacy of αPD-L1 therapy, offering new insights into TNBC treatments.