Engineered NK Exosomes for Tumor Immunotherapy via a Positive Feedback Loop-Mediated Efficient Pyroptosis

Pyroptosis, an immunogenic cell death mediated by Gasdermin proteins, enhances antitumor immune responses and reshapes the tumor microenvironment. Among the Gasdermin proteins, Gasdermin E (GSDME) can be cleaved by caspase-3 or Granzyme B (GZMB), releasing the N-terminal GSDME fragment (GSDME-N) to initiate pyroptosis. However, the effectiveness of GSDME-induced pyroptosis is often limited due to GSDME silencing via methylation and underutilizing the concurrent cleavage of GSDME by caspase-3 and GZMB. Herein, an innovative integrated platform based on engineered exosomes, termed NK-RG-exo, is developed. NK-RG-exo is engineered by loading the methyltransferase inhibitor RG108 into exosomes derived from natural killer cells that naturally express GZMB. In tumor cells, RG108 restores GSDME expression by demethylation, and GZMB directly cleaves GSDME and triggers caspase-3 activation that, in turn, also cleaves GSDME. These dual pathways ensure substantial release of GSDME-N to initiate pyroptosis. Furthermore, GSDME-N disrupts mitochondrial membranes, releasing Cytochrome C to activate caspase-3, which further cleaves GSDME again, thereby creating a positive feedback loop. In an orthotopic breast cancer mouse model characterized by limited immune cell infiltration, NK-RG-exo significantly induces antitumor immune responses by intense pyroptosis. The proposed strategy effectively overcomes the immunosuppressive tumor microenvironment, holding significant promise in cancer therapy.