Nanotoxin induces in situ pyroptosis to sensitize αPD1 to ablate metastases in microsattellite stable colorectal cancer

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Nanomedicine has not generated anticancer immunotherapies because of insufficient targeted specificity, lack of immunity, and associated toxicity. We developed a T22-DITOX-H6 (TDX) nanotoxin to selectively release the diphtheria toxin in the cancer cells in immunosuppressed CXCR4-overexpressing (CXCR4 +) colorectal (CRC) models, inducing pyroptosis and anticancer effect. Microsatellite stable (MSS) CRC patients do not respond to current immunotherapy. Since pyroptosis is highly immunogenic, we treated with TDX immunocompetent CXCR4 + CT26 MSS metastatic CRC models to selectively deliver the toxin to induce in situ pyroptosis mediated by the activation of NLRP3, Caspase-1 GSDMD and IL-1β. In contrast to immunosuppressed, in situ pyroptosis by TDX in immunocompetent models trigger CD8 + T cell recruitment, activation and killing of cancer cells in tissues, mimicking the pyroptosis that the host induces to kill diphtheria-infected cells. The combination of TDX and αPD1 further increases CD8 + recruitment and perforin secretion, achieving a tissue-specific antimetastatic activity in mesentery, peritoneum, and lung, and especially in liver metastases, without systemic toxicity. This is the first time that a novel nanomedicine achieves local T cell activation and antimetastatic effect mediated by pyroptosis and immunogenic cell death, whereas the combination with αPD1 enhances T cell activation, reaching a synergistic response in MSS CRC models.

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