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

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.