Orally delivered metabolically reprogrammed probiotics for cascade-activated antitumor immunity in colorectal cancer

Immunotherapy for colorectal cancer (CRC) remains limited due to the inherently low tumor immunogenicity and the profoundly immunosuppressive tumor microenvironment (TME). Herein, capitalizing on the metabolic traits and anatomical accessibility of CRC, we propose a broadly applicable oral strategy based on metabolically engineered bacteria (EcN-HlpA-CGL [EHC]) for CRC immunotherapy. Mechanistically, cystathionine γ-lyase expressed by EHC disrupts redox homeostasis, triggering ferroptosis in CRC cells and thereby enhancing tumor immunogenicity. Concurrently, the intrinsic adjuvant activity of the bacteria amplifies the cancer-immunity cycle driven by immunogenic cell death and remodels the immunosuppressive TME. In vivo studies demonstrate that this orally delivered engineered bacterial platform not only suppresses the growth of orthotopic CRC tumors but also inhibits metastatic progression, indicating the induction of a potent systemic immune response. Immune profiling confirms robust systemic and gut mucosal immune activation following oral administration. Collectively, this oral metabolically engineered bacterial platform is precisely tailored to the features of CRC and offers a safe and effective immunotherapeutic strategy for this malignancy.