Engineered Bacteria-Vesicle Delivered Lactate Reprogramming Boosts Tumor Radiosensitivity

Radiotherapy (RT) remains a cornerstone in cancer treatment, yet its efficacy is often compromised by tumor-acquired radioresistance, driven in part by lactate accumulation in the tumor microenvironment (TME). Lactate fosters therapeutic resistance through aberrant DNA repair, immunosuppression, and metabolic reprogramming, posing a formidable clinical challenge. Here, we report a precision microbial therapy leveraging engineered Escherichia coli Nissle 1917 (EcNΔnlpI^IHCL, ENHL) to target and deplete lactate in the TME. By utilizing engineered bacteria with nlpI gene deletion to enhance outer membrane vesicles (OMVs) biogenesis and introducing a bifunctional surface display system (INP-HlpA for tumor targeting and ClyA-EGFP for tracking), ENHL delivers lactate oxidase (LOx) to neutralize acidic stress. In vitro and in vivo studies confirm that ENHL and LOx-loaded OMVs effectively radiosensitize colorectal cancer cells by depleting tumor-derived and radiation-induced lactate. Oral administration of ENHL selectively colonizes tumors, where arabinose induction triggers localized LOx expression, significantly improving radiosensitivity and immune cell infiltration while modulating gut microbiota. This synergistic approach-combining targeted metabolic modulation with microbial precision therapy-represents a transformative strategy to overcome RT resistance in colorectal cancer, offering a promising pathway toward clinical translation.