Abstract

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 (EcNΔ nlpI 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.