Nanobody‐Engineered Biohybrid Bacteria Targeting Gastrointestinal Cancers Induce Robust STING‐Mediated Anti‐Tumor Immunity

Bacteria can be utilized for cancer therapy owing to their preferential colonization at tumor sites. However, unmodified non‐pathogenic bacteria carry potential risks due to their non‐specific targeting effects, and their anti‐tumor activity is limited when used as monotherapy. In this study, a biohybrid‐engineered bacterial system comprising non‐pathogenic MG1655 bacteria modified with CDH17 nanobodies on their surface and conjugated with photosensitizer croconium (CR) molecules is developed. The resultant biohybrid bacteria can efficiently home to CDH17‐positive tumors, including gastric, pancreatic, and colorectal cancers, and significantly suppress tumor growth upon irradiation. More importantly, biohybrid bacteria‐mediated photothermal therapy (PTT) induced abundant macrophage infiltration in a syngeneic murine colorectal model. Further, that the STING pathway is activated in tumor macrophages by the released bacterial nucleic acid after PTT is revealed, leading to the production of type I interferons. The addition of CD47 nanobody but not PD‐1 antibody to the PTT regimen can eradicate the tumors and extend survival. This results indicate that bacteria endowed with tumor‐specific selectivity and coupled with photothermal payloads can serve as an innovative strategy for low‐immunogenicity cancers. This strategy can potentially reprogram the tumor microenvironment by inducing macrophage infiltration and enhancing the efficacy of immunotherapy targeting macrophages. This work developed a biohybrid bacterial system through genetic engineering and biomaterial hybridization in which CDH17 nanobodies are engineered onto the bacteria for tumor targeting and a photothermal material croconium (CR) dye is conjugated on bacteria for PTT induction. When combined with checkpoint blockade CD47 nanobody, the biohybrid bacteria successfully eradicated the tumors through STING activation, and considerably extended survival of the mice.