Engineering improves antitumor efficacy via enhancing cytotoxic T cell responses.

Cancer immunotherapy based on bioengineering of bacteria can effectively increase anticancer immune responses. However, few studies have investigated the antitumor potential of engineering . Here, we genetically engineered to overexpress flagellin B (FlaB) protein in a murine CT26 tumor model. We found that a large number of FlaB-expressing colonized tumor tissues, enhanced T cell infiltration and secretion of cytokines and cytotoxic proteins in tumors, and significantly restrained tumor growth. Our results also showed that programmed death ligand 1 (PD-L1) expression in tumor-infiltrating immune cells was elevated after treatment with FlaB-expressing . In addition, combination therapy with FlaB-expressing and PD-L1 blockade synergistically improved antitumor efficacy by enhancing infiltration of CD8 cells. Furthermore, serum liver biochemical indices of mice increased in the short term in both the and the FlaB-expressing treatment groups but gradually recovered in the later stage of treatment so that FlaB protein expression did not increase the toxicity of . Taken together, our results suggest that could serve as an engineered bacterium for bacterium-based cancer immunotherapy.