Manganese-engineered Lactobacillus Reuteri with enhanced antitumor and immunomodulatory activities for colorectal cancer prevention and treatment

Probiotic-based biotherapy for colorectal cancer (CRC) faces significant challenges due to poor tumor-targeting and limited bioactivities within the complex tumor microenvironment. This study shows that Lactobacillus reuteri (L. reuteri)'s inherent bioactivities, including proliferation, metabolism, and colorectal colonization, can be enhanced by manganese, prompting the fabrication of a manganese-engineered strain (MnLR). Oral administration of MnLR with its metabolic substrate-glycerol (MnLR/Gly) promotes the enrichment of L. reuteri and its antitumor metabolites within colon tumors. Across multiple preclinical colon tumor models, MnLR/Gly alone achieves a 95.6% inhibition of orthotopic tumor growth, liver metastases reduction by 62.1%, and confers durable protection, with 75% of prophylactically treated mice remaining long-term tumor-free and 62.5% resisting tumor rechallenge. Mechanistically, MnLR/Gly induces both intratumoral and peripheral dendritic cell maturation, M1 macrophage polarization, and effector T-cell responses. In orthotopic CRC rabbit models, GlyMnLR enteric capsules demonstrate significant antitumor efficacy comparable to standard chemotherapy while exhibiting favorable safety. These findings highlight MnLR as an effective standalone probiotic therapy for CRC prevention and treatment.