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

Manganese enhances L. reuteri's inherent bioactivities including proliferation, metabolism, and colorectal colonization.

• Manganese engineering was used to fabricate a modified strain designated MnLR.
• The enhancement of bioactivities prompted the fabrication strategy combining MnLR with its metabolic substrate glycerol (MnLR/Gly).
• Enhanced colonization within colon tumors was observed following oral administration.
• Antitumor metabolites were enriched within colon tumors as a result of enhanced colonization and metabolism.

MnLR/Gly achieves 95.6% inhibition of orthotopic tumor growth across multiple preclinical colon tumor models.

• Tumor growth inhibition of 95.6% was observed in orthotopic tumor models.
• Results were demonstrated across multiple preclinical colon tumor models.
• MnLR/Gly was administered as a standalone therapy without combination with standard chemotherapy in these models.
• Liver metastases were reduced by 62.1% with MnLR/Gly treatment.

Prophylactic treatment with MnLR/Gly confers durable long-term tumor-free protection and resistance to tumor rechallenge.

• 75% of prophylactically treated mice remained long-term tumor-free.
• 62.5% of prophylactically treated mice resisted tumor rechallenge.
• These results indicate durable immunological protection beyond initial tumor prevention.
• The prophylactic efficacy was observed in preclinical mouse models.

MnLR/Gly mechanistically induces intratumoral and peripheral dendritic cell maturation, M1 macrophage polarization, and effector T-cell responses.

• Both intratumoral and peripheral dendritic cell maturation were induced by MnLR/Gly.
• M1 macrophage polarization was observed as part of the immunomodulatory mechanism.
• Effector T-cell responses were elicited, consistent with adaptive immune activation.
• These findings suggest a multi-faceted immunomodulatory mechanism underlying the antitumor efficacy.

GlyMnLR enteric capsules demonstrate significant antitumor efficacy comparable to standard chemotherapy in orthotopic CRC rabbit models with favorable safety.

• Orthotopic colorectal cancer rabbit models were used to assess translational potential.
• GlyMnLR was formulated as enteric capsules for oral administration in this model.
• Antitumor efficacy was described as comparable to standard chemotherapy.
• Favorable safety profile was exhibited compared to standard chemotherapy.
• Rabbit models were used as a larger preclinical model to extend findings beyond mouse studies.

Oral administration of MnLR with glycerol promotes enrichment of L. reuteri and its antitumor metabolites within colon tumors.

• Glycerol was identified as the metabolic substrate for L. reuteri in this system.
• Oral administration route was used, relevant to clinical translatability for colorectal cancer.
• Enrichment of both the bacterial strain and its metabolites was observed specifically within colon tumors.
• This tumor-targeting addresses the challenge of poor tumor-targeting identified for probiotic-based biotherapy.