Cytotoxic necrotizing factor 1 hinders colon tumorigenesis induced by colibactin-producing Escherichia coli in ApcMin/+ mice

Colorectal cancer (CRC) patients are frequently colonized by colibactin-producing Escherichia coli (CoPEC) (>40%), which enhances tumorigenesis in mouse models of CRC. We observed that 50% of CoPEC also contains the cnf1 gene, which encodes cytotoxic necrotizing factor-1 (CNF1), an enhancer of the eukaryotic cell cycle. The impact of its co-occurrence with colibactin (Clb) has not yet been investigated. We evaluated the impact of CNF1 on colorectal tumorigenesis using human colonic epithelial HT-29 cells and CRC-susceptible Apc ( Min/+ ) mice inoculated with the CoPEC 21F8 clinical strain (Clb+Cnf+) or 21F8 isogenic mutants (Clb+Cnf-, Clb-Cnf+ and Clb-Cnf-). Infection with the Clb+Cnf- strain induced higher levels of inflammatory cytokines and senescence markers both in vitro and in vivo compared to those induced by infection with the Clb+Cnf+ strain. In contrast, the Clb+Cnf- and Clb+Cnf+ strains generated similar levels of DNA damage in HT-29 cells and in colonic murine tissues. Furthermore, the Apc ( Min/+ ) mice inoculated with the Clb+Cnf- strain developed significantly more tumors than the mice inoculated with the Clb+Cnf+ strain or the isogenic mutants, and the composition of their microbiota was changed. Finally, rectal administration of the CNF1 protein in Apc ( Min/+ ) mice inoculated with the Clb+Cnf- strain significantly decreased tumorigenesis and inflammation. Overall, this study provides evidence that CNF1 decreases the carcinogenic effects of CoPEC in Apc ( Min/+ ) mice by decreasing CoPEC-induced cellular senescence and inflammation.

Automated summary

This study found that colorectal cancer patients are often colonized by colibactin-producing Escherichia coli (CoPEC) bacteria, and half of the CoPEC bacteria also contain the cnf1 gene, which enhances their impact on eukaryotic cells. Mutations containing both the colibactin and cnf1 genes induced higher levels of inflammation and senescence markers compared to mutations containing only the colibactin gene. Additionally, mice inoculated with the mutation containing both genes developed significantly fewer tumors and had a changed microbiota composition.