DNA cross-link repair deficiency enhances human cell sensitivity to colibactin-induced genotoxicity

Introduction Colibactin is a small genotoxic molecule of polyketide produced by a subset of enteric bacteria including certain Escherichia coli ( E. coli ) harbored in the human gut microbiota. Its biosynthesis is governed by a multistep enzymatic process encoded by the polyketide synthase ( pk s) gene cluster. Colibactin is thought to exert its carcinogenic potential primarily through the induction of DNA interstrand crosslinks (ICLs); however, the precise mechanisms underlying its genotoxicity remain largely unresolved. In this study, we focused on ICL formation and its associated repair pathways to investigate whether colibactin-induced ICLs play a central role in the induction of chromosomal aberrations and inhibition of cell proliferation. Findings HAP1 cells deficient in FANCD2 , a gene essential for ICL repair, and their wild-type counterparts were infected with colibactin producing ( clb ⁺) E. coli strains isolated from a Japanese colorectal cancer (CRC) patient. Following recovery culture, the frequency of micronucleated (MN) cells was assessed. The results showed that FANCD2 -deficient cells exhibited a significantly higher frequency of MN cells compared to wild-type cells. Additionally, the cytotoxicity of the clb ⁺ strains was evaluated using the XTT assay. FANCD2 -deficient cells demonstrated higher sensitivity to the clb ⁺ E. coli strains than wild-type cells. Conclusion These findings suggest that colibactin, produced by clb ⁺ E. coli , can play a role in the formation of ICLs, thereby contributing significantly to the induction of chromosomal aberrations and the inhibition of human cell proliferation.