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

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 (pks) 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.

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.

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.