High Prevalence of Mucosa-Associated E. coli Producing Cyclomodulin and Genotoxin in Colon Cancer

Abstract

Some Escherichia coli strains produce toxins designated cyclomodulins (CMs) which interfere with the eukaryotic cell cycle of host cells, suggesting a possible link between these bacteria and cancers. There are relatively few data available concerning the colonization of colon tumors by cyclomodulin- and genotoxic-producing E. coli. We did a qualitative and phylogenetic analysis of mucosa-associated E. coli harboring cyclomodulin-encoding genes from 38 patients with colorectal cancer (CRC) and 31 with diverticulosis. The functionality of these genes was investigated on cell cultures and the genotoxic activity of strains devoid of known CM-encoding gene was investigated. Results showed a higher prevalence of B2 phylogroup E. coli harboring the colibatin-producing genes in biopsies of patients with CRC (55.3%) than in those of patients with diverticulosis (19.3%), (p<0.01). Likewise, a higher prevalence of B2 E. coli harboring the CNF1-encoding genes in biopsies of patients with CRC (39.5%) than in those of patients with diverticulosis (12.9%), (p = 0.01). Functional analysis revealed that the majority of these genes were functional. Analysis of the ability of E. coli to adhere to intestinal epithelial cells Int-407 indicated that highly adherent E. coli strains mostly belonged to A and D phylogroups, whatever the origin of the strains (CRC or diverticulosis), and that most E. coli strains belonging to B2 phylogroup displayed very low levels of adhesion. In addition, 27.6% (n = 21/76) E. coli strains devoid of known cyclomodulin-encoding genes induced DNA damage in vitro, as assessed by the comet assay. In contrast to cyclomodulin-producing E. coli, these strains mainly belonged to A or D E. coli phylogroups, and exhibited a non significant difference in the distribution of CRC and diverticulosis specimens (22% versus 32.5%, p = 0.91). In conclusion, cyclomodulin-producing E. coli belonging mostly to B2 phylogroup colonize the colonic mucosa of patients with CRC.

Intracellular colon cancer-associated Escherichia coli promote protumoral activities of human macrophages by inducing sustained COX-2 expression

“…Acquisition of protumoral function by macrophages is directly influenced by tumor microenvironment. As several independent studies have reported high colonization by E. coli of adenomas and carcinomas in colon cancer patients, [15][16][17][18][19] we have analyzed the effect of such a microbial environmental factor on COX-2 expression in human macrophages. Phagocytic uptake of pathogens by macrophages results in the formation of vacuoles that rapidly evolve into bactericidal Figure 3 Intramacrophagic persistence of E. coli strains isolated from colon cancer patients.…”

“…19,33 Bacteria were grown routinely in Luria Bertani (LB) broth or on LB agar plates overnight at 37 1C.…”

“…[10][11][12][13][14] In addition, our group and others have shown that colonic adenomas, carcinomas, and the mucosa of CRC patients are abnormally colonized by Escherichia coli belonging to the B2 phylogroup, with a high prevalence of E. coli producing a genotoxin, termed colibactin, encoded by the pks genomic island. [15][16][17][18][19][20] It has been recently demonstrated that cells that survive infection with colibactin-producing E. coli display hallmarks of cellular senescence accompanied with production of reactive oxygen species and secretion of pro-inflammatory cytokines, chemokines, and proteases, inducing bystander genotoxic and oncogenic effects. 21,22 Macrophages are one of the predominant components of murine and human tumor-infiltrating cells.…”

Targeting colorectal cancer-associated bacteria: A new area of research for personalized treatments

“…20 Interestingly, molecular analyses of these strains have revealed that they frequently harbor in their genome one or several pathogenic islands responsible for the production of toxins. 21,22 These toxins can induce DNA damage and/or affect the cellular cycle. E. coli harboring cytotoxic necrotizing factor (Cnf) and cytolethal distending toxin (Cdt) are significantly associated with CRC biopsies.…”

“…E. coli harboring cytotoxic necrotizing factor (Cnf) and cytolethal distending toxin (Cdt) are significantly associated with CRC biopsies. 21 However, the toxin most frequently associated with E. coli colonizing CRC is colibactin. 21,22 Colibactin is a genotoxic polyketide non-ribosomal peptide (PK-NRP) not yet purified and synthetized by the pks genomic island.…”