Colon cancer-associated B2 Escherichia coli colonize gut mucosa and promote cell proliferation

AIM:To provide further insight into the characterization of mucosa-associated Escherichia coli(E.coli)isolated from the colonic mucosa of cancer patients.METHODS:Phylogroups and the presence of cyclomodulin-encoding genes of mucosa-associated E.coli from colon cancer and diverticulosis specimens weredetermined by PCR.Adhesion and invasion experiments were performed with I-407 intestinal epithelial cells using gentamicin protection assay.Carcinoembryonic antigen-related cell adhesion molecule 6(CEACAM6)expression in T84 intestinal epithelial cells was measured by enzyme-linked immunosorbent assay and by Western Blot.Gut colonization,inflammation and procarcinogenic potential were assessed in a chronic infection model using CEABAC10 transgenic mice.Cell proliferation was analyzed by real-time mRNA quantification of PCNA and immunohistochemistry staining of Ki67.RESULTS:Analysis of mucosa-associated E.coli from colon cancer and diverticulosis specimens showed that whatever the origin of the E.coli strains,86%of cyclomodulin-positive E.coli belonged to B2 phylogroup and most harbored polyketide synthase(pks)island,which encodes colibactin,and/or cytotoxic necrotizing factor(cnf)genes.In vitro assays using I-407 intestinal epithelial cells revealed that mucosa-associated B2 E.coli strains were poorly adherent and invasive.However,mucosa-associated B2 E.coli similarly to Crohn’s disease-associated E.coli are able to induce CEACAM6expression in T84 intestinal epithelial cells.In addition,in vivo experiments using a chronic infection model of CEACAM6 expressing mice showed that B2 E.coli strain11G5 isolated from colon cancer is able to highly persist in the gut,and to induce colon inflammation,epithelial damages and cell proliferation.CONCLUSION:In conclusion,these data bring new insights into the ability of E.coli isolated from patients with colon cancer to establish persistent colonization,exacerbate inflammation and trigger carcinogenesis.

Association of colorectal cancer with pathogenic Escherichia coli: Focus on mechanisms using optical imaging

AIM: To investigate the molecular or cellular mechanisms related to the infection of epithelial colonic mucosa by pks-positive Escherichia coli(E. coli) using optical imaging.METHODS: We choose to evaluate the tumor metabolic activity using a fluorodeoxyglucose analogue as 2-deoxyglucosone fluorescent probes and to correlate it with tumoral volume(mm^3). Inflammation measuring myeloperoxidase(MPO) activity and reactive oxygen species production was monitored by a bioluminescent(BLI) inflammation probe and related to histological examination and MPO levels by enzyme-linked immunosorbent assay(ELISA) on tumor specimens. The detection and quantitation of these two signals were validated on a xenograft model of human colon adenocarcinoma epithelial cells(HCT116) in nude mice infected with a pks-positive E. coli. The inflammatory BLI signal was validated intra-digestively in the colitisCEABAC10 DSS models, which mimicked Crohn's disease. RESULTS: Using a 2-deoxyglucosone fluorescent probe, we observed a high and specific HCT116 tumor uptake in correlation with tumoral volume(P = 0.0036). Using the inflammation probe targeting MPO, we detected a rapid systemic elimination and a significant increase of the BLI signal in the pks-positive E. coli-infected HCT116 xenograft group(P < 0.005). ELISA confirmed that MPO levels were significantly higher(1556 ± 313.6 vs 234.6 ± 121.6 ng/m L P = 0.001) in xenografts infected with the pathogenic E. coli strain. Moreover, histological examination of tumor samples confirmed massive infiltration of pks-positive E. coli-infected HCT116 tumors by inflammatory cells compared to the uninfected group. These data showed that infection with the pathogenic E. coli strain enhanced inflammation and ROS production in tumors before tumor growth. Moreover, we demonstrated that the intra-digestive monitoring of inflammation is feasible in a reference colitis murine model(CEABAC10/DSS).CONCLUSION: Using BLI and fluorescence optical imaging, we provided tools to better understand hostpathogen interactions at the early stage of disease, such as inflammatory bowel disease and colorectal cancer.