title: Genotoxicity of Cytolethal Distending Toxin (CDT) on Isogenic Human Colorectal Cell Lines: Potential Promoting Effects for Colorectal Carcinogenesis.
abstract: The composition of the human microbiota influences tumorigenesis, notably in colorectal cancer (CRC). Pathogenic Escherichia coli possesses a variety of virulent factors, among them the Cytolethal Distending Toxin (CDT). CDT displays dual DNase and phosphatase activities and induces DNA double strand breaks, cell cycle arrest and apoptosis in a broad range of mammalian cells. As CDT could promote malignant transformation, we investigated the cellular outcomes induced by acute and chronic exposures to E. coli CDT in normal human colon epithelial cells (HCECs). Moreover, we conducted a comparative study between isogenic derivatives cell lines of the normal HCECs in order to mimic the mutation of three major genes found in CRC genetic models: APC, KRAS, and TP53. Our results demonstrate that APC and p53 deficient cells showed impaired DNA damage response after CDT exposure, whereas HCECs expressing oncogenic KRAS (V12) were more resistant to CDT. Compared to normal HCECs, the precancerous derivatives exhibit hallmarks of malignant transformation after a chronic exposure to CDT. HCECs defective in APC and p53 showed enhanced anchorage independent growth and genetic instability, assessed by the micronucleus formation assay. In contrast, the ability to grow independently of anchorage was not impacted by CDT chronic exposure in KRAS(V12) HCECs, but micronucleus formation is dramatically increased. Thus, CDT does not initiate CRC by itself, but may have promoting effects in premalignant HCECs, involving different mechanisms in function of the genetic alterations associated to CRC.
authors.affiliation: Institut National de la Recherche Agronomique UMR 1331, TOXALIM (Research Center in Food Toxicology), Université de Toulouse, INRA, INP-ENVT, INP-EI-Purpan, Université de Toulouse III Paul Sabatier Toulouse, France.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Graillot
authors.affiliation: Institut National de la Recherche Agronomique UMR 1331, TOXALIM (Research Center in Food Toxicology), Université de Toulouse, INRA, INP-ENVT, INP-EI-Purpan, Université de Toulouse III Paul Sabatier Toulouse, France.
authors.forename: Inge
authors.initials: I
authors.lastname: Dormoy
authors.affiliation: Institut National de la Recherche Agronomique UMR 1331, TOXALIM (Research Center in Food Toxicology), Université de Toulouse, INRA, INP-ENVT, INP-EI-Purpan, Université de Toulouse III Paul Sabatier Toulouse, France.
authors.forename: Jacques
authors.initials: J
authors.lastname: Dupuy
authors.affiliation: Department of Cell Biology, The University of Texas Southwestern Medical CenterDallas, TX, USA; Center for Excellence in Genomics Medicine Research, King Abdulaziz UniversityJeddah, Saudi Arabia.
authors.forename: Jerry W
authors.initials: JW
authors.lastname: Shay
authors.affiliation: Institut National de la Recherche Agronomique UMR 1331, TOXALIM (Research Center in Food Toxicology), Université de Toulouse, INRA, INP-ENVT, INP-EI-Purpan, Université de Toulouse III Paul Sabatier Toulouse, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Huc
authors.affiliation: Institut National de la Recherche Agronomique UMR 1331, TOXALIM (Research Center in Food Toxicology), Université de Toulouse, INRA, INP-ENVT, INP-EI-Purpan, Université de Toulouse III Paul Sabatier Toulouse, France.
authors.forename: Gladys
authors.initials: G
authors.lastname: Mirey
authors.affiliation: Institut National de la Recherche Agronomique UMR 1331, TOXALIM (Research Center in Food Toxicology), Université de Toulouse, INRA, INP-ENVT, INP-EI-Purpan, Université de Toulouse III Paul Sabatier Toulouse, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Vignard
mesh_terms: D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics; D017209:Apoptosis / Q000187:drug effects; D001427:Bacterial Toxins / Q000494:pharmacology*; D063646:Carcinogenesis / Q000187:drug effects*; D002273:Carcinogens / Q000494:pharmacology*; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000235:genetics / Q000473:pathology*; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects*; D004260:DNA Repair / Q000187:drug effects; D004847:Epithelial Cells / Q000473:pathology; D004926:Escherichia coli / Q000472:pathogenicity; D006801:Humans; D007413:Intestinal Mucosa / Q000473:pathology; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000235:genetics
chemical_list: C555337:APC protein, human; D025601:Adenomatous Polyposis Coli Protein; D001427:Bacterial Toxins; D002273:Carcinogens; C117307:KRAS protein, human; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C067044:cytolethal distending toxin; D016283:Proto-Oncogene Proteins p21(ras)
keywords: APC; DNA double strand breaks; KRAS; colorectal cancer; cytolethal distending toxin; genotoxicity; p53