title: Analysis of beta-catenin, Ki-ras, and microsatellite stability in azoxymethane-induced colon tumors of BDIX/Orl Ico rats.
abstract: The aim of the study reported here was to investigate whether the azoxymethane (AOM)-induced colon cancer rat model mimics the human situation with regard to microsatellite stability, changes in expression of beta-catenin, and/or changes in the sequence of the proto-oncogene Ki-ras. Colon cancer was induced by administration of four weekly doses of AOM (15 mg/kg of body weight per week) separated by a one-week break between the second and third injections. As the histopathologic characteristics of this model resemble those of the human counterpart, further characterization of the genetic changes was undertaken. The animals were euthanized 28 to 29 weeks after the first AOM injection, and tumor specimens were taken for histologic and DNA analyses. Since microsatellite variation was found in only a few (< 2%) specimens, the model can be considered as having stable microsatellites. This result is in accordance with those of similar studies in other rat models and with most human colorectal cancers. Immunohistochemical analyses of beta-catenin did not reveal loss of gene activity, nor did the sequencing of Ki-ras reveal mutations. These results are in contrast to most findings in comparable rat studies. The deviations may be due to differences in exposure to the carcinogen or difference in strain and/or age. The lack of beta-catenin and Ki-ras alterations in this colon cancer model is unlike human sporadic colorectal cancers where these genetic changes are common findings.
authors.affiliation: Biomedical Laboratory, Faculty of Health Sciences, University of Southern Denmark, Winsloewparken 23, DK-5000 Odense, Denmark.
authors.forename: Nanna Møller
authors.initials: NM
authors.lastname: Sørensen
authors.forename: Morten
authors.initials: M
authors.lastname: Kobaek-Larsen
authors.forename: Anita
authors.initials: A
authors.lastname: Bonne
authors.forename: Bert
authors.initials: B
authors.lastname: van Zutphen
authors.forename: Claus
authors.initials: C
authors.lastname: Fenger
authors.forename: Karsten
authors.initials: K
authors.lastname: Kristiansen
authors.forename: Merel
authors.initials: M
authors.lastname: Ritskes-Hoitinga
mesh_terms: D000230:Adenocarcinoma / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D001397:Azoxymethane / Q000633:toxicity*; D003110:Colonic Neoplasms / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D003598:Cytoskeletal Proteins / Q000235:genetics* / Q000378:metabolism; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000032:analysis; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D011905:Genes, ras; D007124:Immunoenzyme Techniques; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics*; D016133:Polymerase Chain Reaction; D000090063:Proto-Oncogene Mas; D051381:Rats; D011919:Rats, Inbred Strains; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D051176:beta Catenin
chemical_list: C495268:Ctnnb1 protein, rat; D003598:Cytoskeletal Proteins; D004273:DNA, Neoplasm; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D015534:Trans-Activators; D051176:beta Catenin; D001397:Azoxymethane