Mutational activation of the RAS-RAF-MAPK and the wnt pathway in small intestinal adenocarcinomas

Background: Adenocarcinomas of the small and the large intestine share risk factors and morphological features but both tumor types seem to follow different genetic pathways. The aim of this study on small intestinal carcinomas was to analyze alternative mechanisms of activation of pathways that are...

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Bibliographic Details
Published in:Scandinavian journal of gastroenterology 2004-08, Vol.39 (8), p.748-753
Main Authors: Bläker, H., Helmchen, B., Bönisch, A., Aulmann, S., Penzel, R., Otto, H. F., Rieker, R. J.
Format: Article
Language:English
Subjects:
Adenocarcinoma - genetics
Adenocarcinoma - metabolism
Aged
Aged, 80 and over
APC, β-catenin
beta Catenin
Biological and medical sciences
BRAF
Cytoskeletal Proteins - analysis
DNA Mutational Analysis
Female
Gastroenterology. Liver. Pancreas. Abdomen
Gene Expression Regulation, Neoplastic
Genes, APC
Genes, ras - genetics
Humans
Immunohistochemistry
Intestinal Neoplasms - genetics
Intestinal Neoplasms - metabolism
KRAS
Male
Medical sciences
Middle Aged
Mitogen-Activated Protein Kinases - genetics
Mutation
Proto-Oncogene Proteins - genetics
raf Kinases - genetics
small intestinal adenocarcinoma
Trans-Activators - analysis
Wnt Proteins
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Summary:Background: Adenocarcinomas of the small and the large intestine share risk factors and morphological features but both tumor types seem to follow different genetic pathways. The aim of this study on small intestinal carcinomas was to analyze alternative mechanisms of activation of pathways that are typically affected in colorectal cancer. Methods: Twenty-one sporadic carcinomas were investigated for mutations in KRAS, BRAF, the -catenin gene CTNNB1, and the mutational cluster region of APC. Immunohistochemical analysis was performed with a monoclonal antibody for -catenin, the transcriptionally active downstream component of wnt signaling. Results: Oncogene mutations were found in 13 (62%) small intestinal adenocarcinomas. Twelve tumors displayed a KRAS mutation, and a novel BRAF mutation at codon 603 604 was seen in one carcinoma without KRAS mutation. One tumor harbored a CTNNB1 mutation consisting of an insertion of 247 nucleotides deriving from chromosome 9. APC mutations were identified in 2 tumors. Immunohistochemistry demonstrated nuclear accumulation of -catenin in 5 carcinomas. These carcinomas included the tumor with a CTNNB1 mutation but not those with APC mutations. Conclusions: Our data show frequent activation of the RAS-RAF-MAPK pathway through mutations of either KRAS or, infrequently, BRAF. Activation of the wnt pathway through accumulation of -catenin may have a role in a subset of small intestinal adenocarcinomas but in contrast to colorectal carcinoma, accumulation of -catenin is generally not caused by inactivating APC or activating CTNNB1 mutations.
ISSN:0036-5521
1502-7708
DOI:10.1080/00365520410005847