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Molecular genetic analysis of malignant melanomas for aberrations of the WNT signaling pathway genes CTNNB1, APC, ICAT and BTRC
Author(s) -
Reifenberger Julia,
Knobbe Christiane B.,
Wolter Marietta,
Blaschke Britta,
Schulte Klaus W.,
Pietsch Torsten,
Ruzicka Thomas,
Reifenberger Guido
Publication year - 2002
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.10512
Subject(s) - wnt signaling pathway , cancer research , biology , melanoma , adenomatous polyposis coli , exon , mutation , missense mutation , germline mutation , somatic cell , gene , genetics , cancer , colorectal cancer
Aberrant activation of the Wnt signaling pathway has been reported in different human tumor types, including malignant melanomas. We investigated 37 malignant melanomas (15 primary tumors and 22 metastases) for alterations of 4 genes encoding members of this pathway, i.e., CTNNB1 (β‐catenin gene, 3p22.1), APC (adenomatous polyposis coli gene, 5q22.2), BTRC (β‐transducin repeat–containing protein gene, 10q24.3) and ICAT (inhibitor of β‐catenin and Tcf‐4, 1p36.2). Mutational analysis of CTNNB1 identified somatic mutations in 1 primary melanoma and 1 melanoma metastasis from 2 different patients (5%). Both mutations affected the N‐terminal degradation box of β‐catenin, which is important for the regulation of β‐catenin homeostasis. Another primary melanoma carried a somatic APC missense mutation within the known mutation cluster region in exon 15. Fourteen tumors (40%) showed LOH at microsatellite markers on 1p36. None of the tumors had lost both copies of the ICAT gene, but 1 melanoma metastasis carried a somatic point mutation altering the translation start codon of ICAT. Real‐time RT‐PCR showed markedly reduced ICAT transcript levels (≤20% relative to normal skin and benign melanocytic nevi) in 28/36 malignant melanomas (78%), including 13/14 tumors with LOH on 1p36. Allelic loss on 10q was detected in 15 tumors (44%). We found neither mutations nor complete loss of expression of the BTRC gene in our melanoma series. Taken together, our results indicate that the Wnt pathway may be altered in malignant melanomas by different mechanisms, including rare somatic mutations in CTNNB1, APC or ICAT, as well as low or absent expression of ICAT transcripts. © 2002 Wiley‐Liss, Inc.