Molecular genetic analysis of malignant melanomas for aberrations of the WNT signaling pathway genes CTNNB1, APC, ICAT and BTRC.
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 (beta-catenin gene, 3p22.1), APC (adenomatous polyposis coli gene, 5q22.2), BTRC (beta-transducin repeat-containing protein gene, 10q24.3) and ICAT (inhibitor of beta-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 beta-catenin, which is important for the regulation of beta-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 (<or=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.
Reifenberger
Julia
J
Department of Dermatology, Heinrich-Heine-University, Düsseldorf, Germany. reifenbergerj@med.uni-duesseldorf.de
Knobbe
Christiane B
CB
Wolter
Marietta
M
Blaschke
Britta
B
Schulte
Klaus W
KW
Pietsch
Torsten
T
Ruzicka
Thomas
T
Reifenberger
Guido
G
D048868:Adaptor Proteins, Signal Transducing; D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D019204:GTP-Binding Proteins / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008545:Melanoma / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D009124:Muscle Proteins / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D018807:Polymorphism, Single-Stranded Conformational; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins; D015398:Signal Transduction; D015534:Trans-Activators; D051176:beta Catenin; D044844:beta-Transducin Repeat-Containing Proteins
D048868:Adaptor Proteins, Signal Transducing; D025601:Adenomatous Polyposis Coli Protein; C471644:BTRC protein, human; C495270:CTNNB1 protein, human; C411982:CTNNBIP1 protein, human; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D015534:Trans-Activators; D051176:beta Catenin; D044844:beta-Transducin Repeat-Containing Proteins; D019204:GTP-Binding Proteins