title: CTNNB1 mutations and overexpression of Wnt/beta-catenin target genes in WT1-mutant Wilms' tumors.
abstract: Gain-of-function mutations in exon 3 of beta-catenin (CTNNB1) are specific for Wilms' tumors that have lost WT1, but 50% of WT1-mutant cases lack such "hot spot" mutations. To ask whether stabilization of beta-catenin might be essential after WT1 loss, and to identify downstream target genes, we compared expression profiles in WT1-mutant versus WT1 wild-type Wilms' tumors. Supervised and nonsupervised hierarchical clustering of the expression data separated these two classes of Wilms' tumor. The WT1-mutant tumors overexpressed genes encoding myogenic and other transcription factors (MOX2, LBX1, SIM2), signaling molecules (TGFB2, FST, BMP2A), extracellular Wnt inhibitors (WIF1, SFRP4), and known beta-catenin/TCF targets (FST, CSPG2, CMYC). Beta-Catenin/TCF target genes were overexpressed in the WT1-mutant tumors even in the absence of CTNNB1 exon 3 mutations, and complete sequencing revealed gain-of-function mutations elsewhere in the CTNNB1 gene in some of these tumors, increasing the overall mutation frequency to 75%. Lastly, we identified and validated a novel direct beta-catenin target gene, GAD1, among the WT1-mutant signature genes. These data highlight two molecular classes of Wilms' tumor, and indicate strong selection for stabilization of beta-catenin in the WT1-mutant class. Beta-Catenin stabilization can initiate tumorigenesis in other systems, and this mechanism is likely critical in tumor formation after loss of WT1.
authors.affiliation: Institute of Cancer Genetics, Columbia University College of Physicians and Surgeons, New York, New York, USA.
authors.forename: Chi-Ming
authors.initials: CM
authors.lastname: Li
authors.forename: Connie E
authors.initials: CE
authors.lastname: Kim
authors.forename: Adam A
authors.initials: AA
authors.lastname: Margolin
authors.forename: Meirong
authors.initials: M
authors.lastname: Guo
authors.forename: Jimmy
authors.initials: J
authors.lastname: Zhu
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Mason
authors.forename: Terrence W
authors.initials: TW
authors.lastname: Hensle
authors.forename: Vundavalli V V S
authors.initials: VV
authors.lastname: Murty
authors.forename: Paul E
authors.initials: PE
authors.lastname: Grundy
authors.forename: Eric R
authors.initials: ER
authors.lastname: Fearon
authors.forename: Vivette
authors.initials: V
authors.lastname: D'Agati
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Licht
authors.forename: Benjamin
authors.initials: B
authors.lastname: Tycko
mesh_terms: D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000235:genetics*; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D005968:Glutamate Decarboxylase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D007680:Kidney Neoplasms / Q000235:genetics*; D008156:Luciferases / Q000378:metabolism; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics*; D014162:Transfection; D025721:WT1 Proteins / Q000235:genetics*; D009396:Wilms Tumor / Q000235:genetics*; D051153:Wnt Proteins; D051176:beta Catenin
chemical_list: C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D007527:Isoenzymes; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D025721:WT1 Proteins; D051153:Wnt Proteins; D051176:beta Catenin; D008156:Luciferases; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1