Beta-catenin mutations correlate with over expression of C-myc and cyclin D1 Genes in bladder cancer.
OBJECTIVE
We hypothesized that over expression of c-myc and cyclin D1 genes is transcriptionally activated by beta-catenin mutation independent of gene amplification in bladder cancer. To test this hypothesis we investigated the relationship of beta-catenin mutation to c-myc and cyclin D1 mRNA with special reference to the changes in copy number of the 2 genes.


METHODS
Genomic DNA and total RNA were extracted from 59 bladder cancer specimens and from 31 histologically normal specimens of bladder mucosa. We performed beta-catenin deletion screening by polymerase chain reaction (PCR) using primers spanning exons 3 (including the glycogen synthase kinase-3beta consensus motif), 5 and 6. Mutational changes in beta-catenin in exons 3, 5 and 6 were detected by each PCR-single strand conformational polymorphism analysis followed by direct DNA sequencing. mRNA expression and copy numbers of c-myc and cyclin D1 were determined by semiquantitative reverse transcriptase-PCR and competitive genomic PCR.


RESULTS
Missense mutations of beta-catenin found in grade 3 bladder cancer were involved in the consensus motif of glycogen synthase kinase-3beta in exon 3. These cancers showed strong intracellular accumulation of beta-catenin and intense expression of c-myc and cyclin D1 mRNA compared with samples lacking the beta-catenin mutation. When grade 3 cancers were compared, expression levels of c-myc and cyclin D1 mRNA were still higher in those with versus without the beta-catenin mutation. In bladder cancers with beta-catenin mutations copy numbers of the c-myc and cyclin D1 genes did not amplify.


CONCLUSIONS
Bladder cancer harboring a beta-catenin mutation may represent aggressive biological behavior with enhanced proliferating activity. These findings are important for understanding the role of beta-catenin mutation in the pathogenesis of bladder cancer.
Shiina
Hiroaki
H
Department of Urology, Shimane Medical University, Izumo, Japan.
Igawa
Mikio
M
Shigeno
Kazushi
K
Terashima
Masaharu
M
Deguchi
Masao
M
Yamanaka
Masaki
M
Ribeiro-Filho
Leopoldo
L
Kane
Christopher J
CJ
Dahiya
Rajvir
R
D002295:Carcinoma, Transitional Cell / Q000235:genetics* / Q000473:pathology; D019938:Cyclin D1 / Q000235:genetics*; D003598:Cytoskeletal Proteins / Q000235:genetics*; D004252:DNA Mutational Analysis; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D020125:Mutation, Missense / Q000235:genetics*; D009367:Neoplasm Staging; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics*; D001743:Urinary Bladder / Q000473:pathology; D001749:Urinary Bladder Neoplasms / Q000235:genetics* / Q000473:pathology; D051176:beta Catenin
C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D015534:Trans-Activators; D051176:beta Catenin; D019938:Cyclin D1