Beta-catenin mutations correlate with over expression of C-myc and cyclin D1 Genes in bladder cancer

J Urol. 2002 Nov;168(5):2220-6. doi: 10.1097/01.ju.0000033989.57509.c5.

Abstract

Purpose: 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.

Materials and 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.

MeSH terms

  • Carcinoma, Transitional Cell / genetics*
  • Carcinoma, Transitional Cell / pathology
  • Cyclin D1 / genetics*
  • Cytoskeletal Proteins / genetics*
  • DNA Mutational Analysis
  • Gene Expression Regulation, Neoplastic / physiology
  • Humans
  • Mutation, Missense / genetics*
  • Neoplasm Staging
  • Proto-Oncogene Proteins c-myc / genetics*
  • RNA, Messenger / genetics
  • Reverse Transcriptase Polymerase Chain Reaction
  • Trans-Activators / genetics*
  • Urinary Bladder / pathology
  • Urinary Bladder Neoplasms / genetics*
  • Urinary Bladder Neoplasms / pathology
  • beta Catenin

Substances

  • CTNNB1 protein, human
  • Cytoskeletal Proteins
  • Proto-Oncogene Proteins c-myc
  • RNA, Messenger
  • Trans-Activators
  • beta Catenin
  • Cyclin D1