title: Frequent p16/MTS1 inactivation in early stages of urothelial carcinoma of the bladder is not associated with tumor recurrence.
abstract: OBJECTIVE
  p16, located at chromosome 9p21, is a negative regulator of G1 cell checkpoint and functions as tumor suppressor gene. Only few data are available on the frequency and clinical relevance of p16 alterations in Ta, T1 transitional cell carcinoma (TCC) of the bladder. We investigated 40 patients with Ta, T1 TCC of the bladder for p16 alterations (mutations, homozygote deletions, allelic loss) or reduced p16 immunoreaction.
  
  
  METHODS
  DNA was prepared from microdissected tumor tissue from 40 patients with pTa, pT1 TCC of the bladder (pTa: 18 patients; pT1: 22 patients; grade 1: 7 patients; grade 2: 28 patients; grade 3: 5 patients). Mutation screening was performed using polymerase chain reaction (PCR), single-strand conformation polymorphism (SSCP) and direct sequencing at exon 1 and exon 2. Detection of homozygote deletions was performed using multiplex PCR. Immunohistochemistry (IHC) was performed using an anti-human monoclonal antibody (p16, Pharmingen). Allelic loss was detected by PCR using three different microsatellite markers (D9S161, D9S171, D9S319).
  
  
  RESULTS
  SSCP and direct sequencing revealed 3 cases of base substitution which turned out to be natural polymorphisms. Homozygote deletions were not detected in any case. p16 IHC revealed reduced p16 expression (<5% positive nuclei) in 10 patients; 30 patients had a positive reaction (> or =5% positive nuclei) and 10 patients a strong positive reaction (> or =50% positive nuclei). Thirteen of 37 informative cases revealed loss of heterozygosity (LOH) with at least one marker. After a median follow-up of 23 months, 15 patients suffered from disease recurrence. Statistical analysis using Kaplan-Meier analysis and the log-rank test did not reveal significant association of recurrence-free interval and detection of LOH (p = 0.34) or p16 IHC (p = 0.9).
  
  
  CONCLUSIONS
  We present a comprehensive evaluation of chromosome 9p21 alterations including p16 analysis and clinical follow-up data. Although p16 mutations and homozygote deletions are rarely detectable in Ta, T1 TCC, the reduction of p16 expression and the frequent hemizygote deletions at 9p21 suggest an early involvement of chromosome 9p and p16 in superficial TCC.
authors.affiliation: Department of Urology, University of Hamburg, University Hospital Eppendorf, Germany. friedrich@uke.uni-hamburg.de
authors.forename: M G
authors.initials: MG
authors.lastname: Friedrich
authors.forename: C
authors.initials: C
authors.lastname: Blind
authors.forename: K
authors.initials: K
authors.lastname: Milde-Langosch
authors.forename: A
authors.initials: A
authors.lastname: Erbersdobler
authors.forename: S
authors.initials: S
authors.lastname: Conrad
authors.forename: T
authors.initials: T
authors.lastname: Löning
authors.forename: P
authors.initials: P
authors.lastname: Hammerer
authors.forename: H
authors.initials: H
authors.lastname: Huland
mesh_terms: D002295:Carcinoma, Transitional Cell / Q000235:genetics* / Q000473:pathology; D002872:Chromosome Deletion; D002899:Chromosomes, Human, Pair 9 / Q000235:genetics*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism; D005500:Follow-Up Studies; D020868:Gene Silencing; D019942:Genes, p16; D006801:Humans; D007150:Immunohistochemistry; D009364:Neoplasm Recurrence, Local / Q000235:genetics* / Q000378:metabolism; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D001749:Urinary Bladder Neoplasms / Q000235:genetics* / Q000473:pathology
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16