title: Histologic-genetic mapping by allele-specific PCR reveals intraurothelial spread of p53 mutant tumor clones.
abstract: Common and clinically important features of urothelial carcinomas are multifocality and a high rate of recurrence. Molecular studies demonstrated that multifocal tumors are frequently composed of one tumor clone spreading throughout the urothelial tract. A combination of histologic and genetic mapping of cystectomy specimens from bladder cancer patients is a valuable tool to study bladder carcinogenesis and tumor cell spread by correlating urothelial morphologic features and defined genetic alterations. In the present study, the primary tumors of 14 cystectomy specimens were investigated for p53 protein overexpression by immunohistochemistry and p53 gene mutation by genomic sequencing. Seven tumors showed a strong nuclear staining for the p53 protein. In six of seven tumors, a p53 gene mutation was detected. Allele-specific PCR of defined p53 mutations was established in five of six cases with a p53 mutation. Subsequent screening of the entire urothelial lining of each cystectomy specimen by allele-specific PCR revealed p53-mutant cell clones in urothelial patches with carcinoma in situ and dysplasia, but also frequently in histomorphologically normal urothelium adjacent to the tumor. The pattern of tumor cell spread indicated a continuous intraurothelial growth of the p53-mutant clone. P53 immunohistochemistry visually confirmed the presence of mutant cells in most of these samples. We conclude that allele-specific PCR is a highly sensitive and reliable method for tracking specific p53 mutant clones in the urothelium. Moreover, the detection of p53-mutant cells in histologically normal or preneoplastic urothelial areas in four patients with invasive bladder cancer indicates an extensive intraurothelial tumor cell spread. The excellent correlation of immunohistochemically positive urothelial patches with the presence of a specific mutation highlights the biologic significance of p53-positive cells in the urothelium of tumor patients.
authors.affiliation: Institute of Pathology, University of Regensburg, Regensburg, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Stoehr
authors.forename: Ruth
authors.initials: R
authors.lastname: Knuechel
authors.forename: Joerg
authors.initials: J
authors.lastname: Boecker
authors.forename: Hagen
authors.initials: H
authors.lastname: Blaszyk
authors.forename: Ruediger
authors.initials: R
authors.lastname: Schmitt
authors.forename: Thomas
authors.initials: T
authors.lastname: Filbeck
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Hofstaedter
authors.forename: Arndt
authors.initials: A
authors.lastname: Hartmann
mesh_terms: D000368:Aged; D000483:Alleles; D005260:Female; D016158:Genes, p53; D006801:Humans; D007150:Immunohistochemistry; D019656:Loss of Heterozygosity; D008297:Male; D008875:Middle Aged; D009154:Mutation; D016133:Polymerase Chain Reaction / Q000379:methods*; D016159:Tumor Suppressor Protein p53 / Q000032:analysis; D001749:Urinary Bladder Neoplasms / Q000235:genetics* / Q000473:pathology
chemical_list: D016159:Tumor Suppressor Protein p53