title: Inverse correlation between RER+ status and p53 mutation in colorectal cancer cell lines.
abstract: The high point mutation rate of replication error-prone (RER+) cells could theoretically lead to inactivation of the p53 gene by polyclonal mutations, which might explain the conflicting results that have been published on the p53 status of RER+ colon cancers. To address this issue, we tested the p53 status of 21 human colorectal cancer cell lines, including four showing microsatellite instability (RER+ phenotype). Denaturing gradient gel electrophoresis (DGGE) followed by sequencing showed that all four RER+ cell lines were wild type for p53 while 15 of the 17 RER- cell lines contained p53 mutations (P=0.001). Eight cell lines (four RER+ and four RER-) were analysed using three complementary methods to test more rigorously the polyclonal mutation hypothesis. (i) Of 87 single-cell clones (seven to 14 per cell line) examined by DGGE, only those derived from known p53 mutant cell lines showed altered profiles. (ii) Antibody DO-7 stained more than 80% of nuclei from the p53 mutant cell lines, but only 15% of nuclei from the RER+ cell lines. (iii) A yeast functional assay which can simultaneously detect polyclonal mutations at over 500 different sites in the p53 cDNA scored all four RER+ cell lines as containing only transcriptionally active p53. These data thus do not support the polyclonal mutation hypothesis and instead suggest that mismatch repair deficiency provides a p53-independent pathway for development of colorectal cancers.
authors.affiliation: Inserm U 434, Génétique des Tumeurs, Institut Curie, Paris, France.
authors.forename: P H
authors.initials: PH
authors.lastname: Cottu
authors.forename: F
authors.initials: F
authors.lastname: Muzeau
authors.forename: A
authors.initials: A
authors.lastname: Estreicher
authors.forename: J F
authors.initials: JF
authors.lastname: Fléjou
authors.forename: R
authors.initials: R
authors.lastname: Iggo
authors.forename: G
authors.initials: G
authors.lastname: Thomas
authors.forename: R
authors.initials: R
authors.lastname: Hamelin
mesh_terms: D015179:Colorectal Neoplasms / Q000235:genetics*; D004260:DNA Repair; D016158:Genes, p53 / Q000235:genetics*; D006801:Humans; D018895:Microsatellite Repeats / Q000235:genetics; D017354:Point Mutation / Q000235:genetics*; D014407:Tumor Cells, Cultured