title: p53 mutational status and survival of human breast cancer MCF-7 cell variants after exposure to X rays or fission neutrons.
abstract: We assessed cytotoxicity of X rays or fission neutrons and the status of the p53 tumor suppressor gene in irradiated and unirradiated actively growing cultures of human breast cancer MCF-7 cells. One parental or wild-type (WT) and the other resistant to adriamycin (ADRR) were studied within the same experiment. We found that, relative to MCF-7 WT cells, MCF-7 ADRR cells exhibited a small but significant resistance to X rays, but not to fission neutrons. Single-strand conformation polymorphism analysis followed by DNA sequencing and immunohistochemical staining with a p53 protein-specific antibody performed on pooled polyclonal or monoclonal populations of MCF-7 WT or ADRR cells confirmed that wild-type cells have two normal copies of the p53 gene. We discovered p53 loss of heterozygosity and a point mutation in the remaining allele of the p53 gene in adriamycin-resistant cells. This mutation is a splice acceptor site change on the upstream border of exon 5 and results in p53 protein overexpression. No new p53 mutations were observed in MCF-7 WT or ADRR cells surviving either X or fission-neutron irradiations. Our results suggest that the mutant p53 allele affects cytotoxic outcomes of DNA damage from X rays but not from neutrons.
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore 21201, USA.
authors.forename: E K
authors.initials: EK
authors.lastname: Balcer-Kubiczek
authors.forename: J
authors.initials: J
authors.lastname: Yin
authors.forename: K
authors.initials: K
authors.lastname: Lin
authors.forename: G H
authors.initials: GH
authors.lastname: Harrison
authors.forename: J M
authors.initials: JM
authors.lastname: Abraham
authors.forename: S J
authors.initials: SJ
authors.lastname: Meltzer
mesh_terms: D001483:Base Sequence; D001943:Breast Neoplasms; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D017931:DNA Primers; D004317:Doxorubicin / Q000633:toxicity; D005091:Exons; D017353:Gene Deletion; D016158:Genes, p53 / Q000528:radiation effects*; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009502:Neutrons; D009680:Nuclear Fission; D017354:Point Mutation; D016133:Polymerase Chain Reaction / Q000379:methods; D011110:Polymorphism, Genetic; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay; D016159:Tumor Suppressor Protein p53 / Q000032:analysis / Q000096:biosynthesis*; D014965:X-Rays
chemical_list: D017931:DNA Primers; D016159:Tumor Suppressor Protein p53; D004317:Doxorubicin