title: p53 mutation decreased radiosensitivity in rat yolk sac tumor cell lines.
abstract: OBJECTIVE
  We reported that two established rat yolk sac tumor cell lines differ in their radiosensitivity by 1.7 fold, and the variation is most likely manifested by the differences seen in their apoptotic response. We investigated the relationship between radiosensitivity and p53 in these cell lines.
  
  
  METHODS
  We assessed the status of p53 in cell lines by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and sequence analysis, and also analyzed protein expression of p53, p21, and bax as a function of time after irradiation to determine the signal transduction for p53 by immunoblotting.
  
  
  RESULTS
  A band shift was observed only in exon 7 for the radioresistant NMT-1R cells and no band shift was detected for the radiosensitive NMT-1 cells. A band shift was confirmed also at the mRNA level. Exon 7 of p53 DNA showed a three base substitution of DNA at codon 267 to 268. Expression of p53, p21, and bax proteins in NMT-1R cells did not change after 10 Gy irradiation; however, in NMT-1 cells, the expression of these proteins was increased from 1-12 h after irradiation.
  
  
  CONCLUSIONS
  A loss of p53 function by radiation-induced mutation of p53 decreased the radiosensitivity in these cell lines.
authors.affiliation: Department of Radiology and Radiation Oncology, Gunma University School of Medicine, Maebashi, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Maebayashi
authors.forename: N
authors.initials: N
authors.lastname: Mitsuhashi
authors.forename: T
authors.initials: T
authors.lastname: Takahashi
authors.forename: H
authors.initials: H
authors.lastname: Sakurai
authors.forename: H
authors.initials: H
authors.lastname: Niibe
mesh_terms: D000818:Animals; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000032:analysis; D018240:Endodermal Sinus Tumor / Q000235:genetics*; D016158:Genes, p53 / Q000235:genetics*; D015151:Immunoblotting; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D011518:Proto-Oncogene Proteins / Q000032:analysis; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger / Q000032:analysis; D011836:Radiation Tolerance / Q000235:genetics*; D051381:Rats; D014407:Tumor Cells, Cultured / Q000528:radiation effects; D016159:Tumor Suppressor Protein p53 / Q000032:analysis*; D051028:bcl-2-Associated X Protein
chemical_list: C494828:Bax protein, rat; C493958:Cdkn1a protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein