title: Identification by suppression subtractive hybridization of p21 as a radio-inducible gene in human glioma cells.
abstract: BACKGROUND
  Radio-gene therapy involves the delivery, to tumor cells, of a therapeutic transgene whose expression is controlled by irradiation.
  
  
  METHODS
  Here, we sought to identify novel radio-inducible transcripts in U87MG human malignant glioma cells using suppression subtractive hybridization (SSH).
  
  
  RESULTS
  Of 998 clones from a subtracted library of irradiated U87MG cells, 24 candidate clones were identified by dot blot and 3 clones were confirmed as having been induced by irradiation by Northern blot analysis. All three clones showed 99-100% homology to the cyclin-dependent kinase (cdk) inhibitor, p21(Waf/Cip1). A screening of 12 human malignant glioma cell lines revealed that irradiation increased p21 mRNA expression and p21 protein levels levels in all of the five cell lines retaining p53 wild-type activity in a p53 reporter assay, but in none of seven p53 reporter-negative cell lines.
  
  
  CONCLUSIONS
  Irradiation induces p21 mRNA expression in a strictly p53-dependent manner and may only enhance the expression of a limited number of genes in glioma cells. We conclude that the identification of radio-inducible genomic sequences suitable for radio-gene therapy may turn out to be difficult.
authors.affiliation: Department of Neurology, University Tübingen, School of Medicine, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Rimner
authors.forename: J
authors.initials: J
authors.lastname: Wischhusen
authors.forename: U
authors.initials: U
authors.lastname: Naumann
authors.forename: M
authors.initials: M
authors.lastname: Gleichmann
authors.forename: J P
authors.initials: JP
authors.lastname: Steinbach
authors.forename: M
authors.initials: M
authors.lastname: Weller
mesh_terms: D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects*; D015316:Genetic Therapy / Q000379:methods*; D005910:Glioma / Q000235:genetics* / Q000628:therapy; D006801:Humans; D009693:Nucleic Acid Hybridization; D014407:Tumor Cells, Cultured
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins