The Radioprotective Effect of the 24 kDa FGF-2 Isoform in HeLa Cells Is Related to an Increased Expression and Activity of the DNA Dependent Protein Kinase (DNA-PK) Catalytic Subunit

Oncogene. 2002 Sep 19;21(42):6471-9. doi: 10.1038/sj.onc.1205838.

Abstract

We previously reported that overexpression of the 24 kDa basic fibroblast factor (or FGF-2) isoform provides protection from the cytotoxic effect of ionizing radiation (IR). DNA double-strand breaks (DSB), the IR-induced lethal lesions, are mainly repaired in human cells by non-homologous end joining system (NHEJ). NHEJ reaction is dependent on the DNA-PK holoenzyme (composed of a regulatory sub-unit, Ku, and a catalytic sub-unit, DNA-PKcs) that assembles at sites of DNA damage. We demonstrated here that the activity of DNA-PK was increased by twofold in two independent radioresistant cell lines, HeLa 3A and CAPAN A3, over expressing the 24 kDa FGF-2. This increase was associated with an overexpression of the DNA-PKcs without modification of Ku expression or activity. This overexpression was due to an up-regulation of the DNA-PKcs gene transcription by the 24 kDa FGF-2 isoform. Finally, HeLa 3A cells exhibited the hallmarks of phenotypic changes associated with the overexpression of an active DNA-PKcs. Indeed, a faster repair rate of DSB and sensitization to IR by wortmannin was observed in these cells. Our results represent the characterization of a new mechanism of control of DNA repair and radioresistance in human tumor cells dependent on the overproduction of the 24 kDa FGF-2 isoform.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Androstadienes / metabolism
  • Androstadienes / pharmacology*
  • Antigens, Nuclear*
  • Blotting, Western
  • DNA Damage / radiation effects*
  • DNA Helicases*
  • DNA Repair*
  • DNA-Activated Protein Kinase
  • DNA-Binding Proteins / metabolism
  • Dose-Response Relationship, Drug
  • Electrophoretic Mobility Shift Assay
  • Fibroblast Growth Factor 2 / pharmacology*
  • HeLa Cells / metabolism
  • HeLa Cells / radiation effects*
  • Humans
  • Ku Autoantigen
  • Nuclear Proteins / metabolism
  • Phenotype
  • Protein Isoforms / pharmacology
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA / metabolism
  • Radiation Tolerance
  • Radiation-Protective Agents / pharmacology*
  • Time Factors
  • Transcription, Genetic
  • Up-Regulation
  • Wortmannin

Substances

  • Androstadienes
  • Antigens, Nuclear
  • DNA-Binding Proteins
  • Nuclear Proteins
  • Protein Isoforms
  • Radiation-Protective Agents
  • Fibroblast Growth Factor 2
  • RNA
  • DNA-Activated Protein Kinase
  • PRKDC protein, human
  • Protein-Serine-Threonine Kinases
  • DNA Helicases
  • XRCC5 protein, human
  • Xrcc6 protein, human
  • Ku Autoantigen
  • Wortmannin