Phosphorylated histone H2AX in relation to cell survival in tumor cells and xenografts exposed to single and fractionated doses of X-rays

Radiother Oncol. 2006 Aug;80(2):223-9. doi: 10.1016/j.radonc.2006.07.026. Epub 2006 Aug 14.


Background and purpose: Human tumor cell lines grown as monolayers or xenograft tumors were exposed to single or multiple fractions of X-rays and the ability to use residual gammaH2AX to identify radiosensitive cells was assessed.

Materials and methods: Twenty-four hour after exposure to single or daily fractions of X-rays, human tumor cells from monolayers or xenografts were analyzed for clonogenic surviving fraction. Cells were also fixed and labeled with anti-gammaH2AX antibodies for analysis by flow and image cytometry. The relative amount of residual gammaH2AX and the percentage of cells with <3 foci were compared with the clonogenic surviving fraction measured for the same population.

Results: The fraction of gammaH2AX remaining 24h after X-irradiation relative to peak levels 1h after exposure was correlated with radiosensitivity (SF2) for 18 human tumor cell lines. The fraction of SiHa, C33A and WiDr cells with <3 gammaH2AX foci was predictive of clonogenic surviving fraction for both monolayer cells exposed to either single doses or up to 5 fractions. Similar results were obtained using cells from xenograft tumors of irradiated mice.

Conclusion: The percentage of tumor cells that retain gammaH2AX foci 24h after single or fractionated doses appears to be a useful measure of cellular radiosensitivity that is potentially applicable in the clinic.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Cell Survival / radiation effects
  • Colonic Neoplasms / metabolism*
  • Colonic Neoplasms / pathology
  • Colonic Neoplasms / radiotherapy*
  • Dose Fractionation, Radiation
  • Female
  • Histones / biosynthesis
  • Histones / metabolism*
  • Humans
  • Mice
  • Mice, Inbred NOD
  • Mice, SCID
  • Phosphorylation / radiation effects
  • Uterine Cervical Neoplasms / metabolism*
  • Uterine Cervical Neoplasms / pathology
  • Uterine Cervical Neoplasms / radiotherapy*
  • X-Rays
  • Xenograft Model Antitumor Assays


  • H2AX protein, human
  • Histones