Phosphorylation of histone H2AX as a measure of radiosensitivity.
OBJECTIVE
Phosphorylation of histone H2AX (gammaH2AX) occurs rapidly in response to the presence of DNA double-strand breaks and is thought to recruit repair enzymes to these sites. We examined the possibility that expression of phosphorylated H2AX could provide information on tumor and/or normal tissue sensitivity to radiation.


METHODS
Flow cytometry of gammaH2AX antibody-stained single cells was used to measure gammaH2AX intensity in cultured cell lines, tumor cells, and normal tissues.


RESULTS
The rate of disappearance of gammaH2AX during the first few hours after irradiation was generally faster in more radioresistant tumor and normal cell lines, but slower in radiosensitive cells and normal tissues from C3H mice. An exception was testis, which showed a high background and rapid loss rate. Levels of gammaH2AX were at least three times higher in well-oxygenated cells than in anoxic cells, and the oxygen concentration that produced a half-maximal response was 0.55%. Hypoxic cells could be detected in SiHa xenografts as a subpopulation with lower expression of gammaH2AX.


CONCLUSIONS
Analysis of gammaH2AX has the potential to provide useful information on tumor and normal cell response to ionizing radiation after exposure to clinically relevant doses of radiation.
Olive
Peggy L
PL
Department of Medical Biophysics, British Columbia Cancer Research Centre, 601 W. 10th Avenue, Vancouver, BC V5Z 1L3, Canada. polive@bccancer.bc.ca
Banáth
Judit P
JP
D000818:Animals; D015687:Cell Hypoxia; D045744:Cell Line, Tumor / Q000378:metabolism / Q000528:radiation effects; D004260:DNA Repair; D005434:Flow Cytometry; D006657:Histones / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008809:Mice, Inbred C3H; D009363:Neoplasm Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011836:Radiation Tolerance
D006657:Histones; D009363:Neoplasm Proteins; C475961:gamma-H2AX protein, mouse