Low-dose hypersensitive gammaH2AX response and infrequent apoptosis in epidermis from radiotherapy patients.
OBJECTIVE
A low-dose hypersensitivity to radiation can be observed in vitro for many human cell types in terms of increased cell kill per dose unit for doses below 0.5Gy. Quantification of the double-strand break marker gammaH2AX in samples taken in clinical radiotherapy practice has the potential to provide important information about how induction and repair of severe DNA damage and apoptosis are linked to low-dose hypersensitivity.


METHODS
The effects of exposure to low doses (0.05-1.1Gy) were investigated in skin biopsies taken from prostate cancer patients undergoing the first week of radiotherapy. gammaH2AX foci and apoptotic cells were visualised by immunohistochemistry and quantified by image analysis.


RESULTS
The gammaH2AX foci pattern in biopsies taken 30min after a single fraction revealed a low-dose hypersensitivity below 0.3Gy (p=0.0009). The result was consistent for repeated fractions (p=0.00001). No decrease in foci numbers could be detected when comparing biopsies taken 30min and 2h after single fractions of 0.4 and 1.2Gy. The result was consistent for repeated fractions. Only 43 of 168,000 cells in total were identified as apoptotic, yet a dose dependency could be detected after 1week of radiotherapy (p=0.003).


CONCLUSIONS
We describe a method based on gammaH2AX to study DNA damage response and apoptosis in a clinical setting. A gammaH2AX hypersensitive response to low doses can be observed in epidermal skin, already 30min following delivered fraction. A very low frequency of apoptosis in normal epithelium suggests that this effect is not an important part of the in vivo response to low doses.
Department of Oncology, Radiology and Clinical Immunology, Uppsala University, Uppsala, Sweden. qvasim@qvasim.com
Martin
M
Simonsson
Fredrik
F
Qvarnström
Jan
J
Nyman
Karl-Axel
KA
Johansson
Hans
H
Garmo
Ingela
I
Turesson
D017209:Apoptosis / Q000528:radiation effects*; D001706:Biopsy; D002467:Cell Nucleus; D004249:DNA Damage; D004260:DNA Repair / Q000528:radiation effects; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D004817:Epidermis / Q000528:radiation effects*; D006657:Histones / Q000528:radiation effects*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D008297:Male; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011836:Radiation Tolerance; D011879:Radiotherapy Dosage
C468783:H2AX protein, human; D006657:Histones