Potential for the G2/M arrest assay to predict patient susceptibility to severe reactions following radiotherapy.
OBJECTIVE
Cell-cycle regulation and checkpoint activation are crucial factors for radiation-induced DNA damage processing. The G2/M phase arrest was assessed in lymphoblastoid cell lines and phytohemagglutinin-stimulated T-lymphocytes of different radiosensitivities to study the relationship of G2/M arrest to radiosensitivity.


METHODS
G2/M arrest was analyzed after in vitro irradiation by 2 and 5 Gy of ionizing radiation up to 6 days using 17 lymphoblastoid cell lines from healthy individuals, ataxia-telangiectasia (AT) patients, Nijmegen breakage syndrome (NBS) patients and cancer patients with clinically increased radiosensitivity. In a second approach, phytohemagglutinin-stimulated T-lymphocytes from 15 healthy individuals, twelve cancer patients, and five cancer patients hypersensitive to ionizing radiation were studied. Image cytometry was performed to analyze G2/M arrest.


RESULTS
Two of the three AT cell lines showed markedly increased G2/M arrest compared to controls. NBS cells were comparable to controls up to day 3, but then demonstrated a slightly increased G2/M arrest. Two of the six radiosensitive lymphoblast cell lines and the five radiosensitive cancer patients' T-lymphocytes assayed showed a reduction in G2/M arrest, while healthy individuals showed no difference from cancer patients.


CONCLUSIONS
The interrelation between G2/M arrest and radiosensitivity is not readily apparent since a variety of radiosensitive cells from patients with radiosensitive syndromes and patients identified as radiosensitive following radiation treatment showed inconsistent G2/M arrest dynamics. Secondary effects, like loss of clonogenicity, G1/S phase arrest and failure of G2/M arrest may contribute to variation of the G2/M arrest endpoint and obscure assessment of cellular radiosensitivity using this method.
Perez
Alexandra
A
Department of Radiation Oncology, Friedrich Alexander University Erlangen-Nuremberg, Erlangen, Germany.
Grabenbauer
Gerhard G
GG
Sprung
Carl N
CN
Sauer
Rolf
R
Distel
Luitpold V R
LV
D000328:Adult; D000368:Aged; D001681:Biological Assay / Q000379:methods*; D002453:Cell Cycle / Q000528:radiation effects*; D004198:Disease Susceptibility / Q000175:diagnosis; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008214:Lymphocytes / Q000166:cytology* / Q000528:radiation effects*; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000175:diagnosis* / Q000209:etiology; D011836:Radiation Tolerance / Q000502:physiology*; D011878:Radiotherapy / Q000009:adverse effects*