[Relationship of HepG2 cell sensitivity to continuous low dose-rate irradiation with ataxia-telangiectasia mutated phosphorylation].
OBJECTIVE
To investigate the changes of ataxia-telangiectasia mutated (ATM) phosphorylation in HepG(2) cells in relation to HepG(2) cell survival under continuous low dose-rate irradiation.


METHODS
HepG(2) cells were exposed to equivalent irradiation doses delivered at either a continuous low dose-rate (7.76 cGy/h) or a high dose-rate (4500 cGy/h), and the phosphorylated ATM proteins and surviving fraction of HepG(2) cells after the exposures were compared.


RESULTS
The phosphorylation of ATM protein was maximal at 0.5 Gy irradiation delivered at either a high doserate or a continuous low doserate. As the radiation dose increased, ATM protein phosphorylation decreased under continuous low dose-rate irradiation, but remained stable under high dose-rate irradiation. With comparable ATM protein phosphorylation induced by continuous low dose-rate irradiation and high dose-rate irradiation, there was no significant difference in the surviving fraction of HepG(2) cells (P>0.05), but at a significantly lower ATM protein phosphorylation level than that induced by high dose-rate irradiation, continuous low dose-rate irradiation resulted in increased cell killing (P<0.01).


CONCLUSIONS
Continuous low dose-rate irradiation increases HepG(2) cells radiosensitivity as compared with high dose-rate irradiation. Increased cell killing following continuous low dose-rate irradiation is associated with reduced phosphorylated ATM protein, and inhibition of ATM phosphorylation may increase the radiosensitivity of HepG(2) cells.
Mei
Que-lin
QL
First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China. meique_lin@163.com
Yang
Jian-yong
JY
DU
Duan-ming
DM
Chen
Zai-zhong
ZZ
Liu
Peng-cheng
PC
D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D051379:Mice; D010766:Phosphorylation / Q000528:radiation effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011836:Radiation Tolerance / Q000528:radiation effects*; D013997:Time Factors; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases