Differential inhibitory effect of OK-1035 on DNA repair in L5178Y murine lymphoma sublines with functional or defective repair of double strand breaks.
Radiosensitive L5178Y-S (LY-S) subline and its parental, more radioresistant L5178Y-R (LY-R) subline differ in DNA double strand break (DSB) rejoining. In this work we examined by comet assay the repair of X-ray-induced DNA damage in LY cells treated with OK-1035, a potent DNA-PK inhibitor. The unirradiated cells differ: the respective tail moment values for LY-R and LY-S cells were 9.62+/-2.84 and 3.52+/-0.1, reflecting the susceptibility to lysis conditions as well as the possible endogenous (oxidative) damage level. The level of initial DNA damage measured after irradiation (8 Gy) at DNA-denaturing pH was the same in both LY sublines: the mean tail moment values +/- SD were 92.93+/-10.39 for LY-R cells and 94.93+/-12.94 for LY-S cells. In LY-S cells the repair of 8 Gy X-ray-induced damage proceeded identically in the presence or absence of 2 mM OK-1035 to the same level of residual damage. In contrast, the level of residual damage in inhibitor treated LY-R cells was considerably higher than that in the untreated cells. Moreover, the inhibitor affected LY-R cells in G1 and S phases and not those in G2, in agreement with cell-cycle specificity of DNA-PK. These results may indicate that the DSB repair defect previously identified in LY-S cells is due to a lack of function of DNA-PK or its impaired activation in the irradiated cells.
Kruszewski
M
M
Department of Radiobiology and Health Protection, Institute of Nuclear Chemistry and Technology, Warsaw, Poland. marcinkr@orange.ichtj.waw.pl
Wojewódzka
M
M
Iwaneńko
T
T
Szumiel
I
I
Okuyama
A
A
D000818:Animals; D002453:Cell Cycle; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D004273:DNA, Neoplasm / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006835:Hydrazones / Q000494:pharmacology*; D007940:Leukemia L5178 / Q000378:metabolism; D051379:Mice; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011728:Pyridones / Q000494:pharmacology*; D011836:Radiation Tolerance; D014407:Tumor Cells, Cultured
C095985:3-cyano-5-(4-pyridyl)-6-hydrazonomethyl-2-pyridone; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D006835:Hydrazones; D011728:Pyridones; D051747:DNA-Activated Protein Kinase; D017346:Protein Serine-Threonine Kinases