End-joining deficiency and radiosensitization induced by gemcitabine.
The mechanism of radiosensitization by gemcitabine (2',2'-difluoro-2'-deoxycytidine, dFdC) is not exactly known. We investigated the possible role of inhibition of the repair of DNA double-strand breaks by dFdC by measuring the extent of radiosensitization in different cell lines deficient and proficient in components of nonhomologous end-joining and in the parental cell lines. Different cell lines were incubated with 0.5 and 5 microM dFdC for 4 h. Cells deficient in DNA-dependent protein-kinase catalytic subunit (V3) showed sensitization similar to that of wild-type cells (AAS) and complemented cells (V3+YAC). Ku80-deficient cells (xrs5 and xrs6) showed even more radiosensitization by dFdC as compared with wild-type CHO-K1. However, Ku80-complemented cell lines (xrs5+huKu80 and xrs6+haKu80) did not show radiosensitization. The differences in dFdC-mediated radiosensitization were not attributable to different changes in deoxynucleotide triphosphate levels and cell cycle distribution. We conclude that a functional nonhomologous end-joining pathway is not required for dFdC-mediated radiosensitization.
Department of Pulmonary Diseases, University Hospital, Groningen, The Netherlands. j.w.g.van.putten@int.azg.nl
van Putten JWG
Groen HJM
K
K
Smid
G J
GJ
Peters
H H
HH
Kampinga
D000818:Animals; D034961:Antigens, Nuclear; D016466:CHO Cells; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D018244:Chromosomes, Artificial, Yeast / Q000235:genetics; D006224:Cricetinae; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004265:DNA Helicases; D004260:DNA Repair / Q000187:drug effects* / Q000502:physiology; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000235:genetics; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000494:pharmacology*; D003854:Deoxyribonucleotides / Q000378:metabolism; D006801:Humans; D000072200:Ku Autoantigen; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D011836:Radiation Tolerance / Q000187:drug effects / Q000235:genetics; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D014162:Transfection; D000093542:Gemcitabine
D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D003854:Deoxyribonucleotides; D009687:Nuclear Proteins; D011838:Radiation-Sensitizing Agents; D003841:Deoxycytidine; D004247:DNA; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen; D000093542:Gemcitabine