Ionizing radiation-induced NF-kappaB activation requires PARP-1 function to confer radioresistance.
Recent reports implicate poly(ADP-ribose) polymerase-1 (PARP-1) in the activation of nuclear factor kappaB (NF-kappaB). We investigated the role of PARP-1 in the NF-kappaB signalling cascade induced by ionizing radiation (IR). AG14361, a potent PARP-1 inhibitor, was used in two breast cancer cell lines expressing different levels of constitutively activated NF-kappaB, as well as mouse embryonic fibroblasts (MEFs) proficient or deficient for PARP-1 or NF-kappaB p65. In the breast cancer cell lines, AG14361 had no effect on IR-induced degradation of IkappaBalpha or nuclear translocation of p50 or p65. However, AG14361 inhibited IR-induced NF-kappaB-dependent transcription of a luciferase reporter gene. Similarly, in PARP-1(-/-) MEFs, IR-induced nuclear translocation of p50 and p65 was normal, but kappaB binding and transcriptional activation did not occur. AG14361 sensitized both breast cancer cell lines to IR-induced cell killing, inhibited IR-induced XIAP expression and increased caspase-3 activity. However, AG14361 failed to increase IR-induced caspase activity when p65 was knocked down by siRNA. Consistent with this, AG14361 sensitized p65(+/+) but not p65(-/-) MEFs to IR. We conclude that PARP-1 activity is essential in the upstream regulation of IR-induced NF-kappaB activation. These data indicate that potentiation of IR-induced cytotoxicity by AG14361 is mediated solely by inhibition of NF-kappaB activation.
Veuger
S J
SJ
Northern Institute for Cancer Research, Medical School, University of Newcastle, Newcastle upon Tyne, Tyne and Wear, UK.
Hunter
J E
JE
Durkacz
B W
BW
D021581:Active Transport, Cell Nucleus; D017209:Apoptosis; D052176:Azulenes / Q000494:pharmacology; D001569:Benzodiazepines / Q000494:pharmacology; D001943:Breast Neoplasms / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects; D006801:Humans; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D011839:Radiation, Ionizing; D051996:Transcription Factor RelA / Q000378:metabolism*
C479234:1-(4-dimethylaminomethylphenyl)-8,9-dihydro-7H-2,7,9a-benzo(cd)azulen-6-one; D052176:Azulenes; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; C498143:RELA protein, human; D034741:RNA, Small Interfering; D051996:Transcription Factor RelA; D001569:Benzodiazepines; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases