Identification of a novel pro-apopotic function of NF-kappaB in the DNA damage response.
NF-kappaB is activated by DNA-damaging anticancer drugs as part of the cellular stress response. However, the consequences of drug-induced NF-kappaB activation are still only partly understood. To investigate the impact of NF-kappaB on the cell's response to DNA damage, we engineered glioblastoma cells that stably express mutant IkappaBalpha superrepressor (IkappaBalpha-SR) to block NF-kappaB activation. Here, we identify a novel pro-apoptotic function of NF-kappaB in the DNA damage response in glioblastoma cells. Chemotherapeutic drugs that intercalate into DNA and inhibit topoisomerase II such as Doxorubicin, Daunorubicin and Mitoxantrone stimulate NF-kappaB DNA binding and transcriptional activity prior to induction of cell death. Importantly, specific inhibition of drug-induced NF-kappaB activation by IkappaBalpha-SR or RNA interference against p65 significantly reduces apoptosis upon treatment with Doxorubicin, Daunorubicin or Mitoxantrone. NF-kappaB exerts this pro-apoptotic function especially after pulse drug exposure as compared to continuous treatment indicating that the contribution of NF-kappaB becomes relevant during the recovery phase following the initial DNA damage. Mechanistic studies show that NF-kappaB inhibition does not alter Doxorubicin uptake and efflux or cell cycle alterations. Genetic silencing of p53 by RNA interference reveals that NF-kappaB promotes drug-induced apoptosis in a p53-independent manner. Intriguingly, drug-mediated NF-kappaB activation results in a significant increase in DNA damage prior to the induction of apoptosis. By demonstrating that NF-kappaB promotes DNA damage formation and apoptosis upon pulse treatment with DNA intercalators, our findings provide novel insights into the control of the DNA damage response by NF-kappaB in glioblastoma.
Karl
Sabine
S
University Children's Hospital, Ulm, Germany.
Pritschow
Yvonne
Y
Volcic
Meta
M
Häcker
Sabine
S
Baumann
Bernd
B
Wiesmüller
Lisa
L
Debatin
Klaus-Michael
KM
Fulda
Simone
S
D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000378:metabolism; D004317:Doxorubicin / Q000378:metabolism / Q000494:pharmacology; D005909:Glioblastoma / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007364:Intercalating Agents / Q000494:pharmacology; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D004273:DNA, Neoplasm; D007364:Intercalating Agents; D016328:NF-kappa B; D016159:Tumor Suppressor Protein p53; D004317:Doxorubicin