Stabilization of p53 is a novel mechanism for proapoptotic function of NF-kappaB.
Both pro- and antiapoptotic activities of NF-kappaB transcription factor have been observed; however, less is known about the mechanism by which NF-kappaB induces apoptosis. To elucidate how NF-kappaB regulates proapoptotic signaling, we performed functional analyses using wild-type, ikk1(-/-), ikk2(-/-), rela(-/-) murine fibroblasts, MDAPanc-28/Puro, MDAPanc-28/IkappaBalphaM, and HCT116/p53(+/+) and HCT116/p53(-/-) cells with investigational anticancer agent doxycycline as a superoxide inducer for generating apoptotic stimulus. In this report, we show that doxycycline increased superoxide generation and subsequently activated NF-kappaB, which in turn up-regulated p53 expression and increased the stability and DNA binding activity of p53. Consequently, NF-kappaB-dependent p53 activity induced the expression of p53-regulated genes PUMA and p21(waf1) as well as apoptosis. Importantly, lack of RelA, IKK, and p53 as well as expression of a dominant negative IkappaBalpha (IkappaBalphaM) inhibited NF-kappaB-dependent p53 activation and apoptosis. The doxycycline-induced NF-kappaB activation was not inhibited in HCT116/p53(-/-) cells. Our results demonstrate that NF-kappaB plays an essential role in activation of wild-type p53 tumor suppressor to initiate proapoptotic signaling in response to overgeneration of superoxide. Thus, these findings reveal a mechanism of NF-kappaB-regulated proapoptotic signaling.
Fujioka
Shuichi
S
Department of Surgical Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Schmidt
Christian
C
Sclabas
Guido M
GM
Li
Zhongkui
Z
Pelicano
Hélène
H
Peng
Bailu
B
Yao
Alice
A
Niu
Jiangong
J
Zhang
Wei
W
Evans
Douglas B
DB
Abbruzzese
James L
JL
Huang
Peng
P
Chiao
Paul J
PJ
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis / Q000235:genetics; D015536:Down-Regulation; D004318:Doxycycline / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D006801:Humans; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D016328:NF-kappa B / Q000172:deficiency / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics; D010766:Phosphorylation; D011480:Protease Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics; D051736:Proto-Oncogene Proteins c-mdm2; D011719:Pyrazines / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D051996:Transcription Factor RelA; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; D001897:Boronic Acids; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D020672:I-kappa B Proteins; D016328:NF-kappa B; D009687:Nuclear Proteins; D011480:Protease Inhibitors; D011518:Proto-Oncogene Proteins; D011719:Pyrazines; D051996:Transcription Factor RelA; D016159:Tumor Suppressor Protein p53; D013481:Superoxides; D000069286:Bortezomib; C497206:MDM2 protein, human; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse; D004318:Doxycycline