NEMO and RIP1 Control Cell Fate in
Response to Extensive DNA Damage
via TNF-a Feedforward Signaling
Sharon Biton1and Avi Ashkenazi1,*
1Department of Molecular Oncology, Genentech, 1 DNA Way, South San Francisco, CA 94080 USA
Upon DNA damage, ataxia telangiectasia mutated
(ATM) kinase triggers multiple events to promote
cell survival and facilitate repair. If damage is exces-
sive, ATM stimulates cytokine secretion to alert
neighboring cells and apoptosis to eliminate the
afflicted cell. ATM augments cell survival by acti-
vating nuclear factor (NF)-kB; however, how ATM
induces cytokine production and apoptosis remains
elusive. Here we uncover a p53-independent mech-
anism that transmits ATM-driven cytokine and
caspase signals upon strong genotoxic damage.
Extensive DNA lesions stimulated two sequential
NF-kB activation phases,
NEMO/IKK-g: The first phase induced TNF-a-
TNFR1 feedforward signaling, promoting the second
kinase triggered JNK3/MAPK10-dependent inter-
leukin-8 secretion and FADD-mediated proapoptotic
caspase-8 activation. Thus, in the context of exces-
sive DNA damage, ATM employs NEMO and RIP1
kinase through autocrine TNF-a signaling to switch
on cytokine production and caspase activation.
These results shed light on cell-fate regulation by
Metazoan cells are capable of maintaining genomic integrity
despite frequent exposure to exogenous or endogenous
genotoxic insults. This capacity is mediated by a specialized
DNA-damage response (DDR), which is essential for tissue
homeostasis and avoidance of malignancy. The DDR involves
a network of sensing and signaling components that detect
DNA lesions and orchestrate their repair (Harper and Elledge,
2007; Jackson and Bartek, 2009; Kastan and Bartek, 2004;
O’Driscoll and Jeggo, 2006; Shiloh, 2003, 2006). The DDR also
engages signaling pathways to arrest cell growth and promote
survival during repair or, alternatively, if lesions are excessive,
to alarm neighboring cells and eliminate the damaged cell by
Cancer treatment often relies on genotoxic strategies such as
ionizing radiation and certain types of chemotherapy. Many
treatments induce a specific type of DNA lesion, characterized
by double-strand breaks (DSBs). The primary transducer of the
response to DSBs is the nuclear kinase ataxia telangiectasia
mutated (ATM) (Kastan and Bartek, 2004; O’Driscoll and Jeggo,
2006; Shiloh, 2003, 2006). Upon detection of DSBs, ATM is
rapidly activated to phosphorylate multiple target proteins on
serine or threonine residues followed by glutamine (SQ/TQ
motif). ATM thereby mobilizes an array of events, facilitating
points, and activation of prosurvival and stress-response
pathways. Depending on the extent and duration of DNA
damage, ATM can also activate cytokine secretion and pro-
grammed cell death (Fumagalli and d’Adda di Fagagna, 2009;
Harper and Elledge, 2007; Kastan and Bartek, 2004; O’Driscoll
and Jeggo, 2006; Rashi-Elkeles et al., 2006; Shiloh, 2003, 2006).
pathway, which regulates genes involved in diverse biological
functions, including inhibition of apoptosis and promotion of
cell survival (Criswell et al., 2003; Huang et al., 2003; Li et al.,
2001; Piret et al., 1999). ATM-induced NF-kB signaling is impli-
cated not only in permitting normal cells to repair DNA but also
in enabling malignant cells to resist genotoxic therapy (Janssens
and Tschopp, 2006). The mechanism underlying NF-kB activa-
tion by ATM shares some features with the mode of NF-kB
stimulation by the proinflammatory ligand tumor necrosis factor
a (TNF-a). Upon binding to its type 1 cell-surface receptor
(TNFR1), TNF-a assembles a proximal signaling complex, con-
sisting of several components (Chen and Goeddel, 2002;
Hayden and Ghosh, 2008; Karin, 2006; Karin and Lin, 2002; Wil-
son et al., 2009). These include the adaptor, TNFR-associated
death domain (TRADD); the DD-containing serine/threonine
(S/T) kinase, receptor-interacting protein 1 (RIP1); and the E3
ubiquitin ligases, TNF receptor-associated factor 2 (TRAF2)
and cellular inhibitor of apoptosis protein (cIAP) 1 and 2.
TNFR1 triggers cIAP-mediated, K63-linked polyubiquitylation
of RIP1, promoting RIP1 interaction with TAK1 kinase and
TAK1-binding proteins 1 and 2. TAK1 stimulates inhibitor of kB
(IkB) kinase (IKK), which consists of the catalytic subunits IKK-a
and b and the regulatory subunit IKK-g (NEMO). A universal
requirement of RIP1 for TNF-a-induced NF-kB activation has
92 Cell 145, 92–103, April 1, 2011 ª2011 Elsevier Inc.
been challenged (Wong et al., 2010). Upon TNFR1 activation,
IKK mediates IkB phosphorylation, leading to IkB ubiquitylation
and proteasomal degradation. This allows NF-kB to enter the
nucleus and activate gene transcription.
ATM is essential for NF-kB activation in response to DNA
damage (Li et al., 2001; Piret et al., 1999; Rashi-Elkeles et al.,
2006). Initial studies suggested that DNA lesions induce
ATM-dependent NEMO phosphorylation and subsequent ubiq-
uitylation to activate the cytoplasmic IKK complex (Bartek and
Lukas, 2006; Huang et al., 2003; Janssens and Tschopp, 2006;
Wu et al., 2006). More recent evidence indicates that nuclear
exit of ATM also drives NEMO ubiquitylation, leading to TAK1
phosphorylation and IKK activation (Hinz et al., 2010; Wu et al.,
2010). In contrast to the TNF-a pathway, DDR-driven IkB degra-
dation in mouse embryo fibroblasts did not require TNFR1,
TRAF2, TRAF5, or FADD (Hur et al., 2003). NEMO also forms
a tripartite complex with RIP1 and p53-inducible DD-containing
protein (PIDD), augmenting NEMO ubiquitylation and NF-kB
activation (Janssens et al., 2005). Alternatively, PIDD binds
caspase-2 via the adaptor RIP1-associated protein with a DD,
forming a ‘‘PIDDosome’’ that induces apoptosis (Janssens and
Tschopp, 2006; Tinel and Tschopp, 2004).
NEMO associates with RIP1, which is reported to be required
for DDR-induced NF-kB activation in mouse embryo fibroblasts
but not human HEPG2 cells (Hinz et al., 2010; Hur et al., 2003).
RIP1 is implicated not only in controlling NF-kB but also in regu-
lating cell death in response to TNF-a, viral infection, or cIAP
antagonists (Bertrand et al., 2008; Cho et al., 2009; He et al.,
2009; Petersen et al., 2007; Varfolomeev et al., 2007; Wang
et al., 2008). Kinase activity of RIP1 is dispensable for NF-kB
activation (Kelliher et al., 1998; Ting et al., 1996) but required
for induction of necroptotic cell death (Cho et al., 2009; Degterev
et al., 2008; He et al., 2009; Hur et al., 2003). RIP1 ubiquitylation
favors downstream prosurvival signaling via NF-kB over cell
death induction through the adaptor Fas-associated death
domain (FADD) and the apoptosis-initiating protease caspase-8
(C8) (Declercq et al., 2009; Wang et al., 2008).
Despite the critical relevance of the DDR to physiology and
disease, little is known about how cellular life or death decisions
are made upon ATM activation. In the present work we identify
a p53-independent mechanism that selectively triggers ATM-
of extensive DNA damage. Our results provide insight into the
control of cell fate downstream of ATM.
Extensive DNA Damage Induces ATM-Dependent
Interaction of NEMO, RIP1, FADD, and Caspase-8,
Leading to Caspase Activation
Toinvestigate howATM controls cellularoutcome inresponse to
different levels of DNA damage, we treated HeLa cells with the
topoisomerase II inhibitor etoposide and analyzed interactions
between potentially relevant intracellular signaling components.
Etoposide caused significant formation of DSBs, indicated by
phosphorylation of H2AX, BRCA1, SMC-1, and the ATM
substrate KAP1 (Figures S1A and S1B available online and
Figures 1A and 1B) (Shiloh, 2006). Etoposide also induced
NF-kB activation, detectable within 2 hr by immunoblot (IB) anal-
ysis of IkB degradation; furthermore, at high doses and upon
longer incubation, etoposide stimulated phosphorylation of
stress-activated c-Jun N-terminal kinase (JNK) (Figures 1A and
1B). Consistent with previous data (Hur et al., 2003), etoposide
triggered association of NEMO with RIP1 (Figures 1C and 1E).
with apparent ubiquitylation of NEMO (Figure S1C)—a modifica-
tion known to be important for NF-kB activation in response to
DSBs (Huang et al., 2003; Hinz et al., 2010). Surprisingly, at
higher doses and on longer incubation, etoposide also stimu-
lated recruitmentof FADD
(Figures 1C and 1E) and association of RIP1 with FADD and C8
(Figures 1D and 1F). FADD binds RIP1 and C8 via respective
DD and death effector domain (DED) interactions (Wilson et al.,
2009). C8 activation involves self-processing between the p18
and p10 subunits to form a p43 fragment, whereas cleavage
between p18 and the DEDs releases C8 from FADD (Boatright
et al., 2003). The pan caspase inhibitor zVAD-fmk (zVAD)
efficiently blocks the latter but not the former event (unpublished
data). Consistent with this, zVAD augmented association of
FADD and RIP1 with NEMO and with C8 (Figures 1G and 1H);
reciprocal immunoprecipitation (IP) of FADD or RIP1 further
confirmed their interaction (Figure 1I, Figure S1D).
The recruitment of FADD and C8 appeared to be functionally
significant because IP of C8 revealed C8 processing into p43
and a marked elevation in C8 enzymatic activity, specifically in
response to high-dose etoposide (Figure 1H and Figure 2A).
zVAD did not affect H2AX and KAP1 phosphorylation or p43
generation (Figure S1B and Figure 2B), nor did it change the
cellular levels of NEMO, RIP1, FADD, or C8 (Figure S1E).
However, zVAD blocked further C8 processing and consequent
activation of caspase-3 (C3), as indicated by attenuated
cleavage of C3 and its substrate, PARP; in contrast, zVAD
slightly enhanced stimulation of NF-kB and JNK (Figure 2B).
Consistent with its lack of effect on p43 generation, zVAD did
not decrease C8 activity in FADD IPs (Figure S1F). Due to
antibody (Ab) cross-reactivity, we were unable to visualize C8
by IB in NEMO IPs. Nevertheless, C8 activity was readily detect-
able by NEMO IP, and this was blocked by siRNA silencing of
NEMO (Figure 2C); moreover, C8 activity was detected by
RIP1 IP (Figure S1G). C8 depletion by siRNA further verified
specific C8 association with FADD and RIP1 and C8 activation
(Figures S1H and S1I). Together, these results suggest that
high-dose etoposide induces a functional interaction of NEMO,
RIP1, FADD, and C8.
Ionizing radiation, neocarcinostatin, doxorubicin, or campto-
thecin also induced recruitment of FADD and C8 to RIP1, as
well as NF-kB and JNK activation (Figures S2A and S2B),
demonstrating that other DSB inducers stimulate similar events.
Moreover, high-dose etoposide triggered association between
RIP1 and C8 and C8 activation also in MDA231 and MDA435
cells (Figures S2C and S2D), extending these effects to other
cell types. p53 is an important mediator of ATM signals in
response to DSBs (Miyashita et al., 1994; Nakano and Vousden,
2001; Oda et al., 2000). Given that HeLa, MDA231 and MDA435
cells lack functional p53, we turned to RKO cells, which
express wild-type p53, to assess p53’s involvement in these
Cell 145, 92–103, April 1, 2011 ª2011 Elsevier Inc. 93
signals, which can be decoded in the context of cellular param-
eters such as the extent of DNA damage to dictate whether the
cell should live or die.
In conclusion, we have identified a NEMO- and RIP1-based
signaling that mediates ATM-induced cytokine secretion and
caspase activation selectively in the context of severe DNA
damage. These results provide important insight into the molec-
ular events that control cell fate downstream of ATM.
HeLa-M cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM),
and MDA231, MDA435, RKO cells were cultured in RPMI 1640. Culture media
were supplemented with 10% fetal bovine serum (FBS), 2 mM L-glutamine.
Reagents, siRNA, and cDNA Transfection
Please see Extended Experimental Procedures.
Immunoprecipitation and Immunoblot Analysis
Cellsweregrownon15cmplates, treatedasindicated, washedtwotimeswith
PBS, and harvested with 2 ml of the following lysis buffer: 20 mM Tris HCL
(pH 7.5), 150 mM NaCl, 10% glycerol, 1% Triton X-100, 2 mM EDTA, with
complete, EDTA-free protease Inhibitor (Roche) and phosphatae inhibitors
Cells were left on ice for 20 min and centrifuged at 14,000 rpm for 15 min.
Three milligrams of protein lysate was used for immunoprecipitation using
2 mg of the following antibodies: FADD (sc-5559), Caspase-8 (sc-6136),
NEMO (FL-419) for overnight at 4?C. The following day, 25 ml of protein A/G
ultralink resin (Thermo Scientific) was added for 2 hr at 4?C, and the IPs
were washed four times with lysis buffer, sample buffer was added, and beads
were boiled for 5 min at 95?C. Samples were then analyzed by SDS-PAGE
followed by IB. For further information on analysis of C8 activity and of RIP1
polyubiquitylation and phosphorylation, please see Extended Experimental
Supplemental Information includes Extended Experimental Procedures, six
figures, and one table and can be found with this article online at doi:10.
We thank Scot Marsters for help with constructs, Vishva Dixit and Kim Newton
for the RIP1 kinase domain deletion mutant and ubiquitin chain-specific anti-
bodies, John Moffat for help with KINOMEscan coordination, Domagoj Vucic
for BV6, members of Genentech’s FACS and DNA synthesis labs for technical
help, and members of the Ashkenazi lab for helpful discussions.
Received: July 2, 2010
Revised: January 21, 2011
Accepted: February 4, 2011
Published: March 31, 2011
Acosta, J.C., O’Loghlen, A., Banito, A., Guijarro, M.V., Augert, A., Raguz, S.,
Fumagalli, M., Da Costa, M., Brown, C., Popov, N., et al. (2008). Chemokine
Ashkenazi, A., and Dixit, V.M. (1998). Death receptors: signaling and modula-
tion. Science 281, 1305–1308.
Bartek, J., and Lukas, J. (2006). Cell biology: The stress of finding NEMO.
Science 311, 1110–1111.
Hopes and pitfalls. Nat. Rev. Drug Discov. 8, 33–40.
Bertrand, M.J., Milutinovic, S., Dickson, K.M., Ho, W.C., Boudreault, A.,
Durkin, J., Gillard, J.W., Jaquith, J.B., Morris, S.J., and Barker, P.A. (2008).
cIAP1 and cIAP2 facilitate cancer cell survival by functioning as E3 ligases
that promote RIP1 ubiquitination. Mol. Cell 30, 689–700.
Boatright, K.M., Renatus, M., Scott, F.L., Sperandio, S., Shin, H., Pedersen,
I.M., Ricci, J.E.,Edris, W.A., Sutherlin, D.P., Green,D.R.,et al. (2003). A unified
model for apical caspase activation. Mol. Cell 11, 529–541.
Chen, G., and Goeddel, D.V. (2002). TNF-R1 signaling: a beautiful pathway.
Science 296, 1634–1635.
Cho, Y.S., Challa, S., Moquin, D., Genga, R., Ray, T.D., Guildford, M., and
Chan, F.K. (2009). Phosphorylation-driven assembly of the RIP1-RIP3
complex regulates programmed necrosis and virus-induced inflammation.
Cell 137, 1112–1123.
Criswell, T., Leskov, K., Miyamoto, S., Luo, G., and Boothman, D.A. (2003).
Transcription factors activated in mammalian cells after clinically relevant
doses of ionizing radiation. Oncogene 22, 5813–5827.
Declercq, W., Vanden Berghe, T., and Vandenabeele, P. (2009). RIP kinases at
the crossroads of cell death and survival. Cell 138, 229–232.
Degterev, A., Hitomi, J., Germscheid, M., Ch’en, I.L., Korkina, O., Teng, X.,
Abbott, D., Cuny, G.D., Yuan, C., Wagner, G., et al. (2008). Identification of
RIP1 kinase as a specific cellular target of necrostatins. Nat. Chem. Biol. 4,
Engels, I.H., Stepczynska, A., Stroh, C., Lauber, K., Berg, C., Schwenzer, R.,
Wajant, H., Janicke, R.U., Porter, A.G., Belka, C., et al. (2000). Caspase-8/
FLICE functions as an executioner caspase in anticancer drug-induced
apoptosis. Oncogene 19, 4563–4573.
Fumagalli, M., and d’Adda di Fagagna, F. (2009). SASPense and DDRama in
cancer and ageing. Nat. Cell Biol. 11, 921–923.
Hande, K.R., Wedlund, P.J., Noone, R.M., Wilkinson, G.R., Greco, F.A., and
Wolff, S.N. (1984). Pharmacokinetics of high-dose etoposide (VP-16-213)
administered to cancer patients. Cancer Res. 44, 379–382.
Harper, J.W., and Elledge, S.J. (2007). The DNA damage response: Ten years
after. Mol. Cell 28, 739–745.
Hayden, M.S., and Ghosh, S. (2008). Shared principles in NF-kappaB
signaling. Cell 132, 344–362.
He, S., Wang, L., Miao, L., Wang, T., Du, F., Zhao, L., and Wang, X. (2009).
Receptor interacting protein kinase-3 determines cellular necrotic response
to TNF-alpha. Cell 137, 1100–1111.
Hickson, I., Zhao, Y., Richardson, C.J., Green, S.J., Martin, N.M., Orr, A.I.,
Reaper, P.M., Jackson, S.P., Curtin, N.J., and Smith, G.C. (2004). Identifica-
tion and characterization of a novel and specific inhibitor of the ataxia-telangi-
ectasia mutated kinase ATM. Cancer Res. 64, 9152–9159.
Hinz, M., Stilmann, M., Arslan, S.C., Khanna, K.K., Dittmar, G., and Scheider-
eit, C. (2010). A cytoplasmic ATM-TRAF6-cIAP1 module links nuclear DNA
damage signaling to ubiquitin-mediated NF-kappaB activation. Mol. Cell 40,
Huang, T.T., Wuerzberger-Davis, S.M., Wu, Z.H., and Miyamoto, S. (2003).
Sequential modification of NEMO/IKKgamma by SUMO-1 and ubiquitin medi-
ates NF-kappaB activation by genotoxic stress. Cell 115, 565–576.
Hur, G.M., Lewis, J., Yang, Q., Lin, Y., Nakano, H., Nedospasov, S., and Liu,
Z.G. (2003). The death domain kinase RIP has an essential role in DNA
damage-induced NF-kappa B activation. Genes Dev. 17, 873–882.
Jackson, S.P., and Bartek, J. (2009). The DNA-damage response in human
biology and disease. Nature 461, 1071–1078.
Janssens, S., and Tschopp, J. (2006). Signals from within: the DNA-damage-
induced NF-kappaB response. Cell Death Differ. 13, 773–784.
Janssens, S., Tinel, A., Lippens, S., and Tschopp, J. (2005). PIDD mediates
NF-kappaB activation in response to DNA damage. Cell 123, 1079–1092.
Jones, D.T., Ganeshaguru, K., Virchis, A.E., Folarin, N.I., Lowdell, M.W.,
Mehta, A.B., Prentice, H.G., Hoffbrand, A.V., and Wickremasinghe, R.G.
102 Cell 145, 92–103, April 1, 2011 ª2011 Elsevier Inc.
(2001). Caspase 8 activation independent of Fas (CD95/APO-1) signaling may
mediate killing of B-chronic lymphocytic leukemia cells by cytotoxic drugs or
gamma radiation. Blood 98, 2800–2807.
Karin, M. (2006). Nuclear factor-kappaB in cancer development and progres-
sion. Nature 441, 431–436.
Karin, M., and Lin, A. (2002). NF-kappaB at the crossroads of life and death.
Nat. Immunol. 3, 221–227.
Kasibhatla, S., Brunner, T., Genestier, L., Echeverri, F., Mahboubi, A., and
Green, D.R. (1998). DNA damaging agents induce expression of Fas ligand
and subsequent apoptosis in T lymphocytes via the activation of NF-kappa
B and AP-1. Mol. Cell 1, 543–551.
Kelliher, M.A., Grimm, S., Ishida, Y., Kuo, F., Stanger, B.Z., and Leder, P.
(1998). The death domain kinase RIP mediates the TNF-induced NF-kappaB
signal. Immunity 8, 297–303.
Li, N., Banin, S., Ouyang, H., Li, G.C., Courtois, G., Shiloh, Y., Karin, M., and
Rotman, G. (2001). ATM is required for IkappaB kinase (IKKk) activation in
response to DNA double strand breaks. J. Biol. Chem. 276, 8898–8903.
Linard, C., Marquette, C., Mathieu, J., Pennequin, A., Clarencon, D., and
Mathe, D. (2004). Acute induction of inflammatory cytokine expression after
gamma-irradiation in the rat: effect of an NF-kappaB inhibitor. Int. J. Radiat.
Oncol. Biol. Phys. 58, 427–434.
Luo, J.L., Kamata, H., and Karin, M. (2005). IKK/NF-kappaB signaling:
balancing life and death–a new approach to cancer therapy. J. Clin. Invest.
D.A., Hoffman, B., and Reed, J.C. (1994). Tumor suppressor p53 is a regulator
of bcl-2 and bax gene expression in vitro and in vivo. Oncogene 9, 1799–1805.
Nakano, K., and Vousden, K.H. (2001). PUMA, a novel proapoptotic gene, is
induced by p53. Mol. Cell 7, 683–694.
O’Driscoll, M., and Jeggo, P.A. (2006). The role of double-strand break repair -
insights from human genetics. Nat. Rev. Cancer 7, 45–54.
family and candidate mediator of p53-induced apoptosis. Science 288,
Papa, S., Bubici, C., Zazzeroni, F., Pham, C.G., Kuntzen, C., Knabb, J.R.,
Dean, K., and Franzoso, G. (2006). The NF-kappaB-mediated control of the
JNK cascade in the antagonism of programmed cell death in health and
disease. Cell Death Differ. 13, 712–729.
Peter, M.E., and Krammer, P.H. (2003). The CD95(APO-1/Fas) Dros. Inf.
Serv.C and beyond. Cell Death Differ. 10, 26–35.
Petersen, S.L., Wang, L., Yalcin-Chin, A., Li, L., Peyton, M., Minna, J., Harran,
P., and Wang, X. (2007). Autocrine TNFalpha signaling renders human cancer
cells susceptible to Smac-mimetic-induced apoptosis. Cancer Cell 12,
Piret, B., Schoonbroodt, S., and Piette, J. (1999). The ATM protein is required
for sustained activation of NF-kappaB following DNA damage. Oncogene 18,
Rashi-Elkeles, S.,Elkon,R.,Weizman, N., Linhart,C., Amariglio,N., Sternberg,
of ATM-dependent pro- and antiapoptotic signals in response to ionizing radi-
ation in murine lymphoid tissue. Oncogene 25, 1584–1592.
Rodier, F., Coppe, J.P., Patil, C.K., Hoeijmakers, W.A., Munoz, D.P., Raza,
S.R., Freund, A., Campeau, E., Davalos, A.R., and Campisi, J. (2009). Persis-
tent DNA damage signalling triggers senescence-associated inflammatory
cytokine secretion. Nat. Cell Biol. 11, 973–979.
Shiloh, Y. (2003). ATM and related protein kinases: safeguarding genome
integrity. Nat. Rev. Cancer 3, 155–168.
Shiloh, Y. (2006). The ATM-mediated DNA-damage response: taking shape.
Trends Biochem. Sci. 31, 402–410.
Sohn, D., Schulze-Osthoff, K., and Janicke, R.U. (2005). Caspase-8 can be
activated by interchain proteolysis without receptor-triggered dimerization
during drug-induced apoptosis. J. Biol. Chem. 280, 5267–5273.
Tinel, A., and Tschopp, J. (2004). The PIDDosome, a protein complex impli-
cated in activation of caspase-2 in response to genotoxic stress. Science
Ting, A.T., Pimentel-Muinos, F.X., and Seed, B. (1996). RIP mediates tumor
necrosis factor receptor 1 activation of NF-kappaB but not Fas/APO-1-initi-
ated apoptosis. EMBO J. 15, 6189–6196.
Varfolomeev, E., Maecker, H., Sharp, D., Lawrence, D., Renz, M., Vucic, D.,
by Apo2 ligand/tumor necrosis factor-related apoptosis-inducing ligand.
J. Biol. Chem. 280, 40599–40608.
Varfolomeev, E., Blankenship, J.W., Wayson, S.M., Fedorova, A.V., Kayagaki,
N., Garg, P., Zobel, K., Dynek, J.N., Elliott, L.O., Wallweber, H.J., et al. (2007).
IAP antagonists induce autoubiquitination of c-IAPs, NF-kappaB activation,
and TNFalpha-dependent apoptosis. Cell 131, 669–681.
Varfolomeev, E., Goncharov, T., Fedorova, A.V., Dynek, J.N., Zobel, K., De-
shayes, K., Fairbrother, W.J., and Vucic, D. (2008). c-IAP1 and c-IAP2 are crit-
ical mediators of tumor necrosis factor alpha (TNFalpha)-induced NF-kappaB
activation. J. Biol. Chem. 283, 24295–24299.
von Haefen, C., Wieder, T., Essmann, F., Schulze-Osthoff, K., Dorken, B., and
Daniel, P.T. (2003). Paclitaxel-induced apoptosis in BJAB cells proceeds via
a death receptor-independent,caspases-3/-8-driven mitochondrial amplifica-
tion loop. Oncogene 22, 2236–2247.
Wang, L., Du, F., and Wang, X. (2008). TNF-alpha induces two distinct
caspase-8 activation pathways. Cell 133, 693–703.
Waugh, D.J., and Wilson, C. (2008). The interleukin-8 pathway in cancer. Clin.
Cancer Res. 14, 6735–6741.
ubiquitin system. Cell Death Differ. 17, 14–24.
Wesselborg, S., Engels, I.H., Rossmann, E., Los, M., and Schulze-Osthoff, K.
(1999). Anticancer drugs induce caspase-8/FLICE activation and apoptosis in
the absence of CD95 receptor/ligand interaction. Blood 93, 3053–3063.
Wilson, N.S., Dixit, V., and Ashkenazi, A. (2009). Death receptor signal trans-
ducers: nodes of coordination in immune signaling networks. Nat. Immunol.
Wong, W.W., Gentle, I.E., Nachbur, U., Anderton, H., Vaux, D.L., and Silke, J.
(2010). RIPK1 is not essential for TNFR1-induced activation of NF-kappaB.
Cell Death Differ. 17, 482–487.
Wu, Z.H., Shi, Y., Tibbetts, R.S., and Miyamoto, S. (2006). Molecular linkage
between the kinase ATM and NF-kappaB signaling in response to genotoxic
stimuli. Science 311, 1141–1146.
Wu, Z.H., Wong, E.T., Shi, Y., Niu, J., Chen, Z., Miyamoto, S., and Tergaonkar,
V. (2010). ATM- and NEMO-dependent ELKS ubiquitination coordinates
TAK1-mediated IKK activation in response to genotoxic stress. Mol. Cell 40,
Zhou, D., Yu, T., Chen, G., Brown, S.A., Yu, Z., Mattson, M.P., and Thompson,
J.S. (2001). Effects of NF-kappaB1 (p50) targeted gene disruption on ionizing
radiation-induced NF-kappaB activation and TNFalpha, IL-1alpha, IL-1beta
and IL-6 mRNA expression in vivo. Int. J. Radiat. Biol. 77, 763–772.
Cell 145, 92–103, April 1, 2011 ª2011 Elsevier Inc. 103