TY - JOUR
T1 - Downregulation of c-FLIP promotes caspase-dependent JNK activation and reactive oxygen species accumulation in tumor cells
AU - Nakajima, A.
AU - Kojima, Y.
AU - Nakayama, M.
AU - Yagita, H.
AU - Okumura, K.
AU - Nakano, H.
N1 - Funding Information:
We thank Y Gotoh, H Nishina, M Takekawa and T Ueno for providing reagents and helpful discussion. This work was supported in part by Grants-in-Aid for 21st Century COE Research and Scientific Research (B) from Japan Society for the Promotion of Science, Japan, a Grant from Human Frontier Science Program (HFSP), and grants from the Takeda Science Foundation, the Tokyo Biochemical Research Foundation, and NOVARTIS Foundation (Japan) for the Promotion of Science.
PY - 2008/1/3
Y1 - 2008/1/3
N2 - Nuclear factor-kappa B (NF-κB) inhibits cell death through suppression of the caspase cascade, the c-Jun N-terminal kinase (JNK) pathway, and reactive oxygen species (ROS) accumulation. To suppress this antiapoptotic function of NF-κB might be a promising strategy to increase susceptibility of tumor cells to stress-induced cell death. We have recently shown that tumor necrosis factor (TNF)α induces caspase-dependent and -independent JNK activation and ROS accumulation in cellular FLICE-inhibitory protein (c-Flip)-/- murine embryonic fibroblasts (MEFs). To apply this observation to tumor therapy, we knocked down c-FLIP by RNA interference in various tumor cells. Consistent with the results using c-Flip-/- MEFs, we found that TNFα stimulation induced caspase-dependent prolonged JNK activation and ROS accumulation, followed by apoptotic and necrotic cell death in various tumor cells. Furthermore, TNFα and Fas induced the cleavage of mitogen-activated protein kinase/ERK kinase kinase (MEKK)1, resulting in generation of a constitutive active form of MEKK1 leading to JNK activation in c-FLIP knockdown cells. Given that ROS accumulation and necrotic cell death enhance inflammation followed by compensatory proliferation of tumor cells, selective suppression of caspase-dependent ROS accumulation will be an alternative strategy to protect cells from ROS-dependent DNA damage and compensatory tumor progression.
AB - Nuclear factor-kappa B (NF-κB) inhibits cell death through suppression of the caspase cascade, the c-Jun N-terminal kinase (JNK) pathway, and reactive oxygen species (ROS) accumulation. To suppress this antiapoptotic function of NF-κB might be a promising strategy to increase susceptibility of tumor cells to stress-induced cell death. We have recently shown that tumor necrosis factor (TNF)α induces caspase-dependent and -independent JNK activation and ROS accumulation in cellular FLICE-inhibitory protein (c-Flip)-/- murine embryonic fibroblasts (MEFs). To apply this observation to tumor therapy, we knocked down c-FLIP by RNA interference in various tumor cells. Consistent with the results using c-Flip-/- MEFs, we found that TNFα stimulation induced caspase-dependent prolonged JNK activation and ROS accumulation, followed by apoptotic and necrotic cell death in various tumor cells. Furthermore, TNFα and Fas induced the cleavage of mitogen-activated protein kinase/ERK kinase kinase (MEKK)1, resulting in generation of a constitutive active form of MEKK1 leading to JNK activation in c-FLIP knockdown cells. Given that ROS accumulation and necrotic cell death enhance inflammation followed by compensatory proliferation of tumor cells, selective suppression of caspase-dependent ROS accumulation will be an alternative strategy to protect cells from ROS-dependent DNA damage and compensatory tumor progression.
KW - Apoptosis
KW - Necrosis
KW - Reactive oxygen species
KW - Tumor necrosis factor
KW - c-FLIP
KW - c-Jun N-terminal kinase
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U2 - 10.1038/sj.onc.1210624
DO - 10.1038/sj.onc.1210624
M3 - Article
C2 - 17599041
AN - SCOPUS:37849036487
VL - 27
SP - 76
EP - 84
JO - Oncogene
JF - Oncogene
SN - 0950-9232
IS - 1
ER -