Interference with nuclear factor kappa B and c-Jun NH2-terminal kinase signaling by TRAF6C small interfering RNA inhibits myeloma cell proliferation and enhances apoptosis.
The tumor necrosis factor receptor (TNFR)-associated factor (TRAF) family of six adaptor proteins (TRAF1-6) links the TNFR superfamily to the nuclear factor kappa B (NF-kappaB) and activator protein-1 (AP-1) transcriptional activators. Unlike other TRAFs, TRAF6 is also involved in Toll-like/interleukin (IL)-1 receptor (TIR) signal transduction. Thus, inhibition of TRAF6 function could interrupt both CD40 (TNFR family) and IL-1 growth signals, pathways critical to myeloma proliferation. To block TRAF6-mediated IL-1 signaling, we constructed small interfering RNA (siRNA) against TRAF6. We found that siRNA targeting the TRAF6 C-terminal (siTRAF6C) receptor interaction domain specifically reduced only TRAF6 protein expression, without affecting TRAF2 or 5 levels, and substantially interfered with IL-1-induced NF-kappaB and c-Jun/AP-1 activation. Inhibition by siTRAF6C was concentration-dependent. SiTRAF6C also significantly reduced myeloma proliferation and enhanced apoptosis in a similar dose-dependent fashion in vitro. More importantly, marked siTRAF6C growth inhibition was detected in vivo when these cells were implanted into the bone marrow of irradiated normal mice. In contrast, introduction of siRNA derived from the TRAF6 Zn-finger domain or an irrelevant siRNA construct failed to alter cell growth or cell death. These studies suggest that TRAF6 may be a new molecular target to block cell signal transduction important for the survival and proliferation of multiple myeloma cells.
Chen
H
H
Institute for Myeloma and Bone Cancer Research, West Hollywood, CA 90069, USA.
Li
M
M
Campbell
R A
RA
Burkhardt
K
K
Zhu
D
D
Li
S G
SG
Lee
H J
HJ
Wang
C
C
Zeng
Z
Z
Gordon
M S
MS
Bonavida
B
B
Berenson
J R
JR
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001853:Bone Marrow / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009101:Multiple Myeloma / Q000378:metabolism* / Q000473:pathology; D016328:NF-kappa B / Q000378:metabolism*; D034622:RNA Interference / Q000502:physiology; D034741:RNA, Small Interfering / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics* / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014162:Transfection; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
D007375:Interleukin-1; D016328:NF-kappa B; D034741:RNA, Small Interfering; D048029:TNF Receptor-Associated Factor 6; D018808:Transcription Factor AP-1; D048031:JNK Mitogen-Activated Protein Kinases