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. Author manuscript; available in PMC: 2011 Oct 1.
Published in final edited form as: Cell. 2007 Nov 16;131(4):655–658. doi: 10.1016/j.cell.2007.10.042

Figure 1. Cancer cell death induced by Smac mimetics.

Figure 1

In non-stimulated cells, cIAPs bound to TRAF2 ubiquitinate and degrade the kinase NIK thereby inhibiting the non-canonical NF-κB pathway. The addition of Smac mimetics stimulates auto-ubiquitination of cIAPs, resulting in their proteasomal degradation, which in turn leads to the stabilization of NIK. Moreover, TRAF2 “freed” from cIAPs facilitates recruitment of the kinase RIP1 to tumor necrosis factor receptor 1 (TNFR1). This results in the activation of the non-canonical and canonical NF-κB pathways, causing TNFα production in a substantial number of tumor cells. Smac mimetics also lead to sensitivity to TNFα-induced cell death, likely through the degradation of cIAPs, which are inhibitors of apoptosis, and by favoring the formation of a RIP1-dependent caspase-8 activating complex.