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The present paper demonstrates that the proteasome inhibitor bortezomib, which behaves as an apoptotic agent in hepatoma HepG2 cells, caused in these cells a decrease in IκBα level and a consequent increase in NF-κB activity. The effect already appeared at 4 h of treatment and preceded the onset of apoptosis which was observed at 24 h. Our results demonstrate that bortezomib-induced IκBα degradation occurred in conjunction with the activation of caspase-8; moreover, the decrease in IκBα level was prevented in a dose-dependent manner by the addition of z-IETD, a specific inhibitor of caspase-8. Bortezomib caused the same effects in non-tumor Chang liver cells, which were not susceptible to the apoptotic effect of the drug. Our results also show that other proteases, such as caspase-3 and calpains, exerted only a limited effect on IκBα degradation. These findings suggest that caspase-8 can be involved in the control of IκBα level. In addition, the activation of caspase-8 can exert, at least in the first phase of treatment with bortezomib, a protective effect in both HepG2 and Chang liver cells, favouring the activation of the survival factor NF-κB
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Calvaruso, G., Giuliano, M., Portanova, P. et al. Bortezomib induces in HepG2 cells IκBα degradation mediated by caspase-8. Mol Cell Biochem 287, 13–19 (2006). https://doi.org/10.1007/s11010-005-9016-3
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DOI: https://doi.org/10.1007/s11010-005-9016-3