Tumor Necrosis Factor α Stimulates Her-2 Cleavage by Activated Caspase-8.

Background/Aim: Her-2 over-expression has been correlated with a poor prognosis in patients with breast cancer. Now, we explored the effect of TNF-α treatment and/or NFκB activation on Her-2 expression in MCF-7 breast adenocarcinoma cells. Methods: Stably transfected MCF-7 cell lines with pcDNA3.0, IκBα MT, c-FLIP/control shRNA were established by FuGENE with the supplementation of G418 (500 μg /ml). Western blot and Real-time PCR were applied to assess the expression levels of protein and mRNA of target gene. In addition, caspase-8 activity was evaluated by the incubation with a caspase-8 fluorogenic substrate, Ac-IEPD-AMC using a spectrofluorometer. Results: It was uncovered that Her-2 was a new substrate for caspase-8 and that tumor necrosis factor α (TNF-α) stimulation resulted in a caspase-8-dependent Her-2 cleavage in MCF-7 breast adenocarcinoma cells defective for nuclear factor κB (NFκB) activation. We demonstrated that the antiapoptotic transcription factor NFκB counteracted this cleavage through the induction of caspase-8 inhibitor, c-FLIP. Conclusion: we propose a novel mechanism in which NFκB functions as a new antiapoptotic factor by counteracting TNF-α-triggered Her-2 cleavage. Copyright © 2012 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]