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 NFĸB activation on Her-2 expression in MCF-7 breast adenocarcinoma cells. METHODS Stably transfected MCF-7 cell lines with pcDNA3.0, IĸBα 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 ĸB (NFĸB) activation. We demonstrated that the antiapoptotic transcription factor NFĸB counteracted this cleavage through the induction of caspase-8 inhibitor, c-FLIP. CONCLUSION we propose a novel mechanism in which NFĸB functions as a new antiapoptotic factor by counteracting TNF-α-triggered Her-2 cleavage.