Fig. 3.

Possible model for the differential c-Rel activation by H₂O₂ and TNF-α in MCF-7- and HeLa cells. For the same extracellular H₂O₂ concentration the estimated intracellular H₂O₂ concentration for HeLa cells will be lower than that of MCF-7 cells because HeLa cells have higher GPx activity. Moreover, MCF-7 cells have a 3-fold higher concentration of c-Rel and 2-fold lower IκB-ε levels than HeLa cells. Therefore in HeLa cells most c-Rel is probably bound to IκB-ε. The differences described between MCF-7 and HeLa cells justify the specific outcome in NF-κB-dependent gene expression. Higher concentrations are shown as bigger lettering.