Fig. 7. Expression of Bcl-xL prevents EGF-induced apoptosis. (A) The level of Bcl-xL expression decreased in A431/ErbB2 cells treated with EGF. A431/ErbB2 cells were incubated in the presence of EGF (20 ng/ml) or vehicle for the indicated times. Antibody was used to immunoprecipitate Bcl-xL from cell lysates and to detect its levels in cells by western blotting (W.B.). (B) A431/ErbB2 cells were transfected with a pIRES2-EGFP vector containing the Bcl-xL cDNA sequence. Cell sorting was used to select stable cell lines expressing Bcl-xL using GFP as a marker. Cells treated with EGF are morphologically different from control. However, they do not form dome-like clusters, as do A431/ErbB-2 cells (see Fig. 2), and continue to grow in the presence of EGF. (C) The different responses of A431/ErbB2 and A431/ErbB2/Bcl-xL cells to EGF (proliferation or cell death) are shown quantitatively.