HeLa cells stably transfected with tetracycline (Tet)-inducible Bcl-xL expression vector were incubated in DMEM containing Tet or not for 12 hours, then treated with DMSO or 10 μM MG132 for 8 hours, then washed and incubated in fresh medium for another 3 days, Cells were then subjected to SA-β-gal staining. The induced Bcl-xL was detectable even 3 days after treatment withdrawal, because this protein is stable. 