Upregulation and delayed activation of caspase-3/CPP32/apopain in human ECFC after incubation with IFNγ. Day-6 cells were cultured in liquid medium or medium containing 500 U/mL of IFNγ for 24 to 96 hours and the cell proteins were analyzed by immunoblotting in three separate experiments. The top panel shows intact caspase-3 expression using MoAb that only reacts with the proenzyme. A polyclonal antibody reacting to both the intact enzyme and its fragments was used in the bottom panel. The proenzyme is significantly increased and a clear cleavage of caspase-3 occurs by 48 hours after incubation with IFNγ.