CASP3 and leukemia: A time course analysis showed that obvious cFLIP suppression occurred 5 minutes to 4 h after the initiation of NSC-743380 treatment of U937 and THP-1 cells, before caspase 8 and caspase 3 cleavage, suggesting that cFLIP suppression with the associated caspase 8 activation is a mechanism by which NSC-743380 exerts anti-leukemia activity (Figure 3).