Figure 1.

Phenethyl isothiocyanate (PEITC) significantly induces apoptosis, caspase activation, and poly(ADP-ribose) polymerase (PARP) cleavage in U937 human leukemia cells in dose- and time-dependent manners. (a) U937 cells were treated without or with various concentrations of PEITC as indicated for 3 and 6 h. (b) U937cell were treated without or with 8 μM PEITC for 1, 3, 6, 9, 12, and 24 h. Cells were stained with Annexin V/propidium iodide (PI), and apoptosis was determined using flow cytometry as described in Materials and Methods. (c) U937 cells were treated without or with various concentrations of PEITC as indicated for 3 and 6 h. (d) U937 cells were treated without or with 8 μM PEITC for 0.5, 1, 2, 3, 4, 6, 12, and 24 h. After treatment of U937 cells with the indicated PEITC concentration or the indicated time interval, total cellular extracts were prepared and subjected to western blot assay using antibodies against PARP, cleaved-caspase-3 (C-Caspase-3), caspase-8, and cleaved-caspase-9 (C-Caspase-9). Each lane was loaded with 30 μg protein. Blots were subsequently stripped and reprobed with antibody against β-actin to ensure equivalent loading and transfer. Two additional studies yielded equivalent results