Immunoblot analysis of depsipeptide-treated HUT78 cells. (A) HUT78 cells were treated for 24 to 48 hours with 0, 1, 2, or 4 ng/mL depsipeptide, as indicated. Whole cell lysates were prepared and 7 μg/mL proteins were separated by PAGE. Immunoblots were performed as described in “Materials and methods” using antibodies against acetylated histone H3, demonstrating the direct effect of depsipeptide on the cells; p21, indicating that depsipeptide is able to induce gene expression, as previously described; and PARP, to demonstrate the apoptotic effect of depsipeptide. GAPDH confirms equivalent loading of proteins. (B) HUT78 cells were pretreated with caspase inhibitor z-VAD-fmk (100 μM) or equal amount of DMSO as control for 1 hour prior to the addition of 2 ng/mL depsipeptide. Cells were exposed to both agents together for an additional 48 hours. Cells cycle arrest and annexin V analysis was performed as described in “Materials and methods.”