Effects of depsipeptide on p21 in vivo. (A) Lysates from CLL patient cells obtained before and 4 or 24 hours after depsipeptide administration were analyzed by immunoblot using an anti-p21 antibody. Simultaneous incubation with anti-GAPDH antibody was performed to detect protein-loading differences. (B) Cells from these same time points were subjected to chromatin immunoprecipitation analysis using anti-acetylated H4 antibody. The graph shows the increase in p21 promoter acetylation relative to GAPDH.