Induction of p53-related proteins by F-ara-A and Nutlin-3a in a CLL sample with wild-type p53. The sample contained more than 95% CD5⁺CD19⁺ cells with normal Atm levels. Cells were treated with 5 μM F-ara-A (F) and 5 μM Nutlin-3a (3a) either as individual agents or in combination, for the indicated times. F-ara-A induced p53 phosphorylation on Ser¹⁵ , followed by p53 accumulation and Puma induction. Nutlin-3a induced immediate accumulation of p53 that is mostly free of phosphorylation on Ser¹⁵ , followed by Mdm2 and Puma induction. The degree of Puma induction was further enhanced in cells treated with F-ara-A and Nutlin-3a. β-Actin is used to confirm equal loading of proteins. Lysate from cells before treatment served as control (C).