Induction of p73 positively regulates PUMA to induce mitochondrial dysfunction and apoptosis in primary leukemia cells. (A) Induction of PUMA transcript in cells treated with 10 nM LBH589 for 36 hours. (B) Immunoblotting was performed on the samples in panel A to determine the levels of PUMA protein. (C top panels) Induction of PUMA was accompanied by the processing of caspase-9 (CF indicates cleaved fragment) in representative samples with or without deletions in 17p. (C middle panel) The same samples were evaluated for losses in TMRM at 48 hours, reflecting decreases in mitochondrial membrane integrity. (C bottom panel) The percentage of cell death at 48 hours was evaluated by annexin V staining in the same samples. (D) Quantitation of the apoptotic response of 34 primary leukemia samples that were normal (p53⁺) or with del17p (p53⁻) 10 nM LBH589 at 48 hours.