Abrogation of TAp73 expression inhibits PD plus ATO-induced apoptosis in leukemia cells. (A) NB4 and K562 cells seeded at 1 × 105 cells/mL were pretreated for 3 hours with MEK1 inhibitors PD98059 (40 μM or 10 μM) or PD184352 (1 μM) or with the PI3K inhibitor wortmannin (0.2 μM and 1 μM) and then incubated for 72 hours with the indicated concentrations of ATO. Viable cells were counted by the trypan blue dye exclusion method and apoptosis was measured as the percentage of cells with hypodiploid DNA content. Each value represents the mean ± SD of 4 independent experiments. (Bi) NB4 cells were transfected with an expression vector encoding for an HA-tagged version of TAp73 alone or in the presence of siRNAp73 or siRNAGFP. Cells were lysed 24 hours after transfection and TAp73 expression was assessed by anti-HA immunoblot. (Bii) NB4 (left) and K562 (right) cells were transfected with the indicated siRNAs and subsequently treated with PD184352 (1 μM), ATO (1 μM for NB4 and 2 μM for K562), or PD plus ATO for 72 hours prior to apoptosis analysis. Values are the mean ± SD of 3 independent experiments. AS = ATO.
