Differential effects of VPA/ATRA on cell cycle and apoptosis in BCR/ABL- and FLT3-ITD–transformed cells. (A) VPA, ATRA, and VPA/ATRA (A+V)–mediated proliferation inhibition in BCR/ABL (BA)–and FLT3-ITD–transformed 32D cells. Values indicate mean ± SD at each time point of 3 different experiments. (B) Cell-cycle distribution of BA and FLT3-ITD cells after treatment with indicated compounds for 72 hours. (C) Western blot analysis of protein lysates harvested after 48 hours of treatment with indicated compounds. Actin and total histone served as loading control. (D) Measurement of apoptosis using Annexin-FITC/propidium iodide staining after cells had been treated with VPA (V), ATRA (A), VPA/ATRA (A+V), or VPA/ATRA/SH-6 (A+V+SH-6) for 96 hours. Values represent mean ± SD of 3 independent experiments. Statistical significance of differences between the percentage of apoptosis after no treatment (co) and treatment with the respective compounds were assessed by Mann-Whitney U-test as indicated (^*P < .01; ^**P < .001). (E) Western blotting of 30 μg protein lysates of 32D-BA and 32D-FLT3-ITD cells obtained after treatment with indicated compounds for 48 hours.