Synergistic antileukemia activity between the PI3-kinase inhibitor, LY294002, and ara-C in Meg-01 cells and primary blasts from children without DS with AMkL. (A) Meg-01 cells were harvested and lysed after incubation with a range of concentrations of the nonselective PI3-kinase inhibitor, LY294002, for 48 hours. Soluble proteins were subjected to Western blots probed with anti-Akt and anti–ph-Akt antibodies. (B) Meg-01 cells were continuously cultured in 96-well plates for 96 hours in dialyzed FBS in the presence of various concentrations of LY294002. Cell numbers were determined by the Cell Titer–blue reagents, as described in “Methods.” (C) Ara-C IC₅₀ values were determined in Meg-01 cells in the presence of different concentrations of LY294002. *Statistically significant differences (P < .05); **statistically significant differences (P < .005). (B-C) Error bars indicate SEs. (D) Standard isobologram analysis of Meg-01 cell growth inhibition by LY294002 and ara-C in combination. The IC₅₀ values of each drug are plotted; the solid line represents the additive effect, whereas the points represent the concentrations of each drug resulting in 50% growth inhibition. (E-F) Ara-C IC₅₀ values were determined in the presence of a range of concentrations of LY294002 in 2 primary AMkL blasts from 2 children newly diagnosed with de novo AMkL by MTT assay as described in “Methods.”