Isobolograms for the apoptotic effects of cytarabine and SU11248 of FLT3 ITD cell lines. Cells were incubated with cytarabine, SU11248, or both for 48 hours and apoptosis was assessed with a flow cytometric assay. Results were used to construct isobolograms for (A) MV4-11, (B) MOLM14, and (C) BAF3 ITD FLT3 cells with concentrations expressed in nM. Experimental results fall far to the left of the lines of equivalence, suggesting potent synergy between cytarabine and SU11248. The experimental CI values are tabulated in Table 3. • indicates ED₅₀; ▪, ED₇₅; and ▾, ED₉₀.