Figure 2.

Dose-effect curves for VBL against the cell growth of human leukemic cells in the absence and presence of MDR reversing agents where ○, varying [VBL] alone; •, varying [VBL] with constant [NAA] (15 μM); ▪, varying [VBL] with constant [NADMA] (15 μM). (Upper) CCRF-CEM lymphoblastic leukemic cells. (Lower) CCRF-CEM/VBL₁₀₀ leukemic cells 760-fold resistant to VBL. The concentrations of the ardeemins used were about one-half of their IC₅₀ values toward CCRF-CEM cells (see Table 1).