CPX induces cell death in malignant cell lines. Leukemia (A), myeloma (B), solid tumor (C), and nonmalignant lung fibroblast (D) cell lines were treated with increasing concentrations of CPX. Seventy-two hours after incubation, cell viability was measured by MTS assay. Data represent the mean percentage of viable cells ± SD from 1 of at least 3 representative experiments. (E) Primary AML cell samples (n = 12) were treated with increasing concentrations of CPX. Seventy-two hours after incubation, cell viability was measured by the Alamar Blue assay. Data represent the mean percentage of viable cells ± SD where each sample was tested in triplicate. (F) Normal mononuclear cells derived from bone marrow (n = 3) or peripheral blood stem cells (n = 2) were plated in a methylcellulose colony-forming assay with increasing concentrations of CPX. Myeloid (granulocyte macrophage-colony forming units) and erythroid (erythroid-burst forming units) colonies were counted 14 days after plating and normalized to cultures treated with buffer alone. Data represent the mean ± SD of 5 independent experiments performed in duplicate.