Quantitative measurements of the efficacy of new anti-cancer agents on fresh human AML cells by using multivariate...

The testing of new human leukemia-specific drugs for activity against primary acute myeloid leukemia (AML) blasts is severely limited by the low and variable clonogenic potential of primary human leukemias in culture. To circumvent this problem, we have modified a previously described flow cytometric approach to permit the simultaneous determination of live/dead cells, and the quantitation of the surviving cell fraction as a ratio of viable cells in treatment and control groups. The method utilizes the combination of calceinAM as a probe for intracellular esterase activity (green fluorescence,) which has the advantage over carboxyFDA of pH insensitivity and superior signal-to-noise ratio, and propidium iodide (red fluorescence) as an indicator of plasma membrane integrity. Suspension cultures of AML blood and marrow samples from patients were treated with known active agents as well as several new agents arising from a clonogenic disk assay screen. Quantitative dose-response values obtained from surviving cell fractions assayed by flow cytometry at 24 h following drug exposure demonstrated the utility of this assay for quantitating drug-induced cytotoxic effects on primary human AML cells in short-term culture.