Flow cytometric chemosensitivity analysis of blasts from patients with acute myeloblastic leukemia and myelodysplastic syndromes: The use of 7AAD with antibodies to CD45 or CD34

Background: Flow cytometry is potentially suited to the chemosensitivity an alysis of peripheral blood or bone marrow subpopulations in patients with l eukaemia and myelodysplastic syndromes. Methods: The use of the fluorescent dye 7-aminoactinomycin (7AAD) on unfixe d cells to measure loss of viability at a range of cytosine arabinoside (ar a-C) doses was evaluated. A six-tube flow cytometric assay for measuring th e sensitivity to ara-C of CD45/side-scateter-gated or of CD34-positive leuk emic blasts with 7AAD was established, using fixed stained normal mononucle ar cells as an internal standard for quantitation of viable cells following culture. Results: 7AAD dose response curves for 10 patients with acute myeloblastic leukemia (AML) showed a wide range of sensitivities at 2.5-5 mu M araC (3.7 -97%, mean 54% of control cell viability at 2.5 mu M and 4.1-94.6%, mean 27 % at 5 mu M). Parallel assays for ATP bioluminescence agreed reasonably wel l with the 7AAD method, r(s) = 0.78. The chemosensitivity of CD45/SSC-gated blast cells at 2.5 mu M araC showed no consistent relationship with the un gated cell populations, such. that CD45/SSC-gated blast sensitivity than th at of the total population. Similarly, the chemosensitivities of the CD34-g ated subpopulations ranged from 51% more to 78% less than those of the tota l populations. Conclusions: These results emphasize the necessity of measuring the chemose nsitivity of the population of interest rather than of the sample as a whol e in heterogeneous clinical material. Cytometry 37:308 -313, 1999. (C) 1999 Wiley-Liss. Inc.