Figure 3.

Effects of gemtuzumab ozogamicin (GO) on the growth and survival of leukemic (stem) cells in patients with acute myeloid leukemia (AML). A: AML cells from a patient with FAB M4 were cultured in the presence of control medium or medium supplemented with GO (0.05–5 µg/mL) for 48 h at 37 °C. Then, CD34⁺/CD38⁻ leukemic stem cells (LSC; red bars) and CD34⁺/CD38⁺ stem and progenitor cells (blue bars) were analyzed by multi-color flow cytometry. The percentage of apoptotic cells (in LSC/progenitors) was determined by Annexin-V and DAPI staining. Flow cytometry was performed on a FACSCanto (BD Biosciences). B: AML blasts (FAB M1) were cultured in control medium or medium supplemented with GO (0.0005–0.1 µg/mL) for 48 h at 37 °C. After incubation, ³H-thymidine uptake was measured. Results are expressed as a percentage of control and represent the mean ±S.D. of triplicates. C: CD34⁺/CD38⁻ stem cells from a patient with AML M4 were purified by cell sorting. Then, cells were cultured in control medium or in medium containing various concentrations of GO (0.001–0.1 µg/mL) for 48 h at 37 °C. After incubation, ³H-thymidine uptake was measured. Results are expressed as the percent of control in one experiment. All the patients gave written informed consent before BM cells were stored and analyzed. The study was approved by the ethics committee of the Medical University of Vienna. FAB, French–American–British cooperation study group classification.