In vitro effects of imatinib on CD34(+) cells of patients with chronic myeloid leukemia in the megakaryocytic crisis phase

Imatinib is a tailored drug for the treatment of chronic myeloid leukemia (CML), and has substantial activity and a favorable safety profile when used as a single agent in patients with CML in myeloid blast crisis. The megakaryocytic blast crisis in CML occurs rarely and carries a poor prognosis. The aim of the present study was to investigate the effects of imatinib on cluster of differentiation (CD)34(+) cells from patients with CML in the megakaryocytic crisis phase. Bone marrow mononuclear cells (BMNCs) were isolated from patients with CML in the megakaryocytic crisis phase. CD34(+) cells were selected from BMNCs by positive immunomagnetic column separation. Imatinib significantly induced G(1) arrest, reduced the phosphorylation of cyclin-dependent kinase 1 and retinoblastoma proteins and inhibited the proliferation of CD34(+) cells from patients with CML in the megakaryocytic crisis phase. Annexin V/propidium iodide and caspase-3 activity showed that imatinib induced apoptosis. Western blot analysis and protein tyrosine kinase activity assays showed that imatinib inhibited BCR-ABL protein tyrosine kinase activity. The in vitro data thus markedly indicate a potential clinical application of imatinib for patients with CML in the megakaryocytic crisis phase.