Fig. 5 shows that exposure to 1.0 μmol/l imatinib for 48 h did not reduce the BCR-ABL protein levels, but did reduce the PTK activity in the CD34+ cells from patients with CML in the megakaryocytic and myeloid crisis phases. However, the decline in PTK activity was not notably different between the CD34+ cells from patients with CML in the megakaryocytic crisis phase and those from patients with CML in the myeloid crisis phase. Here, BCR is linked to chronic myelogenous leukemia, BCR-ABL1 positive.