STAT5B and chronic myelogenous leukemia, BCR-ABL1 positive: Western blot analysis showed that STAT5 was dephosphorylated in the presence of imatinib (Figure 7C), confirming earlier studies [21] and suggesting, as this is the case in the K562 cell line, that phospho-STAT5 activates the transcription of miR-21 in CML CD34+ cells.