JAK2 and erythroleukemia: To further support the hypothesis that NPQ-C6 was able to inhibit constitutive pYSTAT5 in leukemia cells, we investigated the effects of NPQ-C6 on HEL, a human erythroleukemia cell line in which the JAK2/STAT5/STAT3 signaling pathway is constitutively activated due a JAK2 mutation (V617F) (Liu et al., 1999).