FLT3 and acute myeloid leukemia: To exclude the possibility that ACF effects on STAT3/5 signalling are a peculiarity of K562 cells, we tested the drug on the growth as well as on the activation and expression of STAT3/5 in two other BCR‐ABL‐positive cell lines (KU812 and KCL‐22) and in an AML cell line (MV‐4‐11) expressing FLT3‐ITD (Figure 4A).