STAT1 and acute myeloid leukemia: Ser727 phosphorylation of STAT1 is necessary for maximal transcriptional activity of STAT1 and is important for AML differentiation.25, 29, 30 On the other hand, increased phosphorylation of STAT1 (Tyr701) can promote the proliferation of AML cells.34 And increased tyrosine phosphorylation of STAT1 might interfere with differentiation of AML cells.11