p27Kip1 is a substrate of FLT3 and FLT3-ITD in AML patient samples, where they phosphorylate p27Kip1 at the residue Y88 which is required for subsequent p27Kip1 phosphorylation at T187 by the CDK2-cyclin complex marking p27Kip1 for SCFSkp2-mediated degradation. This evidence concerns the gene CDKN1B and acute myeloid leukemia.