CDK1 and FLT3 mutations. An alternative pathway for activation of CDK1 is constitutive activation of FLT3-initiated signaling by FLT3-ITD; this signaling can activate both ERK1/2 and CDK1 and these kinases then phosphorylate the transcription factor C/EBPα; this phosphorylation will inhibit its transcriptional activity and thereby contribute to the differentiation block in these AML cells [127,128,129]. The gene discussed is MAPK3; the disease is acute myeloid leukemia.