MAP2K4 and acute myeloid leukemia: In other cell lineages, atRA can also interact with other MAPKs; atRA-mediated ERK2 activation promoted cell differentiation in HL-60 acute myelogenous leukemia cells [56], and blocked JNK kinase-dependent signaling pathways [57] by activating MAP kinase phosphatase-1 and inhibiting MKK4 [58].