EIF4EBP1 and acute myeloid leukemia: In addition to upregulating the mTORC1/S6K/4EBP1/eIF4F pathway, RSK1 was demonstrated to phosphorylate not only S6RP, but also eIF4B cooperatively with PIM in FLT3-ITD-positive AML cells, which is known to enhance protein synthesis, along with eIF4F [7].