MAPK1 and acute myeloid leukemia: However, neither ASK1 nor EID1 were identified in MS approaches, and western blot analysis of shNTC and shFBXO21 KD cells revealed no alterations in EID1, ASK1 activation, or ASK1’s down-stream target, p38; suggesting EID1 and ASK1 are not substrates of FBXO21 in AML (Fig. 5D).