NPM1 and leukemia: Importantly, menin’s interaction with both wild-type MLL and MLL fusion proteins is necessary to maintain oncogenic activation of Hox genes [125,126,135,136,144,146,147,148], as well as the Hox cofactors MEIS1 [129,137,138,139,140,141,149,150,151,152,153] and PBX3 [141,151,153,154], and downstream targets such as FLT3 [129,137,141,150,153,155,156] in both MLLr and NPM1 mutant leukemias.