Disclosed are methods for inhibiting proliferation of or inducing apoptosis in certain leukemia cells or both. The methods comprise contacting a leukemia cell exhibiting an NPM1 mutation with a pharmacologic inhibitor of interaction between MLL and menin. More broadly, disclosed are methods for treating a susceptible leukemia using pharmacologic inhibition of Menin-MLL interaction. Also disclosed are methods for treating such leukemias using inhibition of Menin-MLL interaction in combination with DOT1L inhibition.