Simultaneous inhibition of MENIN-MLL interaction and DOT1L HMT activity synergistically induces differentiation of MLL fusion-associated leukemia cells (Dafflon et al., 2017; Okuda et al., 2017), supporting the notion that the MLL fusion complex and the DOT1L complex collaborate to induce leukemia. This evidence concerns the gene MEN1 and leukemia.