DOT1L and leukemia: To determine the impact of mutated DOT1L in regulating proliferation, WT and M55L, P271L, and P505L DOT1L expression constructions were introduced into MV411 leukemia cells or HPMs and cell growth after treatment with the DOT1L inhibitor EPZ-5676 was analyzed using cell counting (Fig. 2c) and an MTT assay (Fig. 2d).