Knockdown of EVI1 in MLL-ENL leukemic cells decreases their potential to form colonies.18 Overexpression of EVI1 is also observed in other MLL-rearranged leukemias, including those with a MLL-AF9 fusion25 and EVI1 expression serves as an independent and adverse prognostic factor within MLL-rearranged leukemias.30 Nevertheless, EVI1low leukemias also exist among the MLL-rearranged cases, possibly relating to the cell of origin of these leukemias, as discussed below. Here, MECOM is linked to leukemia.