In MLL1-rearranged leukemias (MLL-AF9), deletion of the MLL2 gene (wt) was shown capable of decreasing the leukemic cell survival, but WT-MLL1 deletion had no impact on leukemia cell function, since targeting the N-terminal part, that is shared in the MLL1-fusion protein, did ablate leukemia cells [79]; thus, indicating that the activities of the two genes are not redundant, as previously suggested [31,80]. The gene discussed is KMT2B; the disease is leukemia.