Chromosomal translocations involving the mixed lineage leukemia (MLL) gene generate potent fusion oncogenes and cause acute myeloid leukemia or lymphocytic leukemia, which account for ~75% infant and 5–10% child/adult acute leukemia cases with a poor prognosis (5-year survival rates < 45%). This evidence concerns the gene KMT2A and acute myeloid leukemia.