AFF1 and acute leukemia: KMT2A is the target of chromosomal translocations in adult and pediatric acute leukemia, mostly leading to fusions of the N-terminus of KMT2A with a large number of different partners, of which AF4/FMR2 family member 1 (AFF1, a.k.a. AF4), MLLT3 super elongation complex subunit (MLLT3, a.k.a. AF9), MLLT1 super elongation complex subunit (MLLT1, a.k.a. ENL), and MLLT10 histone lysine methyltransferase DOT1L cofactor (MLLT10, a.k.a. AF10) are the most prevalent (11).