AFF1 and acute lymphoblastic leukemia: A subset of ALLs, such as KMT2A-AFF1, can also relapse after treatment to become an AML derived from the original leukemic clone (Dorantes-Acosta and Pelayo 2012; Gardner et al. 2016; Pillai et al. 2019), which is indicative of a core KMT2A-AFF1 GRN that can drive both ALL and AML.