AFF1 and acute lymphoblastic leukemia: Because BIM protein levels are significantly increased in MLL-AF4 leukemias [18], we wanted to determine if lack of MLL-AF4 binding to BIM in the Wilkinson/Geng data set 17, 26 (an RS4;11 MLL-AF4 ALL cell line) was simply due to sensitivity of the ChIP-seq experiment.