AFF1 and leukemia: We initially conducted dose-response experiments (Figure S4D) in the three MLL-AF4+ leukemia cell lines to determine IC50 values and subsequently used BF in viability assays at 2 μM and 4 μM, which is 100- to 200-fold lower than what has been used previously in fibroblast cultures (Engelen et al., 2012).