Notably, epigenomic and transcriptomic profiles of human cell lines MV4;11, SEM, and RS4;11 differed from those of the gene-edited leukemias and primary patient samples (Supplemental Figure 3, A–C), again suggesting that human KMT2A-AFF1 cell lines are poor surrogates for primary leukemia biology. This evidence concerns the gene AFF1 and leukemia.