The importance of CDK6 for leukemia with MLL-rearrangements gained attention when Placke et al. identified CDK6 as selectively implicated in the growth of MLL-AF9, MLL-AF4, and MLL-AF6 rearranged cells compared to wild type controls by using a functional genetic RNA interference screening approach (Placke et al., 2014). This evidence concerns the gene AFF1 and leukemia.