We used primary samples of infant MLL-R ALL because these patients have a very poor outcome, and these samples readily engraft in immunodeficient mice and demonstrate enhanced survival with stromal co-culture.[9] After a two-week period of engraftment, we treated the mice with vehicle control, plerixafor, or cytarabine using two different dosing schedules. This evidence concerns the gene KMT2A and acute lymphoblastic leukemia.