Blood cancers come in both acute and chronic forms, and are generally composed of either lymphoid or myeloid cells. Acute lymphoblastic leukemia (ALL) is typically regarded as a childhood disease and although most children are cured with standard chemotherapy, 10-20% suffer relapse and eventually succumb to their disease. ALL also affects adults and despite the fact that the leukemia cells themselves appear essentially identical to those in pediatric ALL, the majority of adults succumb to their disease. Recent studies of normal blood cells have revealed there are significant differences in how these cells are programmed in children and adults, and it is possible these differences underlie the disparity in clinical outcome in pediatric vs. adult ALL. We propose to identify what the differences are between leukemic blood cells in children and adults, and to determine whether these differences can be exploited to design new therapies to improve clinical outcomes for adults and the subset of children who suffer relapse.