Cure rates of childhood acute lymphoblastic leukemia (ALL) have improved dramatically in the past decades. However, in 15-20% of children with ALL, the leukemia comes back after therapy and most children who relapse eventually succumb to the disease. Relapsed ALL is in fact one of the leading cause of death in children with cancer. Most importantly, ALL relapse is significantly more frequent in Hispanic children compared to Caucasians, and the underlying causes are largely unknown.