Reactivation of PP2A activity by FTY720 suppressed cell growth, enhanced apoptosis, impaired clonogenicity, and decreased in vivo leukemogenesis of imatinib- and dasatinib-sensitive and -resistant Ph+ B-ALL cells, as well as Ph+ B-ALL progenitors (CD34+/CD19+). The gene discussed is CD34; the disease is acute lymphoblastic leukemia.