CD34 and acute lymphoblastic leukemia: Reactivation of PP2A activity by FTY720 (fingolimod, a PP2A activator which has been approved as an immunomodulator for oral use in patients with multiple sclerosis [172]), led to leukemic cell growth suppression, 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+).