Although activation of Notch signaling and its downstream target c-Myc can trigger apoptosis through the ARF-MDM2-p53 tumor suppressor pathway, apoptosis is frequently inactivated in T-ALL through homozygous deletions of the CDKN2A locus encoding ARF in 80% of patients [9]. This evidence concerns the gene CDKN2A and acute lymphoblastic leukemia.