NOTCH1 and acute lymphoblastic leukemia: CDKN2A/2B and NOTCH1 are the most frequently affected genes in T-ALL, with 60% of T-ALL patients showing activation of the NOTCH1 signaling pathway and up to 80% harboring deletions and/or mutations inactivating the CDKN2A/B genes at chromosome 9p [4, 5].