NOTCH1 and acute lymphoblastic leukemia: Although new chemotherapeutic protocols have improved the prognosis of T-ALL, the outcome of patients with resistant or relapsed leukemia remains poor,1, 11 highlighting the need for more effective antileukemic drugs.9 The identification of somatic activating Notch1 mutations in the majority of T-ALLs has stimulated interest in targeting the Notch1-signaling pathway.