NOTCH1 and acute lymphoblastic leukemia: While NOTCH1 mutations allowed for ligand-independent activation, they remained sensitive to GSI-mediated inhibition and prompted preclinical studies of Notch blockade as a targeted therapy in T-ALL (Weng et al., 2006; Cullion et al., 2009; Real et al., 2009; Tatarek et al., 2011; Samon et al., 2012; Sanchez-Martin et al., 2017).