Interestingly, and given that Pten null murine T-ALL has generally been considered as an in vivo model for NOTCH1 independent mature T-ALL27, these data show that MN1 can still reactivate an immature T-cell marker, such as Lyl1, in the background of a mature T-ALL murine model system. Here, NOTCH1 is linked to acute lymphoblastic leukemia.