NOTCH1 and leukemia: An important role of Notch signaling in the progression and aggressiveness of solid tumors has been demonstrated;37, 38, 39, 40 in addition, there is increasing evidence supporting the same important role also in leukemia.41 In particular, it has been shown that Notch1 activation in T-ALL cells contributes to central nervous system infiltration42 and more recently that Notch1 influences both hypoxia-induced invasion property43 and extra-medullary infiltration of T-ALLs.44