The Notch signaling pathway plays a critical role in maintaining the balance 
between cell proliferation, differentiation and apoptosis, and is a highly 
conserved signaling pathway that regulates normal development in a context- and 
dose-dependent manner. Dysregulation of Notch signaling has been suggested to be 
key events in a variety of hematological malignancies. Notch1 signaling appears 
to be the central oncogenic trigger in T cell acute lymphoblastic leukemia 
(T-ALL), in which the majority of human malignancies have acquired mutations 
that lead to constitutive activation of Notch1 signaling. However, emerging 
evidence unexpectedly demonstrates that Notch signaling can function as a potent 
tumor suppressor in other forms of leukemia. This minireview will summarize 
recent advances related to the roles of activated Notch signaling in human 
lymphocytic leukemia, myeloid leukemia, stem cells and stromal microenvironment, 
and we will discuss the perspectives of Notch signaling as a potential 
therapeutic target as well.