Notch signaling in mammary development and oncogenesis.

With the discovery of an activated Notch oncogene as a causative agent in mouse mammary tumor virus induced breast cancer in mice, the potential role for Notch signaling in normal and pathological mammary development was revealed. Subsequently, Notch receptors have been found to regulate normal development in many organ systems. In addition, inappropriate Notch signaling has been implicated in cancer of several tissues in humans and animal model systems. Here we review important features of the Notch system, and how it may regulate development and cancer in the mammary gland. A large body of literature from studies in Drosophila and C. elegans has not only revealed molecular details of how the Notch proteins signal to control biology, but shown that Notch receptor activation helps to define how other signaling pathways are interpreted. In many ways the Notch system is used to define the context in which other pathways function to control proliferation, differentiation, cell survival, branching morphogenesis, asymmetric cell division, and angiogenesis--all processes which are critical for normal development and function of the mammary gland.