Specifically, Notch signaling drives luminal cell differentiation.7, 9 We previously reported that a2V inhibition in breast cancer cell lines affects notch receptor processing and results in aberrant activation of the Notch pathway.26 Our finding that a2V is expressed on the plasma membrane of luminal cells led us to investigate the expression of Notch 1 in a2V-KO mice. Here, NOTCH1 is linked to breast cancer.