NOTCH4 and breast cancer: We found that re-expression of Int-β3 by human luminal breast cancer cell lines MCF-7 and T47D promotes their cancer luminal progenitor-like cells (CLPs) to revert into growth-arrested acinar-like organoids resembling normal breast tissue when cultured in a three-dimensional (3D) reconstituted basement membrane extract (BME)11 mimicking the components of the normal basement membrane.12 This reversion was mediated by downregulation of Notch4 expression and its downstream signaling.