Immunofluorescence staining of the postpartum mouse mammary gland shows membrane-bound β-catenin (white) and nuclei (blue). YAP increases β-catenin activity to facilitate the luminal to basal transdifferentiation of mammary cells and promotes basal-like cancer formation. Targeting the YAP/TEAD4/β-catenin complex offers a potential therapeutic strategy for treating basal-like breast cancers. For details, see article by Quinn and colleagues on page 2116.