In this regard, we demonstrate that high PEAK1 expression in HER2-positive breast cancer patient tissues predicts increased disease relapse (Fig. 1b) in HER2-positive breast cancers high in SNAI2 expression (Fig. 1s and Supplementary Fig. 3a) and mesenchymal stem cell (MSC) content (Fig. 2c). Here, SNAI2 is linked to breast carcinoma.