In support of a cooperative role for PEAK1 and SNAI2 within the same fibroblastic stromal cells in HER2-positive breast cancers, the poor prognostic utility of PEAK1 in HER2-positive breast cancer was notably restricted to patient tumors expressing high levels of SNAI2 (Fig. 1p–s and Supplementary Fig. 3). This evidence concerns the gene ERBB2 and breast cancer.