YAP1 and breast cancer: Yap activation is initiated by Collagen I contact and subsequent feed-forward induction of a transcriptional program that promotes ECM remodeling leading to local alignment of Collagen I. Establishment of aligned Collagen organization through activated basal-like cancer cells leads to the emergence of protrusive leader cells that propel collective invasion, the predominant mode of dissemination in breast cancer (Fig. 7).