Blocking α3 and α5 integrin or Rho associated protein kinase (ROCK) in CAFs decreased their ability to produce ECM tracks to facilitate cancer cell migration.85 Accordingly, in patient‐ and PyMT‐derived mammary CAFs, ROCK was required for the expression of cytoskeletal regulators and stiffening of the ECM via nuclear localization of the transcriptional coactivator YAP (YAP1). Here, YAP1 is linked to cancer.