While fibronectin fibers are stretched in healthy organs (12, 13), the presence of untensed fibronectin fibers in the extracellular matrix (ECM) in pathologically remodeled ECM has emerged as a hallmark of various inflammatory conditions (14, 15), as well as cancer (12, 13, 16, 17) and fibrotic diseases (18). Here, FN1 is linked to cancer.