FN1 and cancer: As fibronectin is a key contributor to the motility and invasiveness of many cell types including cancer cells, we allowed fibroblasts to deposit ECM in the presence and absence of extracellular uracil, de-cellularised the deposited ECM, and assessed the ability of this matrix to influence the migration of cancer cells (cells derived from PyMT+ primary mammary tumours, named PyMT+ cells).