FN1 and breast cancer: Furthermore, using three-dimensional (3D) cultures of a laminin-rich extracellular matrix (lrECM) ductal carcinoma in situ model, we showed that in situ breast cancer cells that survive IR treatment emerge with an invasive phenotype and exhibit upregulated α5β1-integrin expression and fibronectin and matrix metalloprotease (MMP)-9 secretion5.