FN1 and sarcoma: Matrigel, a basement membrane matrix extracted from Engelbreth-Holm-Swarm mouse sarcoma consisting of laminin, collagen IV, entactin/nidogen, heparan sulfate proteoglycans and growth factors such as TGF-β and EGF58, has matrix stiffness (rigidity) of 50 Pa (3D, 50% Matrigel)59, which is significantly lower than that of collagen I (more than 6 kPa)60,61, fibronectin (up to 40 kPa)62, and laminin (up to 250 Pa)63.