FN1 and cancer: The collagen-binding integrin subunits β1 and α3 (which also bind fibronectin, laminin, and thrombospondin), together with the α5- (binds fibronectin), β3- (binds fibronectin, von-willebrand factor, and thrombospondin) and β4- (binds laminin) integrin receptors have been shown to be upregulated or functionally activated by their respective ligands within the lung niche to promote the proliferation and metastatic potential of cancer cells (42, 54–59).