FN1 and neoplasm: The peptide CREKA (Cys-Arg-Glu-Lys-Ala) (Song et al., 2014), a targeting ligand for the fibrin–fibronectin complexes in the tumor extracellular matrix (ECM) (Simberg et al., 2007; Ye et al., 2008), works as an anchor to immobilize nanoparticles within the tumor interstitial to enhance retention in glioma tissue.