PDGFB and neoplasm: The targets of aptamers actually in clinical trials [175] are extracellular proteins (VEGF165, C5, PDGFβ, coagulation factor IXa, A1 domain of von Willebrand factor, thrombin, TFPI, CXCL12, CCL2, hepcidin peptide hormone), except nucleolin which is highly expressed at the surface of several tumor cells.