title: Dual-targeting of αvβ3 and galectin-1 improves the specificity of paramagnetic/fluorescent liposomes to tumor endothelium in vivo.
abstract: Molecular imaging of angiogenesis requires a highly specific and efficient contrast agent for targeting activated endothelium. We have previously demonstrated that paramagnetic and fluorescent liposomes functionalized with two angiogenesis-specific ligands, the galectin-1-specific anginex (Anx) and the α(v)β(3) integrin-specific RGD, produce synergistic targeting effect in vitro. In the current study, we applied Anx and RGD dual-conjugated liposomes (Anx/RGD-L) for angiogenesis-specific MRI in vivo, focusing on the specificity and efficacy of liposome association with tumor endothelium. The targeting properties, clearance kinetics and biodistribution of Anx/RGD-L were investigated in B16F10 melanoma-bearing mice, and compared to liposomes functionalized with either Anx (Anx-L) or RGD (RGD-L). The contrast enhancement produced by dual- and single-targeted nanoparticles in the tumor was measured using in vivo T(1)-weighted MRI, complemented by ex vivo immunohistochemical evaluation of tumor tissues. Blood clearance kinetics of Anx/RGD-L was three-fold more rapid than for RGD-L, but comparable to Anx-L. Both dual- and single-targeted liposomes produced similar changes in MRI contrast parameters in tumors with high inter-tumor variability (ΔR(1)=0.04±0.03s(-1), 24h post-contrast). Importantly, however, the specificity of Anx/RGD-L association with tumor endothelium of 53±6%, assessed by fluorescence microscopy, was significantly higher compared to 43±9% (P=0.043) and 28±8% (P=0.0001) of Anx-L and RGD-L, respectively. In contrast, long-circulating RGD-L were on average 16% more efficient in targeting tumor endothelium compared to Anx/RGD-L. Significant differences were also found in the biodistribution of investigated contrast agents. In conclusion, synergistic targeting of α(v)β(3) and galectin-1 improved the specificity of the association of the liposomal contrast agent to tumor endothelium in vivo, providing therefore a more reliable MRI readout of the angiogenic activity.
authors.affiliation: Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
authors.forename: Ewelina
authors.initials: E
authors.lastname: Kluza
authors.forename: Igor
authors.initials: I
authors.lastname: Jacobs
authors.forename: Stefanie J C G
authors.initials: SJ
authors.lastname: Hectors
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Mayo
authors.forename: Arjan W
authors.initials: AW
authors.lastname: Griffioen
authors.forename: Gustav J
authors.initials: GJ
authors.lastname: Strijkers
authors.forename: Klaas
authors.initials: K
authors.lastname: Nicolay
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003287:Contrast Media / Q000008:administration & dosage* / Q000493:pharmacokinetics; D004730:Endothelium, Vascular / Q000378:metabolism; D037483:Galectin 1 / Q000378:metabolism*; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D008081:Liposomes; D008280:Magnetics; D008546:Melanoma, Experimental / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D009842:Oligopeptides / Q000008:administration & dosage* / Q000493:pharmacokinetics; D010455:Peptides / Q000008:administration & dosage* / Q000493:pharmacokinetics
chemical_list: D003287:Contrast Media; D037483:Galectin 1; D039302:Integrin alphaVbeta3; D008081:Liposomes; D009842:Oligopeptides; D010455:Peptides; C558923:anginex peptide; C047981:arginyl-glycyl-aspartic acid