Cyclic RGD Conjugated Poly(ethylene Glycol)-co-poly(lactic Acid) Micelle Enhances Paclitaxel Anti-glioblastoma Effect

The use of glioblastoma-targeted drug delivery system facilitates efficient delivery of chemotherapeutic agents to malignant gliomas in the central nervous system while minimizing high systemic doses associated with debilitating toxicities. To employ the high binding affinity of a cyclic RGD peptide (c(RGDyK), cyclic Arginine-Glycine-Aspartic acid-D-Tyrosine-Lysine) with integrin alpha(v)beta(3) over-expressed on tumor neovasculature and U87MG glioblastoma cells, we prepared paclitaxel-loaded c(RGDyK)-Poly(ethylene glycol)-block-poly(lactic acid) micelle (c(RGDyK)-PEG-PLA-PTX). In vitro physicochemical characterization of these novel micelles showed satisfactory encapsulated efficiency, loading capacity and size distribution. In vitro cytotoxicity studies proved that the presence of c(RGDyK) enhanced the anti-glioblastoma cell cytotoxic efficacy by 2.5 folds. The binding affinity of c(RGDyK)-PEG-PLA micelle with U87MG cells was also investigated. The competitive binding IC(50) value of c(RGDyK)-PEG-PLA micelle was 26.30 nM, even lower than that of c(RGDyK) (56.23 nM). In U87MG glioblastoma-bearing nude mice model, biodistribution of (125)I-radiolabeled c(RGDyK)-PEG-PLA or DiR encapsulated micelles and anti-glioblastoma pharmacological effect was investigated after intravenous administration. c(RGDyK)-PEG-PLA micelle accumulated in the subcutaneous and intracranial tumor tissue, and when loaded with PTX (c(RGDyK)-PEG-PLA-PTX), exhibited the strongest tumor growth inhibition among the studied paclitaxel formulations. The anti-glioblastoma effect of c(RGDyK)-PEG-PLA-PTX micelle was also reflected in the median survival time of mice bearing intracranial U87MG tumor xenografts where the median survival time of c(RGDyK)-PEG-PLA-PTX micelle-treated mice (48 days) was significantly longer than that of mice treated with PEG-PLA-PTX micelle (41.5 days), Taxol (38.5 days) or saline (34 days). Therefore, our results suggested that c(RGDyK)-PEG-PLA micelle may be a potential drug delivery system in the treatment of integrin alpha(v)beta(3) over-expressed glioblastoma.