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Angiogenesis is one of crucial processes associated with tumor growth and development, and consequently a prime target for cancer therapy. Although tumor endothelial cells (TECs) play a key role in pathological angiogenesis, investigating phenotypical changes in neovessels when a gene expression in TEC is suppressed is a difficult task. Small interfering RNA (siRNA) represents a potential agent due to its ability to silence a gene of interest. We previously developed a system for in vivo siRNA delivery to cancer cells that involves a liposomal-delivery system, a MEND that contains a unique pH-sensitive cationic lipid, YSK05 (YSK-MEND). In the present study, we report on the development of a system that permits the delivery of siRNA to TECs by combining the YSK-MEND and a ligand that is specific to TECs. Cyclo(Arg-Gly-Asp-D-Phe-Lys) (cRGD) is a well-known ligand to αVβ3 integrin, which is selectively expressed at high levels in TECs. We incorporated cRGD into the YSK-MEND (RGD-MEND) to achieve an efficient gene silencing in TECs. Quantitative RT-PCR and the 5' rapid amplification of cDNA ends PCR indicated that the intravenous injection of RGD-MEND at a dose of 4.0mg/kg induced a significant RNAi-mediated gene reduction in TEC but not in endothelial cells of other organs. Finally, we evaluated the therapeutic potency of the RGD-MEND encapsulating siRNA against vascular endothelial growth factor receptor 2. A substantial delay in tumor growth was observed after three sequential RGD-MEND injections on alternate days. In conclusion, the RGD-MEND represents a new approach for the characterization of TECs and for us in anti-angiogenic therapy., (© 2013.)

Anti-angiogenic therapy is a potential chemotherapeutic strategy for the treatment of drug resistant cancers. However, a method for delivering such drugs to tumor endothelial cells remains to be a major impediment to the success of anti-angiogenesis therapy. We designed liposomes (LPs) with controlled diameter of around 300 nm, and modified them with a specific ligand and a cell penetrating peptide (CPP) (a dual-ligand LP) for targeting CD13-expressing neovasculature in a renal cell carcinoma (RCC). We modified the LPs with an NGR motif peptide on the top of poly(ethylene glycol) and tetra-arginine (R4) on the surface of the liposome membrane as a specific and CPP ligand, respectively. The large size prevented extravasation of the dual-ligand LP, which allowed it to associate with target vasculature. While a single modification with either the specific or CPP ligand showed no increase in targetability, the dual-ligand enhanced the amount of delivered liposomes after systemic administration to OS-RC-2 xenograft mice. The anti-tumor activity of a dual-ligand LP encapsulating doxorubicin was evaluated and the results were compared with Doxil, which is clinically used to target tumor cells. Even though Doxil showed no anti-tumor activity, the dual-ligand LP suppressed tumor growth because the disruption of tumor vessels was efficiently induced. The comparison showed that tumor endothelial cells (TECs) were more sensitive to doxorubicin by 2 orders than RCC tumor cells, and the disruption of tumor vessels was efficiently induced. Collectively, the dual-ligand LP is promising carrier for the treatment of drug resistant RCC via the disruption of TECs., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The objective of this study was to develop an efficient dual-ligand based PEGylated liposomal delivery system that had target specificity as well as properties that would enhance cellular uptake. PEGylated liposomes (PEG-LP) were prepared by the lipid film hydration method by adding distearoyl phosphoethanolamine-polyethylene-glycol-2000 conjugate (DSPE-PEG2000) to a lipid mixture. The cyclic RGD (Arg-Gly-Asp) peptide, a specific ligand with affinity for Integrin α(v)β(3) was coupled to the distal end of the PEG on the PEG-LP (RGD-PEG-LP). Stearylated octaarginine (STR-R8) was incorporated on the surface of the RGD-PEG-LP as dual-ligand (R8/RGD-PEG-LP) that functions as a cell penetrating peptide (CPP). RGD-PEG-LP and R8/RGD-PEG-LP were preferentially taken up by caveolae-mediated and clathrin-mediated endocytosis pathways, respectively. Compared to PEG-LP, R8/RGD-PEG-LP showed an enhanced cellular uptake as well as a higher transfection efficiency in Integrin α(v)β(3) expressing cells. However, the amount of cellular uptake or gene expression by the single ligand versions was negligible, even in Integrin α(v)β(3) expressing cells. No remarkable difference in cellular uptake or gene expression was observed for cells in which the expression of targeted receptors was absent. It can be concluded that dual-ligand modified PEG-LP possesses a strong capability for the efficient internalization of PEG-LP and consequently would be an effective tool for the targeted delivery of macromolecules or chemotherapeutics through accelerated cellular uptake., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A protein stimulating the GTPase activity of rhoB p20, a ras p21-like GTP-binding protein (G protein), was partially purified from the cytosol fraction of bovine brain. This protein, designated as rhoB p20 GTPase-activating protein (GAP), did not stimulate the GTPase activity of other ras p21/ras p21-like G proteins including c-Ha-ras p21, smg p21 and smg p25A. The activities of c-Ha-ras p21 GAP and smg p21 GAP were also detected in the cytosol fraction of bovine brain and rhoB p20 GAP was separated from these GAPs. The activity of rhoB p20 GAP was eliminated by tryptic digestion or boiling. The Mr value of rhoB p20 GAP was estimated to be 150-200 x 10(3) and 37 x 10(3) by gel filtration and sucrose density gradient ultracentrifugation, respectively. These results indicate that there is rhoB p20 GAP in addition to c-Ha-ras p21 GAP and smg p21 GAP in bovine brain. In rat brain, about 50% of rhoB p20 GAP was found with the highest specific activity in the P2 fraction containing myelin, synaptosomes and mitochondria. In the P2 fraction, about 30% of rhoB p20 GAP was found in the P2C fraction containing mainly synaptosomes. rhoB p20 GAP was detected in the cytosol and particulate fractions of not only rat brain but also other rat tissues.