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In this study, we developed an anionic lipoplex by coating cationic lipoplex with anionic polymers such as hyaluronan (HA), chondroitin sulfate C (CS) and poly-l-glutamic acid (PLE) to deliver the plasmid DNA efficiently into the tumor by avoiding interaction with erythrocytes. The sizes of HA-, CS- and PLE-coated lipoplexes were ∼200 nm and the ζ-potentials were negative. CS- and PLE-coated lipoplexes did not induce agglutination after mixing with erythrocytes, but cationic and HA-coated lipoplexes exhibited agglutination. In terms of biodistribution and gene expression after intravenous administration, cationic and HA-coated lipoplexes largely accumulated and induced gene expression in the lung. In contrast, CS- and PLE-coated lipoplexes did not exhibit high gene expression in the lung and mainly accumulated in the liver. However, in tumor, differences in lipoplex accumulation and gene expression were not observed among the lipoplexes. In terms of toxicity after intravenous injection, CS- and PLE-coated lipoplexes did not increase tumor necrosis factor-α, aspartate aminotransferase and alanine aminotransferase concentrations in blood. From these findings, CS and PLE coatings for cationic lipoplex might produce safe systemic vectors, although they did not increase gene expression in tumor.

Pheochromocytomas are highly angiogenic neuroendocrine tumors. The side effects of treatment with cytotoxic agents frequently outweigh the benefits. Neuroendocrine tumors are highly angiogenic, dependent on vascular endothelial growth factor and receptor (VEGFR) activation. Sunitinib has antitumor and antiangiogenic activities that target VEGFRs. We investigated the antitumor activity of liposomal sunitinib and irinotecan alone and in combination. Liposomal sunitinib and irinotecan, and liposomes co-loaded with both drugs were prepared, and antitumor activity and biodistribution were examined in nude mice bearing PC12 tumors. Liposomal sunitinib increased in life span (ILS, 14.3%) compared with free sunitinib (-17.1% ILS) with moderate tumor growth suppression, whereas liposomal irinotecan suppressed tumor growth significantly without a survival benefit compared with free irinotecan (-21.7 and -13.3% ILSs, respectively). The combination of liposomal sunitinib plus liposomal irinotecan, and liposomes co-loaded with both drugs, induced significant inhibition of tumor growth and increased life-span more than the combination of free drugs. Accumulation of irinotecan in tumors by the combination of the two liposomal drugs and liposomes co-loaded with both drugs was significantly increased compared with the combination of free drugs. This study provides novel formulations of sunitinib and irinotecan in combination for the treatment of pheochromocytoma.

To investigate the use of folate-targeted nanoemulsion-loaded aclacinomycin A (ACM) to folate receptor (FR)-positive cells, we attempted to optimize the targeting ability of nanoemulsions by modifying the chain length and amount of the folate-PEG linker. Folate-linked, nanoemulsion-loaded ACM were formulated with 0.24 mol% of folate-poly (ethylene glycol)(3400)- (folate-PEG(3400)-) and folate-PEG(5000)-distearoylphosphatidylethanolamine (DSPE), and 0.03 mol% of folate-PEG(5000)-DSPE in nanoemulsions. Selective FR-mediated uptake was achieved in a human nasopharyngeal tumor cell line, KB, which overexpresses FR, but not in a human hepatoblastoma cell line, (FR(-)) HepG2. At the same amount of folate modification, the association with KB cells was increased with increasing the PEG-chain length. The association of 0.03 and 0.24 mol% folate-PEG(5000)-linked nanoemulsions with cells was 5- and 3.3-fold higher than that of non-folate nanoemulsion, respectively, while their cytotoxicity was similar. Both 0.03 and 0.24 mol% folate-PEG(5000)-linked nanoemulsions and non-folate nanoemulsion following intravenous injection inhibited tumor growth more significantly than ACM solution on day 24 following tumor inoculation (p < 0.01). This study demonstrates that a folate-linked nanoemulsion is feasible for tumor-targeted ACM delivery, and that folate modification with a sufficiently long PEG-chain and a small amount of nanoemulsion is an effective way of targeting nanoemulsion to tumor cells.

A water-insoluble anti-cancer agent, camptothecin (CPT) was incorporated to a polymeric micelle carrier system forming from poly(ethylene glycol)-poly(aspartate) block copolymers. Incorporation efficiency and stability were analyzed in correlation with chemical structures of the inner core-forming hydrophobic blocks as well as with incorporation methods. Among three incorporation methods (dialysis, emulsion and evaporation methods), an evaporation method brought about much higher CPT yields with less aggregation than the other two methods. By the evaporation method, CPT was incorporated to polymeric micelles in considerably high yields and with high stability using block copolymers possessing high contents of benzyl and methylnaphtyl ester groups as hydrophobic moieties. This indicates importance of molecular design of the hydrophobic block chain to obtain targeting using polymeric micelle carriers as well as importance of the drug incorporation method.

We investigated multilamellar vesicle (MLV) liposomes composed of dipalmitoylphosphatidylcholine (DPPC) and a soybean-derived sterylglucoside mixture (SG) (DPPC/SG-liposomes) for targeting liver parenchymal cells after administration via the tail vein in mice, using liposome-entrapping calcein. The accumulation of DPPC/SG(7:2, mole ratio, DPPC:SG = 7:2)-liposomes in the liver was the highest among DPPC/SG-liposomes. About 80% and 40% of the dose of DPPC/SG(7:2)-liposomes accumulated in the liver at 15 min and 2 h, respectively, but about 20% of DPPC/SG(7:3.5, 7:7)-liposomes accumulated at 2 h after an intravenous administration. However, the uptake of DPPC/SG(7:2, 7:3.5, 7:7)-liposomes by liver parenchymal cells was about 7 times greater than that in non-parenchymal cells irrespective of the SG concentration in liposomes. The uptake of DPPC/SG(7:2)-liposomes in liver was almost the same level as that by liposomes containing lactocylceramide (LC) (LC-liposomes) that were already known to be taken up in liver parenchymal cells by the asialoglycoprotein receptor. DPPC/SG(7:2)-liposomes effectively targeted liver, having optimal stability and SG.