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Utilizing three biocompatible components, a series of novel cationic lipids has been chemically synthesized and tested for their gene-transferring capabilities in 293 transformed kidney cells and B16BL6 mouse melanoma cells. The synthesized cationic lipids consisting of a core of lysine and aspartic acid with hydrocarbon chains of varied length were assigned the acronyms DLKD (O,O'-dilauryl N-lysylaspartate), DMKD (O,O'-dimyristyl N-lysylaspartate), DPKD (O,O'-dipalmityl N-lysylaspartate), and DSKD (O,O'-distearyl N-lysylaspartate). The gene-transferring capabilities of these cationic lipids were found to be dependent on the hydrocarbon chain length. Under similar experimental conditions, the order of gene transfection efficiency was DMKD > DLKD > DPKD > DSKD. Addition of cholesterol or dioleoyl phosphatidylethanolamine (DOPE) as a colipid did not change this order. Colipid addition affected the transfection efficiency positively or negatively depending on the length of the cationic lipid acyl chain. On the whole, the length of the hydrophobic carbon chain was a major factor governing the gene-transferring capabilities of this series of cationic lipids. The observed differences in transfection efficiency may be due to differing binding affinities to DNA molecules as well as differences in the surface charge potential of the liposome-DNA complexes (lipoplexes) in the aqueous environment.

Transfection of the antiangiogenic angiostatin and endostatin genes was shown to be an alternative to high-dose administration of angiostatin or endostatin proteins for cancer therapy. We have systematically investigated whether coadministration of the mouse angiostatin kringle 1-3 gene (pFLAG-AngioK1/3) and the endostatin gene (pFLAG-Endo) complexed with cationic liposomes exhibits enhanced therapeutic efficacy. In vitro, the coexpressed mixture of angiostatin K1-3 and endostatin more effectively reduced angiogenesis in chorioallantoic membranes than either angiostatin K1-3 or endostatin alone. In vivo, subcutaneous coadministration of pFLAG-AngioK1/3 and pFLAG-Endo lipoplexes more effectively inhibited vascularization in Matrigel plugs implanted in mice than either one alone. Additionally, subcutaneous administration of these genes inhibited the growth and formation of pulmonary metastases of B16BL6 melanoma cells in mice. Compared to treatment with an empty vector, treatment with pFLAG-AngioK1/3 plus pFLAG-Endo inhibited 81% of tumor growth, while treatment with pFLAG-AngioK1/3 or pFLAG-Endo inhibited tumor growth 70 and 69%, respectively. Cotreatment with the two plasmids after primary tumor excision induced a 90% inhibition of pulmonary metastases versus 79% for pFLAG-AngioK1/3 or 80% for pFLAG-Endo individually. These results suggest that combined administration of angiostatin K1-3 and endostatin genes complexed with cationic liposomes may be an innovated antiangiogenic strategy for cancer therapy.

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Fusogenic liposomes ( virosomes ) consisting of Sendai virus envelope proteins have been utilized for in vitro and in vivo genetic modification of animal cells. In this study, the virosomes containing DNA were prepared by quantitative reconstitution of Sendai envelope proteins, fusion protein and hemagglutinin -neuramindase in liposomal vesicles. The Sendai virosomes more efficiently transferred genes into cultured 293 transformed kidney cells than 1,2 -dioleoyl -3 -( trimethylammonium ) propane -based cationic liposomes. At 200:1 weight ratio of envelope protein and lipid, the virosomes exhibited the best efficiency of gene transfection into the cells. The Sendai virosomes required relatively a short period of incubation time and much less cytotoxic, compared to the cationic liposome / DNA complex. The transfection efficiency of the Sendai virosomes containing DNA was maintained 70% after a month. This type of Sendai virosomes is relatively convenient for preparation and storage, compared to fusogenic liposomes prepared by liposome -virus fusion. First of all, because the constituents are quantitatively formulated, this type of virosome formulation can provide further consistent transfection for gene therapy.