Receptor Ligand-Facilitated Gene Transfer: Enhancement of Liposome-Mediated Gene Transfer and Expression by Transferrin

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Abstract
A high-efficiency, nonviral gene transfer protocol employing cationic liposome plus a receptor ligand is described. The delivery of the β-galactosidase (β-Gal) gene (pCMVlacZ) by lipofectin plus transferrin can achieve 98–100% transfection of HeLa cells as compared to 3–4% by lipofectin alone. A dose-dependent gene transfer was observed between 1 and 16 μg transferrin, and maximal transfection efficiency was obtained at ≥16 μg transferrin. The expression of β-Gal activity in 100% transfected cells decreased progressively with each passage and returned to the baseline value after six passages, indicating that the DNA delivered was only transiently expressed. The amount of DNA delivered to the cells by lipofectin plus transferrin was approximately two times that obtained by lipofectin, which in turn was two times that by transferrin or without lipofectin and transferrin. In addition, DNA can form complexes with lipofectin and transferrin. These results suggest that transferrin enhances gene transfer and expression in the presence of lipofectin by further facilitating the entry of DNA into the cells through the lipofectin–DNA–transferrin complex. The enhancement of liposome-mediated gene transfer efficiency and expression by transferrin varies with different cationic liposomes. The four different liposomes examined show the following relative transfection efficiency: transfectin > lipofectACE >> DC-cholesterol >> lipofectAMINE. Transfection of HeLa cells employing lipofectin plus a receptor ligand, such as transferrin, yields high gene transfer and expression efficiency. The simplicity of the formulation and high transfection efficiency by these reagents could facilitate the development of suitable transfection reagents for human gene therapy.