RECEPTOR LIGAND-FACILITATED GENE-TRANSFER - ENHANCEMENT OF LIPOSOME-MEDIATED GENE-TRANSFER AND EXPRESSION BY TRANSFERRIN

A high-efficiency, nonviral gene transfer protocol employing cationic liposome plus a receptor ligand is described. The delivery of the beta -galactosidase (beta-Gal) gene (pCMVlacZ) by lipofectin plus transferr in can achieve 98-100% transfection of HeLa cells as compared to 3-4% by lipofectin alone. A dose-dependent gene transfer was observed betwe en 1 and 16 mu g transferrin, and maximal transfection efficiency was obtained at greater than or equal to 16 mu g transferrin. The expressi on of beta-Gal activity in 100% transfected cells decreased progressiv ely with each passage and returned to the baseline value after six pas sages, indicating that the DNA delivered was only transiently expresse d. The amount of DNA delivered to the cells by lipofectin plus transfe rrin was approximately two times that obtained by lipofectin, which in turn was two times that by transferrin or without lipofectin and tran sferrin. In addition, DNA can form complexes with lipofectin and trans ferrin. These results suggest that transferrin enhances gene transfer and expression in the presence of lipofectin by further facilitating t he 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 liposome s. The four different liposomes examined show the following relative t ransfection efficiency: transfectin > lipofectACE >> DC-cholesterol >> lipofectAMINE.