遺伝子治療ＤＤＳとしてのＤＮＡ／ｌｉｐｏｓｏｍｅ

Abstract

Liposomes, artificial generated lipid vesicles, that can entrap drugs within their aqueous compartment and/or in their lipid bilayer have been regarded as a useful drug delivery system ; their potentials for in vivo gene transfection has been reported. In 1987, Feigner and his colleagues demonstrated that a cationic liposomes provide a highly efficient and convenient means to deliver nucleic acids and proteins into various cell types, and that they have a lot of advantages in in vivo gene transfection. Our research of cationic liposomes was initiated in 1988 and we found by collaboration of Yagi and his colleagues that cationic liposomes consisting of N-(α-trimethylammonioacety1)-didodecyl-D-glutamate chloride (TMAG), dilauroyl phosphatidylcholine (DLPC), and dioleoyl phosphatidylethanolamine (DOPE) (1 : 2 : 2 or 1 : 2 : 3, molar ratio) provide high efficiency of DNA entrapping and high potentiality to DNA transfer to human glioma cells. Our cationic liposomes were at first prepared by an improved procedure of reverse-phase evaporation method. However, the improved procedure had some problems for clinical application. Namely, it was complicate and reverse-phase evaporation vesicles were not easy to sterilize and prepare in large quantities. To elucidate these problems, we developed further simple method and characterized the liposomes. Another advantage of cationic liposomes is targeting of the liposomes to specific cells by conjugating the Iiposomes with monoclonal antibodies or ligands. On the monoclonal antibody conjugating Iiposomes, many successful experimental achievements have been reported in the medical application of liposomes. Here, we described simpler method for the association of a monoclonal antibody to target the gene to specific tissues. Further, we also reported the characterization of the liposomes associating a monoclonal antibody (immunoliposomes). We found the immunoliposomes to transfer the entrapped genes more effectively than control liposomes. A β-galactosidase activity was about 2 to 3-fold higher when Lac Z gene was transfected to human glioma cells, and the production of human interferon-β (HuIFN β) was 2 to 7-fold higher when HuIFN β gene was done, than that of control liposomes. Liposomes appear to be more safe than viral vectors because liposomes are non-infectious and appear non-immunogenic. We thought that non viral gene transfer like liposomes would be needed in near future. Furthermore, the immunoliposomes conjugating a glioma-associated monoclonal antibody may become effective carriers for gene transfer to human glioma cells and various cells.