IN-VIVO ANTITUMOR EFFECT OF CATIONIC LIPOSOMES CONTAINING DIPHTHERIA-TOXIN A-CHAIN GENE ON CELLS INFECTED WITH BOVINE LEUKEMIA-VIRUS

A plasmid pLTR-DT which contained a gene for diphtheria toxin A-chain (DT-A) under the control of the long terminal repeat (LTR) of bovine l eukemia virus (BLV) (BLV-LTR) in the multicloning site of pUC-18 was e ntrapped in cationic liposomes composed of lpha-trimethylammonioacetyl )-didodecyl-D-glutamate chloride (TMAG), dioleoyl phosphatidylethanola mine (DOPE) and dilauroyl phosphatidylcholine (DLPC) (1:2:2, molar rat io) (TMAG-liposome), and their antitumor effect on BLV-infected tumor cells was examined in who. The cationic TMAG-liposome containing pLTR- DT was successively injected into the tumor transplanted to nude mice. The growth of tumor was significantly inhibited by the injection of c ationic TMAG-liposome containing pLTR-DT. On the other hand, TMAG-lipo some containing pUC18 plasmids showed no such effect. These results su ggest that a DT-A expression plasmid under the control of BLV-LTR is h ighly toxic to the BLV-infected tumor cells, and that the cationic lip osomes, such as TMAG-liposome, may be efficient transfection reagent f or BLV-infected tumor cells and can be utilized for DT-A gene delivery into BLV-infected tumor cells in vivo.