Gene therapy is expected to treat various incurable diseases including viral infections, autoimmune disorders, and cancers. Complexes of cationic liposomes with DNA are promising tools to deliver genetic information into cells for gene therapy and vaccines. Electrostatic interaction is thought to be the major force in lipid–DNA interaction, while lipid-base binding and the stability of cationic lipid–DNA complexes have been the subject of more debate in recent years. 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) forms heterogeneous liposomes with cationic lipids, which are used as delivery vehicles for therapeutic agents. DOPE is an essential component of cationic liposomes designed to deliver DNA into gliosarcoma and kidney cell lines (gene therapy). The order of stability of lipid–DNA complexation is DOTAP>DDAB>DOPE>Chol. Recently was discovered Lip-DOPE-MPL-GP2 formulation could be a promising vaccine and a therapeutic delivery system against HER2 positive cancers and merited further investigation.