EFFECT OF CO-LIPIDS IN ENHANCING CATIONIC LIPID-MEDIATED GENE-TRANSFER IN-VITRO AND IN-VIVO

Complexes of DNA and cationic lipids are promising vectors for gene tr ansfer. Most cationic lipid formulations contain both a cationic compo nent and a neutral co-lipid. We found that the co-lipid could influenc e DNA uptake were even more important in determining gene expression. We compared dioleoylphosphatidylethanolamine (DOPE) and structural ana logs of DOPE combined with cationic lipids and found that DNA uptake a nd transgene expression did not always correlate. Transgene expression was dependent on DNA uptake into the cell, on entry of DNA into the c ytoplasm, and on release of DNA form the lipid complex. We found that some co-lipids had a greater efect on DNA uptake, whereas others had a greater effect on steps subsequent to entry. Based on those results, we tested the hypothesis: that co-lipids conferring different properti es' could be combined to enhance gene transfer. The results Showed tha t a combination of co-lipids had a synergistic effect on expression. W e also found that structural analogs, at DOPE were more effective than DOPE in enhancing gene transfer to mature human airway epithelia stud ied in vitro and to mouse lung studied in vivo. These data provide ins ight into the mechanism by which co-lipids influence cationic lipid-me diated gene transfer and show that optimization of the effects of co-l ipids can enhance gene transfer both in vitro and in vivo.