728. Anti-TAG-72 Immunoliposomes for Efficient Tumor-Targeted Gene Therapy

Abstract

One of the most promising strategies for cancer gene therapy is achievement of tumor-specific expression of tumor-killing genes without any related cytotoxicity. A tumor-recognizing vehicle with monoclonal antibodies or their fragments specific to tumor surface antigens, so call immunoliposomes (ILs), is a modality for tumor-targeted delivery. However, currently there are very limited data on this type of gene delivery vehicle. Hence, we have developed novel immunoliposomes specific to tumor cells overexpressing tumor-associated glycoprotein 72 (TAG-72) for drug or gene delivery. The anti-TAG-72 ILs were prepared by conjugation of Fab' fragments of recombinant humanized monoclonal antibody HzCC49 to sterically stabilized unilamellar liposomes (90-110 nm in diameter) to create targetability to TAG-72-overexpressing cancer cells. The liposomes consisted of POPC (1-palmitonyl-2-oleoyl-sn-glycerol-3-phosphocholine, 92 mol %), DMKD cationic lipid (O, O'-dymyrisyl-N-lysyl aspartate, 4 mol %), DSPE-PEG2000 (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol) 2000], 3 mol %), and DSPE-PEG2000-MAL (DSPE-[maleimide(polyethylene glycol) 2000], 1 mol %). The anti-TAG-72 ILs were able to adhere to the surface of TAG-72-overexpressing LS174T human colon cancer cells more effectively than conventional liposomes. Also, in vitro gene transfection to the LS174T cells by the anti-TAG-72 ILs in the presence of a high concentration of fetal bovine serum (up to 60%) were greater than that by the conventional cationic lipoplexes. The intravenously administered anti-TAG-72 ILs were efficiently localized in the LS174T tumor tissues while the non-targetable conventional liposomes were not. Intravenous administration of the anti-TAG-72 ILs containing plasmids encoding anti-angiogenic proteins, such as angiostatin K1/3, endostatin, and saxatilin, significantly inhibited in vivo growth of the LS174T tumors and angiogenesis in the tumor tissues. These results demonstrated that the TAG-72-mediated targeting of immunoliposomes would be a possible modality for systemic gene delivery to human colon cancer cells.