Liver-specific expression of an exogenous gene controlled by human apolipoprotein A-I promoter.

Liver-specific gene therapy is advantageous to minimize the possible adverse effects caused by non-target gene expression. The CMV promoter of the enhanced green fluorescent protein (EGFP) expressing plasmid pCMV-EGFP was replaced with the liver-specific promoter apolipoprotein A-I (ApoAI) generating pApoAI-EGFP plasmid. In vitro expression experiments performed in various cell lines including HepG2, SMMC-7721, MCF7, ACC-2 and Lo2 indicated that pCMV-EGFP treatment caused gene expression in all the cell lines, whereas pApoAI-EGFP treatment only induced EGFP expression in cells of liver origin including the liver cancer cells HepG2 and SMMC-7721 and the normal liver cells Lo2. Either pCMV-EGFP or pApoAI-EGFP was formulated as pegylated immuno-lipopolyplexes (PILP), a novel and efficient gene delivery system. Following intravenous administration of the PILP in H22 tumor-bearing mice, there was significant EGFP expression in liver, tumor, spleen, brain and lung in the pCMV-EGFP treated mice, whereas in the pApoAI-EGFP treated mice there was only gene expression in liver and tumor and the non-liver organ gene expression was eliminated. This study suggests that the use of the PILP technology and liver-specific promoter enables efficient and liver-specific expression of an exogenous gene.