Targeted expression of green fluorescent protein/tumor necrosis factor-related apoptosis-inducing ligand fusion protein from human telomerase reverse transcriptase promoter elicits antitumor activity without toxic effects on primary human hepatocytes

Liver toxicity is the major concern for use of recombinant human tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) proteins in treatment of cancers. Here we report that normal human primary hepatocytes (NHPHs) are susceptible to the transduction of the wild-type, full-length coding sequence of the human TRAIL gene. To minimize potential toxicity of the TRAIL gene, a bicistronic adenoviral vector that expresses the green fluorescent protein/TRAIL fusion protein from the human telomerase reverse transcriptase promoter (designated Ad/gTRAIL) was constructed. In vitro and in vivo studies have showed that treatment with the adenoviral vector Ad/gTRAIL results in high-level expression of green fluorescent protein/TRAIL in cancer cells but no detectable transgene expression in NHPHs or in normal mouse liver tissues. Furthermore, treatment with Ad/gTRAIL effectively elicited apoptosis in malignant cells but not in NHPHs in vitro and suppressed tumor growth and prolonged duration of survival in vivo. Thus, with the combined advantages of the TRAIL gene and the human telomerase reverse transcriptase target, Ad/gTRAIL can be a potent therapeutic agent for the treatment of cancers.