EFFECTIVE GENE-VIROTHERAPY FOR COMPLETE ERADICATION OF TUMOR FOR PRECLINICAL STUDIES

Abstract

Proliferation-dependent transcriptional activation that is endogenously triggered could provide a means of improving the efficiency of cancer gene therapy. In this study, we demonstrate that transgene expression could be targeted to proliferating human hepatocellular carcinoma (HCC). This is achieved by placing the transgene under the cell cycle-dependent transcriptional regulation, facilitated by liver-specific promoter in the context of herpes simplex virus type 1 (HSV-1) amplicon vector. As a proof-of principle, the yeast cytosine deaminase (yCD) suicide gene has been chosen as the therapeutic gene. Host tumor growth is monitored non-invasively by tracking the red fluorescent protein-expressing human hepatocellular carcinoma cells (HCC). Expression of yCD is indirectly monitored through the luciferase reporter gene. In the presence of 5-fluorocytosine (5-FC; prodrug), the newly generated vector (AH-6CC-L2C) could induce strong bystander cell killing efficiency in proliferating HCC but to a lesser extent in non-proliferating HCC in vitro. Most importantly, transgene expression mediated by AH-6CC-L2C is significantly enhanced in patient-derived HCC compared to the corresponding matched normal adjacent liver cells, and that efficient suppression of HCC tumor growth is also observed in subcutaneous and orthotopic primary HCC patient-derived xenograft mouse models. These vectors elicit minimal cytotoxicity and are therefore considered as potential vectors for HCC treatment.