In vivo treatment of HCV core-positive HepG2 cells with the transfer of recombinant caspase-3 using a 2′-5′ OAS promoter

Abstract

Hepatitis C virus (HCV) is one of the most common pathogens causing liver-related morbidity and mortality, which affect 170 million individuals worldwide. There is no vaccine available, and current therapy is only partially effective. In a previous study, we constructed a recombinant caspase-3 expression vector under the 2′-5′-oligoadenylate synthetase gene (OAS) promoter (pGL3-OAS-re-caspase-3) and demonstrated that it is an effective gene therapy for HCV core-positive liver cells in vitro. In the present study, the human hepatoma cell line HepG2 was transfected with the pcDNA3.1-HCV-core- EGFP plasmid and selected by G418. Expression of HCV core protein was confirmed by RT-PCR and immunocytochemistry. Both HepG2-expressing HCV core protein and parental HepG2 cells were inoculated subcutaneously into BALB/c mice, respectively. Tumor-bearing mice were treated with an intratumoral injection of pGL3-OAS-re-caspase-3. The mice were sacrificed after 48 h. The correlation between HCV core and caspase-3 expression in tumor tissues was analyzed by immunohistochemical staining and double-label immunofluorescence staining. The subcutaneous hepatoma in vivo mouse models stably expressing HCV core protein and co-expressing HCV core protein and pGL3-OAS-re-caspase-3 were established. Double-label immunofluorescence staining showed that the percentage of co-expression of both HCV core and caspase-3 was 76±6% in the group treated with pGL3-OAS-re-caspase-3. There was a significant increase in the number of apoptotic cells in the group treated with the pGL3-OAS-re-caspase-3 system by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and transmission electron microscopy. The results suggest that the pGL3-OAS-re-caspase-3 construct can effectively induce apoptosis in HCV core-positive hepatocytes in vivo. The results presented strongly suggest that the transfer of pGL3-OAS-re-caspase-3 is an effective and promising gene therapy strategy for HCV infection.