Synergistic cytotoxic effects and mechanism of oncolytic adenovirus SG611 combined with cisplatin on hepatocellular carcinoma HepG2 cells

Abstract

Objective To investigate the synergistic cytotoxic effects and the mechanism of oncolytic adenovirus SG611 combined with cisplatin (DDP) on hepatocellular carcinoma (HCC) HepG2 cells. Methods Human HCC HepG2 cells were infected by adenovirus vector SG611 carried with green fluorescent protein (GFP). The infection efficiency of SG611 on HepG2 cells were examined by flow cytometry. The synergistic cytotoxic effects of SG611 combined with DDP on HepG2 cells were evaluated by cell counting rit(cck)-8 assay and the cytotoxicity was assessed by crystal violet staining. The 4',6-diamidino-2-phenylindole (DAPI) staining was used to detect the apoptosis. The expression of protein E1A was examined by Western blot. The comparison of experimental data was conducted using one-way analysis of variance and LSD-t test. Results HCC HepG2 cells infected by SG611-EGFP were observed under fluorescence microscope. The GFP positive cells increased apparently with the increasing multiplicity of infection (MOI). The infection efficiency of SG611 detected by flow cytometry was 0.18%, 6.36%, 50.60%, 73.20%, 86.80% and 90.50%, which was with dose dependent. With the combined use of SG611 (MOI =10) and 1.5 μg/ml DDP, the cell viability was (33.2±1.2)%, which was significantly lower than (88.8±8.9)% of single use of SG611 (LSD-t=-7.83, P<0.05). The cytotoxic effects on HCC HepG2 cells of combined use was significantly higher than that of single use of SG611. The apoptosis rate of HCC HepG2 cells was (23.9±1.5)% for combined use, which was significantly higher than (15.3±1.0), (12.4±1.1)% for single use of SG611 or DDP (LSD-t=10.56, 21.34; P<0.05). In addition, E1A expression in HCC HepG2 cells significantly increased when combined use. Conclusions Oncolytic adenovirus SG611 combined with DDP has synergistic cytotoxic effects on HCC HepG2 cells. The action mechanism of the synergistic cytotoxic effects may be that the chemosensitivity of DDP is enhanced by SG611 and the proliferation of SG611 is enhanced by DDP. Key words: Carcinoma, hepatocellular; Oncolytic adenovirus SG611; Cisplatin; Drug synergism; Adenovirus E1A proteins