Towards Novel Anti-tumor Strategies for Hepatic Cancer: epsilon-Viniferin in Combination with Vincristine Displays Pharmacodynamic Synergy at Lower Doses in HepG2 Cells

Abstract

Hepatocellular carcinoma is the fifth most common cancer and the third leading cause of cancer-related deaths worldwide. The efficacy of novel combination treatments are increasingly evaluated with use of integrative biology research and development (R&D) strategies and methodological triangulation. We investigated the anti-tumor effect of -viniferin alone, and the putative synergy of -viniferin with vincristine on the growth of HepG2 cells in vitro. Growth inhibition and apoptosis induction were determined by MTT assay and annexin V/propidium iodide (PI), respectively. Morphological changes and DNA fragmentation were investigated under electron microscopy and by agarose gel electrophoresis, respectively. The results collectively showed that treating cells with -viniferin and vincristine significantly inhibited cell viability at lower doses as compared to each agent applied alone. IC50 values for -viniferin and vincristine were determined as 98.3 and 52.5M at 24h, respectively. IC50 value of -viniferin in combination with vincristine was 15.8+11.25M (mean/SD) at 24h. The viability of cells treated with 17.9M vincristine alone for 24h was 79.62%; it reduced to 26.53% when 25M -viniferin was added in combination with vincristine (p<0.05). We found that combination of drugs promoted the sensitivity of cells against to vincristine treatment. The effect of combined use was in support of a synergistic pharmacodynamic effect. Moreover, low doses of the combination regimen induced phosphatidyl re-localization, morphological changes, and DNA fragmentation, and therefore caused apoptotic death. This study thus suggests that low concentrations of -viniferin and vincristine can enhance the anti-tumor effects efficiently by inducing HepG2 cell apoptosis. Further studies in other model systems are warranted with a view to potential future applications in the clinic of such combination regimens and their putative mechanism of action in the observed synergy reported here.