Resveratrol down-regulates eEF1A2 expression by blocking Akt/PI3K signaling in human ovarian cancer PA-1 cells

Abstract

3372

The eukaryotic elongation factor 1A2 (eEF1A2), a subtype of eEF1A that is a key factor in the translational process of protein synthesis, promotes the transfer of animoacylated tRNAs to the A site of the ribosome. Recently, eEF1A2 has been shown to possess a oncogenic potential as it is over-expressed in ovarian cancer. Therefore, suppression of the inappropriate expression of eEF1A2 is considered to be a rational therapeutic and preventive strategy for the management of ovarian cancer. Resveratrol (3,4’,5-trihydroxy stilbene), a phytoalexin present in grapes, has been reported to possess antioxidant, anti-inflammatory, and anti-carcinogenic activities. In the present study, we examined the anti-proliferative effect of resveratrol in PA-1 human ovarian cancer cells, considering eEF1A2 as a potential molecular target. Treatment of PA-1 cells with insulin (10 μg/ml) or serum (1%) resulted in the marked induction of eEF1A2. Resveratrol inhibited the viability, growth and soft agar colony formation of PA-1 cells. Pretreatment of PA-1 cells with resveratrol (25 or 50 μM) suppressed insulin- or serum-induced expression of eEF1A2 at 12 h. eEF1A2 exerts an anti-apoptotic effect by down-regulating the caspase-3 activity. Resveratrol was found to activate caspase-3, thereby inducing apoptosis in eEF1A2 over-expressing PA-1 cells, suggesting that the induction of apoptosis by resveratrol in these cells is mediated, at least in part, via down-regulation of eEF1A2. To clarify upstream signaling events responsible for regulation of eEF1A2, we determined the relative levels of phosphorylation of 18 representative protein kinases by antibody arrays (Proteome Profiler^TM, R&D Systems). We found that insulin induced phosphorylation of Akt1(S473)/2(S474)/pan(S473,S474,S472) which was inhibited by resveratrol as well as by LY294002 (20 μM). The pharmacologic inhibition of Akt activation with LY294002 abrogated insulin-induced eEF1A2 upregulation. Taken together, these results suggest that oncogenic eEF1A2 upregulated via the Akt/PI3K pathway is a potential target for ovarian cancer chemoprevention or treatment with resveratrol.