Abstract 1876: Grape seed extract targets TGFβ/Smad signaling in its potential efficacy against human head and neck cancer cells
Authors: Shrotriya Sangeeta , Agarwal Chapla , Agarwal Rajesh 
Published: February 2011

Abstract
Head and neck squamous cell carcinoma(HNSCC) is the sixth most common malignancy and the major cause of morbidity and mortality worldwide. In HNSCC, various etiological factors produce mutations or epigenetic inactivation of numerous oncogenes and/or tumor suppressor genes, suggesting that all these factors synergistically enhance the progression of normal cells to carcinoma. Transforming growth factor (TGF-beta)/activin-Smad signaling acts as a potent tumor suppressor prior to tumor initiation; however, at later stages, resistance to TGF-beta mediated growth suppression develops and an increase in cell proliferation are observed in a variety of cancers including HNSCC, making this pathway a potential target for both prevention and therapy of various malignancies including HNSCC. Several animal studies in past have shown that consumption of fruits and vegetables and/or the supplements derived from them is associated with reduced risk of cancer development including HNSCC. Grape seed extract (GSE) is one such supplement that has received enormous attention in recent years due to its strong anti-cancer and chemopreventive potential in several cancer models. Accordingly, here we investigated the potential ability of GSE in targeting TGF-beta/Smad4 signaling in two human HNSCC cells, FaDu and Detroit 562 which differ in the status of TGF-beta and Smad4. GSE treatment inhibited growth and increased death in both HNSCC cell lines in a dose- and a time-dependent manner. Specifically, GSE treatment (40 µg/ml for12-72 h) resulted in 20-80% (p&lt;0.001) and 13-60% (p&lt;0.001) decrease in total cell number, increased cell death by 8-49% and 10-53% (p&lt;0.001) in FaDu and Detroit 562 cells, respectively. To elucidate the molecular mechanism underlying cell growth inhibitory and increased cell death effects of GSE, we focused on the possible effect of GSE on TGF-beta/Smad-dependent and -independent signaling pathways in both FaDu and Detroit 562 HNSCC cells. We found that GSE treatment at 40 µg/ml conc. in DMSO decreases the expression of TGF-beta RI/ RII in both FaDu and Detroit 562 cells at 24, 48 and 72 h. GSE-treated cells also showed the reduced expression of Smad4, phosphorylation of Smad2 (at ser 465/467) without any effect on the phosphorylation of Smad3 (at ser 423/425) at 24, 48 and 72 h in Detroit 562 cells. Conversely, in FaDu cells which lack Smad4, similar GSE treatments decreased the phosphorylation of both Smad2 (at ser 465/467) and Smad3 (at ser 423/425). Taken together, our results show that GSE effectively inhibits tumor promoting function of dysfunctional TGF-beta/Smad signaling pathway by blocking the phosphorylation of Smad2/3, which in turn are surrogate marker for active TGF-beta signaling pathway. These effects of GSE seem to have a potential role in its overall anti-cancer activity against human HNSCC cells, suggesting future efficacy studies in pre-clinical animal models of HNSCC.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1876.