Abstract 3708: Resveratrol induces DNA damage independent of Smad4 expression in its efficacy against human head and neck carcinoma cells

Abstract

Resveratrol is a non-toxic natural product present in grape skin, red wine, peanuts etc. Extensive research in almost last two-decades has established that resveratrol possesses a broad range of health benefits including anti-cancer, anti-oxidant, anti aging and cardio protective properties; however, its efficacy and associated mechanisms is not examined in head and neck squamous cell carcinomas (HNSCC), which is the sixth most common human malignancy largely associated with tobacco and alcohol use. Molecular mechanistic studies have established that frequent alterations in Smad4 signaling pathway is common in HNSCC due to frequent mutations in TGF-β type II receptor. Smad4 loss has also been shown to cause genomic instability in mice and to induce HNSCC, suggesting that the agents are needed to control HNSCC that could target both Smad4 dependent and independent pathways. Accordingly, here we evaluated the efficacy of resveratrol against a panel of human HNSCC cell lines, namely FaDu (homologous deletion of Smad4), Cal27 (harbors nonsense mutation in Smad4), and Det562 (wild type Smad4). Resveratrol treatment at 5-50µM concentrations for 24 hrs significantly suppressed cell proliferation and induced DNA damage in FaDu and Cal27 cell lines; however, Det562 cells were more resistant to such treatments even at comparatively higher dose (100 µM). Cal27 cells transfected to Smad4 (Cal27-Smad4) showed similar resveratrol effects as parent line (Cal27) indicating that a lack of resveratrol effect in Det562 cells was independent of Smad4 status in these cells. Same resveratrol treatments also did not induce DNA damage in normal human epidermal keratinocytes and fibroblasts, showing its selective efficacy only in HNSCC cells. In other studies, resveratrol also caused a strong S phase arrest and induced apoptotic death of FaDu and Cal27 cells together with induction in Brca1 and H2AX nuclear foci formation. These finding for the first time established the efficacy of resveratrol in inducing DNA damage mediated cell death, which was independent of Smad4 expression in HNSCC. Further in an in vivo study, resveratrol (50 mg/kg body weight) treatment for 30 days, inhibited the tumor volume (48%; P<.01) and tumor weight (62%; p<.01) in ectopically growing human FaDu tumor xenografts in athymic nude mice. H2AX (ser 139) and cleaved caspase 3 expression was strongly increased in tumor xenograft from resveratrol-treated mice compared to controls. Together, these results clearly establish the anti-proliferative, DNA damaging and pro-apoptotic effects of resveratrol in HNSCC cells independent of Smad4 status, both in vitro and in vivo. Based on these findings, more studies are needed in future to evaluate both anti-cancer and chemopreventive efficacy of resveratrol in relevant pre-clinical models to establish its potential usefulness against human head and neck cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3708. doi:10.1158/1538-7445.AM2011-3708