Abstract 598: Grape seed extract targets bladder cancer cells via initiating both apoptotic and autophagic machineries

Abstract

Abstract Bladder cancer is the fifth most common malignancy in the US; statistical reports for 2011 estimate ∼69,250 new bladder cancer cases and 14,990 associated deaths in the US alone. Of all types of cancers, bladder cancer has an unusually high propensity for recurring after treatment, making it the most expensive cancer to treat on a per patient basis. Thus, discovery and development of agents, especially natural, non-toxic, dietary- agents, which target growth and development of bladder cancer cells, might provide opportunities to reduce the incidence of bladder cancer pre-neoplastic lesions and/or prevent the progression to carcinoma. In this regard, several pre-clinical studies conducted by us and others have established strong anti-cancer efficacy of one such phytochemical agent: grape seed extract (GSE) in various malignancies including prostate, colon, skin, lung etc. Based on these previous reports, in the present study, we sought to establish the efficacy of GSE in bladder cancer and to delineate the mechanistic effects involved in its protective effect. The cell culture studies revealed that indeed GSE has the potential to target bladder cancer as indicated by a significant (P<0.05-0.001) dose and time dependant inhibitory effect (20-60% cell death, 24-48 h) of GSE (25-100 µg/ml) on the viability of two different urinary bladder cancer cell lines viz., HT-B9 and T-24, representing stage I and stage II bladder cancer, respectively. The observed cell death was apoptotic in nature as determined by AnnexinV/PI staining, which was also confirmed by increase in the expression levels of cleaved caspase-3 and -9. Further, we also observed that exposure of urinary bladder cancer cells to GSE causes a dose and time dependant increase in intense cytoplasmic vacuolization, which under electron microscopy was confirmed to be due to an enlargement of mitochondrial organelle as well as due to the presence of autophagosomes. Through detailed in vitro studies; we also examined and defined that GSE targets expression of various molecules regulating apoptosis, as indicated by decreased levels of anti-apoptotic molecules Bcl-2 and Mcl-1. Interestingly, the increase in apoptotic response co-related with increased autophagic events as evidenced by tracking the dynamics of LC3-II within the cells. Together, these results indicate that autophagy might be the major event initiated during GSE treatment of bladder cancer cells, driving the cells towards an apoptotic death pathway; however, more mechanistic studies are warranted in future to confirm our hypothesis. Nevertheless, the findings of the present study are highly significant in establishing, for the first time, that GSE could suppress bladder cancer growth and progression, by targeting both apoptotic and autophagic machineries. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 598. doi:1538-7445.AM2012-598