Abstract 1012: Procyanidin B2 3,3″-di-O-gallate (B2G2), a biologically active constituent of grape seed extract, inhibits angiogenesis targeting multiple molecular pathways

Prostate cancer (PCA) is the single largest cause of non-cutaneous malignancy among men in the United States, and is the second leading cause of cancer-related deaths. According to American Cancer society estimates, in 2013, ∼238,590 new cases of PCA will be diagnosed and ∼29,720 men will die of this disease in the US alone. One of the hallmarks of prostate carcinogenesis is the extensive angiogenesis involved in both primary tumor growth and metastasis. Numerous studies to date have confirmed a direct correlation of angiogenesis with Gleason score, tumor stage, progression, metastasis and survival; and it has emerged as an important cancer prevention and therapeutic target. Therefore, targeting aberrant angiogenesis using non-toxic phytochemicals has emerged as an attractive option against PCA. B2 3,3 ″ -di-O-gallate (B2G2) is a major biological constituent of grape seed extract (GSE), a well-known dietary agent that has shown strong chemopreventive and anti-cancer efficacy against various malignancies including PCA. Recently, we reported strong efficacy of B2G2 against human PCA LNCaP, C4-2, 22Rv1, DU145 and PC-3 cells. In the present study, we investigated the anti-angiogenic efficacy of B2G2 using human umbilical vein endothelial cells (HUVEC) and human prostate microvascular endothelial cells (HPMEC). Our results showed that B2G2 (10-40 µM) inhibits proliferation and induces apoptotic cell death in both HUVEC and HPMEC in a time- and dose-dependent manner. B2G2 treatment also induced cell cycle arrest (in G1 phase) in HUVEC by upregulating CDK inhibitors (p21 (Cip1/Waf1) and p27 (Kip1) ) expression, and downregulating CDKs (Cdk2 andcdc2), cyclins (D1 and A) and Cdc25c phosphatase. B2G2 treatment also up regulated the pro-apoptotic molecules Bax and Smac/ Diablo, and down regulated the cell survival molecule survivin in HUVEC. Furthermore, B2G2 inhibited the capillary-like tube formation and invasiveness of both HUVEC and HPMEC on matrigel. Molecular analyses showed that B2G2 treatment of HUVEC decreased the phosphorylation of PI3K, PDK1, Akt, GSK3β and ERK1/2, which are known to regulate proliferation, apoptosis, tube formation and invasiveness of endothelial cells. Next, we analyzed the angiogenic potential of conditioned media (CM) collected from human PCA LNCaP and PC-3 cells treated with either DMSO or B2G2 (50 µM) under normoxic and hypoxic (1% O 2 ) conditions. CM from PCA cells grown under normoxic and hypoxic conditions significantly enhanced the capillary tube formation in HUVEC, while capillary tube formation in these endothelial cells was significantly compromised in the presence of CM from B2G2-treated PCA cells under both normoxic and hypoxic conditions. Taken together, our current findings clearly demonstrate the anti-angiogenic property of B2G2 suggesting its usefulness in PCA management. Citation Format: Rahul Kumar, Gagan Deep, Michael Wempe, Rajesh Agarwal, Chapla Agarwal. Procyanidin B2 3,3″-di-O-gallate (B2G2), a biologically active constituent of grape seed extract, inhibits angiogenesis targeting multiple molecular pathways. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1012. doi:10.1158/1538-7445.AM2014-1012