Prostate Cancer Prevention by Procyanidins in Grape Seed Extract

描述(由申请人提供)： 前列腺癌(PCA)是老年男性最常见的恶性肿瘤，被评为男性癌症死亡的第二大原因。恶性肿瘤从癌前病变到完全癌变有很长的潜伏期，为采用化学预防策略干预或改变疾病的进展提供了充足的时间。此外，大量研究表明，饮食控制可以降低某些癌症的风险，特别是通过增加水果和蔬菜的消费。因此，人们对确定饮食或饮食成分(包括营养和非营养植物化学物质)作为化学预防药物的潜在用途一直非常感兴趣。葡萄籽提取物(GSE)是一种丰富的商业来源的原花青素(也称为原花青素)，由于其广泛的有益作用，通常被用作健康补充剂。在癌症方面，我们和其他人的几项研究已经证明了GSE对包括PCa细胞在内的各种上皮性恶性肿瘤的抗癌和化学预防效果。由于GSE代表一种复杂的多酚混合物，上一次资助期间的研究重点是分离和鉴定GSE中的活性成分(S)，以使用纯和定义的制剂对抗癌活性进行详细的机理和有效性研究。我们最近从GSE中分离并鉴定了原花青素B2-3，3‘-二O-没食子酸酯(B2-G2)，该化合物对人前列腺癌DU145细胞具有很强的抗癌活性。对该化合物的进一步研究表明，它被前列腺癌细胞摄取，并引起细胞毒性和细胞生长抑制作用。其他研究表明，B2-G2可导致携带功能性雄激素受体的人前列腺癌细胞的细胞周期停滞和凋亡诱导；这些细胞专门代表大多数人类前列腺癌。重要的是，B2-G2在正常人前列腺上皮细胞和间质细胞中没有显示出细胞毒性，在人前列腺癌细胞中显示了其选择性。由于细胞周期紊乱导致的增殖失控和凋亡功能的丧失是包括前列腺癌在内的大多数癌症的主要潜在缺陷，而且由于B2-G2对前列腺癌细胞施加了强烈的细胞周期停滞和凋亡反应，因此我们的中心假设是原花青素B2-3，3‘-二O-没食子酸酯选择性地诱导肿瘤前列腺上皮细胞的细胞周期停滞和凋亡，从而共同导致其预防和治疗前列腺癌的效果。我们的具体目标是：1)制备计划中的机制、生物利用度和疗效研究所需的B2-G2；2)进行体外研究，以探讨B2-G2参与细胞周期停滞和细胞凋亡的作用机制；3)利用转基因小鼠前列腺癌(TRAMP)体内模型，确定B2-G2的疗效和生物利用度。总体而言，我们的长期目标是开发原花青素B2-3，3‘-二O-没食子酸酯作为一种基于机制的潜在的预防前列腺癌的化学预防药物。前列腺癌是美国癌症相关死亡的第二大原因，因此是一个重要的公共卫生问题。前列腺癌的发展潜伏期长，有时从前驱病变到疾病的全面发展需要几十年的时间，因此使用化学预防药物似乎是控制前列腺癌的更有效的方法。目前的拨款提案集中在开发一种这样的制剂，这种制剂是从葡萄籽提取物中分离出来的，葡萄籽提取物是一种广泛消费的健康补充剂。我们提出的研究结果将为人类前列腺癌的预防提供一种基于机制的药物。

DESCRIPTION (provided by applicant): Prostate cancer (PCA) is the most frequently diagnosed malignancy in elderly men, and is rated as second leading cause of cancer deaths in men. The malignancy has long latent period of development from pre-neoplastic lesion to full-blown cancer providing ample time to intervene or alter the progression of this disease employing chemopreventive strategies. Additionally, numerous studies have shown that the risk for certain cancers could be lowered by dietary manipulations, especially by increased consumption of fruits and vegetables. Accordingly, there has been serious interest in identifying diets or dietary constituents (both nutritive and non-nutritive phytochemicals) for their potential use as chemopreventive agents. Grape seed extract (GSE), a rich and commercially available source of proanthocyanidins (also known as procyanidins), is usually consumed as a health supplement for its wide range of beneficial effects. Regarding cancer, several studies by us and others have demonstrated the anti-cancer and chemopreventive efficacy of GSE against various epithelial malignancies including PCA cells. Since GSE represents a complex mixture of polyphenols, the central focus of the studies during the last funding period was to isolate and characterize active component(s) in GSE to carry out detailed mechanistic and efficacy studies for anticancer activity employing pure and defined agents. We recently isolated and characterized procyanidin B2- 3,3'-di-O-gallate (B2-G2) as an active compound from GSE with strong anti-cancer activity against human prostate carcinoma DU145 cells. Further studies with this compound revealed that it is taken up by PCA cells and that it causes both cytotoxic as well as cell growth inhibitory effects. Additional studies revealed that B2-G2 causes both cell cycle arrest and apoptosis induction in human PCA cells carrying functional androgen receptor; these cells specifically represent majority of human prostate tumors. Importantly, B2-G2 did not show cytotoxicity in normal human prostate epithelial and stromal cells, showing its selectivity in human PCA cells. Since uncontrolled proliferation due to deregulated cell cycle progression and loss of apoptotic function are the major underlying defects in most of the cancers including PCA and since B2-G2 exerts strong cell cycle arrest and apoptotic responses in PCA cells, our central hypothesis is that procyanidin B2-3,3'-di-O-gallate selectively induces cell cycle arrest and apoptosis in neoplastic prostate epithelial cells which collectively leads to its preventive and therapeutic efficacy against PCA. Our specific aims are to: 1) prepare B2-G2 needed for planned mechanistic, bioavailability and efficacy studies, 2) conduct in vitro studies to address mechanism of action of B2-G2 involved in cell cycle arrest and apoptosis, and 3) determine efficacy and bioavailability of B2-G2 employing an in vivo transgenic carcinoma of the mouse prostate (TRAMP) model, which closely and naturally mimics the progression of prostatic carcinoma in humans. Overall, our long term goal is to develop procyanidin B2-3,3'-di- O-gallate as a mechanism-based potential chemopreventive agent against PCA. PUBLIC HEALTH RELEVANCE Prostate cancer is second leading cause of cancer-related deaths in United States, and thus is an important public health issue. Use of chemopreventive agents seems to be more effective approach for the control of prostate cancer as it has long latent period of development; sometimes over decades from precursor lesions to full blown disease. Current grant proposal focuses on the development of one such agent, which has been isolated from grape seed extract, a widely consumed health supplement. Outcomes of our proposed research will provide a mechanism-based agent for the prevention of prostate cancer in humans.