Characterizing Potential Redox Mechanisms of Prostate Cancer Chemoprevention by E

描述(由申请人提供)： 前列腺癌是最常见的诊断肿瘤之一，也是美国男性癌症死亡的第二大原因。生物能量学、细胞凋亡和前列腺癌的发生之间似乎有重要的联系。一些研究表明，在前列腺癌发生过程中，雄激素及其受体可能直接作用于线粒体，改变线粒体的功能。此外，明显由于前列腺上皮细胞线粒体功能异常变化而产生的活性氧物种的产生显然推动了前列腺癌的发生。前列腺肿瘤发生的惰性强烈地表明，化学预防策略在预防恶性肿瘤方面将是有效的。表没食子儿茶素没食子酸酯(EGCG)是绿茶儿茶素中的主要多酚成分，是一种很有前途的前列腺癌化学预防药物。当口服较高剂量的绿茶儿茶素(主要是EGCG)时，不会引起生物学上显著的副作用，最近的一项化学预防研究表明，这些含有EGCG的儿茶素在抑制前列腺癌前病变向前列腺癌的进展方面是安全和非常有效的。体外观察表明，EGCG的抗癌活性可能源于其在癌前和/或恶性前列腺上皮细胞中参与细胞死亡途径(即，诱导细胞凋亡)的能力，而不是正常前列腺上皮细胞。EGCG还被证明可以改变细胞氧化还原平衡和/或破坏肿瘤细胞的线粒体功能，这可能是其抗癌活性的基础。EGCG的这些假定的化学预防特性在转化的前列腺上皮细胞中还没有得到广泛的研究。这项拟议的研究将探讨这一假说：与正常前列腺细胞相比，代表前列腺癌不同阶段(即永生化、致癌和恶性细胞)的前列腺上皮细胞在生物能量过程(即氧化磷酸化)和氧化还原状态(即产生活性氧)方面显示出显著的变化。这些生物能量和氧化还原的变化，可能在癌症发生的早期，决定了对癌症化学预防药物EGCG诱导细胞凋亡的敏感性。这一假说将通过完成两个特定的目标来实现：1)比较和对比体外正常、癌前和恶性前列腺上皮细胞的生物能量表型与体内与前列腺癌发生相关的可能的遗传变化(例如，雄激素受体、表皮生长因子受体、前列腺特异性抗原、P53、Mn-SOD和Bcl-2蛋白表达的变化)；2)评估癌症化学预防药物EGCG在体外对正常、癌前和恶性前列腺上皮细胞诱导凋亡的相对敏感性，并确定这些细胞对凋亡诱导的敏感性、遗传的前列腺癌特征和线粒体功能/氧化还原状态(如耗氧量和活性氧产生)的可能变化是否存在相关性。

DESCRIPTION (provided by applicant): Prostate cancer is one of the most frequently diagnosed tumors, and the second leading cause of cancer death among men in the United States. There appears to be an important link between bioenergetics, apoptosis, and prostate carcinogenesis. Several studies propose that androgens and their receptors may act directly on the mitochondria to alter mitochondrial function during prostate carcinogenesis. Furthermore, reactive oxygen species production that apparently results from aberrant changes in mitochondrial function in prostate epithelial cells apparently drives tumorigenesis in the prostate. The indolent nature of prostate tumorigenesis strongly suggests that a chemopreventive strategy would be effective in preventing malignancy. Epigallocatechin-3- gallate (EGCG), the principal polyphenolic component in green tea catechins, has emerged as a promising prostate cancer chemopreventive agent. Green tea catechins (mainly EGCG) causes no biologically significant adverse side effects when relatively high doses are administered orally to humans, and a recent chemoprevention study showed that these EGCG-containing catechins were safe and very effective in suppressing the progression of prostate premalignant lesions to prostate cancer. In vitro observations suggest that the anticancer activity of EGCG may arise from its ability to engage cell death pathways (i.e., induce apoptosis) in premalignant and/or malignant prostate epithelial cells while sparing their normal counterparts. EGCG has also been shown to alter cellular redox homeostasis and/or disrupt mitochondrial function in tumor cells, which may be fundamental to its anticancer activity. These putative chemopreventive properties of EGCG have not been investigated extensively in transformed prostate epithelial cells. The proposed study will investigate the hypothesis: prostate epithelial cells representing various stages of prostate carcinogenesis (i.e., immortalized, tumorigenic, and malignant cells) exhibit marked changes in bioenergetic processes (i.e., oxidative phosphorylation) and redox status (i.e., reactive oxygen species production) compared to their normal counterparts. These bioenergetic and redox changes, perhaps in early-stage carcinogenesis, dictate sensitivity to apoptosis induction by the cancer chemopreventive agent EGCG. The hypothesis will be addressed by completing two specific aims: 1) compare and contrast the bioenergetic phenotypes of normal, premalignant, and malignant prostate epithelial cells in vitro with putative genetic changes (e.g., changes in androgen receptor, epidermal growth factor receptor, prostate-specific antigen, p53, Mn-SOD, and Bcl-2 protein expression) associated with prostate carcinogenesis in vivo; and 2) assessing the relative sensitivity to apoptosis induction by the cancer chemopreventive agent EGCG among normal, premalignant, and malignant prostate epithelial cells in vitro, and ascertain if there is a correlation between sensitivity to apoptosis induction, genetic prostate carcinogenesis signatures, and possible changes in mitochondrial function/redox status (e.g., oxygen consumption and reactive oxygen species production) in these cells.