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发生之间似乎存在重要联系。一些研究表明，雄激素及其受体可能直接作用于线粒体，改变前列腺癌发生过程中线粒体的功能。此外，前列腺上皮细胞中线粒体功能异常引起的活性氧物质的产生显然驱动了前列腺中的肿瘤发生。前列腺肿瘤发生的惰性性质强烈表明化学预防策略将有效预防恶性肿瘤。表没食子儿茶素没食子酸酯（Epigallocatechin-3- gallate，EGCG）是绿色茶儿茶素的主要多酚类成分，是一种很有前途的前列腺癌化学预防剂。绿色茶儿茶素（主要是表没食子儿茶素没食子儿茶素）在相对高剂量口服给药时不会引起生物学上显著的不良副作用，最近的一项化学预防研究表明，这些含表没食子儿茶素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且非常有效的。体外观察表明，EGCG的抗癌活性可能源于其参与细胞死亡途径的能力（即，诱导细胞凋亡），而不影响它们的正常对应物。EGCG还显示出改变肿瘤细胞中的细胞氧化还原稳态和/或破坏线粒体功能，这可能是其抗癌活性的基础。这些推定的化学预防性质的表没食子儿茶素没有被广泛研究转化的前列腺上皮细胞。拟议的研究将调查这一假设：前列腺上皮细胞代表前列腺癌发生的各个阶段（即，永生化的、致瘤的和恶性的细胞）在生物能量过程中表现出显著的变化（即，氧化磷酸化）和氧化还原状态（即，活性氧物质的产生）。这些生物能量和氧化还原的变化，可能在早期阶段的致癌作用，决定了敏感性细胞凋亡诱导的癌症化学预防剂表没食子儿茶素没食子酸酯。该假设将通过完成两个具体目标来解决：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推定的遗传变化（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）与体内前列腺癌发生相关;和2）在体外评估正常、癌前和恶性前列腺上皮细胞对癌症化学预防剂EGCG诱导的细胞凋亡的相对敏感性，并确定对凋亡诱导的敏感性、遗传前列腺癌发生特征和线粒体功能/氧化还原状态的可能变化（例如，氧消耗和活性氧物质产生）。

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.