Redox Effects of Selenium for Prostate Cancer Prevention

描述(申请人提供)：最近的研究表明，硒(Se)可降低人类前列腺癌的发病率，并在体外诱导前列腺癌细胞凋亡和生长抑制。然而，硒的潜在化学预防机制(S)仍不清楚。Se产生超氧阴离子自由基被认为是可能的机制之一。我们的研究表明，Se通过产生超氧阴离子自由基，上调P53、p21(Waf1)、Bax和一些抗氧化酶的表达，诱导细胞凋亡和生长抑制，提示Se通过氧化还原(Redox)介导对P53活化的影响。因此，我们推测，Se诱导前列腺癌细胞生长抑制和凋亡的部分机制是通过调节细胞氧化还原状态，导致P53、Bax和p21(Waf1)的上调和激活。具体目标1是通过检测细胞抗氧化状态、活性氧水平和硒处理后的氧化应激，确定硒在正常前列腺上皮细胞、永生化上皮细胞和癌细胞中是否具有不同的氧化还原效应。具体目的2是确定超氧阴离子自由基的产生是否在Se对P53的磷酸化和激活以及随后的细胞生长抑制和凋亡的氧化还原效应中起主要作用，以及线粒体是否是细胞凋亡的主要靶点或途径；这一目标将通过基因转染和siRNA沉默改变超氧化物歧化酶(SOD)的水平来测试。超氧阴离子自由基和线粒体SOD2水平将与Se的细胞效应相关。目的3通过基因转染和siRNA沉默改变P53及其靶基因Bax和p21(Waf1)的状态，抑制Bax和p21(Waf1)信号转导通路，以确定P53及其靶基因Bax和p21(Waf1)在Se诱导的细胞凋亡和细胞周期停滞中的作用。建议的研究将为深入了解硒在前列腺癌化学预防中的作用机制(S)和分子靶点提供帮助，并有助于开发特定和有效的饮食干预策略来预防前列腺癌。

DESCRIPTION (provided by applicant): Recent studies demonstrated that selenium (Se) reduced prostate cancer incidence in humans and induced apoptosis and growth inhibition of prostate cancer cells in vitro. However, the underlying chemopreventive mechanism(s) of Se remains unclear. Production of superoxide radicals by Se has been considered as one of the potential mechanisms. Our studies showed that Se induced cell apoptosis and growth inhibition with superoxide radical production and up-regulation of p53, p21(Waf1), Bax, and some antioxidant enzymes, suggesting a reduction-oxidation (redox)-mediated effect of Se on the activation of p53. Thus, we hypothesize that Se induces growth inhibition and apoptosis of prostate cancer cells in part by modulating cell redox state resulting in upregulation and activation of p53, Bax, and p21(Waf1). Specific Aim 1 is to determine whether Se has differential redox effects in normal prostate epithelial cells, immortalized epithelial cells, and cancer cells by measuring cellular antioxidant status, levels of reactive oxygen species, and oxidative stress following Se treatment. Specific Aim 2 is to determine whether superoxide radical production plays a major role in redox effects of Se on p53 phosphorylation and activation and subsequent cell growth inhibition and apoptosis and whether mitochondria are the primary targets or pathways for cell apoptosis; this aim will be tested by altering levels of superoxide dismutases (SOD) using gene transfection and siRNA silencing. Levels of superoxide radical and mitochondrial SOD2 will be correlated with cellular effects of Se. Specific Aim 3 is to determine the role of p53 and its target genes Bax and p21(Waf1) in Se-induced apoptosis and cell cycle arrest using gene transfection and siRNA silencing to alter p53 status and suppress Bax and p21(Waf1) pathways. The proposed studies will provide insights into the mechanism(s) and molecular targets of Se in prostate cancer chemoprevention and help in the development of specific and effective dietary intervention strategies for prostate cancer prevention.