Timing of Exposure to Selenium and Isoflavones and Prostate Cancer Prevention

描述（由申请人提供）：本领域申请中描述的研究响应前列腺癌进展审查小组（PRG）报告中的建议。最近的数据表明，高硒（Se）的摄入或状态和高植物雌激素（异黄酮）的摄入都对前列腺癌有保护作用，并且它们的联合使用可能比单独使用任何一种饮食成分都更有益。PRG的报告建议“支持旨在更好地理解雄激素产生和营养物质在前列腺生理学中的作用的研究，例如……硒和植物雌激素……”这项工作的目的是评估高硒和异黄酮的单独和联合摄入对前列腺癌的保护作用，并评估饮食暴露时间的关键作用。最近的动物研究结果表明，怀孕时就开始接触这种物质会产生有益的影响，而性成熟后才开始接触这种物质则不会。为了确定这些作用的生化和分子机制，将把注意力集中在雄激素受体（AR）和NF-:B调节的过程上。具体目的1是证明高硒和异黄酮的饮食摄入，单独或联合，将抑制TRAMP（转基因腺癌小鼠前列腺）小鼠前列腺癌的进展，这取决于饮食干预的时间。在不同的时间点（受孕、6、12和18周）开始，并持续到不同的终点（6、12、18和24周），在2 × 2因子设计中，给TRAMP小鼠喂食足够或高硒、低或高异黄酮的饲料。测量所有动物在每个时间点的体重、泌尿生殖系统（GU）重量、可触及肿瘤的时间、病理肿瘤分级和转移发生率。具体目标2是证明高硒和异黄酮的饮食摄入，单独或联合，将降低雄激素受体（AR）和NF-:B的激活，并降低AR和NF-:B调节基因在TRAMP小鼠前列腺中的表达，这取决于饮食干预的时间。血液中雄激素、IGF-1和生长激素的水平将通过elisa测定，总硒通过荧光法测定，异黄酮水平通过高效液相色谱测定。测定硒依赖性谷胱甘肽过氧化物酶和5 α还原酶的活性。AR和NF-:B的活化将通过EMSA测定。通过RT-PCR检测前列腺癌相关的AR-和NF-: b调控基因的表达，这些基因的表达也被硒和/或异黄酮修饰。这些试验将显示每种膳食成分的单独影响，每种成分对其他成分代谢的调节作用，以及联合使用对目标终点的影响。这些措施与饮食干预时间和疾病进展的相关性将确定肿瘤生长期间补充可能最有效的时期。这项工作将通过联合食用不同的保护性膳食成分和肿瘤发生期间饮食干预的最佳时间来确定化学预防的机制。

DESCRIPTION (provided by applicant): The research described in this AREA application is responsive to recommendations in the Report of the Prostate Cancer Progress Review Group (PRG). Recent data demonstrate that high selenium (Se) intake or status and high intake of phytoestrogens (isoflavones) each provide a protective effect against prostate cancer, and that their combined use may provide greater benefit than either dietary component alone. The PRG report recommends "Support studies aimed at better understanding of the roles in androgen production and in prostate physiology of nutrients such as ... selenium [and] phytoestrogens..." The objective of this work is to assess the cancer protective effects in prostate of high consumption of Se and isoflavones, individually and in combination, and to assess the critical effect of the timing of dietary exposure. Recent results from animal studies suggest that exposure begun at conception produces beneficial effects not seen when exposure is started after sexual maturation. To identify biochemical and molecular mechanisms for those effects, attention will focus on processes regulated by the androgen receptor (AR) and by NF-:B. Specific Aim 1 is to demonstrate that high dietary intake of Se and isoflavones, individually and in combination, will inhibit progression of prostate cancer in TRAMP (TRansgenic Adenocarcinoma of Mouse Prostate) mice, dependent on the timing of dietary intervention. Beginning at different time points (conception, 6, 12, and 18 weeks) and continuing to different end points (6, 12, 18 and 24 weeks), TRAMP mice will be fed diets adequate or high in Se, and low or high in isoflavones in a 2 X 2 factorial design. Measurement of body weight, genitourinary (GU) tract weight, time to palpable tumor, pathological tumor grade, and incidence of metastases will be determined for all animals sacrificed at each time point. Specific Aim 2 is to demonstrate that high dietary intake of Se and isoflavones, individually and in combination, will reduce activation of the androgen receptor (AR) and NF-:B, and decrease expression of AR- and NF-:B-regulated genes in prostates of TRAMP mice, dependent on the timing of dietary intervention. Blood levels of androgen, IGF-1, and GH will be measured by ELISAs, total Se by fluorometry, and isoflavone levels by HPLC. Se-dependent glutathione peroxidase and 5alpha-reductase activities will be assayed. AR and NF-:B activation will be determined by EMSA. Expression of AR- and NF-:B-regulated genes relevant in prostate cancer, whose expression is also modified by Se and/or isoflavones, will be examined by RT-PCR. These assays will show individual effects for each dietary component, the modifying effects each has on the other's metabolism, and the effects of combined use on the end points of interest. Correlation of these measures with time of dietary intervention and disease progression will identify the period(s) during tumor growth when supplementation may be most efficacious. This work will identify mechanisms of chemoprevention by combined consumption of different protective dietary components and the optimum time during tumorigenesis for dietary intervention. PUBLIC HEALTH RELEVANCE: This work will accomplish several objectives outlined by the Prostate Cancer Progress Review Group and by the NIH Five Year Plan "Planning for Prostate Cancer". These include 1) "defining the role of specific dietary factors in the etiology and prevention of...cancer"; 2) increasing "understanding of the roles in...prostate physiology of nutrients"; 3) definition of "the mechanisms by which these nutrients alter risk"; and 4) demonstration of "the effects of nutrients on molecular events in the prostate". According to the NIH report "the effect of food constituents on molecular events in the prostate is unknown". Discovery of Se- and isoflavone-regulated genes will "identify biomarkers of the consumption of key dietary components".