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)摄入量或状态和高摄入量的植物雌激素(异黄酮类)都可以预防前列腺癌，并且它们的联合使用可能比单独使用任何一种饮食成分提供更大的好处。PRG报告建议“支持旨在更好地了解营养素在雄激素产生和前列腺生理中的作用的研究，如……硒[和]植物雌激素……”这项工作的目的是评估单独和联合摄入高硒和异黄酮类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，在受孕时开始暴露会产生在性成熟后开始暴露时看不到的有益效果。为了确定这些影响的生化和分子机制，人们的注意力将集中在雄激素受体(AR)和核因子-B调节的过程上。具体目标1是证明高硒和异黄酮的饮食摄入量，单独和联合使用，将抑制TRAMP(转基因小鼠前列腺癌)小鼠的前列腺癌进展，这取决于饮食干预的时间。从不同的时间点(妊娠6、12和18周)开始，持续到不同的终点(6、12、18和24周)，按2×2析因设计饲喂适量或高硒、低或高异黄酮类的饲料。在每个时间点处死所有动物，测量体重、泌尿生殖道(GU)重量、肿瘤可触及的时间、病理肿瘤分级和转移发生率。具体目的2是证明，单独和联合摄入高硒和异黄酮会减少雄激素受体(AR)和核因子：B的激活，并减少TRAMP小鼠前列腺中雄激素受体(AR)和核因子：B调节基因的表达，这取决于饮食干预的时间。血中雄激素、胰岛素样生长因子-1和生长激素的水平将用ELISAs测定，总硒的测定采用荧光法，异黄酮类的测定采用高效液相色谱法。将测定依赖硒的谷胱甘肽过氧化物酶和5α-还原酶的活性。AR和NF-：B的激活将由EMSA确定。RT-PCR将检测与前列腺癌相关的AR-和NF-B调节基因的表达，这些基因的表达也被Se和/或异黄酮类化合物改变。这些分析将显示每种饮食成分的单独影响，每种成分对另一种新陈代谢的调节作用，以及联合使用对感兴趣的终点的影响。这些措施与饮食干预时间和疾病进展的相关性将确定在肿瘤生长期间(S)补充补充剂可能最有效的时期。这项工作将通过联合摄入不同保护性饮食成分来确定化学预防的机制，以及在肿瘤发生期间进行饮食干预的最佳时间。 公共卫生相关性：这项工作将实现前列腺癌进展审查小组和NIH五年计划“前列腺癌规划”概述的几个目标。其中包括1)“确定特定饮食因素在……癌症的病因和预防中的作用”；2)增加“对营养素在……前列腺生理学中的作用的认识”；3)定义“这些营养素改变风险的机制”；以及4)演示“营养素对前列腺分子事件的影响”。根据美国国立卫生研究院的报告，“食物成分对前列腺分子事件的影响尚不清楚”。硒和异黄酮类调控基因的发现将“识别关键膳食成分摄入量的生物标记物”。

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".