Determining Epigenetic Targets of Milk Thistle Extract in Prostate

描述(由申请人提供)：拟议研究的总体目标是发现水飞蓟衍生化合物的表观遗传调控的等位基因靶标。水飞蓟提取物已被用作包括前列腺癌在内的多种上皮性癌症的实验性预防和治疗药物。虽然这种提取物中活性化合物的确切直接或间接分子靶标尚未确定，但我们显示了初步证据表明，部分纯化的水飞蓟提取物水飞蓟宾影响各种前列腺肿瘤细胞系中EZH2蛋白的调节和活性。EZH2是一种蛋白质甲基转移酶，可以改变染色质结构，导致DNA甲基转移酶重新聚集到基因启动子上。它也被认为是人类更具侵袭性的前列腺癌和乳腺癌的生物标志物。鉴于水飞蓟宾对表观遗传事件的已知修饰物的影响，我们假设水飞蓟的肿瘤预防特性可能是通过表观遗传机制进行的。这项拟议的工作采用了一种探索性的全基因组方法，通过开发一个两部分筛选系统来揭示水飞蓟宾的表观遗传靶标。在第一个筛选中，在没有遗传异质性的情况下表现出高表达变异的等位基因是通过检测来自因非前列腺癌相关原因而接受前列腺切除术的无关个体的正常人类前列腺组织中的蛋白质表达来确定的。在第二个筛选中，使用前列腺癌细胞系鉴定了对重复剂量水飞蓟宾有不同反应的等位基因。正在测试的假设是，在正常组织中表现出高表达水平异质性的等位基因，也被反复接触水飞蓟宾影响的等位基因是亚稳定的表观等位基因；也就是，在正常组织中最容易受到表观遗传调控的等位基因。通过识别这些等位基因并了解它们在正常组织中的表观遗传异质性，我们推进了对水飞蓟宾等饮食因素如何长期作用于前列腺组织的理解。与公共卫生相关：拟议研究的总体目标是发现受水飞蓟提取物影响的亚稳等位基因。水飞蓟提取物已被用作包括前列腺癌在内的多种上皮性癌症的实验性预防和治疗药物。通过识别这些等位基因并了解它们在正常组织中的表观遗传异质性，我们推进了我们对水飞蓟宾等膳食补充剂如何长期作用于前列腺组织的理解。

DESCRIPTION (provided by applicant): The overall goal of the proposed research is to discover allelic targets for epigenetic regulation by milk thistle-derived compounds. Extracts of milk thistle (Silybum marianum L. Gaertn) have been investigated as experimental preventive and therapeutic agents against a variety of epithelial cancers including prostate cancer. While the precise direct or indirect molecular targets of the active compounds in this extracts have not been identified, we show preliminary evidence that the partially purified milk thistle extract silibinin affects the regulation and activity of the protein EZH2 in a variety of prostate tumor cell liners. EZH2 is a protein methyltransferase that can alter chromatin structure and lead to recruitment of DNA methyltransferases to gene promoters. It is also been characterized as a biomarker of the more aggressive prostate and breast cancers in humans. Given the effects of silibinin on a known modifier of epigenetic events, we hypothesize that the tumor preventative properties of milk thistle may proceed through epigenetic mechanisms. The proposed work takes an exploratory genome-wide approach to uncovering epigenetic targets of silibinin by developing a two part screening system. In the first screen, alleles that show high expression variation in the absence of genetic heterogeneity are determined by examining protein expression in normal human prostate tissue from unrelated individuals undergoing prostatectomies for non-prostate cancer related reasons. In the second screen, alleles that show differential response to repeated dosing of silibinin are identified using a prostate tumor cells line. The hypothesis being tested is that alleles the show high expression level heterogeneity in a normal tissue, that are also affected by repeated exposure to silibinin are metastable epialleles; a.k.a, alleles most susceptible to epigenetic regulation in normal tissue. By identifying these alleles and understanding their epigenetic heterogeneity in a normal tissue, we advance our understanding of how dietary factors such as silibinin exert their effects on prostate tissue over the long term. PUBLIC HEALTH RELEVANCE: The overall goal of the proposed research is to discover metastable epialleles that are influenced by milk thistle extracts. Extracts of milk thistle (Silybum marianum L. Gaertn) have been investigated as experimental preventive and therapeutic agents against a variety of epithelial cancers including prostate cancer. By identifying these alleles and understanding their epigenetic heterogeneity in a normal tissue, we advance our understanding of how dietary supplements such as silibinin exert their effects on prostate tissue over the long term.