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Molecular Mechanisms of GSTP1 Reactivation by Green Tea Polyphenols

绿茶多酚重新激活 GSTP1 的分子机制

基本信息

批准号：
8070446
负责人：
SANJAY GUPTA
金额：
$ 25.63万
依托单位：
CASE WESTERN RESERVE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2007
资助国家：
美国
起止时间：
2007-07-01 至 2013-05-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8070446
关键词：
Aberrant DNA Methylation Acetylation Adenocarcinoma Adverse effects Affect Alleles Animal Model Attention Binding Binding Proteins Biological Assay Carcinogens Case-Control Studies Catechin Cell Culture System Cells Chemopreventive Agent Chromatin Chromatin Structure Chromatin Structure Alteration Clinical Clinical Trials Complex Consumption CpG Islands DMA-methyltransferase DNA DNA Methylation DNA Methyltransferase DNA Modification Methylases DNA-Binding Proteins Deacetylation Deoxycytidine Detoxification Process Development Disease Dose Enzymes Epigallocatechin Gallate Epigenetic Process Event Family Future GSTP1 gene Gene Expression Gene Silencing Genes Genetic Transcription Genomics Green tea Growth Histone Acetylation Histone Deacetylase Inhibitor Histone H3 Histones Human Human Characteristics Implant LNCaP Laboratory Study Lead Malignant Epithelial Cell Malignant Neoplasms Malignant neoplasm of prostate Mediating Methyl-CpG-Binding Protein 2 Methylation Modeling Modification Molecular Mus Mutate Nail plate Nude Mice Oral Pathway interactions Pattern Phase Plasma Play Poison Prevention Preventive Process Prostate Prostate carcinoma Prostatic Neoplasms Protein Acetylation Protein Binding Domain Protein Family Proteins Recruitment Activity Regulation Repetitive Sequence Retrotransposon Role Series Source Specificity Staging Supplementation Tail Time Toxic effect Transcriptional Activation Transcriptional Regulation Transgenic Organisms Tumor Tissue base bisulfite cancer cell chromatin remodeling demethylation drinking drinking water enzyme activity gallocatechol gene repression genome-wide glutathione S-transferase pi histone acetyltransferase histone modification human disease in vivo inhibitor/antagonist mRNA Expression member novel promoter prostate cancer prevention prostate carcinogenesis protective effect protein H(3)protein expression research study transcription factor tumor tumor growth tumorigenesis

项目摘要

DESCRIPTION (provided by applicant): Aberrant DNA methylation and chromatin remodeling are common epigenetic changes that play critical role in gene silencing; implicated in the development and progression of prostate cancer. One such alteration is silencing of the expression of glutathione S-transferase-pi (GSTP1), a critical enzyme of carcinogen defense, through methylation of deoxycytidine residue in CpG islands in the 5'-regulating region. Loss of GSTP1 function occurs in vast majority (>70%) of prostate tumors regardless of grade or stage and appears to be characteristic of human prostate tumorigenesis. Unlikely mutated genes; epigenetically silenced genes are intact and are attractive targets for agents that could 'wake up' these dormant genes. Reactivation of such genes could be accomplished by DNA methylation and/or histone deacetylase inhibitors however; clinical utility of these inhibitors has been limited due to severe side- effects and toxicity. In recent years, green tea and its major polyphenolic constituent, epigallocatechin-3-gallate (EGCG) has received much attention as a promising chemopreventive agent for prostate cancer. This notion is supported by recent case-control study (Int. J. Cancer 108:130-5, 2004); clinical trial (Cancer Res. 66:1234-40, 2006) and our observation demonstrating that oral consumption of green tea polyphenols (GTP) at human achievable dose results in significant inhibition of prostate carcinogenesis in transgenic adenocarcinoma of the mouse prostate (TRAMP) model that mimics human disease (Proc. Nail. Acad. Sci. USA 98:10350-5, 2001). Extensive laboratory studies in cell culture systems and in limited animal models have further demonstrated that GTP afford protective effects from diverse types of carcinogens and induce phase II enzyme activity that could lead to enhanced detoxification process. More recently GTP has been shown to inhibit the activity of DNA methyltransferase (Cancer Res. 63:7563-70, 2003). Importantly, if drinking green tea can restore or compensate the loss of GSTP1 activity in the prostate and can slow down the process of prostate carcinogenesis that may have relevance for prevention and/or treatment of this disease. In the proposed studies we further our understanding of how GTP and EGCG mediate reactivation of GSTP1 gene, silenced during prostate carcinogenesis. Through a series of exploration, we will specifically investigate whether these molecular mechanism(s) are mediated through epigenetic pathways related to i) demethylation and activation of aberrantly methylated GSTP1 gene, ii) modulation in binding and expression of transcriptional repressers: methyl CpG binding domain (MBD) proteins, DNA methyltransferases (DNMTs), and histone deacetylases (HDAC) to methylated DNA iii) alteration in activity and expression of histone acetyltransferases (HAT), iv) histone modification, and v) global hypomethylation patterns. These studies will be conducted in human prostate carcinoma LNCaP and MDA PCa 2b cells, which possess hypermethylated GSTP1 CpG island alleles, devoid of GSTP1 mRNA and protein expression. This will be further validated in athymic nude mouse orthotopically implanted with prostate carcinoma cells. Completion of this proposal will establish an important role of green tea polyphenols in modulating epigenetic events and will provide a rationale to conduct prevention-based clinical trial. With the 'proof of principle' more structurally-related non- toxic compounds could be developed in future for prevention of prostate cancer in humans.

描述（由申请人提供）：异常DNA甲基化和染色质重塑是常见的表观遗传变化，在基因沉默中起关键作用;与前列腺癌的发生和进展有关。一种这样的改变是通过5 '调控区CpG岛中脱氧胞苷残基的甲基化沉默谷胱甘肽S-转移酶-pi（GSTP 1）（致癌物防御的关键酶）的表达。GSTP 1功能的丧失发生在绝大多数（>70%）的前列腺肿瘤中，无论其等级或分期如何，并且似乎是人前列腺肿瘤发生的特征。不太可能突变的基因;表观遗传沉默的基因是完整的，是有吸引力的目标，可以'唤醒'这些休眠的基因。这些基因的再活化可以通过DNA甲基化和/或组蛋白脱乙酰酶抑制剂来完成，然而，由于严重的副作用和毒性，这些抑制剂的临床应用受到限制。近年来，绿色茶及其主要多酚成分表没食子儿茶素没食子酸酯（epigallocatechin-3-gallate，EGCG）作为一种有前途的前列腺癌化学预防剂受到了广泛关注。这一观点得到了最近的病例对照研究（Int. J. Cancer 108：130-5，2004）、临床试验（Cancer Res.66：1234-40，2006）和我们的观察结果的支持，这些结果表明，在模拟人类疾病的小鼠前列腺转基因腺癌（TRAMP）模型中，以人类可达到的剂量口服绿色茶多酚（GTP）导致前列腺癌发生的显著抑制（Proc. Nail. Acad. Sci. USA 98：10350-5，2001）。在细胞培养系统和有限的动物模型中进行的广泛的实验室研究进一步表明，GTP提供了对不同类型的致癌物的保护作用，并诱导II相酶活性，这可能导致增强的解毒过程。最近，GTP已显示出抑制DNA甲基转移酶的活性（Cancer Res.63：7563-70，2003）。重要的是，如果喝绿色茶可以恢复或补偿前列腺中GSTP 1活性的损失，并可以减缓前列腺癌发生的过程，这可能与预防和/或治疗这种疾病有关。在这些研究中，我们进一步了解了GTP和EGCG如何介导前列腺癌发生过程中沉默的GSTP 1基因的重新激活。通过一系列的探索，我们将具体研究这些分子机制是否通过与i）异常甲基化的GSTP 1基因的去甲基化和激活，ii）转录抑制因子的结合和表达的调节相关的表观遗传途径介导：甲基CpG结合结构域（MBD）蛋白，DNA甲基转移酶（DNMT），和组蛋白脱乙酰酶（HDAC）转化为甲基化DNA iii）组蛋白乙酰转移酶（HAT）的活性和表达的改变，iv）组蛋白修饰，和v）整体低甲基化模式。这些研究将在人前列腺癌LNCaP和MDA PCa 2b细胞中进行，这些细胞具有高甲基化的GST 1 CpG岛等位基因，缺乏GST 1 mRNA和蛋白质表达。这将在原位植入前列腺癌细胞的无胸腺裸鼠中进一步验证。该提案的完成将确立绿色茶多酚在调节表观遗传事件中的重要作用，并将为进行基于预防的临床试验提供理论基础。有了“原理证明”，未来可以开发更多结构相关的无毒化合物来预防人类前列腺癌。