Identification of Green Tea Polyphenol-Targeted Genes

描述(申请人提供)：绿茶多酚似乎对某些癌症有化学预防作用，包括口腔癌；但癌细胞如何死亡，而正常细胞如何在这种多酚暴露下存活尚不清楚。缺乏这些信息阻碍了多酚在口腔癌化学预防或治疗中的临床应用。这项研究的长期目标是阐明绿茶多酚不同于正常和恶性细胞的信号通路和机制，以直接保护或诱导细胞凋亡。我们实验室的初步数据表明，正常上皮细胞表达p57(KIP2)以剂量和时间依赖的方式响应绿茶多酚。我们提出了一个新的概念，即绿茶多酚可以激活两条通路：1)p57介导的生存通路和/或2)caspase 3依赖的凋亡通路。需要检验的假设是，绿茶多酚对正常上皮细胞p57的诱导可能具有抗凋亡功能，而在恶性细胞中p57反应的缺失可能导致caspase3依赖的细胞凋亡的诱导。这项提议的直接目标是确定受绿茶多酚调控的生存或凋亡基因。在这项拟议的项目中，将在绿茶多酚暴露后，在正常人表皮角质形成细胞和人类口腔鳞状细胞癌细胞中确定存活/凋亡基因的表达谱。具体地说，将测定最有效的绿茶多酚(-)-表没食子儿茶素没食子酸酯(EGCG)在正常人类上皮细胞中诱导的p57表达水平。通过RT-PCR、信使核糖核酸稳定性分析、Northern和Western印迹分析，建立p57转录/翻译水平与EGCG作用时间/剂量之间的关系。在特定时间点的RNA样本将被用于基因阵列分析和图谱分析。不仅那些被EGCG激活或抑制的基因在正常或肿瘤细胞中的表达谱，而且未来化疗干预的有希望的细胞靶点也可能被识别。根据这项提议产生的数据可能会揭示治疗头颈癌的新药物靶点。

DESCRIPTION (provided by applicant): Green tea polyphenols appear to be chemopreventive against certain cancers, including oral cancer; but how cancer cells succumb while normal cells survive this polyphenol exposure is not known. Lack of this information prevented clinical uses of polyphenols for oral cancer chemoprevention or treatment. The long-term goal of this investigation is to elucidate the signal pathways and mechanisms by which green tea polyphenols differentially target normal and malignant cells to direct protective or apoptotic effects. Preliminary data from our laboratories have demonstrated that normal epithelial cells express p57 (KIP2) in response to green tea polyphenols in a dose- and time-dependent manner. We propose a novel concept, that green tea polyphenols are able to activate two pathways: 1) a p57-mediated survival pathway, and/or 2) a caspase 3-dependent apoptosis pathway. The hypotheses to be tested is that p57 induction by green tea polyphenols in normal epithelial cells may serve an anti-apoptotic function, absence of the p57 response in malignant cells may result in induction of caspase 3-dependent apoptosis. The immediate goal of this proposal is to identify the survival or apoptotic genes that are regulated by green tea polyphenols. In this proposed project, the survival/apoptosis gene expression profile will be determined following green tea polyphenol exposure, in normal human epidermal keratinocytes and in human oral squamous cell carcinoma cells. Specifically, the levels of p57 expression induced by the most potent green tea polyphenol, (-)- epigallocatechin-3-gallate (EGCG), in normal human epithelial cells will be determined. Using RT-PCR, mRNA stability assay, Northern and Western blot analyses, the relationship between transcription/translation levels of p57 induction and the time/dose of EGCG will be established. The RNA samples at specific time points will be subjeted to gene array analysis and profiling. Not only will the expression profile of those genes that are either activated or suppressed by EGCG in normal or tumor cells, but promising cellular targets for future chemotherapeutic intervention may be identified. Data generated from this proposal may reveal novel drug targets for treatment of head and neck cancer.