Bmi-1 and Skin Cancer Prevention

* 描述（由申请人提供）：Polycomb Group（PcG）蛋白的组蛋白修饰是一种极其重要的表观遗传机制，通过修饰染色质结构以打开或关闭（沉默）基因来控制基因表达。该系统包括两个调节复合物，PRC 2和PRC 1。PRC 2与染色质结合并使组蛋白H3在赖氨酸27处脱乙酰化，然后甲基化。这些事件是由PRC 2蛋白Ezh 2催化的，Ezh 2是一种组蛋白甲基转移酶。然后，三甲基化赖氨酸（H3 K27- 3 M）充当PRC 1复合物的Bmi-1蛋白的结合位点，其结合以改变染色质结构和基因表达。我们在培养的人皮肤癌细胞中正在进行的研究表明，用绿色茶多酚，（-）-表没食子儿茶素-3-没食子酸酯（EGCG）治疗，降低Bmi-1和Ezh 2 PcG蛋白的表达。我们提出，化学预防剂降低PcG蛋白水平和活性，导致细胞存活率降低。该基金主要研究人类皮肤癌细胞系和小鼠皮肤癌发生模型。然而，致癌物和化学预防剂作用的主要目标是正常的人表皮。因此，这个竞争性的修订建议增加了一个人体表皮的生理模型，我们的实验。这一新的研究方向将极大地促进EGCG、PcG蛋白功能与UVB应答之间相互作用的研究。本竞争性补充品的目的是使用模拟体内皮肤细胞分化的“表皮筏培养”系统来检查EGCG是否调节PcG蛋白功能以减弱UVB照射的影响，并且可以移植到小鼠真皮上作为研究人类皮肤体内行为的模型。这些模型模仿正常的人类皮肤生物学。这些研究大大扩展和扩大了我们研究的力量和范围。我们认为，这些研究是适当的基础上，我们对父母补助金的进展。我们假设Bmi-1和Ezh 2 PcG蛋白增强角质形成细胞的存活，并保护免受UVB或化学预防剂的攻击，并且通过EGCG下调这些蛋白质保护免受UVB依赖性癌症。这些研究将提供重要的见解，在癌症预防中的作用，使用临床前体内模型的人表皮分化的表没食子儿茶素没食子酸酯。

* DESCRIPTION (provided by applicant): Histone modification by Polycomb Group (PcG) proteins is an epigenetic mechanism of paramount importance that controls gene expression by modifying chromatin structure to open or close (silence) genes. This system includes two regulatory complexes, PRC2 and PRC1. PRC2 binds to chromatin and deacetylates and then methylates histone H3 at lysine 27. These events are catalyzed by the PRC2 protein Ezh2, a histone methyltransferase. The trimethylated lysine (H3 K27-3M) then serves as a binding site for the Bmi-1 protein of the PRC1 complex which binds to alter chromatin structure and gene expression. Our ongoing studies in cultured human skin cancer cells demonstrate that treatment with the green tea polyphenol, (-)-epigallocatechin-3-gallate (EGCG), reduces expression of the Bmi-1 and Ezh2 PcG proteins. We propose that chemopreventive agents reduce PcG protein level and activity leading to reduced cell survival. The parent grant focuses on human skin cancer cell lines and a murine skin carcinogenesis models. However, the primary target of carcinogen and chemopreventive agent action is normal human epidermis. Thus, this competitive revision proposal adds a physiological model of human epidermis to our experiments. This new direction will greatly facilitate study of the interplay between EGCG, PcG protein function and response to UVB challenge. The goal of this Competitive Supplement is to examine whether EGCG modulates PcG protein function to attenuate the impact of UVB irradiation using an "epidermal raft culture" system that mimics in vivo skin cell differentiation, and can be engrafted onto mouse dermis as a model to study in vivo behavior of human skin. These models mimic normal human skin biology. These studies significantly extend and expand the power and scope of our study. We argue that these studies are appropriate based on our progress on the parent grant. We hypothesize that Bmi-1 and Ezh2 PcG proteins enhance keratinocyte survival and protect against challenge with UVB or chemopreventive agent and that down-regulation of these proteins by EGCG protects against UVB-dependent cancer. These studies will provide important insights regarding the role of EGCG in cancer prevention using preclinical in vivo models of human epidermal differentiation.