Polycomb proteins and skin cancer prevention

描述（由申请人提供）：表皮鳞状细胞癌是人类最常见的癌症之一，发病率正在上升。因此，皮肤癌是一个重要的健康问题，并且晚期疾病会复发，并且危及生命和毁容。由于皮肤癌的发展在很长一段时间内涉及多种事件，因此预防是一个重要和首选的选择。出于这个原因，目前正在进行一项重大的努力，以确定可以口服或应用于皮肤表面的预防剂。特别是，我们集中在萝卜硫素（SFN），来自花椰菜，对Ezh2 Polycomb组（PcG）蛋白的功能的影响。PcG蛋白是重要的表观遗传调节因子，其甲基化和泛素化特异性组蛋白以产生封闭的染色质和沉默肿瘤抑制基因表达。关键的polycomb组蛋白，包括Ezh2，在皮肤癌中过表达，这驱动p21Cip1和其他肿瘤抑制因子的沉默，从而提高肿瘤细胞的存活率。我们已经表明，SFN抑制Ezh2，导致p21 Cip1表达增加。这些变化最终导致皮肤癌细胞增殖停止和癌细胞死亡增加。我们令人兴奋的未发表的初步研究表明，包括角质形成细胞存活和干细胞命运的两个主要调节因子DNp63a和KLF4的途径调节Ezh2水平。这些蛋白质以前没有被认为是重要的预防目标。我们假设在癌细胞中，DNp63a，KLF4通路刺激Ezh2基因表达，Ezh2基因表达反过来又降低p21Cip1表达，从而增加癌细胞存活。我们进一步提出SFN抑制该途径中的事件以减少Ezh2表达并增加肿瘤抑制因子表达。本提案中的实验围绕明确的预防相关目标展开。具体目的1研究DNp63a和KLF4如何调节Ezh2水平。具体目标2检查SFN对该途径的调节。特异性目的3检查了Ezh2对p21 Cip1表达的调节，特异性目的4解决了Ezh2和SFN治疗对体内肿瘤形成的影响。这些研究与理解SFN在预防皮肤癌形成中的生物学作用高度相关。

DESCRIPTION (provided by applicant): Epidermal squamous cell carcinoma is one of the most common forms of human cancer and the incidence is increasing. Thus, skin cancer is an important health concern and advanced disease recurs and is life- threatening and disfiguring. Because skin cancer development involves multiple events over a long period of time, prevention is an important and preferred option. For this reason there is a major ongoing effort to identify preventive agents that can be taken orally or applied on the skin surface. In particula, we have focused on the impact of sulforaphane (SFN), derived from broccoli, on function of the Ezh2 Polycomb Group (PcG) protein. PcG proteins are important epigenetic regulators that methylate and ubiquitinate specific histones to produce closed chromatin and silence tumor suppressor gene expression. Key polycomb group proteins, including Ezh2, are overexpressed in skin cancer and this drives silencing of p21Cip1 and other tumor suppressors leading to enhanced tumor cell survival. We have shown that SFN suppresses Ezh2 which leads to increased p21Cip1 expression. These changes ultimately lead to cessation of skin cancer cell proliferation and increased cancer cell death. Our exciting unpublished preliminary studies suggest that a pathway that includes two master regulators of keratinocyte survival and stem cell fate, DNp63a and KLF4, regulates Ezh2 level. These proteins have not been previously considered as important prevention targets. We hypothesize that in cancer cells a DNp63a, KLF4 pathway stimulates Ezh2 gene expression which, in turn, acts to reduce p21Cip1 expression leading to increased cancer cell survival. We further propose that SFN inhibits events in this pathway to reduce Ezh2 expression and increase tumor suppressor expression. Experiments in this proposal revolve around well-defined translation-relevant goals. Specific Aim 1 studies how DNp63a and KLF4 regulate Ezh2 level. Specific Aims 2 examines SFN regulation of this pathway. Specific Aim 3 examines Ezh2 regulation of p21Cip1 expression, and Specific Aim 4 address the impact of Ezh2 and SFN treatment on tumor formation in vivo. These studies are highly relevant to understanding the biological role of SFN in preventing skin cancer formation.