Epigenetic Regulators in Tumor Progression

描述（由申请人提供）：癌症进展涉及基因调控紊乱。在大约90%的人类恶性肿瘤发生的皮肤等上皮组织中，这一过程的最早步骤涉及分化和增殖基因的表达中断，导致异常的组织极性，预示着癌症的侵袭。肿瘤进展过程中基因失调的全基因组性质涉及全局活跃的表观遗传基因调节因子，然而，每种调节因子类别包含多种亚型，其在癌症中的特定作用尚未完全了解。在DNA甲基化的情况下，存在多个非冗余DNA甲基转移酶（dnmt），其主要通过沉默特定基因的表达起作用。在过去两年中发现的一组积极促进DNA去甲基化的基因可以拮抗DNMT的作用。然而，dnmt及其拮抗剂在人类组织早期肿瘤进展中的作用尚不清楚。这一修订提案的重点是描述DNA甲基化调节因子在早期肿瘤进展中的作用，特别是正常人类表皮向侵袭性肿瘤的转化。首先，我们将定义DNMT亚型在早期肿瘤进展中的作用。我们最近发现，在皮肤和其他组织的鳞状细胞癌（SCC）中错误表达的DNMT1控制着正常表皮生长和分化基因程序，并调节了在早期人类表皮肿瘤发生中发生改变的一个重要基因亚群。在Aim I中，我们将使用可诱导的ras驱动的表皮瘤变人体组织模型，测试一种添加性DNMT模型，其中DNMT1保持未分化的增殖状态，而DNMT3A/B/L沉默从头诱导肿瘤抑制基因。其次，我们将研究最近表征的dnmt拮抗蛋白的作用。最近发现，活性DNA去甲基化通过与碱基切除修复（BER）途径（MBD4、TDG和AID/Apobec2）和核苷酸切除修复（NER）途径（XPA、XPG、ERCC2、TAF12）相互作用的蛋白质进行。Gadd45蛋白与BER和NER机制相互作用，使DNA去甲基化。为了支持DNA去甲基化介质在肿瘤发生中的潜在作用，我们最近观察到Gadd45促进表皮分化并抑制异位肿瘤的形成，与特定基因的DNA甲基化减少有关。在Aim II中，我们将验证DNA去甲基化的特定介质抑制早期肿瘤进展的假设。在拟议的资金结束时，我们计划描述DNA甲基化调节因子在人体组织中肿瘤进展中的作用，作为未来癌症预防和治疗策略的基础。1

DESCRIPTION (provided by applicant): Cancer progression involves disordered gene regulation. In epithelial tissues such as skin, where ~90% of human malignancies arise, the earliest steps in this process involve disrupted expression of differentiation and proliferation genes, leading to the abnormal tissue polarity that presages cancerous invasion. The genome-wide nature of the gene dysregulation seen in the tumor progression process implicates globally active epigenetic gene regulators, however, each regulator class contains multiple isoforms whose specific roles in cancer are not fully understood. In the case of DNA methylation, there are multiple non-redundant DNA methyltransferases (DNMTs), which act primarily by silencing expression of specific genes. DNMT action is antagonized by a group of genes found over the past 2 years to actively promote DNA demethylation. The role of DNMTs and their antagonists in early tumor progression in human tissue, however, is unknown. This revised proposal focuses on characterizing the role of regulators of DNA methylation in early tumor progression, specifically the conversion of normal human epidermis to invasive neoplasia. First, we will define the role of DNMT isoforms in early tumor progression. We recently observed that DNMT1, which is mis-expressed in squamous cell carcinoma (SCC) of skin and other tissues, controls the normal epidermal growth and differentiation gene program and regulates a significant subset of the genes that are altered in early human epidermal tumorigenesis. Using an inducible human tissue model of Ras-driven epidermal neoplasia, in Aim I we will test an additive DNMT model in which DNMT1 maintains the undifferentiated proliferative state while DNMT3A/B/L silence de novo induction of tumor inhibitory genes. Second, we will study the role of recently characterized DNMT-antagonizing proteins. Active DNA demethylation has recently been found to proceed via proteins interacting with the base excision repair (BER) pathway (MBD4, TDG, and AID/Apobec2) and the nucleotide excision repair (NER) pathway (XPA, XPG, ERCC2, TAF12). Gadd45 proteins interact with both BER and NER mechanisms to enable DNA demethylation. In support of a potential role for mediators of DNA demethylation in tumorigenesis, we recently observed that Gadd45 promotes epidermal differentiation and inhibits ectopic tumor formation in association with diminishing DNA methylation at specific genes. In Aim II, we will test the hypothesis that specific mediators of DNA demethylation inhibit early tumor progression. At the end of proposed funding, we plan to have characterized the role of regulators of DNA methylation on tumor progression in human tissue as a foundation for future strategies for cancer prevention and treatment. 1 PUBLIC HEALTH RELEVANCE: Conversion of normal tissue into cancer involves progressively disordered gene expression. Epigenetic regulators possess the capacity to control global gene expression in cancer and other processes by altering genomic marks, such as DNA methylation. In epithelial tissues, such as skin, where ~90% of human malignancies arise, regulators of DNA methylation are abnormally expressed, however, their roles in cancer progression are undefined. The current proposal aims to characterize the role of regulators of DNA methylation on tumor progression in human tissue as a foundation for future strategies for cancer prevention and treatment. 1