Epigenetic Regulators in Tumor Progression

描述(申请人提供)：癌症进展涉及紊乱的基因调控。在皮肤等上皮组织中，约90%的人类恶性肿瘤发生，这一过程的最早步骤涉及分化和增殖基因的表达中断，导致组织极性异常，预示着癌症的侵袭。肿瘤进展过程中所见的基因失调的全基因组性质涉及全球活跃的表观遗传基因调节因子，然而，每个调节因子类别包含多种亚型，其在癌症中的具体作用尚不完全清楚。在DNA甲基化的情况下，有多个非冗余DNA甲基转移酶(DNMT)，它们主要通过沉默特定基因的表达来发挥作用。DNMT的作用被过去两年中发现的一组积极促进DNA去甲基化的基因所拮抗。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。这项修订后的建议侧重于表征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转化为侵袭性肿瘤的过程。首先，我们将确定DNMT亚型在早期肿瘤进展中的作用。我们最近观察到，DNMT1在皮肤和其他组织的鳞状细胞癌(SCC)中错误表达，控制正常的表皮生长和分化基因程序，并调节在人类早期表皮肿瘤发生过程中改变的一个重要基因亚集。利用RAS诱导的人表皮肿瘤组织模型，在目的I中，我们将测试加入性DNMT模型，在该模型中，DNMT1保持未分化的增殖状态，而DNMT3A/B/L沉默肿瘤抑制基因的从头诱导。其次，我们将研究最近鉴定的DNMT拮抗蛋白的作用。最近发现，DNA去甲基化是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)相互作用进行的。GADD45蛋白与BER和NER机制相互作用，使DNA去甲基化。为了支持DNA去甲基化的介体在肿瘤发生中的潜在作用，我们最近观察到GADD45促进表皮分化和抑制异位肿瘤的形成与减少特定基因的DNA甲基化有关。在AIM II中，我们将测试特定的DNA去甲基化介质抑制早期肿瘤进展的假设。在拟议的资金结束时，我们计划将DNA甲基化调节器在人类组织中的肿瘤进展中的作用表征为未来癌症预防和治疗策略的基础。1 与公共卫生相关：正常组织转化为癌症涉及到逐渐紊乱的基因表达。表观遗传调节器有能力通过改变基因组标记，如DNA甲基化，来控制癌症和其他过程中的全球基因表达。在皮肤等上皮组织中，约90%的人类恶性肿瘤发生，DNA甲基化调节因子异常表达，然而，它们在癌症进展中的作用尚不清楚。目前的提案旨在表征DNA甲基化调节者在人类组织中对肿瘤进展的作用，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