ODC-Az as a Tumor Suppressor by DNA Demethylation

描述(由申请人提供)：这是一项为期四年的提案，旨在通过DNA去甲基化机制检测鸟氨酸脱羧酶-抗酶(ODC-Az)在致癌过程中的新的抗肿瘤活性。ODC-Az是一种鸟氨酸脱羧酶(ODC)活性的细胞内抑制分子，可导致多胺耗竭，参与抗增殖和分化。与正常口腔癌细胞相比，ODC-Az在动物和人类口腔癌细胞中的表达显著减少。ODC-Az基因在口腔癌细胞中的强制表达通过重新激活参与肿瘤抑制的基因而改变了恶性表型。由于启动子区域的异常高甲基化，ODC-Az上调的几个基因在肿瘤细胞中被沉默。基于这一证据，本申请提出了实验来验证以下假设：1)ODC-Az重新激活因DNA异常高甲基化而沉默的肿瘤细胞中的肿瘤抑制相关基因，2)ODC-Az是一个潜在的生理性肿瘤抑制分子。这项建议旨在利用新开发的策略，如cDNA阵列、癌症基因工程动物模型和蛋白质转导系统。这是一个新的和有希望的途径，以对抗肿瘤细胞生长和分化的失控以及肿瘤抑制基因的沉默机制。DNA甲基化可能会影响参与正常生长、侵袭和转移功能的调控基因，其机制将在拟议的研究中进行探讨。本研究的目的有二：1)阐明ODC-Az对人头颈部癌基因表达的调控作用；2)验证ODC-Az作为一种生理性肿瘤抑制分子的作用。该项目的长期目标是确定ODC-Az是否可以作为一种生理性生长抑制因子、终末分化诱导剂和DNA去甲基化诱导剂在癌症患者的治疗中重新激活抑癌基因。

DESCRIPTION (provided by applicant): This is a four-year proposal to examine novel anti-tumor activities of ornithine decarboxylase-antizyme (ODC-Az) in carcinogenesis by a DNA demethylation mechanism. ODC-Az is an intracellular inhibitory molecule of ornithine decarboxylase (ODC) enzyme activity that causes polyamine depletion, which is, implicated in anti-proliferation and differentiation. Expression of ODC-Az is, significantly reduced in animal and human oral cancer cells compared with normal counterparts. Forced-expression of the ODC-Az gene in oral cancer cells altered malignant phenotype by re-activation of genes involved in tumor suppression. Several genes up regulated by ODC-Az are known to be silenced in tumor cells owing to aberrant hypermethylation of the promoter region. Based on this evidence, this application proposes experiments to test the following hypotheses; 1) ODC-Az re-activates tumor suppression-related genes silenced in tumor cells by DNA aberrant hypermethylation, 2) ODC-Az is a potential physiological tumor suppressor molecule. This proposal is design to utilize newly developed strategies, such as cDNA arrays, genetically engineered animal of cancer models and protein transduction systems. This is a novel and promising pathway to counter the deregulated growth and differentiation as well as the silencing mechanism of tumor suppressor genes in cancer cells. The mechanism, by which the regulatory genes involved in normal function of growth invasion and metastasis may become affected by DNA methylation, will be, investigated in the proposed studies. There are two Specific Aims in this proposal: 1) To elucidate the gene expression profile regulated by ODC-Az in human head and neck cancer and 2) To validate ODC-Az as a physiological tumor suppressor molecule. The long-term goal of this project is to determine if ODC-Az could be use therapeutically as a physiological growth suppressor, inducer of terminal differentiation, and inducer of DNA demethylation for reactivation of tumor suppressor genes in the treatment of patients with cancer.