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去甲基化机制研究鸟氨酸脱羧酶-抗酶（ODC-Az）在致癌过程中的新型抗肿瘤活性。ODC- az是一种胞内抑制鸟氨酸脱羧酶（ODC）活性的分子，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在动物和人口腔癌细胞中的表达明显降低。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改变了恶性表型。已知ODC-Az上调的几个基因在肿瘤细胞中由于启动子区域异常高甲基化而沉默。基于这些证据，本应用程序提出实验来检验以下假设；1) ODC-Az通过DNA异常高甲基化重新激活肿瘤细胞中沉默的肿瘤抑制相关基因；2)ODC-Az是一种潜在的生长性肿瘤抑制分子。本研究旨在利用新发展的策略，如cDNA阵列、基因工程动物癌症模型和蛋白质转导系统。这是一种新的有希望的途径来对抗肿瘤细胞中肿瘤抑制基因的生长和分化以及沉默机制。DNA甲基化对正常生长、侵袭和转移功能相关的调控基因的影响机制有待进一步研究。本研究有两个具体目的：1)阐明ODC-Az在人头颈癌中调控的基因表达谱；2)验证ODC-Az作为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是否可以作为生理生长抑制因子、终末分化诱导剂和DNA去甲基化诱导剂用于肿瘤抑制基因的再激活治疗癌症患者。

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.