Mdig gene and histone demethylation in lung cancer

描述(申请人提供)：肺癌是世界上最常见的癌症，每年导致130万人死于癌症。尽管在阐明机制和开发新的治疗方案方面做出了广泛的努力，但全球肺癌的死亡率仍然很高。我们的长期目标是了解mDIG基因在人类肺癌发生发展中的作用，以及mDIG基因能否作为暴露于环境或职业危害的肺癌的生物标志物和治疗靶点。本应用的目的是探讨MDig蛋白在环境和职业危害/致癌物诱导的肺细胞增殖和致癌转化中的作用。中心假说是，MDig通过组蛋白去甲基酶的作用来促进细胞的生长和转化，该酶拮抗组蛋白H3上的三甲基赖氨酸9。组蛋白H3三甲基赖氨酸9的下调将促进肺上皮细胞细胞周期调控和恶性转化相关基因的表达。这一建议背后的理论基础是mDig基因的表达可能在肺细胞增殖和环境致癌物反应的致癌转化中起关键作用。为了实现这一应用的目标，我们将利用细胞株和裸鼠作为实验模型，追求三个特定的目标：(1)检测mDig蛋白对组蛋白H3上三甲基化赖氨酸9的潜在去甲基酶活性；(2)确定细胞周期调控基因如细胞周期蛋白、cdc25s和检查点蛋白的表达是否受到mDig甲基化调控；(3)在Beas-2B细胞和A549细胞中，分别通过上调和下调mdig的表达来研究其在细胞培养和裸鼠体内接种后的致瘤作用。在完成这些特定的目标后，我们希望能够确定mdig如何在肺细胞生长调节和致癌转化中对导致肺癌的因素做出反应。此外，基于初步研究，我们还预计mDig的结构性表达将损害组蛋白H3上赖氨酸9的三甲基化，导致异染色质的减弱或其他抑制性表观遗传标记的形成。因此，与细胞周期转变和细胞增殖相关的基因的表达将得到增强。最后，除了揭示以前未知的人类肺癌的新机制外，mDIG的表达有望成为人类肺癌的一个新的生物标志物和治疗靶点。公共卫生相关性：肺癌是美国与恶性肿瘤相关的死亡的主要原因。它比任何其他类型的恶性肿瘤导致更多的美国人死亡。肺癌的主要原因是环境和职业暴露于致癌物质，包括吸烟和职业粉尘。本项目将通过下调组蛋白H3上赖氨酸9的三甲基化和异染色质的形成来验证mDIG基因诱导细胞生长和转化的假说，从而探讨新发现的肺癌相关基因mDIG在介导致癌物诱发肺癌中的作用机制。其长期目标是了解mdig基因如何在环境和职业危害诱发的人类肺癌的发生和发展中起作用，寻找早期发现肺癌的生物标志物，并开发干预和预防策略。

DESCRIPTION (provided by applicant): Lung cancer is the most common cancer worldwide, accounting for 1.3 million cancer deaths annually. Despite extensive efforts to elucidate mechanisms and develop new therapeutic regimens, the worldwide mortality rate of lung cancer remains high. Our long- term goal is to understand how mdig gene contributes to the initiation and progression of the human lung cancer and whether mdig can be served as a biomarker and a therapeutic target for lung cancer resulted from exposure to environmental or occupational hazards. The objective of this application is to investigate the role of Mdig protein played on the lung cell proliferation and carcinogenic transformation induced by environmental and occupational hazards/carcinogens. The central hypothesis is that Mdig promotes cell growth and transformation by functioning as a histone demethylase that antagonizes tri-methyl lysine 9 on histone H3. Down-regulation of tri-methyl lysine 9 of histone H3 will enhance the expression of genes associated with the cell cycle regulation and malignant transformation in lung epithelial cells. The rationale behind this proposal is that expression of mdig gene may be critical for lung cell proliferation and carcinogenic transformation in response to environmental carcinogens. To accomplish the objectives of this application, we will pursue three specific aims by using cell lines and nude mice as experimental models: (1) test the potential demethylase activity of mdig protein toward tri-methylated lysine 9 on histone H3; (2) determine whether the expression of the cell cycle-regulated genes, such as cyclins, Cdc25s and checkpoint proteins, is regulated by the methylation regulation of mdig; and (3) study the tumorigenic effect of mdig by both over- expression and down-regulation of mdig in BEAS-2B cells and A549 cells, respectively, in both cell culture and inoculation of the cells in nude mice. At the completion of these specific aims, we expect to have determined how mdig contributes to lung cell growth regulation and carcinogenic transformation in response to factors that cause lung cancer. We additionally expect, based on preliminary studies, that constitutive expression of mdig will compromise the tri-methylation of lysine 9 on histone H3, leading to attenuation of heterochromatin or the formation of other inhibitory epigenetic markers. As a result, the expression of genes associated with the cell cycle transition and cell proliferation will be enhanced. Finally, in addition to reveal a previously unknown new mechanism of the human lung cancer, it is anticipated that expression of mdig can be potentially served as a new biomarker and therapeutic target of the human lung cancer. PUBLIC HEALTH RELEVANCE: Lung cancer is the leading cause of malignant-related deaths in the United States (US). It kills more Americans than any other type of malignancy. The main cause of lung cancer is the environmental and occupational exposure to carcinogens, including tobacco smoking and occupational dust. This project will investigate the mechanism of mdig gene, a newly identified lung cancer associated gene, in mediating carcinogen-induced lung cancer by testing the hypothesis that mdig inducing cell growth and transformation through down regulation of the tri-methylation of lysine 9 on histone H3 and the heterochromatin formation. The long-term goals are to understand how mdig gene contributes to the initiation and progression of the human lung cancer induced by environmental and occupational hazards, to identify biomarkers for early detection of the lung cancer and to develop intervention and prevention strategies.