ALKBH5 and nickel-induced lung carcinogenesis

项目摘要 镍化合物是公认的人类致癌物。流行病学研究报告称， 长期暴露于镍化合物后肺癌和鼻癌的发病率增加， 环境或职业暴露。越来越多的证据表明，表观遗传的改变 景观，包括DNA甲基化和组蛋白修饰，是镍诱导的重要机制 肺癌发生然而，镍暴露对表转录组的影响以及镍对表转录组的潜在作用还有待进一步研究。 镍致癌作用中的RNA修饰从未被探索过。我们的初步研究发现， 暴露于镍化合物的人支气管上皮细胞表现出降低的母源性 表达基因3（MEG3），一种在许多类型的肿瘤中下调的印记基因， 镍诱导恶性转化的驱动因素。此外，镍上调m6A脱甲基酶ALKBH 5， mRNA和蛋白表达与MEG3 RNA不稳定一致，表明ALKBH 5可能 通过调节全局或基因特异性m6A丰度有助于细胞转化。此外，Knockdown ALKBH 5完全消除了镍暴露细胞中的MEG 3降解，表明RNA甲基化 可能在保护MEG3稳定性方面起作用。然而，尚不清楚镍如何上调ALKBH 5以及 增加的ALKBH 5是否介导镍诱导的细胞转化。另外，m6A丰度 调节MEG3 RNA稳定性的基因在很大程度上仍然未知。因此，在本申请中， 提出解决镍诱导的MEG3不稳定的关键事件。第一个目标是解决 增加的ALKBH 5足以在体外诱导恶性转化。第二个目标将针对 潜在的上游调节因子和下游效应因子介导镍诱导的ALKBH 5表达， MEG3不稳定。据我们所知，这是第一个解决环境影响的建议， 镍暴露对m6A酶以及转录组范围或基因特异性m6A的变化 甲基化图谱。这一提议的成功将有助于我们理解镍如何靶向RNA 修饰酶或RNA结合蛋白，以启动或促进肺肿瘤形成，并进一步鉴定 m6A酶作为预后生物标志物或治疗靶点的新方面， 肺癌患者。

Project Summary Nickel compounds are well-established human carcinogens. Epidemiological studies have reported an increased incidence of lung and nasal cancer following long-term exposure to nickel compounds due to either environmental or occupational exposure. Growing evidence indicates that alterations of the epigenetic landscape, including DNA methylation and histone modification, are important mechanisms in nickel-induced lung carcinogenesis. However, the impact of nickel exposure on the epitranscriptome and the potential role of RNA modification in nickel carcinogenesis have never been explored. Our preliminary studies discovered that human bronchial epithelial cells exposed to nickel compounds exhibited reduced mRNA stability of maternally expressed gene 3 (MEG3), an imprinted gene that was downregulated in many types of tumors and a strong driver for nickel-induced malignant transformation. In addition, nickel upregulated m6A demethylase ALKBH5 mRNA and protein expression that coincided with MEG3 RNA destabilization, suggesting ALKBH5 may contribute to cell transformation via modulating global- or gene-specific m6A abundance. Moreover, knockdown of ALKBH5 completely abolished MEG3 degradation in nickel-exposed cells, suggesting that RNA methylation may play a role in protecting MEG3 stability. However, it is not clear how nickel upregulates ALKBH5 as well as whether increased ALKBH5 mediates nickel-induced cell transformation. Additionally, how m6A abundance modulates MEG3 RNA stability remains largely unknown. Therefore, in this application, two specific aims were proposed to address the key events in nickel-induced MEG3 destabilization. The first aim will address whether increased ALKBH5 is sufficient to induce malignant transformation in vitro. The second aim will target the potential upstream regulators and downstream effectors that mediate nickel-induced ALKBH5 expression and MEG3 destabilization. To the best of our knowledge, this is the first proposal to tackle the impact of environmental nickel exposure on the changes of m6A enzymes as well as transcriptome-wide or gene-specific m6A methylation profiles. Success of this proposal will facilitate our understanding of how nickel targets RNA modification enzymes or RNA binding proteins to initiate or promote lung tumor formation, and further identify new aspects of m6A enzymes as a prognostic biomarkers or therapeutic targets to improve clinical outcomes of lung cancer patients.