ATF2 Oncogenic Addiction in Melanoma

描述（由申请人提供）：了解致癌基因成瘾的潜在机制非常重要，因为它们在驱动肿瘤发生中起作用。这项提案的重点是一个新的发现，我们揭示了一种新的致癌基因成瘾机制。遗传N-RAS/Ink 4a小鼠黑色素瘤模型建立了转录因子ATF 2在黑色素瘤中的致癌作用。这是通过其组成性核定位实现的，其中ATF 2作为转录因子和DNA损伤反应蛋白具有活性。我们最近发现ATF 2的组成性核定位损害了这种蛋白质在胞质溶胶中的一种新的功能。在细胞暴露于遗传毒性后，ATF 2从细胞核输出以使其定位于线粒体外膜（线粒体外膜），在线粒体外膜处其损害线粒体电位并增强细胞凋亡。这一过程是一种新发现的机制的基础，通过这种机制，ATF 2促进细胞死亡。尽管在大多数细胞类型中可以看到ATF 2的这种线粒体功能， 它在黑素瘤中减弱或消失。此外，ATF 2定位于海马的能力由PKC β（PKC？）控制。黑色素瘤细胞表达高水平的PKC，其有效地将ATF 2锁定在细胞核中并阻止其在线粒体中的输出和功能。这些观察结果构成了我们假设的基础，即PKC对ATF 2核输出的控制构成了黑色素瘤中癌基因成瘾的新范式，因此为研究黑色素瘤发展和进展的未被识别的途径提供了独特的机会，这可以用于开发创新的治疗方式。我们提出的研究旨在回答我们最近发现的ATF 2对PKC？成瘾的关键问题，使用细胞生物学和新的相关遗传小鼠黑素瘤模型。我们将解决的主要问题包括：黑色素瘤中PKC上调的基础是什么，ATF 2肿瘤抑制活性的意义以及致癌ATF 2活性的机制。我们将建立条件性ATF 2基因敲入小鼠，这将使我们能够定义致癌和肿瘤抑制功能的ATF 2，分别。最后，我们将使用已经建立的高含量筛选来鉴定促进黑色素瘤细胞中ATF 2的核输出的天然化合物，从而为黑色素瘤提供新的治疗方式。

DESCRIPTION (provided by applicant): Understanding the mechanism underlying oncogene addiction is of major importance given their role in driving tumorigenesis. This proposal focuses on a new discovery, whereby we reveal a novel mechanism for oncogene addiction. A genetic N-RAS/Ink4a mouse melanoma model established the oncogenic role of the transcription factor ATF2 in melanoma. This is achieved through its constitutive nuclear localization, where ATF2 is active as a transcription factor and DNA damage response protein. We recently discovered that constitutive nuclear localization of ATF2 impairs a newly identified function for this protein in te cytosol. Following exposure of cells to genotoxic, ATF2 is exported from the nucleus to enable its localization at the mitochondrial outer membrane (MOM), where it impairs MOM potential and augments apoptosis. This process underlies a newly disclosed mechanism by which ATF2 contributes to cell death. Although this mitochondrial function of ATF2 is seen in most cell types, it is attenuated or lost in melanoma. Moreover, the ability of ATF2 to localize to the MOM is controlled by PKC epsilon (PKC¿). Melanoma cells express high levels of PKC¿, which effectively locks ATF2 in the nucleus and prevents its export and function at the mitochondria. These observations form the basis for our hypothesis that PKC¿ control of ATF2 nuclear export constitutes a novel paradigm for oncogene addiction in melanoma, and therefore offers unique opportunities for studying unrecognized pathways underlying melanoma development & progression, which can be exploited for development of innovative therapeutic modalities. Our proposed studies are designed to answer key questions that emerge from our recent discovery of ATF2 addiction to PKC¿, using cell biology, and new relevant genetic mouse melanoma models. Among the cardinal questions we will address are: what underlies PKC¿ upregulation in melanoma, the significance of ATF2's tumor suppressor activities and the mechanisms underlying oncogenic ATF2 activity. We will establish conditional ATF2 knock-in mice, which will allow us to define oncogenic and tumor suppressor functions of ATF2, respectively. Lastly, we will use a high- content screen, already established, to identify natural compounds that promote nuclear export of ATF2 in melanoma cells, thereby offering a novel therapeutic modality for melanoma.