Suppression of Melanoma Initiation and Progression by NM23-H1

描述（由申请人提供）：皮肤恶性黑色素瘤（CMM）是最致命的皮肤癌，其发病率在美国和世界各地以惊人的速度增长。暴露于有害的紫外线辐射（UVR）显然是该疾病的一个危险因素，最近在年轻女性中晒黑床的使用与黑色素瘤发病率急剧增加之间的联系证实了这一点。更好地了解CMM发展为转移形式的机制可能为提高生存率提供重要的新治疗方法。转移抑制基因如NM23-H1（小鼠NM23-M1）的研究为黑色素瘤转移的分子机制提供了新的见解。该应用基于我们的新观察，即NM23-H1是一种3‘-5’外切酶，在体外对DNA具有校对活性，其3‘-5’外切酶活性是转移抑制功能所必需的，并且该蛋白促进uvr诱导的DNA损伤的修复。此外，本项目建立的转基因小鼠模型首次概括了NM23-H1在uvr诱导的CMM中的转移抑制功能。我们的研究结果支持一种模型，即NM23-H1表达的缺失导致基因组完整性受损和突变，从而推动CMM的恶性进展。在Specific Aim 1中，NM23-M1和NM23-M2对紫外线辐射诱导的转移性黑色素瘤的贡献将在缺乏其中一种或两种亚型表达的转基因小鼠品系中确定。在Specific Aim 2中，将阐明NM23蛋白促进DNA修复通路的分子机制，并在细胞培养和肿瘤细胞解释模型系统中评估干扰这些通路对转移抑制活性的影响。Specific Aim 3将应用强大的全基因组测序和RNA-seq技术对原发性和转移性黑色素瘤进行大规模平行测序，以确定候选的转移驱动基因组改变和基因表达谱。这些研究将首次系统分析转移抑制基因对抗恶性进展的特异性DNA修复和相关途径，并首次将转基因小鼠模型应用于研究转移抑制基因在CMM中的功能。我们的研究应该提供新颖和关键的见解，可以追求对抗晚期和致命形式的黑色素瘤。

DESCRIPTION (provided by applicant): Cutaneous malignant melanoma (CMM) is the most lethal form of skin cancer, and its incidence has been increasing at an alarming rate in the U.S. and around the world. Exposure to damaging ultraviolet radiation (UVR) is clearly a risk factor for the disease, borne out by the recent linkage between tanning bed usage and dramatically increased melanoma incidence in young females. Better understanding of the mechanisms by which CMM progresses to metastatic forms is likely to provide important new therapeutic approaches for improving survival rates. The study of metastasis suppressor genes, such as NM23-H1 (NM23-M1 in mouse), has provided new insights into molecular mechanisms underlying melanoma metastasis. This application builds on our novel observations that NM23-H1 is a 3'-5' exonuclease which exerts proofreading activity on DNA in vitro, that its 3'-5' exonuclease activity is required for metastasis suppressor function, and that the protein promotes repair of UVR-induced lesions in DNA. In addition, transgenic mouse models developed for this project recapitulate for the first time the metastasis suppressor function of NM23-H1 in UVR-induced CMM. Our findings support a model in which loss of NM23-H1 expression results in compromised genomic integrity and mutations that drive malignant progression in CMM. In Specific Aim 1, the contributions of NM23-M1 and NM23-M2 to UV radiation-induced metastatic melanoma will be determined in transgenic mouse strains deficient in expression of one, or both, of the isoforms. In Specific Aim 2, the molecular mechanisms underlying promotion of DNA repair pathways by NM23 proteins will be elucidated, and the impact of perturbing those pathways on metastasis suppressor activity assessed in cell culture and tumor cell explanation model systems. Specific Aim 3 will apply the powerful technologies of massively parallel sequencing for whole genome sequencing and RNA-seq to primary and metastatic melanomas to identify candidate metastasis-driving genomic alterations and gene expression profiles. The proposed studies will provide the first systematic analysis of specific DNA repair and related pathways through which a metastasis suppressor gene opposes malignant progression, as well as the first application of a transgenic mouse model to the study of metastasis suppressor function in CMM. Our studies should provide novel and critical insights that can be pursued to combat melanoma in its advanced and lethal forms. PUBLIC HEALTH RELEVANCE: While cutaneous malignant melanoma (CMM) is treated surgically with some success in its early stages, conventional treatments are ineffective once the disease has spread, or metastasized, to distant organs. This application is directed to elucidating the mechanisms that underlie metastasis in CMM, particularly that caused by overexposure to damaging ultraviolet radiation. These studies have considerable potential to improve diagnosis and prognosis of CMM patients, and to provide novel insights for effective treatments of the disease in its most advanced and lethal stages.