Role of SIRT3 in melanoma development and progression

黑色素瘤是最致命的皮肤癌之一，它是由黑素细胞引起的 黑色素的产生。对黑色素瘤生物学理解的最新进展导致了 有希望的靶向治疗。例如，BRAF抑制剂维莫拉非尼和达普拉非尼达到 显著改善了化疗，并被批准用于转移性黑色素瘤的BRAF- 突变。最近，达普拉非尼与MEK抑制剂曲美替尼的联合应用显示出改善 与单一疗法相比，无进展生存，并已获得美国FDA的批准。然而， 即使采用联合治疗，大多数患者也会产生获得性耐药性，从而未能 实现肿瘤的持久消退。因此，管理需要以目标为基础的新方法 黑色素瘤。哺乳动物sirtuin由七个已知成员(SIRT1-SIRT7)组成，具有 依赖于NAD的蛋白质脱乙酰酶和/或ADP-核糖基转移酶活性]。此外，他们也是 已知可调节翻译后的酰基修饰。SIRT在重要的细胞过程中发挥着关键作用， 并被证明与包括癌症在内的各种疾病的发病机制有关。SIRT的作用 在癌症中，它们是极其复杂的，它们似乎具有二分功能，这取决于细胞环境。 在已知的SIRT中，SIRT3是一种线粒体sirtuin，它协调线粒体活动的全球转移 通过脱乙酰化参与不同线粒体功能的蛋白质。它还扮演着重要的角色 调节多种细胞过程，包括转录、胰岛素分泌和细胞凋亡。事实是 SIRT3可以调节几个对癌细胞增殖至关重要的细胞过程，这使它成为一种 癌症管理的潜在治疗目标。而关于SIRT3在癌症中的作用的研究仍在进行中 它还处于起步阶段，研究表明它既有肿瘤抑制作用，也有肿瘤促进作用。然而，它的作用是 SIRT3在黑色素瘤中的作用尚不清楚。在我们的初步数据中，我们发现SIRT3在 黑色素瘤及其抑制在黑色素瘤细胞中产生显著的抗增殖反应。此外，我们 还发现SIRT3的一种新的小分子抑制剂4‘-溴-白藜芦醇(4BR)具有抗肿瘤作用。 人类黑色素瘤细胞的增殖效应。因此，根据现有文献和我们的初步数据，我们 建议验证SIRT3通过调节SIRT3在黑色素瘤进展中起关键作用的假设 P53信号、Ku70-Bax相互作用和/或细胞代谢动态平衡。以下是具体目标 建议：1)定义SIRT3在黑色素瘤发生和发展中的作用，使用组织 从退伍军人患者的回顾黑色素瘤组织中创建的微阵列(TMA)和体外细胞 转化模型；2)确定P53信号转导、Ku70-Bax相互作用、细胞代谢 作为黑色素瘤细胞SIRT3下游决定因素的动态平衡；以及3)确定治疗 抑制SIRT3在1)BRAF-Pten小鼠黑色素瘤模型和患者来源的异种移植中的意义 (PDX)是用从退伍军人患者那里收集的转移性黑色素瘤组织开发的。我们预计 本申请中提出的研究结果可能定义SIRT3在 黑素细胞转化与黑色素瘤进展。这可能最终会导致小说的发展 黑色素瘤的诊断、预后或治疗方法。因为黑色素瘤的发病率似乎 在退伍军人群体中较高，我们拟议的研究旨在定义 黑色素瘤的发展可能导致发现新的策略来管理这种致命的 肿瘤。因此，我们拟议的工作对退伍军人的医疗保健和 符合退伍军人事务部的使命。

Melanoma, one of the deadliest cancer of skin, arises from melanocytic cells that are responsible for melanin production. Recent advances in the understanding of melanoma biology has led to the development of targeted therapies with promise. For example, BRAF inhibitors vemurafenib and dabrafenib achieved significant improvement over chemotherapy and were approved for metastatic melanomas with BRAF- mutations. More recently, the combination of dabrafenib with MEK inhibitor trametinib demonstrated improved progression-free survival, compared to monotherapy, and has received approval from the US FDA. However, even with the combination treatment, most of the patients develop acquired resistance, thereby failing to achieve lasting tumor regression. Therefore, novel target-based approaches are needed for the management of melanomas. The mammalian sirtuins constitute a family of seven known members (SIRT1 – SIRT7) with NAD+-dependent protein deacetylase and/or ADP-ribosyltransferase activities]. In addition, they are also known to regulate post-translational acyl modifications. SIRTs play critical roles in important cellular processes, and are shown to be involved in the pathogenesis of a variety of diseases, including cancer. The role of SIRTs in cancer is extremely complex and they appears to have dichotomous functions depending on cell contexts. Among known SIRTs, SIRT3 is a mitochondrial sirtuin, which coordinates global shift in mitochondrial activity by deacetylating proteins involved in diverse mitochondrial functions. It also plays important roles in the regulation of a variety of cellular processes, including transcription, insulin secretion, and apoptosis. The fact that SIRT3 can regulate several cellular processes which are critical in cancer cell proliferation, makes it a potential therapeutic target for cancer management. While the research on the role of SIRT3 in cancer is still in its infancy, studies have suggested its tumor suppressor as well as tumor promoter roles. However, the role of SIRT3 in melanoma is not known. In our preliminary data, we have found that SIRT3 is overexpressed in melanoma and its inhibition results in a significant anti-proliferative response in melanoma cells. Further, we have also found that 4'-bromo-resveratrol (4BR), a new small molecule inhibitor of SIRT3, imparts anti- proliferative effects in human melanoma cells. Thus, based on available literature and our preliminary data, we propose to test the hypothesis that SIRT3 plays a critical role in melanoma progression via modulating p53 signaling, Ku70-Bax interaction and/or cellular metabolic homeostasis. The following specific aims are proposed: 1) o define the role of SIRT3 in melanoma development and progression, employing a tissue microarray (TMA) created from retrospective melanoma tissues from veteran patients, and an in vitro cell transformation model; 2) to define the involvement of p53 signaling, Ku70-Bax interaction, cellular metabolic homeostasis, as downstream determinants of SIRT3 in melanoma cells; and 3) to determine the therapeutic significance of SIRT3 inhibition in vivo in 1) Braf-Pten mouse melanoma mode, and patient derived xenografts (PDX) developed with prospectively collected metastatic melanoma tissues from veteran patients. We expect that the outcome of studies proposed in this application may define the role and mechanism of SIRT3 in melanocytic transformation and melanoma progression. This may ultimately lead to development of novel diagnostic, prognostic or therapeutic approaches for melanoma. Since melanoma incidence seems to be higher in the veteran population and our proposed study aimed at defining the molecular mechanism of melanoma development may lead to identification of novel strategies for the management of this deadly neoplasm. Therefore, our proposed work is relevant and significant to the health care of Veterans and is in line with the mission of the Department of Veteran Affairs.