Succinylation and Malonylation as Novel Protein Modifications in Cancer

描述（由申请人提供）：由于许多癌症缺乏有效的治疗方法，并且对现有疗法产生耐药性，因此确定针对许多人类恶性肿瘤的新靶点和干预策略至关重要。这项多PI指导的研究将确定以前未被识别的可逆蛋白质翻译后修饰（赖氨酸琥珀酰化和丙二酰化）在恶性状态发展中的重要性。本申请中描述的研究来自两个令人兴奋的新研究进展。第一个是基于我们最近的发现，表明细胞中几种代谢酶存在新的翻译后蛋白质修饰。这些修饰似乎受到线粒体蛋白Sirt 5的调节，Sirt 5是Sir 2蛋白家族的成员（沉默信息调节因子2）。第二个是重新关注细胞代谢在癌症进展中所起的作用。对于癌细胞表现出的增强的糖酵解活性（“瓦尔堡效应”）和显著升高的谷氨酰胺代谢（即“谷氨酰胺成瘾”），情况尤其如此。当结合我们的初步研究结果表明，Sirt 5是所需的一些人类癌细胞的转化表型，这些不同的证据使我们提出了新的假设，脱琥珀酰化和/或脱丙二酰化的关键酶在癌症代谢是必不可少的，以满足生物合成和生物能量的要求恶性转化。我们将在细胞培养实验（目标1）和小鼠模型（目标2）中检验这一假设，并描述癌细胞恶性状态（目标1）需要脱丙二酰化/去琥珀酰化的分子机制。此外，我们相信，靶向Sirt 5并阻断其调节癌细胞中这些翻译后修饰的能力将为干预这种疾病提供新的方法。我们将鉴定特异性靶向Sirt 5的新型小分子抑制剂（Aim 3），并证明其在细胞培养（Aim 1）和Kras诱导的肺癌小鼠模型（Aim 2）中阻断恶性转化的有效性，这是一种特别需要开发新治疗策略的恶性肿瘤。虽然一部分肺癌可以用EGF受体抑制剂成功治疗，但大约25-50%的携带Kras突变的肺腺癌对这些抑制剂以及化疗具有抗性，并且临床上有效的靶向Kras的药物仍然难以捉摸。因此，我们认为，开发靶向这些新的Sirt 5调节的翻译后修饰作为帮助“重置”癌细胞的改变的代谢的手段的策略代表了一种变革性方法，其最终可以证明对肺癌患者有益，并且鉴于癌症中代谢改变的基本性质，提供针对广泛的人类恶性肿瘤的一般治疗益处。

DESCRIPTION (provided by applicant): The lack of effective treatments for many cancers and the occurence of resistance to available therapies make it critically important to identify new targets and strategies for intervention against a number of human malignancies. This multi-PI-directed study will set out to establish the importance of previously unrecognized, reversible protein posttranslational modifications (lysine succinylation and malonylation) in the development of the malignant state. The studies described in this application arise from two exciting new research developments. The first is based on our very recent discovery suggesting the existence of novel post-translational protein modifications on several metabolic enzymes in cells. These modifications appear to be regulated by the mitochondrial protein Sirt5, a member of the Sir2 family of proteins (for Silent information regulator 2). The second involves the renewed attention being directed toward understanding the roles played by cellular metabolism in cancer progression. This is especially the case for the enhanced glycolytic activity (the "Warburg effect") and markedly elevated glutamine metabolism (i.e. "glutamine addiction") exhibited by cancer cells. When combined with our preliminary findings suggesting that Sirt5 is required for the transformed phenotypes of a number of human cancer cells, these different pieces of evidence have led us to put forward the novel hypothesis that the desuccinylation and/or demalonylation of key enzymes in cancer metabolism are essential for satisfying the biosynthetic and bioenergetic requirements of malignant transformation. We will test this hypothesis in cell culture experiments (Aim 1) and mouse models (Aim 2), as well as delineate the molecular mechanisms underlying the requirement of demalonylation/desuccinylation for the malignant state of cancer cells (Aim 1). Moreover, we believe that targeting Sirt5 and blocking its ability to regulate these post-translational modifications in cancer cells will offer new approaches for intervention against this disease. We will identify novel small molecule inhibitors that specifically target Sirt5 (Aim 3) and demonstrate their effectiveness at blocking malignant transformation in cell culture (Aim 1) and in a mouse model of Kras-induced lung cancer (Aim 2), a malignancy for which the development of new therapeutic strategies is especially needed. While a subset of lung cancers can be treated successfully with EGF receptor inhibitors, the approximately 25-50% of lung adenocarcinomas harboring Kras mutations are resistant to these inhibitors as well as chemotherapy, and clinically effective drugs targeting Kras have remained elusive. Thus, we feel that developing strategies that target these novel Sirt5-regulated post- translational modifications as a means to help 're-set' the altered metabolism of cancer cells represents a transformative approach that could ultimately prove beneficial to lung cancer patients, as well as provide a general therapeutic benefit against a broad range of human malignancies, given the fundamental nature of metabolic alterations in cancer.