c-Myc Phosphorylation Sites Regulate Its Apoptotic and Tumorigenic Potential

c-Myc 磷酸化位点调节其凋亡和致瘤潜力

• 批准号: 7826589
• 负责人: ROSALIE C SEARS
• 金额: $ 31.44万
• 依托单位: OREGON HEALTH & SCIENCE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-07-01 至 2013-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7826589
• 关键词: Address; Affect; Alanine; Animal Model; Apoptosis; Apoptotic; Applications Grants; Atypia; Biological; Biological Assay; Breast Cancer Cell; Cancer cell line; Cell Proliferation; Code; Complex; Coupled; Defect; Development; Event; Future; Gene Expression Regulation; Gene Targeting; Goals; Grant; Helper-Inducer T-Lymphocyte; Human; Hyperplasia; Impairment; In Vitro; Knock-in Mouse; Knowledge; Malignant Neoplasms; Mammary gland; Molecular; Mouse Strains; Mus; Mutate; Mutation; Oncogene Proteins; Oncogenic; Pathway interactions; Phospho-Specific Antibodies; Phosphorylation; Phosphorylation Site; Positioning Attribute; Primary Cell Cultures; Property; Proteins; Proto-Oncogene Proteins c-myc; Regulation; Research; Role; Sampling; Serine; Signal Pathway; Site; Specimen; T-Lymphocyte; Testing; Therapeutic; Threonine; Threonine Phosphorylation Site; Tissues; Transactivation; c-myc Genes; cancer cell; cell transformation; genetic manipulation; in vivo; leukemia; malignant breast neoplasm; metaplastic cell transformation; mouse model; mutant; non-genetic; novel; overexpression; public health relevance; response; transcription factor; tumor; tumorigenesis; tumorigenic

DESCRIPTION (provided by applicant): The c-Myc transcription factor is a potent inducer of cell proliferation and transformation, and elevated levels of c-Myc protein are observed in most human tumors. However, c-Myc overexpression also induces apoptosis, which limits c-Myc's tumorigenic potential. There are two conserved phosphorylation sites, Threonine 58 (T58) and Serine 62 (S62) that differentially regulate c-Myc protein stability in response to mitogenic stimulation, where S62 phosphorylation increases c-Myc stability, while T58 phosphorylation decreases c-Myc stability. Recent evidence suggests that phosphorylation at these sites also regulates c-Myc's apoptotic versus tumorigenic potential. Specifically, low phosphorylation at T58 and high phosphorylation at S62, which is the signature for more stable c-Myc, appears to suppress c-Myc's apoptotic activity and enhance its proliferative properties. Recent results indicate that lower T58 and higher S62 phosphorylation occurs in some tested human cancer cell lines with aberrantly stabilized c-Myc protein due to deregulation of the pathway that controls c-Myc degradation. Moreover, similarly altered phosphorylation of c-Myc has been detected in primary breast cancer samples. This suggests that cancer cells may contain a more oncogenic form of c-Myc. The objective of this grant is to examine the role of phosphorylation at T58 and S62 in controlling c-Myc's apoptotic versus proliferative activity, and whether this mechanism contributes to c-Myc's transforming activity in human cancer. The following specific aims will be pursued: 1) Examine the activity of c-Myc T58 and S62 phosphorylation mutants in vivo using a unique mouse model; 2) Investigate mechanisms that could underlie the different phenotypic responses to expression of c-Myc T58 and S62 phosphorylation mutants; and 3) Examine the phosphorylation status of c-Myc at T58 and S62 in human cancer cells and whether manipulation of c-MycWT phosphorylation can affect its oncogenic potential. These aims involve the study of novel inducible c-myc knock-in mice that express either wild-type c-Myc or c-Myc T58 or S62 phosphorylation mutants in specific tissues, in vitro and in vivo assays to investigate the underlying mechanisms of how these sites affect c-Myc activity, and an analysis of human cancer to explore the relevance of altered phosphorylation at these sites and whether cell transformation can be affected by non-genetic manipulation of c-Myc T58 and S62 phosphorylation. This research has important therapeutic implications, since targeting the pathway that regulates T58 and S62 phosphorylation could potentially affect both c-Myc expression levels and tumorigenic activity. PUBLIC HEALTH RELEVANCE: The proposed research focuses on understanding how the oncogenic potential of the transcription factor c-Myc is affected by its phosphorylation status at two highly conserved sites, which also regulate its protein stability. Importantly, elevated expression of c-Myc is widely observed in many different human tumors and therefore understanding mechanisms that increase or decrease c-Myc's oncogenic potential are critical to the development of future therapies targeting this potent oncoprotein.

描述（由申请人提供）：c-Myc转录因子是细胞增殖和转化的有效诱导剂，并且在大多数人类肿瘤中观察到c-Myc蛋白水平升高。然而，c-Myc 过度表达也会诱导细胞凋亡，这限制了 c-Myc 的致瘤潜力。有两个保守的磷酸化位点，苏氨酸 58 (T58) 和丝氨酸 62 (S62)，可差异调节 c-Myc 蛋白稳定性以响应有丝分裂刺激，其中 S62 磷酸化增加 c-Myc 稳定性，而 T58 磷酸化降低 c-Myc 稳定性。最近的证据表明，这些位点的磷酸化还调节 c-Myc 的凋亡与致瘤潜力。具体而言，T58 处的低磷酸化和 S62 处的高磷酸化（这是更稳定的 c-Myc 的标志）似乎可以抑制 c-Myc 的凋亡活性并增强其增殖特性。最近的结果表明，由于控制 c-Myc 降解的途径失调，一些测试的 c-Myc 蛋白异常稳定的人类癌细胞系中出现较低的 T58 和较高的 S62 磷酸化。此外，在原发性乳腺癌样本中也检测到了类似的 c-Myc 磷酸化改变。这表明癌细胞可能含有更具致癌性的 c-Myc。这笔资助的目的是检查 T58 和 S62 磷酸化在控制 c-Myc 凋亡与增殖活性中的作用，以及这种机制是否有助于 c-Myc 在人类癌症中的转化活性。我们将追求以下具体目标：1）使用独特的小鼠模型在体内检查c-Myc T58和S62磷酸化突变体的活性； 2) 研究c-Myc T58和S62磷酸化突变体表达的不同表型反应的机制； 3) 检查人类癌细胞中 c-Myc T58 和 S62 的磷酸化状态，以及 c-MycWT 磷酸化的操作是否会影响其致癌潜力。这些目标包括研究在特定组织中表达野生型 c-Myc 或 c-Myc T58 或 S62 磷酸化突变体的新型诱导型 c-myc 敲入小鼠，进行体外和体内测定以研究这些位点如何影响 c-Myc 活性的潜在机制，并分析人类癌症以探索这些位点磷酸化改变的相关性以及细胞转化是否可以 受 c-Myc T58 和 S62 磷酸化非遗传操作的影响。这项研究具有重要的治疗意义，因为针对调节 T58 和 S62 磷酸化的途径可能会影响 c-Myc 表达水平和致瘤活性。公共健康相关性：拟议的研究重点是了解转录因子 c-Myc 的致癌潜力如何受到其两个高度保守位点的磷酸化状态的影响，这也调节其蛋白质稳定性。重要的是，c-Myc 表达升高在许多不同的人类肿瘤中广泛观察到，因此了解增加或减少 c-Myc 致癌潜力的机制对于开发针对这种强效癌蛋白的未来疗法至关重要。