Products of the Transforming Genes of Polyomavirus

描述(申请人提供)：多瘤病毒中T(MT)负责小鼠多瘤病毒(PYV)的肿瘤发生。否则，含有突变MT的野生型病毒不会诱发肿瘤。转基因MT会导致许多组织中的肿瘤，为乳腺癌等疾病提供了有价值的模型。对MT的研究导致了磷脂酰肌醇3-激酶(PI3K)和蛋白质酪氨酸磷酸化的发现。许多证据表明，对MT的持续研究将为肿瘤转化和肿瘤发生提供新的见解。我们的中心假设是，MT通过调节细胞信号中的特定步骤来促进转化，这些步骤不仅影响肿瘤细胞本身，还影响相关的间质细胞，以支持肿瘤的进展。我们将集中在三个领域，MT研究可以为肿瘤转化提供新的见解：1)蛋白磷酸酶2A(PP2A)：我们已经发现的A？MT激活c-src过程中PP2A的异构体表明了特定异构体的重要性。我们将研究PP2A的A亚基亚基异构体和PP2A的特定三聚体ABC复合体的丢失在MT转化中的作用。我们有证据证明一种新的模式，即MT将底物带到PP2A进行去磷酸化。脂类既是溶血磷脂酸(LPA)代谢的酶，也是转录共激活因子，是这种底物的例子，表明新的PP2A依赖的信号在转化中。我们将测试他们在转型中的作用。在脂类结合缺陷突变体的指导下，我们还将使用突变体和野生型(WT)MT的质谱学来发现额外的底物。2)PI3K：MT突变体E349K表明，PI3K募集到激活的酪氨酸激酶和信号激活下游靶分子如Akt之间存在一个步骤，到目前为止还没有被认识到。缺陷的性质将在等电点脂类和蛋白质定位的研究中确定。利用质谱学比较E349K和WT，我们将寻求确定细胞蛋白(S)的责任。识别PI3K信号的新中间体将是范式的转变，并为治疗干预提供新的可能性。3)细胞因子：尽管细胞因子的表达被认为是肿瘤发生的重要部分，但在理解控制细胞因子表达模式的信号方面进展甚微。更重要的是，癌症信号改变对细胞因子的反应的想法在很大程度上还没有被探索过。我们的证据表明，MT在诱导细胞因子表达的同时，也改变了肿瘤细胞对细胞因子的反应。我们将通过基因阵列和蛋白质分析来确定MT在肿瘤细胞和基质细胞中对细胞因子表达和反应的影响范围。利用遗传工具，我们将研究MT用来完成这一任务的机制，并对宿主的遗传背景如何调节反应进行新颖的测试。最后，我们将询问这些效应如何决定巨噬细胞在体外的募集和体内的肿瘤发生研究。因此，我们的工作将填补我们对细胞因子知识的空白，并确定它们在MT乳腺肿瘤发生中的作用。 公共卫生相关性：多瘤病毒广泛存在于人类和动物群体中，为正常细胞和癌细胞的生长调控提供了基本的见解。利用这些病毒，我们试图确定导致肿瘤生长、侵袭和转移的新途径。我们希望这将提高我们对癌症的理解，并为其治疗提供新的可能性。

DESCRIPTION (provided by applicant): Polyomavirus middle T (MT) is responsible for murine polyomavirus (PyV) tumorigenesis. Otherwise wild type viruses that have mutant MT fail to induce tumors. Transgenic MT causes tumors in many tissues, providing valuable models for diseases such as breast cancer. Studies of MT led to the discovery of phosphoinositide 3-kinase (PI3K) and protein tyrosine phosphorylation. Much evidence suggests that continued study of MT will yield new insights into neoplastic transformation and tumorigenesis. Our central hypothesis is that MT promotes transformation by the modulation of specific steps in cell signaling that affect not only the tumor cell itself, but also associated stromal cells, to support tumor progression. We will focus on three areas where MT studies can offer novel insight into neoplastic transformation: 1) Protein phosphatase 2A (PP2A): The role we have uncovered for the A? isoform of PP2A in activation of c- src by MT points to the importance of specific isoforms. We will examine the role of both A subunit isoforms of PP2A and loss of specific trimeric ABC complexes of PP2A in MT transformation. We have evidence for a new model whereby MT brings substrates to PP2A for dephosphorylation. The lipins, which are both enzymes of the lysophosphatidic acid (LPA) metabolism and also transcriptional coactivators, are examples of such substrates that point to novel PP2A-dependent signaling in transformation. We will test their role in transformation. Guided by a mutant defective in lipin binding, we will also use mass spectrometry of mutant and wild type (WT) MT to uncover additional substrates. 2) PI3K: MT mutant E349K shows that there is a step, so far unappreciated, between PI3K recruitment to activated tyrosine kinases and signaling to activate downstream targets such as Akt. The nature of the defect will be determined in studies of PI lipids and protein localization. Using mass spectrometry comparing E349K to WT, we will seek to identify the cellular protein(s) responsible. Identification of a new intermediate in PI3K signaling would be paradigm shifting and offer new possibilities for therapeutic intervention. 3) Cytokines: Although cytokine expression is well recognized to be an important part of tumorigenesis, little progress has been made in understanding the signals that control the patterns of cytokine expression. More importantly, the idea that cancer signaling alters responses to cytokines is largely unexplored. Our evidence shows that MT both induces cytokine expression and at the same time alters the response of tumor cells to cytokines. We will determine the spectrum of effects on cytokine expression and response that MT has both in tumor cells and on stromal cells by gene array and protein analysis. Using genetic tools we will investigate the mechanisms MT uses to do this and carry out novel tests of how the genetic background of the host modulates responses. Finally, we will ask how these effects determine macrophage recruitment in vitro and tumorigenesis in vivo studies. Our work will thus close gaps in our knowledge of cytokines and determine their contribution to MT mammary tumorigenesis. PUBLIC HEALTH RELEVANCE: Widespread in human and animal populations, polyomaviruses have provided fundamental insights into growth regulation of normal and cancer cells. Using these viruses, we seek to identify new pathways responsible for tumor growth, invasion and metastasis. We expect this will improve our understanding of cancer and offer new possibilities for its treatment.