The effects of PTEN on tyrosine kinase signaling in breast cancer

描述（由申请人提供）：这些研究的目的是了解乳腺癌中10号染色体上肿瘤抑制因子磷酸酶和张力蛋白同源物缺失（PTEN）的影响，以及PTEN功能对酪氨酸激酶信号传导的影响。磷脂酰肌醇-3激酶（PI3K）途径的异常激活是人类癌症中最常见的分子改变之一，最常见的是PTEN的表达缺失或功能缺失突变。PTEN作为PI3K下游的脂质磷酸酶拮抗PI3K信号，但PTEN蛋白磷酸酶活性是否具有肿瘤抑制作用尚不清楚。PTEN缺乏导致酪氨酸受体激酶（rtk）的激活，包括胰岛素样生长因子- 1受体（IGF-IR）、胰岛素受体（InsR）和ErbB3/HER3，暗示PTEN参与PI3K上游和下游信号的调节。因此，我假设1)PTEN蛋白磷酸酶活性的肿瘤抑制作用涉及包括RTK在内的癌蛋白的直接去磷酸化，以及2)PTEN的丧失使癌细胞对RTK抑制敏感。支持假设1的结果表明，PTEN的缺失不仅增加了PI3K通路的信号传导，而且还通过尚未确定的蛋白导向通路增加了致癌信号传导。在这种情况下，抑制PI3K可能不足以阻断pten缺陷肿瘤的生长。支持假设2的结果将提供PTEN缺失作为可能从rtk导向治疗中获益的患者亚群的生物标志物。为了验证这些假设，我提出了以下具体目标：1)确定PTEN的缺失是否调节igf - 1、胰岛素和HER3受体信号传导；2)确定PTEN缺失是否对治疗性IGF-IR、InsR和HER3抑制剂敏感；3)发现PTEN蛋白的磷酸化底物及PTEN蛋白磷酸酶活性对酪氨酸激酶信号转导的整体影响。PTEN蛋白底物的全局分析和PTEN丢失对酪氨酸激酶信号传导的影响将确定PTEN的新作用，提供被PTEN丢失改变的候选磷酸化蛋白，并揭示信号通路之间的新联系。IGF-IR在大多数人类乳腺癌中表达，治疗性IGF-IR抑制剂正在开发中。确定PTEN缺失对IGF-IR信号传导和对IGF-IR靶向治疗的敏感性的影响，将揭示PTEN的新功能，并确定PTEN状态是否是对治疗反应的生物标志物。反过来，这些集体发现将允许优化针对IGF-IR和PI3K途径的治疗。本文提出的研究将在范德比尔特-英格拉姆癌症中心进行，该中心的设施和中心非常适合本研究中涉及的分子、遗传、蛋白质组学和活体动物成像分析。该机构还提供广泛的教学活动和职业发展机会，以加强对年轻研究人员的培训。以上的研究将在一个充满合作和跨学科研究的环境中为我提供强化的科学训练，以促进我的成长和独立。我的近期职业目标是获得一个独立的、终身的、助理教授的职位，以建立我自己的实验室和研究团队，长期目标是建立一个基于机制的癌症转化研究的校外资助项目。

DESCRIPTION (provided by applicant): The objective of these studies is to understand the effects of loss of the tumor suppressor Phosphatase and Tensin homolog deleted on chromosome 10 (PTEN) in breast cancer, and the effects of PTEN functions on tyrosine kinase signaling. Aberrant activation of the phosphatidylinositol-3 kinase (PI3K) pathway is one of the most frequent molecular alterations in human cancer, most often by loss of expression or loss-of-function mutations in PTEN. PTEN acts as a lipid phosphatase downstream of PI3K to antagonize PI3K signaling, but PTEN protein phosphatase activity has tumor suppressive effects which remain unresolved. PTEN deficiency results in activation of receptor tyrosine kinases (RTKs) including insulin-like growth factor-I receptor (IGF-IR), insulin receptor (InsR), and ErbB3/HER3, implicating PTEN in the modulation of signaling both upstream and downstream of PI3K. I therefore hypothesize that 1) the tumor suppressive effects of PTEN protein phosphatase activity involve direct dephosphorylation of oncoproteins including RTKs, and 2) PTEN loss sensitizes cancer cells to RTK inhibition. Results in support of hypothesis #1 would suggest that loss of PTEN not only increases PI3K pathway signaling, but also increases oncogenic signaling through protein-directed pathways that remain to be defined. In this case, PI3K inhibition may be insufficient to block the growth of PTEN-deficient tumors. Results in support of hypothesis #2 would offer PTEN loss as a biomarker of a patient subpopulation likely to benefit from RTK-directed therapy. To test these hypotheses, I propose the following Specific Aims: 1) To determine whether loss of PTEN modulates IGF-I, insulin, and HER3 receptor signaling; 2) To determine whether PTEN loss sensitizes to therapeutic inhibitors of IGF-IR, InsR, and HER3; 3) To discover phosphoprotein substrates of PTEN and the global effects of PTEN protein phosphatase activity on tyrosine kinase signaling. Global profiling of PTEN protein substrates and the effects of PTEN loss on tyrosine kinase signaling will identify novel roles of PTEN, offer candidate phosphoproteins altered by PTEN loss, and reveal new connections between signaling pathways. IGF-IR is expressed in the majority of human breast cancers, and therapeutic IGF-IR inhibitors are being developed. Identification of the effects of PTEN loss on IGF-IR signaling and sensitivity to IGF-IR-targeted therapies will reveal novel functions of PTEN, and determine whether PTEN status is a biomarker of response to therapy. In turn, these collective findings will allow the optimization of therapies targeting the IGF-IR and PI3K pathways. The studies proposed herein will be carried out at the Vanderbilt-Ingram Cancer Center, with facilities and centers ideally suited for the molecular, genetic, proteomic, and live animal imaging analyses involved in this research. This institution also provides extensive didactic activities and career development opportunities to enhance the training of young investigators. The above studies will provide me with enhanced scientific training in an environment rich with collaborations and interdisciplinary research to promote growth and independence. My immediate career goal is the acquisition of an independent, tenure-track, assistant professor faculty position to establish my own laboratory and research team, with the long-term goal of establishing an extramurally-funded program in mechanism-based translational cancer research. PUBLIC HEALTH RELEVANCE: PTEN loss is one of the most common aberrations in human cancer. These studies will dissect the mechanism(s) by which PTEN modulates tyrosine kinase signaling and therapeutic response to anticancer agents. This information will guide the design, development, and application of targeted cancer therapies.