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号染色体上缺失的肿瘤抑制因子磷酸酶和张力蛋白同源物（PTEN）缺失的影响，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（PI 3 K）通路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PI 3 K下游的脂质磷酸酶来拮抗PI 3 K信号传导，但PTEN蛋白磷酸酶活性具有肿瘤抑制作用，其仍未得到解决。PTEN缺陷导致受体酪氨酸激酶（RTK）的活化，包括胰岛素样生长因子-I受体（IGF-IR）、胰岛素受体（InsR）和ErbB 3/HER 3，暗示PTEN参与PI 3 K上游和下游的信号传导的调节。因此，我假设1）PTEN蛋白磷酸酶活性的肿瘤抑制作用涉及癌蛋白（包括RTK）的直接去磷酸化，2）PTEN缺失使癌细胞对RTK抑制敏感。支持假设#1的结果表明，PTEN的缺失不仅增加了PI 3 K途径信号传导，而且还增加了通过蛋白质介导的途径的致癌信号传导，这些途径仍有待确定。在这种情况下，PI 3 K抑制可能不足以阻断PTEN缺陷型肿瘤的生长。支持假设#2的结果将提供PTEN缺失作为可能受益于RTK定向治疗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-I、胰岛素和HER 3受体信号传导; 2）确定PTEN的缺失是否对IGF-IR、InsR和HER 3的治疗性抑制剂敏感; 3）发现PTEN的磷蛋白底物和PTEN蛋白磷酸酶活性对酪氨酸激酶信号传导的总体影响。全球分析的PTEN蛋白底物和酪氨酸激酶信号的影响，PTEN的损失将确定新的作用的PTEN，提供候选磷蛋白改变的PTEN损失，并揭示信号通路之间的新的连接。IGF-IR在大多数人乳腺癌中表达，治疗性IGF-IR抑制剂正在开发中。鉴定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靶向IGF-IR和PI 3 K通路的疗法。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，以加强对年轻调查员的培训。上述研究将为我提供一个丰富的合作和跨学科研究的环境中增强科学训练，以促进成长和独立。我的近期职业目标是获得一个独立的，终身制的助理教授职位，建立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转化癌症研究的校外资助计划。 公共卫生相关性：PTEN缺失是人类癌症中最常见的畸变之一。这些研究将剖析PTEN调节酪氨酸激酶信号传导和对抗癌剂的治疗反应的机制。这些信息将指导靶向癌症治疗的设计，开发和应用。

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.