The effects of PTEN on tyrosine kinase signaling in breast cancer

描述(申请人提供)：这些研究的目的是了解肿瘤抑制基因磷酸酶和10号染色体上缺失的Tensin同源基因(PTEN)的缺失在乳腺癌中的作用，以及PTEN功能对酪氨酸激酶信号转导的影响。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，最常见的原因是PTEN基因的表达缺失或功能缺失。PTEN作为PI3K下游的一种脂磷酸酶，可拮抗PI3K信号转导，但PTEN蛋白磷酸酶活性对肿瘤的抑制作用仍未解决。PTEN缺失导致胰岛素样生长因子-I受体(IGF-IR)、胰岛素受体(InsR)和ErbB3/HER3等受体酪氨酸激酶(RTK)的激活，提示PTEN参与PI3K上游和下游信号的调控。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缺失使癌细胞对RTK抑制敏感。支持假说#1的结果表明，PTEN的缺失不仅增加了PI3K信号通路，而且还通过蛋白导向的通路增加了致癌信号，这些信号还有待确定。在这种情况下，抑制PI3K可能不足以阻止PTEN缺陷肿瘤的生长。支持假说2的结果将PTEN缺失作为可能受益于RTK指导治疗的患者亚群的生物标记物。为了验证这些假说，我提出了以下具体目标：1)确定PTEN缺失是否调节IGF-I、胰岛素和HER3受体信号；2)确定PTEN缺失是否对IGF-IR、InsR和HER3的治疗性抑制剂敏感；3)发现PTEN的磷蛋白底物以及PTEN蛋白磷酸酶活性对酪氨酸激酶信号的整体影响。对PTEN蛋白底物的整体分析以及PTEN缺失对酪氨酸激酶信号转导的影响将有助于确定PTEN的新功能，提供PTEN缺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都有表达，治疗性IGF-IR抑制剂正在开发中。确定PTEN缺失对IGF-IR信号的影响以及对IGF-IR靶向治疗的敏感性将揭示PTEN的新功能，并确定PTEN状态是否为治疗反应的生物标志物。反过来，这些集体发现将允许针对IGF-IR和PI3K途径的治疗的优化。这里提出的研究将在范德比尔特-英格拉姆癌症中心进行，其设施和中心非常适合于这项研究中涉及的分子、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，以加强对年轻调查人员的培训。上述研究将为我在一个充满合作和跨学科研究的环境中提供加强的科学培训，以促进成长和独立。我当前的职业目标是获得一个独立的、终身教职的助理教授职位，以建立自己的实验室和研究团队，长期目标是在基于机制的转化性癌症研究方面建立一个由外部资金资助的项目。 公共卫生相关性：PTEN缺失是人类癌症中最常见的异常之一。这些研究将剖析PTEN调节酪氨酸激酶信号转导和抗癌药物治疗反应的机制(S)。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.