THE ROLE OF CLASS III PI-3 KINASE IN MTOR COMPLEX1 SIGNALING AND TUMORIGENESIS

描述（由申请人提供）：癌症已成为全球发病和死亡的主要原因，预计到2020年每年死亡人数将达到1030万。最近的流行病学研究表明，肥胖和相关的2型糖尿病的急剧增加是癌症的主要危险因素。这些观察结果刺激了识别肥胖环境下驱动肿瘤发生的分子信号通路的迫切需要，从而可以开发新的治疗方法。虽然脂肪和碳水化合物的增加通常被认为是饮食引起的代谢异常状态的主要因素，但蛋白质消耗的增加也被认为是一个潜在的因素，它通过循环支链氨基酸（BCAAs）水平的升高起作用。BCAA转运蛋白在许多癌症类型中上调，其表达的增加与恶性肿瘤的分期相关，这表明BCAA可用性的增加和BCAA内流的增强可能足以驱动肿瘤的发生。哺乳动物雷帕霉素靶点复合物1 （mTORC1）作为一个调节节点，通过整合营养和丝裂原的输入来积极控制细胞的生长和增殖。关键的是，BCAAs促进恶性肿瘤的机制似乎在机制上依赖于bcaa诱导的mTORC1信号。III类磷脂酰肌醇3oh激酶（PI3K）是一种异源二聚体，由催化亚基hVps34和调节亚基hVps15组成，介导对mTORC1的营养输入的反应。III类PI3K也是Src依赖性肿瘤发生所必需的。III类PI3K在mtorc1依赖性营养反应和肿瘤发生中的关键作用表明，靶向III类PI3K可能被证明是一种新的有效的抗癌治疗方法。该提案的长期目标是描述III类PI3K介导营养诱导的mTORC1信号传导的机制，并检查III类PI3K在促进肿瘤发生和肿瘤进展中的作用。核心假设是III类PI3K的致瘤作用是通过mTORC1信号通路表现出来的，III类PI3K是治疗干预的候选者。为了解决这一中心假设，我们将追求两个具体目标。目的1是验证III类PI3K调控亚基hVps15正调控mTOR蛋白稳定性和细胞定位的假设。目的2是验证hVps15是肿瘤发生所必需的假设。这些特定的目标将通过在细胞培养中对hVps15进行遗传操作、评估mTORC1信号和确定mTOR蛋白半衰期来实现。原位和体内肿瘤发生模型，结合rnai对hVps15的破坏和mTOR的药理抑制，将用于研究III类PI3K在肿瘤发生中的作用。

DESCRIPTION (provided by applicant): Cancer has become the leading cause of morbidity and death worldwide, with annual deaths expected to reach 10.3 million by 2020. Recent epidemiological studies have shown that a dramatic rise in obesity and the associated type 2 diabetes are major risk factors for cancer. These observations have stimulated the critical need to identify the molecular signaling pathways that drive tumorigenesis in response to the obese setting, such that novel therapies can be developed. Although increased fats and carbohydrates are commonly cited as the major factors in diet-induced dysmetabolic states, increased protein consumption has also emerged as a potential contributor, acting through elevated levels of circulating branched-chain amino acids (BCAAs). BCAA transporters are upregulated in many cancer types and their increased expression correlates with the stage of malignancy, suggesting that increased BCAA availability and enhanced BCAA influx may be sufficient to drive tumorigenesis. The mamalian target of rapamycin complex1 (mTORC1) acts as a regulatory node by integrating input from nutrients and mitogens to positively control cell growth and proliferation. Critically, the mechanism by which BCAAs promote malignancy appears to be mechanistically dependent on BCAA-induced mTORC1 signaling. Class III phosphatidylinositol-3OH kinase (PI3K), a heterodimer consisting of the catalytic subunit, hVps34, and a regulatory subunit, hVps15, mediates the response to nutrient input to mTORC1. Class III PI3K is also required for Src- dependent tumorigenesis. The key role of class III PI3K in the mTORC1-dependent nutrient response and tumorigenesis suggests that targeting class III PI3K may prove to be a novel and efficacious anti- cancer therapy. The long-term goal of this proposal is to delineate the mechanisms through which the class III PI3K mediates nutrient-induced mTORC1 signaling and to examine the role of the class III PI3K in promoting tumorigenesis and tumor progression. The central hypothesis is that the tumorigenic role of class III PI3K is manifested through the mTORC1 signaling pathway and that class III PI3K is a candidate for therapeutic intervention. To address this central hypothesis, two specific aims will be pursued. Aim 1 is to test the hypothesis that the class III PI3K regulatory subunit, hVps15, positively regulates mTOR protein stability and cellular localization. Aim 2 is to test the hypothesis that hVps15 is necessary for tumorigenesis. These specific aims will be achieved through genetic manipulation of hVps15 in cell culture, assessment of mTORC1 signaling, and determination of mTOR protein half-life. In situ and in vivo models of tumorigenesis, in conjunction with RNAi-based disruption of hVps15 and pharmacological inhibition of mTOR, will be used to examine the role of the class III PI3K in tumorigenesis. PUBLIC HEALTH RELEVANCE: Deaths caused by cancer are continuing to rise worldwide, and are, in large part, thought to be accompanying the escalating obesity epidemic. Excess nutrients are strong drivers of cancer. Thus, this proposal aims to understand how nutrient-regulated signals promote cancer, and to obtain a deeper understanding of the nutrient-regulated signaling pathways themselves as a first step in developing more effective cancer therapies.