Cancer-Associated, Interdependent Regulation of mTOR, AKT, and IKK/NF-kappaB

描述(申请人提供)：AKT通过(I)PTEN肿瘤抑制基因突变，(Ii)激活PI3K突变，以及(Ii)生长因子受体上调/刺激，在多种癌症中被广泛激活。Akt下游的致癌机制包括通过关键底物的磷酸化来刺激细胞的增殖和存活。例如，Akt已知可以磷酸化TSC2以上调mTOR，磷酸化和失活促凋亡的Forkhead蛋白，并激活转录因子NF-kB(它在细胞增殖和生存中发挥作用)。Akt途径的一个关键效应器是mTOR，它本身是一种在TORC1复合体中发挥作用的激酶。重要的是，Akt在几种癌症动物模型的发展和进展中是必需的，雷帕霉素抑制mTOR可以阻断Akt诱导的肿瘤生长。此外，含有Rictor蛋白的独特的mTOR复合体(TORC2)被证明是PDK2活性，它通过Ser473上的磷酸化来控制Akt的激活。阻断mTOR活性的雷帕霉素在某些癌症中显示出疗效，但在其他癌症中却失败了，这是因为失去了IRS-1和Akt激活的负反馈途径。因此，了解在癌症中可能同时控制mTOR和Akt激活的潜在调控机制是极其重要的。 我们已经发表了一种与肿瘤发生相关的核因子-kB途径的上游调节因子IKK？，它控制着PTEN缺失/非活动性前列腺癌的TORC1活性。我们团队最近发表的一篇论文表明，这种相互作用反过来导致了对核因子-kB激活的mTOR/Raptor依赖的控制，控制着抗凋亡基因的表达。此外，我们的初步数据显示，ikk？与PC3前列腺癌细胞中的TORC2复合体结合，控制Akt S473的磷酸化和激酶活性。这么说来，好吗？调节TORC1和TORC2中mTOR活性的功能，增加了ikk？抑制可以同时抑制TORC1和TORC2，绕过与雷帕霉素相关的问题及其对Akt激活的反馈控制的影响。我们建议：(I)描述ikk？控制TORC2活动，确定特定的IKK？抑制剂将阻断TORC1和TORC2的活性，(Ii)确定IKK？？抑制是否对癌细胞具有细胞毒性/细胞抑制作用，以及这是否会阻止对IRS-1/Akt的反馈控制的丧失，以及(Iii)确定IKK？？的遗传和药物抑制是否？和/或ikk？将在前列腺癌的PTEN缺失模型中阻止癌症的进展和发展。作为与人类相关的研究，将在原代人类胶质母细胞瘤外植体上进行研究。这些研究可能确定抑制癌症中mTOR和Akt活性的单一机制。这些研究也是第一次使用特定的ikk？癌症研究的抑制剂。 公共卫生相关性：Akt的解除管制与许多癌症的发病机制有关。基于此，Akt通路已经成为多种肿瘤中肿瘤发生和癌症治疗耐药的关键调节因子。AKT通过上调mTOR和不依赖mTOR的途径来促进生长和存活，其中包括控制细胞凋亡的靶分子的磷酸化。用雷帕霉素或类似物靶向mTOR在一些肿瘤中有效，但在许多其他肿瘤中无效，部分原因是失去了对IRS-1的负反馈控制，从而导致Akt激活。基于这些观察，开发同时阻断mTOR和Akt激活的抑制剂可能被证明对一些癌症有效。我们最近出版了那本书？是Akt活性癌细胞中mTOR(TORC1)的关键调节因子。此外，我们发现mTOR(TORC1)调节ikk/NF-kB活性以诱导与癌症治疗耐药相关的基因表达，这表明mTOR对雷帕霉素敏感的mTOR具有新的功能。我们现在已经展示了那个ikk？与TORC2复合体结合，调节其控制Akt活性的能力。通过实验分析了IKK？调节肿瘤细胞中的TORC2活性，并可能在生长因子诱导的信号传导的下游。我们假设抑制IKK？(使用遗传和药理学方法)将阻止依赖Akt和mTOR的癌症的进展，并将克服癌症治疗对雷帕霉素的耐药性。基于细胞和动物模型的研究被用来检验我们的假设。这项工作基于以下几点具有临床意义：(I)我们建议将PTEN f1/fl模型用于前列腺癌，该模型模拟了在包括前列腺癌在内的人类癌症中看到的PTEN基因的丢失，(Ii)这些研究可能揭示一种机制，通过抑制与TORC1被抑制时失去对IRS-1的反馈控制相关的下游影响来显著和广泛地增强雷帕霉素的疗效，(Iii)这些研究将是第一次使用高度特异性的IKK？我们分析了原代人胶质母细胞瘤外植体用于治疗和机制研究，以测试/验证我们的假设，并且(V)结果可能揭示在癌症中同时抑制TORC1活性和Akt激活的单一机制(通过TORC2)。

DESCRIPTION (provided by applicant): Akt is widely activated in a variety of cancers via (i) mutation in the PTEN tumor suppressor, (ii) activating mutations in PI3K, and (ii) through growth factor receptor upregulation/stimulation. Promotion of oncogenic mechanisms downstream of Akt involve stimulation of cellular proliferation and survival through phosphorylation of key substrates. For example, Akt is known to phosphorylate TSC2 to upregulate mTOR, to phosphorylate and inactivate pro-apoptotic Forkhead proteins, and to activate the transcription factor NF-kB (which functions in cell proliferation and survival). A key effector of the Akt pathway is mTOR, itself a kinase that functions in the TORC1 complex. Importantly, Akt is required for the development and progression of several animal models of cancer, and inhibition of mTOR with rapamycin blocks tumor growth induced by Akt. Additionally, a distinct mTOR complex (TORC2) containing the protein Rictor has been demonstrated to be the PDK2 activity that controls Akt activation via phosphorylation on ser473. Rapamycin, which blocks mTOR activity, has shown efficacy in certain cancers, but has failed in others due to a loss of a negative feedback pathway on IRS-1 and Akt activation. Thus, it is of extreme importance to understand potential regulatory mechanisms that could control both mTOR and Akt activation in cancers. We have published that IKK?, an upstream regulator of NF-kB pathway which is associated with oncogenesis, controls TORC1 activity in PTEN-null/inactive prostate cancers. A recently published paper from our group demonstrates that this interaction, reciprocally, leads to an mTOR/Raptor-dependent control of NF-kB activation controlling the expression of anti-apoptotic genes. Additionally, our preliminary data shows that IKK? associates with the TORC2 complex in PC3 prostate cancer cells to control Akt S473 phosphorylation and kinase activity. Thus, IKK? functions to regulate mTOR activity in both TORC1 and TORC2, raising the potential that IKK? inhibition could function to inhibit both TORC1 and TORC2, circumventing problems associated with rapamycin and its effects on feedback control of Akt activation. We propose to: (i) characterize mechanisms whereby IKK? controls TORC2 activity, determining if a specific IKK? inhibitor will block both TORC1 and TORC2 activity, (ii) determine if IKK??inhibition is cytotoxic/cytostatic in cancer cells and if this will block the loss of feedback control on IRS-1/Akt, and (iii) determine if genetic and pharmacologic inhibition of IKK? and/or IKK? will block progression and development of cancer in a PTEN-loss model of prostate cancer. As a human correlate, studies will be performed on primary human glioblastoma explants. The studies may identify a single mechanism to suppress mTOR and Akt activity in cancer. The studies are also the first to use a specific IKK? inhibitor for cancer studies. PUBLIC HEALTH RELEVANCE: Deregulated of Akt is implicated in the pathogenesis of a number of cancers. Based on this, the Akt pathway has emerged as a key regulator of oncogenesis and cancer therapy resistance in a variety of tumors. Akt functions to promote growth and survival through upregulation of mTOR and through mTOR-independent pathways, which include phosphorylation of targets which control apoptosis. Targeting mTOR with rapamycin, or analogs, is efficacious in some tumors but ineffective in many others due, in part, to loss of a negative feedback control on IRS-1 which then leads to Akt activation. Based on these observations, the development of inhibitors that blocks both mTOR and Akt activation may prove effective in a number of cancers. We have recently published that IKK? is a key regulator of mTOR (TORC1) in Akt-active cancer cells. Additionally, we find that mTOR (TORC1) regulates IKK/NF-kB activity to induce expression of genes associated with cancer therapy resistance, demonstrating a novel function for the rapamycin-sensitive form of mTOR. We have now shown that IKK? associates with the TORC2 complex to regulate its ability to control Akt activity. Experiments are proposed to dissect the mechanism whereby IKK? regulates TORC2 activity in cancer cells and potentially downstream of growth factor-induced signaling. We hypothesize that inhibition of IKK? (using genetic and pharmacologic approaches) will block progression of cancers that depend on Akt and mTOR and will overcome cancer therapy resistance to rapamycin. Cell-based and animal model studies are proposed to test our hypotheses. The work is clinically relevant based on the following points: (i) we propose the use of a PTEN fl/fl model for prostate cancer which mimics the loss of PTEN seen in human cancers, including prostate cancer, (ii) the studies may reveal a mechanism to significantly and broadly enhance the efficacy of rapamycin by suppressing the downstream effects associated with the loss of feedback control on IRS-1 when TORC1 is inhibited, (iii) these studies will be the first to use a highly specific IKK? inhibitor in cancer models, (iv) we analyze primary human glioblastoma explants for therapeutic and mechanistic studies to test/validate our hypotheses, and (v) the results may reveal a single mechanism to simultaneously suppress TORC1 activity and Akt activation (via TORC2) in cancer.