Targeting the Kinome in Neurofibromatosis type 1

描述（由申请人提供）：1型神经纤维瘤病（NF 1）是一种常见的遗传性疾病综合征，由NF 1基因的种系突变引起。大约三分之一的NF 1患者发展为弥漫性丛状神经纤维瘤，可以转化为恶性外周神经鞘瘤-一种经常致命的癌症。值得注意的是，在人类肿瘤和NF 1小鼠模型中，神经纤维瘤几乎总是含有NF 1-null雪旺细胞和NF 1-杂合肥大细胞。移植这种NF 1易感小鼠与野生型骨髓防止肿瘤发生，这意味着杂合骨髓衍生的细胞，如肥大细胞是一个必要的组成部分的发病机制，并在施旺细胞或肥大细胞中的靶向信号通路可能是治疗的好处。NF 1基因编码一种称为神经纤维蛋白的大蛋白，具有针对Ras的GTP酶激活蛋白（GAP）活性。NF 1基因的完全或半合子缺失导致雪旺细胞和肥大细胞中K-ras活性增加，伴随着下游效应物的激活，其促进细胞增殖和形状和运动的变化。最近，我们已经表明，p21激活激酶（Paks）在K-ras信号转导中起着至关重要的作用，特别是在激活te Erk和Akt通路中。随着临床级小分子Pak抑制剂最近出现，我们提出的实验与NF 1综合征的治疗应用有直接联系，也许还可以用于由获得性体细胞NF 1突变驱动的其他癌症。此外，我们使用了一种新的磷酸化蛋白质组学方法来分析NF 1缺陷细胞中数百种蛋白激酶的活性，证实了已知的K-ras激活的信号传导活性（例如，升高 Pak，Erk和Akt/mTOR通路的活性），而且还发现了靶向治疗的新的潜在候选者。在这个建议中，我们假设，Paks，这是所需的Erk和Akt/mTOR通路激活下游的K-ras，是唯一适合作为治疗的目标，在NF 1驱动的丛状神经纤维瘤和恶性外周神经鞘肿瘤。此外，我们认为，如果出现抗Pak药物的耐药性，全激酶组分析可用于确定可能的“逃逸”途径，从而实现更有效的组合治疗。因此我们 提出三个目标：1）我们将确定NF 1-/-雪旺细胞和肥大细胞中激酶组的基线状态，以及在Mek、Akt/mTOR或Pak抑制的压力下激酶组如何重编程; 2）我们将使用NF 1和Pak的小鼠模型来确定Pak在NF 1相关肿瘤中功能的细胞基础;和3）我们将确定特异性小分子Pak抑制剂在NF 1小鼠模型和异种移植物中的功效，并评估这些药剂在体内引发的信号传导应答。

DESCRIPTION (provided by applicant): Neurofibromatosis type 1 (NF1) is a common inherited disease syndrome caused by germline mutations in the NF1 gene. About one third of NF1 patients develop diffuse, plexiform neurofibromas that can transform to malignant peripheral nerve sheath tumors - a cancer that is frequently fatal. Remarkably, in human tumors and in mouse models of NF1, neurofibromas almost invariably contain NF1-null Schwann cells and NF1-heterozygous mast cells. Transplanting such NF1-prone mice with wild-type bone marrow prevents tumorigenesis, implying that heterozygous bone marrow-derived cells such as mast cells are a required component in pathogenesis, and that targeting signaling pathways in either Schwann cells or in mast cells might be of therapeutic benefit. The NF1 gene encodes a large protein, termed Neurofibromin, with GTPase Activating Protein (GAP) activity towards Ras. Complete or hemizygous loss of the NF1 gene leads to increased K-ras activity in both Schwann cells and mast cells, with concomitant activation of downstream effectors that promote proliferation and changes in cell shape and movement. Recently, we have shown that p21-activated kinases (Paks) play a vital role in K-ras signaling, in particular in the activation of te Erk and Akt pathways. As clinical-grade small molecules Pak inhibitors have recently emerged, there is a direct line from our proposed experiments to therapeutic application in NF1 syndrome, and perhaps also in other cancers driven by acquired, somatic NF1 mutations. In addition, we have used a new phospho-proteomic method to analyze the activity of hundreds of protein kinases in NF1-deficient cells, confirming known K-ras-activated signaling activity (e.g., elevated activity of Pak, Erk, and Akt/mTOR pathways) but also uncovering new potential candidates for targeted therapy. In this proposal, we postulate that Paks, which are required both for Erk and Akt/mTOR pathway activation downstream of K-ras, are uniquely suited as targets for therapy in NF1-driven plexiform neurofibromas and malignant peripheral nerve sheath tumors. Further, we posit that, should resistance emerge to anti-Pak agents, whole kinome analysis can be used to identify likely "escape" routes, allowing for more effective combinatorial therapy. Accordingly, we propose three aims: 1) We will determine the baseline status of the kinome in NF1-/- Schwann cells and mast cells, and how the kinome reprograms under pressure of Mek, Akt/mTOR, or Pak inhibition; 2) We will use mouse models of NF1 and Pak to determine the cellular basis for Pak's function in NF1-related tumors; and 3) We will determine the efficacy of specific small molecule Pak inhibitors in NF1 mouse models and xenografts, and assess the signaling responses elicited by such agents in vivo.