The Role of p21-Activated Kinases in Malignant Mesothelioma

描述(申请人提供)：恶性间皮瘤(MM)是一种相对常见的，进展迅速的和治疗耐药的恶性肿瘤，与暴露于石棉有关。人类和小鼠MM模型都显示出NF2基因的频繁丢失，NF2基因在NF2-/-MM细胞中的重新表达减缓了它们的增殖并抑制了它们的运动，这意味着NF2在MM中起到了因果作用。NF2基因的蛋白产物Merlin结合并抑制p21激活的蛋白激酶(PAK)，这种酶积极地调节细胞周期的进展、存活和运动。来自我们实验室的最新证据有力地表明，在缺乏NF2基因的细胞中转化需要PAK。我们提出了两个目标：1)利用药理学和遗传学手段，我们将在MM细胞中建立受PAK影响的信号通路，并确定在这些细胞中影响细胞存活的PAK的关键底物；2)我们将Nf2f/f；Ink4a/ARff/f小鼠与胸腔内注射腺病毒Cre后发展为MM的Nf2f/f；Ink4a/ARff/f小鼠，与有条件地表达特定Pak抑制物的转基因小鼠杂交。这项实验将使我们能够确定PAK功能的丧失是否影响MM的发生和/或进展，以及建立体内介导这一影响的信号通路。拟议的研究不仅将增加我们对主要信号通路的了解，还可能建立PAK作为治疗这种原本无法治愈的疾病的合适靶点。

DESCRIPTION (provided by applicant): Malignant Mesothelioma (MM) is a relatively common, rapidly progressive and treatment-resistant malignancy that is associated with exposure to asbestos. Both human patients and mouse models of MM show frequent loss of the neurofibromatosis type II (NF2) gene, and re-expression of NF2 cDNA in Nf2-/- MM cells slows their proliferation and restrains their motility, implying that NF2 plays a causal role in MM. The protein product of the NF2 gene, Merlin, binds to and inhibits p21-activated protein kinases (Paks), enzymes that positively regulate cell cycle progression, survival, and motility. Recent evidence from our laboratories strongly suggests that Pak is required for transformation in cells lacking the NF2 gene. We postulate that loss of Pak function will lead to diminished activation of key Merlin effector pathways in NF2-deficient MM cells as well, and thus could benefit patients with MM. We propose two aims: 1) Using pharmacologic and genetic means to disable Pak function, we will establish the signaling pathways affected by Pak in MM cells, and also identify the key substrates of Paks in these cells that affect cell survival; 2) We will cross Nf2f/f; Ink4a/Arff/f mice, which develop MM upon intrapleural injection of Adeno-Cre, with a transgenic mouse that conditionally expresses a specific Pak inhibitor. This experiment will allow us to determine if loss of Pak function affects MM incidence and/or progression, as well as establish the in vivo signaling pathways that mediate this effect. The proposed studies will not only increase our understanding of cardinal signaling pathways, but could establish Paks as suitable targets for therapeutic intervention in this otherwise untreatable disease.