P21-activated kinase 1 and 2 as therapeutic targets of the NF1 microenvironment

描述（申请人提供）：p21激活激酶1和2作为NF 1微环境的治疗靶点I型神经纤维瘤病（NF 1）的特征在于由NF 1缺失的雪旺细胞和NF 1杂合基质细胞的混合物组成的神经纤维瘤。突变基质细胞和雪旺细胞之间的相互作用促进血管生成、胶原沉积和肥大细胞浸润。 以mas细胞中的c-kit信号通路为治疗靶点可能减少神经纤维蛋白的形成。nf 1杂合子肥大细胞对c-kit受体介导的迁移、增殖和向雪旺细胞的化学吸引是高度活跃的。 通过破坏肥大细胞中过度活跃的c-kit信号传导并调节肿瘤微环境，我们可以破坏NF 1和其他依赖肥大细胞的肿瘤的生长。 我们实验室的最新发现表明，Nf 1下游肥大细胞信号的增强需要p21激活激酶1（PAK 1）来增强体外和体内的迁移和增殖。 由于肥大细胞在NF 1中促进肿瘤生长，并且它们的缺失损害肿瘤进展，因此肥大细胞中的PAK 1抑制是NF 1的理想靶点，其通过设计用于抑制A组Pak家族激酶（Pak 1 -3）的小分子抑制剂进行。 我们的初步研究表明，另一种亚型PAK 2是肥大细胞中的主要亚型。 在另一种肥大细胞受体途径中，这种亚型具有与肥大细胞中PAK 1相反的表型。 Pak 2在c-kit/SCF/NF 1信号转导轴中的作用还有待研究。本研究的目的是在体外和体内鉴定Pak 2在c-kit/Nf 1信号传导中是否与Pak 1功能相反，如果是，则鉴定信号传导差异。 在Pak 2缺陷的原代肥大细胞的体外实验将测量肥大细胞迁移，粘附，增殖和MAPK信号转导，以阐明Pak 1和Pak 2之间的差异。随着针对A组Paks开发的小分子抑制剂，确定可能导致效力降低或潜在副作用的差异至关重要。利用真皮肥大细胞迁移到SCF和骨髓移植在NF 1中的体内研究将阐明Pak 2在皮肤和肿瘤微环境细胞中c-kit信号传导中的作用。 通过在易患神经纤维瘤的小鼠中用Nf 1-杂合~ Pak 1-/-或Pak 2-/-骨髓替换Nf 1野生型骨髓，我们将确定它们是否在支持肿瘤生长方面发挥相反的作用。 这项研究对于了解使用药物抑制剂同时抑制NF 1患者的多种Pak激酶的潜在副作用是必要的。

DESCRIPTION (provided by applicant): p21-activated kinase 1 and 2 as therapeutic targets of the NF1 microenvironment Neurofibromatosis Type I (NF1) is characterized by neurofibromas consisting of NF1-null schwann cells and a mixture of Nf1-heterozygous stromal cells. Cross talk between mutant stromal cells and schwann cells promotes angiogenesis, collagen deposition and mast cell infiltration. Therapeutic targeting of the c-kit signaling pathway in mas cells could potentially reduce neurofibromin formation. Nf1-heterozygous mast cells are hyperactive for c-kit receptor mediate migration, proliferation and chemoattraction to Schwann cells. By disrupting hyperactive c-kit signaling in mast cells and regulating the tumor microenvironment, we can disrupt tumor growth in NF1 and other tumors dependent on mast cells. Recent discoveries in our lab demonstrates that enhanced mast cell signaling downstream of Nf1 requires p21-activated kinase 1 (PAK1) for enhanced migration and proliferation in vitro and in vivo. Since mast cells promote tumor growth in NF1, and their deletion impairs tumor progression, PAK1 inhibition in mast cells is a desirable target for NF1 through small molecule inhibitors designed to inhibit Group A Pak family kinases (Pak1-3). Our preliminary studies show that another isoform, PAK2 is the dominant isoform in mast cells. This isoform has the opposite phenotype to PAK1 in mast cells in another mast cell receptor pathway. The role of Pak2 in c-kit/SCF/NF1 signaling axis has yet to be studied. The objective in our study is identify in vitro and in vivo if Pak2 functions opposite of Pak1 in c-kit/Nf1 signaling, and if so, identify the signaling differences. In vitro experiments on Pak2-deficient primary mast cells will measure mast cell migration, adhesion, proliferation and MAPK signaling to elucidate the differences between Pak1 and Pak2. With small molecule inhibitors being developed against Group A Paks, it is critical to identify differences that could result in reduced potency or potential side effects. In vivo studie using dermal mast cell migration to SCF and bone marrow transplantation in NF1 will elucidate the role that Pak2 plays in c-kit signaling in skin and in tumor microenvironment cells. By replacing Nf1 wildtype bone marrow with Nf1-heterozygous~Pak1-/- or Pak2-/- bone marrow in mice prone to neurofibromas, we will identify if they play opposing roles to support tumor growth. This research is necessary to understand potential side effects of inhibiting multiple Pak kinases simultaneously in NF1 patients wih drug inhibitors.