Targeting the Rac1 signaling pathway in malignant melanoma

项目总结/摘要 测序技术的最新进展有助于揭示恶性肿瘤中各种新的驱动突变。 黑色素瘤，包括最近发现的激活突变的基因编码的鸟嘌呤核苷酸 交换因子PREX 2及其小的GTP酶底物RAC 1。RAC 1中的激活突变具有特殊的 这是令人感兴趣的，因为携带该突变的肿瘤对当前靶向治疗剂是难治的。 在相当一部分人黑色素瘤中存在激活性PREX 2和RAC 1突变，这表明 这种肿瘤可能容易受到靶向其关键激酶效应子的小分子抑制剂的影响， A组p21激活激酶（PAK 1、-2和-3）和磷脂酰肌醇-3激酶，特别是PI 3 K β。在 初步研究，我们已经确定，A组PAKs是至关重要的致癌信号的RAC 1在一个新的研究领域。 斑马鱼模型和RAC 1突变的人黑色素瘤细胞中。这些影响构成了具体目标1的基础， 其中我们使用一种新的信号分析方法来确定RAC 1，BRAF， 和NRAS突变黑素细胞。在目标2中，我们将测试特定的PAK和PI 3 K小分子抑制剂， 它们阻断RAC 1的作用、生长和存活作用的能力，以及确定药物治疗的可能途径的能力， 通过测定药物治疗前后激酶组的活性来确定耐药性。第三个目标，我们将 评估用于临床前研究的新的RAC 1突变型黑色素瘤基因工程小鼠模型。 这样的模型将提供临床相关的系统来研究成黑素细胞发育中的RAC 1信号传导， 以及评估黑色素瘤治疗剂的快速测试平台。

PROJECT SUMMARY/ABSTRACT Recent advances in sequencing technology have helped uncover a variety of new driver mutations in malignant melanoma, including recent discoveries of activating mutations in the genes encoding the guanine-nucleotide exchange factor PREX2 and its small GTPase substrate, RAC1. Activating mutations in RAC1 are of special interest, as tumors bearing this mutation are refractory towards current targeted therapeutic agents. The presence of activating PREX2 and RAC1 mutations in a significant fraction of human melanoma suggest that such tumors could be vulnerable to small molecule inhibitors that target its key kinase effectors, such as Group A p21-activated kinases (PAK1, -2, and -3), and phosphatidylinositol-3 kinases, in particular PI3Kβ. In preliminary studies, we have established that Group A PAKs are critical for oncogenic signaling by RAC1 in a zebrafish model and in RAC1-mutant human melanoma cells. These effects form the basis for Specific Aim 1, in which we use a new method for signaling analysis to establish the activity of the entire kinome in RAC1, BRAF, and NRAS-mutant melanocytes. In Aim 2, we will then test specific PAK and PI3K small molecule inhibitors for their ability to block the effects growth and survival effects of RAC1, as well as determine likely pathways of drug resistance by determining the activity of the kinome before and after drug treatment. In the third aim, we will evaluate a new genetically-engineered mouse model of RAC1-mutant melanoma for use in preclinical studies. Such a model will provide a clinically relevant system to study RAC1 signaling in melanoblast development as well as a rapid testing platform to evaluate therapeutic agents in melanoma.