Role of the Sterile20 (Ste20)-like kinase MST4 in Pituitary Tumorigenesis

描述(由申请人提供)： 脑下垂体瘤是最常见的脑肿瘤，在尸检中发现高达20%的人口，临床上发现1/10,000人。以目前美国退伍军人的数量计算，这意味着超过22.5万名退伍军人患有脑下垂体瘤。促性腺激素(或空细胞)肿瘤更常见于临床表现为勃起功能障碍、激素缺乏、头痛和视力障碍进展至失明的男性。这些肿瘤中有许多是侵袭性的和复发的。对于这些巨大的脑下垂体瘤，目前还没有可用的治疗方法，手术仍然是首选的治疗方法。垂体瘤发生的遗传和分子机制尚不清楚。我们已经积累了一个独特的库&gt；300个人类脑垂体瘤和100个正常脑垂体样本与临床数据库联系在一起。我们进行了一项联合的基因筛查，以确定拷贝数的变化，并使用微阵列进行基因组转录组分析。在一例侵袭性促性腺激素垂体瘤中检测到MST4基因扩增，MST4基因是一个不育的20-样生发中心激酶(GCK)III亚家族成员，并在所有垂体瘤中都有MST4转录和蛋白水平的升高。大量新的初步数据表明，MST4在氧化应激和低氧反应中促进增殖和生存以促进肿瘤发生的作用。在这篇修订的优点综述中，我们建议：目标1：确定MST4激酶拷贝数改变、易位或突变的频率，以作为人类垂体肿瘤发病机制的一部分。这些实验将确定MST4在人类脑下垂体瘤中的失调机制。目的：在临床前小鼠模型中，检测MST4的激活域在介导其对细胞增殖和生存的影响中的重要性，并证实或否定MST4在介导肿瘤生长中的作用。使用促性腺激素和生长激素垂体细胞系统的研究将剖析MST4的关键区域，通过读出增殖、氧化应激或缺氧反应的存活率和克隆性试验来介导肿瘤发生。结果将在临床前体外裸鼠模型中得到证实，以确认MST4在体内促进肿瘤形成的能力。目的3：鉴定具有抑制MST4活性的小分子，并建立选择性抑制MST4所必需的结构特征。已知化合物的文库筛选和电子计算机筛选将识别已知的或设计新的候选MST4激酶抑制剂，这些候选药物将在细胞和动物模型中进行测试，作为我们将MST4靶向治疗人类脑垂体肿瘤的最终目标的概念证明。这些研究将一起使用尖端的遗传和基因组方法以及机制研究来剖析MST4在人类脑下垂体肿瘤中的失调作用。这些研究将有助于揭示脑垂体瘤的病理生物学。靶向MST4激酶可能为我们的脑垂体瘤和其他MST4调节失调的恶性肿瘤患者提供新的药物治疗策略。

DESCRIPTION (provided by applicant): Pituitary tumors are the most common brain tumor, found at autopsy in up to 20% of our population and clinically in 1/10,000 persons. With the current number of US veterans, this translates into over 225,000 veterans with pituitary tumors. Gonadotrope (or null cell) tumors occur more commonly in men who present clinically with erectile dysfunction, hormone deficiencies, headaches and visual disturbances progressing to blindness. Many of these tumors are invasive and recur. There are no available medical therapies for these large pituitary tumors and surgery remains the treatment of choice. The genetic and molecular mechanisms underlying pituitary tumorigenesis are poorly understood. We have amassed a unique bank of >300 human pituitary tumor and 100 normal pituitary samples tied to a clinical database. We performed a combined genetic screen to identify copy number alternations together with genomic transcriptome profiling using microarrays. Amplification of the MST4 gene, a Sterile 20-like germinal center kinase (GCK) III subfamily member was detected in an aggressive gonadotrope pituitary tumor together with increased MST4 transcript and protein levels in all pituitary tumors. Extensive new preliminary data demonstrate the role of MST4 driving proliferation and survival in response to oxidative stress and hypoxia to promote tumorigenesis. In this revised Merit Review we propose: Aim 1: To determine the frequency of altered copy number, translocation or mutation in the MST4 kinase as a mechanism contributing to human pituitary tumor pathogenesis. These experiments will define the mechanism of MST4 dysregulation in human pituitary tumors. Aim 2: To examine the importance of the kinase domain of MST4 to mediate its effects on proliferation and survival and confirm or refute the role of MST4 to mediate tumor growth in a preclinical mouse model. Studies using gonadotrope and growth hormone pituitary cells based systems will dissect the critical regions of MST4 to mediate tumorigenesis using read outs of proliferation, survival in response to oxidative stress or hypoxia and clonagenic assays. Results will be confirmed in a preclinical ex vivo nude mouse model to confirm the ability to MST4 to promote tumorigenesis in vivo. Aim 3: To identify small molecules with the capacity to inhibit MST4 activity and establish the structural characteristics necessary for selective MST4 inhibition. Library screening of known compounds together with in silico computer screening will identify known or design new candidate MST4 kinase inhibitors that will be tested in the cell and animal models as proof of concept for our ultimate goal of targeting MST4 in human pituitary tumors. Together these studies will use cutting edge genetic and genomic approaches together with mechanistic studies to dissect the role of dysregulation of MST4 in human pituitary tumors. These studies will shed light into the pathobiology of pituitary tumors. Targeting of the MST4 kinase may provide novel medical treatment strategies for our patients with pituitary tumors and other malignancies where MST4 is dysregulated.