Blockade of p53 and Aurora A in Therapy Resistant Neuroblastoma

描述(申请人提供)：神经母细胞瘤是一种起源于神经脊部的肿瘤，是儿童最常见的颅外实体肿瘤。MYCN是MYC家族的个体发育基因，在约25%的神经母细胞瘤中发生扩增，是高危疾病的标志。神经母细胞瘤在实体瘤中是独一无二的，因为所有患者对最初的化疗都有反应。因此，风险与复发有关，复发通常是耐药的。造成这种耐药性的原因是，很大一部分复发肿瘤有治疗诱导的P53途径基因突变，在最初出现时并不明显。与人类疾病类似，神经母细胞瘤的TH-MYCN小鼠模型对化疗有反应。为了提供化疗耐药、复发疾病的小鼠模型，我们将TH-MYCN小鼠与p53ER基因敲除的小鼠杂交，这些小鼠在基线水平缺乏P53。暴露于羟基他莫昔芬可以快速和可逆地恢复P53。由此产生的神经母细胞瘤在基线时表现为外显率增加和潜伏期缩短。当p53基因恢复后，小鼠的存活率最初会有所改善，随后又会复发。在目标1中，我将描述肿瘤如何逃避P53的重新激活来使能。然后，我将描述P53在化疗抵抗现有的常规和靶向治疗中的重要性，为新的治疗药物的临床前开发建立基线，包括在AIM 2中产生的那些。神经母细胞瘤中MYCN蛋白的稳定性受到通过PI3K/mTOR途径的上游信号以及Aurora A蛋白的不依赖于激酶的支架功能的严格调控。在目标2中，我将描述一类新的Aurora A激酶的II型抑制剂，该抑制剂专为改变Aurora A的二级结构而设计，并破坏MYCN的激酶非依赖性稳定。在初步研究中，我已经确定了可以显著减少神经母细胞瘤细胞中MYCN蛋白的候选抑制剂，而且这种作用似乎是通过所提出的不稳定机制来实现的。我将完成构效关系研究，以进一步提炼这些候选化合物。成功的完成将带来耐化疗的神经母细胞瘤的改进模型以及一类新的靶向Aurora A抑制剂，预计将对神经母细胞瘤具有高度的效力和特异性。

DESCRIPTION (provided by applicant): Neuroblastoma, a tumor of neural crest origin, is the most common extra-cranial solid tumor of childhood. Amplification of MYCN, a MYC family ontogeny, occurs in ~25% of neuroblastoma and marks high-risk disease. Neuroblastoma is unique among solid tumors in that all patients typically respond to initial chemotherapy. Risk is thus associated with relapse, which is typically therapy-resistant. Contributing to this resistance a large proportion of relapsed tumors have therapy-induced mutations in p53 pathway genes, not evident at initial presentation. Mirroring human disease, the TH-MYCN mouse model of neuroblastoma is responsive to chemotherapy. In order to provide a mouse model of chemotherapy resistant, relapsed disease, we have crossed TH-MYCN mice to mice knocked-in for p53ER, which are p53 deficient at baseline. Exposure to hydroxytamoxifen allows rapid and reversible p53 restoration. Resulting neuroblastoma tumors show increased penetrance and decreased latency at baseline. When p53 is restored, mice show initially improved survival followed by relapse. In Aim 1, I will characterize how tumors evade reactivation of p53 to enable. I will then characterize the importance of p53 in chemotherapy resistance to existent conventional and targeted therapies, establishing a baseline for pre-clinical development of novel therapeutic agents, including those generated in Aim 2. The stability of MYCN protein in neuroblastoma is tightly regulated by upstream signaling through the PI3K/mTOR pathway as well as by a kinase-independent scaffolding function of the Aurora A protein. In Aim 2, I will characterize a novel class of Type II inhibitors of Aurora A kinase designed specifically to alter the secondary structure of Aurora A and disrupt the kinase-independent stabilization of MYCN. In pilot studies I have identified candidate inhibitors that dramatically decrease MYCN protein in neuroblastoma cells and that appear to do so by the destabilization mechanism proposed. I will complete structure activity relationship studies to further refine these candidate compounds. Successful completion will result in both an improved model of chemo-resistant neuroblastoma as well as a new class of targeted Aurora A inhibitors, predicted to be both highly potent and specific against neuroblastoma.