Trk Expression and Inhibition in Human Neuroblastomas

描述(申请人提供)：神经母细胞瘤(NB)是一种常见的、致命的儿童实体瘤，表现出不同的临床行为，从自发的退化到无休止的进展。有证据表明，神经营养素受体的TRK家族在这种行为中起着关键作用。表达TrkA的NB在生物学上是有利的，容易自发退化或分化，而表达TrkB的肿瘤是极具侵袭性的肿瘤，通常是致命的。我们假设TrkA和TrkB之间的结构差异导致信号和基因诱导的差异，从而导致这些非常不同的临床行为。此外，Trk抑制将成为治疗这些肿瘤的有效辅助手段，具有广泛的治疗指数。目的1：我们将确定导致蛋白质结合或信号转导不同的受体结构的独特特征，从而导致TrkA和TrkB激活在人类NBS中的不同生物学效应。我们计划检测TrkA和TrkB蛋白在配体结合反应中的差异，这可能导致信号通路或信号持续时间的不同；使用突变或缺失分析来确认负责这些不同生物反应的受体结构域(S)；并分析TrkA或TrkB配体激活诱导的基因表达模式，以确定分别导致有利和不利行为的关键途径。目的2：我们将比较目前可用的和新的Trk抑制剂，以确定纳入临床试验的最佳药物。我们计划：用几家生物技术公司生产的Trk特异性酪氨酸激酶抑制剂在体内外处理表达TrkA和TrkB的NB细胞，以确定其对细胞存活、生长、分化和致瘤性的影响；使用新型Trk抑制剂与传统细胞毒剂联合治疗体内外表达Trk的NB，以确定最佳组合、剂量和方案；以及在体外和动物模型中使用Trk抑制剂联合PI3K/AKT、RAS、MAPK或mTOR的选择性下游抑制剂来治疗NBS，以确定联合使用是否比单独使用其中任何一种药物具有更强的抗肿瘤效果。目的：我们将确定Trk家族基因在原发NBS中的表达模式，并确定这种表达的临床后果。我们计划筛选805个具有代表性的原发NBs，以寻找Trk家族基因表达的模式，并确定这种表达模式在选定的患者亚群中的预测价值。我们还将使用这些信息来识别可能接受Trk靶向治疗的复发患者。这些研究的成功完成将澄清TrkA或TrkB的结构性差异，这些差异导致生物功能和临床行为的差异。我们将在动物模型中确定Trk抑制剂单独或与其他药物联合治疗NBS的疗效。最后，我们将确定Trk在原发NBs中的表达模式，以预测结果并确定Trk抑制剂治疗的候选者。Trk受体在其他儿童和成人肿瘤中也有表达，因此这些研究也将对它们产生更广泛的影响。公共卫生相关性：神经母细胞瘤是一种常见的致命儿童癌症，我们需要更有效、毒性更低的新疗法。我们的研究将为TrkA和TrkB受体在调节临床行为中的重要作用提供有价值的见解。我们还将确定纳入未来临床试验的最佳Trk抑制剂(试剂、剂量、方案)，我们还将确定哪些肿瘤表达Trk受体，以确定谁将从Trk抑制剂治疗中受益。

DESCRIPTION (provided by applicant): Neuroblastoma (NB) is a common and deadly solid tumor in children that displays heterogeneous clinical behavior, from spontaneous regression to relentless progression. Evidence suggests that the TRK family of neurotrophin receptors plays a critical role in this behavior. NBs expressing TrkA are biologically favorable and prone to spontaneous regression or differentiation, whereas, TrkB-expressing tumors are extremely aggressive and often fatal tumors. We hypothesize that structural differences between TrkA and TrkB lead to differences in signaling and gene induction that result in these very different clinical behaviors. Furthermore, Trk inhibition will be an effective adjunct to treating these tumors, with a wide therapeutic index. Aim 1: We will determine the unique features of receptor structure that result in differences in protein association or signaling, which in turn cause the different biological effects of TrkA vs. TrkB activation in human NBs. We plan to examine differences between TrkA and TrkB protein associations in response to ligand binding that may lead to differences in the signaling pathways or duration of signaling; use mutation or deletion analysis to confirm the receptor domain(s) responsible for these different biological responses; and analyze gene expression patterns induced by ligand activation of TrkA or TrkB to identify critical pathways that contribute to favorable and unfavorable behaviors, respectively. Aim 2: We will compare currently available and novel Trk inhibitors to identify the optimum agent for incorporation into clinical trials. We plan to: treat TrkA and TrkB expressing NB cells in vitro and in vivo with Trk-specific tyrosine kinase inhibitors from several biotechnology companies to determine the effects on cell survival, growth, differentiation and tumorigenicity; treat Trk-expressing NBs in vitro and in vivo with novel Trk inhibitors in combination with conventional cytotoxic agents to determine optimum combinations, dose and schedule; and treat NBs in vitro and in animal models with Trk inhibitors combined with selective downstream inhibitors of PI3K/AKT, RAS, MAPK, or mTOR to determine if the combination has a greater antitumor effect than either agent alone. Aim 3: We will determine the pattern of expression of Trk family genes in primary NBs, and determine the clinical consequences of this expression. We plan to screen 805 representative primary NBs for the pattern of Trk family gene expression, and determine the predictive value of this expression pattern in selected patient subsets. We will also use this information to identify relapsed patients who would be candidates for Trk-targeted therapy. The successful completion of these studies will clarify structural differences in TrkA or TrkB that lead to differences in biological function and clinical behavior. We will determine the efficacy of Trk inhibitor therapy, alone or combined with other agents, on NBs in animal models. Finally, we will determine the pattern of Trk expression in primary NBs to predict outcome and to identify candidates for Trk inhibitor therapy. Trk receptors are expressed in other pediatric and adult tumors, so these studies will have broader implications for them as well. PUBLIC HEALTH RELEVANCE: Neuroblastoma is a common and lethal childhood cancer, and we need novel therapies that are more effective and less toxic. Our studies will provide valuable insight into the important role of the TrkA and TrkB receptors in regulating clinical behavior. We will also determine the optimum Trk inhibitor (agent, dose, schedule) to incorporate into future clinical trials, and we will determine which tumors express Trk receptors to identify who would benefit from Trk inhibitor therapy.