NEUROTROPHIN AND TRK EXPRESSION IN MEDULLOBLASTOMA AND NEUROBLASTOMA

神经母细胞瘤是神经嵴来源的肿瘤， 酪氨酸激酶受体编码的TrkA，TrkB和TrkC， 发展这些受体与神经营养因子NGF，BDNF， 和NT-3。 我们已经证明， 神经母细胞瘤表达TrkA和TrkC，而不表达N-myc， 扩增的神经母细胞瘤表达TrkB。 在髓母细胞瘤中， TrkC的表达与更有利的结果相关。 这些研究使我们假设TrkA的激活 和/或TrkC诱导分化，导致有利的细胞分化。 结果，而TrkB的激活对生存或 不利的肿瘤生长。 支持这一概念的是研究 在神经母细胞瘤中， 神经营养素-有利的原发性肿瘤对NGF的反应， BDNF促进细胞生长/存活 线 我们的假设提出的一个重要问题是， Trk家族的不同成员促进了 分化和生长。 本提案的目标是 了解TrkB和TrkC在神经母细胞瘤中的作用， 髓母细胞瘤的发病机制，并阐明其机制， 相似的受体促进不同的结果。 具体地说， 我们将确定TrkB受体的作用， 神经母细胞瘤的信号转导通路， 表达内源性TrkB的细胞系。 康贝特人将以 信号传导中间体SHC、PI 3的激活模式 激酶和PLC-γ 1，并确定是否参与 在PC 12细胞中的分化-延长ERK的激活， SNT的磷酸化是由BDNF诱导的。 我们将确定 无论TrkB或TrkC的过表达（主要表达于 有利的肿瘤），介导分化或细胞生长。 我们 将研究TrkC受体在有利的 通过测定添加神经营养因子的作用 以及对良好的神经母细胞瘤的原代培养物的撤回。 当足够时，将检查信号转导途径 组织可用。 我们计划在 髓母细胞瘤细胞系。 我们将确定BDNF的作用 和NT-3，我们将开发单克隆抗体， 特异性识别TrkA、TrkB和TrkC， 免疫组化 这些研究的成功完成 可以提供重要的见解，选择性的影响， 激活不同的Trk家族受体。 而且我们的 结果应提供关于以下方面作用的重要信息： TrkB和TrkC在神经母细胞瘤的不同亚群中， 髓母细胞瘤和髓母细胞瘤的Trk模式 表达可能有助于预测结果并指导这些疾病的治疗 患者

Neuroblastomas are neural crest derived tumors that express tyrosine kinase receptors encoded by TrkA, TrkB, and TrkC during development. These receptors bind to the neurotrophins NGF, BDNF, and NT-3, respectively. We have shown that favorable neuroblastoma express TrkA and TrkC, while unfavorable, N-myc amplified neuroblastomas express TrkB. In medulloblastomas, high expression of TrkC is associated with more favorable outcome. These studies have lead to our hypothesis that activation of TrkA and/or TrkC induces differentiation leading to a favorable outcome, while activation of TrkB is critical to the survival or growth of unfavorable tumors. Supporting this concept are studies in neuroblastoma that show a distinct difference in response to neurotrophin addition--favorable primary tumors respond to NGF by differentiation while BDNF promotes growth/ survival in cell lines. An important question raise by our hypothesis is how do different members of the Trk family promote the opposite fates of differentiation and growth. The goals of this proposal are to understand the roles of TrkB and TrkC in neuroblastoma and medulloblastoma pathogenesis and to elucidate the mechanism by which similar receptors promote different outcomes. Specifically, we will determine the role of TrkB receptors in unfavorable neuroblastomas by examining the signal transduction pathways in cell lines expressing endogenous TrkB. We will determine the activation patterns of the signaling intermediates, SHC, PI3 kinase, and PLC-gamma1, and determine if pathways involved in differentiation in PC12 cells--prolonged activation of ERK and phosphorylation of SNT--are induced by BDNF. We will determine whether the overexpression of TrkB or TrkC (expressed primarily in favorable tumors), mediates differentiation or cell growth. We will examine the role of TrkC receptors in favorable neuroblastomas by determining the effect of neurotrophin addition and withdrawal on primary cultures of favorable neuroblastomas. Signal transduction pathways will be examined when sufficient tissue is available. We plan to conduct parallel studies in medulloblastoma cell lines. We will determine the effect of BDNF and NT-3 and we will develop monoclonal antibodies that can specifically recognize TrkA, TrkB and TrkC by immunohistochemistry. The successful completion of these studies may provide important insights into the selective effects of activating the different Trk family receptors. Furthermore, our results should provide important information about the role of TrkB and TrkC in different subsets of neuroblastomas and medulloblastomas and medulloblastomas by their pattern of Trk expression may help predict outcome and guide therapy for these patients.