PROTEIN TYROSINE KINASE GROWTH FACTOR RECEPTORS IN TUMORIGENESIS OF PNET

髓母细胞瘤是具有组织学特征的恶性小脑肿瘤。 类似于生发中未分化的神经外胚层细胞 基质，也因此被称为“原始神经外胚层” 肿瘤“(PNETs)。费城儿童医院是一家 诊断和护理患有这些肿瘤的儿童的转诊中心。 尽管在组织学上没有分化，但大多数PNETs显示 早期分化的免疫化学和分子证据 神经元或星形胶质细胞谱系。特别是，超过一半的小学生 PNETs和除一个已建立的PNET线外的所有PNET线都表达神经丝肽， 神经母细胞的一种细胞骨架特征。增殖、分化和 中枢神经系统生发基质来源的细胞最终退出细胞周期 注定是神经元的是由细胞因子调节的，这些细胞因子利用成员 蛋白酪氨酸激酶(PTK)跨膜受体家族 发信号。我们计划测试的假设是，基因改变 PTK受体家族成员参与人中枢神经系统的发病 PNETs。 我们计划进行以下实验： 1.生长因子受体PTK家族成员参与 原始神经上皮细胞的神经母细胞分化 通过两种方法进行鉴定：a)消减杂交和克隆 来自可分化为有丝分裂后神经元的人类肿瘤细胞系 通过维甲酸治疗；以及b)探测现有的人类胎儿 用抗磷酸酪氨酸单抗构建脑表达文库。 已建立的人类PNET细胞系和原发的人类PNET肿瘤 检测这些PTK转录本的表达，结果将是 与正常小脑标本相比，在 未成熟和成年人类的尸检。 2.将寻求这些PTK基因的以下遗传变化 CNS PNETs：扩增、插入、缺失和点突变。每个人 可能导致神经母细胞分化的显性表型 和生长控制受到干扰，从而导致了 CNS PNETs。PTK受体基因突变的生物学意义 在PNETs中检测到的将通过以下方式进行评估：a)确定其 在已建立的CNS PNET细胞系和原代PNET中的出现频率 肿瘤标本；以及b)检查其功能后果 小鼠3T3细胞和胚胎细胞培养的转染实验 大鼠神经外胚层细胞。

Medulloblastomas are malignant cerebellar tumors with histologic features resembling those of undifferentiated neuroectodermal cells of the germinal matrix, and hence are also referred to as "primitive neuroectodermal tumors" (PNETs). The Children's Hospital of Philadelphia is a major referral center for the diagnosis and care of children with these tumors. Though histologically undifferentiated, the majority of PNETs show immunochemical and molecular evidences of early differentiation along neuronal or astroglial lineages. In particular, more than half of primary PNETs and all but one established PNET line express neurofilament peptides, a cytoskeletal feature of neuroblasts. Proliferation, differentiation, and eventual exit from the cell cycle of cells derived from CNS germinal matrix and destined to be neurons are regulated by cytokines which employ members of the protein tyrosine kinase (PTK) family of receptors for trans-membrane signalling. The hypothesis we plan to test is that genetic alterations of members of the PTK receptor family contribute to pathogenesis of human CNS PNETs. We plan the following experiments: 1. Members of the PTK family of growth factor receptors involved in neuroblastic differentiation of primitive neuroepithelium will be identified by two approaches: a) subtractive hybridization and cloning from a human tumor line that can be differentiated into postmitotic neurons by treatment with retinoic acid; and b) probing an existing human fetal brain expression library with an anti-phosphotyrosine monoclonal antibody. Established human PNET cell lines and primary human PNET tumors will then be examined for expression of these PTK transcripts, and results will be compared with those obtained with samples of normal cerebellum obtained at autopsy from immature and adult humans. 2. The following genetic alterations of these PTK genes will be sought in CNS PNETs: amplification, insertion, deletion, and point mutation. Each could lead to a dominant phenotype in which neuroblastic differentiation and growth control are perturbed, thus contributing to the pathogenesis of CNS PNETs. The biological significance of PTK receptor gene alterations detected in the PNETs will be assessed by: a) determination of their frequency of occurrence in established CNS PNET cell lines and primary PNET tumor specimens; and b) examination of their functional consequences by transfection assays employing cultures of mouse 3T3 cells and of embryonic rat neuroectodermal cells.