PROTEIN TYROSINE KINASE GROWTH FACTOR RECEPTORS IN TUMORIGENESIS OF PNET

髓母细胞瘤是一种具有组织学特征的小脑恶性肿瘤 类似于胚芽的未分化的神经外胚层细胞 因此也被称为“原始神经外胚层 肿瘤”（PNIPs）。 费城儿童医院是一家主要的 转诊中心，用于诊断和治疗患有这些肿瘤的儿童。 虽然组织学上未分化，但大多数PNS显示 早期分化沿着 神经元或星形胶质细胞谱系。 特别是，超过一半的小学 PNET和除一个以外的所有已建立的PNET系都表达神经丝肽， 成神经细胞的细胞骨架特征。 增殖、分化和 最终退出来源于CNS生发基质的细胞的细胞周期 并注定成为神经元是由细胞因子调节的， 蛋白酪氨酸激酶（PTK）家族的跨膜受体 信号装置. 我们计划测试的假设是， PTK受体家族成员参与人CNS的发病机制 好的 我们计划进行以下实验： 1.生长因子受体的PTK家族成员参与 原始神经上皮的神经母细胞分化将是 通过两种方法鉴定：a）消减杂交和克隆 从一个人类肿瘤细胞系，可以分化成有丝分裂后的神经元， 通过用视黄酸处理;和B）探测现有的人胎儿 用抗磷酸酪氨酸单克隆抗体构建脑表达文库。 然后将建立的人PNET细胞系和原代人PNET肿瘤 检查这些PTK转录本的表达，结果将在 与正常小脑样品相比， 未成年人和成年人的尸检 2.这些PTK基因的以下遗传改变将在 CNS PNIPs：扩增、插入、缺失和点突变。 每个 可能导致显性表型，其中神经母细胞分化 和生长控制受到干扰，从而导致 中枢神经系统 PTK受体基因变异的生物学意义 将通过以下方式评估在PNIPs中检测到的：a）确定其 在已建立的CNS PNET细胞系和原代PNET中的发生频率 肿瘤标本;和B）通过以下方法检查它们的功能结果： 使用小鼠3 T3细胞和胚胎干细胞的培养物的转染测定 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.