EXAMINATION OF UNDEFINED MOLECULAR ALTERATIONS IN GLIOMAS

肿瘤细胞致瘤能力的获得和进展 肿瘤细胞涉及基因改变，导致 癌基因和肿瘤抑制基因的功能丧失。的 该项目的累积目标是确定和描述 肿瘤抑制基因定位于4号染色体长臂， 最近发现与恶性进展有关， 人类神经胶质瘤许多分子改变以前已经被发现。 在神经胶质瘤中，虽然有其他的遗传位点， 预计会造成损坏， 是肿瘤发生所必需的。最近，我们展示了意想不到的 涉及4号染色体肿瘤抑制基因座。这是 通过微细胞介导的4号染色体转移到 神经胶质瘤细胞和杂交细胞抑制的证明 致瘤表型对照染色体转移没有表型 方面的影响.插入的4号染色体是片段化的，因此只有一小段 染色体片段保留在抑制的杂种细胞中。 该片段已被部分表征，并显示含有三个 4号染色体的区域;两个大约1-2 CM的区域和另一个 大约7-8厘米。这些区域已被分子鉴定， 已经产生了跨越所涉及区域的YAC重叠群。初始 脑胶质瘤与头颈部鳞状细胞癌的等位基因分型 癌标本，其中后者先前已报告， 涉及4号染色体的缺失， 区域显示一致的杂合性缺失（洛）。的 两种表现出一致洛缺失的人类癌症的定位， 染色体片段，以独立地识别相同的小区域， 4号染色体，为肿瘤的存在提供了强有力的证据 抑制基因为了确定责任基因，一个修改的位置， 将继续实施克隆战略。最初，该地区将 广泛分析损失或其他可能的地标， 确定包含肿瘤抑制基因的关键区域。还有， 杂合体中抑制区的可能缺失或重排 将对细胞进行功能和分子评估。孤立余弦 将利用定位到各个区域来进一步识别 关键区域和用于产生粘粒重叠群。一旦关键 区域被定义，在该区域内表达的基因序列将被 鉴定并分析受累肿瘤的变化。这 功能和分子方法的组合已经确定了一种新的 肿瘤抑制位点，并为我们提供了一种独特的方法来识别 负责任的基因

The acquisition and progression of the tumorigenic capabilities of neoplastic cells involves genetic alterations leading to the activation of oncogenes and the loss of function of tumor suppressor genes. The cumulative objective of this project is to identify and characterize a tumor suppressor gene localized to the long arm of chromosome 4 that we have recently identified to be involved in the malignant progression of human gliomas. A number of molecular alterations have previously been identified to occur in gliomas, although additional sites of genetic damage would be anticipated to account for the multiple alterations required for oncogenesis. Recently, we have demonstrated the unexpected involvement of a chromosome 4 tumor suppressive locus. This was accomplished by the microcell-mediated transfer of a chromosome 4 into a glioma cell and demonstration of a suppression of the hybrids cells tumorigenic phenotype. Control chromosomal transfers had no phenotypic effects. The inserted chromosome 4 was fragmented, thus only a small segment of the chromosome was retained in the suppressed hybrid cells. This fragment has been partially characterized and shown to contain three regions of chromosome 4; two regions of approximately 1-2 CM and another approximately 7-8 CM. These regions have been molecularly identified and YAC contigs have been generated spanning the involved regions. Initial allelotyping analyses of gliomas and head and neck squamous cell carcinomas specimens, the latter of which have previously been reported to involve deletions on chromosome 4, have implicated one of the retained regions to display consistent loss of heterozygosity (LOH). The localization of two human cancers exhibiting consistent LOH and our chromosomal fragment to independently identify the same small region of chromosome 4, provides strong evidence for the presence of a tumor suppressor gene. To identify the responsible gene, a modified positional cloning strategy will be pursued. Initially, the region will be extensively analyzed for losses or other possible landmarks that may identify the critical region containing the tumor suppressor gene. Also, the possible deletion or rearrangement of the suppressive region in hybrid cells will be functionally and molecularly assessed. Isolated cosmids localized to the various regions will be utilized to further identify the critical region and for generation of cosmid contigs. Once the critical region is defined, expressed gene sequences within the region will be identified and analyzed for alterations in involved neoplasms. This combination of functional and molecular approaches has identified a novel tumor suppressive locus and provided us with an unique means to identify the responsible gene.