Mechanisms of RET/PTC rearrangements in thyroid cancer

描述：(摘自申请者的摘要)甲状腺癌是最常见的 已知与辐射暴露有关的常见形式的实体肿瘤。 然而，辐射致癌的机制尚不清楚。 明白了。RET基因重排的高流行率一直是 最近在切尔诺贝利事件后的甲状腺乳头状癌和甲状腺中发现 来自暴露于治疗性外照射的患者的肿瘤。头寸 化学后发现的RET和ELEI基因的断裂点 具有RETPTC3重排的肿瘤提示这两个基因可能是 在DNA断裂时在细胞核中彼此对齐 (Nikiforov等人，Oncogene，1999)。与这个想法一致，我们发现 一对RET和H4基因(有助于RET/PTCI重排)是 在35%的正常甲状腺细胞间期细胞核中并列分布。这些 数据表明，两个潜在的重组染色体基因座可能是 在核中彼此毗邻，易于产生 电离产生的相邻双链DNA断裂的重排 辐射或其他遗传毒性物质。目前提案的主要目标是 探讨核结构和基因邻近性在骨质疏松症的发生中的作用 辐射后的染色体重排。我们建议使用 双色FISH和三维共聚焦激光扫描显微镜 确定基因物理接近的频率，有助于 正常人甲状腺滤泡细胞RET/PTC重排的主要类型 以及在其他细胞谱系中。我们将确定染色体组织是否 相对于这些基因座，这些基因座是细胞类型特定的、年龄相关的或随 细胞周期阶段。这些参数中的任何一个都可以部分解释这种高 照射后甲状腺癌的患病率和易感性较高 孩子们的生活。然后，我们将培养的细胞暴露在不同剂量的电离下 直接测试基因接近度和基因频率之间的关系 体外辐射诱导的RET/PTC重排频率。这些研究 将扩大我们对辐射诱导的机制的理解 甲状腺的癌变。此外，他们可能会有 在癌症中发现的广泛的染色体重排的重要性。

DESCRIPTION: (Scanned from the applicant's abstract) Thyroid cancer is the most common form of solid neoplasms known to be associated with radiation exposure. However, the mechanisms of radiation-induced carcinogenesis are not well understood. The high prevalence of rearrangements of the RET gene has been recently found in post-Chernobyl papillary thyroid carcinomas and in thyroid tumors from patients exposed to therapeutic external radiation. The positions of breakpoints sites in the RET and ELEI genes identified in post-Chemobyl tumors with RETPTC3 rearrangements suggested that these two genes may be aligned across from each other in the nucleus at the time of DNA breaks (Nikiforov et al., Oncogene, 1999). Consistent with this idea, we found that one pair of RET and H4 genes (contributing to RET/PTCI rearrangement) was juxtaposed in 35 percent of inter-phase nuclei of normal thyroid cells. These data suggest that two potentially recombinogenic chromosomal loci may be contiguous to each other in the nucleus predisposing to generation of rearrangement by adjacent double-strand DNA breaks produced by ionizing radiation or other genotoxic agents. The main goal of the current proposal is to explore the role of nuclear architecture and gene proximity in generation of chromosomal rearrangements after radiation exposure. We propose to use two-color FISH and three-dimensional confocal laser-scanning microscopy to determine the frequency of physical proximity of genes, contributing to the major types of RET/PTC rearrangements, in normal human thyroid follicular cells and in other cell lineages. We will establish whether chromosomal organization with respect to these loci is cell-type specific, age-dependent, or varies with cell cycle stage. Any of these parameters could explain in part the high prevalence of thyroid cancer after irradiation, and the higher susceptibility of children. Then, we will expose cultured cells to different doses of ionizing radiation to test directly the relationship between gene proximity and the frequency of radiation-induced RET/PTC rearrangements in vitro. These studies will extend our understanding of the mechanisms of radiation-induced carcinogenesis in the thyroid gland. In addition, they are likely to have importance for a broad range of chromosomal rearrangements found in cancer.