RAINBOW TROUT--A MODEL FOR ENVIRONMENTAL CARCINOGENESIS

本提案旨在研究虹鳟鱼的遗传毒性机制 作为一个中心主题，主要强调遗传学，分子 遗传学和致癌和肿瘤促进的生物化学。 许多 属性证明了在环境卫生中使用这种水生模型的合理性 research. 鳟鱼减少癌症研究对哺乳动物的依赖， 提供比较机制信息，显示高灵敏度 （纳克肿瘤反应），具有如此低的成本， 每个肿瘤研究的动物数量是合理的， 背景发病率，并易于操作，以产生克隆或 多倍体 强调机制将扩大我们的比较基础 用于将癌症研究从替代物外推到人类，同时 增加对野生鱼类肿瘤发展的了解。的 这四个互动项目是： 探讨 鳟鱼肿瘤发生和发展的分子基础， 包括：确定发病率的机制， Ki-ras p21等位基因型的产生和选择性增殖; 致癌物剂量、增殖再生、DNA加合 和修复能力对Ki-ras激活的发生率影响，降至10-3 肿瘤风险（ED 0.1%肿瘤研究）;以及三倍体作为 涉及显性p53点的肿瘤发生的选择性环境 突变。 2.检查肿瘤变异的遗传控制 反应远交，克隆和三倍体群体的鳟鱼。 利用 利用染色体倍性操作评估鳟鱼肿瘤抑制基因的表达 致癌作用，并建立使用RFLP标记和已知的 用抑制基因探针研究二倍体和 同基因鳟鱼的三倍体种群。 启动开发一个 虹鳟鱼的DNA标记遗传图谱。 3.建立 鳟鱼早期生命阶段对原致癌物的代谢能力 生物活化和烷基化修复。 克隆、测序并建立 三个新的鳟鱼细胞色素P450基因的表达。 建立 这些和另外两种鳟鱼的时间和组织依赖性表达 P450，它们对选定的环境因子的感应反应， 其生物活化选定的原致癌物的潜力。 建立 水平，发育表达和组织分布的06- 烷基转移酶 4.对于临床应用，建立机制 通过该方法，天然存在的化合物吲哚-3-甲醇， 目前提出用于人类干预的假定“抗癌剂” 试验，也表现为肿瘤促进剂。 调查，如果 在鳟鱼和小鼠中通过Ah受体介导促进机制 激动作用 严格量化其剂量反应性促销效力 以及潜在的促进阈值剂量， 评估推广风险与化学预防效益。

This proposal investigates mechanisms of genotoxicity in rainbow trout as a central theme, with a primary emphasis on the genetics, molecular genetics, and biochemistry of carcinogenesis and tumor promotion. Many attributes justify use of this aquatic model in environmental health research. Trout reduce dependence on mammals for cancer research, provide comparative mechanism information, show high sensitivity (nanogram tumor response), have such low cost that many thousands of animals per tumor study are reasonable, have zero and near-zero background incidence, and are readily manipulated to produce clones or polyploids. An emphasis on mechanisms will broaden our comparative base for extrapolating cancer studies from surrogates to humans, while also increasing understanding of tumor development in feral fish species. The four interactive projects within this theme are: 1. Investigate the molecular basis for tumor initiation and development in trout, including: mechanisms that determine the incidence, site-specific generation and selective propagation of Ki-ras p21 allelomorphs; the influence of carcinogen dose, proliferative regeneration, DNA adduction, and repair capacity on the incidence of Ki-ras activation, down to 10-3 tumor risk (ED0.1% tumor study); and the influence of triploid as a selective environment for oncogenesis involving dominant p53 point mutations. 2. Examine the genetic control of variation in tumor response in outbred, clonal, and triploid populations of trout. Utilize ploidy manipulation to assess tumor suppressor gene involvement in trout carcinogenesis, and establish the use of RFLP markers and known suppressor gene probes to investigate deletional events in diploid and triploid populations of isogenic trout. Initiate development of a genetic map of DNA markers for rainbow trout. 3. Establish the metabolic capacity of early trout life stages for procarcinogen bioactivation and alkylation repair. Clone, sequence, and establish the expression of three new trout cytochrome P450 genes. Establish the time- and tissue-dependent expression of these and two additional trout P450s, their inductive response to selected environmental agents, and their potential to bioactivate selected procarcinogens. Establish the levels, developmental expression, and tissue distribution of 06- alkyltransferase. 4. For clinical application, establish the mechanisms through which the naturally occurring compound indole-3-carbinol, a putative "anticarcinogen" currently proposed for human intervention trials, also behaves as a tumor promoter. Investigate if the promotional mechanism is mediated in trout and mice through Ah receptor agonism. Rigorously quantify its dose-responsive promotional potency and the potential presence of a threshold dose for promotion, in order to assess promotional risk vs. chemopreventive benefit.