ONCOGENES, SUPPRESSOR GENES, AND MOLECULAR DOSIMETRY

虹鳟鱼是一种有用的低等脊椎动物模型， 人类环境致癌作用的问题和适当的 替代研究肿瘤发展的分子基础， 受污染水道中的野生鱼类种群。 然而，基因 在水生物种中伴随癌症发展的事件并不好 明白 该提案的重点是表征分子 鳟鱼Ki-Ras原癌基因激活的细胞学基础 肿瘤形成，及其与致癌物剂量，DNA加合物水平， 细胞增殖和靶器官毒性降至0.1%肿瘤 发病率，一个数量级低于任何以前的动物研究。 我们还提出了一个有限的检查p53抑制基因显性 多倍体动物肿瘤发生过程中的突变，研究没有 在哺乳动物模型中可行。 具体目标是：1。建立 控制突变频率和类型的基本参数 各种鳟鱼肿瘤表型中的Ki-ras等位基因。 检查 假设ras和非ras肿瘤发生途径的平衡是 通过致癌物剂量（见目标3）或肿瘤促进剂改变， 再生增殖 2.检验选择性的假设 突变型ras p21蛋白功能失调适应性的差异 克隆扩张和进展，而不仅仅是位点特异性速率 致癌物-DNA加合和诱变过程中启动，确定 在终末期检测到的Ki-ras突变等位基因的最终谱 肿瘤的 3.建立Ki-ras之间的分子剂量学关系 激活和致癌物剂量，DNA加合，细胞增殖和 两项ED 0.1%肿瘤研究中的肿瘤缓解-通过适当的机制 研究探索了四个假设：1）任何非线性都可以解释 通过剂量依赖性毒性，DNA内收，或持久性; 2）Ki- ras肿瘤发生随致癌物诱导毒性的增加而减少 和增殖再生; 3）DMBA在体内的肿瘤发生可能 主要由来自一个电子氧化的不稳定加合物驱动， 而不是稳定的加合物; 4）DEN剂量学和Ki-ras突变体 等位基因谱依赖于宿主的切除修复能力，而不是 仅仅是烷基转移酶修复。 4.检验假设， 抑制基因的基因剂量增加， 在三倍体中对大多数肿瘤表型发展的抗性增加 鳟鱼。 具体地说，我们假设那些少数肿瘤， 在三倍体中发展，在选择性环境中发展， 主要转化p53点突变，因此将显示出许多 突变型p53的患病率高于二倍体同胞的肿瘤。

The rainbow trout is a useful lower vertebrate model for comparative issues in human environmental carcinogenesis and an appropriate surrogate to investigate the molecular basis for tumor development by feral fish populations in contaminated waterways. However, the genetic events accompanying cancer development in aquatic species are not well understood. The focus of this proposal is to characterize the molecular and cellular basis for Ki-Ras proto-oncogene activation in trout neoplasia, and its interactions with carcinogen dose, DNA adduct levels, cell proliferation and target organ toxicity down to 0.1% tumor incidence, an order of magnitude lower than any previous animal studies. We also propose a limited examination of p53 suppressor gene dominant mutation during tumor development in polyploid animals, studies not feasible with mammalian models. Specific Aims are: 1. Establish the fundamental parameters that govern the frequency, and types, of mutant Ki-ras alleles among various trout tumor phenotypes. Examine the hypothesis that the balance of ras and non-ras tumorigenesis pathways is altered by carcinogen doses (see Aim 3) or tumor promoters that induce regenerative proliferations. 2. Examine the hypothesis that selective differences in dysfunctional fitness of mutant ras p21 proteins during clonal expansion and progression, not solely site-specific rates of carcinogen-DNA adduction and mutagenesis during initiation, determine the eventual spectrum of Ki-ras mutant alleles detected in end-stage tumors. 3. Establish molecular dosimetry relationships between Ki-ras activation and carcinogen dose, DNA adduction, cell proliferation and tumor response in two ED0.1% tumor studies - By appropriate mechanistic studies explore four hypotheses: 1) that any non-linearity is explained by dose-dependent toxicity, DNA adduction, or persistence; 2) that Ki- ras oncogenesis decreases with increasing carcinogen-induced toxicity and proliferative regeneration; 3) that DMBA tumorigenesis in vivo may be driven primarily by unstable adducts from one electron oxidation, rather than stable adducts; 4) that DEN dosimetry and Ki-ras mutant allele spectrum is dependent on host excision repair proficiency, not solely alkyltransferase repair. 4. Examine the hypothesis that increased gene dosage for suppressor genes accounts for the greatly increased resistance to development of most tumor phenotypes in triploid trout. Specifically, we hypothesize that those few tumors that do develop in triploids have developed in an environment selective for dominantly transforming p53 point mutations, and thus will show a much greater prevalence of mutant p53 than will tumor from diploid siblings.