ONCOGENES, SUPPRESSOR GENES, AND MOLECULAR DOSIMETRY

癌基因、抑制基因和分子剂量测定

基本信息

批准号：
6106186
负责人：
GEORGE S BAILEY
金额：
$ 23.69万
依托单位：
OREGON STATE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
1998
资助国家：
美国
起止时间：
1998-05-01 至 2000-04-30
项目状态：
已结题

项目摘要

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.

虹鳟鱼是一种有用的低等脊椎动物模型，可用于比较人类环境致癌的问题和适当的替代物来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，遗传水生生物中伴随癌症发展的事件并不顺利明白了。该提案的重点是表征分子鳟鱼 Ki-Ras 原癌基因激活的细胞基础肿瘤及其与致癌剂剂量、DNA 加合物水平的相互作用，细胞增殖和靶器官毒性降至 0.1% 肿瘤发生率比之前的任何动物研究都要低一个数量级。我们还建议对 p53 抑制基因显性进行有限检查多倍体动物肿瘤发生过程中的突变，研究未发现哺乳动物模型是可行的。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因致癌剂剂量（见目标 3）或诱发肿瘤的肿瘤促进剂而改变再生增殖。 2. 检验选择性的假设突变型 ras p21 蛋白在不同时期的功能失调适应性差异克隆扩增和进展，而不仅仅是位点特异性速率致癌物-DNA 加合和引发过程中的诱变，确定在末期检测到的 Ki-ras 突变等位基因的最终谱肿瘤。 3. 建立Ki-ras之间的分子剂量学关系活化和致癌剂量、DNA 加合、细胞增殖和两项 ED0.1% 肿瘤研究中的肿瘤反应 - 通过适当的机制研究探索了四个假设：1）任何非线性都可以得到解释通过剂量依赖性毒性、DNA 加合或持久性； 2）那个基- ras致癌作用随着致癌物诱导毒性的增加而减少和增殖再生； 3）DMBA体内肿瘤发生可能主要由一个电子氧化产生的不稳定加合物驱动，而不是稳定的加合物； 4) DEN剂量测定和Ki-ras突变体等位基因谱取决于宿主切除修复能力，而不是仅烷基转移酶修复。 4. 检验以下假设：抑制基因的基因剂量增加是导致三倍体中大多数肿瘤表型的发展抵抗力增强鳟鱼。具体来说，我们假设那些少数肿瘤确实三倍体的发育是在选择性的环境中发育的显性转化 p53 点突变，因此将显示出更多突变型 p53 的患病率高于二倍体兄弟姐妹的肿瘤患病率。