ONCOGENES, SUPPRESSOR GENES, AND MOLECULAR DOSIMETRY

虹鲑鱼是比较低等脊椎动物的有用模型。 人类环境致癌中的问题和适当的 通过以下途径研究肿瘤发生的分子基础 受污染的水道中的野生鱼类种群。然而，基因 伴随水生物种癌症发展的事件并不顺利 明白了。这项提议的重点是描述分子 和鲑鱼Ki-Ras原癌基因激活的细胞学基础 肿瘤及其与致癌物剂量、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，比之前的任何动物研究都低一个数量级。 我们还建议对显性p53抑制基因进行有限的检查。 多倍体动物肿瘤发育过程中的突变，研究报告 在哺乳动物模型上是可行的。具体目标是：1.建立 控制突变频率和类型的基本参数 鲑鱼肿瘤不同表型间的Ki-ras等位基因。请查看 假设ras和非ras致癌途径的平衡是 因致癌剂量(见目标3)或致癌促进剂而改变 再生性增殖。2.检验有选择性的假设 突变型ras p21蛋白功能失调适合性的差异 克隆性扩张和进展，而不仅仅是特定部位的比率 致癌物-DNA加合和启动过程中的突变，确定 终末期检测到的Ki-ras突变等位基因的最终谱 肿瘤。3.建立KI-RAS的分子剂量学关系 激活和致癌物剂量、DNA加成、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)任何非线性都可以解释 通过剂量依赖的毒性、DNA加成或持久性；2)Ki- RAS致癌率随致癌物毒性增加而降低 和增殖性再生；3)DMBA体内成瘤可能 主要由单电子氧化的不稳定加合物驱动， 而不是稳定加合物；4)嵌入剂量学和Ki-ras突变体 等位基因谱取决于宿主切除修复的熟练程度，而不是 完全是烷基转移酶修复。4.检验以下假设 抑制基因剂量的增加在很大程度上解释了 三倍体大多数肿瘤表型对发育的抵抗力增强 鲑鱼。具体地说，我们假设那些为数不多的肿瘤 三倍体的发育是在有选择性的环境中进行的 以转化为主的P53点突变，从而会表现出很大的 突变型p53的患病率高于二倍体兄弟姐妹的肿瘤患病率。

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.