Dietary Cancer Prevention in DNA Repair Deficient Mice

描述（由申请人提供）： 我们细胞中的基因组DNA不断被破坏和修复。损伤通过暴露于环境遗传毒素（如阳光的UV组分）和与DNA反应的内源性代谢物自发发生。不修复损伤的后果是由遗传疾病揭示的，其中DNA修复途径被破坏。人类的修复缺陷会导致癌症风险的大幅增加，即使在没有明显暴露于环境遗传毒素的情况下。因此，癌症的预防是依赖于确定内源性DNA损伤的来源和手段，以避免或减弱it. Mouse模型，这些人类修复缺陷综合征提供了一个敏感的工具，用于识别这些来源。这项研究的长期目标是使用基因工程改造成DNA修复缺陷的小鼠来确定遗传毒性应激的饮食来源和预防癌症的营养干预措施。ERCC 1-XPF是一种核酸内切酶，用于DNA一条链上大块损伤的核苷酸切除修复（NER）和二价DNA链间交联（ICL）的修复。ERCC 1-XPF亚型小鼠具有非常高的实体瘤发病率，这不能归因于它们在NER中的缺陷。因此，ERCC 1-XPF缺陷小鼠的肿瘤发生可归因于其ICL修复缺陷，因此是自发ICL的结果。我们推测，在这种DNA修复缺陷模型中，ICL损伤促进自发性肿瘤是由脂质过氧化（LPO）引起的。提出的实验将通过用富含多不饱和脂肪酸的饮食挑战ERCC 1-XPF低形态小鼠来测试这一假设，所述多不饱和脂肪酸促进内源性LPO。该项目的具体目标是确定饮食中的多不饱和脂肪酸（PUFA）是否会促进癌症。膳食中的多不饱和脂肪酸被吸收到细胞膜中，特别容易被氧化，从而增加体内的脂质过氧化（LPO）。膜PUFA的LPO产生能够交联DNA的醛。我们假设LPO是导致修复缺陷小鼠肿瘤发生的自发性ICL的来源。通过给予富含PUFA的饮食将在ERCC 1-XPF低形态小鼠中诱导LPO。第二组动物将接受耗尽PUFA的等热量饮食。我们预测喂食富含PUFA饮食的动物将具有实体瘤的发病率增加和/或更早发作。这些实验的结果将表明，膳食脂肪是否会增加内源性DNA损伤的数量，以及这种损伤是否会促进肿瘤发生。同样，研究结果将揭示避免膳食PUFA是否会降低癌症风险。最后，这些实验将揭示ERCC 1-XPF亚型小鼠是否是筛选可能降低癌症风险的抗氧化剂的有用模型。

DESCRIPTION (provided by applicant): The genomic DNA in our cells is continuously damaged and repaired. The damage occurs via exposure to environmental genotoxins such as the UV component of sunlight and spontaneously due to endogenous metabolites that react with DNA. The consequences of not repairing the damage are revealed by genetic diseases in which DNA repair pathways are disrupted. Repair deficiency in humans can lead to a profound increase in the risk of cancer, even in the absence of obvious exposure to environmental genotoxins. Thus prevention of cancer is dependent upon identifying the sources of endogenous DNA damage and means to avoid or attenuate it. Mouse models of these human repair deficiency syndromes offer a sensitive tool for identifying these sources. The long term objective of this research is to use mice, genetically engineered to be deficient in DNA repair to identifying dietary sources of genotoxic stress and nutritional interventions that prevent cancer. ERCC1-XPF is an endonuclease required for nucleotide excision repair (NER) of bulky lesions on one strand of DNA and the repair of bivalent DNA interstrand crosslinks (ICL). Mice hypomorphic for ERCC1-XPF have a very high incidence of solid tumors, which cannot be attributed to their defect in NER. Thus tumorigenesis in ERCC1-XPF-deficient mice can be attributed to their defect in ICL repair, and therefore the consequence of spontaneous ICL. We hypothesize that the ICL damage that promotes spontaneous tumors in this DNA repair-deficient model is caused by lipid peroxidation (LPO). Experiments proposed will test this hypothesis by challenging the ERCC1-XPF hypomorphic mice with a diet rich in polyunsaturated fatty acids, which promote endogenous LPO. The specific aim of this project is to determine if dietary polyunsaturated fatty acids (PUFA) promote cancer. Dietary PUFA assimilate into cell membranes and are particularly vulnerable to oxidation, thus increase lipid peroxidation (LPO) in vivo. LPO of membrane PUFA produces aldehydes able to crosslink DNA. We hypothesize that LPO is a source of spontaneous ICL that contribute to tumorigenesis in the repair-deficient mice. LPO will be induced in ERCC1-XPF hypomorphic mice by administering a diet rich in PUFA. A second cohort of animals will receive an isocaloric diet depleted of PUFA. We predict that animals fed the PUFA-rich diet will have an increased incidence and/or earlier onset of solid tumors. The results from these experiments will indicate if dietary fats increase the amount of endogenous DNA damage and if this damage can promote tumorigenesis. Similarly, the results will reveal if avoiding dietary PUFA reduces cancer risk. Finally, these experiments will reveal if ERCC1-XPF hypomorphic mice are a useful model for screening anti-oxidants that may reduce cancer risk.