INFLUE HETEROCYCLIC AMINE METABOLIC POLYMORPH ON BIOACTIVAT PHIP IN HUMAN COLON

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 本研究的主要目的是通过证明NAT2和CYPIA2表型以及GSTM1和CYPIA1基因型与摄入14C-PhIP的人体内形成的PhIP-DNA加合物水平相关，从而证实PhIP代谢在结肠癌中的作用。这些因素对研究很重要，因为它们代表的酶被认为是基于啮齿动物研究的PhIP代谢中的重要酶。这项工作的结果将是进一步的证据，证明杂环胺，如PhIP，与结肠癌有关，因为这些酶在杂环胺的代谢中很活跃。此外，这项工作将表明，基因或表型是否是结肠癌PHIP易感性的潜在有用标记物。 我们收集了人类的数据，通过确定NAT2和CYPIA2表型之间的关系，以及GSTM1和CYPIA1基因和人类形成的PhIP-DNA加合物水平的关系，来确定PhIP代谢在结肠癌中的作用。这是通过给被诊断为结肠癌并计划接受手术的人类受试者注射非常低水平的14C标记的PhIP来实现的。到目前为止，来自10名受试者的数据表明，sult、Nat2和CYP1A2表型影响结肠中的加合物水平。计划进行一项更大规模、更具统计学意义的研究来验证这一发现。 有必要对乳腺癌、前列腺癌和肺癌等其他癌症进行类似的研究。在这些地区，疾病造成的死亡人数都很大，预防策略受到疾病病因和代谢途径领域知识匮乏的限制，暴露信息也不完整。 研究总结和结果： 在环境中接触致癌物的最重要来源之一是通过饮食。流行病学证据表明，饮食中暴露于杂环胺(HAS)是结肠癌发生的重要危险因素。熟透的熟肉含有大量的氟化氢，已被证明会在实验动物中引起癌症。为了更好地了解羟基磷灰石的生物活化机制和潜在的诱发肿瘤的机制，我们用质量最丰富的羟基磷灰石(2-amino-1-methyl-6-phenylimidazo[4，5-b]pyridine，PhIP)来评估PhIP代谢与DNA加合物形成的关系。10名人类志愿者，在切除结肠肿瘤手术前48-72小时给予饮食相关剂量的14C-PhIP(70-84？g)。给药后24 h收集尿液进行代谢物分析，从结肠组织中提取DNA，用加速器质谱仪分析DNA加合物。所有10名受试者还进行了CYP1A2、NAT2和SULT1A1酶活性的表型分析。在尿样中检测到与PhIP有关的12个放射性峰。在所有10名志愿者中，最丰富的代谢物被鉴定为N-羟基-PhIP-N-葡萄糖醛酸苷。观察到志愿者之间代谢物水平的差异。10名志愿者均检测到结肠DNA加合物。个体之间的DNA加合物水平存在明显的个体差异。数据分析表明，尿中N-羟基-PhIP-N-2-葡萄糖醛酸苷水平高的个体，以及被归类为具有快速CYP1A2表型的个体，其结肠PhIP-DNA加合物水平最低。 意义：这些数据表明，葡萄糖醛酸化在N-羟基-PhIP的解毒中起着重要的作用。统计分析表明，尿N-羟基-PhIP-N-葡萄糖醛酸苷水平与结肠DNA加合物水平呈负相关。虽然很难从一个小的数据集中得出明确的结论，但这项初步研究的结果鼓励了使用一个更大的研究小组进行进一步的研究。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The main objective of this research is to confirm the role of PhIP metabolism in colon cancer by demonstrating that the NAT2 and CYPIA2 phenotype, as well as GSTM1 and CYPIA1 genotype are related to the level of PhIP-DNA adducts formed in humans administered dietary relevant levels of 14C-PhIP. These factors are important to study because they represent enzymes that are thought to be important in PhIP metabolism based on rodent studies. The outcome of this work will be additional proof that heterocyclic amines such as PhIP are involved in colon cancer since these enzymes are active in the metabolism of heterocyclic amines. Additionally, this work will show whether genotype or phenotype are potentially useful markers of PhIP susceptibility for colon cancer. We have collected data in humans to establish the role of PhIP metabolism in colon cancer by determining the relationship between NAT2 and CYPIA2 phenotype, as well as GSTM1 and CYPIA1 genotype and the level of PhIP-DNA adducts formed in humans. This was accomplished by administering very low levels of 14C-labeled PhIP to human subjects with a diagnosis of colon cancer who are scheduled for surgery. Data so far from 10 subjects indicates that SULT, NAT2 and CYP1A2 phenotypes influence adduct levels in the colon. A larger, more statistically significant, study is planned to verify the findings. There is a need to perform similar work in other cancers such as breast cancer, prostate cancer and lung cancer. In each of these areas, the disease toll is great, the prevention strategies are limited by a knowledge deficit in the areas of disease etiology and metabolism pathway and exposure information is incomplete. Study summary and results: One of the most significant sources of environmental exposures to carcinogens is through the diet. Epidemiologic evidence indicates that exposure to heterocyclic amines (HAs) in the diet is an important risk factor for the development of colon cancer. Well-done cooked meats contain significant levels of HAs which have been shown to cause cancer in laboratory animals. To better understand the mechanisms of HA bioactivation and potential tumor induction in humans, the most mass abundant HA, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), was used to assess the relationship between PhIP metabolism and DNA adduct formation. Ten human volunteers where administered a dietary relevant dose of 14C-PhIP (70-84 ¿g) 48-72 h prior to surgery to remove colon tumors. Urine was collected for 24 h after dosing for metabolite analysis, and DNA was extracted from colon tissue and analyzed by accelerator mass spectrometry for DNA adducts. All ten subjects were also phenotyped for CYP1A2, NAT2, and SULT1A1 enzyme activity. Twelve radioactive peaks associated with PhIP were detected in the urine samples. The most abundant metabolite in all ten volunteers was identified as N-hydroxy-PhIP-N2-glucuronide. Variation in the levels of metabolites between volunteers was observed. Colon DNA adducts were detected in all ten volunteers. Interindividual differences were evident in the levels of DNA adducts between each individual. Analysis of the data showed that individuals with high levels of urinary N-hydroxy-PhIP-N2-glucuronide, and that were categorized as having a rapid CYP1A2 phenotype had the lowest level of colon PhIP-DNA adducts. Significance: These data suggest that glucuronidation plays a significant role in detoxifying N-hydroxy-PhIP. Statistical analyses showed that levels of urinary N-hydroxy-PhIP-N2-glucuronide were negatively correlated to colon DNA adduct levels. Although it is difficult to make definite conclusions from a small data set, the results from this pilot study have encouraged further investigations using a much larger study group.