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Activating liver carcinogens in yeast by expressing CYP450 polymorphisms

通过表达CYP450多态性激活酵母中的肝癌致癌物

基本信息

批准号：
8072914
负责人：
MICHAEL Thomas FASULLO
金额：
$ 1.84万
依托单位：
ORDWAY RESEARCH INSTITUTE, INC.
依托单位国家：
美国
项目类别：
财政年份：
2007
资助国家：
美国
起止时间：
2007-08-01 至 2010-08-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8072914
关键词：
Acetylation Acetyltransferase Affect Aflatoxin B1 Africa South of the Sahara Alleles Amino Acid Sequence Area Benzo(a)pyrene Biological Biological Assay Breast CHEK2 gene CYP1A1 gene CYP1A2 gene CYP3A4 gene CYP3A5 gene Carcinogens Cells Chronic Cytochrome P450 DNA Adduction DNA Adducts DNA Damage DNA Repair Gene Drug Metabolic Detoxication Early Diagnosis Enzymes Epidemiologic Studies Epoxy Compounds Exposure to Frequencies Genes Genetic Genetic Polymorphism Genetic Recombination Genome Genotype Genus Cola Goals Guide prevention HCV and Aflatoxin Hepatitis B Hepatitis B Virus Hepatitis C virus Human Individual Infection Lead Liver Malignant Neoplasms Malignant neoplasm of liver Measurement Measures Mediating Metabolic Activation Mutagens Mutation NAT2 gene Pancreas Pathogenesis Plasmids Predisposition Primary carcinoma of the liver cells Proteins Public Health Risk Risk Factors Role Saccharomyces cerevisiae Smoke Substrate Specificity System TP53 gene Testing Tobacco smoke Variant Virus Yeasts adduct aflatoxin B1-DNA adduct cancer risk expression vector genetic risk factor genotoxicity heterocyclic aromatic amines high risk response

项目摘要

DESCRIPTION (Provided by applicant): Hepatocellular carcinoma (HCC) has been correlated with specific p53 mutations and exposure to aflatoxin B1 (AFB1). Individual response to liver carcinogens shows great variability. High risk factors include chronic infection with hepatitis B (HBV) and C viruses (HCV), while additional risk factors include exposure to tobacco smoke. Cytochrome P450 genes, such as CYP1A1, CYP1A2, CYP3A4, and CYP3A5 encode proteins that activate potent liver carcinogens into genotoxic epoxides. Heterocyclic aromatic amines (HAs) require additional activation by N,O-acetyltransferase (NAT2). Specific cytochrome P450 polymorphisms and NAT2 polymorphisms contribute to risk of specific cancers, such as breast, pancreatic and colon. However, determining the risk of P450 and NAT polymorphisms in HCC is complicated by many modifying factors that can lead to detoxification of metabolites. To determine whether P450 polymorphisms per se are sufficient to increase the genotoxicity of carcinogens, we have expressed the P450 genes in Saccharomyces cerevisiae (yeast), which lacks the detoxification enzymes. We previously observed that expression of specific P450 genes in yeast is sufficient to stimulate carcinogen-associated mutation and recombination, the transcriptional induction of DNA repair genes after AFB1 exposure, and AFB1-associated activation of the checkpoint gene Rad53 (CHK2). We propose to further screen CYP1A1, CYP1A2, CYP3A4 and CYP3A5 polymorphisms that are associated with increased cancer risk. In the first specific aim, we will determine whether a subset of CYP1A1 and CYP1A2 polymorphisms affect frequencies of genetic recombination and mutation and the DNA damage response to AFB1 and liver carcinogens. In the second specific aim, we will determine whether CYP1A2 and NAT2 polymorphisms affect the metabolic activation of HAs in yeast. In the third specific aim, we will develop an expression system for CYP3A4 and CYP3A5 in yeast that will enable us to detect metabolic activation of carcinogens mediated by CYP3A3 and CYP3A5 polymorphisms. These studies will thus provide a new strategy for determining the potential risk of cytochrome P450 polymorphisms in liver cancer. Ultimately, the information will aid public health practitioners and clinicians to identify which individuals are at highest risk for liver cancer, and guide prevention and early detection efforts.

描述（由申请人提供）：肝细胞癌 (HCC) 与特定的 p53 突变和黄曲霉毒素 B1 (AFB1) 暴露相关。对肝癌致癌物的个体反应表现出很大的差异。高风险因素包括慢性乙型肝炎 (HBV) 和丙型肝炎病毒 (HCV) 感染，而其他风险因素包括接触烟草烟雾。细胞色素 P450 基因，如 CYP1A1、CYP1A2、CYP3A4 和 CYP3A5 编码的蛋白质可将强效肝癌致癌物激活为基因毒性环氧化物。杂环芳香胺 (HA) 需要 N,O-乙酰转移酶 (NAT2) 进行额外激活。特定细胞色素 P450 多态性和 NAT2 多态性会增加患乳腺癌、胰腺癌和结肠癌等特定癌症的风险。然而，由于许多可能导致代谢物解毒的改变因素，确定 HCC 中 P450 和 NAT 多态性的风险变得复杂。为了确定 P450 多态性本身是否足以增加致癌物的遗传毒性，我们在缺乏解毒酶的酿酒酵母（酵母）中表达了 P450 基因。我们之前观察到，酵母中特定 P450 基因的表达足以刺激致癌物相关的突变和重组、AFB1 暴露后 DNA 修复基因的转录诱导，以及 AFB1 相关的检查点基因 Rad53 (CHK2) 的激活。我们建议进一步筛查与癌症风险增加相关的 CYP1A1、CYP1A2、CYP3A4 和 CYP3A5 多态性。在第一个具体目标中，我们将确定 CYP1A1 和 CYP1A2 多态性的子集是否影响基因重组和突变的频率以及对 AFB1 和肝脏的 DNA 损伤反应致癌物质。在第二个具体目标中，我们将确定CYP1A2和NAT2是否多态性影响酵母中 HA 的代谢激活。在第三个具体目标中，我们将开发酵母中 CYP3A4 和 CYP3A5 的表达系统，使我们能够检测 CYP3A3 和 CYP3A5 多态性介导的致癌物代谢激活。这些因此，研究将为确定细胞色素 P450 的潜在风险提供新策略肝癌的多态性。最终，这些信息将帮助公共卫生从业者和临床医生确定哪些人患肝癌的风险最高，并指导预防和早期发现工作。