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

• 批准号: 7477314
• 负责人: MICHAEL Thomas FASULLO
• 金额: $ 21.74万
• 依托单位: ORDWAY RESEARCH INSTITUTE, INC.
• 依托单位国家: 美国
• 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/7477314
• 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; Colon; Cytochrome P450; DNA Adduction; DNA Adducts; DNA Damage; DNA Repair Gene; Drug Metabolic Detoxication; Early Diagnosis; End Point; 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; Numbers; 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; cytochrome P450 3A; expression vector; genetic risk factor; genotoxicity; heterocyclic aromatic amines; response

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)：肝细胞癌与特定的p53突变和接触黄曲霉毒素B1(AFB1)有关。个体对肝脏致癌物质的反应表现出很大的差异性。高风险因素包括慢性感染乙肝病毒(乙肝病毒)和丙型肝炎病毒(丙型肝炎病毒)，而其他风险因素包括接触烟草烟雾。细胞色素P450基因，如细胞色素P1A1、细胞色素P1A2、细胞色素P3A4和细胞色素P3A5，编码的蛋白质可将强致癌物激活为具有遗传毒性的环氧化物。杂环芳胺(HAs)需要N，O-乙酰基转移酶(NAT2)的额外激活。特异性细胞色素P450多态和Nat2多态 增加患特定癌症的风险，如乳腺癌、胰腺癌和结肠癌。然而，确定P450和NAT多态在肝癌中的风险是复杂的，许多修饰因素可能导致代谢产物的解毒。为了确定P450多态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中表达了P450基因。我们先前观察到，特定的P450基因在酵母中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。我们建议进一步筛选与癌症风险增加相关的细胞色素P1A1、细胞色素P1A2、细胞色素P3A4和细胞色素P3A5基因。在第一个特定目标中，我们将确定CYP1A1和CYP1A2的一个子集是否影响基因重组和突变的频率以及对黄曲霉毒素B 1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 多态影响酵母中HAS的代谢活性。在第三个具体目标中，我们将 建立细胞色素P3A4和细胞色素P3A5在酵母中的表达系统，使我们能够检测 细胞色素P3A3和细胞色素P3A5基因多态介导的致癌物代谢活化这些 因此，研究将为确定细胞色素P450的潜在风险提供新的策略 肝癌中的基因多态性。最终，这些信息将有助于公共卫生从业者和 临床医生确定哪些人患肝癌的风险最高，并指导预防 以及早期发现的努力。