Role of local P450 enzymes in chemical carcinogenesis in mouse mammary gland

局部P450酶在小鼠乳腺化学癌变中的作用

• 批准号: 8063627
• 负责人: JUN GU
• 金额: $ 6.82万
• 依托单位: WADSWORTH CENTER
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-05-01 至 2015-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8063627
• 关键词: Age; Anthracenes; Aryl Hydrocarbon Hydroxylases; Blood; Carcinogens; Chemicals; Crossbreeding; Cytochrome P450; DNA Adduction; DNA Adducts; Development; Dose; Enzymes; Epidemiologic Studies; Exposure to; Extrahepatic; Female; Genes; Genetic Polymorphism; Glycols; Hepatic; Hepatic Tissue; Human; Incidence; Knockout Mice; Knowledge; Lactation; Liver; Mammary Gland Parenchyma; Mammary gland; Mediating; Metabolic Activation; Metabolism; Modeling; Mouse Mammary Tumor Virus; Mus; Organ; Oxidoreductase; Physiological; Pilot Projects; Play; Pregnancy; Prevention approach; Proteins; Relative (related person); Research; Role; Site; Staging; Testing; Time; Tissues; Toxic effect; Transgenic Mice; Wild Type Mouse; Xenobiotic Metabolism; base; carcinogenicity; chemical carcinogen; chemical carcinogenesis; design; dimethylbenzanthracene; environmental chemical; environmental chemical exposure; improved; in vivo Model; insight; malignant breast neoplasm; mouse model; novel; public health relevance; research study

DESCRIPTION (provided by applicant): The long-term objective is to determine the mechanisms of chemical carcingensis in the breast tissue. Our current focus is to study the role of mammary cytochrome P450 (P450) enzymes in chemical carcinogen- induced DNA adduct formation in the mammary gland (MG) using tissue-selective gene knockout mouse models. It is well-documented that the microsomal cytochrome P450 (P450) enzymes play a critical role in the metabolic activation of chemical procarcinogens. However, it has been difficult to determine whether, following systemic exposure to a given procarcinogen, the bulk of the activated carcinogen, or its DNA adducts, in the breast tissue is derived from local metabolism or from the liver; the latter organ is generally much more active than extrahepatic target tissues in the metabolic activation of procarcinogens. The problem becomes even more complicated for procarcinogens, such as 7,12-dimethylbenz[a]anthracene (DMBA), that require multiple steps of metabolic activation, given the potential contributions of hepatic or breast tissues to the formation of not only the ultimate carcinogen, but also the intermediate metabolites, such as DMBA-trans-3,4-dihydrodiol (3,4-diol-DMBA), that are precursors to the ultimate carcinogen. Our hypothesis is that target-tissue P450- mediated metabolic activation plays an important role in DMBA-induced formation of DNA adducts in the mammary gland (MG); however, the extent of this target-tissue contribution will vary according to the developmental stages and physiological states of the MG. To test this hypothesis, we will modulate P450 activities in the liver and extrahepatic tissues (including MG) through conditional deletion (or suppression) of the gene for P450 reductase (Cpr), an enzyme required for the activity of all microsomal P450 enzymes. In this two-year pilot project study, we will determine the relative contributions of hepatic and extrahepatic (including the MG) P450 enzymes in the metabolic activation of DMBA, a mammary procarcinogen, and its intermediate metabolite 3,4-diol-DMBA, in newly developed mouse models with tissue-specific suppression of P450 activities, either in the liver alone (designated as liver-Cpr-null mouse), or in all tissues except the liver (designated as extrahepatic-Cpr-low mouse) (Aim 1). Furthermore, we will develop and characterize MG selective Cpr null models (designated as MG-Cpr-null mice), for direct determination of the role of MG P450 enzymes in the MG DNA-adduct formation induced by DMBA and 3,4-diol-DMBA (Aim 2). The knowledge gained from studies will improve the design of epidemiological studies that attempt to associate environmental chemical exposure, and/or genetic polymorphisms in P450 enzymes, with the incidence of breast cancer in humans. It may also help with designing mechanism-based approaches to the prevention of breast cancer. PUBLIC HEALTH RELEVANCE: This research will further our understanding of the mechanisms of chemical carcinogenesis in the mammary gland induced by environmental chemicals, and provide novel insights for mechanism-based approaches to the prevention of breast cancer.

描述(由申请者提供)：长期目标是确定乳房组织中化学癌变的机制。我们目前的重点是利用组织选择性基因敲除小鼠模型来研究乳腺细胞色素P450(P450)酶在化学致癌物诱导的乳腺DNA加合物形成中的作用。已有文献表明，微粒体细胞色素P450(P450)酶在化学致癌物的代谢激活中起着关键作用。然而，在全身暴露于一种特定的致癌物后，很难确定乳腺组织中大部分被激活的致癌物或其DNA加合物是来自局部代谢还是来自肝脏；在致癌物的代谢激活方面，后者通常比肝外靶组织活跃得多。对于前致癌物，如7，12-二甲基苯并[a]菲(DMBA)，问题变得更加复杂，需要多步骤的代谢激活，因为肝脏或乳腺组织不仅对最终致癌物的形成有潜在贡献，而且还对作为最终致癌物前体的中间代谢物，如DMBA-反式-3，4-二氢二醇(3，4-二醇-DMBA)。我们的假设是，靶组织P450介导的代谢激活在DMBA诱导的乳腺DNA加合物的形成中起着重要作用；然而，这种靶组织激活的程度将因MG的发育阶段和生理状态而异。为了验证这一假设，我们将通过有条件地缺失(或抑制)P450还原酶(CPR)基因来调节肝脏和肝外组织(包括MG)的P450活性，CPR是所有微粒体P450酶活性所必需的酶。在这项为期两年的试点研究中，我们将确定肝脏和肝外(包括MG)P450酶在乳腺原癌原DMBA及其中间代谢物3，4-二醇-DMBA代谢激活中的相对贡献，在新开发的组织特异性抑制P450活性的小鼠模型中，要么仅在肝脏(指定为肝脏CPR-空小鼠)，要么在除肝脏以外的所有组织(指定为肝外-CPR-低小鼠)(目标1)。此外，我们将建立和鉴定MG选择性CPR缺失模型(指定为MG-CPR缺失小鼠)，以直接确定MG P450酶在DMBA和3，4-diol-DMBA诱导的MG DNA加合物形成中的作用(目标2)。从研究中获得的知识将改进流行病学研究的设计，这些研究试图将环境化学暴露和/或P450酶基因多态与人类乳腺癌的发病率联系起来。它还可能有助于设计基于机制的预防乳腺癌的方法。 公共卫生意义：这项研究将进一步加深我们对环境化学物质诱导的乳腺化学致癌机制的理解，并为基于机制的预防乳腺癌的方法提供新的见解。