Mechanisms of Tumor Promotion Effects of B[a]PDE

说明书(申请人提供)：多环芳烃(PAHs)，如苯并[a]芘(B[a]P)，是烟草烟雾中普遍存在的完全致癌物质。在以前的研究中，大部分工作都集中在与这些化合物的肿瘤启动效应相关的突变上。然而，多环芳烃的促肿瘤作用被认为是通过调节导致转录因子激活的信号转导途径来实现的，目前还不清楚。我们的初步研究表明，苯并[a]芘二醇环氧化物(B[a]PDE)是苯并[a]芘(B[a]P)的最终致癌代谢产物，是在非细胞毒性浓度下激活转录因子激活蛋白-1(AP-1)的主要化合物。由于越来越多的证据表明，在细胞培养模型和动物实验中，致癌物激活AP-1是促肿瘤所必需的，因此本建议的主要假设是，导致AP-1激活的信号转导通路在B[a]PDE诱导的促癌作用中起着关键作用。这项建议的总体目标是阐明多环芳烃诱导肿瘤促进的分子机制。特别是，我们将在一个具有良好特性的促肿瘤细胞培养模型--小鼠表皮C141细胞中建立B[a]PDE激活AP-1的信号转导通路。然后，我们将使用AP-1-荧光素酶报告转基因小鼠模型来研究是否在体内模型中发生相同的途径。此外，我们将使用显性负突变c-jun(TAM67)转基因小鼠，在两阶段致癌小鼠皮肤模型中确定AP-1激活在B[a]PDE诱导的肿瘤促进中的作用。我们将根据以下可检验的假设和特定的目的来研究这些问题：1)阐明B[a]PDE在小鼠表皮C141细胞中启动导致AP-1激活的信号通路的早期事件；2)验证B[a]PDE在小鼠表皮C141细胞中诱导AP-1激活需要PI-3K/Akt/p7086k途径的假设；3)通过AP-1-荧光素酶报告基因转基因小鼠，确定B[a]PDE是否能够在体内诱导AP-1激活，以及这种激活是否通过与体外相同的信号转导途径；4)验证AP-1活化在B[a]PDE两阶段致癌小鼠模型中的促癌作用。本申请中提出的研究的意义在于，从建议的研究结果将极大地促进了解苯并[a]磷和苯并[a]二苯醚引起癌症发生的分子机制。更好地了解导致AP-1诱导的信号转导通路可能为设计更有效的预防和治疗吸烟引起的癌症的药物提供必要的有价值的信息。这类药物可能会干扰导致AP-1激活的信号通路。

DESCRIPTION (provided by applicant): Polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (B[a]P), are ubiquitous complete carcinogens that are present in tobacco smoke. The majority of work in previous studies has focused on the mutations that are associated with the tumor initiation effect of these compounds. However, the tumor promotion effect of PAHs, which is thought to be mediated through regulation of signal transduction pathways leading to activation of transcription factors, remains unclear. Our preliminary studies suggest that benzo[a]pyrene diol-epoxide (B[a]PDE), an ultimate carcinogenic metabolite of benzo[a]pyrene (B[a]P), is a major compound responsible for activation of the transcription factor activator protein-1 (AP-1) in non-cytotoxic concentrations. Since growing evidence has shown that activation of AP-1 by carcinogens is required for tumor promotion in both cell culture models and animal experiments, the main hypothesis of this proposal is that signal transduction pathways leading to activation of AP-1 play a critical role in the tumor promotion effect induced by B[a]PDE. The overall aim of this proposal is to elucidate the molecular mechanisms by which PAHs induce tumor promotion. Especially, we will establish the signal transduction pathways leading to AP-1 activation by B[a]PDE in a well-characterized tumor promotion cell culture model, mouse epidermal C141 cells. We will then investigate whether the same pathway occurs in an in vivo model using an AP-1-luciferase reporter transgenic mouse model. Furthermore, we will determine the role of AP-1 activation in B[a]PDE-induced tumor promotion in a two-stage carcinogenesis mouse skin model using dominant negative mutant c-jun (TAM67) transgenic mice. We will investigate these issues in accordance with the following testable hypotheses and specific aims: 1) To elucidate early events involved in initiating the signaling pathways leading to AP-1 activation by B[a]PDE in mouse epidermal C141 cells; 2) To test the hypothesis that the PI-3K/Akt/p7086k pathway is required for B[a]PDE-induced AP-1 activation in mouse epidermal C141 cells; 3) To determine whether B[a]PDE is able to induce AP-1 activation in vivo by using AP-1-luciferase reporter transgenic mice and whether this activation is through the same signal transduction pathways as in vitro; 4) To test the hypothesis that AP-1 activation is essential in the tumor promotion effect of B[a]PDE in a two-stage carcinogenesis mouse model. The significance of the research proposed in this application is that the results derived from the proposed studies will greatly facilitate the understanding of the molecular mechanism of cancer development caused by B[a]P and B[a]PDE. A better understanding of signal transduction pathways leading to AP-1 induction may provide valuable information needed for designing more effective agents for prevention and therapy of cancers caused by cigarette smoke. Such agents could interfere with the signaling pathways leading to AP-1 activation.