The Aryl Hydrocarbon Receptor and Breast Cancer

描述(申请人提供)：我们的目标是研究芳香烃受体(AhR)在乳腺癌进展中的作用，长期目标是将AhR作为乳腺癌预防和治疗干预的靶点。AHR是一种配体激活的转录因子，介导环境中多环芳烃(PAH)的致癌作用。AhR的PAH激活通过诱导CYP1家族基因和随后产生的反应性代谢物和转录因子的激活而参与癌症的发生。我们的实验室和其他人已经报道了在晚期人类乳腺癌中成分激活的AhR的高水平表达。我们进一步证明，AhR的异位过表达足以诱导人乳腺上皮细胞(HMEC)发生恶性转化，而不依赖于PAH。我们建立的AhR转化的HMEC克隆细胞系在体外表现出促进增殖、上皮向间充质转化以及增强迁移和侵袭能力。因此，我们推测AhR的高表达与乳腺癌的进展相关，并预测乳腺癌的进展，AhR的高表达通过上调对肿瘤生存和侵袭性至关重要的信号通路促进浸润性乳腺癌的发展。为了解决这一假说，我们的具体目标是：1)使用SCID小鼠异种移植模型，通过原位移植过表达AhR的克隆性HMEC细胞株并展示其形成乳腺肿瘤和转移隐匿性的能力，来测试AhR过表达与体内侵袭性癌症发生和发展的相关性；2)通过siRNA抑制AhR过表达细胞中AhR的表达，从而检测AhR过表达在侵袭性癌的发生和发展中的因果作用，然后评估它们在体外和SCID小鼠中的致瘤潜力；3)确定哪些基因和信号通路是由AhR过表达激活的；4)应用组织芯片技术，通过研究AhR在乳腺癌中的表达与疾病分期及其他预后指标的关系，探讨AhR在晚期乳腺癌中的表达是否普遍上调。这项拟议的研究将确定AhR在浸润性乳腺癌进展中的因果作用。我们的发现可能验证AhR作为一种新的预测临床标志物和设计新的选择性抑制物用于转移性乳腺癌治疗干预的独特靶点。 公共卫生相关性：本申请中的拟议研究旨在解决和定义AhR在浸润性乳腺癌进展中的因果作用。这些研究的结果将有助于确定AhR是乳腺癌转移决定因素之一，从而将其确立为乳腺癌的独立生存预后因素。这些研究也将有助于更好地了解AhR在晚期乳腺癌中的分子作用及其配体非依赖性激活，从而为设计新的选择性抑制剂用于转移性乳腺癌的治疗提供独特的靶点。

DESCRIPTION (provided by applicant): Our objective is to investigate the role of the aryl hydrocarbon receptor (AhR) in breast cancer progression with a long-term goal of targeting AhR for preventive and therapeutic intervention of breast cancer. AhR is a ligand- activated transcription factor which mediates the carcinogenic effects of environmental polycyclic aromatic hydrocarbons (PAH). PAH activation of AhR is implicated in carcinogenesis through induction of CYP1 family of genes with subsequent generation of reactive metabolites and activation of transcription factors. Our laboratory and others have reported high-level expression of constitutively activated AhR in advanced human breast carcinomas. We further showed that ectopic over expression of AhR is sufficient to induce malignant transformation of human mammary epithelial cells (HMEC), independent of PAH. Our generated clonal cell lines of the AhR-transformed HMEC exhibited enhanced proliferation, epithelial-to-mesenchymal transition and enhanced migration and invasiveness, as measured in vitro. We therefore postulated that elevated expression of AhR correlates with and forecasts breast cancer progression and that high AhR expression promotes the development of invasive breast carcinoma by up-regulating signaling pathways critical for tumor survival and invasiveness. To address this hypothesis our specific aims are 1) To test the relevance of AhR over expression for development and progression of invasive carcinoma in vivo using SCID mice xenograft model, by orthotopically implanting clonal HMEC cell lines which over express AhR and demonstrating their ability to form mammary tumors and metastatic occults 2) To examine the causal role of the AhR over expression on the development and progression of invasive carcinoma by the siRNA knockdown of AhR expression in cells overexpressing AhR followed by assessing their tumorigenic potential in vitro and in SCID mice 3) To determine which genes and signaling pathways for tumor progression are activated by AhR over expression; 4) To examine whether the expression of AhR is universally upregulated in advanced human breast cancer, by correlating the AhR expression in human breast tumors with the stage of the disease and other prognostic biomarkers using tissue microarrays. The proposed research will define the causal role of AhR in invasive breast cancer progression. Our findings may validate the AhR as a new predictive clinical marker and a unique target for designing novel selective inhibitors for therapeutic intervention of metastatic breast cancer. PUBLIC HEALTH RELEVANCE: The proposed research in this application is designed to address and define the causal role of AhR in invasive breast cancer progression. Results from these studies will help identify the AhR as one of the breast cancer metastatic determinants; thus establishing it as an independent survival prognostic factor for breast cancer. The studies will also lead to a better understanding of the molecular action of AhR and its ligand-independent activation in advanced breast cancer, thus providing a unique target for the design of novel selective inhibitors for therapeutic intervention of metastatic breast cancer.