ROLE OF THE ARYL HYDROCARBON RECEPTOR IN BREAST CANCER

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 二恶英(TCDD)是一种工业副产物和环境污染物，是一种具有致畸、免疫调节和促肿瘤活性的最强的合成毒物。对TCDD的反应是通过芳香烃(或二恶英)受体(AhR)介导的，AhR是配体激活的碱性螺旋-环-螺旋(BHLH)转录因子。TCDD与其受体结合，导致许多基因表达增强，包括那些与细胞增殖和分化有关的基因。我们对该基因表达的初步调查 人类乳腺癌(HBC)细胞系中AhR蛋白的表达与细胞的恶性程度成正比。我们的新发现促使我们假设AhR过度表达在HBC的进展中发挥作用。我们将致力于找出导致正常上皮细胞向具有侵袭性和转移性表型的肿瘤细胞转变的一些因素。为了解决AhR过度表达是否足以转化正常乳腺上皮的问题，以及它是否与转化有因果关系，我们将使用两种遗传学方法。至 直接针对AhR表达增加的影响，人AhR基因将稳定地在正常乳腺上皮细胞中过表达。在AhR转化系中转移表型的发展将被检测为它们在软琼脂和软琼脂中非锚定生长的能力 在裸鼠体内诱发肿瘤。相反，通过转导针对人AhR的siRNA，在高致瘤性HBc细胞系中AhR的表达将被阻断，以证明AhR在改变转移进展中的直接作用。尽管AhR已经在其结合和介导多环芳烃和有机氯毒性的背景下被识别和研究，但越来越多的证据表明它在正常细胞功能中还有其他作用(S)。作为我们拟议研究的基础的新奇观察进一步指出 AhR的另一个病理生理作用。总而言之，我们建议的研究将解决乳腺癌研究中一个研究不足的领域。即使有一个最佳的结果，我们提议的研究也将确定AhR是乳腺癌进展的关键调节因子。一旦确定，AhR可以作为一个独立的预后因子，并可能作为一个早期生物标记物来确定癌症进展的程度，以便进行可能的早期干预。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. TCDD (dioxin), an industrial byproduct and environmental pollutant is the most potent synthetic toxicant that elicits teratogenic, immuno-modulating, and tumor-promoting activities. The responses to TCDD are mediated via the aromatic hydrocarbon (or dioxin) receptor (AhR), which is a ligand-activated basic helix-loop-helix (bHLH) transcription factor. Binding of TCDD to its receptor, results in enhanced expression of many genes including those are involved in cellular proliferation and differentiation. Our preliminary investigation on the expression of the AhR protein in human breast carcinoma (HBC) cell lines has revealed that the AhR is dramatically upregulated in direct proportion to the malignancy of these cells. Our novel findings prompted us to hypothesize that AhR over-expression plays a role in the progression of HBC. We will aim to identify some factors responsible for the disregulation and the switch of normal epithelial to tumor cells with invasive and metastatic phenotype. To address the question of whether the AhR overexpression alone is sufficient for transforming normal mammary epithelia, and whether it is causally associated with transformation, we will use two genetic approaches. To directly address the effect of increased expression of AhR, the human AhR cDNA will be stably transfected and over-expressed in a normal mammary epithelia. The development of metastatic phenotypes in the AhR-transformed lines will be assayed as their ability for anchorage-independent growth in soft agar media and for inducing tumors in nude mice. Conversely, the AhR expression will be blocked in high tumorigenic HBC cell lines by transfecting siRNA targeting human AhR to demonstrate a direct role of the AhR in modifying the progression of metastasis. Although the AhR has been identified and studied in the context of its binding and mediating the toxicity of polycyclic aromatic hydrocarbons and organochlorines, evidence are gathering to suggest other role(s) for it in normal cell function. The novel observations, which are the basis of our proposed studies further point to another patho-physiological role for AhR. In conclusion, our proposed studies will address an understudied area of breast cancer research. Even with an optimum outcome, the research we are proposing will identify the AhR as a key regulator in breast cancer progression. When established, the AhR could be used as an independent prognostic factor, and possibly as an early biomarker for determining the degree of cancer progression for possible early intervention.