ROLE OF THE ARYL HYDROCARBON RECEPTOR IN BREAST CANCER

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。列出的机构是 中心，不一定是研究者的机构。 二恶英（TCDD）是一种工业副产物和环境污染物，是具有致畸、免疫调节和促肿瘤活性的最强人工合成毒物。 对TCDD的反应是通过芳香烃（或二恶英）受体（AhR）介导的，AhR是一种配体激活的碱性螺旋-环-螺旋（bHLH）转录因子。 TCDD与其受体的结合导致许多基因的表达增强，包括那些参与细胞增殖和分化的基因。 我们初步研究了 人乳腺癌（HBC）细胞系中的AhR蛋白揭示了AhR的显著上调与这些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的进展中起作用。我们的目标是确定一些因素负责失调和开关正常上皮细胞的肿瘤细胞的侵袭性和转移表型。 为了解决AhR过度表达是否足以转化正常乳腺上皮细胞，以及它是否与转化有因果关系的问题，我们将使用两种遗传方法。 到 直接解决AhR表达增加的作用，人AhR cDNA将在正常乳腺上皮中稳定转染并过表达。 AhR转化系中转移表型的发展将被测定为它们在软琼脂培养基中的锚定非依赖性生长的能力和它们在培养基中的生长能力。 在裸鼠中诱导肿瘤。 相反，通过阻断靶向人AhR的siRNA，AhR表达将在高致瘤性HBC细胞系中被阻断，以证明AhR在改变转移进展中的直接作用。 虽然AhR已被确定并在其结合和介导多环芳烃和有机氯的毒性的背景下进行了研究，但证据正在收集，表明它在正常细胞功能中的其他作用。 新的观察结果是我们提出的研究的基础，进一步指出， AhR的另一个病理生理作用。 总之，我们提出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，我们提出的研究将确定AhR作为乳腺癌进展的关键调节因子。 当建立时，AhR可以用作独立的预后因素，并可能作为早期生物标志物，用于确定癌症进展的程度，以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.