Department of Bioscience and Biotechnology, College of Life Science, Institute of Biotechnology, Sejong University, Kwangjingu, Kunjadong, Seoul 143-747, Korea.
Breast Cancer Res. 2011 Mar 24;13(2):R32. doi: 10.1186/bcr2854.
Estrogen receptor (ER) β is predicted to play an important role in prevention of breast cancer development and metastasis. We have shown previously that ERβ inhibits hypoxia inducible factor (HIF)-1α mediated transcription, but the mechanism by which ERβ works to exert this effect is not understood.
Vascular endothelial growth factor (VEGF) was measured in conditioned medium by enzyme-linked immunosorbent assays. Reverse transcription polymerase chain reaction (RT-PCR), Western blotting, immunoprecipitation, luciferase assays and chromatin immunoprecipitation (ChIP) assays were used to ascertain the implication of ERβ on HIF-1 function.
In this study, we found that the inhibition of HIF-1 activity by ERβ expression was correlated with ERβ's ability to degrade aryl hydrocarbon receptor nuclear translocator (ARNT) via ubiquitination processes leading to the reduction of active HIF-1α/ARNT complexes. HIF-1 repression by ERβ was rescued by overexpression of ARNT as examined by hypoxia-responsive element (HRE)-driven luciferase assays. We show further that ERβ attenuated the hypoxic induction of VEGF mRNA by directly decreasing HIF-1α binding to the VEGF gene promoter.
These results show that ERβ suppresses HIF-1α-mediated transcription via ARNT down-regulation, which may account for the tumour suppressive function of ERβ.
雌激素受体（ER）β被预测在预防乳腺癌发展和转移方面发挥重要作用。我们之前已经表明，ERβ 抑制缺氧诱导因子（HIF）-1α 介导的转录，但 ERβ 发挥这种作用的机制尚不清楚。
通过酶联免疫吸附试验测量条件培养基中的血管内皮生长因子（VEGF）。反转录聚合酶链反应（RT-PCR）、Western blot、免疫沉淀、荧光素酶测定和染色质免疫沉淀（ChIP）测定用于确定 ERβ 对 HIF-1 功能的影响。
在这项研究中，我们发现 ERβ 表达对 HIF-1 活性的抑制与 ERβ 通过泛素化过程降解芳香烃受体核转位蛋白（ARNT）的能力相关，导致活性 HIF-1α/ARNT 复合物减少。通过缺氧反应元件（HRE）驱动的荧光素酶测定，我们进一步表明，ARNT 的过表达挽救了 ERβ 对 HIF-1 抑制。我们还表明，ERβ 通过直接减少 HIF-1α 与 VEGF 基因启动子的结合来减弱 VEGF mRNA 的低氧诱导。
这些结果表明，ERβ 通过下调 ARNT 抑制 HIF-1α 介导的转录，这可能是 ERβ 抑制肿瘤的功能。
