探討乳癌細胞株MCF-7在常氧與缺氧下NDRG1對細胞功能的影響與受到的新轉錄調控

過去研究發現N-myc downstream-regulated gene 1 (NDRG1)會影響到許多癌症的發展，也在腫瘤適應氧濃度變化上扮演重要的角色。先前我們實驗室發現乳癌細胞株MCF-7中、NDRG1在缺氧刺激下會大量表現，同時芳香烴受體(aryl hydrocarbon receptor, AHR)的結合位點存在於NDRG1的啟動子上。然而，我們仍然不清楚缺氧調控NDRG1表現的機制以及NDRG1對乳癌細胞的影響，因此本篇的研究目的是探討芳香烴受體能否在調控NDRG1表現上、扮演轉錄因子的角色，並且了解在氧濃度變化下、NDRG1對癌細胞功能的影響。在缺氧濃度下，免疫螢光染色和染色質免疫沈澱法顯示芳香烴受體轉移至核內並結合到NDRG1啟動子(-412 ~ -388鹼基對)上。同時，過度表現芳香烴受體會藉由增進NDRG1表現來促進細胞的增生與遷移，然而利用小片段干擾核糖核酸機制抑制NDRG1表現後，細胞會減低成長與遷移。另一方面，在正常氧濃度下、過度表現NDRG1會抑制細胞的生長與遷移。過度表現NDRG1也會抑制腫瘤細胞在裸鼠體內的生長。此外，NDRG1在乳癌細胞株與腫瘤組織中亦有明顯下降的情形。總而言之，本研究顯示一個新的轉錄調控，即在缺氧刺激下、芳香烴受體會促進NDRG1表現量上升；並且顯示NDRG1在乳癌細胞的成長與遷移能力上、扮演動態調控的角色。

關鍵字

芳香烴受體； NDRG1 ；常氧；缺氧；乳癌

並列摘要

N-myc downstream-regulated gene 1 (NDRG1) has been reported to regulate tumor progression in various cancers. In addition, it plays a critical role in tumor adaptation to fluctuation of oxygen concentrations. Previously, we showed that NDRG1 was strongly up-regulated under hypoxia in a breast cancer cell line MCF-7, and predicted to contain binding sites for aryl hydrocarbon receptor (AHR) at its promoter. However, the regulatory mechanism of NDRG1 expression under hypoxia and its cellular function remained elusive. Therefore, the aims of this study were to elucidate whether AHR could modulate NDRG1 expression, and to investigate the functional roles of NDRG1 upon changes in oxygen concentrations. In hypoxia, immunofluorescence staining and chromatin immunoprecipitation assays showed that AHR translocated to nuclei and bound to NDRG1 promoter (-412 ~ -388 bp). Also, over-expression of AHR facilitated cell proliferation and migration via up-regulation of NDRG1, whereas shRNA knockdown of NDRG1 reduced cell growth and motility. On the other hand, over-expression of NDRG1 under normoxia suppressed cell proliferation and migration ability. Tumor growth on the nude mice was also inhibited in cells over-expressed with NDRG1. Clinically, NDRG1 was down-regulated in breast cancer cell lines and tumor tissues. In summary, these results showed a novel mechanism of NDRG1 regulated by AHR upon hypoxic stress, and highlighted the dynamic role of NDRG1 in regulating cell growth and migration capacity during oxygen fluctuation in breast cancer.

並列關鍵字

aryl hydrocarbon receptor ； NDRG1 ； normoxia ； hypoxia ； breast cancer

參考文獻

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探討乳癌細胞株MCF-7在常氧與缺氧下NDRG1對細胞功能的影響與受到的新轉錄調控

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