Döhr O, Vogel C, Abel J
Heinrich-Heine-University of Düsseldorf, Department of Toxicology, Federal Republic of Germany.
Arch Biochem Biophys. 1995 Aug 20;321(2):405-12. doi: 10.1006/abbi.1995.1411.
Human breast cancer cell lines are widely used to study the antiestrogenic effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in vitro. Like other groups we found that 10 nM TCDD inhibits cell growth and induces cytochrome P450 1A1 (CYP1A1)-associated 7-ethoxyresorufin-O-deethylase (EROD) activity in MCF-7 cells expressing the estradiol receptor (ER). Neither cell growth nor EROD activity was affected in ER-negative MDA-MB 231 cells. Results of reverse transcription-polymerase chain reaction (RT-PCR) revealed a strong induction of CYP1A1 mRNA in MCF-7 but only a weak increase in MDA-MB 231 cells treated with 1, 10, or 100 nM TCDD. Transcripts of CYP1B1 were detected in both cell lines and mRNA content was enhanced 8- and 30-fold in MCF-7 and MDA-MB 231 cells treated with 1 nM TCDD, respectively. In gel mobility shift assay a stronger signal of DNA-binding aryl hydrocarbon receptor (AhR) was observed in MDA-MB 231 than in MCF-7 cells treated with 10 nM TCDD. These results were confirmed by RT-PCR analyses which showed an approximately 40-fold higher AhR mRNA content in untreated MDA-MB 231 than in MCF-7 cells. In contrast the mRNA of the AhR nuclear translocator was expressed in a similar range of magnitude. Treatment of the cells with TCDD did not change mRNA expression of both genes. Analysis of NADPH:quinone oxidoreductase (NMO-1) and plasminogen activator inhibitor-2 (PAI-2) mRNA expression revealed a dose-dependent induction of both genes in MDA-MB 231 cells after TCDD-treatment. From the results it was concluded that AhR-mediated transactivation is not impaired in ER-negative MDA-MB 231 cells. In addition, the results confirm reported data that expression of ER seems to be important for regulation of CYP1A1 induction after TCDD in human breast cancer cell lines but the present data show that ER does not appear to have a function in TCDD-induced mRNA expression of CYP1B1, NMO-1, and PAI-2 in MDA-MB 231 cells.
人乳腺癌细胞系被广泛用于体外研究2,3,7,8-四氯二苯并-对-二恶英（TCDD）的抗雌激素作用。与其他研究小组一样，我们发现10 nM TCDD可抑制细胞生长，并在表达雌二醇受体（ER）的MCF-7细胞中诱导细胞色素P450 1A1（CYP1A1）相关的7-乙氧基异吩恶唑酮-O-脱乙基酶（EROD）活性。在ER阴性的MDA-MB 231细胞中，细胞生长和EROD活性均未受到影响。逆转录-聚合酶链反应（RT-PCR）结果显示，在MCF-7细胞中CYP1A1 mRNA被强烈诱导，但在用1、10或100 nM TCDD处理的MDA-MB 231细胞中仅微弱增加。在两种细胞系中均检测到CYP1B1转录本，在用1 nM TCDD处理的MCF-7和MDA-MB 231细胞中，mRNA含量分别增加了8倍和30倍。在凝胶迁移率变动分析中，在用10 nM TCDD处理的MDA-MB 231细胞中观察到的DNA结合芳烃受体（AhR）信号比MCF-7细胞中的更强。RT-PCR分析证实了这些结果，该分析显示未处理的MDA-MB 231细胞中的AhR mRNA含量比MCF-7细胞高约40倍。相反，AhR核转运蛋白的mRNA在相似的数量范围内表达。用TCDD处理细胞并未改变这两个基因的mRNA表达。对NADPH：醌氧化还原酶（NMO-1）和纤溶酶原激活物抑制剂-2（PAI-2）mRNA表达的分析显示，TCDD处理后MDA-MB 231细胞中这两个基因均呈剂量依赖性诱导。从结果得出结论，在ER阴性的MDA-MB 231细胞中，AhR介导的反式激活未受损。此外，结果证实了已报道的数据，即ER的表达似乎对人乳腺癌细胞系中TCDD后CYP1A1诱导的调节很重要，但目前的数据表明ER似乎在MDA-MB 231细胞中TCDD诱导的CYP1B1、NMO-1和PAI-2的mRNA表达中不起作用。
