Estrogen regulates Ah responsiveness in MCF-7 breast cancer cells.
Estrogen regulates Ah responsiveness in MCF-7 breast cancer cells.
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DOI：
10.1093/carcin/bgg162
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发表时间：
2003-12
期刊：
影响因子：
4.7
通讯作者：
D. Spink;B. H. Katz;M. Hussain;B. Pentecost;Z. Cao;B. C. Spink
中科院分区：
文献类型：
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作者：
D. Spink;B. H. Katz;M. Hussain;B. Pentecost;Z. Cao;B. C. Spink
细胞色素P450(CYP)1A1和细胞色素P1B1受芳香烃受体(AhR)调控，分别催化C-2和C-4位17β-雌二醇(E_2)的代谢活化和17β-雌二醇(E_2)的羟基化。有证据表明，在乳腺和子宫内膜细胞中，雌激素受体α(ERpha)和AhR介导的信号之间存在串扰。为了进一步研究这些相互作用，我们研究了E2暴露对MCF-7人乳腺癌细胞AH反应性的短期和长期影响。实时定量聚合酶链式反应显示，短期暴露于1 nM E2可增加2，3，7，8-四氯二苯并对二恶英(TCDD)诱导的E2代谢的4-羟化途径和2-羟基化途径的比例，以及诱导的CYP1B1/CYP1A1基因水平的比例。细胞长期(9-12个月)在低E_2培养液中逐渐失去AH反应性，表现为TCDD诱导的E_2代谢率和乙氧基间苯二酚O-脱乙基酶活性降低，以及CYP1A1和CYP1B1mRNAs和蛋白质水平的降低。这些缺乏E2的细胞表现出ERpha mRNA水平升高，AhR mRNA水平降低，AhR核转运子mRNA水平不变。使用CYP1B1-启动子-荧光素酶报告基因构建的瞬时转染研究表明，在缺乏E2的细胞中，通过与AhR表达构建物共转染可以恢复降低的CYP1B1启动子活性，这表明AhR在这些细胞中的表达是有限的。在添加1 nM E_2的培养液中培养4代后，缺乏E_2的细胞的AH反应性降低，ERa和AhR的mRNAs恢复到接近正常的水平，并恢复了TCDD对CYP1A1和CYP1B1mRNAs、蛋白质和E_2代谢活性的诱导能力。这些研究表明，在MCF-7细胞中，雌激素的持续存在是维持高水平的AhR表达和前致癌物生物激活酶CYP1A1和CYP1B1诱导性所必需的。
Cytochrome P450 (CYP)1A1 and CYP1B1, which are under the regulatory control of the aryl hydrocarbon (Ah) receptor (AhR), catalyze the metabolic activation of numerous procarcinogens and the hydroxylation of 17beta-estradiol (E2) at the C-2 and C-4 positions, respectively. There is evidence of cross-talk between estrogen receptor alpha (ERalpha)- and AhR-mediated signaling in breast and endometrial cells. To further examine these interactions, we investigated the short- and long-term effects of E2 exposure on Ah responsiveness in MCF-7 human breast cancer cells. Short-term exposure to 1 nM E2 elevated the ratio of the 4- to 2-hydroxylation pathways of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced E2 metabolism and the ratio of the induced CYP1B1 to CYP1A1 mRNA levels, as determined by real-time PCR. Cells maintained long-term (9-12 months) in low-E2 medium progressively lost Ah responsiveness, as indicated by diminished rates of TCDD-induced E2 metabolism and ethoxyresorufin O-deethylase activity, and the reduced expression of the CYP1A1 and CYP1B1 mRNAs and proteins levels. These E2-deprived cells showed elevated levels of ERalpha mRNA, depressed levels of AhR mRNA, and unchanged levels of the AhR nuclear translocator mRNA. Transient transfection studies using a CYP1B1-promoter-luciferase reporter construct showed that reduced CYP1B1 promoter activity in E2-deprived cells could be restored by co-transfection with an AhR expression construct, indicating that AhR expression was limiting in these cells. The reduced Ah responsiveness of E2-deprived cells was reversed by culture for four passages in medium supplemented with 1 nM E2; ERalpha and AhR mRNAs returned to near-normal levels and the inducibility of the CYP1A1 and CYP1B1 mRNAs, proteins, and E2 metabolic activities by TCDD was restored. These studies indicate that the continued presence of estrogen is required to maintain high levels of AhR expression and inducibility of the procarcinogen-bioactivating enzymes, CYP1A1 and CYP1B1, in MCF-7 cells.