Angus W G, Larsen M C, Jefcoate C R
Department of Pharmacology and Environmental Toxicology Center, University of Wisconsin, 3770 Medical Sciences Center, 1300 University Avenue, Madison, WI 53706, USA.
Carcinogenesis. 1999 Jun;20(6):947-55. doi: 10.1093/carcin/20.6.947.
The impact of estrogen receptor (ER) was examined for expression and activity of cytochrome P4501B1 (CYP1B1) and cytochrome P4501A1 (CYP1A1) in two pairs of ER+/ER- human breast epithelial cell lines derived from single lineages, and representing earlier (T47D) or later (MDA-MB-231) stages of tumorigenesis. Acute loss of ER was evaluated using the anti-estrogen ICI 182,780 (ICI). In all lines, CYP1B1 was expressed constitutively and was induced by 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD), whereas CYP1A1 was expressed only following induction. Expression of each CYP (with or without TCDD) was greater in T47D cells than MDA cells. The ER impacted expression of these genes in opposite directions. The ER- phenotype was associated with less TCDD-induced CYP1A1 expression, but greater basal and induced CYP1B1 expression. A 48 h treatment of ER+ cells with ICI did not revert the P450 expression pattern to that of ER- cells. Based on activities of recombinant enzyme and expression levels, differences in 7,2-dimethylbenz [a]anthracene (DMBA) metabolism between the cell lines were consistent with differences in CYP1A1 and CYP1B1 expression. In T47D lines, basal microsomal DMBA metabolism was primarily due to CYP1B1, based on regioselective metabolite distribution and inhibition by anti-CYP1B1 antibodies (>80%). Metabolism in TCDD-induced microsomes was mostly due to CYP1A1 and was inhibited by anti-CYP1A1 antibody (>50%). TCDD-induced MDA+ cells demonstrated CYP1A1 activity, whereas TCDD-induced MDA- cells displayed CYP1B1 activity. Aryl hydrocarbon receptor (AhR) levels, but not AhR nuclear translocator protein (ARNT) levels were highly dependent on cell type; AhR was high and ER-independent in MDA, and low and ER-linked in T47D. AhR levels were insensitive to ICI. ER does not directly modulate the expression of CYP1A1, CYP1B1 or AhR. Indeed, factors that have replaced ER in growth regulation during clonal selection predominate in this regulation. Characteristics unique to each cell line, including ER status, determine CYP1A1 and CYP1B1 expression.
在源自单一谱系、代表肿瘤发生早期（T47D）或晚期（MDA-MB-231）的两对ER+/ER-人乳腺上皮细胞系中，研究了雌激素受体（ER）对细胞色素P4501B1（CYP1B1）和细胞色素P4501A1（CYP1A1）表达及活性的影响。使用抗雌激素ICI 182,780（ICI）评估ER的急性缺失情况。在所有细胞系中，CYP1B1组成性表达，并被2,3,7,8-四氯二苯并对二恶英（TCDD）诱导，而CYP1A1仅在诱导后表达。每种CYP（无论有无TCDD）在T47D细胞中的表达均高于MDA细胞。ER对这些基因表达的影响方向相反。ER-表型与TCDD诱导的CYP1A1表达减少相关，但基础和诱导的CYP1B1表达增加。用ICI对ER+细胞进行48小时处理并未使P450表达模式恢复为ER-细胞的模式。基于重组酶活性和表达水平，细胞系之间7,2-二甲基苯并[a]蒽（DMBA）代谢的差异与CYP1A1和CYP1B1表达的差异一致。在T47D细胞系中，基于区域选择性代谢物分布和抗CYP1B1抗体的抑制作用（>80%），基础微粒体DMBA代谢主要归因于CYP1B1。TCDD诱导的微粒体中的代谢主要归因于CYP1A1，并被抗CYP1A1抗体抑制（>50%）。TCDD诱导的MDA+细胞表现出CYP1A1活性，而TCDD诱导的MDA-细胞表现出CYP1B1活性。芳烃受体（AhR）水平高度依赖于细胞类型，而芳烃受体核转运蛋白（ARNT）水平则不然；AhR在MDA中高表达且不依赖于ER，在T47D中低表达且与ER相关。AhR水平对ICI不敏感。ER不直接调节CYP1A1、CYP1B1或AhR的表达。实际上，在克隆选择过程中替代ER参与生长调节的因素在这种调节中起主导作用。每个细胞系独特的特征，包括ER状态，决定了CYP1A1和CYP1B1的表达。
