Gene Expression Preferentially Regulated by Tamoxifen in Breast Cancer Cells. Homo sapiens

The beneficial effect of the selective estrogen receptor modulator (SERM) tamoxifen in the treatment and prevention of breast cancer is assumed to be through its ability to antagonize the stimulatory actions of estrogen, although tamoxifen can also have some estrogen-like agonist effects. Here we report that in addition to these mixed agonist/antagonist actions, tamoxifen can also selectively regulate a unique set of more than 60 genes in estrogen receptor alpha (ERa)-positive MCF-7 human breast cancer cells which are minimally regulated by estradiol or raloxifene. This gene regulation by tamoxifen is mediated by ERa and is reversed by estradiol or ICI 182,780. We find that the introduction of ERbeta into MCF-7 cells reverses tamoxifen action on approximately 75% of these genes, suggesting that ERbeta is capable of repressing certain actions of tamoxifen. To examine whether these genes might serve as markers of tamoxifen sensitivity and/or the development of resistance, the expression level of these genes was examined in breast tumors of women who had received treatment with tamoxifen. High expression of two of the tamoxifen stimulated genes, YWHAZ/14-3-3z and LOC441453, was found to correlate significantly with disease recurrence following tamoxifen treatment in women with ER-positive tumors, and hence appear to be markers of a poor prognosis. Our data indicate a new dimension in tamoxifen action, involving gene expression regulation that is tamoxifen-preferential, and identify genes that might serve as markers of tumor responsiveness or resistance to tamoxifen therapy. Keywords: ligand response in two ER backgrounds Overall design: MCF-7 cells expressing endogenous ERalpha were infected with adenovirus carrying either estrogen receptor beta (AdERb) or no insert (Ad) at multiplicity of infection (moi) of 10. Cells were infected with adenovirus for a period of 48hr before treatment with ligand (vehicle control, 10nM 17beta-estradiol, or 10nM hydroxytamoxifen) for a additional period of 24hr before harvest.

选择性雌激素受体调节剂（selective estrogen receptor modulator, SERM）他莫昔芬在乳腺癌治疗与预防中的有益作用，既往认为是通过拮抗雌激素的刺激活性实现的，尽管他莫昔芬本身也可表现出部分类雌激素激动活性。本研究发现，除上述兼具激动与拮抗的双重活性外，他莫昔芬还可在雌激素受体α（estrogen receptor alpha, ERα）阳性的人乳腺癌MCF-7细胞中，选择性调控一组共60余个独特基因；而雌二醇或雷洛昔芬对这些基因的调控作用极弱。他莫昔芬的此类基因调控作用由ERα介导，且可被雌二醇或ICI 182,780逆转。我们发现，向MCF-7细胞中转入雌激素受体β（estrogen receptor beta, ERβ）后，可逆转他莫昔芬对其中约75%基因的调控作用，这表明ERβ能够抑制他莫昔芬的部分生物学活性。为探究这些基因能否作为他莫昔芬敏感性或耐药性发生的标志物，我们对接受他莫昔芬治疗的女性乳腺癌患者的肿瘤组织中这些基因的表达水平进行了检测。在ER阳性乳腺癌患者中，他莫昔芬诱导的两个基因YWHAZ/14-3-3ζ与LOC441453的高表达，与他莫昔芬治疗后的疾病复发显著相关，因此可作为不良预后的标志物。本研究揭示了他莫昔芬作用的新维度，即存在他莫昔芬偏好性的基因表达调控模式，并鉴定出可作为肿瘤对他莫昔芬治疗应答或耐药性标志物的基因。
关键词：两种雌激素受体背景下的配体应答
实验设计：将表达内源性ERα的MCF-7细胞以感染复数（multiplicity of infection, MOI）10的剂量，感染携带雌激素受体β（AdERβ）或空载（Ad）的腺病毒。细胞经腺病毒感染48小时后，分别用配体（溶剂对照、10nM 17β-雌二醇或10nM 羟基他莫昔芬）处理24小时，随后收集细胞。