Tamoxifen through GPER upregulates aromatase expression: a novel mechanism sustaining tamoxifen-resistant breast cancer cell growth
Tamoxifen through GPER upregulates aromatase expression: a novel mechanism sustaining tamoxifen-resistant breast cancer cell growth
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DOI：
10.1007/s10549-014-3017-4
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发表时间：
2014-07-01
影响因子：
3.8
通讯作者：
Barone, Ines
中科院分区：
文献类型：
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作者：
Catalano, Stefania;Giordano, Cinzia;Barone, Ines
他莫昔芬耐药是乳腺癌治疗中的主要临床挑战。芳香化酶抑制剂对他莫昔芬治疗后进展或复发的女性有效，这表明芳香化酶在驱动他莫昔芬耐药表型中的局部雌激素产生的作用。然而，芳香酶活性与他莫昔芬耐药性之间的联系尚未报道。我们研究了长期暴露于他莫昔芬是否会影响芳香化酶的活性和/或表达，从而维持耐他莫昔芬的乳腺癌细胞的生长。我们使用MCF-7乳腺癌细胞、他莫昔芬耐药MCF-7细胞（MCF-7 TR 1和TR 2）、SKBR-3乳腺癌细胞、癌症相关成纤维细胞（CAFs 1和CAFs 2）。我们使用氚水释放试验，实时RT-PCR和免疫印迹分析，用于评估芳香酶的活性和表达;锚定独立的生长测定;启动子活性研究的启动子基因，细胞迁移率变化和染色质免疫沉淀测定。我们证明了芳香化酶活性和表达的增加，这支持了他莫昔芬耐药乳腺癌细胞的增殖。这是由G蛋白偶联受体GPR 30/GPER介导的，因为敲低GPER表达或用GPER拮抗剂治疗逆转了由长期他莫昔芬暴露诱导的增强的芳香酶水平。在ER阴性，GPER/芳香化酶阳性SKBR 3细胞中研究了分子机制，其中他莫昔芬作为GPER激动剂。他莫昔芬处理通过增强c-fos/c-jun复合物向位于启动子区域内的AP-1应答元件的募集来增加芳香化酶启动子活性。由于他莫昔芬通过GPER诱导CAF中的芳香化酶表达，该途径可能参与促进乳腺肿瘤对他莫昔芬治疗的反应的侵袭行为。阻断雌激素产生和/或GPER信号激活可能是克服乳腺癌他莫昔芬耐药性的有效选择。
Tamoxifen resistance is a major clinical challenge in breast cancer treatment. Aromatase inhibitors are effective in women who progressed or recurred on tamoxifen, suggesting a role of local estrogen production by aromatase in driving tamoxifen-resistant phenotype. However, the link between aromatase activity and tamoxifen resistance has not yet been reported. We investigated whether long-term tamoxifen exposure may affect aromatase activity and/or expression, which may then sustain tamoxifen-resistant breast cancer cell growth. We employed MCF-7 breast cancer cells, tamoxifen-resistant MCF-7 cells (MCF-7 TR1 and TR2), SKBR-3 breast cancer cells, cancer-associated fibroblasts (CAFs1 and CAFs2). We used tritiated-water release assay, realtime-RT-PCR, and immunoblotting analysis for evaluating aromatase activity and expression; anchorage-independent assays for growth; reporter-gene, electrophoretic-mobility-shift, and chromatin-immunoprecipitation assays for promoter activity studies. We demonstrated an increased aromatase activity and expression, which supports proliferation in tamoxifen-resistant breast cancer cells. This is mediated by the G-protein-coupled receptor GPR30/GPER, since knocking-down GPER expression or treatment with a GPER antagonist reversed the enhanced aromatase levels induced by long-term tamoxifen exposure. The molecular mechanism was investigated in ER-negative, GPER/aromatase-positive SKBR3 cells, in which tamoxifen acts as a GPER agonist. Tamoxifen treatment increased aromatase promoter activity through an enhanced recruitment of c-fos/c-jun complex to AP-1 responsive elements located within the promoter region. As tamoxifen via GPER induced aromatase expression also in CAFs, this pathway may be involved in promoting aggressive behavior of breast tumors in response to tamoxifen treatment. Blocking estrogen production and/or GPER signaling activation may represent a valid option to overcome tamoxifen-resistance in breast cancers.