NCOA3 是 MCF-7 乳腺癌细胞中雌激素受体 α 介导的 PLAC1 转录激活的选择性共激活因子。
NCOA3 is a selective co-activator of estrogen receptor α-mediated transactivation of PLAC1 in MCF-7 breast cancer cells.
机构信息
Department of Internal Medicine III, Division of Translational and Experimental Oncology, University Medical Center, Johannes Gutenberg University, 55131 Mainz, Germany.
出版信息
BMC Cancer. 2013 Dec 4;13:570. doi: 10.1186/1471-2407-13-570.
BACKGROUND
The placenta-specific 1 (PLAC1) gene encodes a membrane-associated protein which is selectively expressed in the placental syncytiotrophoblast and in murine fetal tissues during embryonic development. In contrast to its transcriptional repression in all other adult normal tissues, PLAC1 is frequently activated and highly expressed in a variety of human cancers, in particular breast cancer, where it associates with estrogen receptor α (ERα) positivity. In a previous study, we showed that ERα-signaling in breast cancer cells transactivates PLAC1 expression in a non-classical pathway. As the members of the p160/nuclear receptor co-activator (NCOA) family, NCOA1, NCOA2 and NCOA3 are known to be overexpressed in breast cancer and essentially involved in estrogen-mediated cancer cell proliferation we asked if these proteins are involved in the ERα-mediated transactivation of PLAC1 in breast cancer cells.
METHODS
Applying quantitative real-time RT-PCR (qRT-PCR), Western Blot analysis and chromatin immunoprecipitation, we analyzed the involvement of NCOA1, NCOA2, NCOA3 in the ERα-mediated transactivation of PLAC1 in the breast cancer cell lines MCF-7 and SK-BR-3. RNAi-mediated silencing of NCOA3, qRT-PCR, Western blot analysis and ERα activation assays were used to examine the role of NCOA3 in the ERα-mediated regulation of PLAC1 in further detail. Transcript expression of NCOA3 and PLAC1 in 48 human breast cancer samples was examined by qRT-PCR and statistical analysis was performed using Student's t-test.
RESULTS
We detected selective recruitment of NCOA3 but not NCOA1 or NCOA2 to the PLAC1 promoter only in ERα-positive MCF-7 cells but not in ERα-negative SK-BR-3 breast cancer cells. In addition, we demonstrate that silencing of NCOA3 results in a remarkable decrease of PLAC1 expression levels in MCF-7 cells which cannot be restored by treatment with estradiol (E₂). Moreover, significant higher transcript levels of PLAC1 were found only in ERα-positive human breast cancer samples which also show a NCOA3 overexpression.
CONCLUSIONS
In this study, we identified NCOA3 as a selective co-activator of ERα-mediated transactivation of PLAC1 in MCF-7 breast cancer cells. Our data introduce PLAC1 as novel target gene of NCOA3 in breast cancer, supporting the important role of both factors in breast cancer biology.
背景
胎盘特异性 1（PLAC1）基因编码一种膜相关蛋白，该蛋白在胎盘合体滋养层中特异性表达，并在胚胎发育过程中的鼠胎儿组织中表达。与所有其他成人正常组织中的转录抑制相反，PLAC1 在多种人类癌症中经常被激活并高度表达，特别是在乳腺癌中，它与雌激素受体α（ERα）阳性相关。在先前的研究中，我们表明乳腺癌细胞中的 ERα 信号通过非经典途径转激活 PLAC1 的表达。由于 p160/核受体共激活剂（NCOA）家族的成员 NCOA1、NCOA2 和 NCOA3 在乳腺癌中过度表达，并且本质上参与雌激素介导的癌细胞增殖，我们询问这些蛋白是否参与 ERα 介导的乳腺癌细胞中 PLAC1 的转激活。
方法
应用实时定量 RT-PCR（qRT-PCR）、Western Blot 分析和染色质免疫沉淀，我们分析了 NCOA1、NCOA2、NCOA3 在 MCF-7 和 SK-BR-3 乳腺癌细胞系中 ERα 介导的 PLAC1 转激活中的作用。RNAi 介导的 NCOA3 沉默、qRT-PCR、Western blot 分析和 ERα 激活测定用于更详细地研究 NCOA3 在 ERα 介导的 PLAC1 调节中的作用。通过 qRT-PCR 检查 48 个人乳腺癌样本中 NCOA3 和 PLAC1 的转录表达，并使用 Student's t 检验进行统计分析。
结果
我们仅在 ERα 阳性 MCF-7 细胞中检测到选择性募集 NCOA3，但在 ERα 阴性 SK-BR-3 乳腺癌细胞中未检测到 NCOA1 或 NCOA2 募集到 PLAC1 启动子。此外，我们证明沉默 NCOA3 可导致 MCF-7 细胞中 PLAC1 表达水平显着降低，而用雌二醇（E₂）处理不能恢复。此外，仅在 ERα 阳性的人乳腺癌样本中发现 PLAC1 的转录水平显着升高，这些样本也表现出 NCOA3 的过表达。
结论
在这项研究中，我们确定 NCOA3 是 MCF-7 乳腺癌细胞中 ERα 介导的 PLAC1 转激活的选择性共激活剂。我们的数据将 PLAC1 作为 NCOA3 在乳腺癌中的新靶基因引入，支持这两个因素在乳腺癌生物学中的重要作用。
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