Department of Surgery, Washington University School of Medicine, Campus Box 8109, 660 South Euclid Avenue, St, Louis, Missouri 63110, USA.
Breast Cancer Res. 2011;13(6):R124. doi: 10.1186/bcr3070. Epub 2011 Dec 1.
EpCAM is a cell-surface glycoprotein that is overexpressed in the majority of epithelial carcinomas. However, the functional role of EpCAM in regulating cancer invasion remains controversial, and the mechanism(s) underlying EpCAM-mediated regulation of breast cancer invasion remain to be defined.
EpCAM expression was manipulated in breast cancer cell lines using RNA interference and cDNA expression constructs. Recombinant EpCAM was used to rescue EpCAM signaling following specific ablation of EpCAM. Protein and gene expression, invasion, transcription factor activity, and protein phosphorylation were measured using standard molecular biology techniques.
In loss-of-function, and gain-of-function experiments we demonstrate that EpCAM expression is associated with increased breast cancer invasion in vitro and in vivo. We demonstrate further that specific ablation of EpCAM expression is associated with decreased activator protein-1 (AP-1) transcription factor activity. Phosphoprotein analyses confirm that specific ablation of EpCAM is associated with decreased phosphorylation of the AP-1 subunit c-Jun. Recombinant soluble extracellular EpCAM (rEpCAM) is able to rescue invasion, AP-1 transcription factor activity, and c-Jun phosphorylation in a dose-dependent fashion. Pharmacologic inhibitors, and constitutively active constructs of the c-Jun N-terminal kinase (JNK) signal transduction pathway, suggest that the impact of EpCAM expression on AP-1 transcription factor activity is mediated through the JNK pathway. In functional rescue experiments, forced expression of c-Jun rescues invasion in breast cancer cells following specific ablation of EpCAM.
These data demonstrate for the first time that EpCAM expression can influence the JNK/AP-1 signal transduction pathway, and suggest that modulation of AP-1 transcription factor activity contributes to EpCAM-dependent breast cancer invasion. These data have important implications for the design and application of molecular therapies targeting EpCAM.
EpCAM 是一种细胞表面糖蛋白，在大多数上皮性癌中过度表达。然而，EpCAM 在调节癌症侵袭中的功能作用仍存在争议，并且 EpCAM 介导的乳腺癌侵袭调节的机制仍有待确定。
使用 RNA 干扰和 cDNA 表达构建体在乳腺癌细胞系中操纵 EpCAM 的表达。使用重组 EpCAM 来挽救 EpCAM 信号，在 EpCAM 特异性缺失后。使用标准分子生物学技术测量蛋白质和基因表达、侵袭、转录因子活性和蛋白质磷酸化。
在功能丧失和功能获得实验中，我们证明 EpCAM 的表达与体外和体内乳腺癌侵袭的增加有关。我们进一步证明 EpCAM 表达的特异性缺失与激活蛋白-1(AP-1)转录因子活性的降低有关。磷酸蛋白分析证实，EpCAM 的特异性缺失与 AP-1 亚基 c-Jun 的磷酸化减少有关。重组可溶性细胞外 EpCAM(rEpCAM)能够以剂量依赖性方式挽救侵袭、AP-1 转录因子活性和 c-Jun 磷酸化。c-Jun N 末端激酶(JNK)信号转导途径的药理学抑制剂和组成型激活构建体表明，EpCAM 表达对 AP-1 转录因子活性的影响是通过 JNK 途径介导的。在功能挽救实验中，c-Jun 的强制表达在 EpCAM 特异性缺失后挽救了乳腺癌细胞的侵袭。
这些数据首次证明 EpCAM 表达可以影响 JNK/AP-1 信号转导途径，并表明 AP-1 转录因子活性的调节有助于 EpCAM 依赖性乳腺癌侵袭。这些数据对于设计和应用针对 EpCAM 的分子治疗具有重要意义。
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