Department of Biomedicine, University of Basel, Basel, Switzerland.
PLoS One. 2013;8(2):e57329. doi: 10.1371/journal.pone.0057329. Epub 2013 Feb 25.
We have identified the zinc-finger transcription factor Kruppel-like factor 4 (Klf4) among the transcription factors that are significantly downregulated in their expression during epithelial-mesenchymal transition (EMT) in mammary epithelial cells and in breast cancer cells. Loss and gain of function experiments demonstrate that the down-regulation of Klf4 expression is required for the induction of EMT in vitro and for metastasis in vivo. In addition, reduced Klf4 expression correlates with shorter disease-free survival of subsets of breast cancer patients. Yet, reduced expression of Klf4 also induces apoptosis in cells undergoing TGFβ-induced EMT. Chromatin immunoprecipitation/deep-sequencing in combination with gene expression profiling reveals direct Klf4 target genes, including E-cadherin (Cdh1), N-cadherin (Cdh2), vimentin (Vim), β-catenin (Ctnnb1), VEGF-A (Vegfa), endothelin-1 (Edn1) and Jnk1 (Mapk8). Thereby, Klf4 acts as a transcriptional activator of epithelial genes and as a repressor of mesenchymal genes. Specifically, increased expression of Jnk1 (Mapk8) upon down-regulation of its transcriptional repressor Klf4 is required for EMT cell migration and for the induction of apoptosis. The data demonstrate a central role of Klf4 in the maintenance of epithelial cell differentiation and the prevention of EMT and metastasis.
我们在乳腺上皮细胞和乳腺癌细胞的上皮-间充质转化（EMT）过程中表达显著下调的转录因子中鉴定出锌指转录因子 Kruppel 样因子 4（Klf4）。功能丧失和获得实验表明，Klf4 表达下调是体外诱导 EMT 和体内转移所必需的。此外，Klf4 表达减少与乳腺癌患者亚组无病生存时间缩短相关。然而，Klf4 的表达减少也会诱导 TGFβ诱导的 EMT 中细胞凋亡。染色质免疫沉淀/深度测序与基因表达谱相结合揭示了直接的 Klf4 靶基因，包括 E-钙粘蛋白（Cdh1）、N-钙粘蛋白（Cdh2）、波形蛋白（Vim）、β-连环蛋白（Ctnnb1）、血管内皮生长因子-A（Vegfa）、内皮素-1（Edn1）和 Jnk1（Mapk8）。因此，Klf4 作为上皮基因的转录激活因子和间充质基因的抑制因子发挥作用。具体而言，下调其转录抑制剂 Klf4 后 Jnk1（Mapk8）的表达增加是 EMT 细胞迁移和诱导凋亡所必需的。这些数据表明 Klf4 在维持上皮细胞分化和防止 EMT 和转移方面发挥着核心作用。
