Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32827, USA.
Oncogene. 2011 Apr 21;30(16):1901-11. doi: 10.1038/onc.2010.563. Epub 2010 Dec 13.
Epithelial to mesenchymal transition (EMT) and extracellular matrix degradation are critical for the initiation and progression of tumor invasion. We have recently identified Krüppel-like factor 8 (KLF8) as a critical inducer of EMT and invasion. KLF8 induces EMT primarily by repressing E-cadherin transcription. However, how KLF8 promotes invasion is unknown. Here, we report a novel KLF8-to- matrix metalloproteinase (MMP)9 signaling that promotes human breast cancer invasion. To identify the potential KLF8 regulation of MMPs in breast cancer, we established two inducible cell lines that allow either KLF8 overexpression in MCF-10A or knockdown in MDA-MB-231 cells. KLF8 overexpression induced a strong increase in MMP9 expression and activity as determined by quantitative real-time PCR and zymography. This induction was well correlated with the MMP inhibitor-sensitive Matrigel invasion. Conversely, KLF8 knockdown caused the opposite changes that could be partially prevented by MMP9 overexpression. Promoter-reporter assays and chromatin and oligonucleotide precipitations determined that KLF8 directly bound and activated the human MMP9 gene promoter. Three-dimensional (3D) glandular culture showed that KLF8 expression disrupted the normal acinus formation, which could be prevented by the MMP inhibitor, whereas KLF8 knockdown corrected the abnormal 3D architecture, which could be protected by MMP9 overexpression. KLF8 knockdown promoted MDA-MB-231 cell aggregation in suspension culture, which could be prevented by MMP9 overexpression. KLF8 knockdown inhibited the lung metastasis of MDA-MB-231 cells in nude mice. Immunohistochemical staining strongly correlated the co-expression of KLF8 and MMP9 with the patient tumor invasion, metastasis and poor survival. Taken together, this work identified the KLF8 activation of MMP9 as a novel and critical signaling mechanism underlying human breast cancer invasion and metastasis.
上皮间质转化（EMT）和细胞外基质降解对于肿瘤侵袭的发生和进展至关重要。我们最近发现 Kruppel 样因子 8（KLF8）是 EMT 和侵袭的关键诱导因子。KLF8 通过抑制 E-钙黏蛋白转录来诱导 EMT。然而，KLF8 如何促进侵袭尚不清楚。在这里，我们报告了一种新的 KLF8 到基质金属蛋白酶（MMP）9 信号通路，该通路促进人乳腺癌侵袭。为了鉴定 KLF8 在乳腺癌中对 MMPs 的潜在调控作用，我们建立了两个诱导细胞系，使 MCF-10A 细胞中 KLF8 过表达或 MDA-MB-231 细胞中 KLF8 敲低。定量实时 PCR 和明胶酶谱法测定，KLF8 过表达诱导 MMP9 表达和活性强烈增加。这种诱导与 MMP 抑制剂敏感的 Matrigel 侵袭密切相关。相反，KLF8 敲低导致相反的变化，这些变化可以部分被 MMP9 过表达所阻止。启动子报告分析、染色质和寡核苷酸沉淀确定 KLF8 直接结合并激活人 MMP9 基因启动子。三维（3D）腺泡培养显示，KLF8 表达破坏了正常的腺泡形成，MMP 抑制剂可阻止这一过程，而 KLF8 敲低纠正了异常的 3D 结构，MMP9 过表达可保护这一结构。KLF8 敲低促进 MDA-MB-231 细胞在悬浮培养中的聚集，而 MMP9 过表达可阻止这一过程。KLF8 敲低抑制 MDA-MB-231 细胞在裸鼠中的肺转移。免疫组织化学染色强烈显示 KLF8 和 MMP9 的共表达与患者肿瘤侵袭、转移和不良预后密切相关。总之，这项工作确定了 KLF8 对 MMP9 的激活是人类乳腺癌侵袭和转移的一种新的关键信号机制。
