11279

KLF8

Kruppel-like factor 8;KLF8;Kruppel-like factor 8

Krueppel-like factor 8|basic krueppel-like factor 3|basic kruppel-like factor 3|zinc finger protein 741

Xp11.21

protein-coding

Epithelial to mesenchymal transition (EMT) and extracellular matrix degradation are critical for the initiation and progression of tumor invasion. We have recently identified Kruppel-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.

Kruppel-like factor 8 (KLF8) regulates critical gene transcription associated with cancer. The underlying mechanisms, however, remain largely unidentified. We have recently demonstrated that KLF8 expression enhances the activity but not expression of matrix metalloproteinase-2 (MMP2), the target substrate of MMP14. Here, we report a novel KLF8 to MMP14 signaling that promotes human breast cancer invasion and metastasis. Using cell lines for inducible expression and knockdown of KLF8, we demonstrate that KLF8 promotes MMP14 expression at the transcriptional level. Knocking down KLF8 expression inhibited the breast cancer cell invasion both in vitro and in vivo as well as the lung metastasis in mice, which could be rescued by ectopic expression of MMP14. Promoter reporter assays and oligonucleotide and chromatin immunoprecipitations determined that KLF8 activates the human MMP14 gene promoter by both directly acting on the promoter and indirectly via promoting the nuclear translocation of beta-catenin, the expression of T-cell factor-1 (TCF1) and subsequent activation of the promoter by the beta-catenin/TCF1 complex. Inhibition of focal adhesion kinase (FAK) using pharmacological inhibitor, RNA interference or knockout showed that the cell surface presentation of active MMP14 downstream of KLF8 depends on FAK expression and activity. Taken together, this work identified novel signaling mechanisms by which KLF8 and FAK work together to promote the extracellular activity of MMP14 critical for breast cancer metastasis.

Kruppel-like factor 8 (KLF8) is a transcriptional factor critical for metastatic progression of breast cancer. Epithelial stromal interaction 1 (EPSTI1), a recently identified stromal fibroblast-induced gene in non-invasive breast cancer cells is highly overexpressed in invasive breast carcinomas. The function and regulation of EPSTI1, however, remain largely unknown. In this paper, we report a novel KLF8 to EPSTI1 signaling pathway in breast cancer. Using various expression analyses, we revealed a high co-overexpression of KLF8 and EPSTI1 in invasive human breast cancer cells and patient tumors. Ectopic overexpression of KLF8 in the non-invasive MCF-10A cells induced the EPSTI1 expression, whereas KLF8 knockdown from the invasive, MDA-MB-231 cells decreased the EPSTI1 expression. Promoter activation and binding analyses indicated that KLF8 promoted the EPSTI1 expression by directly acting on the EPSTI1 gene promoter. EPSTI1 knockdown dramatically reduced the KLF8-promoted MCF-10A cell invasion, and ectopic expression of EPSTI1 in the non-invasive MCF-7 cells is sufficient to induce the cell invasion. Experiments using nude mice demonstrated that the ectopic EPSTI1 granted the MCF-7 cells capability of both invasive growth in the breasts and metastasis to the lungs. Using co-immunoprecipitation coupled with mass spectrometry, we discovered that EPSTI1 interacts with the valosin-containing protein (VCP), resulting in the degradation of IkappaBalpha and subsequent activation of NF-kappaB in the nucleus. These findings suggest a novel KLF8 to EPSTI1 to VCP to NF-kappaB signaling mechanism potentially critical for breast cancer invasion and metastasis.