MT1-MMP Induces An Epithelial To Mesenchymal Transition And Promotes Invasion And Metastasis Ability In Oral Squamous Cell Carcinoma

Tissue invasion and metastasis are acquired abilities of cancer and related to the deathin oral squamous cell carcinoma (OSCC). Emerging observations indicate that theepithelial-to-mesenchymal transition (EMT) is associated with tumor progression.Membrane Type1Matrix Metalloproteinase (MT1-MMP) is a cell surface proteinasein an active form, which is known as one of the factors that influence the pericellularmicroenvironment. MT1-MMP is involved in degrading extracellular matrixcomponents that can promote tumor invasion and cell migration.Objective: In this study, we intend to investigate the role of MT1-MMP in inducingEMT and promoting tumor cell invasion and metastasis in OSCC.Methods: First, the eukaryotic expression vector pEGFP-N1-MT1-MMP wasconstructed. We utilized SCC9cells stably transfected with an empty vector(SCC9-N) or a vector encoding human MT1-MMP (SCC9-M) to study the role ofMT1-MMP in EMT development. Real-time RT-PCR, western blotting,immunofluorescence microscopy were used to detect the changes of the epithelial andmesenchymal markers. Adhesion, invasion and wound-healing assay were performedto measure the biological properties of the cells. Next, the CSC-like characteristics inSCC9-M cells were evaluated by flow cytometry, MTT, colony-forming assay.Furthermore, we utilized SCC25cells transfected with a vector with a scrambledmiRNA sequences (SCC25-mock) as experiment control or the most effectivelentivirus-miRNA interference vector (SCC25-miRNA-M) to downregulation ofMT1-MMP. Real-Time RT-PCR, western blotting, transwell invasion assay were performed to further determine the role of MT1-MMP in oral cancer cell invasion.Results: First, the eukaryotic expression vector pEGFP-N1-MT1-MMP wasconstructed. Upon up-regulation of MT1-MMP, SCC9-M cells underwent EMT, inwhich they presented a fibroblast-like phenotype and had a decreased expression ofepithelial markers (E-cadherin, cytokeratin18and β-catenin) and an increasedexpression of mesenchymal markers (vimentin and fibronectin). We furtherdemonstrated that MT1-MMP-induced morphologic changes increased the level ofTwist and ZEB, and were dependent on repressing the transcription of E-cadherin.These activities resulted in low adhesive, high invasive abilities of the SCC9-M cells.Next, MT1-MMP-induced transformed cells exhibited cancer stem cell (CSC)-likecharacteristics, such as low proliferation, self-renewal ability, resistance tochemotherapeutic drugs and apoptosis, and expression of CSCs surface markers.Furthermore, upon downregulation of MT1-MMP in SCC25cells caused a decreasedlevel of MMP-2, MMP-9and MMP-13. Meanwhile, up-regulation of MT1-MMP inSCC9cells could also activate the expression of MMP-2, MMP-9and MMP-13. Thisresult revealed that oral cancer cell MT1-MMP expression was associated with theexpression of MMP-2, MMP-9and MMP-13. Downregulation of MT1-MMP inSCC25cells caused the more aggressive cancer cells decreased the invasive ability.By contrast, the less aggressive SCC9cells obtained high invasive ability byoverexpression of MT1-MMP. This data demonstrated that cancer cell MT1-MMPexpression affected the invasive ability of cancer cells.Conclusions: Our study indicates that overexpression of MT1-MMP induces an EMTand promotes cancer cell invasion and metastasis in OSCC. This phenotypetransformation results in the acquisition of CSC-like properties in SCC9cells. Oralcancer cell MT1-MMP is correlated with the expression of MMP-2, MMP-9andMMP-13, affects cancer cell invasion, and leads to a remodeling of the tumor microenvironment. These aspects of MT1-MMP function in cancer invasion andmetastasis are giving our approaches to a better understanding of OSCC therapy.