The roles of MKP-4 in oral squamous cell carcinoma cells

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Mitogen-activated protein kinase (MAPK) pathway is one of the most important cell signaling pathway. Many crucial cellular activities are controlled by the MAPK pathways including cell proliferation, differentiation, and apoptosis. This is also the reason for MAPK pathway needs to be tightly regulated. MAPK phosphatases (MKPs) are dual specificity phosphatases that able to remove the phosphor group of activated MAPK. MKP-4, known as dual-specificity phosphatase-9, belongs to the MKP family and is characterized to dephosphorylate p38 MAPK. Previous study In our laboratory showed the expression level of MKP-4 was decreased in the oral squamous cell carcinoma (OSCC) cell line that transient expressing Insulin-like growth factor binding protein (IGFBP) -5, a tumor suppressor found by our laboratory. Further investigation of the relation between MKP-4 and OSCC is the main target of this research. A MKP-4 expressing plasmid was constructed and transfected into OECM-1 and SAS OSCC cell lines. Cells expressed high MKP-4 had inactivation of p38 MAPK. The phenotypes of cell proliferation, migration, and anchorage-independence growth were observed after the transfection. As a result, MKP-4 induced cell proliferation and migration of both OECM-1 and SAS, but not anchorage-independence growth. The induction of proliferation and migration may enhance the development of neoplasms. Experiment results also showed MKP-4 causes the enhancement of OSCC proliferation and migration through p38 MAPK inactivation.