Expression of Tyrosine Kinase Receptor 2 in Oral Squamous Cell Carcinoma and the Effect on Cell Proliferation and Migration and Epithelial-Mesenchymal Transition Process

  Objective  To study the expression of tyrosine kinase receptor 2 (Tie2) in oral squamous cell carcinoma (OSCC) and its effect on cell proliferation and migration and the epithelial-mesenchymal transition (EMT) process.

  Methods  Immunohistochemistry (IHC) tests were conducted to examine the expression of Tie2 in OSCC tissues and normal oral mucosa tissues. Western blot was performed to examine the expression of Tie2 in dysplastic oral keratinocyte (DOK) cell line and OSCC cell lines, and the cell line with high Tie2 expression was selected as the experimental cell line. The Tie2-silenced lentiviral vector was successfully transfected onto the experimental cell line for subsequent experiments. Cell proliferation and cloning abilities were examined with CCK-8 and clone formation assays. Cell migration ability was examined with scratch and Transwell assays. The remodeling ability of cytoskeletal F-actin and the expressions of E-cadherin and N-cadherin were examined with confocal laser scanning microscope. Western blot was performed to examine the expression of EMT-related signature proteins, including E-cadherin, N-cadherin, and vimentin, and the expression of the protein kinase B (AKT) and extracellular signal-regulated kinase (ERK).

  Results   IHC results showed that the Tie2-positive rate of the OSCC group (74.5%) was significantly higher than that of the control group (19.4%) (P<0.0001). The expression of Tie2 was higher in HSC-4 and SCC-9 cell lines compared to that in DOK cells. The lentiviral shRNA-162 group showed the best silencing effect, which was used as the experimental group and applied in subsequent experiments. Compared with those of the control group, the proliferation, cloning and migration capacities of the cells of the experimental group were significantly reduced. Furthermore, the green fluorescence intensity of the cytoskeleton F-actin was reduced, the number of filamentous pseudopods at the leading edge of the cells decreased and their length was shortened, and the expression of E-cadherin was significantly increased, while the expression of N-cadherin and vimentin was significantly reduced in the experimental group in comparison with those of the control group. The expression of p-AKT and p-ERK proteins decreased, while AKT and ERK protein expression increased.

  Conclusion  Tie2 was highly expressed in most OSCC cells. Silencing Tie2 can inhibit the proliferation, cloning, and migration ability of OSCC cells, inhibit F-actin remodeling, and alter the expression of its EMT-related signature proteins by regulating AKT and ERK signaling pathway, which suggests that Tie2 may be involved in the growth, metastasis and EMT process of OSCC.