The Role of Integrin αV in Oral Cancer

Background: Oral cancer constitutes 2-3% of carcinomas worldwide and results in more than 128,000 deaths each year. The most common form of oral cancer, squamous cell carcinoma (OSCC), is derived from the oral epithelium. Invasive OSCC is extremely destructive with high metastatic potential due to the high vasculature within the oral cavity. SOX-11 is a transcription factor that has been shown to be up-regulated in cancer and recent studies in our lab have suggested an increase in SOX-11 expression in higher invasive oral cancer cells. By using proteomic analysis, we have also demonstrated that knockdown of SOX-11 inhibited the expression of integrin αV (ITGAV) in oral cancer cells. However, the role and expression of ITGAV in oral cancer are not known. Objectives: The objective of our research is to investigate if SOX-11 regulates the expression of ITGAV in oral cancer cells and to examine the role of ITGAV in oral cancer. We will also demonstrate the differential expression of ITGAV among normal human oral keratinocytes (NHOK), and high and low invasive cancer cells. Methods: Both SOX-11 and ITGAV expression in high (UM1 and UM5) and low (UM2 and UM6) invasive cells were measured using western blotting and qPCR. Chromatin immunoprecipitation (ChIP) assay and siRNA knockdown were used to examine if SOX-11 regulates ITGAV expression in oral cancer cells. Invasion, migration, and proliferation assays were performed to evaluate if ITGAV plays an important role in oral cancer cell proliferation and invasion. Results: In silico analysis through the Genematix software suite and MatInspector identified one potential binding site of SOX-11 to the promoter region of ITGAV at 90% confidence. However, twelve additional SoxC group binding sites were located and cross regulation within the SoxC group has been noted in other genes. ChIP assay showed SOX-11 binds to the promoter region of ITGAV gene. After SOX-11 knockdown with siRNA (90% efficiency), ITGAV showed a 40% decrease matching to our previous finding by LC-MS/MS. Next, both western blotting and qPCR showed a significant over-expression of ITGAV (p < 0.01) in highly invasive cancer cells (UM1 and UM5) when compared to low-invasive cancer cells (UM2 and UM6). ITGAV was knocked down in invasive UM1 (95% knockdown) and UM5 (63% knockdown) with siRNA and phenotypic studies were preformed. Wound healing assay showed a 33.1% (UM1) and 40.8% (UM5) decrease in migration capability (p < 0.001), invasion assay showed a 68% (UM1) and 65% (UM5) decrease in invasion potential (p < 0.05), and proliferation assay showed a decreasing proliferation trend in the knockdown group with significant decrease at day 2 and 3 (UM1) and day 2 and 4 (UM5) (p < 0.05).Conclusions: SOX-11 is a transcription factor that binds to the promoter region of ITGAV gene and may regulate the expression of ITGAV in oral cancer cells. ITGAV is significantly over-expressed in highly invasive cancer cells compared to low invasive cancer cells and may play an important role in oral cancer cell migration and invasion