Overexpression of N-terminal amino acids of p55γ regulatory subunit of PI3K inhibits cell adhesion of human gastric carcinoma MGC803 cells

AIM: To investigate the effect of the N-terminal 24-amino acid(N24) overexpression in p55γ re-gulatory subunit of phosphatidylinositiol 3-kinase(PI3K) on the cell adhesion of human gastric carcinoma cell MGC803.METHODS: MGC803 cells, which stably expressed GFP-N24 fusion protein and GFP alone, were generated by transfection with pEGFPN-24 plasmid and control plasmid pEGFP-C1, respectively. The morphological change of the cells was observed under inverted microscope. The expression of GFP-N24 fusion protein was detected by Western blot. The adhesion of the cells was determined by cell adhesion assay. The effects of GFP-N24 fusion protein on the expression of E-cadherin and β-catenin were analyzed by Western blot. The expression and secretion of matrix metalloproteinase 9(MMP9) and urokinase-type plasminogen activator(uPA) in the MGC803 cells were detected by gelatin zymography.RESULTS: MGC803/GFP-N24 cell line steadily expressed GFP-N24 fusion protein and MGC803/GFP cell line steadily expressing GFP were successfully established, but the expression of fusion protein GFP-N24 was lower than that of the control protein GFP. The morphological changes of the transfected cells from paving stone to fibroblast cell form after gene transfection, and the cytoplasm secretory granules were increased significantly. The cell adhesion to fibronectin and collagen decreased after GFP-N24 transfection. GFP-N24 fusion protein increased the expression of cell adhesion molecule E-cadherin and decreased the wnt signal pathway molecule β-catenin in the MGC803 cells. However, it did not affect the expression and secretion of tumor metastasis-related proteins MMP9 and uPA.CONCLUSION: Overexpression of N24p55γ inhibits cell adhesion by influencing the expression of E-cadherin and β-catenin in the MGC803 cells.