␣5␤1 Integrin Protects Intestinal Epithelial Cells from Apoptosis through a Phosphatidylinositol 3-kinase and Protein Kinase B– Dependent Pathway Materials and Methods Cell Cultures Stable Transfectants Evaluating the Expression of Integrin Subunits Tunel Assay by Flow Cytometry Annexin V Assay Plat