CERS5 and colon carcinoma: To investigate if the barrier function of colon epithelial cells is impaired by CerS5-depletion, we downregulated CerS5 expression in colon carcinoma cells by CerS5-shRNA and assessed the epithelial barrier function by determining the transepithelial electric resistance (TEER) and membrane permeability by a fluorescein isothiocyanate (FITC)-dextran permeability assay.