SOX9 negatively regulates CLDN8 in colonic epithelial cells by binding CLDN8 promoter. a and b, Luciferase reporter assays in Caco-2 and NCM460 cells. & P < 0.0001 compared with pGL3-basic + pcDNA3.1-Flag group; # P < 0.0001 compared with pGL3-CLDN8 + pcDNA3.1-Flag group. c, The putative SOX9-binding sites located within the CLDN8 promoter region targeted by the ChIP primers. d and e, ChIP-qPCR analysis in Caco-2 and NCM460 cells. ChIP-qPCR shows SOX9 occupancy on the CLDN8 promoter region compared with immunoglobulin-G (IgG). All Data are shown as means ± SEM in (a), (b), (d) and (e). Student's t-test and one-way ANOVA were used for comparison, respectively.