FIGURE 4.

TF CEBPB regulates the expression of FXR in colon cancer cells by directly binding FXR promoter. (A) The upstream genes of FXR were predicted by hTFtarget and PROMO databases. (B) The expression of CEBPB protein was analyzed using UALCAN (http://ualcan.path.uab.edu/index.html). (C) The correlation of CEBPB expression in TCGA database and colon cancer was analyzed utilizing bioinformatics method. (D) Levels of CEBPB in four strains of colon cancer cell lines (HCT116, SW620, HT‐29, SW480) and one strain of human normal colon cancer cell line CCD‐18Co. (E) ChIPBase and JASPER databases were adopted to predict the putative binding site of CEBPB on FXR. (F) The diagram demonstrating the FXR promoter region using different primers for amplication. Region 2 and Region 3 both contain one CEBPB binding site, while Region 1 that excludes CEBPB binding site is taken as a negative control. (G) The relationship between CEBPB and FXR promoter. (H) si‐CEBPB is constructed, and then co‐transfected with the firefly luciferase vector containing either wild or mutation FXR promoter. pRL‐SV40 containing Renilla luciferase is taken as a control plasmid. The firefly luciferase and Renilla luciferase ratio are utilized to check the viability of promoters. The test is repeated three times on each sample. (I) oe‐CEBPB is constructed, and then co‐transfected with the firefly luciferase vector containing either wild or mutation FXR promoter. pRL‐SV40 containing Renilla luciferase is taken as a control plasmid. The firefly luciferase‐Renilla luciferase ratio is utilized to check the viability of promoters. The test is repeated three times.* p < 0.05