To know the mechanism underlying the induction of p57 expression by C/EBPβ, we analyzed the promoter activity of p57 using human hepatoma HuH-7 cells and ATDC5 cells transfected with a luciferase reporter gene construct containing the 5′-flanking sequences from −1,092 to +226 bp of the p57 promoter (Figure 5A). Here, CEBPB is linked to hepatocellular carcinoma.