ATF3 and hepatocellular carcinoma: Of note, opposing effects of ATF3 on cyclin D1 expression have been previously documented: ATF3 binds to AP-1 motif and activates cyclin D1 in mitogen-stimulated mouse hepatoma cells[45], whereas it binds to ATF/CRE site and represses cyclin D1 in mouse fibroblasts stimulated by serum[46].