PTTG1 and hepatocellular carcinoma: Reduced KLF6 expression occurs at early stages during HCC progression, which is attributable to control cell growth and apoptosis by regulation of multiple target genes, such as tumor suppressor genes (p21, E-cadherin, p53), oncogenes (Rb, β-catenin, pituitary tumor-transforming gene 1 (PTTG1), mouse double minute 2 homolog (MDM2)), pro-apoptosis gene (Bax) and anti-apoptosis gene (Bcl-xL)19, 22, 29.