CDKN1A and hepatocellular carcinoma: Molecular carcinogenesis of HCC could be variable due to either inactivation or loss of tumor suppressor genes such as cyclin-dependent kinase inhibitor 1A (P21, Cip1), tumor protein p53 (TP53), retinoblastoma (RB) and phosphatase and tensin homolog (PTEN) and/or activation of oncogenes including protein kinase B (PKB) and neuroblastoma Ras (N-Ras) [12, 13].