CDKN1A and hepatocellular carcinoma: First, we examined p21cip1 mRNA expression in our HCC patient samples, and p21cip1 expression was down-regulated in tumor tissues compared with their normal counterparts (Fig. 7a; 1.20 ± 1.38 vs 2.20 ± 1.51 for tumors vs non-tumorous tissues, P = 0.0035).