CDKN1A and hepatocellular carcinoma: We further examined the levels of cell cycle regulators in URGCP/URG4-transduced HCC cells at the protein and mRNA level, and found that p21Cip1 and p27Kip1 were downregulated, whereas the expression of cyclin D1 was upregulated in URGCP/URG4-overexpressing cells, in comparison with control cells (Figure 4A and 4B).