The tumor growth in vivo of hepatoma cells was also reduced in nude mice treated with the HDAC8-specific inhibitor PCI-34051(5 μM) for four weeks (Figure 5E), and the tumor mass in mice treated with PCI-34051 showed lower levels of proliferation marker (Cyclin D1, E2F1, PCNA and Ki 67+) expression than those treated with DMSO (0.1%) (Figure 5F) [28]. This evidence concerns the gene E2F1 and hepatocellular carcinoma.