HDAC9 and hepatocellular carcinoma: Additional to chemotherapeutic agents, different type of drugs that show synergy with TRAIL in HCC have been identified, and these include histone deacetylase (HDAC) inhibitors [92], proteasome inhibitors as bortezomib [64], kinase inhibitors, such as sorafenib [71] and natural compound (for more information see Table 2).