HDAC9 and hepatocellular carcinoma: Romidepsin (depsipeptide, ISTODAX), the second HDAC inhibitor for HDAC1 and HDAC2 that is approved for the treatment of CTCL, inhibits the growth of HCC cells by inducing cell cycle arrest and apoptosis in vivo via ERK/MAPK signaling and c-Jun N-terminal kinase (JNK)/c-Jun signaling pathway [54,55,56].