HDAC9 and hepatocellular carcinoma: Taken together, frequent downregulation of miR-497 and miR-195 expression occurred not mainly by genomic loss, DNA hypermethylation or altered miRNA biogenesis, but at least partly through repressive histone modifications in the HCC cell lines examined, although HDAC inhibitor had little or no effect on the expression and the epigenetic factors contributing to the downregulation remain to be clarified.