Many studies have reported the differential expression of specific HDAC isoforms in a variety of hematological or solid malignancies and cell lines, such as lymphoma [14], breast [15], gastric [16], colorectal [17], and lung cancers [18], hepatocellular carcinoma [19], and cholangiocarcinoma [20]. The gene discussed is HDAC9; the disease is cholangiocarcinoma.