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