In some studies, ithas been proven that HDAC enzymes play an active role in many cancertypes, such as gastrointestinal,7 breast,8,9 lymphoblastic and myeloid leukemia,10,11 pancreas,12 and lung cancer.13 Histone deacetylases are highly expressed in both normal cholangiocytesand cholangiocarcinoma.14 Although theeffects of HDACis are studied in CCA, not much is known about theirmechanism. Here, HDAC9 is linked to cholangiocarcinoma.