The HDAC families consist of four classes (I, II, III, and IV), and the subgroups of II constitutes IIa (HDAC4, 5, 7, and 9) and IIb (HDAC6 and 10) [6], one of which HDAC4 has been found linked with malignant phenotypes of ESCC [7]. The gene discussed is HDAC4; the disease is esophageal squamous cell carcinoma.