The role of histone demethylases in tumorigenesis and progression has become more clearly recognized recently, for example, KDM4B is involved in the growth and progression of tumors such as GC, breast cancer, and ovarian cancer (31–33); HPV16 E7 and miR-342-3p stimulate the expression of KDM2A in tumors, and KDM2A then enhances ERK1/2-mediated tumor formation in lung cancer (34–36); KDM4A is abnormally expressed in colorectal cancer, prostate cancer, lung cancer, and breast cancer and promotes their progression (37, 38). The gene discussed is KDM4B; the disease is gastric cancer.