Identified as endogenous regulatory factors of KDM4B, several microRNAs, such as miRNA-491-5P, have been found to inhibit KDM4B expression by binding to the 3′ UTR of KDM4B mRNA, thereby inhibiting the proliferation of breast cancer and gastric cancer cells (Zeng et al., 2015; Zhang et al., 2018). The gene discussed is KDM4B; the disease is gastric cancer.