Since its discovery and initial characterization [23], JIB-04 has been used as an inhibitor of the H3K9/K36 demethylase activity of KDM4A in leukemia [48], the H3K9 demethylase activity of KDM3B in lung cancer [49], and the H3K4 demethylase activity of members of the KDM5 family in breast cancer and glioblastoma [50, 51]. Here, KDM3B is linked to breast cancer.