Epirubicin is an anthracycline commonly used for the treatment of breast cancer.12 Upon epirubicin treatment, FOXM1 is primarily downregulated at the post-translational level in breast cancer cells.8, 13, 14 In line with this, we have recently shown that in response to epirubicin treatment, FOXM1 is modified through SUMOylation, which leads to its ubiquitination and degradation via the proteasome proteolytic pathway.15 A novel subgroup of E3-ligases called SUMO-targeted Ubiquitin E3-ligases (STUbLs) provide a link for cross-talks between the SUMO and ubiquitin pathways. Here, FOXM1 is linked to breast cancer.