AICDA and cancer: In a final experiment, the authors show that 17‐AAG treatment prevents AID‐dependent epithelial‐mesenchymal transition (EMT) in a breast cancer cell line, a process that leads to cancer progression and in which cells lose their epithelial features and gain mesenchymal properties, characterized by, for example, higher expression of the cytoskeletal filament Vimentin and the cell adhesion protein N‐cadherin 23.