CIZ1 and breast carcinoma: Full-length CIZ1, detected by a monoclonal antibody to a C-terminal epitope, clearly localizes to the Xi in MCF-7 cells, though in line with reports that Xi in breast cancer-derived cells is a less discrete (compact) entity than in ‘normal’ cells [23] Xi staining is markedly irregular, and also accompanied by the nucleus wide signal that is typical of CIZ1 [9].