To determine the role of Zeb1 in breast cancer development, we crossed the floxed Zeb1 allele homozygously into PyMT mice to generate PyMT;Zeb1cKO (MMTV-Cre+/−;PyMT+/−;Zeb1−/−) mice as previously described [50]. Here, ZEB1 is linked to breast carcinoma.