ADAM12-L is also induced during EMT in mammary epithelial cells [12,14-17], is enriched in mammary epithelial cells or breast cancer cells grown in suspension as mammospheres [12,18,19], is up-regulated in residual tumors remaining after endocrine therapy for estrogen receptor (ER)-positive disease [12,19,20], and the level of ADAM12-L expression predicts resistance to chemotherapy in ER-negative breast tumors [12,21-23]. Here, ESR1 is linked to breast cancer.