These cell lines were chosen to represent three different types of breast cancers, viz., MDA-MB-231, triple negative and highly aggressive metastatic adenocarcinoma [48]; T47DA18, estrogen receptor positive and invasive ductal carcinoma [50]; MCF7, estrogen receptor positive but non-aggressive metastatic adenocarcinoma [49]. Here, ESR1 is linked to invasive ductal breast carcinoma.