ESR1 and breast cancer: In addition, we used the non-transformed mammary epithelial cell line MCF10A (RASWT immortalized by a spontaneous t(3;9)(3p13;9p22) translocation that deletes the CDKN2A gene, also known as p16) [46, 47] and the non-invasive estrogen receptor (ER) and progesterone receptor (PR) positive RASWT breast cancer cell line MCF7 (wild-type p53) and T47D (mutant p53).