ESR1 and breast cancer: To agnostically profile AR interacting proteins across ER+ and ER- breast cancer models, four cell lines that encompass three molecular subtypes of breast cancer and have established AR expression were interrogated: ER+ luminal (ZR-75-1, T-47D) and two subtypes of ER- disease including molecular apocrine/HER2 + (MDA-MB-453) and triple negative (i.e., lacking ER, PR and HER2 expression; MFM-223) [22–24].