ESR1 and breast cancer: Several studies have profiled the whole‐genome effects of 1,25D in breast cancer model systems including non‐transformed cell lines (hTERT‐HME1, HME, MCF10A), human breast cancer cell lines representative of ER+ (MCF7), HER2+ (SKBR3), and Triple Negative (MDA‐MB‐231, SUM159, Hs578T), and patient explants.