ESR1 and breast cancer: Three types of breast cancer cells with distinct characteristics of specifically targeted receptors, including triple-negative MDA-MB-231, estrogen receptor (ER)+/human epidermal growth factor receptor 2 (HER2)− MCF-7, and ER−/HER2+ SK-BR-3 cells, are employed along with lung cancer cells (A549) and pancreatic cancer cells (Panc1).