ESR1 and triple-negative breast carcinoma: We focused on these cells because they are a highly aggressive, invasive, and poorly differentiated triple-negative breast cancer (TNBC) cell line that lacks the estrogen receptor (ER), progesterone receptor, as well as amplification of the human epidermal growth factor receptor 2 (HER2) and is one of the triple-negative basal subtype cell line most widely used in MBC research (32) (40.2% of total PubMed citations).