To further investigate the generalized effects of ATP-driven chemoresistance in breast cancer, we performed a CCK-8 assay in triple-negative breast cancer MDA-MB-231 cells and estrogen receptor (ER)-positive breast cancer MCF-7 cells treated with standard chemotherapy drugs for breast carcinomas, such as cisplatin, doxorubicin, paclitaxel, and gemcitabine [26] at the concentration of each drugs’ IC50 at 48 h, with or without 100 μM extracellular ATP, a concentration that induced significant chemoresistance in our previous study [14]. This evidence concerns the gene ESR1 and breast cancer.