As shown in Figure S1A, compared with MCF7 (ER‐positive breast cancer cell line) and MDA‐MB‐468 (GPER‐positive TNBC cell line), ERα, ERβ, and GPER were significantly either very low or not expressed in NFs, BT549, and MDA‐MB‐231 cells. Here, ESR1 is linked to breast cancer.