We generated stable cell lines with FRG1 level modulation in MCF7 (estrogen receptor positive cells; ER+) cells that harbors moderate expression of endogenous FRG1 and MDA‐MB‐231 (Triple negative breast cancer cells; TNBC) cells that has the basal level of endogenous FRG1. The gene discussed is ESR1; the disease is breast carcinoma.