However, we and others demonstrated that G-1 abrogates the proliferation of both MCF-7 (ER/GPER1-positive) and MDA-MB-231 (ER/GPER1-negative) breast cancer cells, with more substantial effects on MDA-MB-231 cells than on MCF-7 cells [6,14]. This evidence concerns the gene ESR1 and breast carcinoma.