This study focused on the evaluation of the effects of new synthetic methoxy-stilbenes with 3,4, and 5 methoxy groups in the positions 3,4,2′,4′,6′ of stilbene ring, respectively, on the expression of genes encoding proteins involved in estrogen signaling and metabolism in two breast cancer cell lines: benign MCF7 and metastatic (ER-negative) MDA-MB-231. The gene discussed is ESR1; the disease is breast cancer.