However, in addition to the binding to ERs, in human breast cancer cell lines quercetin activates signaling pathways through the G-protein-coupled receptor GPR30 (Maggiolini et al., 2004); also, in murine small intestine quercetin activates an opioid receptor (Gim et al., 2015) decreasing amplitudes and frequencies of pacemaker activity of interstitial cells of Cajal. This evidence concerns the gene GPER1 and breast cancer.