Treatment with D1R agonists (SKF38393, A68930, A77636, fenoldopam) was shown to dramatically suppress the viability of triple-negative breast cancer cell lines (MDA-MB-231, MDA-MB-468, SUM149) and hormonal breast cancer cell line (BT-20) without affecting the proliferation of normal breast epithelium [52,55,65]. This evidence concerns the gene DRD1 and breast cancer.