In addition, experimental studies indicated that many dietary natural products and their bioactive components showed inhibitory effects on breast cancer (Figure 1), through downregulating ER-α expression and activity, inhibiting proliferation, metastasis and angiogenesis of breast tumor cells, inducing apoptosis and cell cycle arrest, and sensitizing breast tumor cells to radiotherapy and chemotherapy [32,33,34,35]. This evidence concerns the gene ESR1 and breast cancer.