ESR1 and breast cancer: At present, the main treatment for breast cancer patients is to inhibit the expression of ERα gene using anti-hormone therapy, and then control the estrogen level in patients through the modulation of estrogen receptor activity, so as to achieve the inhibition of breast cancer spread and malignant trend, and gradually combine drugs and radiochemotherapy to achieve effective treatment of breast cancer (Ali and Coombes, 2002; Mohla et al., 2009; Huang et al., 2015).