ESR1 and breast cancer: MICAL‐L2, a protein that regulates the transport of adhesion molecules and promotes cell–cell adhesion in epithelial cells, also promotes the malignant progression in an ERβ‐dependent manner, mediating cell proliferation and invasion and further inhibiting tamoxifen sensitivity on ER+ breast cancer cells, through the activation of the AKT/mTOR pathway (Fig. 5) [75].