ESR1 and breast cancer: We identified vascular cell adhesion molecule (VCAM)‐1 as a niche‐derived, chemoprotective factor and demonstrated that targeting integrin‐β1‐VCAM‐1 interactions sensitizes DTCs to chemotherapy, substantially decreases DTC burden in vivo, and prevents bone metastases in an estrogen receptor‐positive (ER+) model of breast cancer metastasis [5].