ESR1 and breast cancer: Recently, these drugs have been exploring the potential role in patients with estrogen receptor (ER) positive BCBM.112 A phase II study is evaluating the safety and activity of abemaciclib in hormone receptor (HR) positive BCBM and lung cancer or melanoma with BM.113 Vimentin and Snail, known as the EMT markers, could be downregulated with palbociclib treatment,114 supporting its inhibition of migration and invasion of breast cancer cells.