EZH2 and breast cancer: Its expression corelates with various cancer stem cell markers, including cell division cycle 2a (Cdc2a), bone gamma-carboxyglutamate protein 1 (Bglap1), aldehyde dehydrogenase 1 (ALDH1), enhancer of zeste homolog 2 (EZH2) and cluster of differentiation 44 (CD44).70,103,104 Increased levels of these stemness markers enhance resistance to chemotherapy in squamous cell carcinoma and promote self-renewal activities in human mammary epithelial cells.105 AXL maintains breast cancer stem cells (BCSCs) and epithelial plasticity through a positive feedback loop.