ALDH1A1 and breast cancer: Compared with other subtypes of breast cancer, CLBC has high expression of EMT-related markers (such as Vimentin, SNAI1 and SNAI2, TWIST1 and TWIST2, and ZEB1 and ZEB2) (114) and breast cancer stem cells/tumors with the initial cell markers ALDH1 and CD44hi/CD24-/low (115, 117) and high expression of PD-L1 (122).