ALDH1A1 has previously been reported as a CSC marker in ovarian and breast cancers [56–58], and the Li et al. study revealed that EZH2 directly increased ALDH1A1 expression in ovarian cancer cells, supporting the notion that EZH2 can increase the proportion of CSCs by promoting ALDH1A1 expression. This evidence concerns the gene EZH2 and breast cancer.