MUC1 and breast cancer: Similarly, quercetin inhibits breast cancer stem cells by reducing the expression of chemokine receptor type 4 (CXCR4), mucin 1 (MUC1), aldehyde dehydrogenase 1A1 (ALDH1A1), and epithelial cell adhesion molecule (EpCAM) both in vitro and in vivo, while also preventing tumor metastasis in the CD44+/CD24− population and downregulating estrogen receptor α and PI3K/Akt/mTOR signaling pathways [65].