CD44 and breast cancer: Therefore, suppressing P-gp expression and reducing the population of breast cancer stem cells, characterized by high levels of YB-1 nuclear protein, P-gp, and CD44+/CD24−/low phenotype, which are resistant to various chemotherapeutic drugs such as paclitaxel, doxorubicin, and vincristine, could potentially reverse MDR in breast cancer cells [44,66].