ABCB1 and breast cancer: Moreover, different studies have described organoselenium derivatives with potent activity against triple-negative breast cancer, i.e., a type of breast cancer that lacks estrogen, progesterone and HER2 receptors [9,10], or as adjuvants against resistant breast cancer, i.e., a doxorubicin-resistant subline overexpressing ABCB1 derived from MCF-7 cells [11].