Furthermore, IPH-926 cells display overexpression of the BC anti-estrogen resistance 4 (BCAR4) gene, which has been linked to hormone-independent tumor cell growth [55,56,57], display overexpression of the MDR1/ABCB1 drug transporter, and actively extrude conventional chemotherapeutic agents, such as doxorubicin, in an MDR1/ABCB1-dependent manner [56]. This evidence concerns the gene ABCB1 and breast cancer.