ABCG2 and breast cancer: Inhibition of the PI3K/Akt signaling pathway was recently shown to modulate ABCG2-mediated drug transport via the translocation of ABCG2 from the plasma membrane to intracellular compartments in different cell systems, including side population cells in the bone marrow [40], glioma-derived stem-like cells [41], and ABCG2-overexpressing extracellular vesicles derived from MCF-7 breast cancer cells [42].