ABCG2 and breast cancer: Among the delivered proteins are frequently described ATP-binding cassette (ABC) family, like P-glycoprotein (P-gp, MDR1, and ABCB1), breast cancer (BC)-resistant proteins (ABCG2, BRCP, and ABCA3), and multidrug-resistant protein 1 (MRP-1) (45, 46, 68–72).