ABCG2 was discovered in 1998 by three independent research groups, receiving different names based on the biological model, including BCRP, because of its identification in a breast cancer cell line (Doyle et al., 1998[13]), MXR from resistance caused by mitoxantrone (Miyake et al., 1999[35]) and ABCP, due their presence in placenta (Allikmets et al., 1998[5]). The gene discussed is ABCG2; the disease is breast cancer.