At least 48 human ABC transporters have been described, however only three have been linked to a role in mutidrug drug resistance (MDR) to anti-cancer, anti-inflammatory and anti-viral drugs [8]: the multidrug resistance associated protein 1 (MRP1 or ABCC1), the breast cancer resistance protein (BCRP or ABCG2) and P-gp also called transmembrane small-molecule pump (ABCB1). The gene discussed is ABCG2; the disease is cancer.