ABCG2 and cancer: BCRP (ABCG2) is a 72 kDa half-transporter that acts as a homomeric dimer, and so far, BCRP is known to mediate resistance to a variety of anti-cancer agents, among these the chemotherapeutic agents SN-38, topotecan, mitoxantrone, doxorubicin, and daunorubicin [11,12,13,14,15,16].