In both MCF-7/AdrVp3000 (over-expressing ABCG2) and full length ABCG2 cDNA-transfected MCF-7 breast cancer cells, the over-expression of this transporter conferred resistance to several xenobiotics including mitoxantrone, doxorubicin and daunorubicin, also reducing the intracellular accumulation of Rhodamine-123 (R123) by an ATP-dependent mechanism5,7. The gene discussed is ABCG2; the disease is breast cancer.