In breast cancer patients, use of the cholesterol-lowering agent simvastatin did not affect blood estradiol (E2) and estrone concentrations, whereas simvastatin treatment reduced the blood concentration of estone sulfate (a substrate of MRP and BCRP, [16, 19]) in female breast cancer patients, especially in postmenopausal participants [20]. Here, ABCG2 is linked to breast carcinoma.