Sesink et al. showed that breast cancer resistance ABCG2 and the multidrug resistance-associated protein 2 (Mrp2), two ATP-binding cassette (ABC) transporters involved in drug cancer resistance are able to pump both quercetin aglycone and quercetin conjugated derivatives out of the cells and thus explain the low bioavailability of quercetin (234). The gene discussed is ABCC2; the disease is breast carcinoma.