Others have also investigated the effects of single-step doxorubicin selection on the human sarcoma cell line MES-SA and have reported an increase in ABCB1 expression (Chen et al, 1994; Beketic-Oreskovic et al, 1995); yet previous studies were performed before the identification of ABCG2 as a major ABC transporter in the area of MDR. The gene discussed is ABCB1; the disease is sarcoma.