Most previous investigations have focused on reversing MDR by antagonizing the function or downregulating the expression of PGP1 in osteosarcoma, and several drugs to reverse MDR have been developed, including verapamil, cyclosporin A, biricodar and valspodar (Ferry et al., 1996; Mullin et al., 2004; Karthikeyan and Hoti, 2015). The gene discussed is CD44; the disease is osteosarcoma.