The overexpression of the membrane drug transporter ATP-binding cassette subfamily B member 1 (ABCB1), also known as P-glycoprotein (P-gp) or multidrug resistance protein 1 (MDR1), has been extensively investigated in relation to chemotherapy resistance in osteosarcoma, as reported in various studies [59,60,61]. Here, ABCB1 is linked to osteosarcoma.