ABCB1 and osteosarcoma: HIF-1α has been reported to have a direct linkage with the ABCB1-mediated chemoresistance in osteosarcoma: indeed, HIF-1α is induced during the acquisition of doxorubicin resistance by the continuous exposure to the drug and in turn, it mediates the resistance to doxorubicin by up-regulating ABCB1 [50].