For instance, resistance of metastatic tumors to the anthracycline doxorubicin (DOX) has been linked to overexpression of ABC transporters ABCB1 (MDR1/P-glycoprotein) [7], ABCC1 (MRP1) [8], ABCC2 (MRP2) [9, 10] and ABCG2 (MXR, BRCP) [11-13]. This evidence concerns the gene ABCG2 and metastatic neoplasm.