ABCG2 and plasma cell myeloma: It has been fond that the poly-specific drug transporters ABCB1 (P-glycoprotein, PGP), ABCC1 (multidrug resistance-associated protein 1, MRP1), ABCG2 (breast cancer resistance protein, BCRP) and the ribonucleoprotein LRP are over-expressed in various types of cancer [4]–[7], and a number of studies have investigated the possibility of using conventional drugs or siRNA to inhibit ABC and LRP proteins in order to overcome MDR in myelomas and solid tumours such as ovarian, renal and hepatocellular carcinomas (HCCs) [8]–[13].