Indeed, in our pilot migration experiment using one of the following three conditions in the lower chamber including FBS only, BMSC conditioned medium, or BMSCs, lower chamber loaded with BMSCs resulted in the highest yield of myeloma cell migration across the membrane (Additional file 1: Figure S1), implicating the importance of the SDF-1/CXCR4 axis in plasma cell migration [36]. Here, CXCR4 is linked to plasma cell myeloma.