CXCL12 and plasma cell myeloma: Chemokine (C-X-C motif) ligand 12(CXCL12), chemokines ligand 2(CCL2), chemokines ligand 3(CCL3) and chemokines ligand 14(CCL14) produced by myeloma cells and BMSCs promote macrophage M2 polarization and imbalance the M1/M2 ratio (19, 20).