The inhibition of the interaction between myeloma cells and macrophages via PSGL-1/selectins and intercellular adhesion molecule-1 (ICAM-1)/LFA-1 compromised macrophage-mediated protection in vitro, suggesting that cell–cell contact between surface proteins in MM cells and macrophages is important for macrophage-mediated protection of myeloma cells from chemotherapy-induced apoptosis [22,135,150]. This evidence concerns the gene SELPLG and plasma cell myeloma.