However, inside the myeloma cell niche, two soluble mediators, i.e., a proliferation-induced ligand (APRIL) and B-cell activation factor (BAFF) interact with B-cell maturation antigen (BCMA) on the surface of MM cells, play an important role in survival and proliferation of tumor plasma cells. The gene discussed is TNFRSF17; the disease is plasma cell myeloma.