These plasma cells also produce cytokines, such as interleukin-6 (IL-6),2 which stimulate osteoclasts via an osteoclast-stimulating-factor (such as interleukin-1, tumor necrosis factor-alpha, lymphotoxin) and increase myeloma cell growth.3,4 Osteoblasts are concomitantly suppressed, promoting bone breakdown, and the immune response that would normally attack the myeloma cells is also inhibited.