Multiple myeloma cells secreted RNAKL and interleukin-6 (IL-6), endocytosed osteoprotegerin (OPG) to result in the elevated ratio of RNAKL/OPG, which promoted the differentiation and maturation of osteoclast precursors [9–13]. The gene discussed is TNFRSF11B; the disease is AL amyloidosis.