TNF and plasma cell myeloma: In addition, IL1β and TNFα, which act as pathological osteoclastogenic factors [29, 30], were highly expressed in both osteoclast progenitor PBMCs and differentiated osteoclasts from multiple myeloma patients than in those from healthy controls, which was consistent with increased levels of circulating osteoclastogenic factors in the blood obtained from patients with multiple myeloma, as shown in Fig. 1c.