title: Soluble rank ligand produced by myeloma cells causes generalised bone loss in multiple myeloma.
abstract: Patients with multiple myeloma commonly develop focal osteolytic bone disease, as well as generalised osteoporosis. The mechanisms underlying the development of osteoporosis in patients with myeloma are poorly understood. Although disruption of the RANKL/OPG pathway has been shown to underlie formation of focal osteolytic lesions, its role in the development of osteoporosis in myeloma remains unclear. Increased soluble RANKL in serum from patients with myeloma raises the possibility that this molecule plays a key role. The aim of the present study was to establish whether sRANKL produced by myeloma cells contributes directly to osteoporosis. C57BL/KaLwRij mice were injected with either 5T2MM or 5T33MM murine myeloma cells. 5T2MM-bearing mice developed osteolytic bone lesions (p<0.05) with increased osteoclast surface (p<0.01) and reduced trabecular bone volume (p<0.05). Bone volume was also reduced at sites where 5T2MM cells were not present (p<0.05). In 5T2MM-bearing mice soluble mRANKL was increased (p<0.05), whereas OPG was not altered. In contrast, 5T33MM-bearing mice had no changes in osteoclast surface or trabecular bone volume and did not develop osteolytic lesions. Soluble mRANKL was undetectable in serum from 5T33MM-bearing mice. In separate experiments, RPMI-8226 human myeloma cells were transduced with an human RANKL/eGFP construct, or eGFP alone. RPMI-8226/hRANKL/eGFP cells, but not RPMI-8226/eGFP cells, stimulated osteoclastic bone resorption (p<0.05) in vitro. Sub-cutaneous injection of NOD/SCID mice with RPMI-8226/hRANKL/eGFP or RPMI-8226/eGFP cells resulted in tumour development in all mice. RPMI-8226/hRANKL/eGFP-bearing mice exhibited increased serum soluble hRANKL (p<0.05) and a three-fold increase in osteoclast number (p<0.05) compared to RPMI-8226/eGFP-bearing mice. This was associated with reduced trabecular bone volume (27%, p<0.05), decreased trabecular number (29%, p<0.05) and increased trabecular thickness (8%, p<0.05). Our findings demonstrate that soluble RANKL produced by myeloma cells causes generalised bone loss, suggesting that targeting RANKL may prevent osteoporosis in patients with myeloma.
authors.affiliation: Department of Human Metabolism, University of Sheffield Faculty of Medicine, Dentistry and Health, Sheffield, United Kingdom.
authors.forename: Clive Henry
authors.initials: CH
authors.lastname: Buckle
authors.forename: Evy
authors.initials: E
authors.lastname: De Leenheer
authors.forename: Michelle Anne
authors.initials: MA
authors.lastname: Lawson
authors.forename: Kwee
authors.initials: K
authors.lastname: Yong
authors.forename: Neil
authors.initials: N
authors.lastname: Rabin
authors.forename: Mark
authors.initials: M
authors.lastname: Perry
authors.forename: Karen
authors.initials: K
authors.lastname: Vanderkerken
authors.forename: Peter Ian
authors.initials: PI
authors.lastname: Croucher
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000378:metabolism*; D045744:Cell Line, Tumor; D018076:DNA, Complementary / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D008159:Lumbar Vertebrae / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D016513:Mice, SCID; D009101:Multiple Myeloma / Q000378:metabolism*; D009368:Neoplasm Transplantation; D010010:Osteoclasts / Q000166:cytology*; D010024:Osteoporosis / Q000235:genetics / Q000503:physiopathology; D053244:Osteoprotegerin / Q000378:metabolism; D053245:RANK Ligand / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D053244:Osteoprotegerin; D053245:RANK Ligand; D049452:Green Fluorescent Proteins