Myeloma cells can directly contribute to the pool of RANKL in bone bypassing the classic stromal and osteoblast pathway of osteoclast stimulation.
Summary The ratio of osteoprotegerin [OPG, tumour necrosis factor receptor superfamily, member 11b (TNFRSF11B)] to receptor activator of nuclear factor kappaB ligand [RANKL, tumour necrosis factor (ligand) superfamily, member 11 (TNFSF11)] in bone is critical for the regulation of bone remodelling. Myeloma cells can home to bone, triggering increased RANKL and decreased OPG expression by stromal cells, leading to osteolysis. Whether myeloma cells contribute directly to the pool of RANKL or OPG in bone has been contentious. Here we provide evidence of RANKL expression by reverse transcription polymerase chain reaction and in situ hybridization, demonstrating transcripts encoding both the membrane-bound and secreted forms of RANKL in five human multiple myeloma cell lines (LP-1, NCI-H929, OPM-2, RPMI8226, U266) and myeloma cells purified from bone marrow aspirates of myeloma patients. We demonstrated that RANKL encoding mRNAs are translated to protein by antibody detection of RANKL. In vitro assays showed that myeloma cells induced bone marrow derived mononuclear cells to differentiate into adherent tartrate-resistant acid phosphatase positive multinucleated cells, indicative of the formation of functional osteoclasts. This differentiation could also be achieved with passaged myeloma media alone, implicating secreted products. Finally, we provide evidence that the differentiation observed is at least in part the result of myeloma cell expression of RANKL. We therefore conclude that myeloma cells can directly contribute to the pool of RANKL in bone.
Lai
F P L
FP
Alfred Pathology Service, Alfred Hospital, Melbourne, Victoria, Australia.
Cole-Sinclair
M
M
Cheng
W-J
WJ
Quinn
J M W
JM
Gillespie
M T
MT
Sentry
J W
JW
Schneider
H-G
HG
D000135:Acid Phosphatase / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics*; D002454:Cell Differentiation; D002455:Cell Division; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned; D015870:Gene Expression; D006801:Humans; D017403:In Situ Hybridization / Q000379:methods; D007527:Isoenzymes / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000473:pathology*; D008562:Membrane Glycoproteins / Q000235:genetics*; D009101:Multiple Myeloma / Q000378:metabolism / Q000473:pathology*; D010010:Osteoclasts / Q000276:immunology / Q000473:pathology*; D020033:Protein Isoforms / Q000235:genetics; D011509:Proteoglycans; D053245:RANK Ligand; D012333:RNA, Messenger / Q000032:analysis*; D053246:Receptor Activator of Nuclear Factor-kappa B; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053667:Syndecans; D000071681:Tartrate-Resistant Acid Phosphatase; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D017077:Culture Media, Conditioned; D007527:Isoenzymes; D008562:Membrane Glycoproteins; D020033:Protein Isoforms; D011509:Proteoglycans; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; D053667:Syndecans; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase