Osteoprotegerin inhibits prostate cancer–induced osteoclastogenesis and prevents prostate tumor growth in the bone
Jian Zhang, … , John Westman, Evan T. Keller
Jian Zhang, … , John Westman, Evan T. Keller
Published May 15, 2001
Citation Information: J Clin Invest. 2001;107(10):1235-1244. https://doi.org/10.1172/JCI11685.
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Article

Osteoprotegerin inhibits prostate cancer–induced osteoclastogenesis and prevents prostate tumor growth in the bone

Abstract

Prostate cancer (CaP) forms osteoblastic skeletal metastases with an underlying osteoclastic component. However, the importance of osteoclastogenesis in the development of CaP skeletal lesions is unknown. In the present study, we demonstrate that CaP cells directly induce osteoclastogenesis from osteoclast precursors in the absence of underlying stroma in vitro. CaP cells produced a soluble form of receptor activator of NF-κB ligand (RANKL), which accounted for the CaP-mediated osteoclastogenesis. To evaluate for the importance of osteoclastogenesis on CaP tumor development in vivo, CaP cells were injected both intratibially and subcutaneously in the same mice, followed by administration of the decoy receptor for RANKL, osteoprotegerin (OPG). OPG completely prevented the establishment of mixed osteolytic/osteoblastic tibial tumors, as were observed in vehicle-treated animals, but it had no effect on subcutaneous tumor growth. Consistent with the role of osteoclasts in tumor development, osteoclast numbers were elevated at the bone/tumor interface in the vehicle-treated mice compared with the normal values in the OPG-treated mice. Furthermore, OPG had no effect on CaP cell viability, proliferation, or basal apoptotic rate in vitro. These results emphasize the important role that osteoclast activity plays in the establishment of CaP skeletal metastases, including those with an osteoblastic component.

Authors

Jian Zhang, Jinlu Dai, Yinghua Qi, Din-Lii Lin, Peter Smith, Chris Strayhorn, Atsushi Mizokami, Zheng Fu, John Westman, Evan T. Keller

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Figure 1

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OPG inhibits LNCaP and C4-2B cell–induced osteoclastogenesis of osteobla...
OPG inhibits LNCaP and C4-2B cell–induced osteoclastogenesis of osteoblast/stromal cells in vitro. (a) LNCaP or C4-2B cells were directly cocultured with murine bone marrow cells for 9 days in the presence or absence of M-CSF (1 ng/ml). Osteoclast-like cells were identified as TRAP-positive multinucleated (>3 nuclei) cells. AP < 0.001 compared with its respective control culture (without adding CaP cells) or coculture; BP < 0.01 compared with its respective control culture; CP < 0.01 compared with its LNCaP cells. (b) Conditioned media (CM) from LNCaP and C4-2B cells was collected after 24 hours of culture, then the indicated concentrations of CM (vol/vol) was added to murine bone marrow cells and cultured for 9 days. Osteoclast-like cells were identified as TRAP-positive multinucleated (>3 nuclei) cells. AP < 0.001 compared with respective control culture (without adding CM); BP < 0.001 compared with each cell line’s respective control culture or coculture; CP < 0.01 compared with its LNCaP cells. (c) CM (25% vol/vol) from LNCaP and C4-2B cells were collected after 24 hours of culture, then added to murine bone marrow cells with different dose of recombinant mouse OPG (1–1000 ng/ml) as indicated and cultured for 9 days. Osteoclast-like cells were identified as TRAP-positive multinucleated (>3 nuclei) cells. AP < 0.001 compared with its control culture; BP < 0.01 compared with its respective vehicle-treated CM cultures; CP < 0.001 compared with its respective vehicle-treated CM cultures. All in vitro cultures were evaluated in quadruplicate. Results were reported as the mean (± SD) number of osteoclast-like cells per coverslip. Data were analyzed using ANOVA and Fisher’s least-significant difference for post hoc analysis.