Receptor Activator of NF-κB Ligand Inhibition Suppresses Bone Resorption and Hypercalcemia but Does Not Affect Host Immune Responses to Influenza Infection

Abstract

Receptor activator of NF-κB (RANK) and its ligand (RANKL) are essential for osteoclast formation, function, and survival. Osteoprotegerin (OPG) inhibits RANK signaling by sequestering RANKL. This study evaluated the antiosteoclast and immunoregulatory effects of mouse rRANK-Fc, which, similar to OPG, can bind RANKL. The effect of RANKL inhibition by RANK-Fc on osteoclast function was determined by inhibition of vitamin D3 (1,25(OH)2D3)-induced hypercalcemia. Mice were injected with a single dose of 0, 10, 100, 500, or 1000 μg of RANK-Fc; 100 μg of OPG-Fc; or 5 μg of zoledronate 2 h before 1,25(OH)2D3 challenge on day 0, and sacrificed on days 1, 2, 4, 6, 8, 12, 16, and 20. RANK-Fc doses of 100 or 500 μg were tested in a mouse respiratory influenza virus host-resistance model. A single dose of RANK-Fc ≥100 μg suppressed elevation of serum calcium levels and suppressed the bone turnover marker serum pyridinoline at day 4 and later time points, similar to those observed with OPG-Fc and zoledronate (p ≤ 0.01 vs controls). By day 6, both immature and mature osteoclasts were depleted by high doses of RANK-Fc (500 and 1000 μg) or 100 μg of OPG-Fc. RANK-Fc doses of 100 or 500 μg had no detectable effect on immune responses to influenza infection, as measured by activation of cytotoxic T cell activity, influenza-specific IgG response, and virus clearance. RANK-Fc inhibition of RANKL has antiosteoclast activity at doses that have no detectable immunoregulatory activity, suggesting that RANKL inhibitors be further studied for their potential to treat excess bone loss.

The RANKL/RANK system as a therapeutic target for bone invasion by oral squamous cell carcinoma

“…Recent studies have shown that administration of OPG or sRANK prevents bone metastasis by cancer cells in vivo (21)(22)(23). These findings suggest that the RANKL/RANK system contributes to bone metastasis by cancer cells.…”

“…In support of this notion, recent studies in rodent models of breast and prostate cancer have established that inhibition of RANKL/RANK signal decreases bone lesion development and tumor growth in bone (21-23). Alternatively, it has been reported that functional RANK is expressed on some bone-associated tumor cells (21)(22)(23)54). Indeed, the migration of RANK-positive tumor cells is induced by RANKL stimulation.…”

“…Thus, RANKL levels are increased in osteolytic lesions associated with malignant tumors, whereas OPG levels are increased in osteoblastic lesions (20). This suggests that blocking RANKL/RANK with soluble RANK (sRANK) or OPG inhibits osteoclastogenesis and successfully prevents bone destruction by cancers (21)(22)(23). Therefore, in this review, we first summarize the RANKL/RANK signaling pathway and its effects on osteoclastogenesis.…”

Therapeutic efficacy of soluble receptor activator of nuclear factor-κB-Fc delivered by nonviral gene transfer in a mouse model of osteolytic osteosarcoma

“…Delivery of RANK-Fc as a recombinant protein has shown promising results as a potential therapy through experiments in animal models, in that RANK-Fc limits hypercalcemia and osteolysis induced by myeloma or prostate cancer and reduces bone tumor establishment in these models (15,16,29,36). Moreover, a recent study reported that RANK-Fc inhibition of RANKL has an antiosteoclast activity at doses that have no detectable immunoregulatory activity (37). Even if long-lasting expression of RANK-Fc could be provided at bone-protective levels using a retrovirus-mediated gene transfer approach by the use of genetically modified mesenchymal stem cells (17), the toxicity associated with the use of such viral vectors is extremely complex.…”

Combined therapy with the RANKL inhibitor RANK-Fc and rhApo2L/TRAIL/dulanermin reduces bone lesions and skeletal tumor burden in a model of breast cancer skeletal metastasis

“…The treatment regimen for RANK-Fc was based on the dose and schedule which optimally inhibits bone resorption in vivo. 32 Twenty-four hours after the first dose of rhApo2L/TRAIL (day 10), a 68% reduction in hind limb tumor burden (as measured by BLI) compared with PBS-treated animals was observed (p < 0.0001; Table 1). Upon cessation of treatment with rhApo2L/TRAIL, skeletal tumors continued to progress (Fig.…”