Bench to bedside: elucidation of the OPG-RANK-RANKL pathway and the development of denosumab

Long-term safety and effectiveness of denosumab in Japanese patients with osteoporosis: 3-year post-marketing surveillance study

INTRODUCTION

Denosumab is a humanized IgG2 monoclonal antibody that was approved for the treatment of osteoporosis in Japan in 2013. This study aimed to investigate the long-term safety and effectiveness of denosumab in Japanese patients with osteoporosis in daily clinical practice.

MATERIALS AND METHODS

This 3-year, prospective, observational, post-marketing study included patients who initiated treatment with denosumab (60 mg/6 months) for osteoporosis. Data were assessed at baseline, 3, 6, 12, 24 and 36 months. Key endpoints were adverse events (AEs), adverse drug reactions (ADRs), occurrence of osteoporotic fractures, bone mineral density (BMD), and bone turnover markers. Multivariate analyses were conducted to identify predictors of hypocalcaemia and percent change in BMD.

RESULTS

Overall, 3534 patients were assessed (mean 75.7 years; 89.8% women). In total, 298 patients (8.4%) developed ADRs; the most common was hypocalcaemia (3.9%). Hypocalcaemia risk was significantly increased in patients with creatinine clearance < 30 mL/min, no prior use of bisphosphonates, prior use of calcium and vitamin D preparations, baseline serum calcium < 8.5 mg/dL, and no concomitant use of calcium or vitamin D preparations. Six patients had adjudicated osteonecrosis of the jaw. Lumbar spine BMD increased significantly from baseline (mean percent change: 11.4% at 36 months). All bone turnover markers decreased significantly from baseline. Over 3 years, 3.3% of patients developed a new osteoporotic fracture.

CONCLUSIONS

This study confirmed the long-term safety and effectiveness of denosumab in Japanese patients with osteoporosis in daily clinical practice. No new safety signals were identified.

Immuno-PET Molecular Imaging of RANKL in Cancer

PURPOSE

The involvement of RANK/RANKL signaling in the tumor microenvironment (TME) in driving response or resistance to immunotherapy has only very recently been recognized. Current quantification methods of RANKL expression suffer from issues such as sensitivity, variability, and uncertainty on the spatial heterogeneity within the TME, resulting in conflicting reports on its reliability and limited use in clinical practice. Non-invasive molecular imaging using immuno-PET is a promising approach combining superior targeting specificity of monoclonal antibodies (mAb) and spatial, temporal and functional information of PET. Here, we evaluated radiolabeled anti-RANKL mAbs as a non-invasive biomarker of RANKL expression in the TME.

EXPERIMENTAL DESIGN

Anti-human RANKL mAbs (AMG161 and AMG162) were radiolabeled with ⁸⁹Zr using the bifunctional chelator DFO in high yield, purity and with intact binding affinity. After assessing the biodistribution in healthy CD-1 nude mice, [⁸⁹Zr]Zr-DFO-AMG162 was selected for further evaluation in ME-180 (RANKL-transduced), UM-SCC-22B (RANKL-positive) and HCT-116 (RANKL-negative) human cancer xenografts to assess the feasibility of in vivo immuno-PET imaging of RANKL.

RESULTS

[⁸⁹Zr]Zr-DFO-AMG162 was selected as the most promising tracer for further validation based on biodistribution experiments. We demonstrated specific accumulation of [⁸⁹Zr]Zr-DFO-AMG162 in RANKL transduced ME-180 xenografts. In UM-SCC-22B xenograft models expressing physiological RANKL levels, [⁸⁹Zr]Zr-DFO-AMG162 imaging detected significantly higher signal compared to control [⁸⁹Zr]Zr-DFO-IgG2 and to RANKL negative HCT-116 xenografts. There was good visual agreement with tumor autoradiography and immunohistochemistry on adjacent slides, confirming these findings.

CONCLUSIONS

[⁸⁹Zr]Zr-DFO-AMG162 can detect heterogeneous RANKL expression in the TME of human cancer xenografts, supporting further translation of RANKL immuno-PET to evaluate tumor RANKL distribution in patients.

Various Therapeutic Methods for the Treatment of Medication-Related Osteonecrosis of the Jaw (MRONJ) and Their Limitations: A Narrative Review on New Molecular and Cellular Therapeutic Approaches

Medication-related osteonecrosis of the jaw (MRONJ) is one of the most interesting diseases in the field of maxillofacial surgery. In addition to bisphosphonates, the use of antiresorptive and antiangiogenic agents is known to be the leading cause. However, the exact pathogenesis of MRONJ has not been established, and various hypotheses have been proposed, such as oxidative stress-related theory. As a result, a definitive treatment protocol for MRONJ has not been identified, while various therapeutic approaches are applied to manage patients with MRONJ. Although the surgical approach to treat osteomyelitis of the jaw has been proven to be most effective, there are limitations, such as recurrence and delayed healing. Many studies and clinical trials are being conducted to develop another effective therapeutic modality. The use of some materials, including platelet concentrates and bone morphogenetic proteins, showed a positive effect on MRONJ. Among them, teriparatide is currently the most promising material, and it has shown encouraging results when applied to patients with MRONJ. Furthermore, cell therapy using mesenchymal stem cells showed promising results, and it can be the new therapeutic approach for the treatment of MRONJ. This review presents various treatment methods for MRONJ and their limitations while investigating newly developed and researched molecular and cellular therapeutic approaches along with a literature review.

Doxycycline-doped membranes induced osteogenic gene expression on osteoblastic cells

OBJECTIVES

To analyze how novel developed silicon dioxide composite membranes, functionalized with zinc or doxycycline, can modulate the expression of genes related to the osteogenic functional capacity of osteoblastic cells.

METHODS

The composite nanofibers membranes were manufactured by using a novel polymeric blend and 20 nm silicon dioxide nanoparticles (SiO₂-NPs). To manufacture the membranes, 20 nm SiO₂-NPs were added to the polymer solution and the resulting suspension was processed by electrospinning. In a second step, the membranes were functionalized with zinc or doxycycline. Then, they were subjected to MG63 osteoblast-like cells culturing for 48 h. After this time, real-time quantitative polymerase chain reaction (RT-qPCR) was carried out to study the expression of Runx-2, OSX, ALP, OSC, OPG, RANKL, Col-I, BMP-2, BMP-7, TGF-β1, VEGF, TGF-βR1, TGF- βR2, and TGF-βR3. Mean comparisons were conducted by One-way ANOVA and Tukey tests (p < 0.05).

RESULTS

In general, the blending of SiO₂-NPs in the tested non-resorbable polymeric scaffold improves the expression of osteogenic genes over the control membranes. Doxycycline doping of experimental scaffolds attained the best results, encountering up-regulation of BMP-2, ALP, OPG, TGFβ-1 and TGFβ-R1. Membranes with zinc induced a significant increase in the expression of Col-I, ALP and TGF β1. Both, zinc and doxycycline functionalized membranes enormously down-regulated the expression of RANKL.

CONCLUSIONS

Zinc and doxycycline doped membranes are bioactive inducing overexpression of several osteogenic gene markers.

CLINICAL SIGNIFICANCE

Doxycycline doped membranes may be a potential candidate for use in GBR procedures in several challenging pathologies, including periodontal diseases.

Pharmacological Treatment of Osteoporosis in Elderly People: A Systematic Review and Meta-Analysis

BACKGROUND

The evidence supporting the use of antiresorptive and anabolic agents for fracture prevention in elderly patients is still inconclusive. Whether it is too late to alter the course of the disease in this age-group has remained uncertain.

OBJECTIVES

The objective of this study was to determine the efficacy and safety of antiresorptive and anabolic agents in elderly patients.

METHODS

PubMed, Web of Science, MEDLINE, and the Cochrane Central Register of Controlled Trials were searched for randomized controlled trials (RCTs) and post hoc analyses of RCTs reporting efficacy outcomes or adverse events of antiresorptive and anabolic agents in elderly patients. Statistical heterogeneity was assessed with the Cochran Q χ2 test and I2 statistic. All results were expressed as relative risk (RR) with 95% confidence intervals (CIs).

RESULTS

The meta-analysis included 1 RCT and 11 post hoc analyses of data from 10 double-blind placebo-controlled RCTs. Antiresorptive therapy significantly reduced the pooled incidence of vertebral fractures (RR = 0.43; 95% CI = 0.35-0.53; and p < 0.001). It was also associated with lower risk of nonvertebral and hip fractures (RR = 0.84; 95% CI = 0.74-0.96; and p = 0.009 and RR = 0.75; 95% CI = 0.58-0.97; and p = 0.028, respectively). For any adverse events, no difference was observed between antiresorptive agents and placebo groups (RR = 1.01; 95% CI = 1.00-1.02; and p = 0.23).

CONCLUSIONS

Both antiresorptive and anabolic agents represented potentially important osteoporosis treatments, showing significant effects on reducing vertebral, nonvertebral, or hip fracture risk, and were well-tolerated by elderly patients. Even in the elderly, maybe it is not too late to alter the course of the disease.

Muscle-Bone Crosstalk in Chronic Kidney Disease: The Potential Modulatory Effects of Exercise

Chronic kidney disease (CKD) is a prevalent worldwide public burden that increasingly compromises overall health as the disease progresses. Two of the most negatively affected tissues are bone and skeletal muscle, with CKD negatively impacting their structure, function and activity, impairing the quality of life of these patients and contributing to morbidity and mortality. Whereas skeletal health in this population has conventionally been associated with bone and mineral disorders, sarcopenia has been observed to impact skeletal muscle health in CKD. Indeed, bone and muscle tissues are linked anatomically and physiologically, and together regulate functional and metabolic mechanisms. With the initial crosstalk between the skeleton and muscle proposed to explain bone formation through muscle contraction, it is now understood that this communication occurs through the interaction of myokines and osteokines, with the skeletal muscle secretome playing a pivotal role in the regulation of bone activity. Regular exercise has been reported to be beneficial to overall health. Also, the positive regulatory effect that exercise has been proposed to have on bone and muscle anatomical, functional, and metabolic activity has led to the proposal of regular physical exercise as a therapeutic strategy for muscle and bone-related disorders. The detection of bone- and muscle-derived cytokine secretion following physical exercise has strengthened the idea of a cross communication between these organs. Hence, this review presents an overview of the impact of CKD in bone and skeletal muscle, and narrates how these tissues intrinsically communicate with each other, with focus on the potential effect of exercise in the modulation of this intercommunication.

RANK signaling increases after anti-HER2 therapy contributing to the emergence of resistance in HER2-positive breast cancer

BACKGROUND

Around 15-20% of primary breast cancers are characterized by HER2 protein overexpression and/or HER2 gene amplification. Despite the successful development of anti-HER2 drugs, intrinsic and acquired resistance represents a major hurdle. This study was performed to analyze the RANK pathway contribution in HER2-positive breast cancer and anti-HER2 therapy resistance.

METHODS

RANK and RANKL protein expression was assessed in samples from HER2-positive breast cancer patients resistant to anti-HER2 therapy and treatment-naive patients. RANK and RANKL gene expression was analyzed in paired samples from patients treated with neoadjuvant dual HER2-blockade (lapatinib and trastuzumab) from the SOLTI-1114 PAMELA trial. Additionally, HER2-positive breast cancer cell lines were used to modulate RANK expression and analyze in vitro the contribution of RANK signaling to anti-HER2 resistance and downstream signaling.

RESULTS

RANK and RANKL proteins are more frequently detected in HER2-positive tumors that have acquired resistance to anti-HER2 therapies than in treatment-naive ones. RANK (but not RANKL) gene expression increased after dual anti-HER2 neoadjuvant therapy in the cohort from the SOLTI-1114 PAMELA trial. Results in HER2-positive breast cancer cell lines recapitulate the clinical observations, with increased RANK expression observed after short-term treatment with the HER2 inhibitor lapatinib or dual anti-HER2 therapy and in lapatinib-resistant cells. After RANKL stimulation, lapatinib-resistant cells show increased NF-κB activation compared to their sensitive counterparts, confirming the enhanced functionality of the RANK pathway in anti-HER2-resistant breast cancer. Overactivation of the RANK signaling pathway enhances ERK and NF-κB signaling and increases lapatinib resistance in different HER2-positive breast cancer cell lines, whereas RANK loss sensitizes lapatinib-resistant cells to the drug. Our results indicate that ErbB signaling is required for RANK/RANKL-driven activation of ERK in several HER2-positive cell lines. In contrast, lapatinib is not able to counteract the NF-κB activation elicited after RANKL treatment in RANK-overexpressing cells. Finally, we show that RANK binds to HER2 in breast cancer cells and that enhanced RANK pathway activation alters HER2 phosphorylation status.

CONCLUSIONS

Our data support a physical and functional link between RANK and HER2 signaling in breast cancer and demonstrate that increased RANK signaling may contribute to the development of lapatinib resistance through NF-κB activation. Whether HER2-positive breast cancer patients with tumoral RANK expression might benefit from dual HER2 and RANK inhibition therapy remains to be elucidated.

Successful denosumab treatment for central giant cell granuloma in a 9-year-old child

BACKGROUND

Denosumab is a nonsurgical treatment option for central giant cell granulomas (CGCG), especially in aggressive lesions.

CASE REPORT

We describe a 9-year-old girl with an aggressive maxillary CGCG successfully treated with denosumab, avoiding a mutilating surgery after intralesional corticosteroid injections failed, and the lesion continued to rapidly grow. During denosumab treatment, she developed a self-limiting area of osteonecrosis in the maxillary alveolar bone, which rapidly resolved after antibiotic therapy. Six months after denosumab discontinuation, a maxillary surgical recontour was performed. Two weeks after surgery, the patient presented vomiting, pallor, dehydration, but no fever. Blood tests revealed severe hypercalcemia and acute renal dysfunction. After discarding thyroid, parathyroid, and adrenal alterations, a diagnosis of severe rebound hypercalcemia after denosumab treatment was made. Treatment consisted of hyperhydration, calcium pamidronate, and methylprednisolone, restoring calcium levels to normal.

CONCLUSION

After 2 years of follow-up, she remains on orthodontic treatment, with no recurrences or other episodes of hypercalcemia.

Giant Cell Tumor of Bone: An Update

PURPOSE OF REVIEW

To highlight the new developments in the management of advanced giant cell tumor of bone, a rare locally aggressive benign tumor, which was traditionally managed with surgery alone by either curettage and local adjuvant therapy, wide resection, or marginal excision. Here, we review the current role of systemic therapy for management of locally advanced or metastatic giant cell tumor of bone (GCTB).

RECENT FINDINGS

The elucidation of the pathophysiology of giant cell tumor of bone, especially with regards to the role of nuclear factor kappa B ligand (RANKL), has led to the Food and Drug Administration (FDA) approval of denosumab in the management of locally advanced or metastatic GCTB. For advanced giant cell tumor where surgical resection alone can cause severe morbidity, the paradigm has shifted from local treatment alone to multidisciplinary management with the consideration of use of denosumab.

Association of environmental cadmium exposure and bone remodeling in women over 50 years of age

Chronic cadmium (Cd) toxicity is a significant health concern, and the mechanism of long-term low-dose Cd exposure on bone has not been fully elucidated yet. This study aimed to assess the association between long-term environmental Cd exposure and bone remodeling in women who aged over 50. A total of 278 non-smoking subjects from Cd-polluted group (n = 191) and non-Cd polluted group (n = 87) were investigated. Bone mineral density (BMD), the levels of three bone turnover markers (BTMs), including total procollagen type 1 amino-terminal propeptide (P1NP), collagen type 1 cross-linked C-telopeptide (β-CTX), bone-specific alkaline phosphatase (BALP), together with serum soluble receptor activator of nuclear factor-κB ligand (sRANKL) and osteoprotegerin (OPG) were determined. Early markers of renal dysfunction were measured as well. Urinary Cd concentrations ranged from 0.41 to 87.31 μg/g creatinine, with a median of 4.91 μg/g creatinine. Age, BMD, T-score, and prevalence of osteoporosis showed no statistical differences among the quartiles of urinary Cd concentrations, while serum levels of P1NP, β-CTX, and OPG were higher in the upper quartiles. Multivariate linear regression models indicated significantly positive associations of urinary Cd concentration with serum levels of P1NP, β-CTX, BALP, sRANKL, and OPG. A ridge regression analysis with T-score and the three BTMs, sRANKL, and OPG, adjusted for age and body mass index (BMI), indicated that except for age and Cd exposure, β-CTX was a predictor of T-score. These findings demonstrated that Cd may directly accelerate bone remodeling. Serum β-CTX might be an appropriate biochemical marker for evaluating and monitoring Cd-related bone loss. Capsule: Cadmium (Cd) may directly accelerate bone remodeling and serum β-CTX is a valuable biochemical marker for evaluating Cd-related bone loss.

A novel modified RANKL variant can prevent osteoporosis by acting as a vaccine and an inhibitor

BACKGROUND

The discovery of receptor activator of nuclear factor-ĸB ligand (RANKL) as the final effector in the pathogenesis of osteoporosis has led to a better understanding of bone remodeling. When RANKL binds to its receptor (RANK), osteoclastic differentiation and activation are initiated. Herein, we propose a strategy using a novel RANKL variant as a competitive inhibitor for RANKL. The RANKL variant activates LGR4 signaling, which competitively regulates RANK and acts as an immunogen that induces anti-RANKL antibody production.

METHODS

We modified the RANK-binding site on RANKL using minimal amino acid changes in the RANKL complex and its counterpart receptor RANK and tried to evaluate the inhibitory effects on osteoclastogenesis.

RESULTS

The novel RANKL variant did not bind RANK in osteoclast progenitor cells, but activated LGR4 through the GSK3-β signaling pathway, thereby suppressing activated T cell cytoplasmic nuclear factor calcineurin-dependent 1 (NFATc1) expression and activity during osteoclastogenesis. Our RANKL variant generated high levels of RANKL-specific antibodies, blocked osteoclastogenesis, and inhibited osteoporosis in ovariectomized mouse models. Generated anti-RANKL antibodies showed a high inhibitory effect on osteoclastogenesis in vivo and in vitro.

CONCLUSIONS

We observed that the novel RANKL indeed blocks RANKL via LGR4 signaling and generates anti-RANKL antibodies, demonstrating an innovative strategy in the development of general immunotherapy.

Osthole enhances the bone mass of senile osteoporosis and stimulates the expression of osteoprotegerin by activating β-catenin signaling

Introduction

Osthole has a potential therapeutic application for anti-osteoporosis. The present study verified whether osthole downregulates osteoclastogenesis via targeting OPG.

Methods

In vivo, 12-month-old male mice were utilized to evaluate the effect of osthole on bone mass. In vitro, bone marrow stem cells (BMSCs) were isolated and extracted from 3-month-old OPG^−/− mice and the littermates of OPG^+/+ mice. Calvaria osteoblasts were extracted from 3-day-old C57BL/6J mice or 3-day-old OPG^−/− mice and the littermates of OPG^+/+ mice.

Results

Osthole significantly increased the gene and protein levels of OPG in primary BMSCs in a dose-dependent manner. The deletion of the OPG gene did not affect β-catenin expression. The deletion of the β-catenin gene inhibited OPG expression in BMSCs, indicating that osthole stimulates the expression of OPG via activation of β-catenin signaling.

Conclusion

Osthole attenuates osteoclast formation by stimulating the activation of β-catenin-OPG signaling and could be a potential drug for the senile osteoporosis.

Carbonic anhydrase 13 suppresses bone metastasis in breast cancer

Metastatic progression is the leading cause of mortality in breast cancer. However, molecular mechanisms that govern this process remain unclear. In this study, we found that carbonic anhydrase 13 (CA13) plays a potential role in suppressing bone metastasis. iRFP713-labeled iCSCL-10A (iRFP-iCSCL-10A) breast cancer cells, which exhibit the hallmarks of cancer stem cells, exerted the ability of bone metastasis in hind legs after 5-week injections, whereas no metastasis was observed in control iRFP713-labeled MCF-10A (iRFP-MCF10A) cells. Transcriptome analysis indicated that the expression of several genes, including metabolism-related CA13, was reduced in bone metastatic iRFP-iCSCL-10A cells. In vitro and in vivo analyses demonstrated that overexpression of CA13 in iRFP-iCSCL-10A cells suppressed migration, invasion, and bone metastasis, together with the reduction of VEGF-A and M-CSF expression. Furthermore, we found that breast cancer patients with a low CA13 expression had significantly shorter overall survival and disease-free survival rates compared to those with higher CA13 expression. These findings suggest that CA13 may act as a novel prognostic biomarker and would be a therapeutic candidate for the prevention of bone metastasis in breast cancer.

Severe osteoporosis: Principles for pharmacological therapy in Mexico

BACKGROUND

This article presents evidence and recommendations regarding the efficacy and safety of the approved and available therapies in Mexico to treat severe or established osteoporosis with the aim of developing a position regarding therapeutics in this stage of the disease, according to the descriptive cards of the National Drug Formulary of the National General Health Council of Mexico.

METHODS

We performed a systematic and narrative review of the evidence of teriparatide and denosumab, from their pharmacological profile, effectiveness, and safety derived from clinical trials, as well as an analysis of the general recommendations of the national and international clinical practice guidelines.

RESULTS

The evidence establishes that teriparatide and denosumab belong to different therapeutic classes, with biologically opposed mechanisms of action and indications of use, which are clearly differentiated in their respective national codes, therefore these drugs cannot be substitutable or interchangeable in severe osteoporosis therapy. Both represent the best options currently available for this stage of the disease; being similar in their efficacy in preventing new vertebral fragility fractures, with an RR of .35 (CI 95%; .22-.55) for teriparatide, and .32 (CI 95%: .26-.41) for denosumab. The absolute risk reduction is higher with teriparatide 9.3% (21 months) compared with denosumab at 4.8% (36 months).

CONCLUSIONS

Our results agree with the recommendations available in national and international clinical practice guidelines, with both therapies proposed as a sequential, but not a substitute, treatment.

Characteristics of pre-metastatic niche: the landscape of molecular and cellular pathways

Metastasis is a major contributor to cancer-associated deaths. It involves complex interactions between primary tumorigenic sites and future metastatic sites. Accumulation studies have revealed that tumour metastasis is not a disorderly spontaneous incident but the climax of a series of sequential and dynamic events including the development of a pre-metastatic niche (PMN) suitable for a subpopulation of tumour cells to colonize and develop into metastases. A deep understanding of the formation, characteristics and function of the PMN is required for developing new therapeutic strategies to treat tumour patients. It is rapidly becoming evident that therapies targeting PMN may be successful in averting tumour metastasis at an early stage. This review highlights the key components and main characteristics of the PMN and describes potential therapeutic strategies, providing a promising foundation for future studies.

Targeted Ptpn11 deletion in mice reveals the essential role of SHP2 in osteoblast differentiation and skeletal homeostasis

The maturation and function of osteoblasts (OBs) rely heavily on the reversible phosphorylation of signaling proteins. To date, most of the work in OBs has focused on phosphorylation by tyrosyl kinases, but little has been revealed about dephosphorylation by protein tyrosine phosphatases (PTPases). SHP2 (encoded by PTPN11) is a ubiquitously expressed PTPase. PTPN11 mutations are associated with both bone and cartilage manifestations in patients with Noonan syndrome (NS) and metachondromatosis (MC), although the underlying mechanisms remain elusive. Here, we report that SHP2 deletion in bone gamma-carboxyglutamate protein-expressing (Bglap+) bone cells leads to massive osteopenia in both trabecular and cortical bones due to the failure of bone cell maturation and enhanced osteoclast activity, and its deletion in Bglap+ chondrocytes results in the onset of enchondroma and osteochondroma in aged mice with increased tubular bone length. Mechanistically, SHP2 was found to be required for osteoblastic differentiation by promoting RUNX2/OSTERIX signaling and for the suppression of osteoclastogenesis by inhibiting STAT3-mediated RANKL production by osteoblasts and osteocytes. These findings are likely to explain the compromised skeletal system in NS and MC patients and to inform the development of novel therapeutics to combat skeletal disorders.

Corydalis Saxicola Bunting Total Alkaloids Attenuate Walker 256-Induced Bone Pain and Osteoclastogenesis by Suppressing RANKL-Induced NF-κB and c-Fos/NFATc1 Pathways in Rats

Metastatic bone pain is characterized by insufferable bone pain and abnormal bone structure. A major goal of bone cancer treatment is to ameliorate osteolytic lesion induced by tumor cells. Corydalis saxicola Bunting total alkaloids (CSBTA), the alkaloid compounds extracted from the root of C. saxicola Bunting, have been shown to possess anticancer and analgesic properties. In this study, we aimed to verify whether CSBTA could relieve cancer induced bone pain and inhibit osteoclastogenesis. The in vivo results showed that CSBTA ameliorated Walker 256 induced bone pain and osteoporosis in rats. Histopathological changes also supported that CSBTA inhibited Walker 256 cell-mediated osteolysis. Further in vitro analysis confirmed that CSBTA reduced the expression of RANKL and downregulate the level of RANKL/OPG ratio in breast cancer cells. Moreover, CSBTA could inhibit osteoclastogenesis by suppressing RANKL-induced NF-κB and c-Fos/NFATc1 pathways. Collectively, this study demonstrated that CSBTA could attenuate cancer induced bone pain via a novel mechanism. Therefore, CSBTA might be a promising candidate drug for metastatic bone pain patients.

Bone metastasis: mechanisms, therapies, and biomarkers

Skeletal metastases are frequent complications of many cancers, causing bone complications (fractures, bone pain, disability) that negatively affect the patient's quality of life. Here, we first discuss the burden of skeletal complications in cancer bone metastasis. We then describe the pathophysiology of bone metastasis. Bone metastasis is a multistage process: long before the development of clinically detectable metastases, circulating tumor cells settle and enter a dormant state in normal vascular and endosteal niches present in the bone marrow, which provide immediate attachment and shelter, and only become active years later as they proliferate and alter the functions of bone-resorbing (osteoclasts) and bone-forming (osteoblasts) cells, promoting skeletal destruction. The molecular mechanisms involved in mediating each of these steps are described, and we also explain how tumor cells interact with a myriad of interconnected cell populations in the bone marrow, including a rich vascular network, immune cells, adipocytes, and nerves. We discuss metabolic programs that tumor cells could engage with to specifically grow in bone. We also describe the progress and future directions of existing bone-targeted agents and report emerging therapies that have arisen from recent advances in our understanding of the pathophysiology of bone metastases. Finally, we discuss the value of bone turnover biomarkers in detection and monitoring of progression and therapeutic effects in patients with bone metastasis.

Bad to the bone: B cell acute lymphoblastic leukemia cells mediate bone destruction

Skeletal morbidities continue to cause acute and long-term burdens for B-ALL patients underscoring the need to identify the mechanisms underlying these processes and to develop effective therapies. Our recent findings demonstrated that B-ALL cells isolated at patient diagnosis can cause bone destruction and have identified the receptor activator of nuclear factor κ-B (RANK-RANKL) ligand axis as a critical effector of these effects.

The endocrine role of bone: Novel functions of bone-derived cytokines

Bone-derived cytokines refer to various proteins and peptides that are released from the skeleton and can distribute in organisms to regulate homeostasis by targeting many organs, such as the pancreas, brain, testicles, and kidneys. In addition to providing support and movement, many studies have disclosed the novel endocrine function of bone, and bone can modulate glucose and energy metabolism as well as phosphate metabolism by versatile bone-derived cytokines. However, this specific exoskeletonfunction of bone-derived cytokines in the regulation of homeostasis and the pathological response caused by skeletal dysfunction are still not very clear, and elucidation of the above mechanisms is of great significance for understanding the pathological processes of metabolic disorders and in the search for novel therapeutic measures for maintaining organ stability and physical fitness.

Molecular Mechanisms and Emerging Therapeutics for Osteoporosis

Osteoporosis is the most common chronic metabolic bone disease. It has been estimated that more than 10 million people in the United States and 200 million men and women worldwide have osteoporosis. Given that the aging population is rapidly increasing in many countries, osteoporosis could become a global challenge with an impact on the quality of life of the affected individuals. Osteoporosis can be defined as a condition characterized by low bone density and increased risk of fractures due to the deterioration of the bone architecture. Thus, the major goal of treatment is to reduce the risk for fractures. There are several treatment options, mostly medications that can control disease progression in risk groups, such as postmenopausal women and elderly men. Recent studies on the basic molecular mechanisms and clinical implications of osteoporosis have identified novel therapeutic targets. Emerging therapies targeting novel disease mechanisms could provide powerful approaches for osteoporosis management in the future. Here, we review the etiology of osteoporosis and the molecular mechanism of bone remodeling, present current pharmacological options, and discuss emerging therapies targeting novel mechanisms, investigational treatments, and new promising therapeutic approaches.

The Role of the RANKL/RANK Axis in the Prevention and Treatment of Breast Cancer with Immune Checkpoint Inhibitors and Anti-RANKL

The receptor activator of nuclear factor-κB (RANK) and the RANK ligand (RANKL) were reported in the regulation of osteoclast differentiation/activation and bone homeostasis. Additionally, the RANKL/RANK axis is a significant mediator of progesterone-driven mammary epithelial cell proliferation, potentially contributing to breast cancer initiation and progression. Moreover, several studies supported the synergistic effect of RANK and epidermal growth factor receptor (EGFR) and described RANK's involvement in epidermal growth factor receptor 2 (ERBB2)-positive carcinogenesis. Consequently, anti-RANKL treatment has been proposed as a new approach to preventing and treating breast cancer and metastases. Recently, RANKL/RANK signaling pathway inhibition has been shown to modulate the immune environment and enhance the efficacy of anti-CTLA-4 and anti-PD-1 monoclonal antibodies against solid tumors. Clinical and experimental trials have emerged evaluating RANKL inhibition as an enhancer of the immune response, rendering resistant tumors responsive to immune therapies. Trials evaluating the combinatorial effect of immune checkpoint inhibitors and anti-RANKL treatment in double-positive (RANK+/ERBB2+) patients are encouraging.

c-Met expression in renal cell carcinoma with bone metastases

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Bone is a common metastatic site in renal cell carcinoma (RCC).

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HGF/c-Met pathway is particularly relevant in tumors with bone metastases.

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c-Met/HGF pathway is involved in RCC progression, conferring poor prognosis.

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Several c-Met targeting therapies are currently in clinical development.

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c-Met expression is an important therapeutic target in RCC with bone metastases.

Hepatocyte growth factor (HGF)/c-Met pathway is implicated in embryogenesis and organ development and differentiation. Germline or somatic mutations, chromosomal rearrangements, gene amplification, and transcriptional upregulation in MET or alterations in autocrine or paracrine c-Met signalling have been associated with cancer cell proliferation and survival, including in renal cell carcinoma (RCC), and associated with disease progression. HGF/c-Met pathway has been shown to be particularly relevant in tumors with bone metastases (BMs). However, the efficacy of targeting c-Met in bone metastatic disease, including in RCC, has not been proven. Therefore, further investigation is required focusing the particular role of HGF/c-Met pathway in bone microenvironment (BME) and how to effectively target this pathway in the context of bone metastatic disease.

Denosumab in Giant Cell Tumor of Bone: Current Status and Pitfalls

Denosumab is a monoclonal antibody against RANK ligand for treatment of giant cell tumor of bone (GCTB). Clinical trials and case series have demonstrated that denosumab is relevant to beneficial tumor response and surgical down-staging in patients of GCTB. However, these trials or case series have limitations with a short follow-up. Recent increasing studies revealed that denosumab probably increased the local recurrence risk in patients treated with curettage. This may be caused by the thicken bone margin of tumor that trapped tumor cells from curettage. The direct bone formation by tumor cells in the margin after denosumab treatment also contributed to the local recurrence. in vitro studies showed denosumab resulted in a cytostatic instead of a true cytotoxic response on neoplastic stromal cells. More importantly, denosumab-treated GCTB exhibited morphologic overlap with malignancy, and a growing number of patients of malignant transformation of GCTB during denosumab treatment have been reported. The optimal duration, long term safety, maintenance dose, and optimum indications remain to be elucidated. With these concerns in mind, this review warns that the denosumab therapy of GCTB should be applied with caution.

Treatment with Zoledronate Subsequent to Denosumab in Osteoporosis: a Randomized Trial

Discontinuing denosumab is associated with bone loss and possibly increased fracture risk. We investigated if treatment with zoledronate (ZOL) could prevent bone loss and if the timing of the ZOL infusion influenced the outcome. We report on a 2-year randomized, open label, interventional study including 61 patients with osteopenia, discontinuing denosumab after 4.6 ± 1.6 years. We administrated ZOL 6 months (6M group, n = 20) or 9 months (9M group, n = 20) after the last denosumab injection or when bone turnover had increased (OBS group, n = 21). We monitored the patients with DXA and bone turnover markers. Our primary endpoints were change in lumbar spine BMD (LSBMD) 6 months after ZOL and the proportion of patients who failed to maintain BMD. The study is ongoing (clinicaltrials.gov; NCT03087851). We included 61 participants and 59 patients completed follow-up 12 months after ZOL. Six months after ZOL, LSBMD had decreased significantly by (mean ± SE) 2.1% ± 0.9%, 4.3% ± 1.1%, and 3.0% ± 1.1% in the 6M, 9M, and OBS groups, respectively, and by 4.8% ± 0.7%, 4.1% ± 1.1%, and 4.7% ± 1.2% 12 months after ZOL in the 6M, 9M, and OBS groups, respectively (p < .02, no between-group differences). BMD loss above the least significant change was seen in all groups; at the spine: 6M, n = 6 (30%); 9M, n = 9 (45%); and OBS, n = 9 (47%); and at the total hip: 6M, n = 1 (5%); 9M, n = 5 (25%); and OBS, n = 2 (11%). In the 6M group p-crosslinked C-terminal telopeptide (p-CTX) decreased initially, but increased rapidly thereafter, and 6 months after ZOL, p-CTX was 0.60 ± 0.08 g/L. p-CTX increased rapidly in the 9M and OBS groups, was suppressed by ZOL but increased again thereafter; p-CTX was 0.47 ± 0.05 μg/L and 0.47 ± 0.05 μg/L in the 9M and OBS groups 6 months after ZOL, respectively. Incident vertebral fractures were seen in two women in the 9M group. Treatment with ZOL irrespective of the timing did not fully prevent loss of BMD in patients discontinuing denosumab. © 2020 American Society for Bone and Mineral Research.

Updated bone mineral density status in Saudi patients with inflammatory bowel disease

BACKGROUND

Little is known about inflammatory bowel disease (IBD) burden and its impact on bone mineral density (BMD) among adult patients in Saudi Arabia. To the best of our knowledge, our study is the only study to give an update about this health problem in adult Saudi patients with IBD. IBD is a great risk factor for reduced BMD due to its associated chronic inflammation, malabsorption, weight loss and medication side effects. Consequently, screening for reduced BMD among patients with IBD is of utmost importance to curb and control anticipated morbidity and mortality among those patients.

AIM

To assess the relationship between IBD and BMD in a sample of adult Saudi patients with IBD.

METHODS

Ninety adult patients with IBD - 62 Crohn's disease (CD) and 28 ulcerative colitis (UC) - were recruited from King Fahad Specialist Hospital gastroenterology clinics in Buraidah, Al-Qassim. All enrolled patients were interviewed for their demographic information and for IBD- and BMD-related clinical data. All patients had the necessary laboratory markers and dual-energy x-ray absorptiometry scans to evaluate their BMD status. Patients were divided into two groups (CD and UC) to explore their clinical characteristics and possible risk factors for reduced BMD.

RESULTS

The CD group was significantly more prone to osteopenia and osteoporosis compared to the UC group; 44% of the CD patients had normal BMD, 19% had osteopenia, and 37% had osteoporosis, while 78% of the UC patients had normal BMD, 7% had osteopenia, and 25% had osteoporosis (P value < 0.05). In the CD group, the lowest t-score showed a statistically significant correlation with body mass index (BMI) (r = 0.45, P < 0.001), lumbar z-score (r = 0.77, P < 0.05) and femur z-score (r = 0.85, P < 0.05). In the UC group, the lowest t-score showed only statistically significant correlation with the lumbar z-score (r = 0.82, P < 0.05) and femur z-score (r = 0.80, P < 0.05). The ROC-curve showed that low BMI could predict the lowest t-score in the CD group with the best cut-off value at ≤ 23.43 (m/kg2); area under the curve was 0.73 (95%CI: 0.59-0.84), with a sensitivity of 77%, and a specificity of 63%.

CONCLUSION

Saudi patients with IBD still have an increased risk of reduced BMD, more in CD patients. Low BMI is a significant risk factor for reduced BMD in CD patients.

Osteoporosis in Patients with Chronic Kidney Diseases: A Systemic Review

Chronic kidney disease (CKD) is associated with the development of mineral bone disorder (MBD), osteoporosis, and fragility fractures. Among CKD patients, adynamic bone disease or low bone turnover is the most common type of renal osteodystrophy. The consequences of CKD-MBD include increased fracture risk, greater morbidity, and mortality. Thus, the goal is to prevent the occurrences of fractures by means of alleviating CKD-induced MBD and treating subsequent osteoporosis. Changes in mineral and humoral metabolism as well as bone structure develop early in the course of CKD. CKD-MBD includes abnormalities of calcium, phosphorus, PTH, and/or vitamin D; abnormalities in bone turnover, mineralization, volume, linear growth, or strength; and/or vascular or other soft tissue calcification. In patients with CKD-MBD, using either DXA or FRAX to screen fracture risk should be considered. Biomarkers such as bALP and iPTH may assist to assess bone turnover. Before initiating an antiresorptive or anabolic agent to treat osteoporosis in CKD patients, lifestyle modifications, such as exercise, calcium, and vitamin D supplementation, smoking cessation, and avoidance of excessive alcohol intake are important. Managing hyperphosphatemia and SHPT are also crucial. Understanding the complex pathogenesis of CKD-MBD is crucial in improving one's short- and long-term outcomes. Treatment strategies for CKD-associated osteoporosis should be patient-centered to determine the type of renal osteodystrophy. This review focuses on the mechanism, evaluation and management of patients with CKD-MBD. However, further studies are needed to explore more details regarding the underlying pathophysiology and to assess the safety and efficacy of agents for treating CKD-MBD.

Denosumab for cancer-related bone loss

INTRODUCTION

Prolonged use of anti-cancer treatments in breast and prostate tumors alters physiological bone turnover leading to adverse skeletal related events, such as osteoporosis, loss of bone mass, and increased risk of fractures. These complications known as cancer treatment-induced bone loss (CTIBL) should be managed with bone targeting agents such as the bisphosphonates and denosumab. The latter is a monoclonal antibody against the receptor activator of nuclear factor-kB ligand (RANKL) that suppresses osteoclasts function and survival increasing bone mass.

AREAS COVERED

This review will focus on the mechanisms associated with bone loss induced by cancer treatments and the most recent evidence about the use of denosumab as preventive and therapeutic strategy to protect bone health. Moreover, we will discuss several key aspects regarding the clinical practical use of denosumab to optimize the management of CTLIB in breast and prostate cancer.

EXPERT OPINION

Denosumab treatment strongly prevents cancer therapies-related skeletal issues in breast and prostate cancer with a good safety profile. Adjuvant six-monthly denosumab delays the time to first fracture onset in early stage breast cancer patients with normal or altered bone mineral density (BMD). Similarly, denosumab treatment is able to prevent fractures and BMD loss in nonmetastatic prostate cancer patients.

A Review of the Pharmacological Properties of Psoralen

Psoralen is the principal bioactive component in the dried fruits of Cullen corylifolium (L.) Medik (syn. Psoralea corylifolia L), termed "Buguzhi" in traditional Chinese medicine (TCM). Recent studies have demonstrated that psoralen displays multiple bioactive properties, beneficial for the treatment of osteoporosis, tumors, viruses, bacteria, and inflammation. The present review focuses on the research evidence relating to the properties of psoralen gathered over recent years. Firstly, multiple studies have demonstrated that psoralen exerts strong anti-osteoporotic effects via regulation of osteoblast/osteoclast/chondrocyte differentiation or activation due to the participation in multiple molecular mechanisms of the wnt/β-catenin, bone morphogenetic protein (BMP), inositol-requiring enzyme 1 (IRE1)/apoptosis signaling kinase 1 (ASK1)/c-jun N-terminal kinase (JNK) and the Protein Kinase B(AKT)/activator protein-1 (AP-1) axis, and the expression of miR-488, peroxisome proliferators-activated receptor-gamma (PPARγ), and matrix metalloproteinases (MMPs). In addition, the antitumor properties of psoralen are associated with the induction of ER stress-related cell death via enhancement of PERK: Pancreatic Endoplasmic Reticulum Kinase (PERK)/activating transcription factor (ATF), 78kD glucose-regulated protein (GRP78)/C/EBP homologous protein (CHOP), and 94kD glucose-regulated protein (GRP94)/CHOP signaling, and inhibition of P-glycoprotein (P-gp) or ATPase that overcomes multidrug resistance. Furthermore, multiple articles have shown that the antibacterial, anti-inflammatory and neuroprotective effects of psoralen are a result of its interaction with viral polymerase (Pol), destroying the formation of biofilm, and regulating the activation of tumor necrosis factor alpha (TNF-α), transforming growth factor beta (TGF-β), interleukin 4/5/6/8/12/13 (IL-4/5/6/8/12/13), GATA-3, acetylcholinesterase (AChE), and the hypothalamic-pituitary-adrenal (HPA) axis. Finally, the toxic effects and mechanisms of action of psoralen have also been reviewed.

Secreted Osteoclastogenic Factor of Activated T Cells (SOFAT) Is Associated With Rheumatoid Arthritis and Joint Pain: Initial Evidences of a New Pathway

Rheumatoid arthritis (RA) has an inflammatory milieu in the synovial compartment, which is regulated by a complex cytokine and chemokine network that induces continuously degenerative and inflammatory reactions. The secreted osteoclastogenic factor of activated T cells (SOFAT) is a unique cytokine and represents an alternative pathway for osteoclast activation. In this study, we examined whether SOFAT is able to induce joint pain and investigated the presence of SOFAT in a Collagen-induced Arthritis (CIA) model and in human subjects. Here, we found that an intra-articular stimulation with SOFAT (1, 10, 100, or 1,000 ng/10 μl) in the knee joint significantly decreases the mechanical threshold in the hind paw of mice (p < 0.05). Moreover, after a second injection of SOFAT, the mechanical threshold decrease was sustained for up to 8 days (p < 0.05). In the CIA model, the immunohistochemical assay of knee joint showed positivity stained for SOFAT, and the mRNA and protein expression of SOFAT were significantly higher in the affected-group (p < 0.05). Besides, the mRNA of RANKL, IL-1β, IL-6, and IL-15 were significantly higher in the affected-group (p < 0.05). Finally, SOFAT was detected in the synovial fluid of RA patients, but not in OA patients (p < 0.05). In conclusion, SOFAT is up regulated in inflammatory milieu such as RA but not in non-inflammatory OA. SOFAT may be a novel molecule in the complex inflammatory phenotype of RA.

Immune-Modulating Effects of Conventional Therapies in Colorectal Cancer

Biological heterogeneity and low inherent immunogenicity are two features that greatly impact therapeutic management and outcome in colorectal cancer. Despite high local control rates, systemic tumor dissemination remains the main cause of treatment failure and stresses the need for new developments in combined-modality approaches. While the role of adaptive immune responses in a small subgroup of colorectal tumors with inherent immunogenicity is indisputable, the challenge remains in identifying the optimal synergy between conventional treatment modalities and immune therapy for the majority of the less immunogenic cases. In this context, cytotoxic agents such as radiation and certain chemotherapeutics can be utilized to enhance the immunogenicity of an otherwise immunologically silent disease and enable responsiveness to immune therapy. In this review, we explore the immunological characteristics of colorectal cancer, the effects that standard-of-care treatments have on the immune system, and the opportunities arising from combining immune checkpoint-blocking therapy with immune-modulating conventional treatments.

Myokines and Osteokines in the Pathogenesis of Muscle and Bone Diseases

PURPOSE OF REVIEW

In this review we aim to summarize the latest findings on the network of molecules produced by muscle and bone under physiological and pathological conditions.

RECENT FINDINGS

The concomitant onset of osteoporosis and sarcopenia is currently one of the main threats that can increase the risk of falling fractures during aging, generating high health care costs due to hospitalization for bone fracture surgery. With the growing emergence of developing innovative therapies to treat these two age-related conditions that often have common onset, a broader understanding of molecular messengers regulating the communication between muscle and bone tissue became imperative. Recently it has been highlighted that two muscle-derived signals, such as the myokines Irisin and L-BAIBA, positively affect bone tissue. In parallel, there are signals derived from bone that affect either positively the skeletal muscle, such as osteocalcin, or negatively, such as RANKL.

Molecular mechanisms and clinical management of cancer bone metastasis

As one of the most common metastatic sites of malignancies, bone has a unique microenvironment that allows metastatic tumor cells to grow and flourish. The fenestrated capillaries in the bone, bone matrix, and bone cells, including osteoblasts and osteoclasts, together maintain the homeostasis of the bone microenvironment. In contrast, tumor-derived factors act on bone components, leading to subsequent bone resorption or excessive bone formation. The various pathways involved also provide multiple targets for therapeutic strategies against bone metastases. In this review, we summarize the current understanding of the mechanism of bone metastases. Based on the general process of bone metastases, we specifically highlight the complex crosstalk between tumor cells and the bone microenvironment and the current management of cancer bone metastases.

Crosstalk of Brain and Bone-Clinical Observations and Their Molecular Bases

As brain and bone disorders represent major health issues worldwide, substantial clinical investigations demonstrated a bidirectional crosstalk on several levels, mechanistically linking both apparently unrelated organs. While multiple stress, mood and neurodegenerative brain disorders are associated with osteoporosis, rare genetic skeletal diseases display impaired brain development and function. Along with brain and bone pathologies, particularly trauma events highlight the strong interaction of both organs. This review summarizes clinical and experimental observations reported for the crosstalk of brain and bone, followed by a detailed overview of their molecular bases. While brain-derived molecules affecting bone include central regulators, transmitters of the sympathetic, parasympathetic and sensory nervous system, bone-derived mediators altering brain function are released from bone cells and the bone marrow. Although the main pathways of the brain-bone crosstalk remain ‘efferent’, signaling from brain to bone, this review emphasizes the emergence of bone as a crucial ‘afferent’ regulator of cerebral development, function and pathophysiology. Therefore, unraveling the physiological and pathological bases of brain-bone interactions revealed promising pharmacologic targets and novel treatment strategies promoting concurrent brain and bone recovery.

Erythropoietin receptor in B cells plays a role in bone remodeling in mice

Erythropoietin (EPO) is a key regulator of erythropoiesis. However, EPO receptors (EPO-Rs) are also expressed on non-erythroid cell types, including myeloid and bone cells. Immune cells also participate in bone homeostasis. B cells produce receptor activator of nuclear factor kappa-Β ligand (RANKL) and osteoprotegerin (OPG), two pivotal regulators of bone metabolism. Here we explored the ability of B cells to transdifferentiate into functional osteoclasts and examined the role of EPO in this process in a murine model.

Methods: We have combined specifically-designed experimental mouse models and in vitro based osteoclastogenesis assays, as well as PCR analysis of gene expression.

Results: (i) EPO treatment in vivo increased RANKL expression in bone marrow (BM) B cells, suggesting a paracrine effect on osteoclastogenesis; (ii) B cell-derived osteoclastogenesis occured in vivo and in vitro, as demonstrated by B cell lineage tracing in murine models; (iii) B-cell-derived osteoclastogenesis in vitro was restricted to Pro-B cells expressing CD115/CSF1-R and is enhanced by EPO; (iv) EPO treatment increased the number of B-cell-derived preosteoclasts (β3⁺CD115⁺), suggesting a physiological rationale for B cell derived osteoclastogenesis; (v) finally, mice with conditional EPO-R knockdown in the B cell lineage (cKD) displayed a higher cortical and trabecular bone mass. Moreover, cKD displayed attenuated EPO-driven trabecular bone loss, an effect that was observed despite the fact that cKD mice attained higher hemoglobin levels following EPO treatment.

Conclusions: Our work highlights B cells as an important extra-erythropoietic target of EPO-EPO-R signaling and suggests their involvement in the regulation of bone homeostasis and possibly in EPO-stimulated erythropoietic response. Importantly, we present here for the first time, histological evidence for B cell-derived osteoclastogenesis in vivo.

Megakaryocytes promote osteoclastogenesis in aging

Megakaryocytes (MKs) support bone formation by stimulating osteoblasts (OBs) and inhibiting osteoclasts (OCs). Aging results in higher bone resorption, leading to bone loss. Whereas previous studies showed the effects of aging on MK-mediated bone formation, the effects of aging on MK-mediated OC formation is poorly understood. Here we examined the effect of thrombopoietin (TPO) and MK-derived conditioned media (CM) from young (3-4 months) and aged (22-25 months) mice on OC precursors. Our findings showed that aging significantly increased OC formation in vitro. Moreover, the expression of the TPO receptor, Mpl, and circulating TPO levels were elevated in the bone marrow cavity. We previously showed that MKs from young mice secrete factors that inhibit OC differentiation. However, rather than inhibiting OC development, we found that MKs from aged mice promote OC formation. Interestingly, these age-related changes in MK functionality were only observed using female MKs, potentially implicating the sex steroid, estrogen, in signaling. Further, RANKL expression was highly elevated in aged MKs suggesting MK-derived RANKL signaling may promote osteoclastogenesis in aging. Taken together, these data suggest that modulation in TPO-Mpl expression in bone marrow and age-related changes in the MK secretome promote osteoclastogenesis to impact skeletal aging.

Effects of denosumab versus teriparatide in glucocorticoid-induced osteoporosis patients with prior bisphosphonate treatment

Introduction

Osteoporosis is one of the serious adverse effects associated with glucocorticoid therapy. Although bisphosphonates have been used for glucocorticoid-induced osteoporosis (GIO), some patients have shown an inadequate response. In such cases, denosumab or teriparatide are used. However, there is no consensus on which of these two drugs is superior. We prospectively compared denosumab's and teriparatide's effects on the bone mineral density (BMD) in GIO patients with prior bisphosphonate treatment.

Materials and methods

After receiving oral bisphosphonates for ≥2 years, GIO patients with low T-score BMD (<−2.5) were switched from bisphosphonates to denosumab (n = 20) or daily teriparatide (n = 21). We measured the BMD (lumbar spine, femoral neck, and total hip) in both groups every 6 months for 24 months.

Results

At 24 months of treatment, the lumbar spine BMD increased significantly from baseline in both the denosumab and teriparatide groups (baseline vs. denosumab and teriparatide; 5.9 ± 5.6%, P < 0.001 and 7.9 ± 5.4%, P < 0.001). A significant increase in femoral neck BMD from baseline occurred only in the teriparatide group (6.6 ± 10.8%, P < 0.05); denosumab (1.5 ± 5.0%). No significant changes occurred in the total hip BMD from baseline in either group (−0.1 ± 5.6% and 3.3 ± 7.5%, respectively). There was no significant difference between the denosumab and teriparatide groups at 24 months in lumbar spine and femoral neck BMD, but was significantly higher in the teriparatide group at 12 months (P < 0.01 and P < 0.05 in the lumbar spine and femoral neck, respectively).

Conclusion

Teriparatide might have some advantages over denosumab and be a good alternative for treating GIO patients with prior bisphosphonate treatment.

•

We compared the effects of denosumab and teriparatide on BMD in GIO patients with prior bisphosphonate treatment.

•

At 24 months, teriparatide increased lumbar spine and femoral neck BMD, whereas denosumab increased lumbar spine BMD only.

•

At 12 months, teriparatide increased lumbar spine and femoral neck BMD more than denosumab.

•

Teriparatide might have some advantages over denosumab in GIO patients with prior bisphosphonate treatment.

Role of the bone microenvironment in bone metastasis of malignant tumors - therapeutic implications

BACKGROUND

Bone is one of the most common sites for solid tumor metastasis. Bone metastasis of a malignant tumor seriously affects the quality of life and the overall survival of patients. Evidence has suggested that bone provides a favorable microenvironment that enables disseminated tumor cells to home, proliferate and colonize, leading to the formation of metastases. In the process of bone metastasis the bone microenvironment may be considered as an orchestra that plays a dissonant melody through blending (e.g. cross-talk between osteoclasts, osteoblasts and/or other cells), adding (e.g. a variety of biological factors) or taking away (e.g. blocking a specific pathway) players.

CONCLUSIONS

Here, we review the normal bone microenvironment, bone microenvironment-related factors that promote bone metastasis, as well as mechanisms underlying bone metastasis. In addition, we elude on directions for clinical bone metastasis management, focusing on potential therapeutic approaches to target bone microenvironment-related factors, including bisphosphonate, denosumab, CXCR4/CXCL12 antagonists and cathepsin K inhibitors.

RANK and RANKL Expression in Salivary Gland Tumors

OBJECTIVES

The pathogenesis and molecular basis of salivary gland tumors (SGT) are not well understood. We investigated the expression of receptor activator of nuclear factor κB (RANK) and RANK ligand (RANKL) in benign and malignant SGTs and their relationship with clinicopathological features.

METHODS

Fifty malignant and 38 benign SGTs were analyzed in this study. We evaluated the correlation between RANK and RANKL expression and benign and malignant tumors, as well as the correlation between clinicopathological prognostic parameters and RANK and RANKL expression.

RESULTS

Receptor activator of nuclear factor κB was positive in 82% (41) malignant SGTs and in 34.2% (13) benign SGTs. Receptor activator of nuclear factor κB ligand was expressed in 28% (14) malignant and 5.3% (2) benign tumors. Receptor activator of nuclear factor κB and RANKL expression were significantly different between benign and malignant SGTs (P < .001, P = .006, respectively). However, a relationship was not found between positive expression of RANK or RANKL and clinicopathological features.

CONCLUSIONS

In our study, RANK and RANKL expression was found to be higher in malignant SGTs compared to benign SGTs and RANK was more sensitive than RANKL. In addition, RANK and RANKL expression was higher in some malignant histological subtypes. Based on these results, we think that RANK and RANKL expression in SGTs and its potential as a target for treatment should continue to be investigated.

Review of Secondary Causes of Osteoporotic Fractures Due to Diabetes and Spinal Cord Injury

PURPOSE OF REVIEW

The aim of this review is to gain a better understanding of osteoporotic fractures and the different mechanisms that are driven in the scenarios of bone disuse due to spinal cord injury and osteometabolic disorders due to diabetes.

RECENT FINDINGS

Despite major advances in understanding the pathogenesis, prevention, and treatment of osteoporosis, the high incidence of impaired fracture healing remains an important complication of bone loss, leading to marked impairment of the health of an individual and economic burden to the medical system. This review underlines several pathways leading to bone loss and increased risk for fractures. Specifically, we addressed the different mechanisms leading to bone loss after a spinal cord injury and diabetes. Finally, it also encompasses the changes responsible for impaired bone repair in these scenarios, which may be of great interest for future studies on therapeutic approaches to treat osteoporosis and osteoporotic fractures.

Pros and Cons of Denosumab Treatment for Osteoporosis and Implication for RANKL Aptamer Therapy

Osteoporosis is age-related deterioration in bone mass and micro-architecture. Denosumab is a novel human monoclonal antibody for osteoporosis. It is a receptor activator of nuclear factor-κB ligand (RANKL) inhibitor, which binds to and inhibits osteoblast-produced RANKL, in turn reduces the binding between RANKL and osteoclast receptor RANK, therefore decreases osteoclast-mediated bone resorption and turnover. However, adverse events have also been reported after denosumab treatment, including skin eczema, flatulence, cellulitis and osteonecrosis of the jaw (ONJ). Extensive researches on the mechanism of adverse reactions caused by denosumab have been conducted and may provide new insights into developing new RANKL inhibitors that achieve better specificity and safety. Aptamers are single-stranded oligonucleotides that can bind to target molecules with high specificity and affinity. They are screened from large single-stranded synthetic oligonucleotides and enriched by a technology named SELEX (systematic evolution of ligands by exponential enrichment). With extra advantages such as high stability, low immunogenicity and easy production over antibodies, aptamers are hypothesized to be promising candidates for therapeutic drugs targeting RANKL to counteract osteoporosis. In this review, we focus on the pros and cons of denosumab treatment in osteoporosis and the implication for novel aptamer treatment.

Delayed Denosumab Injections and Bone Mineral Density Response: An Electronic Health Record-based Study

CONTEXT

Discontinuation of denosumab leads to a rapid reversal of its therapeutic effect. However, there are no data regarding how unintended delays or missed injections of denosumab impact bone mineral density (BMD) response.

OBJECTIVE

We examined the association of delays in injections of denosumab with BMD change.

DESIGN

We used electronic medical records from two academic hospitals from 2010 to 2017.

PARTICIPANTS

Patients older than 45 years of age and used at least 2 doses of 60 mg denosumab. Denosumab adherence was evaluated by the medication coverage ratio (MCR). Good adherence corresponds to a dosing interval ≤7 months (defined by MCR ≥93%), moderate adherence corresponds to an interval of 7 to 10 months (MCR 75%-93%), and poor adherence corresponds to an interval ≥10 months (MCR ≤75%).

OUTCOME MEASURES

Annualized percent BMD change from baseline at the lumbar spine, total hip, and femoral neck.

RESULTS

We identified 938 denosumab injections among 151 patients; the mean (SD) age was 69 (10) years, and 95% were female. Patients with good adherence had an annualized BMD increase of 3.9% at the lumbar spine, compared with patients with moderate (3.0%) or poor adherence (1.4%, P for trend .002). Patients with good adherence had an annualized BMD increase of 2.1% at the total hip, compared with patients with moderate (1.3%) or poor adherence (0.6%, P for trend .002).

CONCLUSIONS

A longer interval between denosumab injections is associated with suboptimal BMD response at both spine and total hip. Strategies to improve the timely administration of denosumab in real-world settings are needed.

Denosumab in giant cell tumour of bone in the pelvis and sacrum: Long-term therapy or bone resection?

INTRODUCTION

Surgery of GCTB in sacrum and pelvis is challenging, with high rates of complications and local recurrence. Denosumab can consolidate the peripheral rim of the tumour, thus reducing the rate of morbidities of surgery. The aim of this paper is to evaluate the use of denosumab in pelvic/sacrum giant cell tumours of bone (GCTB).

PATIENTS AND METHODS

We retrospectively reviewed a cohort of 26 patients with aggressive GCTB in sacrum or pelvis treated with denosumab at two referral centres. Clinical response and local recurrence were recorded and the radiologic responses were evaluated with the MDA criteria.

RESULTS

69% of the pelvic GCTB treated with denosumab presented partial or good radiologic responses (type 2A or 2B) after 49 weeks of treatment. Denosumab was administered as adjuvant therapy prior and after surgery in 11 patients (group A), and as the only treatment in 15 patients (group B). In group A, 62% of local recurrence was observed in patients treated with intralesional curettage. No recurrences were identified after en bloc resection. In group B, 9 patients were on continuous bimonthly long term denosumab administration with type 2A and 2B responses. Six patients stopped denosumab and 66% remained stable after 10 months of follow-up.

CONCLUSIONS

Long-term denosumab therapy can be considered with curative intent for pelvic and sacrum GCTB. If surgical intervention is required wide resection may be advisable to reduce the risk of recurrence.

Cellular Communication in Bone Homeostasis and the Related Anti-osteoporotic Drug Development

Background：Intercellular crosstalk among osteoblast, osteoclast, osteocyte and chondrocyte is involved in the precise control of bone homeostasis. Disruption of this cellular and molecular signaling would lead to metabolic bone diseases such as osteoporosis. Currently a number of anti-osteoporosis interventions are restricted by side effects, complications and long-term intolerance. This review aims to summarize the bone cellular communication involved in bone remodeling and its usage to develop new drugs for osteoporosis. Methods：We searched PubMed for publications from 1 January 1980 to 1 January 2018 to identify relevant and latest literatures, evaluation and prospect of osteoporosis medication were summarized. Detailed search terms were 'osteoporosis', 'osteocyte', 'osteoblast', 'osteoclast', 'bone remodeling', 'chondrocyte', 'osteoporosis treatment', 'osteoporosis therapy', 'bisphosphonates', 'denosumab', 'Selective Estrogen Receptor Modulator (SERM)', 'PTH', 'romosozumab', 'dkk-1 antagonist', 'strontium ranelate'. Results：A total of 170 papers were included in the review. About 80 papers described bone cell interactions involved in bone remodeling. The remaining papers were focused on the novel advanced and new horizons in osteoporosis therapies. Conclusion：There exists a complex signal network among bone cells involved in bone remodeling. The disorder of cell-cell communications may be the underlying mechanism of osteoporosis. Current anti-osteoporosis therapies are effective but accompanied by certain drawbacks simultaneously. Restoring the abnormal signal network and individualized therapy are critical for ideal drug development.

CD39 Produced from Human GMSCs Regulates the Balance of Osteoclasts and Osteoblasts through the Wnt/β-Catenin Pathway in Osteoporosis

Osteoporosis is a disease in which the density and quality of bone are reduced, causing bones to become weak and so brittle that a fall or even mild stresses can cause a fracture. Current drug treatment consists mainly of antiresorptive agents that are unable to stimulate new bone formation. Our recent studies have defined a critical role of gingiva-derived mesenchymal stem cells (GMSCs) in attenuating autoimmune arthritis through inhibition of osteoclast formation and activities, but it remains to be ruled out whether the administration of GMSCs to patients with osteoporosis could also regulate osteoblasts and eventually affect bone formation and protection. With the use of an ovariectomized mouse model, we here demonstrated that adoptive transfer of GMSCs regulated the balance of osteoclasts and osteoblasts, eventually contributing to dynamic bone formation. Validation by RNA sequencing (RNA-seq), single-cell sequencing, revealed a unique population of CD39⁺ GMSC that plays an important role in promoting bone formation. We further demonstrated that CD39 produced from GMSC exerted its osteogenic capacity through the Wnt/β-catenin pathway. Our results not only establish a previously unidentified role and mechanism of GMSC for bone promotion but also a potential therapeutic target for management of patients with osteoporosis and other bone loss conditions.

Tussilagone Inhibits Osteoclastogenesis and Periprosthetic Osteolysis by Suppressing the NF-κB and P38 MAPK Signaling Pathways

Background

Aseptic prosthetic loosening is one of the main factors causing poor prognosis of limb function after joint replacement and requires troublesome revisional surgery. It is featured by wear particle-induced periprosthetic osteolysis mediated by excessive osteoclasts activated in inflammatory cell context. Some natural compounds show antiosteoclast traits with high cost-efficiency and few side effects. Tussilagone (TUS), which is the main functional extract from Tussilago farfara generally used for relieving cough, asthma, and eliminating phlegm in traditional medicine has been proven to appease several RAW264.7-mediated inflammatory diseases via suppressing osteoclast-related signaling cascades. However, whether and how TUS can improve aseptic prosthetic loosening via modulating osteoclast-mediated bone resorption still needs to be answered.

Methods

We established a murine calvarial osteolysis model to detect the preventative effect of TUS on osteolysis in vivo. Micro-CT scanning and histomorphometric analysis were used to determine the variation of bone resorption and osteoclastogenesis. The anti–osteoclast-differentiation and anti–bone-resorption bioactivities of TUS in vitro were investigated using bone slice resorption pit evaluation, and interference caused by cytotoxicity of TUS was excluded according to the CCK-8 assay results. Quantitative polymerase chain reaction (qPCR) analysis was applied to prove the decreased expression of osteoclast-specific genes after TUS treatment. The inhibitory effect of TUS on NF-κB and p38 MAPK signaling pathways was testified by Western blot and NF-κB-linked luciferase reporter gene assay.

Results

TUS better protected bones against osteolysis in murine calvarial osteolysis model with reduced osteoclasts than those in the control group. In vitro studies also showed that TUS exerted antiosteoclastogenesis and anti–bone-resorption effects in both bone marrow macrophages (BMMs) and RAW264.7 cells, as evidenced by the decline of osteoclast-specific genes according to qPCR. Western blotting revealed that TUS treatment inhibited IκBα degradation and p38 phosphorylation.

Conclusions

Collectively, our studies proved for the first time that TUS inhibits osteoclastogenesis by suppressing the NF-κB and p38 MAPK signaling pathways, therefore serving as a potential natural compound to treat periprosthetic osteolysis-induced aseptic prosthetic loosening.

Denosumab inhibits MCF-7 cell line-induced spontaneous osteoclastogenesis via the RANKL/MALAT1/miR-124 axis

Background

Denosumab is an inhibitor of receptor activator of NF-κB ligand (RANKL), which inhibits bone metastasis (BM) in breast cancer (BC), but does not completely control cancer cell BM in some BC patients. This study was designed to study whether denosumab inhibits human BC cells (MCF-7) cell line-induced spontaneous osteoclastogenesis via RANKL/metastasis-associated lung adenocarcinoma transcript 1 (MALAT1)/miR-124 axis.

Methods

We established a co-culture system of MCF-7-induced spontaneous osteoclastogenesis in RAW 264.7 cells, and denosumab is added into the co-culture system to inhibit RAW 264.7 cell differentiation into osteoclasts. Real-time PCR (RT-PCR), immunofluorescence and western blotting analysis were used to detect gene expression, while tartrate-resistant acid phosphatase (TRAP) staining was used to assess osteoclast formation.

Results

Denosumab inhibits MCF-7 cell line-induced spontaneous osteoclastogenesis, and the inhibition of denosumab was found to be more pronounced after MALAT1 downregulation and miR-124 overexpression. However, MALAT1 knockdown or miR-124 overexpression did not alter RANKL protein expression. Moreover, the dual luciferase gene reporter system showed that miR-124 targeted the inhibition of MALAT1, while si-MALAT1 upregulated miR-124 expression. miR-124-mimics were able to decrease the expression of Rab27a, IL-11, activated T-cell nuclear factor 1 (NFATc1) and TARP protein.

Conclusions

Denosumab inhibits MALAT1 expression by inhibiting RANKL, thereby upregulating miR-124 expression, which ultimately inhibits MCF-7 cell line-induced pseudo osteoclastogenesis.

Pregnenolone Inhibits Osteoclast Differentiation and Protects Against Lipopolysaccharide-Induced Inflammatory Bone Destruction and Ovariectomy-Induced Bone Loss

Osteolytic bone disease is characterized by excessive osteoclast bone resorption leading to increased skeletal fragility and fracture risk. Multinucleated osteoclasts formed through the fusion of mononuclear precursors are the principle cell capable of bone resorption. Pregnenolone (Preg) is the grand precursor of most if not all steroid hormones and have been suggested to be a novel anti-osteoporotic agent. However, the effects of Preg on osteoclast biology and function has yet to be shown. Here we examined the effect of Preg on receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclast formation and bone resorption in vitro, and potential therapeutic application in inflammatory bone destruction and bone loss in vivo. Our in vitro cellular assays demonstrated that Preg can inhibit the formation of TRAP^+ve osteoclast formation as well as mature osteoclast bone resorption in a dose-dependent manner. The expression of osteoclast marker genes CTSK, TRAP, DC-STAMP, ATP6V0d2, and NFATc1 were markedly attenuated. Biochemical analyses of RANKL-induced signaling pathways showed that Preg inhibited the early activation of extracellular regulated protein kinases (ERK) mitogen-activated protein kinase (MAPK) and nuclear factor-κB, which consequently impaired the downstream induction of c-Fos and NFATc1. Using reactive oxygen species (ROS) detection assays, we found that Preg exhibits anti-oxidant properties inhibiting the generation of intracellular ROS following RANKL stimulation. Consistent with these in vitro results, we confirmed that Preg protected mice against local Lipopolysaccharide (LPS)-induced inflammatory bone destruction in vivo by suppressing osteoclast formation. Furthermore, we did not find any observable effect of Preg on osteoblastogenesis and mineralization in vitro. Finally Preg was administered to ovariectomy (OVX)-induced bone loss and demonstrated that Preg prevented systemic OVX-induced osteoporosis. Collectively, our observations provide strong evidence for the use of Preg as anti-osteoclastogenic and anti-resorptive agent for the potential treatment of osteolytic bone conditions.

Interaction of Brucella abortus with Osteoclasts: a Step toward Understanding Osteoarticular Brucellosis and Vaccine Safety

Osteoarticular disease is a frequent complication of human brucellosis. Vaccination remains a critical component of brucellosis control, but there are currently no vaccines for use in humans, and no in vitro models for assessing the safety of candidate vaccines in reference to the development of bone lesions currently exist. While the effect of Brucella infection on osteoblasts has been extensively evaluated, little is known about the consequences of osteoclast infection. Murine bone marrow-derived macrophages were derived into mature osteoclasts and infected with B. abortus 2308, the vaccine strain S19, and attenuated mutants S19vjbR and B. abortus ΔvirB2 While B. abortus 2308 and S19 replicated inside mature osteoclasts, the attenuated mutants were progressively killed, behavior that mimics infection kinetics in macrophages. Interestingly, B. abortus 2308 impaired the growth of osteoclasts without reducing resorptive activity, while osteoclasts infected with B. abortus S19 and S19vjbR were significantly larger and exhibited enhanced resorption. None of the Brucella strains induced apoptosis or stimulated nitric oxide or lactose dehydrogenase production in mature osteoclasts. Finally, infection of macrophages or osteoclast precursors with B. abortus 2308 resulted in generation of smaller osteoclasts with decreased resorptive activity. Overall, Brucella exhibits similar growth characteristics in mature osteoclasts compared to the primary target cell, the macrophage, but is able to impair the maturation and alter the resorptive capacity of these cells. These results suggest that osteoclasts play an important role in osteoarticular brucellosis and could serve as a useful in vitro model for both analyzing host-pathogen interactions and assessing vaccine safety.

The therapeutic efficacy of denosumab for the loss of bone mineral density in glucocorticoid-induced osteoporosis: a meta-analysis

OBJECTIVE

Prevention of steroidal osteoporosis is an important issue. There is no clear consensus on the impact of anti-RANKL antibody (denosumab) on BMD in patients with glucocorticoid-induced osteoporosis (GIO). In this study, we aimed to evaluate the impact of denosumab on BMD loss in patients with GIO.

METHODS

A comprehensive systematic review and meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. PubMed, Web of Science and Google Scholar were used to search for original studies reported about BMD in patients with GIO treated with denosumab. In meta-analysis of BMD, the mean difference in the rate of change from baseline and the 95% CI were calculated using the random effects model. The mean differences in patients treated with denosumab were compared with those in patients treated with bisphosphonates.

RESULTS

Out of 713 studies identified, seven studies met the selection criteria for the meta-analysis. At 6 and 12 months of denosumab therapy, increases in BMD were observed in the lumbar spine (2.99% [95% CI 2.71, 3.28] and 4.59% [95% CI 4.17, 5.01]), total hip (1.34% [95% CI 0.64, 2.04] and 2.16% [95% CI 2.05, 2.27]) and femoral neck (0.12% [95% CI -0.38, 0.62] and 1.55% [95% CI 0.45, 2.65]). Additionally, denosumab resulted in significant increases in BMD in the lumbar spine and femoral neck at 12 months compared with bisphosphonate therapy.

CONCLUSION

Patients with GIO experienced significant increases in BMD in response to treatment with denosumab that were detected in the lumbar spine, total hip and femoral neck at 12 months.