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

Calcium Homeostasis: A Potential Vicious Cycle of Bone Metastasis in Breast Cancers

Cancers have been considered as one of the most severe health problems in the world. Efforts to elucidate the cancer progression reveal the importance of bone metastasis for tumor malignancy, one of the leading causes for high mortality rate. Multiple cancers develop bone metastasis, from which breast cancers exhibit the highest rate and have been well-recognized. Numerous cells and environmental factors have been believed to synergistically facilitate bone metastasis in breast cancers, from which breast cancer cells, osteoclasts, osteoblasts, and their produced cytokines have been well-recognized to form a vicious cycle that aggravates tumor malignancy. Except the cytokines or chemokines, calcium ions are another element largely released from bones during bone metastasis that leads to hypercalcemia, however, have not been well-characterized yet in modulation of bone metastasis. Calcium ions act as a type of unique second messenger that exhibits omnipotent functions in numerous cells, including tumor cells, osteoclasts, and osteoblasts. Calcium ions cannot be produced in the cells and are dynamically fluxed among extracellular calcium pools, intracellular calcium storages and cytosolic calcium signals, namely calcium homeostasis, raising a possibility that calcium ions released from bone during bone metastasis would further enhance bone metastasis and aggravate tumor progression via the vicious cycle due to abnormal calcium homeostasis in breast cancer cells, osteoclasts and osteoblasts. TRPs, VGCCs, SOCE, and P2Xs are four major calcium channels/routes mediating extracellular calcium entry and affect calcium homeostasis. Here we will summarize the overall functions of these four calcium channels in breast cancer cells, osteoclasts and osteoblasts, providing evidence of calcium homeostasis as a vicious cycle in modulation of bone metastasis in breast cancers.

miR-128 plays a critical role in murine osteoclastogenesis and estrogen deficiency-induced bone loss

Postmenopausal osteoporosis (PMOP) is a severe health issue faced by postmenopausal women. microRNA-128 (miR-128) is associated with aging, inflammatory signaling, and inflammatory diseases, such as PMOP. It has also been reported to modulate in vitro osteogenic/adipogenic differentiation. However, its function in osteoclast formation is unknown.

Methods: First, the expression of miR-128 and nuclear factor of activated T cells 1 (Nfatc1, bone resorption master marker) was investigated in bone tissues derived from PMOP patients, while their correlation to each other was also investigated. The levels of miR-128 and Nfatc1 in bone specimens and bone marrow-derived macrophages (BMMs) from mice subjected to ovariectomy (OVX) were also assayed. Next, we employed mice BMMs modified for overexpression and inhibition of miR-128 levels to determine its effect on osteoclast differentiation. Moreover, we generated osteoclastic miR-128 conditional knockout (miR-128^Oc-/-) mice and isolated miR-128 deletion-BMMs to observe its biological function on bone phenotype and osteoclastogenesis in vivo, respectively. The miR-128^Oc-/- BMMs were used to explore the downstream regulatory mechanisms using pull-down, luciferase reporter, and western-blotting assays. Finally, the impact of miR-128 deficiency on OVX-induced bone loss in mice was evaluated.

Results: The miR-128 level was found to be positively correlated with the increase in Nfatc1 level in mouse/human bone specimens and mouse primary BMMs. In vitro experiments demonstrated miR-128 levels that were dependent on activity of osteoclast differentiation and miR-128 overexpression or inhibition in BMMs significantly increased or decreased osteoclastogenesis, respectively. In vivo, we revealed that osteoclastic miR-128 deletion remarkedly increased bone mass through the inhibition of osteoclastogenesis. Mechanistically, we identified sirtuin 1 (SIRT1) as the direct target of miR-128 at the post-transcriptional level during osteoclast differentiation. Increased levels of SIRT1 reduced nuclear factor κB (NF-κB) activity by decreasing the level of acetylation of Lysine 310, as well as inhibiting tumor necrosis factor-α (Tnf-α) and interleukin 1 (IL-1) expressions. Lastly, osteoclastic deletion of miR-128 significantly suppressed OVX-triggered osteoclastogenesis and exerted a protective effect against bone loss in mice.

Conclusions: Our findings reveal a critical mechanism for osteoclastogenesis that is mediated by the miR-128/SIRT1/NF-κB signaling axis, highlighting a possible avenue for the further exploration of diagnostic and therapeutic target molecules in PMOP.

In silico experiments of bone remodeling explore metabolic diseases and their drug treatment

Bone structure and function are maintained by well-regulated bone metabolism and remodeling. Although the underlying molecular and cellular mechanisms are now being understood, physiological and pathological states of bone are still difficult to predict due to the complexity of intercellular signaling. We have now developed a novel in silico experimental platform, V-Bone, to integratively explore bone remodeling by linking complex microscopic molecular/cellular interactions to macroscopic tissue/organ adaptations. Mechano-biochemical couplings modeled in V-Bone relate bone adaptation to mechanical loading and reproduce metabolic bone diseases such as osteoporosis and osteopetrosis. V-Bone also enables in silico perturbation on a specific signaling molecule to observe bone metabolic dynamics over time. We also demonstrate that this platform provides a powerful way to predict in silico therapeutic effects of drugs against metabolic bone diseases. We anticipate that these in silico experiments will substantially accelerate research into bone metabolism and remodeling.

RANK/RANKL Acts as a Protective Factor by Targeting Cholangiocytes in Primary Biliary Cholangitis

BACKGROUND

Primary biliary cholangitis (PBC) is an autoimmune liver disease characterized by the highly selective autoimmune injury of small intrahepatic bile ducts. Studies reported that the cholangiocytes from PBC patients expressed significantly higher levels of both receptor activator of nuclear factor-kappa B (RANK) and its ligand RANKL. However, the accurate role of RANK/RANKL axis in PBC remains unclear.

METHODS

Forty patients with PBC were enrolled according to the inclusion criteria. The biochemical parameters (alkaline phosphatase, ALP; gamma-glutamyltransferase, GGT; alanine aminotransferase, ALT; aspartate transaminase, AST; total bilirubin, TB) were collected at baseline and followed-up after 6 months of treatment with ursodeoxycholic acid (UDCA, 15 mg/kg d). Stages of PBC were diagnosed based on liver biopsy histopathology according to Nakanuma's criteria. RANK expression in hepatic tissues was detected by immunohistochemistry. The cellular immunofluorescence method was used to locate the distribution of RANK in the human intrahepatic biliary epithelial cells (HIBECs) cultured in vitro. HIBECs were treated with RANKL at a concentration of 100 ng/ml or transfected with RANK-overexpressing lentivirus (LV-RANK). CCK-8 assay and cell cycle assay were used to detect the cell proliferation. Real-time PCR was used to detect the expression of IL-6, E-cadherin, VCAM, ICAM-1, TNF-α, and CD80.

RESULTS

RANK expression in liver biopsies from early PBC patients (stage I + stage II) was significantly lower than that from advanced PBC patients (stage III + stage IV) (1.7 ± 0.63 vs. 2.3 ± 0.45 scores, P < 0.05). High-RANK patients seemed to have better response to UDCA than low-RANK patients (88.9% vs. 40.9%, P < 0.05). The baseline biochemical parameters between the two groups were comparable. The decline percentages of ALP and GGT after UDCA treatment were more obvious in high-RANK patients than those in low-RANK patients (53.90% ± 9.82% vs. 23.93% ± 6.24%, P < 0.05; 74.11% ± 7.18% vs. 48.00% ± 8.17%, P < 0.05, respectively). HIBECs proliferation was significantly inhibited after treatment of RANKL or transfection with LV-RANK. Increased expression of IL-6 and E-cadherin was observed in HIBECs treated with RANKL or LV-RANK.

CONCLUSION

The overall hepatic RANK expression was associated with disease severity and biochemical response in PBC patients. Activation of RANK/RANKL signaling pathway inhibited cholangiocytes proliferation in vitro. Our study suggested that RANK/RANKL pathway might be a potential target of immunotherapy of PBC based on its involvement in the occurrence and development of the disease.

Dynamic changes of Receptor activator of nuclear factor-κB expression in Circulating Tumor Cells during Denosumab predict treatment effectiveness in Metastatic Breast Cancer

Receptor-activator of nuclear-factor -κB-ligand (RANKL) and its receptor RANK have been recently identified as key players in breast cancer bone metastases. Since Circulating Tumor Cells (CTCs) are considered a crucial step of metastatic process, we explored RANK expression on CTCs in metastatic breast cancer (MBC), and the predictive value of RANK-positive CTCs in monitoring patients during treatment with denosumab (anti-RANKL antibody). To this purpose, we developed a novel CTC assay to quantify RANK-positive CTCs in forty-two bone MBC patients, candidates to denosumab treatment. Companion algorithms ΔAUC and Slope were developed, and correlated with time to first skeletal-related-events (SRE), time to bone metastasis progression and time to visceral metastasis progression. Twenty-seven patients had at least one CTC at baseline and, among these, nineteen (70%) had one or more RANK-positive CTCs. Notably, the baseline total CTCs, but not the RANK-positive, were associated with Time-to-first-SRE, Time-to-Bone-Metastasis-Progression and Time-to-Visceral-Metastasis-Progression. Conversely, during treatment monitoring, positive ΔAUC value, expression of RANK-positive CTCs persistence, correlated with longer Time-to-first-SRE (p = 0.0002) and Time-to-Bone-Metastasis-Progression (p = 0.0012). Furthermore, the early increase at second day, in RANK-positive CTCs (Positive-Slope) was associated with delay in time-to-first-SRE (p = 0.0038) and Time-to-Bone-Metastasis-Progression (p = 0.0024). We demonstrate, for the first time, the expression of RANK on CTCs in MBC patients and that the persistence of RANK expression determines denosumab effectiveness.

Role of RANK-L as a potential inducer of ILC2-mediated type 2 inflammation in chronic rhinosinusitis with nasal polyps

Chronic rhinosinusitis with nasal polyps (CRSwNP) is characterized by type 2 inflammation with accumulation of activated group 2 innate lymphoid cells (ILC2s) and elevation of thymic stromal lymphopoietin (TSLP). A member of the TNF superfamily (TNFSF), TNFSF15, is known to induce the production of type 2 cytokines in ILC2s. Although ILC2s have been implicated in CRSwNP, the presence and role of TNFSFs in ILC2-mediated type 2 inflammation in CRSwNP has not been elucidated. Here, we investigate the involvement of TNFSFs in ILC2-mediated type 2 inflammation in CRSwNP. We found that receptor activator of NF-κB (RANK) ligand (RANK-L (TNFSF11)) was significantly elevated in nasal polyps (NPs), and that the receptor of RANK-L, RANK, was expressed on ILC2s in human peripheral blood and NPs. An agonistic antibody against RANK induced production of type 2 cytokines in human ILC2s, and TSLP significantly enhanced this reaction. The membrane-bound RANK-L was detected mainly on CD45 + immune cells, including T_H2 cells in NPs. The co-culture of NP-derived ILC2s and T_H2 cells significantly enhanced production of type 2 cytokines, and anti-RANK-L monoclonal antibody suppressed this enhancement. In conclusion, RANK-L, together with TSLP, may play an inductive role in the ILC2-mediated type 2 inflammation in CRSwNP.

Structure and Optimization of Checkpoint Inhibitors

With the advent of checkpoint inhibitor treatment for various cancer types, the optimization of drug selection, pharmacokinetics and biomarker assays is an urgent and as yet unresolved dilemma for clinicians, pharmaceutical companies and researchers. Drugs which inhibit cytotoxic T-lymphocyte associated protein-4 (CTLA-4), such as ipilimumab and tremelimumab, programmed cell death protein-1 (PD-1), such as nivolumab and pembrolizumab, and programmed cell death ligand-1 (PD-L1), such as atezolizumab, durvalumab and avelumab, each appear to have varying pharmacokinetics and clinical activity in different cancer types. Each drug differs in terms of dosing, which becomes an issue when drug comparisons are attempted. Here, we examine the various checkpoint inhibitors currently used and in development. We discuss the antibodies and their protein targets, their pharmacokinetics as measured in various tumor types, and their binding affinities to their respective antigens. We also examine the various dosing regimens for these drugs and how they differ. Finally, we examine new developments and methods to optimize delivery and efficacy in the field of checkpoint inhibitors, including non-fucosylation, prodrug formations, bispecific antibodies, and newer small molecule and peptide checkpoint inhibitors.

Genetics' Piece of the PI: Inferring the Origin of Complex Traits and Diseases from Proteome-Wide Protein-Protein Interaction Dynamics

How do common and rare genetic polymorphisms contribute to quantitative traits or disease risk and progression? Multiple human traits have been extensively characterized at the genomic level, revealing their complex genetic architecture. However, it is difficult to resolve the mechanisms by which specific variants contribute to a phenotype. Recently, analyses of variant effects on molecular traits have uncovered intermediate mechanisms that link sequence variation to phenotypic changes. Yet, these methods only capture a fraction of genetic contributions to phenotype. Here, in reviewing the field, it is proposed that complex traits can be understood by characterizing the dynamics of biochemical networks within living cells, and that the effects of genetic variation can be captured on these networks by using protein-protein interaction (PPI) methodologies. This synergy between PPI methodologies and the genetics of complex traits opens new avenues to investigate the molecular etiology of human diseases and to facilitate their prevention or treatment.

Pharmacodynamics of Pre-Operative PD1 checkpoint blockade and receptor activator of NFkB ligand (RANKL) inhibition in non-small cell lung cancer (NSCLC): study protocol for a multicentre, open-label, phase 1B/2, translational trial (POPCORN)

Background

Neoadjuvant immunotherapy targeting immune checkpoint programmed death-1 (PD-1) is under investigation in various tumour settings including non-small-cell lung cancer (NSCLC). Preclinical models demonstrate the superior power of the immunotherapy provided in a neoadjuvant (pre-operative) compared with an adjuvant (post-operative) setting to eradicate metastatic disease and induce long-lasting antigen-specific immunity. Novel effective immunotherapy combinations are widely sought in the oncology field, targeting non-redundant mechanisms of immune evasion. A promising combination partner with anti-PD1 in NSCLC is denosumab, a monoclonal antibody blocking receptor activator of NF-κB ligand (RANKL). In preclinical cancer models and in a large retrospective case series in NSCLC, anti-cancer activity has been reported for the combination of immune checkpoint inhibition (ICI) and denosumab. Furthermore, clinical trials of ICI and denosumab are underway in advanced melanoma and clear-cell renal cell carcinoma. However, the mechanism of action of combination anti-PD1 and anti-RANKL is poorly defined.

Methods

This open-label multicentre trial will randomise by minimisation 30 patients with resectable stage IA (primary > 2 cm) to IIIA NSCLC to a neoadjuvant treatment regime of either two doses of nivolumab (3 mg/kg every 2 weeks) or two doses of nivolumab (same regimen) plus denosumab (120 mg every 2 weeks, following nivolumab). Each treatment arm is of equal size and will be approximately balanced with respect to histology (squamous vs. non-squamous) and clinical stage (I-II vs. IIIA). All patients will receive surgery for their tumour 2 weeks after the final dose of neoadjuvant therapy. The primary outcome will be translational research to define the tumour-immune correlates of combination therapy compared with monotherapy. Key secondary outcomes will include a comparison of rates of the following between each arm: toxicity, response (pathological and radiological), and microscopically complete resection.

Discussion

The POPCORN study provides a unique platform for translational research to determine the mechanism of action of a novel proposed combination immunotherapy for cancer.

Trial registration

Prospectively registered on Australian New Zealand Clinical Trials Registry (ACTRN12618001121257) on 06/07/2018.

Osteoporosis in Rheumatic Diseases

Osteoporosis is a chronic disease characterized by an increased risk of fragility fracture. Patients affected by rheumatic diseases are at greater risk of developing osteoporosis. The purpose of the present review is to discuss the pathogenesis, epidemiology, and treatment of osteoporosis in patients affected by rheumatic diseases with special focus for rheumatoid arthritis, psoriatic arthritis, spondyloarthritis, systemic lupus erythematosus, systemic sclerosis, vasculitides, Sjogren syndrome, and crystal-induced arthritis.

Regulation of the Bone Vascular Network is Sexually Dimorphic

Osteoblast (OB) lineage cells are an important source of vascular endothelial growth factor (VEGF), which is critical for bone growth and repair. During bone development, pubertal differences in males and females exist, but little is known about whether VEGF signaling contributes to skeletal sexual dimorphism. We have found that in mice, conditional disruption of VEGF in osteocalcin-expressing cells (OcnVEGFKO) exerts a divergent influence on morphological, cellular, and whole bone properties between sexes. Furthermore, we describe an underlying sexual divergence in VEGF signaling in OB cultures in vitro independent of circulating sex hormones. High-resolution synchrotron computed tomography and backscattered scanning electron microscopy revealed, in males, extensive unmineralized osteoid encasing enlarged blood vessel canals and osteocyte lacunae in cortical bone after VEGF deletion, which contributed to increased porosity. VEGF was deleted in male and female long bone-derived OBs (OBVEGKO) in vitro and Raman spectroscopic analyses of mineral and matrix repertoires highlighted differences between male and female OBVEGFKO cells, with increased immature phosphate species prevalent in male OBVEGFKO cultures versus wild type (WT). Further sexual dimorphism was observed in bone marrow endothelial cell gene expression in vitro after VEGF deletion and in sclerostin protein expression, which was increased in male OcnVEGFKO bones versus WT. The impact of altered OB matrix composition after VEGF deletion on whole bone geometry was assessed between sexes, although significant differences between OcnVEGFKO and WT were identified only in females. Our results suggest that bone-derived VEGF regulates matrix mineralization and vascularization distinctly in males and females, which results in divergent physical bone traits.

The PPAR-γ antagonist T007 inhibits RANKL-induced osteoclastogenesis and counteracts OVX-induced bone loss in mice

Background

Osteoclasts are key determinant cellular components implicated in the development and progression of disorders driven by bone damage. Herein, we studied the upshot of T007, an antagonist of peroxisome proliferator-activated receptor-gamma (PPARγ), on osteoclastogenesis using cell and animal models.

Results

The in vitro assays revealed that T007 hindered the osteoclastogenesis caused by the treatment with the receptor activator of nuclear factor-κB ligand (RANKL) through inhibiting the levels of PPARγ in cells. The PPARγ siRNA partially reproduced the inhibitory action of T007. The opposite findings were produced after PPARγ overexpression. Furthermore, T007 prevented from bone loss in a mouse model of osteoporosis induced by ovariectomy (OVX). These findings implied that T007 is a potential efficient drug for the prophylaxis and cure of osteoclast-related disorders.

Conclusions

Taken together, our findings demonstrated that T007 impedes osteoclastogenesis and will be useful for the therapy of bone related diseases, essentially osteoporosis.

HTLV-1 viral oncogene HBZ drives bone destruction in adult T cell leukemia

Osteolytic bone lesions and hypercalcemia are common, serious complications in adult T cell leukemia/lymphoma (ATL), an aggressive T cell malignancy associated with human T cell leukemia virus type 1 (HTLV-1) infection. The HTLV-1 viral oncogene HBZ has been implicated in ATL tumorigenesis and bone loss. In this study, we evaluated the role of HBZ on ATL-associated bone destruction using HTLV-1 infection and disease progression mouse models. Humanized mice infected with HTLV-1 developed lymphoproliferative disease and continuous, progressive osteolytic bone lesions. HTLV-1 lacking HBZ displayed only modest delays to lymphoproliferative disease but significantly decreased disease-associated bone loss compared with HTLV-1-infected mice. Gene expression array of acute ATL patient samples demonstrated increased expression of RANKL, a critical regulator of osteoclasts. We found that HBZ regulated RANKL in a c-Fos-dependent manner. Treatment of HTLV-1-infected humanized mice with denosumab, a monoclonal antibody against human RANKL, alleviated bone loss. Using patient-derived xenografts from primary human ATL cells to induce lymphoproliferative disease, we also observed profound tumor-induced bone destruction and increased c-Fos and RANKL gene expression. Together, these data show the critical role of HBZ in driving ATL-associated bone loss through RANKL and identify denosumab as a potential treatment to prevent bone complications in ATL patients.

Osteoblast-specific expression of Panx3 is dispensable for postnatal bone remodeling

Since cost-effective osteoanabolic treatment options remain to be established, it is relevant to identify specific molecules physiologically regulating osteoblast differentiation and/or activity that are principally accessible as drug targets. Specific or predominant gene expression in a given cell type often predicts a relevant function in the respective tissue. Thus, we aimed to identify genes encoding membrane-associated proteins with selective expression in differentiated osteoblasts. We therefore applied an unbiased approach, i.e. Affymetrix Gene Chip hybridization, to compare global gene expression in primary murine osteoblasts at two stages of differentiation. For the most strongly induced genes we analyzed their expression pattern in different tissues, which led us to identify known and unknown osteoblast differentiation markers with predominant expression in bone. One of these genes was Panx3, encoding a transmembrane hemichannel with ill-defined function in skeletal remodeling. To decipher the role of Panx3 in osteoblasts we first generated Panx3-fl/fl mice carrying a Runx2-Cre transgene. Using undecalcified histology followed by bone-specific histomorphometry we did not observe any significant difference between 24 weeks old Cre-negative and Cre-positive littermates. We additionally generated and analyzed mice with ubiquitous Panx3 deletion, where a delay of endochondral ossification did not translate into a detectable skeletal phenotype after weaning, possibly explained by compensatory induction of Panx1. Of note, newborn Panx3-deficient mice displayed significantly reduced serum glucose levels, which was not the case in older animals. Our findings demonstrate that Panx3 expression in osteoblasts is not required for postnatal bone remodeling, which essentially rules out its suitability as a target protein for osteoanabolic medication.

Specific RANK Cytoplasmic Motifs Drive Osteoclastogenesis

Upon receptor activator of NF-κB ligand (RANKL) binding, RANK promotes osteoclast formation through the recruitment of tumor necrosis factor (TNF) receptor-associated factors (TRAFs). In vitro assays identified two RANK intracellular motifs that bind TRAFs: PVQEET^560-565 (Motif 2) and PVQEQG^604-609 (Motif 3), which potently mediate osteoclast formation in vitro. To validate the in vitro findings, we have generated knock-in (KI) mice harboring inactivating mutations in RANK Motifs 2 and 3. Homozygous KI (RANK^KI/KI ) mice are born at the predicted Mendelian frequency and normal in tooth eruption. However, RANK^KI/KI mice exhibit significantly more trabecular bone mass than age- and sex-matched heterozygous KI (RANK^+/KI ) and wild-type (RANK^+/+ ) counterparts. Bone marrow macrophages (BMMs) from RANK^KI/KI mice do not form osteoclasts when they are stimulated with macrophage colony-stimulating factor (M-CSF) and RANKL in vitro. RANKL is able to activate the NF-κB, ERK, p38, and JNK pathways in RANK^KI/KI BMMs, but it cannot stimulate c-Fos or NFATc1 in the RANK^KI/KI cells. Previously, we showed that RANK signaling plays an important role in Porphyromonas gingivalis (Pg)-mediated osteoclast formation by committing BMMs into the osteoclast lineage. Here, we show that RANKL-primed RANK^KI/KI BMMs are unable to differentiate into osteoclasts in response to Pg stimulation, indicating that the two RANK motifs are required for Pg-induced osteoclastogenesis. Mechanistically, RANK Motifs 2 and 3 facilitate Pg-induced osteoclastogenesis by stimulating c-Fos and NFATc1 expression during the RANKL pretreatment phase as well as rendering c-Fos and NFATc1 genes responsive to subsequent Pg stimulation. Cell-penetrating peptides (CPPs) conjugated with RANK segments containing Motif 2 or 3 block RANKL- and Pg-mediated osteoclastogenesis. The CPP conjugates abrogate RANKL-stimulated c-Fos and NFATc1 expression but do not affect RANKL-induced activation of NF-κB, ERK, p38, JNK, or Akt signaling pathway. Taken together, our current findings demonstrate that RANK Motifs 2 and 3 play pivotal roles in osteoclast formation in vivo and mediate Pg-induced osteoclastogenesis in vitro.

Dual targeting of RANKL and PD-1 with a bispecific antibody improves anti-tumor immunity

Objectives

The addition of RANKL/RANK blockade to immune checkpoint inhibitors (ICIs) such as anti‐PD‐1/PD‐L1 and anti‐CTLA4 antibodies is associated with increased anti‐tumor immunity in mice. Recent retrospective clinical studies in patients with advanced melanoma and lung cancer suggest the addition of anti‐RANKL antibody to ICI increases the overall response rate relative to ICI treatment alone. Based on this rationale, we developed a novel bispecific antibody (BsAb) co‐targeting RANKL and PD‐1.

Methods

We characterized target binding and functional activity of the anti‐RANKL/PD‐1 BsAb in cell‐based assays. Anti‐tumor activity was confirmed in experimental lung metastasis models and in mice with established subcutaneously transplanted tumors.

Results

The anti‐RANKL/PD‐1 BsAb retained binding to both RANKL and PD‐1 and blocked the interaction with respective counter‐structures RANK and PD‐L1. The inhibitory effect of anti‐RANKL/PD‐1 BsAb was confirmed by demonstrating a complete block of RANKL‐dependent osteoclast formation. Monotherapy activity of anti‐RANKL/PD‐1 BsAb was observed in anti‐PD‐1 resistant tumors and, when combined with anti‐CTLA‐4 mAb, increased anti‐tumor responses. An equivalent or superior anti‐tumor response was observed with the anti‐RANKL/PD‐1 BsAb compared with the combination of parental anti‐RANKL plus anti‐PD‐1 antibodies depending upon the tumor model.

Discussion

Mechanistically, the anti‐tumor activity of anti‐RANKL/PD‐1 BsAb required CD8⁺T cells, host PD‐1 and IFNγ. Targeting RANKL and PD‐1 simultaneously within the tumor microenvironment (TME) improved anti‐tumor efficacy compared with combination of two separate mAbs.

Conclusion

In summary, the bispecific anti‐RANKL/PD‐1 antibody demonstrates potent tumor growth inhibition in settings of ICI resistance and represents a novel modality for clinical development in advanced cancer.

Chemokines in Physiological and Pathological Bone Remodeling

The bone matrix is constantly remodeled by bone-resorbing osteoclasts and bone-forming osteoblasts. These two cell types are fundamentally different in terms of progenitor cells, mode of action and regulation by specific molecules, acting either systemically or locally. Importantly, there is increasing evidence for an impact of cell types or molecules of the adaptive and innate immune system on bone remodeling. Understanding these influences is the major goal of a novel research area termed osteoimmunology, which is of key relevance in the context of inflammation-induced bone loss, skeletal metastases, and diseases of impaired bone remodeling, such as osteoporosis. This review article aims at summarizing the current knowledge on one particular aspect of osteoimmunology, namely the impact of chemokines on skeletal cells in order to regulate bone remodeling under physiological and pathological conditions. Chemokines have key roles in the adaptive immune system by controlling migration, localization, and function of immune cells during inflammation. The vast majority of chemokines are divided into two subgroups based on the pattern of cysteine residues. More specifically, there are 27 known C-C-chemokines, binding to 10 different C-C receptors, and 17 known C-X-C-chemokines binding to seven different C-X-C receptors. Three additional chemokines do not fall into this category, and only one of them, i.e., CX3CL1, has been shown to influence bone remodeling cell types. There is a large amount of published studies demonstrating specific effects of certain chemokines on differentiation and function of osteoclasts and/or osteoblasts. Chemokine signaling by skeletal cells or by other cells of the bone marrow niche regulates bone formation and resorption through autocrine and paracrine mechanisms. In vivo evidence from mouse deficiency models strongly supports the role of certain chemokine signaling pathways in bone remodeling. We will summarize these data in the present review with a special focus on the most established subsets of chemokines. In combination with the other review articles of this issue, the knowledge presented here confirms that there is a physiologically relevant crosstalk between the innate immune system and bone remodeling cell types, whose molecular understanding is of high clinical relevance.

Function of CSF1 and IL34 in Macrophage Homeostasis, Inflammation, and Cancer

Colony-stimulating factor 1 (CSF1) and interleukin 34 (IL34) signal via the CSF1 receptor to regulate macrophage differentiation. Studies in IL34- or CSF1-deficient mice have revealed that IL34 function is limited to the central nervous system and skin during development. However, the roles of IL34 and CSF1 at homeostasis or in the context of inflammatory diseases or cancer in wild-type mice have not been clarified in vivo. By neutralizing CSF1 and/or IL34 in adult mice, we identified that they play important roles in macrophage differentiation, specifically in steady-state microglia, Langerhans cells, and kidney macrophages. In several inflammatory models, neutralization of both CSF1 and IL34 contributed to maximal disease protection. However, in a myeloid cell-rich tumor model, CSF1 but not IL34 was required for tumor-associated macrophage accumulation and immune homeostasis. Analysis of human inflammatory conditions reveals IL34 upregulation that may account for the protection requirement of IL34 blockade. Furthermore, evaluation of IL34 and CSF1 blockade treatment during Listeria infection reveals no substantial safety concerns. Thus, IL34 and CSF1 play non-redundant roles in macrophage differentiation, and therapeutic intervention targeting IL34 and/or CSF1 may provide an effective treatment in macrophage-driven immune-pathologies.

A new computerized tomography classification to evaluate response to Denosumab in giant cell tumors in the extremities

Objectives

The aim of this study was to describe the cohort of patients who have been treated with Denosumab as neoadjuvant therapy prior to surgery for aggressive giant cell tumor of bone in the extremities, to evaluate the radiological responses to Denosumab comparing Choi criteria and a newly described computerized tomography (CT) classification, and to evaluate the risk of local recurrence after intralesional curettage or radical excision.

Methods

We retrospectively evaluated 36 patients (20 females and 16 males; mean age at diagnosis 36 years (range, 18–64)) treated with neoadjuvant Denosumab therapy prior to surgery for aggressive giant cell tumor of bone in the extremities. The radiological responses to Denosumab treatment were analyzed on the preoperative images after the neoadjuvant course with the Choi criteria and with a newly proposed classification based on CT. All these images were independently reviewed by two of the researchers. Surgical intervention methods were noted and local recurrence rates were evaluated. The correlation between radiological response amount and local recurrence were analyzed for both Choi criteria and the new CT classification.

Results

Denosumab was administered for a mean of 21 weeks (range 7–133). Five patients also had a short postoperative course. According to Choi criteria there was a radiological response in 32 patients (89%), while the new CT classification identified responses in all the 36 patients (100%). The identification of changes after 7 weeks of treatment was higher using the CT classification compared to Choi criteria (p = 0.043 vs p = 0.462). The surgical interventions after Denosumab comprised curettage in 29 patients (74%) and resection in 7 (26%). Local recurrence was higher in patients managed with intralesional curettage than in those treated with en bloc resection (55.1% vs 0%, p < 0.001). At last follow up 19 patients (53%) required en bloc resections. Good responders to Denosumab (type 2C) had lower risk of local recurrence (p = 0.047) after either resection or curettage.

Conclusion

The new CT classification evaluated more accurately the response to Denosumab. Our experience suggests that the requirement for radical bone resection remains high despite the use of Denosumab.

Level of evidence

Level IV, Therapeutic Study.

RANKL blockade suppresses pathological angiogenesis and vascular leakage in ischemic retinopathy

Receptor activator of NF-κB ligand (RANKL) is a member of the TNF superfamily. RANKL increases endothelial permeability and induces angiogenesis, suggesting its critical roles in the vasculature. Despite the evidence implicating RANKL in vascular pathology, its role in ischemic retinopathy has not been previously reported. In this study, neonatal mice were exposed to 75% oxygen from postnatal day (P)7 to P12 to induce vaso-obliteration, and then returned to room air from P12 to P17, causing the retina to become hypoxic and inducing vascular endothelial growth factor (VEGF) signaling, which produces pathological neovascularization. On P12, the mice received a single intravitreal injection of control IgG1 or RANK-Fc, and retinas were obtained at P17. On P17, RANKL was expressed strongly and selectively in the neovascular tufts (NVT) area. RANKL colocalized with αSMA or PDGFRβ in NVT. However, co-immunostaining revealed that CD31-positive areas were not the same as RANKL, which indicates that RANKL might be produced by retinal pericytes, not endothelial cells. Consistent with this finding, chemical hypoxia upregulated RANKL expression in cultured human retinal pericytes but not in endothelial cells. Treatment with RANK-Fc markedly reduced the NVT area compared to that in mice administered the IgG1 injection. In contrast, the central avascular region of RANKL-Fc retina was comparable to the controls. In addition, we assessed retinal vascular permeability using FITC-labeled dextran. RANK-Fc treated mice displayed decreased vascular leakages compared to those injected with IgG1. Our work supports the use of an RANKL blockade as a potential therapeutic approach against ischemic retinopathies.

[The mechanism of anti-RANKL antibody in the treatment of metabolic bone diseases including osteoporosis - possible applications of anti-RANKL antibody to the treatment of cancer patients]

Discovery of RANKL (receptor activator of NF-κB ligand) gave a great impact on identification of the mechanisms regulating osteoclast differentiation and function, establishment of research field bridging bone and mineral research and immunology (osteoimmunology), and development of a fully human anti-RANKL monoclonal neutralizing antibody (denosumab). Denosumab has been clinically available for treatment of osteoporosis and cancer-induced bone diseases in the US, Europe and many countries including Japan. Denosumab is a so-called blockbuster of which sales amount was 3.9 billion US dollars in 2017. Because RANKL is the absolute factor for osteoclast differentiation, anti-RANKL antibody is very effective and its application is good news for many patients. Recent topics are the identification of importance of RANKL on osteoblasts in regulation of osteogenesis and the demonstration of RANKL-RANK (the receptor of RANKL) dual signaling in coupling between bone resorption and bone formation. RANKL reverse signaling that we had hypothesized was demonstrated at last. In this review I describe the mechanism of anti-RANKL antibody in the treatment of metabolic bone diseases including osteoporosis. I also suggest possible applications of anti-RANKL antibody to the treatment of cancer patients.

Bone alterations in inflammatory bowel diseases

Inflammatory bowel diseases (IBDs) are characterized by a multifactorial partially unknown etiology that involves genetic, immunological and environmental factors. Up to 50% of IBD patients experience at least one extraintestinal manifestation; among them is the involvement of bone density which is referred to as metabolic bone disease (MBD), including osteopenia and osteoporosis. Bone alterations in IBDs population appear to have a multifactorial etiology: Decreased physical activity, inflammation-related bone resorption, multiple intestinal resections, dietary malabsorption of minerals and vitamin D deficiency, genetic factors, gut-bone immune signaling interaction, steroid treatment, microbiota and pathogenic micro-organisms interaction, and dietary malabsorption of minerals, that, all together or individually, may contribute to the alteration of bone mineral density. This review aims to summarize the prevalence and pathophysiology of metabolic bone alterations in IBD subjects outlining the main risk factors of bone fragility. We also want to underline the role of the screening and prophylaxis of bone alterations in Crohn’s disease and ulcerative colitis patients and the importance of treating appropriately MBD.

RhoA regulates translation of the Nogo-A decoy SPARC in white matter-invading glioblastomas

Glioblastomas strongly invade the brain by infiltrating into the white matter along myelinated nerve fiber tracts even though the myelin protein Nogo-A prevents cell migration by activating inhibitory RhoA signaling. The mechanisms behind this long-known phenomenon remained elusive so far, precluding a targeted therapeutic intervention. This study demonstrates that the prevalent activation of AKT in gliomas increases the ER protein-folding capacity and enables tumor cells to utilize a side effect of RhoA activation: the perturbation of the IRE1α-mediated decay of SPARC mRNA. Once translation is initiated, glioblastoma cells rapidly secrete SPARC to block Nogo-A from inhibiting migration via RhoA. By advanced ultramicroscopy for studying single-cell invasion in whole, undissected mouse brains, we show that gliomas require SPARC for invading into white matter structures. SPARC depletion reduces tumor dissemination that significantly prolongs survival and improves response to cytostatic therapy. Our finding of a novel RhoA-IRE1 axis provides a druggable target for interfering with SPARC production and underscores its therapeutic value.

Deficiency of sphingosine-1-phosphate receptor 3 does not affect the skeletal phenotype of mice lacking sphingosine-1-phosphate lyase

Albeit osteoporosis is one of the most prevalent disorders in the aged population, treatment options stimulating the activity of bone-forming osteoblasts are still limited. We and others have previously identified sphingosine-1-phosphate (S1P) as a bone remodeling coupling factor, which is released by bone-resorbing osteoclasts to stimulate bone formation. Moreover, S1pr3, encoding one of the five known S1P receptors (S1P3), was found differentially expressed in osteoblasts, and S1P3 deficiency corrected the moderate high bone mass phenotype of a mouse model (deficient for the calcitonin receptor) with increased S1P release from osteoclasts. In the present study we addressed the question, if S1P3 deficiency would also influence the skeletal phenotype of mice lacking S1P-lyase (encoded by Sgpl1), which display markedly increased S1P levels due to insufficient degradation. Consistent with previous reports, the majority of Sgpl1-deficient mice died before or shortly after weaning, and this lethality was not influenced by additional S1P3 deficiency. At 3 weeks of age, Sgpl1-deficient mice displayed increased trabecular bone mass, which was associated with enhanced osteoclastogenesis and bone resorption, but also with increased bone formation. Most importantly however, none of the skeletal parameters assessed by μCT, histomorphometry and serum analyses were significantly influenced by additional S1P3 deficiency. Taken together, our findings fully support the concept that S1P is a potent osteoanabolic molecule, although S1P3 is not the sole receptor mediating this influence. Since S1P receptors are considered excellent drug targets, it is now required to screen for the impact of other family members on bone formation.

Bone metastases in the era of targeted treatments: insights from molecular biology

Bone metastases remain a common feature of advanced cancers and are associated with significant morbidity and mortality. Recent research has identified promising novel treatment targets to improve current treatment strategies for bone metastatic disease. This review summarizes the well-known and recently discovered molecular biology pathways in bone that govern normal physiological remodeling or drive the pathophysiological changes observed when bone metastases are present. In the rapidly changing world of targeted cancer treatments, it is important to recognize the specific treatment effects induced in bone by these agents and the potential impact on common imaging strategies. The osteoclastic targets (bisphosphonates, LGR4, RANKL, mTOR, MET-VEGFR, cathepsin K, Src, Dock 5) and the osteoblastic targets (Wnt and endothelin) are discussed, and the emerging field of osteo-immunity is introduced as potential future therapeutic target. Finally, a summary is provided of available trial data for agents that target these pathways and that have been assessed in patients. The ultimate goal of research into novel pathways and targets involved in the tumor-bone microenvironment is to tackle one of the great remaining unmet needs in oncology, that is finding a cure for bone metastatic disease.

iTRAQ-based Comparative Serum Proteomic Analysis of Prostate Cancer Patients with or without Bone Metastasis

Background: Once prostate cancer developed bone metastasis, the quality of life and prognosis of patients are seriously affected as no effective treatment is currently available. It is necessary to explore the mechanism of bone metastasis and new therapeutic targets. Purpose: To find out the differentially expressed serum proteins in prostate cancer patients with bone metastasis and analyze the expression of key proteins in prostate cancer tissues, serum and prostate cancer cell lines. So as to provide a basis for revealing the mechanism of bone metastasis and designing new therapeutic targets. Methods: iTRAQ-based proteomics method was used to compare serum differential proteins in prostate cancer patients with and without bone metastasis. Three key proteins (CD59, haptoglobin and tetranectin) which had significant fold changes were selected to validate the results of mass spectrometry. Immunohistochemistry and ELISA were applied to tissues and serum samples from prostate cancer patients, respectively, for validation. Finally, western blot, flow cytometry, and immunocytochemistry were used to analyze the expression of the three differentially expressed proteins in the prostate cancer cell lines PC3, LNCap, and Du145. Results: Thirty-two differentially expressed proteins related to bone metastasis of prostate cancer were identified, of which 11 were up-regulated and 21 were down-regulated. CD59 and haptoglobin were up-regulated in prostate cancer with bone metastasis while tetranectin was down-regulated. Tetranectin showed differential expression in epithelial and stromal cells of prostate cancer and hyperplasia tissues.The expression of CD59 was highest in PC3 and lowest in LNCap, while the expression of haptoglobin and tetranectin was the highest in DU145 and lowest in PC3. Conclusion: Mass spectrometry analysis showed that there were more differentially expressed proteins in the serum of patients with bone metastasis than those without metastasis. It has been verified that CD59, haptoglobin and tetranectin are prostate cancer bone metastasis related proteins.

From latency to overt bone metastasis in breast cancer: potential for treatment and prevention

Bone metastasis is present in a high percentage of breast cancer (BCa) patients with distant disease, especially in those with the estrogen receptor‐positive (ER⁺) subtype. Most cells that escape primary tumors are unable to establish metastatic lesions, which suggests that target organ microenvironments are hostile for tumor cells. This implies that BCa cells must achieve a process of speciation to adapt to the new conditions imposed in the new organ. Bone has unique characteristics that can be exploited by cancer cells: it undergoes constant remodeling and comprises diverse environments (including osteogenic, perivascular, and hematopoietic stem cell niches). This allows colonizing cells to take advantage of numerous adhesion molecules, matrix proteins, and soluble factors that facilitate homing, survival, and, eventually, metastatic outgrowth. However, in most cases, metastatic lesions enter into a latency state that can last months, years, or even decades, before forming a clinically detectable macrometastasis. This dormant state challenges the effectiveness of adjuvant chemotherapy. Detecting which tumors are more prone to metastasize to bone and developing new specific therapies that target bone metastasis represent urgent clinical needs. Here, we review the biological mechanisms of BCa bone metastasis and provide the latest options of treatments and predictive markers that are currently in clinical use or are being tested in clinical assays. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Bone-targeted therapies to reduce skeletal morbidity in prostate cancer

Bone metastases are the main driver of morbidity and mortality in advanced prostate cancer. Targeting the bone microenvironment, a key player in the pathogenesis of bone metastasis, has become one of the mainstays of therapy in men with advanced prostate cancer. This review will evaluate the data supporting the use of bone-targeted therapy, including (1) bisphosphonates such as zoledronic acid, which directly target osteoclasts, (2) denosumab, a receptor activator of nuclear factor-kappa B (RANK) ligand inhibitor, which targets a key component of bone stromal interaction, and (3) radium-223, an alpha-emitting calcium mimetic, which hones to the metabolically active areas of osteoblastic metastasis and induces double-strand breaks in the DNA. Denosumab has shown enhanced delay in skeletal-related events compared to zoledronic acid in patients with metastatic castration-resistant prostate cancer (mCRPC). Data are mixed with regard to pain control as a primary measure of efficacy. New data call into question dosing frequency, with quarterly dosing strategy potentially achieving similar effect compared to monthly dosing for zoledronic acid. In the case of radium-223, there are data for both pain palliation and improved overall survival in mCRPC. Further studies are needed to optimize timing and combination strategies for bone-targeted therapies. Ongoing studies will explore the impact of combining bone-targeted therapy with investigational therapeutic agents such as immunotherapy, for advanced prostate cancer. Future studies should strive to develop biomarkers of response, in order to improve efficacy and cost-effectiveness of these agents.

Low-dose cadmium exposure acts on rat mesenchymal stem cells via RANKL/OPG and downregulate osteogenic differentiation genes

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 till date. This study aimed to assess the association between rat mesenchymal stem cells (MSCs) and long-term Cd exposure through 38-week intake of CdCl₂ at 1 and 2 mg/kg body weight (bw). Increased gene expression of receptor activator of NF-κB ligand (RANKL) and decreased gene expression of osteoprotegerin (OPG) were observed. Fold change of RANKL gene expression (fold change = 1.97) and OPG gene expression (fold change = 1.72) showed statistically significant differences at dose 2 mg/kg bw. Decreased expression of key genes was observed during the early osteogenic differentiation of MSCs. The gene expression of Osterix in 1 mg/kg bw group was decreased by 3.70-fold, and the gene expressions of Osterix, Osteopontin, collagen type I alpha 2 chain (COL1a2) and runt-related transcription factor 2 (RUNX2) in 2 mg/kg bw group were decreased by 1.79, 1.67, 1.45 and 1.35-folds, respectively. Exposure to CdCl₂ induced an increase in the renal Cd load, but only an adaptive response was observed, including increased expression of autophagy-related proteins LC3B and Beclin-1, autophagy receptor p62, and heme oxygenase 1 (HO-1), which is an inducible isoform that releases in response to stress. There were no significant changes in the urinary low molecular weight proteins including N-acetyl-b-D-glucosaminidase (NAG), β₂-microglobulin and albumin (U-Alb). Urinary calcium (Ca) excretion showed no increase, and no obvious renal histological changes. Taken together, these results indicated that the chronic CdCl₂ exposure directly act on MSCs through RANKL/OPG pathway and downregulate the key genes involved in osteogenic differentiation of MSCs. The toxic effect of Cd on bone may occur in parallel to nephrotoxicity.

RANKL inhibition improves muscle strength and insulin sensitivity and restores bone mass

Receptor activator of Nfkb ligand (RANKL) activates, while osteoprotegerin (OPG) inhibits, osteoclastogenesis. In turn a neutralizing Ab against RANKL, denosumab improves bone strength in osteoporosis. OPG also improves muscle strength in mouse models of Duchenne's muscular dystrophy (mdx) and denervation-induce atrophy, but its role and mechanisms of action on muscle weakness in other conditions remains to be investigated. We investigated the effects of RANKL inhibitors on muscle in osteoporotic women and mice that either overexpress RANKL (HuRANKL-Tg+), or lack Pparb and concomitantly develop sarcopenia (Pparb-/-). In women, denosumab over 3 years improved appendicular lean mass and handgrip strength compared to no treatment, whereas bisphosphonate did not. HuRANKL-Tg+ mice displayed lower limb force and maximal speed, while their leg muscle mass was diminished, with a lower number of type I and II fibers. Both OPG and denosumab increased limb force proportionally to the increase in muscle mass. They markedly improved muscle insulin sensitivity and glucose uptake, and decrease anti-myogenic and inflammatory gene expression in muscle, such as myostatin and protein tyrosine phosphatase receptor-γ. Similarly, in Pparb-/-, OPG increased muscle volume and force, while also normalizing their insulin signaling and higher expression of inflammatory genes in skeletal muscle. In conclusions, RANKL deteriorates, while its inhibitor improves, muscle strength and insulin sensitivity in osteoporotic mice and humans. Hence denosumab could represent a novel therapeutic approach for sarcopenia.

Management of bone health in solid tumours: From bisphosphonates to a monoclonal antibody

Patients with solid tumours are at risk of impaired bone health from metastases and cancer therapy-induced bone loss (CTIBL). We review medical management of bone health in patients with solid tumours over the past 30 years, from first-generation bisphosphonates to the receptor activator of nuclear factor κB ligand (RANKL)-targeted monoclonal antibody, denosumab. In the 1980s, first-generation bisphosphonates were shown to reduce the incidence of skeletal-related events (SREs) in patients with breast cancer. Subsequently, more potent second- and third-generation bisphosphonates were developed, particularly zoledronic acid (ZA). Head-to-head studies showed that ZA was significantly more effective than pamidronate for reducing SREs in patients with breast and castrate-resistant prostate cancer (CRPC), becoming the standard of care for more than a decade. The RANKL inhibitor denosumab was licensed in 2010, and head-to-head studies and integrated analyses confirmed its superiority to ZA for preventing SREs, particularly in breast cancer and CRPC. Bisphosphonates and denosumab have also been investigated for prevention of CTIBL in patients receiving hormonal therapy for breast and prostate cancer, and denosumab is licensed in this indication. Despite advances in management of bone health, several issues remain, notably the optimal time to initiate therapy, duration of therapy, and dosing frequency, and how to avoid toxicity, particularly with long-term treatment. In summary, introduction of ZA and denosumab has protected patients with bone metastasis from serious bone complications and improved their quality of life. Ongoing research will hopefully guide the optimal use of these agents to help maintain bone health in patients with solid tumours.

Treatment with zoledronic acid subsequent to odanacatib prevents bone loss in postmenopausal women with osteoporosis

Treatment with zoledronic acid 5 mg maintained bone turnover markers in the premenopausal range, increased lumbar spine bone mineral density, and maintained hip bone mineral density in women previously treated with odanacatib 50 mg weekly.

INTRODUCTION

The development of odanacatib (ODN), a cathepsin K inhibitor, for treatment of osteoporosis was discontinued due to an increased risk of cardiovascular events. As the treatment is considered reversible, participants from the LOFT trial in Aarhus, Denmark, were offered treatment with zoledronic acid (ZOL).

METHODS

Sixty-seven postmenopausal women were treated with ZOL 5 mg and followed for 12 months. Of these, 39 had received ODN for 7 years and 28 had received placebo for 5 years and ODN for 2 years. Bone turnover markers (BTM) were measured 3, 6, and 12 months after ZOL, and DXA of spine and hip were performed at time of ZOL treatment and after 12 months.

RESULTS

Within the entire study population, BMD at the lumbar spine increased by 2.8 ± 0.9% (mean ± SEM) (p < 0.01) from baseline to month 12. There was no significant change in BMD at the total hip (p = 0.17) or femoral neck (p = 0.39). There was no difference in the changes in BMD from baseline to 12 months between the two groups at any site (p ≥ 0.20 for all). CTX increased by 107 ± 9% (p < 0.001), PINP by 102 ± 16% (p < 0.001), osteocalcin by 32 ± 6% (p = 0.001) and BSAP by 79 ± 37% (p = 0.001) between 3 and 12 months after ZOL. At month 12, BTM were still within the premenopausal reference range. S-25-hydroxyvitamin D increased (p = 0.059), while PTH (p = 0.007) and eGFR (p = 0.014) decreased during the year following ZOL administration.

CONCLUSION

Treatment with ZOL 5 mg maintained BTMs in the premenopausal range and prevented bone loss in women previously treated with ODN.

Comparison of Denosumab and Bisphosphonates in Patients With Osteoporosis: A Meta-Analysis of Randomized Controlled Trials

CONTEXT

It is uncertain which osteoporosis therapy is more effective: bisphosphonates or denosumab.

OBJECTIVE

To determine whether denosumab therapy increases bone mineral density (BMD) and reduces fracture risk more so than bisphosphonates in patients with low BMD or osteoporosis.

METHODS

The PubMed, Embase, and the Cochrane Library databases were searched through November 2018 for head-to-head, randomized, controlled trials comparing denosumab and bisphosphonates among adult patients with low BMD or osteoporosis. Random-effects models were used.

RESULTS

We identified 10 eligible trials including 5361 participants. Denosumab increased BMD more than bisphosphonate at 12 months (mean difference, 1.42%; 95% CI, 0.95% to 1.89%; P < 0.001) at lumbar spine, 1.11% (95% CI, 0.91% to 1.30%; P < 0.001) at total hip, and 1.00% (95% CI, 0.78% to 1.22%; P < 0.001) at femoral neck. At 24 months, the respective increase differences were 1.74% (95% CI, 1.05% to 2.43%; P < 0.001), 1.22% (95% CI, 0.66% to 1.77%; P < 0.001), and 1.19% (95% CI, 0.65% to 1.72%; P < 0.001). There was no difference in fracture end point at 12 months, but denosumab had a lower osteoporotic fracture incidence than alendronate at 24 months (risk ratio, 0.51; 95% CI, 0.27 to 0.97).

CONCLUSION

Denosumab improved BMD significantly more than bisphosphonate treatment at the lumbar spine, total hip, and femoral neck at 12 and 24 months. Only one study demonstrated greater osteoporotic fracture reduction with denosumab treatment. Longitudinal studies with longer follow-up and large sample size are needed to confirm the efficacy difference.

Molecular understanding of pharmacological treatment of osteoporosis

Osteoporosis is a serious health concern, particularly in aged societies. The burden of osteoporosis with its associated morbidity and mortality due to fracture has become a critical socioeconomic problem.

Skeletal integrity is maintained through a balance of bone resorption and bone formation. The bone turnover process, called bone remodelling.

Recently, a number of anti-osteoporosis drugs with excellent anti-osteoporosis and fracture effects have been developed. They are mainly classified into two groups according to their effects on bone remodelling: anti-resorptive agents and anabolic agents.

Cite this article: EFORT Open Rev 2019;4:158-164. DOI: 10.1302/2058-5241.4.180018

RANKL is a therapeutic target of bone destruction in rheumatoid arthritis

Although remarkable advances have been made in the treatment of rheumatoid arthritis (RA), novel therapeutic options with different mechanisms of action and fewer side effects have been expected. Recent studies have demonstrated that bone-resorbing osteoclasts are critically involved in the bone destruction associated with RA. Denosumab, a human antibody against receptor activator of nuclear factor-kappa B ligand (RANKL), efficiently suppressed the progression of bone erosion in patients with RA by suppressing osteoclast differentiation and activation in several clinical studies, although it had no effect on inflammation or cartilage destruction. Denosumab, in combination with anti-rheumatic drugs, is considered a pivotal therapeutic option for the prevention of bone destruction in RA.

Severe, Symptomatic Hypocalcemia due to Denosumab Administration: Treatment and Clinical Course

Denosumab is a receptor activator of nuclear factor kappa-B (RANK) ligand inhibitor used in the treatment of osteoporosis. Blockade of RANK ligand prevents osteoclastic resorption of bone, but in doing so impairs the parathyroid hormone (PTH)-driven maintenance of serum calcium. A subsequent elevation of PTH remains active at sites other than bone, potentially lowering serum phosphate by inhibiting proximal tubular reabsorption. We present 2 patients who developed severe, symptomatic hypocalcemia after administration of denosumab. These patients provide an opportunity to describe the clinical course and treatment, including the need to consider a continuous calcium infusion, of severe, symptomatic hypocalcemia caused by denosumab.

Genistein and Silicon Synergistically Protects Against Ovariectomy-Induced Bone Loss Through Upregulating OPG/RANKL Ratio

We have reported that genistein (Gen) and silicon (Si) have synergistic effects on ovariectomy-induced bone loss in rat; however, the potential mechanisms behind this effect were not fully clarified yet. This study was performed to evaluate the bone protective mechanisms of concomitant intake of genistein and silicon in ovariectomized rat by OPG/RANKL axis. Three-month-old Sprague-Dawley female rats were subjected to ovariectomy (OVX) or sham surgery; after surgery, the OVX rats were randomly divided into five groups: OVX-Gen, OVX-Si, OVX-Gen-Si, OVX-E, and OVX. Genistein, silicon, and 17β-estradiol supplementation were started after ovariectomy and continued for 10 weeks. The results showed that genistein and silicon treatment increased the bone mineral density (BMD) of ovariectomized rats. In addition, the BMD of the tibia and femur were highest in the OVX-Gen-Si group compared with OVX-Gen and OVX-Si group (p < 0.05). After 10 weeks treatment with genistein and silicon, the bone structure of ovariectomized rats was recovered, there was no difference of bone histomorphometric parameters between OVX-Gen-Si, OVX-E, and SHAM group (p > 0.05), and there was no difference in the concentration of serum ALP, Ca, P, OPG, and RANKL between OVX-Gen-Si, SHAM, and OVX-E groups (p > 0.05). RT-PCR showed that genistein and silicon treatment could effectively increase the OPG mRNA expression and decreased the RANKL mRNA expression compared to that of the OVX group (p < 0.05), the OPG/RANKL mRNA ratios were significantly decreased in the OVX group (p < 0.05), and it was nearly to normal in the OVX-Gen-Si group. Immunohistochemical staining results showed that genistein and silicon supplementation could effectively increase the protein expression of OPG and decrease the protein expression of RANKL in bone tissues; there were no significant differences in OPG and RANKL positive expression areas between OVX-Gen-Si, SHAM, and OVX-E group (p > 0.05). The results above indicate that genistein and silicon supplementation can effectively reduce RANKL, increase OPG levels, and OPG/RANKL ratios in the serum and bone tissue of ovariectomized rats; this is the main mechanism by which genistein and silicon play a bone protective role in ovariectomized rats.

The RANKL-RANK Axis: A Bone to Thymus Round Trip

The identification of Receptor activator of nuclear factor kappa B ligand (RANKL) and its cognate receptor Receptor activator of nuclear factor kappa B (RANK) during a search for novel tumor necrosis factor receptor (TNFR) superfamily members has dramatically changed the scenario of bone biology by providing the functional and biochemical proof that RANKL signaling via RANK is the master factor for osteoclastogenesis. In parallel, two independent studies reported the identification of mouse RANKL on activated T cells and of a ligand for osteoprotegerin on a murine bone marrow-derived stromal cell line. After these seminal findings, accumulating data indicated RANKL and RANK not only as essential players for the development and activation of osteoclasts, but also for the correct differentiation of medullary thymic epithelial cells (mTECs) that act as mediators of the central tolerance process by which self-reactive T cells are eliminated while regulatory T cells are generated. In light of the RANKL-RANK multi-task function, an antibody targeting this pathway, denosumab, is now commonly used in the therapy of bone loss diseases including chronic inflammatory bone disorders and osteolytic bone metastases; furthermore, preclinical data support the therapeutic application of denosumab in the framework of a broader spectrum of tumors. Here, we discuss advances in cellular and molecular mechanisms elicited by RANKL-RANK pathway in the bone and thymus, and the extent to which its inhibition or augmentation can be translated in the clinical arena.

Murine osteoclasts secrete serine protease HtrA1 capable of degrading osteoprotegerin in the bone microenvironment

Osteoclasts are multinucleated cells responsible for bone resorption. The differentiation of osteoclasts from bone marrow macrophages (BMMs) is induced by receptor activator of NF-κB ligand (RANKL). Osteoprotegerin (OPG), a decoy receptor of RANKL, inhibits osteoclastogenesis by blocking RANKL signaling. Here we investigated the degradation of OPG in vitro. Osteoclasts, but not BMMs, secreted OPG-degrading enzymes. Using mass spectrometry and RNA-sequencing analysis, we identified high-temperature requirement A serine peptidase 1 (HtrA1) as an OPG-degrading enzyme. HtrA1 did not degrade OPG pre-reduced by dithiothreitol, suggesting that HtrA1 recognizes the three-dimensional structure of OPG. HtrA1 initially cleaved the amide bond between leucine 90 and glutamine 91 of OPG, then degraded OPG into small fragments. Inhibitory activity of OPG on RANKL-induced osteoclastogenesis was suppressed by adding HtrA1 in RAW 264.7 cell cultures. These results suggest that osteoclasts potentially prepare a microenvironment suitable for osteoclastogenesis. HtrA1 may be a novel drug target for osteoporosis.

Potential association with early changes in serum calcium level after starting or switching to denosumab combined with eldecalcitol

The aims of this study are to investigate changes in serum calcium (Ca) level after switching from either non-therapy, bisphosphonate, selective estrogen receptor modulators (SERM) or teriparatide treatments to a combination therapy of denosumab (DMAb), and eldecalcitol, and the association between early changes in serum calcium and changes in bone metabolic markers and bone mineral density (BMD). 129 patients with postmenopausal osteoporosis (32 non-pretreatment, 50 bisphosphonates, 18 SERM, and 29 teriparatide) were recruited and switched to DMAb plus eldecalcitol. Serum calcium levels, bone metabolism markers, and BMD measurements of the lumbar spine and femoral neck were evaluated. All groups showed an increase in BMD 6 months and 1 year after DMAb administration compared to baseline via suppression of bone metabolism markers. The TPD group showed a significant decrease in serum calcium level 1 week after the first injection of DMAb and eldecalcitol compared to baseline and the bisphosphonate group. Changes in serum calcium level from baseline to 1 week after the first injection of DMAb trended to correlate with changes in bone metabolism markers and lumbar BMD. The risks of DMAb-induced hypocalcemia are different between starting and switching from bone resorption inhibitors and bone formation promoters. Therefore, appropriate assessment before administration of DMAb, including pretreatment therapy as well as serum Ca and bone metabolic markers will help identify the risk of hypocalcemia following DMAb in combination with eldecalcitol. Our findings also showed that early change in serum Ca level after DMAb initiation could potentially predict the efficacy for therapy reaction.

Immobilization of Denosumab on Titanium Affects Osteoclastogenesis of Human Peripheral Blood Monocytes

Immobilization of proteins has been examined to improve implant surfaces. In this study, titanium surfaces were modified with nanofunctionalized denosumab (cDMAB), a human monoclonal anti-RANKL IgG. Noncoding DNA oligonucleotides (ODN) served as linker molecules between titanium and DMAB. Binding and release experiments demonstrated a high binding capacity of cDMAB and continuous release. Human peripheral mononuclear blood cells (PBMCs) were cultured in the presence of RANKL/MCSF for 28 days and differentiated into osteoclasts. Adding soluble DMAB to the medium inhibited osteoclast differentiation. On nanofunctionalized titanium specimens, the osteoclast-specific TRAP5b protein was monitored and showed a significantly decreased amount on cDMAB-titanium in PBMCs + RANKL/MCSF. PBMCs on cDMAB-titanium also changed SEM cell morphology. In conclusion, the results indicate that cDMAB reduces osteoclast formation and has the potential to reduce osteoclastogenesis on titanium surfaces.

Adjuvant denosumab in postmenopausal patients with hormone receptor-positive breast cancer (ABCSG-18): disease-free survival results from a randomised, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

In postmenopausal women with hormone receptor-positive, early-stage breast cancer, treatment with adjuvant aromatase inhibitors is the standard of care, but it increases risk for osteoporosis and fractures. Results from the ABCSG-18 trial showed that use of denosumab as an adjuvant to aromatase inhibitor therapy significantly reduced clinical fractures. Disease-free survival outcomes from ABCSG-18 have not yet been reported.

METHODS

Postmenopausal patients with early, hormone receptor-positive, non-metastatic adenocarcinoma of the breast, who had completed their initial adjuvant treatment pathway (surgery, radiotherapy, or chemotherapy, or a combination) and were receiving adjuvant aromatase inhibitors, were enrolled at 58 trial centres in Austria and Sweden into this prospective, double-blind, placebo-controlled, phase 3 trial. With permuted block randomisation (block sizes 2 and 4, stratified by previous aromatase inhibitor use, total lumbar spine bone mineral density score at baseline, and type of centre), patients were assigned (1:1) to receive subcutaneous denosumab (60 mg) or matching placebo every 6 months during aromatase inhibitor therapy. The primary endpoint (previously reported) was the time to first clinical fracture after randomisation. The secondary endpoint reported here is disease-free survival (defined as time from randomisation to first evidence of local or distant metastasis, contralateral breast cancer, secondary carcinoma, or death from any cause) in the intention-to-treat population. This study is registered with EudraCT (number 2005-005275-15) and ClinicalTrials.gov (number NCT00556374), and is ongoing for long-term follow-up.

FINDINGS

Between Dec 18, 2006, and July 22, 2013, 3425 eligible patients were enrolled and randomly assigned; 1711 to the denosumab group and 1709 to the placebo group (with five others withdrawing consent). After a median follow-up of 73 months (IQR 58-95), 240 (14·0%) patients in the denosumab and 287 (16·8%) in the placebo group had disease-free survival events. Disease-free survival was significantly improved in the denosumab group versus the placebo group (hazard ratio 0·82, 95% CI 0·69-0·98, Cox p=0·0260; descriptive analysis, without controlling for multiplicity). In the denosumab group, disease-free survival was 89·2% (95% CI 87·6-90·8) at 5 years and 80·6% (78·1-83·1) at 8 years of follow-up, compared with 87·3% (85·7-89·0) at 5 years and 77·5% (74·8-80·2) and 8 years in the placebo group. No independently adjudicated cases of osteonecrosis of the jaw or confirmed atypical femoral fractures were recorded. The total number of adverse events was similar in the denosumab group (1367 [including 521 serious] adverse events) and the placebo group (1339 [515 serious]). The most common serious adverse events were osteoarthritis (62 [3·6%] of 1709 in the denosumab group vs 58 [3·4%] of 1690 in the placebo group), meniscus injury (23 [1·3%] vs 24 [1·4%]), and cataract (16 [0·9%] vs 28 [1·7%]). One (<0·1%) treatment-related death (due to pneumonia, septic kidney failure, and cardiac decompensation) occurred in the denosumab group.

INTERPRETATION

Denosumab constitutes an effective and safe adjuvant treatment for patients with postmenopausal hormone receptor-positive early breast cancer receiving aromatase inhibitor therapy.

FUNDING

Amgen.

ERRα promotes breast cancer cell dissemination to bone by increasing RANK expression in primary breast tumors

Bone is the most common metastatic site for breast cancer. Estrogen-related-receptor alpha (ERRα) has been implicated in cancer cell invasiveness. Here, we established that ERRα promotes spontaneous metastatic dissemination of breast cancer cells from primary mammary tumors to the skeleton. We carried out cohort studies, pharmacological inhibition, gain-of-function analyses in vivo and cellular and molecular studies in vitro to identify new biomarkers in breast cancer metastases. Meta-analysis of human primary breast tumors revealed that high ERRα expression levels were associated with bone but not lung metastases. ERRα expression was also detected in circulating tumor cells from metastatic breast cancer patients. ERRα overexpression in murine 4T1 breast cancer cells promoted spontaneous bone micro-metastases formation when tumor cells were inoculated orthotopically, whereas lung metastases occurred irrespective of ERRα expression level. In vivo, Rank was identified as a target for ERRα. That was confirmed in vitro in Rankl stimulated tumor cell invasion, in mTOR/pS6K phosphorylation, by transactivation assay, ChIP and bioinformatics analyses. Moreover, pharmacological inhibition of ERRα reduced primary tumor growth, bone micro-metastases formation and Rank expression in vitro and in vivo. Transcriptomic studies and meta-analysis confirmed a positive association between metastases and ERRα/RANK in breast cancer patients and also revealed a positive correlation between ERRα and BRCA1mut carriers. Taken together, our results reveal a novel ERRα/RANK axis by which ERRα in primary breast cancer promotes early dissemination of cancer cells to bone. These findings suggest that ERRα may be a useful therapeutic target to prevent bone metastases.

Immune checkpoint inhibitor (anti-CTLA-4, anti-PD-1) therapy alone versus immune checkpoint inhibitor (anti-CTLA-4, anti-PD-1) therapy in combination with anti-RANKL denosumuab in malignant melanoma: a retrospective analysis at a tertiary care center

Denosumab is a monoclonal antibody against RANK ligand with a role in the prevention of skeletal-related events and is also known to possess antitumor properties. In this retrospective review, we aim to evaluate the synergist effect of a combination therapy with immune checkpoint inhibitors and denosumab in malignant melanoma patients. Patients of 18 years of age or older with a diagnosis of malignant melanoma who have received immune checkpoint inhibitors and denosumab between June 2015 and May 2017 were divided into two cohorts: cohort A (immune checkpoint inhibitors only) and cohort B (immune checkpoint inhibitors and denosumab). Overall survival, progression-free survival, objective response rate, and safety analysis were performed. Stratified analysis based on metastatic (M) status was performed as well. Eleven (29.72%) out of 37 patients received immune checkpoint inhibitors and denosumab combination. Median overall survival in cohort B was 57 months compared with 22.8 months in cohort A and 22 months in M1c patients from cohort A. Median progression-free survival was 4.15 months in cohort B compared with 11.6 months in cohort A and 5.12 months in M1c patients from cohort A. The mean number of distant sites involved in metastasis were significantly higher in cohort B (3.54 vs. 2.23, P=0.0015). Cohort B also had more patients with more than two distant metastatic sites (90.9 vs. 30.8%, P=0.001). A combination therapy with denosumab and immune checkpoint inhibitors may have a beneficial effect on survival and progression as in our study; the patients receiving combination therapy did not behave poorly despite having poor prognostic features.

RANKL/RANK/OPG system beyond bone remodeling: involvement in breast cancer and clinical perspectives

RANKL/RANK/OPG system consists of three essential signaling molecules: i) the receptor activator of nuclear factor (NF)-kB-ligand (RANKL), ii) the receptor activator of NF-kB (RANK), and iii) the soluble decoy receptor osteoprotegerin (OPG). Although this system is critical for the regulation of osteoclast differentiation/activation and calcium release from the skeleton, different studies have elucidated its specific role in mammary gland physiology and hormone-driven epithelial proliferation during pregnancy. Of note, several data suggest that progesterone induces mammary RANKL expression in mice and humans. In turn, RANKL controls cell proliferation in breast epithelium under physiological conditions typically associated with higher serum progesterone levels, such as luteal phase of the menstrual cycle and pregnancy. Hence, RANKL/RANK system can be regarded as a major downstream mediator of progesterone-driven mammary epithelial cells proliferation, potentially contributing to breast cancer initiation and progression. Expression of RANKL, RANK, and OPG has been detected in breast cancer cell lines and in human primary breast cancers. To date, dysregulation of RANKL/RANK/OPG system at the skeletal level has been widely documented in the context of metastatic bone disease. In fact, RANKL inhibition through the RANKL-blocking human monoclonal antibody denosumab represents a well-established therapeutic option to prevent skeletal-related events in metastatic bone disease and adjuvant therapy-induced bone loss in breast cancer. On the other hand, the exact role of OPG in breast tumorigenesis is still unclear. This review focuses on molecular mechanisms linking RANKL/RANK/OPG system to mammary tumorigenesis, highlighting pre-clinical and clinical evidence for the potential efficacy of RANKL inhibition as a prevention strategy and adjuvant therapy in breast cancer settings.

Suppression of hematopoietic cell kinase ameliorates the bone destruction associated with inflammation

Objectives: To investigate the role of non-receptor tyrosine kinases (NRTKs) in inflammation-induced osteoclastogenesis.Methods: Microarray analyses of global mRNA expression during receptor activator of NF-κB ligand (RANKL) and RANKL plus tumor necrosis factor (TNF)-α-induced osteoclast differentiation were performed. The inhibitory effect on TNF-α-induced osteoclast differentiation of A-419259, a potent inhibitor of hematopoietic cell kinase (Hck), was examined. The in vivo therapeutic effect of A-419259 treatment on lipopolysaccharide (LPS)-induced inflammatory bone destruction was evaluated.Results: We confirmed that Hck expression was selectively increased among the NRTKs during the osteoclast differentiation induced by RANKL and TNF-α, but not by RANKL alone. RANKL and TNF-α-induced osteoclast differentiation and they were dose-dependently inhibited by A-419259 treatment through inhibition of the expression of key regulators of osteoclastogenesis, including Prdm1 and Nfatc1. Notably, LPS-induced inflammatory bone loss in murine calvarial bones was ameliorated by the administration of A-419259.Conclusions: Our results demonstrate that the administration of A-419259 is effective for the inhibition of osteoclast differentiation induced by TNF-α in the presence of RANKL. Therefore, an inhibitor of Hck may be useful as a potent anti-osteoclastogenic agent for the treatment of inflammatory bone destruction.

The Cells of Bone and Their Interactions

Bone tissue is comprised of a collagen-rich matrix containing non-collagenous organic compounds, strengthened by mineral crystals. Bone strength reflects the amount and structure of bone, as well as its quality. These qualities are determined and maintained by osteoblasts (bone-forming cells) and osteoclasts (bone-resorbing cells) on the surface of the bone and osteocytes embedded within the bone matrix. Bone development and growth also involves cartilage cells (chondrocytes). These cells do not act in isolation, but function in a coordinated manner, including co-ordination within each lineage, between the cells of bone, and between these cells and other cell types within the bone microenvironment. This chapter will briefly outline the cells of bone, their major functions, and some communication pathways responsible for controlling bone development and remodeling.

The TNF Family of Ligands and Receptors: Communication Modules in the Immune System and Beyond

The tumor necrosis factor (TNF) and TNF receptor (TNFR) superfamilies (TNFSF/TNFRSF) include 19 ligands and 29 receptors that play important roles in the modulation of cellular functions. The communication pathways mediated by TNFSF/TNFRSF are essential for numerous developmental, homeostatic, and stimulus-responsive processes in vivo. TNFSF/TNFRSF members regulate cellular differentiation, survival, and programmed death, but their most critical functions pertain to the immune system. Both innate and adaptive immune cells are controlled by TNFSF/TNFRSF members in a manner that is crucial for the coordination of various mechanisms driving either co-stimulation or co-inhibition of the immune response. Dysregulation of these same signaling pathways has been implicated in inflammatory and autoimmune diseases, highlighting the importance of their tight regulation. Investigation of the control of TNFSF/TNFRSF activities has led to the development of therapeutics with the potential to reduce chronic inflammation or promote anti-tumor immunity. The study of TNFSF/TNFRSF proteins has exploded over the last 30 yr, but there remains a need to better understand the fundamental mechanisms underlying the molecular pathways they mediate to design more effective anti-inflammatory and anti-cancer therapies.

Bone management in hematologic stem cell transplant recipients

Autologous and allogeneic hematopoietic stem cell transplantation (HSCT) is the treatment of choice for patients with some malignant and non-malignant hematological diseases. Advances in transplantation techniques and supportive care measures have substantially increased the number of long-term HSCT survivors. This has led to an increasing patient population suffering from the late effects of HSCT, of which, bone loss and its consequent fragility fractures lead to substantial morbidity. Altered bone health, with consequent fragility fractures, and chronic graft-versus-host disease (GVHD) are factors affecting long-term quality of life after HSCT. Hypogonadism, HSCT preparative regimens, nutritional factors, and glucocorticoids all contribute to accelerated bone loss and increased fracture risk. Management strategies should include bone mineral density examination, evaluation of clinical risk factors, and general dietary and physical activity measures. Evidence has accumulated permitting recommendations for more attentiveness to evaluation and monitoring of bone health, with appropriate application of osteoporosis pharmacotherapies to patients at increased risk of bone loss and fracture.