Evidence for a role of a tumor necrosis factor-alpha (TNF-alpha)-converting enzyme-like protease in shedding of TRANCE, a TNF family member involved in osteoclastogenesis and dendritic cell survival

Biologic Antiresorptive: Denosumab

Background

Osteoporosis is an age-related common bone disorder characterized by low bone mineral density and increased fragility fracture risk. Various Antiresorptive medications are being used to target osteoclast mediated bone resorption to prevent bone loss and reduce fracture risk.

About Denosumab

Denosumab is a novel biological antiresorptive drug that belongs to the class of monoclonal antibodies. It binds to and inhibits the cytokine receptor activator of nuclear factor kappa-B ligand (RANKL), which is requisite for osteoclast differentiation, function and survival.

Effectiveness

Denosumab has been shown to be a potent and effective therapy for osteoporosis, with clinical trial data demonstrating significant improvement in bone mineral density (BMD) and reductions in fracture risk at various skeletal sites for more than 10 years of treatment.

Safety Profile

Denosumab has a favourable benefit/risk profile, with low rates of complications such as infection, atypical femoral fracture and osteonecrosis of the jawbone.

Challenges

However, denosumab treatment requires continuous administration, as discontinuation leads to rapid bone mineral loss and increased risk of multiple vertebral fractures due to rebound of bone turnover. Therefore, modification to another anti-osteoporosis drug therapy after denosumab discontinuation is required to maintain bone health.

Conclusion

Denosumab is a promising biological antiresorptive therapy for osteoporosis that offers high efficacy and safety, but also poses challenges for long-term management.

ADAM10 and ADAM17, Major Regulators of Chronic Kidney Disease Induced Atherosclerosis?

Chronic kidney disease (CKD) is a major health problem, affecting millions of people worldwide, in particular hypertensive and diabetic patients. CKD patients suffer from significantly increased cardiovascular disease (CVD) morbidity and mortality, mainly due to accelerated atherosclerosis development. Indeed, CKD not only affects the kidneys, in which injury and maladaptive repair processes lead to local inflammation and fibrosis, but also causes systemic inflammation and altered mineral bone metabolism leading to vascular dysfunction, calcification, and thus, accelerated atherosclerosis. Although CKD and CVD individually have been extensively studied, relatively little research has studied the link between both diseases. This narrative review focuses on the role of a disintegrin and metalloproteases (ADAM) 10 and ADAM17 in CKD and CVD and will for the first time shed light on their role in CKD-induced CVD. By cleaving cell surface molecules, these enzymes regulate not only cellular sensitivity to their micro-environment (in case of receptor cleavage), but also release soluble ectodomains that can exert agonistic or antagonistic functions, both locally and systemically. Although the cell-specific roles of ADAM10 and ADAM17 in CVD, and to a lesser extent in CKD, have been explored, their impact on CKD-induced CVD is likely, yet remains to be elucidated.

Targeting 4-1BB for tumor immunotherapy from bench to bedside

Immune dysfunction has been proposed as a factor that may contribute to disease progression. Emerging evidence suggests that immunotherapy aims to abolish cancer progression by modulating the balance of the tumor microenvironment. 4-1BB (also known as CD137 and TNFRS9), a member of tumor necrosis factor receptor superfamily, has been validated as an extremely attractive and promising target for immunotherapy due to the upregulated expression in the tumor environment and its involvement in tumor progression. More importantly, 4-1BB-based immunotherapy approaches have manifested powerful antitumor effects in clinical trials targeting 4-1BB alone or in combination with other immune checkpoints. In this review, we will summarize the structure and expression of 4-1BB and its ligand, discuss the role of 4-1BB in the microenvironment and tumor progression, and update the development of drugs targeting 4-1BB. The purpose of the review is to furnish a comprehensive overview of the potential of 4-1BB as an immunotherapeutic target and to discuss recent advances and prospects for 4-1BB in cancer therapy.

Human mast cells induce osteoclastogenesis through cell surface RANKL

OBJECTIVES

We employed the co-culture of CD34⁺ stem cell-derived human mast cells (HMC) and human monocyte-derived osteoclast precursors to evaluate if mast cells contribute to the pathogenesis of osteoporosis through regulation of osteoclast proliferation and activation.

METHODS

Mature HMC and osteoclast precursors were cultured from monocytes isolated from human buffy coat. The osteoclast precursors were incubated with HMC or receptor activator of nuclear factor kappa-B ligand (RANKL) for a week prior to determination of osteoclast maturation through characterization by their morphology and tartrate resistant acid phosphatase (TRAP) expression. The bone absorption activity was determined by pit formation on osteo-assay plate.

RESULTS

Mature osteoclasts were identified following co-culture of osteoclast precursors with HMC for one week in the absence of RANKL and they were capable of bone resorption. These actions of HMC on osteoclasts were not affected by mast cell activators such anti-IgE or substance P but could be reversed by osteoprotegerin (OPG) in the co-culture system suggesting the involvement of RANKL. The expression of RANKL on the cell surface of HMC was confirmed by flow cytometry and the density was not affected by activation of HMC.

CONCLUSION

Our study provided direct evidence confirming the initiation of osteoclast proliferation and activation by mast cells through cell surface RANKL suggesting that mast cells may contribute to bone destruction in pathological conditions such as osteoporosis.

RANKL regulates testicular cancer growth and Denosumab treatment has suppressive effects on GCNIS and advanced seminoma

BACKGROUND

Testicular germ cell tumours (TGCTs) have a high sensitivity to chemotherapy and a high cure rate, although with serious adverse effects. In the search for tumour suppressive drugs, the RANKL inhibitor Denosumab, used to treat osteoporosis, came up as a candidate since RANKL signalling was recently identified in the testis.

METHODS

Expression of RANKL, RANK and OPG, and the effects of RANKL inhibition were investigated in human TGCTs, TGCT-derived cell-lines, and TGCT-xenograft models. Serum RANKL was measured in TGCT-patients.

RESULTS

RANKL, RANK, and OPG were expressed in germ cell neoplasia in situ (GCNIS), TGCTs, and TGCT-derived cell lines. RANKL-inhibition reduced proliferation of seminoma-derived TCam-2 cells, but had no effect on embryonal carcinoma-derived NTera2 cells. Pretreatment with Denosumab did not augment the effect of cisplatin in vitro. However, inhibition of RANKL in vivo reduced tumour growth exclusively in the TCam-2-xenograft model and Denosumab-treatment decreased proliferation in human GCNIS cultures. In TGCT-patients serum RANKL had no prognostic value.

CONCLUSIONS

This study shows that the RANKL signalling system is expressed in GCNIS and seminoma where RANKL inhibition suppresses tumour growth in vitro and in vivo. Future studies are needed to determine whether RANKL is important for the malignant transformation or transition from GCNIS to invasive tumours.

Clinical and Biochemical Effects of Smoking on Non-Surgical Periodontal Treatment in Grade III Stage C Periodontitis Patients

Objective: The purpose of this study was to evaluate the effect of smoking on clinical parameters and the serum and saliva levels of RANKL, OPG, and IL-34 in periodontitis stage III grade C (III-C) patients after non-surgical periodontal treatment (NSPT). Methods: A total of 60 subjects, 40 periodontitis-III-C patients (20 smokers and 20 non-smokers) and 20 non-smoker periodontally healthy individuals, were included. All clinical periodontal parameters were recorded, and unstimulated saliva and serum samples were collected from all patients at baseline, but at 1 and 3 months only from periodontitis patients (N=40). Saliva and serum levels of RANKL, OPG, and IL-34 were analyzed by ELISA. Results: At baseline only whole mouth probing depth (PD) and percent of sites with PD>5mm were higher in smokers than non-smoker periodontitis patients (p

Onc201 reduces osteoclastogenesis and prevents ovariectomy-induced bone loss via inhibiting RANKL-induced NFATc1 activation and the integrin signaling pathway

Osteoporosis is an osteolytic disease with a disrupted balance between the resorption and formation of bone as well as bone microstructure degeneration, leading to bone loss and increased fracture risk, which greatly affects patients' quality of life. Currently, inhibition of osteoclast bone resorption remains the mainstream treatment for osteoporosis. Onc201, a new compound, induces the gene expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and has an efficient anticancer effect in clinical trials. However, its effects on osteolytic disease and the mechanism of action are unclear. We examined the effect of Onc201 on nuclear factor κB ligand-receptor activator (RANKL)-induced osteoclasts via Cell Counting Kit-8, bone resorption assay, luciferase reporter assay, immunofluorescence staining, calcium ion intensity assay and employed an ovariectomy model to investigate the effect of Onc201 on osteoporosis in the mice. Results showed that Onc201 inhibited the function and formation of osteoclasts induced by RANKL in a manner that was dependent on time and concentration, and did not cause cytotoxicity. Mechanistically, Onc201 inhibited osteoclast-relevant genes and NFATc1 expression, the main transcriptional regulatory factor of the formation of osteoclasts induced by RANKL; meanwhile, downregulating the expressions of the osteoclast cytoskeleton key signal molecules integrin αvβ3, focal adhesion kinase (FAK), c-Src, and spleen-associated tyrosine kinase (SYK). In addition, Onc201 had a protective effect on the mouse model of bone loss caused by ovariectomy-induced estrogen deficiency, which is consistent with the in vitro results. Our findings suggest that the new small-molecular compound Onc201 has the potential to prevent osteoclast-related osteolytic diseases.

Receptor Activator of NF-κB (RANK) Confers Resistance to Chemotherapy in AML and Associates with Dismal Disease Course

Simple Summary

Acute myeloid leukemia (AML) is the most common form of acute leukemia in adults. Despite the emergence of new therapeutic agents in recent years, curation remains challenging, and new and better treatment options are needed. In the present study, we investigated the expression, prognostic significance, and functional role of the Receptor Activator of Nuclear Factor-κB (RANK) in AML. We found that RANK is expressed on leukemic cells in a substantial proportion of AML patients and is associated with a dismal disease course. We further demonstrated that signaling via RANK induces release of factors that favor AML cell survival and confers resistance to chemotherapeutics in AML treatment. Together, our findings identify RANK as novel prognostic marker and putative candidate for therapeutic intervention in AML to enhance response to treatment.

Abstract

Although treatment options of acute myeloid leukemia (AML) have improved over the recent years, prognosis remains poor. Better understanding of the molecular mechanisms influencing and predicting treatment efficacy may improve disease control and outcome. Here we studied the expression, prognostic relevance and functional role of the tumor necrosis factor receptor (TNFR) family member Receptor Activator of Nuclear Factor (NF)-κB (RANK) in AML. We conducted an experimental ex vivo study using leukemic cells of 54 AML patients. Substantial surface expression of RANK was detected on primary AML cells in 35% of the analyzed patients. We further found that RANK signaling induced the release of cytokines acting as growth and survival factors for the leukemic cells and mediated resistance of AML cells to treatment with doxorubicin and cytarabine, the most commonly used cytostatic compounds in AML treatment. In line, RANK expression correlated with a dismal disease course as revealed by reduced overall survival. Together, our results show that RANK plays a yet unrecognized role in AML pathophysiology and resistance to treatment, and identify RANK as “functional” prognostic marker in AML. Therapeutic modulation of RANK holds promise to improve treatment response in AML patients.

Age-related changes and reference intervals of RANKL, OPG, and bone turnover markers in Indian women

RANKL and OPG are cytokines involved in bone remodeling that makes them potential bone biomarkers. The reference interval for these cytokines, their ratio, and bone turnover markers CTX and PINP were established in Indian women, which may serve in diagnosis and management of osteoporosis.

PURPOSE

The aim of the study was to establish reference interval for RANKL, OPG, RANKL/OPG, and bone turnover markers CTX and PINP in healthy Indian women.

METHODS

This was a cross-sectional study on 374 healthy Indian women in the age group of 20-65 years. Serum levels of total RANKL, OPG, CTX, PINP, and estradiol were determined by commercial ELISA kits. The reference intervals for these cytokines and bone turnover markers were based on the 95% centrally distributed data.

RESULTS

Median RANKL (245.6 pmol/L vs. 149 pmol/L) and RANKL/OPG (38.7 vs. 20.4) were higher, while sCTX (380 ng/L vs. 551 ng/L) and OPG levels (6.1 pmol/L vs. 7.4 pmol/L) were lower in premenopausal women than those in postmenopausal women. PINP levels were comparable in both groups. Women were classified into 5 groups according to decades of age and the reference intervals for RANKL, OPG, RANKL/OPG ratio, and CTX and PINP in each group were reported.

CONCLUSION

We reported menopausal status-based and age-related reference intervals for serum RANKL, OPG, RANKL/OPG ratio, and CTX and PINP in healthy Indian women.

Myeloma-Bone Interaction: A Vicious Cycle via TAK1-PIM2 Signaling

Simple Summary

Myeloma cells interact with their ambient cells in the bone, such as bone marrow stromal cells, osteoclasts, and osteocytes, resulting in enhancement of osteoclastogenesis and inhibition of osteoblastogenesis while enhancing their growth and drug resistance. The activation of the TAK1–PIM2 signaling axis appears to be vital for this mutual interaction, posing it as an important therapeutic target to suppress tumor expansion and ameliorate bone destruction in multiple myeloma.

Abstract

Multiple myeloma (MM) has a propensity to develop preferentially in bone and form bone-destructive lesions. MM cells enhance osteoclastogenesis and bone resorption through activation of the RANKL–NF-κB signaling pathway while suppressing bone formation by inhibiting osteoblastogenesis from bone marrow stromal cells (BMSCs) by factors elaborated in the bone marrow and bone in MM, including the soluble Wnt inhibitors DKK-1 and sclerostin, activin A, and TGF-β, resulting in systemic bone destruction with loss of bone. Osteocytes have been drawn attention as multifunctional regulators in bone metabolism. MM cells induce apoptosis in osteocytes to trigger the production of factors, including RANKL, sclerostin, and DKK-1, to further exacerbate bone destruction. Bone lesions developed in MM, in turn, provide microenvironments suited for MM cell growth/survival, including niches to foster MM cells and their precursors. Thus, MM cells alter the microenvironments through bone destruction in the bone where they reside, which in turn potentiates tumor growth and survival, thereby generating a vicious loop between tumor progression and bone destruction. The serine/threonine kinases PIM2 and TAK1, an upstream mediator of PIM2, are overexpressed in bone marrow stromal cells and osteoclasts as well in MM cells in bone lesions. Upregulation of the TAK1–PIM2 pathway plays a critical role in tumor expansion and bone destruction, posing the TAK1–PIM2 pathway as a pivotal therapeutic target in MM.

The pathophysiology of immunoporosis: innovative therapeutic targets

BACKGROUND

The physiological balance between bone resorption and bone formation is now known to be mediated by a cascade of events parallel to the classic osteoblast-osteoclast interaction. Thus, osteoimmunology now encompasses the role played by other cell types, such as cytokines, lymphocytes and chemokines, in immunological responses and how they help modulate bone metabolism. All these factors have an impact on the RANK/RANKL/OPG pathway, which is the major pathway for the maturation and resorption activity of osteoclast precursor cells, responsible for osteoporosis development. Recently, immunoporosis has emerged as a new research area in osteoimmunology dedicated to the immune system's role in osteoporosis.

METHODS

The first part of this review presents theoretical concepts on the factors involved in the skeletal system and osteoimmunology. Secondly, existing treatments and novel therapeutic approaches to treat osteoporosis are summarized. These were selected from to the most recent studies published on PubMed containing the term osteoporosis. All data relate to the results of in vitro and in vivo studies on the osteoimmunological system of humans, mice and rats.

FINDINGS

Treatments for osteoporosis can be classified into two categories. They either target osteoclastogenesis inhibition (denosumab, bisphosphonates), or they aim to restore the number and function of osteoblasts (romozumab, abaloparatide). Even novel therapies, such as resolvins, gene therapy, and mesenchymal stem cell transplantation, fall within this classification system.

CONCLUSION

This review presents alternative pathways in the pathophysiology of osteoporosis, along with some recent therapeutic breakthroughs to restore bone homeostasis.

RANKL expression in chondrocytes and its promotion by lymphotoxin-α in the course of cartilage destruction during rheumatoid arthritis

We investigated the expression and localization of the receptor activator nuclear factor κB ligand (RANKL) in cartilage from patients with rheumatoid arthritis (RA) of relevance to cartilage degeneration. We also examined the role of exogenous lymphotoxin (LT)-α on RANKL expression in human chondrocytes and its effect on in vitro osteoclast differentiation. Cartilage and synovial fluid samples were obtained from 45 patients undergoing total joint replacement surgery or joint puncture, including 24 patients with osteoarthritis (OA) and 21 patients with RA. RANKL expression in articular cartilage was examined by immunohistochemistry. LT-α concentrations in synovial fluid were measured using an enzyme-linked immunosorbent assay (ELISA). Normal human chondrocytes were stimulated with LT-α, and the relative mRNA levels of RANKL, osteoprotegerin (OPG), matrix metalloproteinase-9, and vascular endothelial growth factor were examined by real-time polymerase chain reaction. Soluble RANKL protein in culture media was measured using ELISA, and membrane-bound RANKL protein in cells was examined by western blotting. Co-cultures of human chondrocytes with peripheral blood mononuclear cells (PBMCs) were stimulated with macrophage-colony stimulating factor and LT-α, and osteoclast differentiation was evaluated by staining for tartrate-resistant acid phosphatase. LT-α concentrations were higher in RA synovial fluid than in OA samples. The population of RANKL-positive chondrocytes of RA cartilage was higher than that of OA cartilage, and correlated with cartilage degeneration. Stimulation of cultured human chondrocytes by LT-α increased RANKL expression, the RANKL/OPG ratio, and angiogenic factors. Membrane-bound RANKL in chondrocytes was up-regulated after stimulation of LT-α, whereas soluble RANKL in culture medium did not increase. Co-cultures of human chondrocytes and PBMCs demonstrated that LT-α stimulated human chondrocytes to produce RANKL and induced osteoclastic differentiation of PBMCs. RANKL produced by chondrocytes may contribute to cartilage destruction during RA and LT-α could promote the expression of RANKL in human chondrocytes.

The hidden secrets of soluble RANKL in bone biology

The discovery of cytokine tumor necrosis factor (TNF) in the 20th century revealed numerous secrets about organ development. In particular, the functions identified for the receptor activator of nuclear factor kappa-β (NF-κβ) ligand (also known as the RANKL/osteoprotegerin ligand (OPGL) or RANK ligand/TNFSF11) in the homeostasis of skeletal structure, function and regulation were not anticipated. Empirical evidence established the receptor-ligand interaction of RANKL with RANK in osteoclast formation. Reverse signaling of RANKL triggers NF-κβ for the degradation of β-catenin to inhibit bone formation. There is also evidence that RANKL modifies the behavior of other cells in the bone microenvironment, including osteoblasts, chondrocytes, endothelial cells and lymphocytes during normal (homeostatic) and diseased (osteoimmune) states. Two forms of RANKL, i.e., soluble and membrane-bound RANKL, are produced by bone cells. Even though soluble RANKL (sRANKL) and membrane-bound RANKL (mRANKL) both stimulate osteoclast formation in vitro, their biological roles are different. mRANKL triggers osteoclastogenesis by binding to RANK through cell-cell interaction; however, sRANKL released from osteogenic cells binds to RANK without cell-cell interaction. This review attempts to hypothesize how sRANKL functions biologically in bone and explore how this hypothesis might influence future research.

Contribution of ADAM17 and related ADAMs in cardiovascular diseases

A disintegrin and metalloproteases (ADAMs) are key mediators of cell signaling by ectodomain shedding of various growth factors, cytokines, receptors and adhesion molecules at the cellular membrane. ADAMs regulate cell proliferation, cell growth, inflammation, and other regular cellular processes. ADAM17, the most extensively studied ADAM family member, is also known as tumor necrosis factor (TNF)-α converting enzyme (TACE). ADAMs-mediated shedding of cytokines such as TNF-α orchestrates immune system or inflammatory cascades and ADAMs-mediated shedding of growth factors causes cell growth or proliferation by transactivation of the growth factor receptors including epidermal growth factor receptor. Therefore, increased ADAMs-mediated shedding can induce inflammation, tissue remodeling and dysfunction associated with various cardiovascular diseases such as hypertension and atherosclerosis, and ADAMs can be a potential therapeutic target in these diseases. In this review, we focus on the role of ADAMs in cardiovascular pathophysiology and cardiovascular diseases. The main aim of this review is to stimulate new interest in this area by highlighting remarkable evidence.

RANK Signaling in the Differentiation and Regeneration of Thymic Epithelial Cells

Thymic epithelial cells (TECs) provide essential clues for the proliferation, survival, migration, and differentiation of thymocytes. Recent advances in mouse and human have revealed that TECs constitute a highly heterogeneous cell population with distinct functional properties. Importantly, TECs are sensitive to thymic damages engendered by myeloablative conditioning regimen used for bone marrow transplantation. These detrimental effects on TECs delay de novo T-cell production, which can increase the risk of morbidity and mortality in many patients. Alike that TECs guide the development of thymocytes, reciprocally thymocytes control the differentiation and organization of TECs. These bidirectional interactions are referred to as thymic crosstalk. The tumor necrosis factor receptor superfamily (TNFRSF) member, receptor activator of nuclear factor kappa-B (RANK) and its cognate ligand RANKL have emerged as key players of the crosstalk between TECs and thymocytes. RANKL, mainly provided by positively selected CD4⁺ thymocytes and a subset of group 3 innate lymphoid cells, controls mTEC proliferation/differentiation and TEC regeneration. In this review, I discuss recent advances that have unraveled the high heterogeneity of TECs and the implication of the RANK-RANKL signaling axis in TEC differentiation and regeneration. Targeting this cell-signaling pathway opens novel therapeutic perspectives to recover TEC function and T-cell production.

RANK/RANKL/OPG Signaling in the Brain: A Systematic Review of the Literature

Together with its dominant immunological and bone remodeling involvement, RRO axis, comprising of receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) signaling, is as well-implicated in CNS functioning and corresponding pathologies. The CNS aspects of RANKL/RANK/OPG (RRO) axis were systematically reviewed. With search 10 databases, and 7 additional resources from first article publication to July 2019, resulted in total 2,222 hits, from which 33 relevant articles were selected. The elements of RRO axis in CNS include cells involved in neuroinflammation, predominantly in microglia, but as well in resident macrophages and inflammatory cells migrating across the blood-brain barrier. The expression in neurons and oligodendrocytes is mainly confined to processes of differentiation and cell death. RRO axis tunes the neuroinflammatory response, depending on the molecular, cellular and pathological context. RANK/RANKL signaling is neuroprotective in TLR-mediated inflammation, while OPG seems detrimental in stroke, but beneficial in multiple sclerosis. The levels of RRO axis elements can serve as biomarkers in the blood and cerebrospinal fluid. They act as neuroprotectant after brain damage even being implicated in body weight- and thermo-regulation. As derivatives of RRO axis already exist as therapeutic agents in bone remodeling, it would be intriquing to see if these or new RRO-based pharmaceuticals would appear effective in CNS therapies.

Anti-c-fms Antibody Prevents Osteoclast Formation and Bone Resorption in Co-Culture of Osteoblasts and Osteoclast Precursors In Vitro and in Ovariectomized Mice

Osteoporosis morphology is characterized by bone resorption and decreases in micro-architecture parameters. Anti-osteoporosis therapy targets osteoclasts because bone resorption is a unique function of osteoclasts. Anti-c-fms antibodies against the receptor for macrophage colony-stimulating factor (M-CSF) inhibit osteoclast formation and bone resorption in vitro and in vivo. However, the effect of anti-c-fms antibodies on bone resorption in ovariectomized (OVX) mice is unknown. In this study, we evaluated the effect of anti-c-fms antibodies on osteoclast formation and bone resorption in osteoblast-osteoclast precursor co-culture in vitro and in OVX mice. Osteoblast and osteoclast precursor co-cultures treated with anti-c-fms antibodies showed significantly inhibited osteoclast formation, while cultures without anti-c-fms antibody treatment showed osteoclast formation. However, anti-c-fms antibodies did not change the receptor activator of nuclear factor kappa-B ligand (RANKL) or osteoprotegrin (OPG) expression during osteoblast and osteoclast differentiation in vitro. These results indicate that anti-c-fms antibodies directly affected osteoclast formation from osteoclast precursors in co-culture. OVX mice were treated with intraperitoneal injections of anti-c-fms antibody. The trabecular bone structure of the femur was assessed by micro-computer tomography. The anti-c-fms antibody inhibited osteoclast formation and bone loss compared with PBS-treated OVX mice. These results indicate potential for the therapeutic application of anti-c-fms antibodies for postmenopausal osteoporosis.

Glucocorticoids employ the monomeric glucocorticoid receptor to potentiate vitamin D3 and parathyroid hormone-induced osteoclastogenesis

Glucocorticoid (GC) therapy decreases bone mass and increases the risk of fractures. We investigated interactions between the GC dexamethasone (DEX) and the bone resorptive agents 1,25(OH)₂-vitamin D₃ (D3) and parathyroid hormone (PTH) on osteoclastogenesis. We observed a synergistic potentiation of osteoclast progenitor cell differentiation and formation of osteoclasts when DEX was added to either D3- or PTH-treated mouse bone marrow cell (BMC) cultures. Cotreatment of DEX with D3 or PTH increased gene encoding calcitonin receptor (Calcr), acid phosphatase 5, tartrate resistant (Acp5), cathepsin K (Ctsk), and TNF superfamily member 11 (Tnfsf11) mRNA, receptor activator of NF-κB ligand protein (RANKL), numbers of osteoclasts on plastic, and pit formation and release of C-terminal fragment of type I collagen from cells cultured on bone slices. Enhanced RANKL protein expression caused by D3 and DEX was absent in BMC from mice in which the GC receptor (GR) was deleted in stromal cells/osteoblasts. Synergistic interactions between DEX and D3 on RANKL and osteoclast formation were present in BMC from mice with attenuated GR dimerization. These data demonstrate that the GR cooperates with D3 and PTH signaling, causing massive osteoclastogenesis, which may explain the rapid bone loss observed with high dosages of GC treatment.-Conaway, H. H., Henning, P., Lie, A., Tuckermann, J., Lerner, U. H. Glucocorticoids employ the monomeric glucocorticoid receptor to potentiate vitamin D₃ and parathyroid hormone-induced osteoclastogenesis.

ADAM Metalloproteinases as Potential Drug Targets

The ADAMs, together with ADAMTSs and snake venom metalloproteases (SVMPs), are members of the Adamalysin family. Differences in structural organization, functions and localization are known and their domains, catalytic or non-catalytic, show key roles in the substrate recognition and protease activity. Some ADAMs, as membrane-bound enzymes, show sheddase activity. Sheddases are key to modulation of functional proteins such as the tumor necrosis factor, growth factors, cytokines and their receptors, adhesion proteins, signaling molecules and stress molecules involved in immunity. These activities take part in the regulation of several physiological and pathological processes including inflammation, tumor growth, metastatic progression and infectious diseases. On these bases, some ADAMs are currently investigated as drug targets to develop new alternative therapies in many fields of medicine. This review will be focused on these aspects.

Soluble RANKL is physiologically dispensable but accelerates tumour metastasis to bone

Receptor activator of NF-κB ligand (RANKL) is a multifunctional cytokine known to affect immune and skeletal systems, as well as oncogenesis and metastasis^1-4. RANKL is synthesized as a membrane-bound molecule, and cleaved into its soluble form by proteases^5-7. As the soluble form of RANKL does not contribute greatly to bone remodelling or ovariectomy-induced bone loss⁸, whether soluble RANKL has a role in pathological settings remains unclear. Here we show that soluble RANKL promotes the formation of tumour metastases in bone. Mice that selectively lack soluble RANKL (Tnfsf11^ΔS/ΔS)^5-7,9 have normal bone homoeostasis and develop a normal immune system but display markedly reduced numbers of bone metastases after intracardiac injection of RANK-expressing melanoma and breast cancer cells. Deletion of soluble RANKL does not affect osteoclast numbers in metastatic lesions or tumour metastasis to non-skeletal tissues. Therefore, soluble RANKL is dispensable for physiological regulation of bone and immune systems, but has a distinct and pivotal role in the promotion of bone metastases.

NF-κB-dependent RANKL expression in a mouse model of immature T-cell leukemia

Activation of the receptor activator of nuclear factor-κB (RANK) by its ligand (RANKL) is involved in both solid and hematological malignancies, including multiple myeloma, acute myeloid leukemia and B-cell leukemia. Although RANKL expression has been described in normal T cells, a potential role in T-cell leukemia remains undefined. Here, we used a model of immature T-cell leukemia/lymphoma, the TEL-JAK2 transgenic mice, to assess RANKL expression in leukemic cells and its regulatory mechanisms. We found that Rankl mRNA was significantly overexpressed in leukemic T cells when compared to wild-type thymocytes, their nonmalignant counterparts. Moreover, Rankl mRNA and RANKL surface expression in leukemic cells was induced by T-cell receptor (TCR) signaling activation, dependently on the NF-κB signaling pathway. These results indicate that TCR-activated leukemic T cells express high levels of RANKL and are potential inducers of RANK signaling in microenvironmental cells.

Structure of the 4-1BB/4-1BBL complex and distinct binding and functional properties of utomilumab and urelumab

4-1BB (CD137, TNFRSF9) is an inducible costimulatory receptor expressed on activated T cells. Clinical trials of two agonist antibodies, utomilumab (PF-05082566) and urelumab (BMS-663513), are ongoing in multiple cancer indications, and both antibodies demonstrate distinct activities in the clinic. To understand these differences, we solved structures of the human 4-1BB/4-1BBL complex, the 4-1BBL trimer alone, and 4-1BB bound to utomilumab or urelumab. The 4-1BB/4-1BBL complex displays a unique interaction between receptor and ligand when compared with other TNF family members. Furthermore, our ligand-only structure differs from previously published data. Utomilumab, a ligand-blocking antibody, binds 4-1BB between CRDs 3 and 4. In contrast, urelumab binds 4-1BB CRD-1, away from the ligand binding site. Finally, cell-based assays demonstrate utomilumab is a milder agonist than urelumab. Collectively, our data provide a deeper understanding of the 4-1BB signaling complex, providing a template for future development of next generation 4-1BB targeted biologics.

Expression of the Immune Checkpoint Modulator OX40 in Acute Lymphoblastic Leukemia Is Associated with BCR-ABL Positivity

OX40 and its ligand are members of the TNF/TNF receptor superfamily, which includes various molecules influencing cellular signaling and function of both tumor and immune cells. The ability of OX40 to promote proliferation and differentiation of activated T cells fueled present attempts to modulate this immune checkpoint to reinforce antitumor immunity. While we recently found evidence for the involvement of OX40 in pathophysiology of acute myeloid leukemia including natural killer (NK) cell immunosurveillance, less is known on its role in acute lymphoblastic leukemia (ALL). In the present study, OX40 expression on ALL cells was significantly associated with positivity for the adverse risk factor BCR-ABL. In line, signaling via OX40 increased metabolic activity of primary ALL cells and resulted in release of cytokines involved in disease pathophysiology. Furthermore, interaction of ALL-expressed OX40 with its cognate ligand on NK cells stimulated ALL cell lysis. The data presented thus not only identify the yet unknown involvement of OX40/OX40L in ALL pathophysiology and NK cell immunosurveillance but also point to the necessity to thoroughly consider the consequences of modulating the OX40/OX40L molecule system beyond its effects on T cells when developing OX40-targeting approaches for cancer immunotherapy.

Identification of N-Hydroxycinnamamide analogues and their bio-evaluation against breast cancer cell lines

The present study demonstrates the identification of N-hydroxycinnamamide derivatives and their anticancer potential against human triple-negative breast cancer cell line MDA-MB‑231, MCF-7 and non-malignant origin cell line, HEK-293 (human embryonic kidney). MTT assay was studied with HEK-293 cell line. Anticancer potential of the N-hydroxycinnamamide derivatives were compared with marked drug Tamoxifen through in vitro study. The compound numbers 3b and 3h exhibit most potent activity against antagonistic breast cancer cells (MDA-MB-231) with IC₅₀13μM and 5μM respectively. Compound 3h promotes DNA fragmentation and induction of apoptosis. Furthermore, loss of mitochondrial membrane potential induced by compound 3h. The major mechanism of compound 3h for anti-breast cancer activity was probably initiation of reactive oxygen species (ROS) in cancer cells thereby persuading apoptotic cell deaths in cancer cells.

Immunomodulatory drug methotrexate used to treat patients with chronic inflammatory rheumatisms post-chikungunya does not impair the synovial antiviral and bone repair responses

Chikungunya virus (CHIKV) is a mosquito-transmitted RNA alphavirus causing major outbreaks of infectious chronic inflammatory rheumatisms (CIR). Recently, methotrexate (MTX), a disease modifying anti-rheumatic drug has been used successfully to treat patients suffering from rheumatoid-like arthritis post-CHIK but its immunomodulatory activity in the context of viral persistence has been a matter of concerns. We herein used a model of primary human synovial fibroblasts (HSF) and the synthetic molecule polyriboinosinic:polyribocytidylic acid (PIC) to mimic chronic infectious settings in the joints of CHIKV infected patients. The innate antiviral immune and inflammatory responses were investigated in response to MTX used at the therapeutic concentration of 1 μM. We found that MTX did not affect cellular viability as indicated by the LDH release assay. By quantitative RT-PCR, we observed that HSF responded robustly to PIC by increasing ISG15 and IFNβ mRNA levels. Furthermore, PIC upregulated the mRNA expression of two of the major pattern recognition receptors, RIG-I and MDA5 involved in the innate immune detection of viral RNA. MTX did not impact the antiviral response of PIC on ISG15, IFNβ, RIG-I and MDA5 mRNA expressions. MTX alone or combined with PIC did not affect the expression of proinflammatory CCL2 and CXCL8 chemokines. PIC strongly upregulated the mRNA and protein expression of osteoclastogenic factors (IL-6, GM-CSF but not RANKL). Critically, MTX treatment alone or combined with PIC did not affect the expression of all three tested osteoclastogenic cytokines. We found that MTX alone did not increase the capacity of CHIKV to infect and replicate in HSF. In conclusion, our study argues for a beneficial effect of MTX to treat CIR post-CHIKV given that it does not critically impact the antiviral, the proinflammatory and the bone tissue remodeling responses of synovial cells.

Chikungunya is a mosquito-borne virus (CHIKV) and has been incriminated in the development of arthralgia (pain of the joint) and arthritis particularly in elderly patients. Methotrexate (MTX) has been used widely to effectively treat these chronic rheumatic symptoms. Using a model of primary human joint fibroblasts (HSF), we investigated the capacity of the MTX immunosuppressive drug to affect the immune antiviral and inflammatory responses essential to clear the virus while allowing bone tissue repair. This study is important given that CHIKV and its RNA were shown to persist in the joint for months to years post infection and leading to injuries through ill-characterized mechanisms. The molecule PIC was used to mimic the effect of viral RNA. Interestingly, we found that MTX did not affect the expression of several proinflammatory and bone repair factors by HSF. Remarkably, MTX did not also impair the antiviral response of synovial fibroblasts. Our study revealed for the first time that MTX treatment should be considered as safe even in the context of viral persistence associated with chronic inflammation. MTX will not affect the capacity of the synovial tissue to maintain antiviral mechanism, to control inflammation and to promote bone tissue repair.

Bone: Another potential target to treat, prevent and predict diabetes

Type 2 diabetes mellitus is now a worldwide health problem with increasing prevalence. Mounting efforts have been made to treat, prevent and predict this chronic disease. In recent years, increasing evidence from mice and clinical studies suggests that bone-derived molecules modulate glucose metabolism. This review aims to summarize our current understanding of the interplay between bone and glucose metabolism and to highlight potential new means of therapeutic intervention. The first molecule recognized as a link between bone and glucose metabolism is osteocalcin (OCN), which functions in its active form, that is, undercarboxylated OCN (ucOC). ucOC acts in promoting insulin expression and secretion, facilitating insulin sensitivity, and favouring glucose and fatty acid uptake and utilization. A second bone-derived molecule, lipocalin2, functions in suppressing appetite in mice through its action on the hypothalamus. Osteocytes, the most abundant cells in bone matrix, are suggested to act on the browning of white adipose tissue and energy expenditure through secretion of bone morphogenetic protein 7 and sclerostin. The involvement of bone resorption in glucose homeostasis has also been examined. However, there is evidence indicating the implication of the receptor activator of nuclear factor κ-B ligand, neuropeptide Y, and other known and unidentified bone-derived factors that function in glucose homeostasis. We summarize recent advances and the rationale for treating, preventing and predicting diabetes by skeleton intervention.

Soluble RANKL contributes to osteoclast formation in adult mice but not ovariectomy-induced bone loss

Receptor activator of NFkB ligand (RANKL) is a TNF-family cytokine required for osteoclast formation, as well as immune cell and mammary gland development. It is produced as a membrane-bound protein that can be shed to form a soluble protein. We created mice harboring a sheddase-resistant form of RANKL, in which soluble RANKL is undetectable in the circulation. Lack of soluble RANKL does not affect bone mass or structure in growing mice but reduces osteoclast number and increases cancellous bone mass in adult mice. Nonetheless, the bone loss caused by estrogen deficiency is unaffected by the lack of soluble RANKL. Lymphocyte number, lymph node development, and mammary gland development are also unaffected by the absence of soluble RANKL. These results demonstrate that the membrane-bound form of RANKL is sufficient for most functions of this protein but that the soluble form does contribute to physiological bone remodeling in adult mice.

RANKL is a cytokine produced as a membrane-bound and a secreted protein. Here, using mice lacking soluble RANKL, the authors show that the secreted protein is important for osteoclast function, but not for mammary gland and lymphocyte development.

The Tumor Necrosis Factor Superfamily Member RANKL Suppresses Effector Cytokine Production in Group 3 Innate Lymphoid Cells

While signals that activate group 3 innate lymphoid cells (ILC3s) have been described, the factors that negatively regulate these cells are less well understood. Here we found that the tumor necrosis factor (TNF) superfamily member receptor activator of nuclear factor κB ligand (RANKL) suppressed ILC3 activity in the intestine. Deletion of RANKL in ILC3s and T cells increased C-C motif chemokine receptor 6 (CCR6)⁺ ILC3 abundance and enhanced production of interleukin-17A (IL-17A) and IL-22 in response to IL-23 and during infection with the enteric murine pathogen Citrobacter rodentium. Additionally, CCR6⁺ ILC3s produced higher amounts of the master transcriptional regulator RORγt at steady state in the absence of RANKL. RANKL-mediated suppression was independent of T cells, and instead occurred via interactions between CCR6⁺ ILC3s that expressed both RANKL and its receptor, RANK. Thus, RANK-RANKL interactions between ILC3s regulate ILC3 abundance and activation, suggesting that cell clustering may control ILC3 activity.

Lamins and bone disorders: current understanding and perspectives

Lamin A/C is a major constituent of the nuclear lamina implicated in a number of genetic diseases, collectively known as laminopathies. The most severe forms of laminopathies feature, among other symptoms, congenital scoliosis, osteoporosis, osteolysis or delayed cranial ossification.

Importantly, specific bone districts are typically affected in laminopathies. Spine is severely affected in LMNA-linked congenital muscular dystrophy. Mandible, terminal phalanges and clavicles undergo osteolytic processes in progeroid laminopathies and Restrictive Dermopathy, a lethal developmental laminopathy. This specificity suggests that lamin A/C regulates fine mechanisms of bone turnover, as supported by data showing that lamin A/C mutations activate non-canonical pathways of osteoclastogenesis, as the one dependent on TGF beta 2.

Here, we review current knowledge on laminopathies affecting bone and LMNA involvement in bone turnover and highlight lamin-dependent mechanisms causing bone disorders. This knowledge can be exploited to identify new therapeutic approaches not only for laminopathies, but also for other rare diseases featuring bone abnormalities.

IL-3 Differentially Regulates Membrane and Soluble RANKL in Osteoblasts through Metalloproteases and the JAK2/STAT5 Pathway and Improves the RANKL/OPG Ratio in Adult Mice

Bone remodeling comprises balanced activities between osteoclasts and osteoblasts, which is regulated by various factors, including hormones and cytokines. We previously reported that IL-3 inhibits osteoclast differentiation and pathological bone loss. IL-3 also enhances osteoblast differentiation and bone formation from mesenchymal stem cells. However, the role of IL-3 in regulation of osteoblast–osteoclast interactions and underlying mechanisms is not yet delineated. In this study, we investigated the role of IL-3 on the regulation of osteoblast-specific molecules, receptor activator of NF-κB ligand (RANKL), and osteoprotegerin (OPG) that modulate bone homeostasis. We found that IL-3 increases RANKL expression at both the transcriptional and translational levels, and it showed no effect on OPG expression in calvarial osteoblasts. The increased RANKL expression by IL-3 induces mononuclear osteoclasts; however, it does not induce multinuclear osteoclasts. Interestingly, IL-3 decreases soluble RANKL by reducing ectodomain shedding of membrane RANKL through downregulation of metalloproteases mainly a disintegrin and metalloproteinase (ADAM)10, ADAM17, ADAM19, and MMP3. Moreover, IL-3 increases membrane RANKL by activating the JAK2/STAT5 pathway. Furthermore, IL-3 enhances RANKL expression in mesenchymal stem cells of wild-type mice but not in STAT5a knockout mice. Interestingly, IL-3 restores RANKL expression in adult mice by enhancing bone-specific RANKL and decreasing serum RANKL. Furthermore, IL-3 increases the serum OPG level in adult mice. Thus, our results reveal, to our knowledge for the first time, that IL-3 differentially regulates two functional forms of RANKL through metalloproteases and the JAK2/STAT5 pathway, and it helps in restoring the decreased RANKL/OPG ratio in adult mice. Notably, our studies indicate the novel role of IL-3 in regulating bone homeostasis in important skeletal disorders.

The Immune Checkpoint Modulator OX40 and Its Ligand OX40L in NK-Cell Immunosurveillance and Acute Myeloid Leukemia

The TNF receptor family member OX40 promotes activation and proliferation of T cells, which fuels efforts to modulate this immune checkpoint to reinforce antitumor immunity. Besides T cells, NK cells are a second cytotoxic lymphocyte subset that contributes to antitumor immunity, particularly in leukemia. Accordingly, these cells are being clinically evaluated for cancer treatment through multiple approaches, such as adoptive transfer of ex vivo expanded polyclonal NK cells (pNKC). Here, we analyzed whether and how OX40 and its ligand (OX40L) influence NK-cell function and antileukemia reactivity. We report that OX40 is expressed on leukemic blasts in a substantial percentage of patients with acute myeloid leukemia (AML) and that OX40 can, after stimulation with agonistic OX40 antibodies, mediate proliferation and release of cytokines that act as growth and survival factors for the leukemic cells. We also demonstrate that pNKC differentially express OX40L, depending on the protocol used for their generation. OX40L signaling promoted NK-cell activation, cytokine production, and cytotoxicity, and disruption of OX40-OX40L interaction impaired pNKC reactivity against primary AML cells. Together, our data implicate OX40/OX40L in disease pathophysiology of AML and in NK-cell immunosurveillance. Our findings indicate that effects of the OX40-OX40L receptor-ligand system in other immune cell subsets and also malignant cells should be taken into account when developing OX40-targeted approaches for cancer immunotherapy. Cancer Immunol Res; 6(2); 209-21. ©2018 AACR.

Cystic Fibrosis, Cystic Fibrosis Transmembrane Conductance Regulator and Drugs: Insights from Cellular Trafficking

The eukaryotic cell is organized into membrane-delineated compartments that are characterized by specific cadres of proteins sustaining biochemically distinct cellular processes. The appropriate subcellular localization of proteins is key to proper organelle function and provides a physiological context for cellular processes. Disruption of normal trafficking pathways for proteins is seen in several genetic diseases, where a protein's absence for a specific subcellular compartment leads to organelle disruption, and in the context of an individual, a disruption of normal physiology. Importantly, several drug therapies can also alter protein trafficking, causing unwanted side effects. Thus, a deeper understanding of trafficking pathways needs to be appreciated as novel therapeutic modalities are proposed. Despite the promising efficacy of novel therapeutic agents, the intracellular bioavailability of these compounds has proved to be a potential barrier, leading to failures in treatments for various diseases and disorders. While endocytosis of drug moieties provides an efficient means of getting material into cells, the subsequent release and endosomal escape of materials into the cytosol where they need to act has been a barrier. An understanding of cellular protein/lipid trafficking pathways has opened up strategies for increasing drug bioavailability. Approaches to enhance endosomal exit have greatly increased the cytosolic bioavailability of drugs and will provide a means of investigating previous drugs that may have been shelved due to their low cytosolic concentration.

Small leucine rich proteoglycans, a novel link to osteoclastogenesis

Biglycan (Bgn) and Fibromodulin (Fmod) are subtypes of the small leucine-rich family of proteoglycans (SLRP). In this study we examined the skeletal phenotype of BgnFmod double knockout (BgnFmod KO) mice and found they were smaller in size and have markedly reduced bone mass compared to WT. The low bone mass (LBM) phenotype is the result of both the osteoblasts and osteoclasts from BgnFmod KO mice having higher differentiation potential and being more active compared to WT mice. Using multiple approaches, we showed that both Bgn and Fmod directly bind TNFα as well as RANKL in a dose dependent manner and that despite expressing higher levels of both TNFα and RANKL, BgnFmod KO derived osteoblasts cannot retain these cytokines in the vicinity of the cells, which leads to elevated TNFα and RANKL signaling and enhanced osteoclastogenesis. Furthermore, adding either Bgn or Fmod to osteoclast precursor cultures significantly attenuated the cells ability to form TRAP positive, multinucleated giant cells. In summary, our data indicates that Bgn and Fmod expressed by the bone forming cells, are novel coupling ECM components that control bone mass through sequestration of TNFα and/or RANKL, thereby adjusting their bioavailability in order to regulate osteoclastogenesis.

Cyclophosphamide causes osteoporosis in C57BL/6 male mice: suppressive effects of cyclophosphamide on osteoblastogenesis and osteoclastogenesis

The clinical evidence indicated that cyclophosphamide (CPD), one of the chemotherapy drugs, caused severe deteriorations in bones of cancer patients. However, the exact mechanisms by which CPD exerts effects on bone remodeling is not yet fully elucidated. Therefore, this study was performed to investigate the role and potential mechanism of CPD in osteoblastogenesis and osteoclastogenesis. Here it was found that CPD treatment (100mg/kg/day) for 7 days led to osteoporosis phenotype in male mice. CPD inhibited osteoblastogenesis as shown by decreasing the number and differentiation of bone mesenchymal stem cells (MSCs) and reducing the formation and activity of osteoblasts. Moreover, CPD suppressed the osteoclastogenesis mediated by receptor activator for nuclear factor-κ B ligand (RANKL) as shown by reducing the maturation and activity of osteoclasts. At the molecular level, CPD exerted inhibitory effect on the expression of components (Cyclin D1, β-catenin, Wnt 1, Wnt10b) of Wnt/β-catenin signaling pathway in MSCs and osteoblasts-specific factors (alkaline phosphatase, Runx2, and osteocalcin). CPD also down-regulated the expression of the components (tumor necrosis factor receptor-associated factor 6, nuclear factor of activated T-cells cytoplasm 1, c-Fos and NF-κB) of RANKL signaling pathway and the factors (matrix metalloproteinase 9, cathepsin K, tartrate-resistant acid phosphates and carbonic anhydrase II) for osteoclastic activity. Taken together, this study demonstrated that the short-term treatment of CPD induced osteoporosis in mice and the underlying mechanism might be attributed to its marked suppression on osteoblastogenesis and osteoclastogenesis, especially the effect of CPD on bone formation might play a dominant role in its detrimental effects on bone remodeling.

Identification of subepithelial mesenchymal cells that induce IgA and diversify gut microbiota

Immunoglobulin A (IgA) maintains a symbiotic equilibrium with intestinal microbes. IgA induction in the gut-associated lymphoid tissues (GALTs) is dependent on microbial sampling and cellular interaction in the subepithelial dome (SED). However it is unclear how IgA induction is predominantly initiated in the SED. Here we show that previously unrecognized mesenchymal cells in the SED of GALTs regulate bacteria-specific IgA production and diversify the gut microbiota. Mesenchymal cells expressing the cytokine RANKL directly interact with the gut epithelium to control CCL20 expression and microfold (M) cell differentiation. The deletion of mesenchymal RANKL impairs M cell-dependent antigen sampling and B cell-dendritic cell interaction in the SED, which results in a reduction in IgA production and a decrease in microbial diversity. Thus, the subepithelial mesenchymal cells that serve as M cell inducers have a fundamental role in the maintenance of intestinal immune homeostasis.

SheddomeDB: the ectodomain shedding database for membrane-bound shed markers

BACKGROUND

A number of membrane-anchored proteins are known to be released from cell surface via ectodomain shedding. The cleavage and release of membrane proteins has been shown to modulate various cellular processes and disease pathologies. Numerous studies revealed that cell membrane molecules of diverse functional groups are subjected to proteolytic cleavage, and the released soluble form of proteins may modulate various signaling processes. Therefore, in addition to the secreted protein markers that undergo secretion through the secretory pathway, the shed membrane proteins may comprise an additional resource of noninvasive and accessible biomarkers. In this context, identifying the membrane-bound proteins that will be shed has become important in the discovery of clinically noninvasive biomarkers. Nevertheless, a data repository for biological and clinical researchers to review the shedding information, which is experimentally validated, for membrane-bound protein shed markers is still lacking.

RESULTS

In this study, the database SheddomeDB was developed to integrate publicly available data of the shed membrane proteins. A comprehensive literature survey was performed to collect the membrane proteins that were verified to be cleaved or released in the supernatant by immunological-based validation experiments. From 436 studies on shedding, 401 validated shed membrane proteins were included, among which 199 shed membrane proteins have not been annotated or validated yet by existing cleavage databases. SheddomeDB attempted to provide a comprehensive shedding report, including the regulation of shedding machinery and the related function or diseases involved in the shedding events. In addition, our published tool ShedP was embedded into SheddomeDB to support researchers for predicting the shedding event on unknown or unrecorded membrane proteins.

CONCLUSIONS

To the best of our knowledge, SheddomeDB is the first database for the identification of experimentally validated shed membrane proteins and currently may provide the most number of membrane proteins for reviewing the shedding information. The database included membrane-bound shed markers associated with numerous cellular processes and diseases, and some of these markers are potential novel markers because they are not annotated or validated yet in other databases. SheddomeDB may provide a useful resource for discovering membrane-bound shed markers. The interactive web of SheddomeDB is publicly available at http://bal.ym.edu.tw/SheddomeDB/ .

Non-Canonical (RANKL-Independent) Pathways of Osteoclast Differentiation and Their Role in Musculoskeletal Diseases

Osteoclasts are multinucleated cells derived from mononuclear phagocyte precursors (monocytes, macrophages); in the canonical pathway of osteoclastogenesis, these cells fuse and differentiate to form specialised bone-resorbing osteoclasts in the presence of receptor activator for nuclear factor kappa B ligand (RANKL). Non-canonical pathways of osteoclastogenesis have been described in which several cytokines and growth factors are able to substitute for RANKL. These humoral factors can generally be divided into those which, like RANKL, are tumour necrosis family (TNF) superfamily members and those which are not; the former include TNFα lymphotoxin exhibiting inducible expression and competing with herpes simplex virus glycoprotein D for herpesvirus entry mediator, a receptor expressed by T lymphocytes (LIGHT), a proliferation inducing ligand (APRIL) and B cell activating factor (BAFF); the latter include transforming growth factor beta (TGF-β), interleukin-6 (IL-6), IL-8, IL-11, nerve growth factor (NGF), insulin-like growth factor-I (IGF-I) and IGF-II. This review summarises the evidence for these RANKL substitutes in inducing osteoclast differentiation from tissue-derived and circulating mononuclear phagocytes. It also assesses the role these factors are likely to play in promoting the pathological bone resorption seen in many inflammatory and neoplastic lesions of bone and joint including rheumatoid arthritis, aseptic implant loosening and primary and secondary tumours of bone.

Bone-Seeking Matrix Metalloproteinase-2 Inhibitors Prevent Bone Metastatic Breast Cancer Growth

Bone metastasis is common during breast cancer progression. Matrix metalloproteinase-2 (MMP-2) is significantly associated with aggressive breast cancer and poorer overall survival. In bone, tumor- or host-derived MMP-2 contributes to breast cancer growth and does so by processing substrates, including type I collagen and TGFβ latency proteins. These data provide strong rationale for the application of MMP-2 inhibitors to treat the disease. However, in vivo, MMP-2 is systemically expressed. Therefore, to overcome potential toxicities noted with previous broad-spectrum MMP inhibitors (MMPIs), we used highly selective bisphosphonic-based MMP-2 inhibitors (BMMPIs) that allowed for specific bone targeting. In vitro, BMMPIs affected the viability of breast cancer cell lines and osteoclast precursors, but not osteoblasts. In vivo, we demonstrated using two bone metastatic models (PyMT-R221A and 4T1) that BMMPI treatment significantly reduced tumor growth and tumor-associated bone destruction. In addition, BMMPIs are superior in promoting tumor apoptosis compared with the standard-of-care bisphosphonate, zoledronate. We demonstrated MMP-2-selective inhibition in the bone microenvironment using specific and broad-spectrum MMP probes. Furthermore, compared with zoledronate, BMMPI-treated mice had significantly lower levels of TGFβ signaling and MMP-generated type I collagen carboxy-terminal fragments. Taken together, our data show the feasibility of selective inhibition of MMPs in the bone metastatic breast cancer microenvironment. We posit that BMMPIs could be easily translated to the clinical setting for the treatment of bone metastases given the well-tolerated nature of bisphosphonates. Mol Cancer Ther; 16(3); 494-505. ©2017 AACR.

Low‑molecular weight fucoidan inhibits the differentiation of osteoclasts and reduces osteoporosis in ovariectomized rats

Fucoidan is a type of sulfated polysaccharide isolated from seaweed. The present study used ovariectomized Sprague‑Dawley rats, which were treated with fucoidan. The effects of fucoidan on bone metabolism, density and microarchitecture were assessed using micro‑computed tomography (CT), histomorphometric analysis, biochemical markers of bone metabolism (Serum procollagen type I N propeptide and C‑terminal telopeptide‑1) and tests of mechanical competence of the femur. In addition, the effects of low‑molecular weight fucoidan (LMWF) on in vitro cultured osteoclasts were examined, in order to determine the mechanisms underlying LMWF‑induced osteoclastic inhibition. In ovariectomized rats, LMWF increased femoral bone density. Micro‑CT scan also revealed that LMWF prevented microarchitectural deterioration and histomorphometric analysis determined that LMWF increased trabecular bone number and reduced the surface of bone resorption. In addition, LMWF reduced the high bone turnover rate, and improved the mechanical properties of the femur in ovariectomized rats. In vitro experiments revealed that LMWF inhibited the receptor activator of nuclear factor κB ligand (RANKL) and macrophage colony‑stimulating factor‑induced differentiation of RAW264.7 cells into tartrate‑resistant acid phosphatase (TRAP)‑positive osteoclasts, and reduced the bone resorption surface of the osteoclasts. Reverse transcription‑quantitative polymerase chain reaction demonstrated that LMWF inhibited mRNA expression of TRAP, matrix metallopeptidase‑9, nuclear activator of activated T‑cells 1, and osteoclast‑associated immunoglobulin‑like receptor, which are components of the signaling pathway for osteoclast differentiation. LMWF had no effect on RANK mRNA expression. In conclusion, the present study confirmed that LMWF inhibited osteoclast differentiation and bone resorption, and may be a potential treatment for osteoporosis in ovariectomized rats.

TNF superfamily cytokines in the promotion of Th9 differentiation and immunopathology

The tumor necrosis factor (TNF) receptors and their corresponding cytokine ligands have been implicated in many aspects of the biology of immune functions. TNF receptors have key roles during various stages of T cell homeostasis. Many of them can co-stimulate lymphocyte proliferation and cytokine production. Additionally, several TNF cytokines can regulate T cell differentiation, including promoting Th1, Th2, Th17, and more recently the newly described Th9 subset. Four TNF family cytokines have been identified as regulators for IL-9 production by T cells. OX40L, TL1A, and GITRL can promote Th9 formation but can also divert iTreg into Th9, while 4-1BBL seems to inhibit IL-9 production from iTreg and has not been studied for its ability to promote Th9 generation. Regulation of IL-9 production by TNF family cytokines has repercussions in vivo, including enhancement of anti-tumor immunity and immunopathology in allergic lung and ocular inflammation. Regulating T cell production of IL-9 through blockade or agonism of TNF family cytokine receptors may be a therapeutic strategy for autoimmune and allergic diseases and in tumor.

Parathyroid hormone induces expression and proteolytic processing of Rankl in primary murine osteoblasts

Rankl, the major pro-osteoclastogenic cytokine, is synthesized as a transmembrane protein that can be cleaved by specific endopeptidases to release a soluble form (sRankl). We have previously reported that interleukin-33 (IL-33) induces expression of Tnfsf11, the Rankl-encoding gene, in primary osteoblasts, but we failed to detect sRankl in the medium. Since we also found that PTH treatment caused sRankl release in a similar experimental setting, we directly compared the influence of the two molecules. Here we show that treatment of primary murine osteoblasts with PTH causes sRankl release into the medium, whereas IL-33 only induces Tnfsf11 expression. This difference was not explainable by alternative splicing or by PTH-specific induction of endopeptidases previously shown to facilitate Rankl processing. Since sRankl release after PTH administration was blocked in the presence a broad-spectrum matrix metalloprotease inhibitor, we applied genome-wide expression analyses to identify transcriptional targets of PTH in osteoblasts. We thereby confirmed some of the effects of PTH established in other systems, but additionally identified few PTH-induced genes encoding metalloproteases. By comparing expression of these genes following administration of IL-33, PTH and various other Tnfsf11-inducing molecules, we observed that PTH was the only molecule simultaneously inducing sRankl release and Adamts1 expression. The functional relevance of the putative influence of PTH on Rankl processing was further confirmed in vivo, as we found that daily injection of PTH into wildtype mice did not only increase bone formation, but also osteoclastogenesis and sRankl concentrations in the serum. Taken together, our findings demonstrate that transcriptional effects on Tnfsf11 expression do not generally trigger sRankl release and that PTH has a unique activity to promote the proteolytic processing of Rankl.

Soluble RANKL Cleaved from Activated Lymphocytes by TNF-α-Converting Enzyme Contributes to Osteoclastogenesis in Periodontitis

Host immune responses play a key role in promoting bone resorption in periodontitis via receptor activator of NF-κB ligand (RANKL)-dependent osteoclastogenesis. Both membrane-bound RANKL (mRANKL) expressed on lymphocytes and soluble RANKL (sRANKL) are found in periodontal lesions. However, the underlying mechanism and cellular source of sRANKL release and its biological role in periodontitis are unclear. TNF-α-converting enzyme (TACE) is reported to cleave the following: 1) precursor TNF-α with release of mature, soluble TNF-α and 2) mRANKL with release of sRANKL. Both soluble TNF-α and sRANKL are found in the periodontitis lesion, leading to the hypothesis that TACE expressed on lymphocytes is engaged in RANKL shedding and that the resulting sRANKL induces osteoclastogenesis. In the current study, upon stimulating PBLs with mitogens in vitro, RANKL expression, sRANKL secretion, and TACE expression were all upregulated. Among the four putative mRANKL sheddases examined in neutralization assays, TACE was the only functional sheddase able to cleave mRANKL expressed on PBL. Moreover, PBL culture supernatant stimulated with mitogens in the presence of anti-TACE Ab or anti-RANKL Ab showed a marked reduction of osteoclastogenesis from osteoclast precursors, indicating that TACE-mediated sRANKL may possess sufficient osteoclastogenic activity. According to double-color confocal microscopy, B cells expressed a more pronounced level of RANKL and TACE expression than T cells or monocytes in periodontally diseased gingiva. Conditioned medium of patients' gingival lymphocyte culture increased in vitro osteoclastogenic activity, which was suppressed by the addition of anti-TACE Ab and anti-RANKL Ab. Therefore, TACE-mediated cleavage of sRANKL from activated lymphocytes, especially B cells, can promote osteoclastogenesis in periodontitis.

A-Disintegrin and Metalloproteinase (ADAM) 17 Enzymatically Degrades Interferon-gamma

Interferon-gamma (IFN-γ) is a pleiotropic cytokine that exerts anti-tumor and anti-osteoclastogenic effects. Although transcriptional and post-transcriptional regulation of IFN-γ is well understood, subsequent modifications of secreted IFN-γ are not fully elucidated. Previous research indicates that some cancer cells escape immune surveillance and metastasize into bone tissue by inducing osteoclastic bone resorption. Peptidases of the a-disintegrin and metalloproteinase (ADAM) family are implicated in cancer cell proliferation and tumor progression. We hypothesized that the ADAM enzymes expressed by cancer cells degrades IFN-γ and attenuates IFN-γ-mediated anti-tumorigenic and anti-osteoclastogenic effects. Recombinant ADAM17 degraded IFN-γ into small fragments. The addition of ADAM17 to the culture supernatant of stimulated mouse splenocytes decreased IFN-γ concentration. However, ADAM17 inhibition in the stimulated mouse T-cells prevented IFN-γ degradation. ADAM17-expressing human breast cancer cell lines MCF-7 and MDA-MB-453 also degraded recombinant IFN-γ, but this was attenuated by ADAM17 inhibition. Degraded IFN-γ lost the functionality including the inhibititory effect on osteoclastogenesis. This is the first study to demonstrate the extracellular proteolytic degradation of IFN-γ by ADAM17. These results suggest that ADAM17-mediated degradation of IFN-γ may block the anti-tumorigenic and anti-osteoclastogenic effects of IFN-γ. ADAM17 inhibition may be useful for the treatment of attenuated cancer immune surveillance and/or bone metastases.

RANK-RANKL signalling in cancer

Oncogenic events combined with a favourable environment are the two main factors in the oncological process. The tumour microenvironment is composed of a complex, interconnected network of protagonists, including soluble factors such as cytokines, extracellular matrix components, interacting with fibroblasts, endothelial cells, immune cells and various specific cell types depending on the location of the cancer cells (e.g. pulmonary epithelium, osteoblasts). This diversity defines specific "niches" (e.g. vascular, immune, bone niches) involved in tumour growth and the metastatic process. These actors communicate together by direct intercellular communications and/or in an autocrine/paracrine/endocrine manner involving cytokines and growth factors. Among these glycoproteins, RANKL (receptor activator nuclear factor-κB ligand) and its receptor RANK (receptor activator nuclear factor), members of the TNF and TNFR superfamilies, have stimulated the interest of the scientific community. RANK is frequently expressed by cancer cells in contrast with RANKL which is frequently detected in the tumour microenvironment and together they participate in every step in cancer development. Their activities are markedly regulated by osteoprotegerin (OPG, a soluble decoy receptor) and its ligands, and by LGR4, a membrane receptor able to bind RANKL. The aim of the present review is to provide an overview of the functional implication of the RANK/RANKL system in cancer development, and to underline the most recent clinical studies.

Zoledronic acid increases the circulating soluble RANKL level in mice, with a further increase in lymphocyte-derived soluble RANKL in zoledronic acid- and glucocorticoid-treated mice stimulated with bacterial lipopolysaccharide

The nitrogen-containing bisphosphonate (BP) zoledronic acid (ZA) is a potent antiresorptive drug used in conjunction with standard cancer therapy to treat osteolysis or hypercalcemia due to malignancy. However, it is unclear how ZA influences the circulating levels of bone remodeling factors. The aim of this study was to evaluate the effects of ZA on the serum levels of soluble receptor activator of NF-kB ligand (sRANKL) and osteoprotegerin (OPG). The following four groups of C57BL/6 mice were used (five mice per group): (1) the placebo+phosphate-buffered saline (PBS) group, in which placebo-treated mice were injected once weekly with PBS for 4weeks; (2) the placebo+ZA group, in which placebo-treated mice were injected once weekly with ZA for 4weeks; (3) the prednisolone (PSL)+PBS group, in which PSL-treated mice were injected once weekly with PBS for 4weeks; and (4) the PSL+ZA group, in which PSL-treated mice were injected once weekly with ZA for 4weeks. At the 3-week time point, all mice were subjected to oral inflammatory stimulation with bacterial lipopolysaccharide (LPS). The sera of these mice were obtained every week and the levels of sRANKL and OPG were measured using enzyme-linked immunosorbent assay. At the time of sacrifice, femurs were prepared for micro-computed tomography (micro-CT), histological, and histomorphometric analyses. Our data indicated that ZA administration remarkably reduced bone turnover and significantly increased the basal level of sRANKL. Interestingly, the PSL+ZA group showed a dramatically elevated sRANKL level after LPS stimulation. In contrast, the PSL+ZA group in nonobese diabetic mice with severe combined immunodeficiency disease (NOD-SCID mice), which are characterized by the absence of functional T- and B-lymphocytes, showed no increase in the sRANKL level. Our data suggest that, particularly with combination treatment of ZA and glucocorticoids, surviving lymphocytes might be the source of inflammation-induced sRANKL. Thus, circulating sRANKL levels might be modulated by ZA.

Deletion of the Distal Tnfsf11 RL-D2 Enhancer That Contributes to PTH-Mediated RANKL Expression in Osteoblast Lineage Cells Results in a High Bone Mass Phenotype in Mice

Receptor activator of nuclear factor-κB ligand (RANKL) is a tumor necrosis factor (TNF)-like cytokine that is necessary for osteoclast formation and survival. Elevated RANKL synthesis is associated with both increased osteoclast number and bone resorption. Earlier studies identified an enhancer 76 kb upstream of the Tnfsf11 transcriptional start site (TSS) termed RL-D5 or the distal control region (DCR) that modulates RANKL expression in response to PTH, 1,25(OH)2D3,, and an array of cytokines. Mice lacking RL-D5 exhibit high bone mass associated with decreased RANKL expression in bone, spleen, and thymus. In addition to RL-D5, genome-wide studies have identified 9 additional Tnfsf11 enhancers residing upstream of the gene's TSS, which provide RANKL cell type-specificity and responsiveness to local and systemic factors. ChIP-chip analyses has revealed inducible vitamin D receptor (VDR) and cAMP response element-binding protein (CREB) binding at an enhancer termed RL-D2 23 kb upstream of the Tnfsf11 TSS in osteoblastic ST2 cells. Herein, we use ChIP-seq analyses to confirm this finding and then delete this enhancer from the mouse genome to determine its physiological role in vivo. RL-D2(-/-) primary stromal cells showed decreased RANKL-induction by both forskolin and 1,25(OH)2D3 ex vivo. Consistent with this, the parathyroid hormone (PTH) induction of RANKL expression was significantly blunted in RL-D2(-/-) mice in vivo. In contrast, lack of RL-D2 had no effect on 1,25(OH)2D3 induction of RANKL in vivo. Similar to the results found in RL-D5(-/-) mice, lack of RL-D2 led to decreased skeletal RANKL expression, resulting in decreased osteoclast numbers and a progressive increase in bone mineral density. Lack of RL-D2 increased cancellous bone mass in femur and spine but did not alter femoral cortical bone thickness. These results highlight the role of distal enhancers in the regulation of RANKL expression by PTH and perhaps 1,25(OH)2D3 and suggest that the RL-D2 and RL-D5 enhancers contribute in either an additive or synergistic manner to regulate bone remodeling.

Unique Distal Enhancers Linked to the Mouse Tnfsf11 Gene Direct Tissue-Specific and Inflammation-Induced Expression of RANKL

Receptor activator of nuclear factor κB ligand (RANKL) is expressed by a number of cell types to participate in diverse physiological functions. We have previously identified 10 distal RANKL enhancers. Earlier studies have shown that RL-D5 is a multifunctional RANKL enhancer. Deletion of RL-D5 from the mouse genome leads to lower skeletal and lymphoid tissue RANKL, causing a high bone mass phenotype. Herein, we determine the physiological role and lineage specificity of 2 additional RANKL enhancers, RL-D6 and RL-T1, which are located 83 and 123 kb upstream of the gene's transcriptional start site, respectively. Lack of RL-D6 or RL-T1 did not alter skeletal RANKL or bone mineral density up to 48 weeks of age. Although both RL-D5 and RL-T1 contributed to activation induction of T-cell RANKL, RL-T1 knockout mice had drastically low lymphocyte and lymphoid tissue RANKL levels, indicating that RL-T1 is the major regulator of lymphocyte RANKL. Moreover, RL-T1 knockout mice had lower circulating soluble RANKL, suggesting that lymphocytes are important sources of circulating soluble RANKL. Under physiological conditions, lack of RL-D6 did not alter RANKL expression. However, lack of RL-D5 or RL-D6, but not of RL-T1, blunted the oncostatin M and lipopolysaccharide induction of RANKL ex vivo and in vivo, suggesting that RL-D5 and RL-D6 coregulate the inflammation-mediated induction of RANKL in osteocytes and osteoblasts while lack of RL-D6 did not alter secondary hyperparathyroidism or lactation induction of RANKL or bone loss. These results suggest that although RL-D5 mediates RANKL expression in multiple lineages, other cell type- or factor-specific enhancers are required for its appropriate control, demonstrating the cell type-specific and complex regulation of RANKL expression.