Key roles of the OPG–RANK–RANKL system in bone oncology

Amicis Omnia Sunt Communia: NF-κB Inhibition as an Alternative to Overcome Osteosarcoma Heterogeneity

Tumor heterogeneity poses a significant challenge in osteosarcoma (OS) treatment. In this regard, the "omics" era has constantly expanded our understanding of biomarkers and altered signaling pathways (i.e., PI3K/AKT/mTOR, WNT/β-catenin, NOTCH, SHH/GLI, among others) involved in OS pathophysiology. Despite different players and complexities, many commonalities have been described, among which the nuclear factor kappa B (NF-κB) stands out. Its altered activation is pervasive in cancer, with pleiotropic action on many disease-relevant traits. Thus, in the scope of this article, we highlight the evidence of NF-κB dysregulation in OS and its integration with other cancer-related pathways while we summarize the repertoire of compounds that have been described to interfere with its action. In silico strategies were used to demonstrate that NF-κB is closely coordinated with other commonly dysregulated signaling pathways not only by functionally interacting with several of their members but also by actively participating in the regulation of their transcription. While existing inhibitors lack selectivity or act indirectly, the therapeutic potential of targeting NF-κB is indisputable, first for its multifunctionality on most cancer hallmarks, and secondly, because, as a common downstream effector of the many dysregulated pathways influencing OS aggressiveness, it turns complex regulatory networks into a simpler picture underneath molecular heterogeneity.

A comprehensive review and advanced biomolecule-based therapies for osteoporosis

BACKGROUND

The prevalence of osteoporosis (OP) on a global scale is significantly elevated that causes life threatening issues. The potential of groundbreaking biomolecular therapeutics in the field of OP is highly encouraging. The administration of biomolecular agents has the potential to mitigate the process of bone demineralization while concurrently augmenting the regenerative capacity of bone tissue, thereby facilitating a personalized therapeutic approach. Biomolecules-based therapies showed promising results in term of bone mass protection and restoration in OP.

AIM OF REVIEW

We summarized the recent biomolecular therapies with notable progress in clinical, demonstrating the potential to transform illness management. These treatments frequently utilize different biomolecule based strategies. Biomolecular therapeutics has a targeted character, which results in heightened specificity and less off-target effects, ultimately leading to increased patient outcomes. These aspects have the capacity to greatly enhance the management of OP, thus resulting in a major enhancement in the quality of life encountered by individuals affected by this condition.

MicroRNA in medication related osteonecrosis of the jaw: a review

Medication related osteonecrosis of the jaw (MRONJ) is a condition caused by inhibition of the osteoclast activity by the anti-resorptive and anti-angiogenic drugs. Clinically, there is an exposure of the necrotic bone or a fistula which fails to heal for more than 8 weeks. The adjacent soft tissue is inflamed and pus may be present as a result of the secondary infection. To date, there is no consistent biomarker that could aid in the diagnosis of the disease. The aim of this review was to explore the literature on the microRNAs (miRNAs) related to medication related osteonecrosis of the jaw, and to describe the role of each miRNA as a biomarker for diagnostic purpose and others. Its role in therapeutics was also searched. It was shown that miR-21, miR-23a, and miR-145 were significantly different in a study involving multiple myeloma patients as well as in a human-animal study while miR-23a-3p and miR-23b-3p were 12- to 14-fold upregulated compared to the control group in an animal study. The role of the microRNAs in these studies were for diagnostics, predictor of progress of MRONJ and pathogenesis. Apart from its potential diagnostics role, microRNAs have been shown to be bone resorption regulator through miR-21, miR-23a and miR-145 and this could be utilized therapeutically.

Human cells with osteogenic potential in bone tissue research

Bone regeneration after injury or after surgical bone removal due to disease is a serious medical challenge. A variety of materials are being tested to replace a missing bone or tooth. Regeneration requires cells capable of proliferation and differentiation in bone tissue. Although there are many possible human cell types available for use as a model for each phase of this process, no cell type is ideal for each phase. Osteosarcoma cells are preferred for initial adhesion assays due to their easy cultivation and fast proliferation, but they are not suitable for subsequent differentiation testing due to their cancer origin and genetic differences from normal bone tissue. Mesenchymal stem cells are more suitable for biocompatibility testing, because they mimic natural conditions in healthy bone, but they proliferate more slowly, soon undergo senescence, and some subpopulations may exhibit weak osteodifferentiation. Primary human osteoblasts provide relevant results in evaluating the effect of biomaterials on cellular activity; however, their resources are limited for the same reasons, like for mesenchymal stem cells. This review article provides an overview of cell models for biocompatibility testing of materials used in bone tissue research.

Hyperoside suppresses osteoclasts differentiation and function through downregulating TRAF6/p38 MAPK signaling pathway

Hyperoside (HP), as a natural product, can promote proliferation and differentiation of osteoblasts and presents a protective effect on ovariectomized (OVX) mice. However, the inhibitory effect of HP on osteoclasts (OCs) and the potential mechanism remain to be elucidated. In this study, it was found that HP could effectively inhibit the differentiation and bone resorption of OCs, and its intrinsic molecular mechanism was related to the inhibition of TRAF6/p38 MAPK signaling pathway. Therefore, HP could be a promising natural compound for lytic bone diseases.

Asperuloside Prevents Peri-Implantitis via Suppression of NF-κB and ERK1/2 on Rats

Peri-implantitis is characterized by inflammatory cell infiltration and hyperactivation of the osteoclasts surrounding dental implants which can result in bone resorption and ultimately implant failure. Therefore, coordinating the activity of inflammatory response and bone-resorbing osteoclasts is crucial for the prevention of peri-implantitis. Asperuloside (ASP), an iridoid glycoside, has significant anti-inflammatory activities, suggesting the great potential in attenuating peri-implantitis bone resorption. A ligature-induced peri-implantitis model in the maxilla of rats was established, and the effects of ASP on preventing peri-implantitis were evaluated after four weeks of ligation using micro-CT and histological staining. RT-PCR, western blotting, tartrate-resistant acid phosphatase (TRAP), and immunofluorescent staining were conducted on osteoclasts to confirm the mechanisms of ASP on osteoclastogenesis. The results show that ASP could lead to attenuation of alveolar bone resorption in peri-implantitis by inhibiting osteoclast formation and decreasing pro-inflammatory cytokine levels in vivo. Furthermore, ASP could inhibit osteoclastogenesis by downregulating expression levels of transcription factors nuclear factor of activated T-cell (NFATc1) via restraining the activations of nuclear factor kappa beta (NF-κB) and the phosphorylation of extracellular signal-related kinase 1/2 (ERK1/2). In conclusion, ASP could significantly attenuate bone resorption in peri-implantitis via inhibition of osteoclastogenesis by suppressing NF-κB and ERK1/2 signaling pathways activations.

OPG is associated with thyroid nodule development in type 2 diabetes

Background

Thyroid nodule prevalence is increasing lately, especially in diabetes, but the mechanism of which is not clear. In this study, we investigated if osteoprotegerin (OPG) is involved in the pathogenesis of thyroid nodules in diabetes.

Methods

A total of 7568 individuals with detailed information and ultrasound examination results were studied for the prevalence of thyroid nodules. Among them, 1883 were with type 2 diabetes and 5685 were non‐diabetic. Then, 1120 individuals were randomly selected for the measurement of OPG. Diabetic rats were made by feeding a high‐fat‐high‐fructose diet for 28 weeks. Rats fed with a normal diet were as controls. Fresh thyroid tissues were obtained and fixed, dehydrated, and embedded in paraffin for hematoxylin‐eosin staining and observing pathological changes. qPCR and western blot were used to detect OPG expression in rat thyroid tissues.

Results

We found that HbA1c is an independent risk factor for thyroid nodules (Exp [β] = 1.158, p < 0.001). The prevalence of thyroid nodules in type 2 diabetes was higher than that in non‐diabetes (53.9% vs. 46.7%, p < 0.001). Serum OPG levels were significantly elevated in the diabetes group than in the non‐diabetes group (3160.17 pg/ml vs. 2819.39 pg/ml, p < 0.01). The expression of OPG increased significantly in the thyroid tissues of diabetic rats.

Conclusion

Osteoprotegerin may be associated with thyroid nodule development in diabetes.

Mycobacterium tuberculosis Induced Osteoblast Dysregulation Involved in Bone Destruction in Spinal Tuberculosis

Disturbance of bone homeostasis caused by Mycobacterium tuberculosis (Mtb) is a key clinical manifestation in spinal tuberculosis (TB). However, the complete mechanism of this process has not been established, and an effective treatment target does not exist. Increasing evidence shows that abnormal osteoclastogenesis triggered by an imbalance of the receptor activator of NF-κB ligand (RANKL)/osteoprotegerin (OPG) axis may play a key role in the disturbance of bone homeostasis. Previous studies reported that RANKL is strongly activated in patients with spinal TB; however, the OPG levels in these patients were not investigated in previous studies. In this study, we investigated the OPG levels in patients with spinal TB and the dysregulation of osteoblasts caused by Mtb infection. Inhibition of the Mce4a gene of Mtb by an antisense locked nucleic acid (LNA) gapmer (Mce4a-ASO) was also investigated. Analysis of the serum OPG levels in clinical samples showed that the OPG levels were significantly decreased in patients with spinal TB compared to those in the group of non-TB patients. The internalization of Mtb in osteoblasts, the known major source of OPG, was investigated using the green fluorescent protein (GFP)-labeled Mycobacterium strain H37Ra (H37RaGFP). The cell-associated fluorescence measurements showed that Mtb can efficiently enter osteoblast cells. In addition, Mtb infection caused a dose-dependent increase of the CD40 mRNA expression and cytokine (interleukin 6, IL-6) secretion in osteoblast cells. Ligation of CD40 by soluble CD154 reversed the increased secretion of IL-6. This means that the induced CD40 is functional. Considering that the interaction between CD154-expressing T lymphocytes and bone-forming osteoblast cells plays a pivotal role in bone homeostasis, the CD40 molecule might be a strong candidate for mediating the target for treatment of bone destruction in spinal TB. Additionally, we also found that Mce4a-ASO could dose-dependently inhibit the Mce4a gene of Mtb and reverse the decreased secretion of IL-6 and the impaired secretion of OPG caused by Mtb infection of osteoblast cells. Taken together, the current finding provides breakthrough ideas for the development of therapeutic agents for spinal TB.

The Role of Cannabinoids in Bone Metabolism: A New Perspective for Bone Disorders

Novel interest has arisen in recent years regarding bone, which is a very complex and dynamic tissue deputed to several functions ranging from mechanical and protective support to hematopoiesis and calcium homeostasis maintenance. In order to address these tasks, a very refined, continuous remodeling process needs to occur involving the coordinated action of different types of bone cells: osteoblasts (OBs), which have the capacity to produce newly formed bone, and osteoclasts (OCs), which can remove old bone. Bone remodeling is a highly regulated process that requires many hormones and messenger molecules, both at the systemic and the local level. The whole picture is still not fully understood, and the role of novel actors, such as the components of the endocannabinoids system (ECS), including endogenous cannabinoid ligands (ECs), cannabinoid receptors (CBRs), and the enzymes responsible for endogenous ligand synthesis and breakdown, is extremely intriguing. This article reviews the connection between the ECS and skeletal health, supporting the potential use of cannabinoid receptor ligands for the treatment of bone diseases associated with accelerated osteoclastic bone resorption, including osteoporosis and bone metastasis.

12-Deoxyphorbol 13-acetate inhibits RANKL-induced osteoclastogenesis via the attenuation of MAPK signaling and NFATc1 activation

Osteoporosis, characterized by bone loss and microstructure damage, occurs when osteoclast activity outstrips osteoblast activity. Natural compounds with inhibitory effect on osteoclast differentiation and function have been evidenced to protect from osteoporosis. After multiple compounds screening, 12-deoxyphorbol 13-acetate (DPA) was found to decline RANKL-induced osteoclastogenesis dose-dependently by attenuating activities of NFATc1 and c-Fos, followed by decreasing the level of osteoclast function-associated genes and proteins including Acp5, V-ATPase-d2 and CTSK. Mechanistically, we found that DPA suppressing RANKL-induced downstream signaling pathways, including MAPK signaling pathway and calcium oscillations. Furthermore, the in vivo efficacy of DPA was further confirmed in an OVX-induced osteoporosis mice model. Collectively, the results in our presentation reveal that DPA might be a promising compound to manage osteoporosis.

Investigation of anticancer activities of STA-9090 (ganetespib) as a second generation HSP90 inhibitor in Saos-2 osteosarcoma cells

Osteosarcoma is common childhood tumour type of the bone. Chemotherapy is the most important step in treatment of osteosarcoma. Despite advanced diagnosis methods and target specific cancer therapeutics, osteosarcoma has still a high mortality rate and a tendency to metastasize. Therefore, new therapeutic strategies are evaluated in osteosarcoma treatment in pre-clinical and clinical studies. In the last ten years, heat shock protein 90 (HSP90) has been important biological target to design target specific cancer drugs. HSP90 play vital roles in proper folding, stabilization and maintenance of oncogenic client proteins in tumorigenesis. Therefore, inhibition of HSP90 has been significant therapeutic aspects in cancer drug design. STA-9090 (ganetespib) is a second generation small molecule HSP90 inhibitor which blocks tumurogenesis in cancer cells. STA-9090 inhibited ATP hydrolysis and protein folding process of HSP90. In this study, STA-9090 decreased Saos-2 cell proliferation and IC₅₀ dose of STA-9090 was found out as 18.71 µM and 10.25 µM at 24 h and 48 h, respectively. STA-9090 inhibited HSP90 ATPase function and disrupted oncogenic client protein folding activity. Also, STA-9090 decreased protein level of the HSP90 in osteosarcoma cells. Expression analysis of osteosarcoma and bone metabolism related genes was performed by RT² Profiler PCR Array. This study has found the down-regulation of the expression levels of oncogenic genes: DKK1, TWIST1, WNT10B, WNT3A, RANK, RANKL, PTH, FGFR1, FGFR2, LTBP2, IL6, TGFβ1, MMP2 and SPARC genes, in STA-9090 treated Saso-2 cells. Furthermore, expression levels of osteosarcoma related genes, OPG, ERα, ERβ, IL15, BMP2 and BMP7, were found to have increased significantly. Biological activities of STA-9090 on Saos-2 cell line show its potential as a target specific drug to inhibit osteosarcoma and its metastasis.

Various pathways of zoledronic acid against osteoclasts and bone cancer metastasis: a brief review

Zoledronic acid (ZA) is one of the most important and effective class of anti-resorptive drug available among bisphosphonate (BP), which could effectively reduce the risk of skeletal-related events, and lead to a treatment paradigm for patients with skeletal involvement from advanced cancers. However, the exact molecular mechanisms of its anticancer effects have only recently been identified. In this review, we elaborate the detail mechanisms of ZA through inhibiting osteoclasts and cancer cells, which include the inhibition of differentiation of osteoclasts via suppressing receptor activator of nuclear factor κB ligand (RANKL)/receptor activator of nuclear factor κB (RANK) pathway, non-canonical Wnt/Ca2+/calmodulin dependent protein kinase II (CaMKII) pathway, and preventing of macrophage differentiation into osteoclasts, in addition, induction of apoptosis of osteoclasts through inhibiting farnesyl pyrophosphate synthase (FPPS)-mediated mevalonate pathway, and activation of reactive oxygen species (ROS)-induced pathway. Furthermore, ZA also inhibits cancer cells proliferation, viability, motility, invasion and angiogenesis; induces cancer cell apoptosis; reverts chemoresistance and stimulates immune response; and acts in synergy with other anti-cancer drugs. In addition, some new ways for delivering ZA against cancer is introduced. We hope this review will provide more information in support of future studies of ZA in the treatment of cancers and bone cancer metastasis.

Lactobacillus Plantarum HFY15 Helps Prevent Retinoic Acid-Induced Secondary Osteoporosis in Wistar Rats

A rat model of secondary osteoporosis was constructed using retinoic acid as an inducer, and the genes, proteins, and bone mass of the rats were analyzed. qPCR detection of the Wnt/β-catenin and OPG/RANK/RANKL signaling pathway-related gene expression levels showed that Lactobacillus plantarum HFY15 played a positive role in regulating both pathways. HFY15 significantly increased β-catenin, Lrp5, Lrp6, Wnt10b, OPG, RANKL, and Runx2 expression and downregulated DKK1, RANK, CTSK, TRACP, and ALP expression. Enzyme-linked immunosorbent assays further confirmed the qPCR results. Tartrate-resistant acid phosphatase staining showed that HFY15 slowed retinoic acid-induced osteoclast formation. Microcomputed tomography showed that HFY15 reduced trabecular separation and increased the percent bone volume, trabecular numbers, trabecular thickness, and bone mineral density in the rats in vivo. These findings indicate that HFY15 may help prevent retinoic acid-induced secondary osteoporosis in vivo.

Shikonin relieves osteoporosis of ovariectomized mice by inhibiting RANKL-induced NF-κB and NFAT pathways

Postmenopausal osteoporosis is very common in women. Currently, many kinds of new drugs are being developed for this disease. Postmenopausal osteoporosis is closely related to overactivity of osteoclasts in body. Shikonin is purple red naphthoquinone pigment extracted from lithospermum, which has anti-inflammation, antivirus, anticancer and other bioactivities. At the same time, it has been proved that shikonin can promote the proliferation and differentiation of osteoblasts, but its influence on osteoclasts and molecular mechanism are unknown. Our study showed that shikonin could inhibit the activity and formation of RANKL-mediated osteoclasts depending on dose without affecting the activity of bone marrow macrophages (BMM). In addition, we have also found that shikonin can inhibit the expression of specific marker gene of osteoclasts, including nuclear factor of activated T cells cytoplasmic 1 (NFATc1), cathepsin K (Ctsk), tartrate resistant acid phosphatase (TRAcP) and calcitonin receptor. Shikonin also could promote the proliferation of MC3T3-E1, increasing the expression of mRNA related to osteogenesis, like the expression of bone morphogenetic protein-2 (BMP-2), alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2) and osteocalcin (OCN). Luciferase reporter gene assay and Western blot analysis further indicated that shikonin could inhibit the activity of RANKL-induced NF-κB and NFAT receptors. Moreover, shikonin can also slow down bone loss of ovariectomized (OVX) mice by inhibiting the activity of osteoclasts. This work explains the molecular mechanism of shikonin in RANKL-mediated formation of osteoclasts, and reveals the potential of further developing shikonin into a new drug for prevention and treatment of postmenopausal osteoporosis.

Hederagenin protects mice against ovariectomy-induced bone loss by inhibiting RANKL-induced osteoclastogenesis and bone resorption

AIMS

Postmenopausal osteoporosis and other osteolytic bone diseases are often caused by the elevation in osteoclastogenesis and/or increased osteoclastic bone resorption, leading to excessive bone loss. Hederagenin (Hed) is a pentacyclic triterpenoid saponin extracted from various natural medicinal plants and exhibits numerous biological activities and may offer benefits against bone-related conditions. We evaluated the effects of Hed on osteoclast formation and bone resorption in vitro and the in vivo therapeutic benefits in the mouse model of ovariectomy (OVX)-induced bone loss.

MAIN METHODS

In vitro, osteoclast formation were determined by TRAcp staining; bone resorption were examined using Hydroxyapatite resorption assay and Podosomal actin belt formation assay; Related molecular mechanisms were determined by western blot assay. Construction of OVX mice by bilateral oophorectomy to simulate bone loss in vivo.

KEY FINDINGS

In vitro cellular assays showed that Hed inhibited RANKL-induced osteoclast formation and osteoclast bone (hydroxyapatite) resorption as well as marker gene expression from BMM culture. Mechanistically, Hed attenuated RANKL-induced intracellular reactive oxygen species (ROS) production, and MAPK signaling pathway (ERK and p38) activation which curbed the downstream induction of c-Fos and NFATc1. Consistent with the in vitro findings, Hed administration effectively protected OVX mice from bone loss by reducing osteoclast number and activity on bone surface.

SIGNIFICANCE

Our data provided promising evidence for the potential use of Hederagenin in the treatment of osteoclast-mediated osteolytic bone diseases such as postmenopausal osteoporosis.

Asiatic Acid Inhibits OVX-Induced Osteoporosis and Osteoclastogenesis Via Regulating RANKL-Mediated NF-κb and Nfatc1 Signaling Pathways

Asiatic acid is a triterpenoid compound extracted from a medicinal plant Centella asiatica. It has been used as a highly efficient compound for the treatment of cancer and hyperlipidemia, as well as possessing potential antiinflammatory properties. However, its effects on bone metabolism and osteoporosis haven't been reported. The purpose of our research were to reveal the biomolecular effects of asiatic acid on osteoclasts, and its underlying molecular mechanisms regulating its effects on receptor activator of NF-κB ligand (RANKL)-induced signaling pathways. We found that asiatic acid inhibited multinucleated tartrate-resistant acid phosphatase (TRAcP)-positive osteoclast differentiation and osteoclast induced bone loss. Real time PCR showed that asiatic acid reduced the expression of down-cascade target genes including Ctsk, Nfatc1, Calcr, and Atp6v0d2. Western blot and luciferase reporter gene assays revealed that asiatic acid inhibits RANKL mediated NF-κB and NFATc1 signalings. Further, in vivo study demonstrated asiatic acid attenuates estrogen deficiency-induced bone loss in ovariectomized mice. MicroCT and histology analyses revealed that osteoclast numbers were significantly suppressed in asiatic acid treated groups. Furthermore, serum levels of TRAcP and CTX-1 were downregulated in treated groups. Taken together, our data show that asiatic acid can inhibit osteoclastic formation and reduce OVX-induced bone resorption through RANKL-activated NF-κB or NFATc1 signaling, suggesting that asiatic acid may be a potential and effective natural compound for the therapy of excessive RANKL-related osteolytic diseases.

Diosmetin inhibits osteoclast formation and differentiation and prevents LPS-induced osteolysis in mice

Osteolytic bone diseases are closely linked to the over-activation of osteoclasts and enhancement of bone resorption. It has become a major health issue in orthopedic practice worldwide. Inhibition of osteoclasts is proposed to be the main treatment for osteolytic disorders. Diosmetin (DIO) is a natural flavonoid with properties of antioxidant, anti-infection, and antishock. The effect of DIO on osteoclast differentiation is poorly understood. In this study project, we found that DIO could inhibit osteoclastic formation induced by receptor activator of nuclear factor kappa-B ligand (RANKL) in a dose-dependent manner. The expression of the osteoclast differentiation marker genes, cathepsin K, nuclear factor of activated T-cells 1 (NFATc1), Acp5, Ctr, Atp6v0d2, and Mmp9 were also decreased by the treatment of DIO. In addition, DIO attenuated the formation of actin ring and the ability of bone resorption. Further, the western blotting showed that DIO inhibits the phosphorylation of the mitogen-activated protein kinases signaling pathway induced by RANKL, accompanied by the downregulation of NFATc1 and c-Fos expression. We also found that DIO could reduce the accumulation of reactive oxygen species (ROS) induced by RANKL. In vivo, the study revealed that DIO can significantly reduce LPS-induced osteolysis in mice. Collectively, our study shows that DIO can inhibit osteoclast formation and activation, and could serve as a potential therapeutic drug for osteolytic bone diseases.

Daphnetin attenuates LPS-induced osteolysis and RANKL mediated osteoclastogenesis through suppression of ERK and NFATc1 pathways

Aseptic prosthetic loosening and periprosthetic infection resulting in inflammatory osteolysis is a leading complication of total joint arthroplasty (TJA). Excessive bone destruction around the bone and prosthesis interface plays a key role in the loosening prostheses leading to revision surgery. The bacterial endotoxins or implant-derived wear particles-induced inflammatory response is the major cause of the elevated osteoclast formation and activity. Thus, agents or compounds that can attenuate the inflammatory response and/or inhibit the elevated osteoclastogenesis and excessive bone resorption would provide a promising therapeutic avenue to prevent aseptic prosthetic loosening in TJA. Daphnetin (DAP), a natural coumarin derivative, is clinically used in Traditional Chinese Medicine for the treatment of rheumatoid arthritis due to its anti-inflammatory properties. In this study, we report for the first time that DAP could protect against lipopolysaccharide-induced inflammatory bone destruction in a murine calvarial osteolysis model in vivo. This protective effect of DAP can in part be attributed to its direct inhibitory effect on RANKL-induced osteoclast differentiation, fusion, and bone resorption in vitro. Biochemical analysis found that DAP inhibited the activation of the ERK and NFATc1 signaling cascades. Collectively, our findings suggest that DAP as a natural compound has potential for the treatment of inflammatory osteolysis.

Rhoifolin ameliorates titanium particle-stimulated osteolysis and attenuates osteoclastogenesis via RANKL-induced NF-κB and MAPK pathways

Prosthesis loosening is a highly troublesome clinical problem following total joint arthroplasty. Wear-particle-induced osteoclastogenesis has been shown to be the primary cause of periprosthetic osteolysis that eventually leads to aseptic prosthesis loosening. Therefore, inhibiting osteoclastogenesis is a promising strategy to control periprosthetic osteolysis. The possible mechanism of action of rhoifolin on osteoclastogenesis and titanium particle-induced calvarial osteolysis was examined in this study. The in vitro study showed that rhoifolin could strongly suppress the receptor activators of nuclear factor-κB (NF-κB) ligand-stimulated osteoclastogenesis, hydroxyapatite resorption, F-actin formation, and the gene expression of osteoclast-related genes. Western blot analysis illustrated that rhoifolin could attenuate the NF-κB and mitogen-activated protein kinase pathways, and the expression of transcriptional factors nuclear factor of activated T cells 1 (NFATc1) and c-Fos. Further studies indicated that rhoifolin inhibited p65 translocation to the nucleus and the activity of NFATc1 and NF-κB rhoifolin could decrease the number of tartrate-resistant acid phosphate-positive osteoclasts and titanium particle-induced C57 mouse calvarial bone loss in vivo. In conclusion, our results suggest that rhoifolin can ameliorate the osteoclasts-stimulated osteolysis, and may be a potential agent for the treatment of prosthesis loosening.

New challenges in integrated diagnosis by imaging and osteo-immunology in bone lesions

INTRODUCTION

High-resolution imaging is the gold standard to measure the functional and biological features of bone lesions. Imaging markers have allowed the characterization both of tumour heterogeneity and metabolic data. Besides, ongoing studies are evaluating a combined use of 'imaging markers', such as SUVs, MATV, TLG, ADC from PET and MRI techniques respectively, and several 'biomarkers' spanning from chemokine immune-modulators, such as PD-1, RANK/RANKL, CXCR4/CXCL12 to transcription factors, such as TP53, RB1, MDM2, RUNX family, EZH2, YY1, MAD2. Osteoimmunology may improve diagnosis and prognosis leading to precision medicine in bone lesion treatment. Areas covered: We investigated modalities (molecular and imaging approach) useful to identify bone lesions deriving both from primary bone tumours and from osteotropic tumours, which have a higher incidence, prevalence and prognosis. Here, we summarized the recent advances in imaging techniques and osteoimmunology biomarkers which could play a pivotal role in personalized treatment. Expert commentary: Although imaging and molecular integration could allow both early diagnosis and stratification of cancer prognosis, large scale clinical trials will be necessary to translate pilot studies in the current clinical setting.

ABBREVIATIONS

ADC: apparent diffusion coefficient; ALCAM: Activated Leukocyte Cell Adhesion Molecule; ALP: Alkaline phosphatases; BC: Breast cancer; BSAP: B-Cell Lineage Specific Activator; BSAP: bone-specific alkaline phosphatase; BSP: bone sialoprotein; CRIP1: cysteine-rich intestinal protein 1; CD44: cluster of differentiation 44; CT: computed tomography; CXCL12: C-X-C motif ligand 12; CXCR4: C-X-C C-X-C chemokine receptor type 4; CTLA-4: Cytotoxic T-lymphocyte antigen 4; CTX-1: C-terminal end of the telopeptide of type I collagen; DC: dendritic cell; DWI: Diffusion-weighted MR image; EMT: mesenchymal transition; ET-1: endothelin-1; FDA: Food and Drug Administration; FDG: ¹⁸F-2-fluoro-2-deoxy-D-glucose; FGF: fibroblast growth factor; FOXC2: forkhead box protein C2: HK-2: hexokinase-2; ICTP: carboxyterminal cross-linked telopeptide of type I collagen; IGF-1R: Insulin Like Growth Factor 1 Receptor; ILC: innate lymphocytes cells; LC: lung cancer; IL-1: interleukin-1; LYVE1: lymphatic vessel endothelial hyaluronic acid receptor 1; MAD2: mitotic arrest deficient 2; MATV: metabolically active tumour volume; M-CSF: macrophage colony stimulating factor; MM: multiple myeloma; MIP1a: macrophage inflammatory protein 1a; MSC: mesenchymal stem cell; MRI: magnetic resonance imaging; PC: prostate cancer; NRP2: neuropilin 2; OPG: osteoprotogerin; PDGF: platelet-derived growth factor; PD-1: Programmed Cell Death 1; PET: positron emission tomography; PINP: procollagen type I N propeptide; PROX1: prospero homeobox protein 1; PSA: Prostate-specific antigen; PTH: parathyroid hormone; RANK: Receptor activator of NF-kB ligand; RECK: Reversion-inducing-cysteine-rich protein; SEMAs: semaphorins; SPECT: single photon computed tomography; SUV: standard uptake value; TLG: total lesion glycolysis; TP53: tumour protein 53; VCAM-1: vascular endothelial molecule-1; VOI: volume of interest; YY1: Yin Yang 1.

Optimized Extract from Corylopsis coreana Uyeki (Hamamelidaceae) Flos Inhibits Osteoclast Differentiation

Osteoporosis is a metabolic disorder that decreases the stability against fractures of the spine, femur, and radius by weakening the strength and integrity of bones. Receptor activator of nuclear factor-kappa B ligand signaling ultimately activated nuclear factor-activated T cells c1, a major transcription factor for osteoclast formation. This study researched the effects of Corylopsis coreana (C. coreana) Uyeki flos extracts on the antiosteoclastic potential of macrophages and the phytochemicals contained therein. The alcoholic extract of C. coreana Uyeki flos inhibited the differentiation of osteoclast. We carried out the experiments of the pattern of differentiation of osteoclasts based on the alcoholic percentage of extracts. Among them, 80% alcoholic extract showed the highest inhibitory effect. The alcoholic extract was composed of phytochemicals such as bergenin, quercetin, and quercitrin. This extract inhibited not only mRNA expression levels of NFATc1, osteoclast-associated receptor (OSCAR), cathepsin K, and tartrate-resistant acid phosphatase (TRAP), but also the translational expression of NFATc1. The inhibitory effect for osteoclast differentiation of the alcoholic extract was confirmed using the resorption pit assay. This is the first scientific report of the antiosteoclastic effects of C. coreana Uyeki flos extract, which can be applied therapeutically for the treatment of osteoporosis.

Potential Role of L-Arginine and Vitamin E Against Bone Loss Induced by Nano-Zinc Oxide in Rats

The purpose of this study was to illustrate the effects of zinc oxide nanoparticles (ZnO-NPs) administration on bone turnover and bone resorbing agents in rats and how L-arginine (L-arg) or vitamin E (vit E) co-administrations might affect them. Fasting rats were randomly divided into four groups (n = 10): G1-normal healthy animals; G2-ZnO-NPs-exposed rats (600 mg/kg^-1/day^-1); G3-ZnO-NPs-exposed rats co-administrated L-arg (200 mg/kg^-1/day^-1); G4-ZnO-NPs-exposed rats co-administrated vit E (200 mg/kg^-1/day^-1). The ingredients were orally administered daily. The body weight and food consumption of rats were recorded during the administration period and the experiment continued for three consecutive weeks. The results demonstrated that ZnO-NPs administration induced bone loss in rats as manifested by reduced activity of bone alkaline phosphatase (B-ALP) and increased level of C-terminal peptide type I collagen (CTx). The increase of inflammatory markers, tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) by ZnO-NPs suggests that deleterious effects of ZnO-NPs on bone turnover were, in part, due to inflammation. Confirming to this suggestion, both L-arg and vit E reduced TNF-α and IL-6 levels and consequently decreased bone resorption as indicated by reduced serum CTx level. This study proved that ZnO-NPs can induce bone turnover, which may be reduced by L-arg or vit.E co-administration, partly by anti-inflammatory mechanism.

Role of RANK and Akt1 activation in human osteosarcoma progression: A clinicopathological study

The receptor activator of nuclear factor κB (RANK) axis is the fundamental signaling pathway in bone formation as well as bone tumor pathophysiology. The aim of the present study was to evaluate the impact of the expression of RANK and its downstream signaling molecule Akt1 on tumor progression in patients with osteosarcoma. Expression of RANK and Akt1 was examined in 78 human osteosarcoma samples by immunohistochemistry using formalin-fixed samples. Following this, each graded immunohistochemistry result was correlated with clinicopathological parameters and patient survival. In total, 60 osteosarcomas (76.9%) expressed RANK and 58 cases (74.4%) showed expression of Akt1. In addition, expression of RANK was negatively correlated with disease-free survival by Kaplan-Meier analysis. A resistance was observed to chemotherapy in RANK-expressing cases, which was statistically significant (P<0.05). In addition, chemotherapy and staging of the tumor were found to independent factors that have an effect on patient survival (P<0.05). Thus, RANK was identified as a negative prognostic factor of osteosarcoma survival.

Germline genetic predictors of aromatase inhibitor concentrations, estrogen suppression and drug efficacy and toxicity in breast cancer patients

The third-generation aromatase inhibitors (AIs), anastrozole, letrozole and exemestane, are highly effective for the treatment of estrogen receptor-positive breast cancer in postmenopausal women. AIs inhibit the aromatase (CYP19A1)-mediated production of estrogens. Most patients taking AIs achieve undetectable blood estrogen concentrations resulting in drug efficacy with tolerable side effects. However, some patients have suboptimal outcomes, which may be due, in part, to inherited germline genetic variants. This review summarizes published germline genetic associations with AI treatment outcomes including systemic AI concentrations, estrogenic response to AIs, AI treatment efficacy and AI treatment toxicities. Significant associations are highlighted with commentary about prioritization for future validation to identify pharmacogenetic predictors of AI treatment outcomes that can be used to inform personalized treatment decisions in patients with estrogen receptor-positive breast cancer.

Bajijiasu Abrogates Osteoclast Differentiation via the Suppression of RANKL Signaling Pathways through NF-κB and NFAT

Pathological osteolysis is commonly associated with osteoporosis, bone tumors, osteonecrosis, and chronic inflammation. It involves excessive resorption of bone matrix by activated osteoclasts. Suppressing receptor activator of NF-κB ligand (RANKL) signaling pathways has been proposed to be a good target for inhibiting osteoclast differentiation and bone resorption. Bajijiasu—a natural compound derived from Morinda officinalis F. C. How—has previously been shown to have anti-oxidative stress property; however, its effect and molecular mechanism of action on osteoclastogenesis and bone resorption remains unclear. In the present study, we found that Bajijiasu dose-dependently inhibited RANKL-induced osteoclast formation and bone resorption from 0.1 mM, and reached half maximal inhibitory effects (IC₅₀) at 0.4 mM without toxicity. Expression of RANKL-induced osteoclast specific marker genes including cathepsin K (Ctsk), nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), tartrate resistant acid phosphatase (TRAcP), vacuolar-type H⁺-ATPase V0 subunit D2 (V-ATPase d2), and (matrix metalloproteinase-2 (MMP2) was inhibited by Bajijiasu treatment. Luciferase reporter gene studies showed that Bajijiasu could significantly reduce the expression and transcriptional activity of NFAT as well as RANKL-induced NF-κB activation in a dose-dependent manner. Further, Bajijiasu was found to decrease the RANKL-induced phosphorylation of extracellular signal-regulated kinases (ERK), inhibitor of κB-α (IκB-α), NFAT, and V-ATPase d2. Taken together, this study revealed Bajijiasu could attenuate osteoclast formation and bone resorption by mediating RANKL signaling pathways, indicative of a potential effect of Bajijiasu on osteolytic bone diseases.

Association of Genes Variants in RANKL/RANK/OPG Signaling Pathway with the Development of Osteonecrosis of the Femoral Head in Chinese Population

The RANKL/RANK/OPG pathway plays an important role in regulating bone remodeling and bone turnover. However, the association of the genes variants with the risk of ONFH has rarely been reported. Here, we analyzed the correlation of the 10 SNPs polymorphisms of RANKL, RANK, OPG, TRAF6, and NFATC1 genes with the risk and development of ONFH in 200 ONFH patients and 177 health controls of Chinese population with using Mass ARRAY® platform. The results showed that the recessive model of NFATC1rs9518 was significantly associated with increased ONFH risk (OR:8.223, P=0.048); the proportion of stage Ⅳ patients in the rs9518TC genotype carriers was statistically higher than that of stage Ⅲ patients (P=0.03); in the T-C haplotype carriers of Naftac1, the proportion of bilateral hips lesions was also significantly enhanced than that of unilateral hip lesions(P=0.05). In addition, the proportion of idiopathic ONFH in the TT genotype carriers of OPGrs2073617 was significantly higher than that of steroid or alcohol-induced ONFH, respectively, while in the TC genotype carriers of the SNP, the proportion of idiopathic ONFH remarkably decreased compared with that of Alcohol-induced ONFH, P=0.021. Our results were first found that NFATC1rs9518 closely associated with the risk and the development of ONFH, while OPGrs2073617 statistically correlated with the etiological classification of ONFH.

Inhibition of BET proteins and epigenetic signaling as a potential treatment for osteoporosis

Histone modifications are important for maintaining the transcription program. BET proteins, an important class of "histone reading proteins", have recently been described as essential in bone biology. This study presents the therapeutic opportunity of BET protein inhibition in osteoporosis. We find that the pharmacological BET protein inhibitor JQ1 rescues pathologic bone loss in a post-ovariectomy osteoporosis model by increasing the trabecular bone volume and restoring mechanical properties. The BET protein inhibition suppresses osteoclast differentiation and activity as well as the osteoblastogenesis in vitro. Moreover, we show that treated non-resorbing osteoclasts could still activate osteoblast differentiation. In addition, specific inhibition of BRD4 using RNA interference inhibits osteoclast differentiation but strongly activates osteoblast mineralization activity. Mechanistically, JQ1 inhibits expression of the master osteoclast transcription factor NFATc1 and the transcription factor of osteoblast Runx2. These findings strongly support that targeting epigenetic chromatin regulators such as BET proteins may offer a promising alternative for the treatment of bone-related disorders such as osteoporosis.

The implications of genetic variation for the pharmacokinetics and pharmacodynamics of aromatase inhibitors

INTRODUCTION

Breast cancer is the most common female cancer and remains a serious public health concern worldwide. Third-generation aromatase inhibitors (AIs) are widely used in postmenopausal women with estrogen receptor positive breast cancer. However, there is marked interindividual variability in terms of the efficacy and incidence of adverse events following treatment with AIs. Pharmacogenetics has the potential to predict clinical outcomes based on patients' genetic information, paving the way towards personalized treatment.

AREAS COVERED

This article reviews pharmacogenetic studies of AIs, including pharmacokinetic and pharmacodynamic aspects, highlighting those studies where the efficacy and adverse events of AIs have been examined using both candidate gene and genome-wide approaches.

EXPERT OPINION

Pharmacogenetics is a promising approach to develop personalized medicine with AIs. However, the application of pharmacogenetics to predict therapeutic efficacy and adverse events in breast cancer patients is still far from implementation in routine clinical practice. Large, comprehensive, multicenter studies that simultaneously evaluate multiple genes and pathways, including rare variants, are warranted in order to produce reliable and informative results. The ultimate aim is to develop clinically-relevant guidelines for breast cancer therapy.

Association Between Osteoprotegerin Gene Polymorphisms and Rheumatoid Arthritis Susceptibility: A Meta-analysis

BACKGROUND AND AIMS

We undertook this study to assess the association between osteoprotegerin (OPG) gene polymorphisms and rheumatoid arthritis (RA) susceptibility.

METHODS

English language databases of PubMed Medline and OVID EMBASE and Chinese databases of China National Knowledge Infrastructure, Chinese Biomedical Literature Database and Wanfang were searched to identify case-control studies studied the relationship between OPG gene polymorphisms and RA susceptibility. Two reviewers separately and repeatedly screened searched studies according to study selection criteria and collected data. Data analyses of five comparison models-allelic model, heterozygote model, homozygote model, dominant model and recessive model-were conducted in Review Manager Software 5.1.

RESULTS

A total of five studies including 1713 RA cases and 1845 controls were eligible in this meta-analysis. Single nucleotide polymorphisms (SNPs), rs3102735 T/C or A/G, rs2073618 G/C and rs3134069 T/G, of OPG gene were studied. Data from five studies of SNPs rs3102735 were OR = 1.22, 95% CI 0.86-1.73, OR = 1.06, 95% CI 0.86-1.32, OR = 1.79, 95% CI 0.65-4.89, OR = 1.16, 95% CI 0.85-1.59, OR = 1.73, 95% CI 0.67-4.46, respectively, for the five comparison models in order. For SNPs rs2073618, results derived from three studies were OR = 1.06, 95% CI 0.95-1.19, OR = 1.11, 95% CI 0.94-1.31, OR = 1.09, 95% CI 0.84-1.42, OR = 1.10, 95% CI 0.94-1.30, OR = 1.04, 95% CI 0.84-1.30, respectively. With respect to SNPs rs3134069, only one study assessed the associations, reporting no statistically significant results among the five comparison models.

CONCLUSION

SNPs rs3102735, rs2073618 and rs3134069 of OPG gene polymorphisms are not susceptibility factors of RA based on currently available evidence.

Eriodictyol Inhibits RANKL-Induced Osteoclast Formation and Function Via Inhibition of NFATc1 Activity

Receptor activator of nuclear factor kappa-B ligand (RANKL) induces differentiation and function of osteoclasts through triggering multiple signaling cascades, including NF-κB, MAPK, and Ca(2+) -dependent signals, which induce and activate critical transcription factor NFATc1. Targeting these signaling cascades may serve as an effective therapy against osteoclast-related diseases. Here, by screening a panel of natural plant extracts with known anti-inflammatory, anti-tumor, or anti-oxidant properties for possible anti-osteoclastogenic activities we identified Eriodictyol. This flavanone potently suppressed RANKL-induced osteoclastogenesis and bone resorption in a dose-dependent manner without detectable cytotoxicity, suppressing RANKL-induced NF-κB, MAPK, and Ca(2+) signaling pathways. Eriodictyol also strongly inhibited RANKL-induction of c-Fos levels (a critical component of AP-1 transcription factor required by osteoclasts) and subsequent activation of NFATc1, concomitant with reduced expression of osteoclast specific genes including cathepsin K (Ctsk), V-ATPase-d2 subunit, and tartrate resistant acid phosphatase (TRAcP/Acp5). Taken together, these data provide evidence that Eriodictyol could be useful for the prevention and treatment of osteolytic disorders associated with abnormally increased osteoclast formation and function. J. Cell. Physiol. 231: 1983-1993, 2016. © 2016 Wiley Periodicals, Inc.

Pathophysiology of Osteonecrosis of the Jaws

Osteonecrosis of the jaw (ONJ) is a multifactorial disease in patients with primary or metastatic bone malignancy or osteoporosis undergoing systemic antiresorptive therapy, where pathophysiology has not yet been fully determined. The staging of ONJ is based on severity of symptoms and extent of clinical and radiographic findings. Treatment strategies range from conservative local wound care to aggressive resective surgery of all necrotic bone. The first ONJ cases were reported in 2003 and 2004, and although significant progress has been made in our understanding of the disease, much more work needs to be done to completely explain its pathophysiology.

RANKL and OPG Polymorphisms Are Associated with Aromatase Inhibitor-Related Musculoskeletal Adverse Events in Chinese Han Breast Cancer Patients

Background

Breast cancer patients treated with aromatase inhibitors (AIs) may experience musculoskeletal adverse events (MS-AEs). Several studies have confirmed that the RANKL/RANK/OPG signaling pathway plays a dominant role in bone health. Therefore, this study aimed to analyze the relationship between the serum levels of RANKL, OPG and their SNPs (single nucleotide polymorphisms) with AI-related MS-AEs.

Methodology and Principal Findings

Patients with early stage, hormone-sensitive breast cancer who were receiving AI therapy were enrolled. We included 208 cases with AI-related MS-AEs and 212 without (controls). The levels of estradiol, bone-turnover markers, multiple inflammatory cytokines, RANKL,OPG and lumbar spine BMD were measured, and questionnaires were completed. We analyzed 29 SNPs of RANKL, RANK and OPG using Sequenom MassARRAY assays and PCR-based TaqMan assays. The levels of bone-turnover markers and RANKL and the ratio of RANKL/OPG were higher in patients with AI-related MS-AEs than controls (all p < 0.05). A genetic assay showed that the RANKL SNP rs7984870 and OPG SNP rs2073618 were associated with AI-related MS-AEs. In patients with AI-related MS-AEs, rs7984870 CC and rs2073618 CC were risk genotypes. Carriers of the rs7984870 CC genotype were more likely to have a higher RANKL level and RANKL/OPG ratio than carriers of the GG genotype, and carriers of the rs2073618 CC genotype were more likely to have a lower OPG level and a higher RANKL/OPG ratio than carriers of the GG genotype (all p < 0.05). Moreover, risk genotypes were associated with higher levels of serum CTX and PINP and a lower lumbar spine BMD (all p < 0.05).

Conclusions and Significance

In conclusion, the RANKL and OPG risk genotypes synergize to negatively impact bone health and predispose breast cancer patients to AI-related MS-AEs.

Crosstalk between bone niche and immune system: osteoimmunology signaling as a potential target for cancer treatment

There is a well recognized link between the bone and the immune system and in recent years there has been a major effort to elucidate the multiple functions of the molecules expressed in both bone and immune cells. Several molecules that were initially identified and studied in the immune system have been shown to have essential functions also in the bone. An interdisciplinary field embracing immune and bone biology has been brought together and called "osteoimmunology". The co-regulation of the skeletal and immune systems strikingly exemplifies the extreme complexity of such an interaction. Their interdependency must be considered in designing therapeutic approaches for either of the two systems. In other words, it is necessary to think of the osteoimmune system as a complex physiological unit. Denosumab was originally introduced to specifically target bone resorption, but it is now under evaluation for its effect on the long term immune response. Similarly, our current and still growing knowledge of the intimate link between the immune system and bone will be beneficial for the safety of drugs targeting either of these integrated systems. Given the large number of molecules exerting functions on both the skeletal and immune systems, osteoimmunological understanding is becoming increasingly important. Both bone and immune systems are frequently disrupted in cancer; and they may be crucial in regulating tumor growth and progression. Some therapies - such as bisphosphonates and receptor activator of NF-κB ligand (RANKL) targeted drugs - that aim at reducing pathologic osteolysis in cancer may interact with the immune system, thus providing potential favorable effects on survival.

Osteoprotegerin induces podosome disassembly in osteoclasts through calcium, ERK, and p38 MAPK signaling pathways

Osteoclasts are critical for bone resorption and use podosomes to attach to bone matrix. Osteoprotegerin (OPG) is a negative regulator of osteoclast function that can affect the formation and function of podosomes. However, the signaling pathways that link OPG to podosome function have not been well characterized. Therefore, this study examined the roles of intracellular calcium and MAPKs in OPG-induced podosome disassembly in osteoclasts. We assessed the effects of the intracellular calcium chelator Bapta-AM, ERK inhibitor U0126, and p38 inhibitor SB202190 on OPG-treated osteoclast differentiation, adhesion structures, intracellular free Ca(2+) concentration and the phosphorylation state of podosome associated proteins (Pyk2 and Src). Mouse monocytic RAW 264.7 cells were differentiated to osteoclasts using RANKL (30ng/mL) and M-CSF (25ng/mL). The cells were pretreated with Bapta-AM (5μM), U0126 (5μM), or SB202190 (10μM) for 30min, followed by 40ng/mL OPG for 3h. Osteoclastogenesis, adhesion structure, viability and morphology, intracellular free Ca(2+) concentration and the phosphorylation state of Pyk2 and Src were measured by TRAP staining, scanning electron microscopy, real-time cell analyzer, flow cytometry and western blotting, respectively. OPG significantly inhibited osteoclastogenesis, the formation of adhesion structures, and reduced the amount of phosphorylated Pyk2 and Src-pY527, but increased phosphorylation of Src-pY416. Bapta-AM, U0126, and SB202190 partially restored osteoclast differentiation and adhesion structures. Both Bapta-AM and U0126, but not SB202190, restored the levels of intracellular free Ca(2+) concentration, phosphorylated Pyk2 and Src-pY527. All three inhibitors blocked OPG-induced phosphorylation at Src-pY416. These results suggest OPG disrupts the attachment structures of osteoclasts and activates Src as an adaptor protein that competes for the reduced amount of phosphorylated Pyk2 through calcium- and ERK-dependent signaling pathways. p38 MAPK signaling may have a different role in OPG-induced osteoclast retraction. Our findings potentially offer novel insights into the signaling mechanisms downstream of OPG that affect osteoclast attachment to the extracellular matrix.

Recent advances in bone-targeted therapies of metastatic prostate cancer

Prostate cancer is one of the most common malignancies affecting men worldwide, with bone being the most common site of metastasis in patients that progress beyond organ confinement. Bone metastases are virtually incurable and result in significant disease morbidity and mortality. Bone provides a unique microenvironment whose local interactions with tumor cells offer novel targets for therapeutic interventions. Several attractive molecules or pathways have been identified as new potential therapeutic targets for bone metastases caused by metastatic castration-resistant prostate cancer. In this review, we present the recent advances in molecular targeted therapies for prostate cancer bone metastasis focusing on therapies that target the bone cells and the bone microenvironment. The therapies covered in this review include agents that inhibit bone resorption, agents that stimulate bone formation, and agents that target the bone matrix. Suggestions to devise more effective molecular targeted therapies are proposed. Hopefully, with better understanding of the biology of the disease and the development of more robust targeted therapies, the survival and quality of life of the affected individuals could be significantly improved.

A study of immunomodulatory genes responses to macrophages of Schistosoma japonicum infection during different stages by microarray analysis

Macrophages initiate, modulate, and also serve as final effector cells in immune responses during the course of schistosomal infections. In this study, we investigated the gene expression profile and functional changes of macrophages in immune responses against the Schistosoma japonicum by microarray analysis. Hierarchical clustering analysis demonstrated that a significant switch in gene transformation associated with a type-1 response and linked with a type-2 cytokine phenotype occurs between 4.5 and 8 weeks post-infection. Moreover, the gene profiles at 3 later time-points following egg challenge were similar in complexity and magnitude. The data also showed that there were mostly inhibition of gene expression related TLR, IFN, MHC and TNFrsf at the switch between 4.5 and 8 weeks post-infection, It is suggested that these immunomodulatory genes may be down-regulated in defense against S. japonicum eggs and granuloma pathology. The induction of alternatively activated macrophage (AAMϕ) was important for dampening the inflammation in hepatic granulomas and contributing to a decrease in cytotoxicity. The gene expressions involved in repair/remodeling during liver fibrosis were also observed after egg production. Understanding the immune mechanisms associated with parasitic resistance, pathology of parasite infection, and parasite growth will provide useful insight on host-schistosome interactions and for the control of schistosomiasis.

Effect of fluoride and low versus high levels of dietary calcium on mRNA expression of osteoprotegerin and osteoprotegerin ligand in the bone of rats

The ratio of osteoprotegerin ligand (OPGL) to osteoprotegerin (OPG) determines the delicate balance between bone resorption and synthesis. The main objective of the present study is to investigate the possible role of OPGL and OPG in the bone metabolism of rats exposed to fluoride and the protective or aggravating effect of calcium (Ca). In a 6-month study, 270 weanling male Sprague-Dawley rats weighing between 70 and 90 g were divided randomly into six groups of 45 rats in each group. Three groups (groups I, III, and V)served as controls and drank deionized water and were fed purified rodent diets containing either 1,000 mg Ca/kg (low Ca), 5,000 mg Ca/kg (normal Ca), or 20,000 mg Ca/kg (high Ca). The three experimental groups (groups II, IV, and VI) were given the same diets but they drank water containing 100 mg F ion/L (from NaF). Every 2 months 15 rats were randomly selected from each group and sacrificed for the study. The ratio of OPGL mRNA to OPG mRNA was significantly increased by the sixth month in the distal femur joints of the F-exposed rats. Serum tartrate-resistant acid phosphatase activity and serum calcitonin activity in the F-exposed groups was increased, although changes were not apparent in the serum alkaline phosphatase or Gla-containing proteins, especially in the low calcium and high calcium diet F-exposed groups. The results indicated that OPG and OPGL may play important roles in skeletal fluorosis, and that fluoride may enhance osteoclast formation and induce osteoclastic bone destruction. A high Ca diet did not play a protective role, but rather may aggravate the damage of fluoride.

HGFK1 inhibits bone metastasis in breast cancer through the TAK1/p38 MAPK signaling pathway

Breast cancer metastasis to bone represents a devastating complication of advanced breast cancer, frequently resulting in significant increases in morbidity and mortality. An understanding of the mechanisms that govern breast cancer metastasis at the molecular level should lead to more effective therapies. Recently, the kringle 1 domain of human hepatocyte growth factor (HGFK1) was identified as a candidate metastasis suppressor gene. Here, we investigated whether HGFK1 is a key regulator of breast cancer bone metastasis. Of the 193 human breast carcinoma tissue samples examined, HGFK1 expression was relative higher in 82 (42.4%) by western blot and in 84 (43.5%) by quantitative real-time PCR. The higher expression of HGFK1 was significantly associated with a better prognostic value (P<0.001) and inversely correlated with bone metastasis (P=0.003). The efficacy of adeno-associated virus carrying HGFK1 (AAV-HGFK1) in osteolytic bone metastasis was then evaluated using an in vivo bone metastasis model. AAV-HGFK1 significantly inhibited osteolytic bone metastasis and prolonged the survival of mice in this model (P<0.01). In vitro, HGFK1 expression resulted in significant anti-invasion effects, enhanced the phosphorylation of TAK1 (transforming growth factor-β-activated kinase 1), p38 MAPK (mitogen-activated protein kinase) and MAPKAPK2 (MAPK-activated protein kinase 2) and decreased the expression of receptor activator of nuclear factor-κB (RANK), which was abrogated by the p38 MAPK inhibitor SB203580. This study shows for the first time that HGFK1 significantly inhibits the metastasis of breast cancer to bone by activating the TAK1/p38 MAPK signaling pathway and inhibiting RANK expression. Thus, AAV-HGFK1 treatment represents a potential therapy for bone metastasis in breast cancer.

Bisphosphonates regulate cell proliferation, apoptosis and pro-osteoclastic expression in MG-63 human osteosarcoma cells

Bisphosphonates are well established in the management of cancer-induced skeletal complications. Recent studies suggest that nitrogen-containing bisphosphonates (N-BPs) promote the apoptosis of cancer cells as well as osteoclasts in bone metastatic sites. To investigate whether N-BPs exhibit a direct antitumor effect on osteoclasts, the current study investigated the effects of zoledronic acid (ZOL) on MG-63 cells in vitro. MG-63 cells were treated with ZOL. The inhibitory effect of ZOL on the growth of MG-63 cells was measured by MTT assay. ZOL-induced apoptosis of the MG-63 cells was examined by Hoechst 33258 staining, electron microscopy, Annexin V-FITC and propidium iodide staining. Reverse-transcription polymerase chain reaction (RT-PCR) and western blotting analysis were employed to assess the expression of osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL). The MTT assay showed that ZOL induced a distinct dose- and time-dependent reduction of cell viability with an IC(50) value of 52.37±1.0 μM for 72 h. Flow cytometric analysis further revealed that the cell apoptosis was induced by arrest of the cell cycle in the G(1) phase. RT-PCR and western blot analysis demonstrated that ZOL upregulated OPG expression. These results suggest that ZOL has direct effects on osteosarcoma cell growth and apoptosis. Increased OPG expression is an indirect effect, possibly via changes in the local microenvironment.

OPG inhibits gene expression of RANK and CAII in mouse osteoclast-like cell

This study was designed to determine the effects of the osteoprotegerin (OPG) on the mRNA expression of carbonic anhydrase II (CAII) and the receptor activator of NF-κB (RANK) in mouse osteoclast-like cells. Marrow cells were harvested from femora and tibiae of mouse and cultured in 6-well chamber slides. After 1 day of incubation, the marrow cells were exposed to M-CSF (25 ng/ml), RANKL (50 ng/ml), and different concentrations of OPG (50, 75, and 100 ng/ml, respectively) for 3 days. Osteoclast-like cells were confirmed by both tartrate-resistant acid phosphatase (TRAP) stain and bone resorption assay. The expression of RANK and CAIImRNA was determined with real-time fluorescent quantitative polymerase chain reaction. The numbers of multinucleated, TRAP-positive osteoclast-like cells, and resorption pits formed were observed. Compared with the M-CSF + RANKL group, RANKmRNA expression was statistically decreased in the M-CSF and M-CSF + RANKL + OPG (100 ng/ml) groups (P = 0.004, P = 0.024, respectively); Compared with the M-CSF, M-CSF + RANKL, and M-CSF + RANKL + OPG (100 ng/ml) group, CAIImRNA expression in the M-CSF + RANKL + OPG (75 ng/ml) groups was statistically decreased (P = 0.001, P = 0.008, and P = 0.036, respectively). These data suggest that OPG could regulate the expression of RANK and CA II mRNA in the marrow culture system.

Comparison of tumor and microenvironment secretomes in plasma and in platelets during prostate cancer growth in a xenograft model

To survive and metastasize, tumors interact with surrounding tissues by secreting growth factors and cytokines. In return, surrounding host tissues respond by changing their secretome. Numerous factors theoretically function as therapeutic targets or biomarkers of cancer growth and metastatic risk. However, it is unclear if these factors are tumor-derived or actually represent the host defense. To analyze the concentrations of tumor- and microenvironment-derived factors associated with neoplastic growth, we used ELISA-based arrays specific for murine or human proteins to establish a profile of tumor- or host-derived factors circulating in the plasma or within the platelets upon human tumor implantation into mice. Many factors characterized as tumor-derived were actually secreted by host tissues. This study uncovered the origin of various cytokines and revealed their circulation methods. We found that tumor-produced cytokines are predominantly sequestered in platelets. Sequestered proteins are protected from degradation and, thus, may be functional at metastatic sites. These findings identify tumor-specific targets for the detection and prevention of tumor growth and metastasis. As predicted by our model, monocyte chemotactic protein 1 and tumor necrosis factor alpha may be biomarkers for human cancers. Thus, our study identified several potential biomarkers that might be predictive of prostate cancer.

Proteoglycans on bone tumor development

Proteoglycans, extracellular matrix components, exert several activities on bone cells and seem crucial for maintaining an appropriate number of osteoblasts and osteoclasts. The overall data strengthen a pro-bone resorptive role for proteoglycans, through the control of osteoprotegerin availability and of receptor activator of NF-kappaB ligand bioactivity. In parallel, proteoglycans participate in the control of tumor development at different levels, including bone tumor development and bone metastases dissemination. This dual role makes them good candidates as regulatory molecules in the vicious cycle between tumor proliferation and bone resorption observed during tumor development in bone site. Knowledge of the biological roles of these molecules in cancer biology, tumor angiogenesis and metastasis has promoted the development of drugs targeting them.