Osteoclast Formation In Cells Research Articles

Chlorpyrifos Exposure Induces Parkinsonian Symptoms and Associated Bone Loss in Adult Swiss Albino Mice

Prenatal and early life exposure of chlorpyrifos (CPF), a widely used pesticide, is known to cause neuronal deficits and Parkinson's disease (PD). However, data about the effect of its exposure at adult stages on PD-like symptoms and associated bone loss is scanty. In the present study, we investigated the impact of CPF on the behavioral alterations seen in PD using adult Swiss albino mice. PD is often associated with bone loss. Hence, skeletal changes were also evaluated using micro-computed tomography and histology. MPTP was used as a positive control. Cell culture studies using MC3T3E-1, SHSY5Y, and primary osteoclast cultures were done to understand the cellular mechanism for the behavioral and skeletal changes. Our results showed that CPF treatment leads to PD-like symptoms due to the loss of dopaminergic neurons. Moreover, CPF has a deleterious effect on the trabecular bone through both indirect changes in circulating factors and direct stimulation of multinucleate osteoclast cell formation. The impact on the bone mass was even stronger than MPTP. In conclusion, this is the first report demonstrating that CPF induces parkinsonian features in adult Swiss albino mice and it is accompanied by loss of trabecular bone.

Cellular study of the LPS‐induced osteoclastic multinucleated cell formation from RAW264.7 cells

Despite the response to the receptor activator of nuclear factor κ-Β ligand (RANKL), a study has reported that lipopolysaccharide (LPS) could induce RAW264.7 linage osteoclastic differentiation. However, on the contrary, another study recently showed that the LPS-induced multinuclear cells from RAW264.7 did not express osteoclastic functions. Interestingly, in our previous study, we found that RAW264.7 cells pretreated with 10 ng LPS plus macrophage-colony stimulating factor did not show any effects for enhancing RANKL-induced osteoclastic cell differentiation. Therefore, in our current study, we aim to investigate the oteoclastogesis induction ability and efficacy of LPS in the RAW264.7 cell line and relevant molecular signaling. The osteoclastogenic activity of LPS-treated RAW264.7 linage was studied by bone resorption pits and fibrous actin study. Besides that, through polymerase chain reaction and western blot, we showed that the transcriptional factor c-Fos and Nfatc1 might be associated with LPS-induced osteoclastogenesis. Overall, the results of our current study showed positive proof for osteoclast generation from LPS-independent treatment, as well as established an optimal and efficient method for this process.

Mechanical loading induced osteocyte apoptosis and connexin 43 expression in three-dimensional cell culture and dental implant model.

Osteocytes are thought to act as stress sensors, and are known to display a gap junction-mediated stress-transfer mechanism. To demonstrate the stress-related function of osteocytes, cells of an osteocyte-like cell line derived from murine long bone osteocyte Y4 (MLO-Y4) were cultivated in a three-dimensional culture and subjected to cyclic loading from a titanium plate. This application of physiological loading using a titanium plate significantly increased connexin 43 (Cx43) expression, the number of dead and apoptotic cells, and receptor activator of nuclear factor κB ligand expression. Furthermore, the conditioned medium from the loaded osteocytes induced alkaline phosphatase activity in bone marrow cell culture. In addition, we immunohistologically determined whether bone metabolism increased as a result of the occlusal force in the bone surrounding the titanium implants in a rat model. Increased Cx43 expression and apoptotic osteocytes were observed in the loading group as well as a significantly increased number of tartrate-resistant acid phosphatase-positive cells. These findings indicate that stress from the implant adversely affected the osteocytes, which may promote osteoclastic and osteoblastic cell formation around the implants. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 815-827, 2019.

The effect of the new hemostatic agent Ostene® on bone healing: An experimental study in rabbits

Introduction: Ostene® is a water-soluble wax-like alkylene oxide copolymer preparation for use as a mechanical hemostatic agent. This study aims to evaluate the effects of Ostene® on bone healing. Materials and Methods: Twenty albino rabbits were divided into four groups according to post-treatment follow-up (24 hr, 3 days, 7 days, 14 days) with five rabbits in each group. Each rabbit in all groups was treated with two study materials (Ostene® and Gelfoam®). Three holes were made in the mandibular bone of each rabbit using 5mm surgical bur; two holes were made on right side: one for testing Ostene® and another for Gelfoam®. A third hole, on the left side of mandible, was not treated, and was used as a control. Finally, the incision was closed. The specimens were collected at different days post-treatment and examined by histopathology. Result and Discussion: This study showed that there is a significant difference (p-value≤ 0.05) between the Ostene® group and the other groups (Gelfoam® and control). At 24 hr post intervention, there is a significant difference in osteoblast cell formation (p-value=0.03), and osteoclast cell formation (p-value=0.05). New blood vessel formation, osteoblast and osteoclast cell formation for Ostene® group at 3 days post-intervention were also significantly different (p-values = 0.05, 0.03, 0.04, respectively). At 7 days post-intervention p-values were 0.05 for osteoblast formation and 0.04 for osteoclast formation, respectively. After 14 days of healing p-value for osteoblast cell formation in the Ostene® group was 0.05 and 0.04 for osteoclast cell formation. Conclusions: The bone hemostatic agent Ostene® is an effective at enhancing osteogenesis by initiating proliferation of osteoblast and osteoclast cells.

The Effect of New Haemostatic Agent Ostene® on Bone Healing (A Comparative Experimental Study)

ABSTRACT Introduction: Ostene ® is a bone wax-like preparation of water-soluble wax (WSW). It is an alkylene oxide copolymers mechanical haemostatic agent. This study aims to evaluate the effects of Ostene ® on bone healing. Materials and Methods: Twenty albino rabbits were randomized into three groups according to study materials into [Ostene, gelfoam, control (no material applied)]. Each group was subdivided into 4 groups according to healing periods (24h., 3days, 7days, 14 days). Three holes were made in mandible of each rabbit. Two holes were made on one side and third hole on the other side of mandible using 5mm surgical bur. Finally, the incision was closed. The specimens were collected and examined histopathologicaly. Result and Discussion: This study showed that there is a significant difference between ostene group and other groups in which P -value was ≤ 0.05. During 24h of healing, there is a significant difference in osteoblast cell formation in which P -value was 0.03 and osteoclast cell formation P -value was 0.05. New blood vessel formation, osteoblast and osteoclast cell formation for ostene group during 3days of healing P -value was 0.05, 0.03, 0.04 respectively .In 7days of healing P -value was 0.05 for osteoblast cell and 0.04 for osteoclast cell. In 14 days of healing P -value of ostene in osteoblast cell formation was 0.05 and osteoclast cell formation was 0.04. Conclusions: Ostene bone haemostatic agent is an effective agent that enhances osteogenesis by initiating proliferation of osteoblast and osteoclast cells.

The role of TGFβ receptor 1-smad3 signaling in regulating the osteoclastic mode affected by fluoride

Studies that have focused on the role TGFβ signaling plays in osteoclast activity are gradually increasing; however, literature is rare in terms of fluorosis. The aim of this study is to observe the role the TβR1/Smad3 pathway plays in fluoride regulating cellsosteoclast-like cells that are under the treatment of TGFβ receptor 1 kinase. The RANKL-mediated osteoclast-like cells from RAW264.7 cells were used as osteoclast precursor model. The profile of miRNA expression in fluoride-treated osteoclast-like cells exhibited 303 upregulated miRNAs, 61 downregulated miRNAs, and further drew 37 signaling pathway maps by KEGG and Biocarta pathway enrichment analysis. TGFβ and its downstream effectors were included among them. Osteoclast viability, formation and function were detected via MTT method, bone resorption pit and tartrate-resistant acid phosphatase (TRACP) staining, respectively. Results demonstrated that different doses of fluoride exhibited a biphasic effect on osteoclast cell viability, differentiation, formation and function. It indicated that a low dose of fluoride treatment stimulated them, but high dose inhibited them. SB431542 acted as TβR1 kinase inhibitor and blocked viability, formation and function of osteoclast-like cells regulated by fluoride. The expression of the osteoclast marker, RANK, and TβR1/Smad3 at gene and protein level was analyzed under fluoride with and without SB431542 treatment. Fluoride treatment indicated little effect on the RANK protein expression; however it significantly influenced TRACP expression in osteoclast-like cells. The stimulation of fluoride on the expression of Smad3 gene and phosphorylated Smad3 protein exhibited dose-dependent manner. SB431542 significantly impeded phosphorylation of Smad3 protein and TRACP expression in osteoclast-like cells that were exposed to fluoride. Our work demonstrated that TGFβ signaling played a key role in fluoride regulating osteoclast differentiation, formation and function. It elucidated that TβR1/Smad3 pathway participated in the mechanism of biphasic modulation of osteoclast mode regulated by fluoride.

Combined TRAF6 Targeting and Proteasome Blockade Has Anti-myeloma and Anti-Bone Resorptive Effects

TNF receptor-associated factor 6 (TRAF6) has been implicated in polyubiquitin-mediated IL1R/TLR signaling through activation of IκB kinase (IKK) to regulate the NF-κB and JNK signaling pathways. Here, TRAF6 protein was determined to be overexpressed in bone marrow mononuclear cells (BMMC) from patients with multiple myeloma. TRAF6 expression in BMMCs from patients with progressive disease is significantly elevated as compared with individuals in complete remission, with monoclonal gammopathy of undetermined significance, or healthy subjects. Furthermore, TRAF6 dominant-negative (TRAF6dn) peptides were constructed which specifically reduced TRAF6 signaling and activation of IKK. TRAF6 not only reduced cellular growth but also increased the apoptosis of multiple myeloma tumor cells in a concentration-dependent fashion. Because TRAF6 activates IKK through polyubiquitination, independent of its proteasome activity, a TRAF6dn peptide was combined with the proteasome inhibitors bortezomib or carfilzomib to treat multiple myeloma. Importantly, targeting of TRAF6 in the presence of proteasome inhibition enhanced anti-multiple myeloma effects and also decreased TLR/TRAF6/NF-κB-related signaling. Finally, TRAF6dn dose dependently inhibited osteoclast cell formation from CD14+ monocytes, induced with RANKL and mCSF, and markedly reduced bone resorption in dentin pits. In all, these data demonstrate that blocking TRAF6 signaling has anti-multiple myeloma effects and reduces bone loss.Implications: The ability to target TRAF6 signaling and associated pathways in multiple myeloma suggests a promising new therapeutic approach. Mol Cancer Res; 15(5); 598-609. ©2017 AACR.

Highlights of This Issue

Follicular dendritic cell (FDC) sarcomas are rare soft tissue sarcomas with significant metastatic potential. In addition, diagnosis is a challenge due to morphologic and immunophenotypic heterogeneity. To better understand this rare tumor type and uncover potential diagnostic and therapeutic targets, genomic analysis was performed on FDC sarcomas compared to other rare mesenchymal tumors. Based on differential gene expression and pathway enrichment, a number of critical transcriptional programs were identified: signal transduction, cell cycle, metabolism, extracellular matrix (ECM), chromatin organization, and immune system. Further investigation revealed that the PD-1 receptor and its ligands were upregulated in FDC sarcomas and suggests the potential for targeted immunotherapy.Mutations in isocitrate dehydrogenase 1 (IDH1) occur in the majority of low-grade gliomas and lead to the production of D-2HG. To determine the effects mutant IDH1 has on neural stem cells (NSCs) and on the microenvironment, Pirozzi and colleagues generated a genetically faithful conditional knock-in mouse model. The data demonstrate that mutant Idh1 confers reduced proliferation of NSCs both in vitro and in vivo, and results in a disorganized subventricular zone (SVZ). Additionally, this mouse glioma model shows that expression of mutant Idh1 leads to distinct molecular and histological features, and alters the course of tumor progression. Collectively, these findings provide new insights into IDH1-R132H-driven tumorigenesis, and establish a platform for future preclinical investigations focused on mutant IDH1-targeted therapy.Increased nucleolar size and number are common in many cancers. These increases partly reflect increased activity of RNA polymerase I, which catalyzes the synthesis of the precursor rRNA (45S rRNA). Guner and colleagues describe and validate a chromogenic in situ hybridization (CISH) assay for the 5′-external transcribed spacer (ETS) of the 45S rRNA in formalin-fixed, paraffin-embedded (FFPE) tissues as a measure of Pol I activity–a therapeutic target in cancer. This 5′ETS/45S signal, restricted to the nucleolus, was attenuated after pharmacological inhibition or RNAi depletion of Pol I. Most invasive prostatic adenocarcinomas and high-grade prostatic intraepithelial neoplasia had increased 5′ETS/45S signals. 5′ETS/45S CISH is a novel, potentially predictive and pharmacodynamic biomarker for Pol I inhibitors in tissue specimens.Bone marrow mononuclear cells from multiple myeloma patients overexpress tumor necrosis factor receptor-associated factor 6 (TRAF6). This protein has been implicated in polyubiquitin-mediated IL1R/TLR signaling through activation of IκB kinase which regulates the NF-κB and JNK signaling pathways. Inhibition of TRAF6 reduces tumor growth and enhances the anti-myeloma effects of proteasome inhibitors. TRAF6 dominant negative peptides also downregulate the RANKL/RANK signaling pathway leading to inhibition of osteoclast cell formation and a reduction in bone resorption. Taken together, these data indicate that targeting TRAF6 is a potential strategy for the treatment of multiple myeloma and its related disease-associated bone loss.

Clinical and pathological results of denosumab treatment for giant cell tumors of bone: Prospective study of 14 cases

ObjectiveGiant cell tumor of bone (GCT) is a primary, osteolytic, benign tumor of the bone. Surgery is the commonly used treatment; however, recurrence remains a problem. Receptor activator of nuclear factor kappa B (RANKL) is responsible for the formation of osteoclastic cells. Discovery of RANKL and its human monoclonal antibody, denosumab, led to use of denosumab for treatment of GCT. The aim of this study was to evaluate clinical and pathological results of treatment of GCT with denosumab and to assess adverse effect profile and recurrence rate. MethodsThirteen patients with 14 lesions were enrolled in the study. Mean age was 38.3 years. Patients were given subcutaneous injections of denosumab (120 mg) every 4 weeks (with additional doses on days 0, 8 and 15 in cycle 1 only) and were radiologically evaluated for tumor response. Pain and functional status were measured using Visual Analog Score (VAS) and Musculoskeletal Tumor Society Score (MSTS). Adverse effects were analyzed after each cycle. ResultsParticipants were 5 men and 8 women. Mean follow-up was 17 months. One lesion was Campanacci grade I, 8 were grade II, and 5 were grade III. Eight lesions were recurrent, and remaining were primary lesions. After average of 9 cycles (range: 4–17 cycles), all tumors underwent radiological regression. Ten lesions were removed surgically. More than 90% of giant cells were found to have regressed in all pathological specimens. On last follow-up, average VAS was 1 and MSTS was 87%. Fatigue and joint and muscle pain after injections was reported by 46% of patients, and mild hypocalcaemia was seen in 1 patient. ConclusionDenosumab has been shown to be a successful drug in treatment of GCT. Denosumab can be used as neoadjuvant for all recurrent lesions, grade II lesions with high surgical risk, grade III lesions, and metastatic cases of GCT. Level of evidenceLevel IV, Therapeutic study

Crosslinking of Fc Gamma-Rllb and Fc Epsilon-RI Binding Peptides Inhibits Osteoclast Formation in Multiple Myeloma through Inactivation of the ITAM Signaling Pathway

Introduction: Overactivity of osteoclasts resulting in bone destruction is a hallmark of multiple myeloma (MM). Receptor for activation of NF-kB ligand (RANKL) and monocyte colony stimulating factor (MCSF) signaling pathways both promote proliferation and survival of the precursors of the osteoclast lineage, and have been widely investigated in MM. The third pathway involved in osteoclast differentiation is the immunoreceptor tyrosine-based activation motif (ITAM) with c-Fms signaling. ITAM and its inhibitor ITIM provide the basis for two opposed signaling modules that duel for control of osteoclast formation. Human monocyte/macrophage expresses the low-affinity FcγRIIb and high-affinity Fcε receptor 1 (FcεRI). Both receptors mediate Syk phosphorylation to activate or inactivate downstream ITAM or ITIM signaling molecules. In this study, we determined the effects of an IgG(CH2-CH3) and IgE(CH2-CH3-CH4) fusion protein that activates the ITIM inhibitory pathway on downstream signaling of Syk and osteoclast formation in monocytes from MM patients.Methods: We constructed IgG(CH2-CH3) with an IgE(CH2-CH3-CH4) fusion protein using standard cloning techniques. We evaluated the fusion protein on osteoclast formation using cells from either human monocytes isolated from MM patients' peripheral blood mononuclear cells (PBMCs) or bone marrow (BM) MCs with an anti-CD14 micro-bead affinity column and magnetic bead selection (Miltenyi Biotec, Auburn, CA). The monocytes were cultured on slide-culture dishes (2 X 105 cells/well). The cells were treated with the fusion protein or with IgE or IgG and subsequently treated with 50ng/ml RANKL (receptor for activation of nuclear factor kB and 10ng/ml MCSF (monocyte colony stimulating factor) in order to stimulate osteoclast formation at the beginning of the culture and during a medium change after 3 days with the same amount of growth factors added. The cells were fixed for tartrate resistant acid phosphatase (TRAP)-staining assay on day 21. To investigate ITIM signaling pathway we determined Syk phosphorylation of monocytes treated or without treated with fusion protein by Western blot analysis.Results: We found that in a concentration-dependent fashion, the fusion protein inhibited osteoclast cell formation from CD14+ MCs from PB or BM exposed to RANKL and MCSF. We further analyzed the effects on the FcγRIIb-SHIP signaling pathway in monocytes induced with 50ng/ml RANKL and 10ng/ml MCSF following exposure to fusion protein or control IgG or IgE. The results showed that the monocytes showed markedly lower Syk phosphorylation following exposure to the fusion protein (100-200ng/ml). There was no change of Syk phosphorylationl in monocytes treated with IgG or IgE or IgG with IgE.Conclusions: The results of our study show that intact human IgG or IgE does not affect the ITAM or ITIM signaling pathways. However, a fusion protein consisting of IgG(CH2-CH3) with IgE(CH2-CH3-CH4) showed the ability to activate the ITIM inhibition pathway through FcγRIIb to reduce osteoclast formation. Thus, blockage of ITAM may be treating novel treatment for preventing bone loss for MM patients. DisclosuresNo relevant conflicts of interest to declare.

Higher TRAF6 and Fbxo 3 Expression Is With Progressive Multiple Myeloma and Blockage Of TRAF6 Inhibits Tumor Growth and Bone Resorption

Tumor necrosis factor receptor-associated factor 6 (TRAF6) has been implicated in regulating the NF-kB and JNK signal transduction pathways; and, thus, is likely to promote tumor cell proliferation and osteoclast formation. F-box proteins such as the E3 ligase component Fbxo3 and another F-box family member Fbxl 2, regulate TRAF protein signaling.First, we investigated TRAF6 expression in bone marrow mononuclear cells (BMMCs) from multiple myeloma (MM) patients with progressive disease or in remission and healthy subjects. The results showed higher TRAF6 protein expression among MM patients with progressive disease than among those in remission or healthy subjects. Notably, changes in TRAF6 protein expression in MM BMMCs were found to correlate with response of individual patients to treatment with the proteasome inhibitors bortezomib or carfilzomib. We have previously reported inhibition of MM cell proliferation and increase of apoptosis through regulation of the NF-kB and JNK pathways using a silencing TRAF6 C-domain mRNA construct. In this study, we cloned a 167 amino acid (in residues 333 to 508) portion of the TRAF6 dominant negative (TRAF6dn) and synthesized decoy peptides of the TRAF6 interaction domain with CD40 and the TRAF6-RANK binding domain. Decreases in cell proliferation and increase in cell apoptosis in MM BMMCs treated with TRAF6dn occurred in a concentrationdependent fashion. We also found TRAF6dn markedly inhibited osteoclast cell formation of monocytes induced by RANKL and mCSF in a dose-dependent manner. Next, we examined the effect of TRAF6dn on NF-kB and JNK by determining phosphorylation of JUN kinase kinase (JNKK), which activates the MAP kinase homologues SAPK and JNK in response to IL-1 receptor stimulation. MM BMMCs exposed to the TRAF6dn fragment or TRAF6 decoy peptide showed reduced phosphoNF-kB protein and phosphorylation of JNKK. These studies suggest that the TRAF6dn or combined TRAF6 decoy and CD40 decoy peptide may be excellent agents to block both MM cell growth and osteoclast formation in MM.We further investigated the protein expression of Fbxo 3, Fbxl 2 and TRAF6 in fresh BMMCs from MM patients with progressive disease or in remission. Results of Western blot analysis showed protein expression of Fbxo 3 and TRAF6 was increased and Fbxl 2 was decreased among patients with progressive disease compared to patients in remission.Thus, these results may offer a new mechanism through which MM tumor cells are regulated and provide a new therapeutic approach to treat MM and reduce the clinical consequences resulting from enhanced bone loss that commonly occur in these patients. Disclosures:No relevant conflicts of interest to declare.

Flavan‐3‐ol isolated from rhizome of Drynaria fortunei (Kunze) J. Sm. exerts osteoprotective effects via its actions on osteoblastogenesis and osteoclastogenesis

(‐)‐Epiafzelechin (FRD) is a flavan‐3‐ol found in rhizome of Drynaria fortunei (Kunze) J. Sm., a Chinese herb commonly used for management of bone diseases. Previous study suggested FRD could stimulate osteoblastic functions. Our study aims to determine if FRD act on osteoblastogenesis and osteoclastogenesis, and if its actions in bone cells involve the activation of Estrogen Receptors (ER) using pre‐osteoblast MC3T3‐E1, pre‐osteoclast RAW 264.7 as well as osteoblast‐like UMR 106 cells. FRD could increase alkaline phosphatase activity and secretory collagen in MC3T3‐E1 cells.FRD could reduce viability of RAW 264.7 cells and prevent the formation of osteoclastic cells, as observed by a reduction of Tartrate‐resistant acid phosphatase activity. Co‐incubation of ER antagonist (ICI 182780) with FRD abolished its positive effects on UMR 106 cell growth. FRD has a weak binding affinity to ER‐alpha and beta and could only weakly activate ER‐alpha, but not ER‐beta, mediated Estrogen Response Element (ERE)‐dependent transcriptional activity in UMR 106 cells.In conclusion, our results showed that FRD could stimulate osteoblastogenesis and inhibit osteoclastogenesis and its positive effects in bone cells appeared to be ER dependent.Funding support: RGC General Research Fund [POLYU 563209] and research studentship from the Hong Kong Polytechnic University

Modern Interpretation of Giant Cell Tumor of Bone: Predominantly Osteoclastogenic Stromal Tumor

Owing to striking features of numerous multinucleated cells and bone destruction, giant cell tumor (GCT) of bone, often called as osteoclastoma, has drawn major attractions from orthopaedic surgeons, pathologists, and radiologists. The name GCT or osteoclastoma gives a false impression of a tumor comprising of proliferating osteoclasts or osteoclast precursors. The underlying mechanisms for excessive osteoclastogenesis are intriguing and GCT has served as an exciting disease model representing a paradigm of osteoclastogenesis for bone biologists. The modern interpretation of GCT is predominantly osteoclastogenic stromal cell tumors of mesenchymal origin. A diverse array of inflammatory cytokines and chemokines disrupts osteoblastic differentiation and promotes the formation of excessive multi-nucleated osteoclastic cells. Pro-osteoclastogenic cytokines such as receptor activator of nuclear factor kappa-B ligand (RANKL), interleukin (IL)-6, and tumor necrosis factor (TNF) as well as monocyte-recruiting chemokines such as stromal cell-derived factor-1 (SDF-1) and monocyte chemoattractant protein (MCP)-1 participate in unfavorable osteoclastogenesis and bone destruction. This model represents a self-sufficient osteoclastogenic paracrine loop in a localized area. Consistent with this paradigm, a recombinant RANK-Fc protein and bisphosphonates are currently being tried for GCT treatment in addition to surgical excision and conventional topical adjuvant therapies.

Increased numbers of nonattached osteoclasts after long-term zoledronic acid therapy in mice.

Osteoclasts are key players in the maintenance of bone, which is an endocrine target and organ. Bisphosphonates, used for the management of metastatic bone diseases and osteoporosis, suppress osteoclasts. However, the impact of continuously suppressed osteoclasts is unknown. In this study, mice received zoledronic acid (ZA) for 13 months, nearly half the lifespan of mice, and the effects of continual osteoclast suppression on the bone environment and oral wound healing were determined. ZA therapy suppressed osteoclasts, resulting in significantly more bone mass compared with control. Despite continuous and intense suppression of bone loss in mice receiving ZA, serum calcium levels were maintained in the normal range. No differences were noted in serum tartrate-resistant acid phosphatase (TRAP) 5b levels between ZA-treated and control mice. Histomorphometric analyses of bones revealed that ZA therapy significantly decreased osteoclasts on the bone surface but, instead, substantially increased TRAP(+) mononuclear cells and osteoclasts that were not on the bone surface. When oral trauma was induced, such TRAP(+) mononuclear and nonattached osteoclasts increased considerably with increased inflammatory cell infiltration in the wounds. As a result, oral wound healing was hindered at the connective tissue level. Healing of the epithelium was unaffected. These findings indicate that the continual suppression of osteoclasts does not affect serum calcium levels and that long-term ZA therapy stimulates nonattached osteoclast and TRAP(+) mononuclear cell formation that are expanded rapidly in response to oral trauma. Caution should be exercised when using the serum TRAcP5b to estimate the efficacy of antiresorptive therapy.

TRAF6 Dominant Negative Peptides Block Intracellular Signaling Resulting in Anti-Myeloma and Anti-Bone Resorptive Effects in Multiple Myeloma

Abstract 2919Tumor necrosis factor receptor-associated factor 6 (TRAF6) has been implicated in regulating the NF-kB and JNK signal transduction pathways; and, thus, is likely to promote tumor cell proliferation and osteoclast formation. We have previously reported inhibition of cell proliferation and increase of apoptosis in multiple myeloma (MM) cells through regulation of these intracellular pathways through silencing of TRAF6 C-domain mRNA. To determine TRAF6 protein expression in fresh MM tumor cells, we performed an immunofluorescence assay (IFA). The results showed that expression of this factor in tumor cells from bone marrow (BM) from MM patients with progressive disease is higher than in cells from patients with monoclonal gammopathies without disease progression or normal controls. We further examined the effects of TRAF6 negative dominant peptides on intracellular signaling pathways. Briefly, cells from the RPMI8226 or MM1s MM cell lines or primary MM BM samples were treated with or without TRAF6 inhibition peptide for 24 hours and then stimulated with either IGF1 (30ng/ml) or IL1 β (20ng/ml) for 30 minutes. The cells were lysed and Western blot analysis performed to determine protein phosphorylation and RT-PCR for gene expression. TRAF6 has been found to be an E3 ligase for Akt ubiquitination. We found that IGF1 increased the phosphorylation of AKT and treatment with TRAF6 inhibition peptide markedly decreased its phosphorylation compared to treatment with a control peptide in RPMI8226 and primary MM tumor cells. Downstream of AKT, C-Raf phosphorylation was also significantly reduced with treatment with TRAF6 inhibition peptide. Notably, cyclin D gene expression in MM tumor cells treated with TRAF6 inhibition peptide was reduced as determined with an RT-PCR. In contrast, the gene expression of mTOR was increased in RPMI8226 cells treated with TRAF6 inhibition peptide whereas there was no change in its expression in MM1s and primary MM tumor cells. It is quite possible that the increase in mTOR expression in RPMI8226 cells may act as a negative feedback which results from blockage of the ubiquitination of TRAF6. We further examined the effect of the TRAF6 inhibition peptide on NF-kB and JNK signaling as determined through evaluation of JUN kinase kinase (JNKK), which activates the MAP kinase homologues SAPK and JNK in response to IL-1 receptor stimulation. Phospho-NF-kB protein was reduced and phosphorylation of JNKK was clearly decreased with exposure to the TRAF6 inhibition peptide. We examined c-Jun, a component of the transcription factor complex AP-1, which binds and activates transcription at TRE/AP-1 elements. Total endogenous c-Jun is reduced following exposure of RPMI8226 cells to the TRAF6 inhibition peptide. Consistent with our past findings, TRAF6 inhibition peptide significantly inhibited osteoclast formation from CD14+ induced by RANKL and M-CSF with in a concentration dependent fashion whereas control peptides showed no effects on osteoclast formation. In addition, inhibition of the TRAF6 signaling blocked not only myeloma cell proliferation induced by AKT and NF-kB activation but also osteoclast cell formation mediated through transcription at TRE/AP-1 elements. The study has been extended to our SCID-hu murine model of human myeloma. Disclosures:No relevant conflicts of interest to declare.

Stage-dependent suppression of the formation of dentin-resorbing multinuclear cells with migration inhibitory factor in vitro

The macrophage migration inhibitory factor (MIF) is a crucial mediator of immune responses and is known to play a pivotal role in cell proliferation and differentiation. In this study, we assessed whether MIF exerts regulatory effects on osteoclast formation in bone marrow cells and, if so, by what mechanism. Bone marrow cells were either co-cultured with MC3T3-E1 cells or cultured with macrophage-colony stimulating factor (M-CSF) and the soluble form of the receptor activator of the nuclear factor-κB ligand (RANKL). Under the influence of MIF, the formation of osteoclastic multinuclear cells was examined. The number of multinuclear TRAP-positive cells formed in the co-culture was significantly reduced when MIF (≥0.1 μg/ml) was exogenously applied during the third and fourth days of the 6-day cultivation period. MIF affected neither the number of mononuclear TRAP-positive cells induced with M-CSF and RANKL, nor the expression of RANKL and osteoprotegerin in MC3T3-E1 cells. TRAP-positive cells cultured on dentin slices with MIF showed lower dentin-resorbing activity than those cultured without MIF. These results suggest that MIF has no regulatory roles in the differentiation of bone marrow cells to mononuclear TRAP-positive cells, but has inhibitory effects on the formation of mature osteoclasts by preventing cell fusion, which may eventually interfere with the osteoclast-mediated dentin resorption.

Abstract LB-305: The tyrosine kinase inhibitor bafetinib (INNO-406) inhibits osteoclast formation and bone resorption

Abstract Lyn phosphorylation up-regulates several kinases including Syk, phospholipase Cγ2 and phosphatidyl inostitol-3 kinase through the immunoreceptor tyrosine-based activation motif (ITAM). Lyn plays critical roles in cell proliferation, Ca2+ mobilization and cell differentiation. This kinase also plays an essential role in transmission of inhibitory signals through phosphorylation of tyrosine residues within the immunoreceptor tyrosine-based inhibitory motifs (ITIM). ITAM-ITIM cross talk is important for macrophage differentiation and osteoclast formation. Bafetinib (INNO-406) is an inhibitor of Bcr-Abl, Fyn and Lyn kinase. No studies have evaluated potential anti-bone resorptive effects of this tyrosine kinase inhibitor. Osteoclasts are multinucleated bone-resorbing cells derived from monocytes that play critical roles in bone remodeling. To evaluate the effects of bafetinib on osteoclast formation and bone resorption, we isolated monocytes using immunomagnetic bead selection from normal or multiple myeloma (MM) patients' PBMCs. CD14+ cells (monocytes) were treated with 50ng/ml RANKL and 20 ng/ml MCSF at the beginning of the culture and during a medium change at 3 days. During the second day of culture, bafetinib or the nitrogen-containing bisphosphonate zoledronic acid, an inhibitor of osteoclast formation and bone resorption, was added into the cells. The cells were fixed and tartrate-resistant acid phosphatase staining performed on day 21. Bafetinib and zoledronic acid both markedly inhibited osteoclast cell formation of monocytes induced by RANKL and MCSF at similar concentrations in a concentration-dependent fashion in both monocytes derived from MM patients and normal subjects. Next, we assessed bone resorption using monocytes that were induced with M-CSF and RANKL and cultured on bone slides for 28 days. At that time, bone resorption was determined using toluidine blue staining. Resorption pits were measured and percentage of surface area with lacunar resorption on each bone slice was determined using an image analysis system. At a concentration as low as 5μM, bafetinib significantly inhibited bone resorption in a concentration-dependent fashion (P<0.001). We further examined the effects of bafetinib on NF-κB and JNK phosphorylation in human monocytes that were induced with RANKL and MCSF through assessment of JUN kinase kinase (JNKK), which activates the MAP kinase homologues SAPK and JNK in response to IL-1 receptor stimulation. Phospho-NF-κB protein levels were reduced and phosphorylation of JNKK was also decreased following exposure to bafetinib. These studies suggest that bafetinib may be a new therapeutic option to reduce skeletal complications through its ability to block osteoclast development and reduce bone resorption. We are evaluating the effects of this tyrosine kinase inhibitor on bone resorption in vivo using our SCID-hu murine models of human myeloma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-305. doi:10.1158/1538-7445.AM2011-LB-305

Blockage of TRAF6 by Dominant Negative Peptides to Inhibit Multiple Myeloma (MM) Cell Proliferation and Osteoclast Formation through NF-κB, JNK and AKT Signal Transduction Pathways

AbstractAbstract 4068Several members of the tumor necrosis factor receptor-associated factor (TRAF) family, including TRAF1, TRAF2, TRAF3, TRAF5, and TRAF6 have been implicated in regulating signal transduction from various TRAF family members. However, the unique biological function of TRAF6 is largely determined by its TRAF-C domain, which does not interact with peptide motifs that are recognized by TRAF1, -2, -3 or -5. We have reported inhibition of MM cell proliferation and increase of apoptosis through regulation of the NF-κB and JNK pathways through silencing TRAF6 C-domain mRNA and the dominant negative peptide expression vector (Chen H. et al, Oncogene, 2006; Li M. et al, Blood 2009). TRAF6 have been recently found as a ligase for Akt ubiquitination (Yang WL et al, Science, 2009). Akt signaling plays a central role in many biological functions, such as cell proliferation and apoptosis. In this study, we first investigated whether TRAF6 is over-expressed in MM tumor cells. Twelve MM fresh bone marrow (BM) aspirates derived from MM patients were assessed using Western blot analysis and immunohistochemical staining with anti-TRAF6 antibody. We found that TRAF6 protein was highly expressed in tumor cells from MM patients compared to normal human BM samples. Based on TRAF6, CD40, and RANKL sequences and crystal structures, we targeted the TRAF6 C-domain binding residues. We found that TRAF6 dominant negative binding peptide (TRAF6dn) significantly inhibited MM cell proliferation maximally at 72 hours using the MTS cell proliferation assay whereas effects on inducing MM cell apoptosis were most prominent at 48 hours as assessed with Annexin V staining with flow cytometric analysis. The decrease in cell proliferation and increase in cell apoptosis occurred in a concentration peptide-dependent fashion. Furthermore, phosphorylation of both AKT and NF-κB were also reduced using our human TRAF6dn or decoy peptides. We also examined the effect of the TRAF6dn peptide on the JNK pathway since this signaling pathway is also associated with cell cycle effects in MM. We measured JUN kinase kinase (JNKK), which activates the MAP kinase homologues SAPK and JNK in response to IL-1 receptor stimulation. The results showed that the phosphorylation of JNKK is markedly reduced after treatment with the TRAF6dn peptide. Furthermore, we examined c-Jun, a component of the transcription factor complex AP-1, which binds and activates transcription at TRE/AP-1 elements. We evaluated the effect of TRAF6dn peptide on osteoclast formation using cells from human monocytes isolated by anti-CD14 micro-bead affinity column from MM patients' BM or peripheral blood mononuclear cells. The monocytes were cultured on slide-culture dishes (2 × 105 cells/well).We found TRAF6dn markedly inhibited osteoclast cell formation from monocytes induced with RANKL and mCSF in a concentration- dependent fashion compared with a control group using tartrate resistant acid phosphatase staining. We further assessed whether TRAF6dn can reduce bone resorption using a dentin bone resorption assay. BM-derived monocytes were isolated as above and were cultured on dentin bone slides (4 × 105 cells/slide). The cells treated with a TRAF6dn peptide or the control peptide, were incubated with 50ng/ml RANKL and 10ng/ml MCSF. All cells were cultured for 21 days. It was found that TRAF6dn significantly inhibited lacunar resorption in a concentration-dependent fashion. These studies suggest that TRAF6 is over-expressed in MM and our TRAF6dn peptide inhibits many signaling pathways critical to the growth of MM and formation of osteoclasts resulting in marked anti-MM effects and reduction in osteoclast formation resulting in marked inhibition of bone resorption. Thus, this novel approach may offer a new therapeutic approach to both treat multiple myeloma and reduce the clinical consequences resulting from enhanced bone loss that commonly occur in these patients. Disclosures:No relevant conflicts of interest to declare.

Rapid and Sensitive Lentivirus Vector-Based Conditional Gene Expression Assay to Monitor and Quantify Cell Fusion Activity

Cell-to-cell fusion is involved in multiple fundamental biological processes. Prominent examples include osteoclast and giant cell formation, fertilization and skeletal myogenesis which involve macrophage, sperm-egg and myoblast fusion, respectively. Indeed, the importance of cell fusion is underscored by the wide range of homeostatic as well as pathologic processes in which it plays a key role. Therefore, rapid and sensitive systems to trace and measure cell fusion events in various experimental systems are in demand. Here, we introduce a bipartite cell fusion monitoring system based on a genetic switch responsive to the site-specific recombinase FLP. To allow flexible deployment in both dividing as well as non-dividing cell populations, inducer and reporter modules were incorporated in lentivirus vector particles. Moreover, the recombinase-inducible transcription units were designed in such a way as to minimize basal activity and chromosomal position effects in the “off” and “on” states, respectively. The lentivirus vector-based conditional gene expression assay was validated in primary human mesenchymal stem cells and in a differentiation model based on muscle progenitor cells from a Duchenne muscular dystrophy patient using reporter genes compatible with live- and single-cell imaging and with whole population measurements. Using the skeletal muscle cell differentiation model, we showed that the new assay displays low background activity, a 2-log dynamic range, high sensitivity and is amenable to the investigation of cell fusion kinetics. The utility of the bipartite cell fusion monitoring system was underscored by a study on the impact of drug- and RNAi-mediated p38 MAPK inhibition on human myocyte differentiation. Finally, building on the capacity of lentivirus vectors to readily generate transgenic animals the present FLP-inducible system should be adaptable, alone or together with Cre/loxP-based assays, to cell lineage tracing and conditional gene manipulation studies in vivo.

TRAF6-Dominant Negative Peptides Show Potent Inhibitory Effects On Multiple Myeloma, Osteoclast Formation and Bone Resorption.

Abstract 611Tumor necrosis factor receptor-associated factor 6 (TRAF6) has been implicated in regulating NF-κB and JNK signal transduction pathway resulting in inhibition of tumor cell proliferation and osteoclast formation. The unique biological function of TRAF6 is largely determined within its TRAF-C domain which does not interact with peptide motifs that are recognized by other TRAFs including 1, 2, 3 or 5. We have recently reported inhibition of cell proliferation and increased apoptosis of multiple myeloma (MM) cells through regulation of the NF-κB and JNK pathways through silencing the TRAF6 C-domain mRNA. In this study, we determined the effects of TRAF6 dominant negative peptides on MM cells, osteoclast formation and bone resorption. We cloned a 167 amino acid (in residues 333 to 508) fragment to produce a TRAF6 negative dominant (TRAF6dn) construct and synthesized an inhibitory decoy peptide of the TRAF6 interaction domain with CD40 and another peptide interacting with the TRAF6-RANK binding domain as well as a control peptide. All peptides were synthesized with a 16 amino acid permeable peptide. Using the MM1s, RPMI8226, and U266, we evaluated the effects of these peptides on MM tumor cell growth using an MTS assay and apoptosis with an Annexin V assay. We found that TRAF6dn peptides significantly inhibited MM cell proliferation maximally at 72 hours whereas effects on induction of apoptosis in MM cells were most prominent at 48 hours. The decrease in cell proliferation and increase in cell apoptosis occurred in a concentration-dependent fashion. We found that TRAF6dn also markedly inhibited osteoclast cell formation from freshly derived human monocytes induced by RANKL and M-CSF in a concentration-dependent fashion comparing with cells exposed to control peptide. We further examined the effects on MM cell apoptosis of the TRAF6 decoy or CD40 decoy peptides alone and in cells exposed to the combination of both peptides. The results showed either decoy peptide alone slightly induced apoptosis of MM tumor cells whereas the combination of both peptides demonstrated marked apoptosis of MM cells. We also showed that although melphalan alone induced apoptotic cell death, this effect was markedly enhanced when this alkylating agent was combined with the TRAF6 decoy peptide. Although the CD40 peptide alone did not inhibit osteoclast formation, TRAF6 decoy peptide alone and the combination of both decoy peptides markedly inhibited formation of these bone resorbing cells. We also examined the effects of TRAF6dn on NF-κB and JNK by measuring JUN kinase kinase (JNKK), which activates the MAP kinase homologues SAPK and JNK in response to IL-1 receptor stimulation. Phospho-NF-κB protein levels and phosphorylation of JNKK are both markedly reduced when MM cells are exposed to TRAF6dn fragment or TRAF6 decoy peptide. These studies suggest that TRAF6dn or the combination of TRAF6 decoy and CD40 decoy peptides may be excellent targets to block both myeloma cell and osteoclast cell formation. The study has been extended to assess the effects of these peptides in vivo using our SCID-hu murine model of human myeloma. Disclosures:No relevant conflicts of interest to declare.