The Effects of CCL3 on Osteoblast Inhibition in Myeloma-Induced Bone Disease

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 5672-5672
Author(s):  
Rong Fu ◽  
Sijie Zhao ◽  
Zonghong Shao
Keyword(s):  
Bone Disease ◽  
Plasma Cells ◽  
Conflicts Of Interest ◽  
Hematologic Malignancy ◽  
Bone Destruction ◽  
Neutralizing Antibody ◽  
Osteogenic Potential ◽  
Matrix Mineralization ◽  
Osteoblast Activity

Abstract Multiple myeloma (MM) is a hematologic malignancy characterized by the accumulation of monoclonal plasma cells in the bone marrow. A common manifestation of the disease is bone destruction that caused by increased osteoclastic bone resorption and decreased bone formation. Suppression of osteoblast activity appears to persist even in patients enjoying long-term complete remission that without any detectable MM tumor cells. CCL3, also known as MIP-1α, is a pro-inflammatory and chemoline. To investigate if CCL3, a recently described osteoclast stimulatory factor,was possibly involved in the inhibition of osteoblast in MM-induced bone disease,osteoblast from BM of MM patients and healthy donors were cultured in vitro. Our results showed the proliferation and osteogenic potential of osteoblasts from MM patients were suppressed. MM-derived OBs expressed higher levels of CCR1 compared with normal controls. It’s an indication that CCL3 is able to influence OBs in MM bone disease (MBD).We cultured MM-derived OBs in osteogenic media and then stimulated them with CCL3 in the absence or presence of neutralizing antibody against CCL3. Our data suggested that CCL3 impaired matrix mineralization and suppressed osteocalcin (OCN).Gene expression analysis of osteoblastic transcription factors in CCL3-treated OBs revealed a Runx2 and Osterix downregulation. CCL3 antibody at least partially restored OBs activity with an upregulation of OCN levels and Runx2 and Osterix expression. These results showed that CCL3 may contribute to OB/OC imbalance by inhiting OBs’ dedifferentiation and function in MBD. Disclosures No relevant conflicts of interest to declare.

Osteoprotegerin is bound, internalized, and degraded by multiple myeloma cells

Blood ◽  
2002 ◽  
Vol 100 (8) ◽  
pp. 3002-3007 ◽  
Author(s):  
Therese Standal ◽  
Carina Seidel ◽  
Øyvind Hjertner ◽  
Torben Plesner ◽  
Ralph D. Sanderson ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Disease ◽  
Plasma Cells ◽  
Hematologic Malignancy ◽  
Bone Destruction ◽  
Nuclear Factor Κb ◽  
Heparin Binding ◽  
Bone Homeostasis ◽  
Myeloma Cells ◽  
Heparan Sulfates

Multiple myeloma (MM) is a hematologic malignancy characterized by accumulation of plasma cells in the bone marrow (BM). Bone destruction is a complication of the disease and is usually associated with severe morbidity. The balance between receptor activator of nuclear factor-κB (NF-κB) ligand and osteoprotegerin (OPG) is of major importance in bone homeostasis. We have recently shown that serum OPG levels are lower in patients with myeloma than in healthy individuals. Here we show that myeloma cells can bind, internalize, and degrade OPG, thereby providing a possible explanation for the lower levels of OPG in the BM of patients with MM. This process is dependent on interaction of OPG with heparan sulfates on the myeloma cells. The results suggest a novel biologic mechanism for the bone disease associated with MM and that treatment of the bone disease with OPG lacking the heparin-binding domain should be considered.

scholarly journals Ticagrelor Modulates Proliferation in Multiple Myeloma Via P1 and P2 Receptor-Mediated Mechanisms

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 5694-5694
Author(s):  
Elan Meltzer ◽  
Aranzazu Mediero ◽  
Carl Whatling ◽  
Jeffrey S Berger ◽  
Bruce Cronstein
Keyword(s):  
Multiple Myeloma ◽  
Cell Proliferation ◽  
Research Funding ◽  
Plasma Cells ◽  
Hematologic Malignancy ◽  
Bone Destruction ◽  
Extracellular Adenosine ◽  
Myeloma Cells ◽  
Platelet Releasate

Abstract Background:Multiple Myeloma (MM) is a hematologic malignancy involving uncontrolled proliferation of plasma cells and is particularly trophic to bone where it induces osteoclast-mediated bone destruction. Ticagrelor is a platelet inhibitor that blocks P2Y12 receptors and inhibits ENT1-mediated adenosine uptake, thereby increasing extracellular adenosine, which activates P1 receptors. Prior studies demonstrate that ticagrelor increases life span in a murine model of MM via its effect on extracellular adenosine. Prior studies also demonstrate an increase in proliferation, in vitro, and tumor growth, in vivo, of MM cells in the presence of platelet releasate. Ticagrelor blocks in vitro platelet-stimulated myeloma proliferation, suggesting a positive relationship and interaction between active platelets and multiple myeloma. We therefore determined whether the effect of ticagrelor on myeloma cells was mediated by extra-cellular adenosine or/and inhibition of platelet function. Methods:Human primary myeloma cells (KMS) were incubated with ticagrelor (10-9-10-4 M) in the presence of 5ng/ml IL-6 in the absence/presence of an A2AR antagonist (ZM241385 10-6M) and platelets (1:500 myeloma cell:platelets). In other experiments MM cells were incubated in the presence of platelet releasate, releasate from platelets treated with ticagrelor, or ticagrelor alone. Proliferation was assayed by Cell Titer MTS assay (Promega). Results: Ticagrelor inhibited MM cell proliferation by 20% (p<0.0001, IC50=0.5µM). This effect was abrogated by ZM241385 (48±6% increased vs. ticagrelor, p<0.0001). Platelet releasate increased MM proliferation by 33±6% (p<0.05) and ticagrelor inhibited the effect of platelet releasate on MM cell proliferation (IC50=0.12µM). Conclusions:These results suggest that ticagrelor inhibits proliferation of malignant plasma cells by a mechanism dependent on both adenosine A2A and platelet P2Y12 receptors. Moreover, platelet releasate intensifies proliferation, and this effect is reversed when the P2Y12 receptor is blocked by ticagrelor. Figure 1 Figure 1. Figure 2 Figure 2. Figure 3 Figure 3. Disclosures Meltzer: NIH: Research Funding; Celgene: Research Funding; AstraZeneca: Research Funding. Mediero:AstraZeneca: Research Funding; Celgene: Research Funding; NIH: Research Funding. Whatling:AstraZeneca: Employment. Berger:Merck: Membership on an entity's Board of Directors or advisory committees; AZ: Research Funding. Cronstein:AstraZeneca: Consultancy, Research Funding; CanFite: Equity Ownership; Gizmo Therapeutics: Consultancy; Eli Lilly & Co.: Consultancy; NIH: Research Funding; Celgene: Research Funding.

Bone disease as the first manifestation of systemic AL-amyloidosis

2020 ◽  
Vol 92 (7) ◽  
pp. 85-89
Author(s):  
L. P. Mendeleeva ◽  
I. G. Rekhtina ◽  
A. M. Kovrigina ◽  
I. E. Kostina ◽  
V. A. Khyshova ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Bone Disease ◽  
Plasma Cells ◽  
Interventricular Septum ◽  
Bone Destruction ◽  
Amyloid Deposition ◽  
Bone Lesions ◽  
Al Amyloidosis ◽  
Linear Type

Our case demonstrates severe bone disease in primary AL-amyloidosis without concomitant multiple myeloma. A 30-year-old man had spontaneous vertebral fracture Th8. A computed tomography scan suggested multiple foci of lesions in all the bones. In bone marrow and resected rib werent detected any tumor cells. After 15 years from the beginning of the disease, nephrotic syndrome developed. Based on the kidney biopsy, AL-amyloidosis was confirmed. Amyloid was also detected in the bowel and bone marrow. On the indirect signs (thickening of the interventricular septum 16 mm and increased NT-proBNP 2200 pg/ml), a cardial involvement was confirmed. In the bone marrow (from three sites) was found 2.85% clonal plasma cells with immunophenotype СD138+, СD38dim, СD19-, СD117+, СD81-, СD27-, СD56-. FISH method revealed polysomy 5,9,15 in 3% of the nuclei. Serum free light chain Kappa 575 mg/l (/44.9) was detected. Multiple foci of destruction with increased metabolic activity (SUVmax 3.6) were visualized on PET-CT, and an surgical intervention biopsy was performed from two foci. The number of plasma cells from the destruction foci was 2.5%, and massive amyloid deposition was detected. On CT scan foci of lesions differed from bone lesions at multiple myeloma. Bone fragments of point and linear type (button sequestration) were visualized in most of the destruction foci. The content of the lesion was low density. There was no extraossal spread from large zones of destruction. There was also spontaneous scarring of the some lesions (without therapy). Thus, the diagnosis of multiple myeloma was excluded on the basis based on x-ray signs, of the duration of osteodestructive syndrome (15 years), the absence of plasma infiltration in the bone marrow, including from foci of bone destruction by open biopsy. This observation proves the possibility of damage to the skeleton due to amyloid deposition and justifies the need to include AL-amyloidosis in the spectrum of differential diagnosis of diseases that occur with osteodestructive syndrome.

Impact of Natural Dietary Agents on Multiple Myeloma Prevention and Treatment: Molecular Insights and Potential for Clinical Translation

2020 ◽  
Vol 27 (2) ◽  
pp. 187-215 ◽  
Author(s):  
Lavinia Raimondi ◽  
Angela De Luca ◽  
Gianluca Giavaresi ◽  
Agnese Barone ◽  
Pierosandro Tagliaferri ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Multiple Myeloma ◽  
Natural Products ◽  
Bone Disease ◽  
Molecular Mechanisms ◽  
Plasma Cells ◽  
Hematologic Malignancy ◽  
Signal Transduction Pathways ◽  
Pharmacologically Active ◽  
Dietary Agents

: Chemoprevention is based on the use of non-toxic, pharmacologically active agents to prevent tumor progression. In this regard, natural dietary agents have been described by the most recent literature as promising tools for controlling onset and progression of malignancies. Extensive research has been so far performed to shed light on the effects of natural products on tumor growth and survival, disclosing the most relevant signal transduction pathways targeted by such compounds. Overall, anti-inflammatory, anti-oxidant and cytotoxic effects of dietary agents on tumor cells are supported either by results from epidemiological or animal studies and even by clinical trials. : Multiple myeloma is a hematologic malignancy characterized by abnormal proliferation of bone marrow plasma cells and subsequent hypercalcemia, renal dysfunction, anemia, or bone disease, which remains incurable despite novel emerging therapeutic strategies. Notably, increasing evidence supports the capability of dietary natural compounds to antagonize multiple myeloma growth in preclinical models of the disease, underscoring their potential as candidate anti-cancer agents. : In this review, we aim at summarizing findings on the anti-tumor activity of dietary natural products, focusing on their molecular mechanisms, which include inhibition of oncogenic signal transduction pathways and/or epigenetic modulating effects, along with their potential clinical applications against multiple myeloma and its related bone disease.

scholarly journals Identification of the Cysteine Protease Legumain as a Potential Chronic Hypoxia-Specific Multiple Myeloma Target Gene

Cells ◽  
2022 ◽  
Vol 11 (2) ◽  
pp. 292
Author(s):  
Ada-Sophia Clees ◽  
Verena Stolp ◽  
Björn Häupl ◽  
Dominik C. Fuhrmann ◽  
Frank Wempe ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Cysteine Protease ◽  
Chronic Hypoxia ◽  
Plasma Cells ◽  
Hematologic Malignancy ◽  
Low Oxygen ◽  
Clonal Proliferation ◽  
Temporal Adaptation ◽  
Specific Regulation

Multiple myeloma (MM) is the second most common hematologic malignancy, which is characterized by clonal proliferation of neoplastic plasma cells in the bone marrow. This microenvironment is characterized by low oxygen levels (1–6% O2), known as hypoxia. For MM cells, hypoxia is a physiologic feature that has been described to promote an aggressive phenotype and to confer drug resistance. However, studies on hypoxia are scarce and show little conformity. Here, we analyzed the mRNA expression of previously determined hypoxia markers to define the temporal adaptation of MM cells to chronic hypoxia. Subsequent analyses of the global proteome in MM cells and the stromal cell line HS-5 revealed hypoxia-dependent regulation of proteins, which directly or indirectly upregulate glycolysis. In addition, chronic hypoxia led to MM-specific regulation of nine distinct proteins. One of these proteins is the cysteine protease legumain (LGMN), the depletion of which led to a significant growth disadvantage of MM cell lines that is enhanced under hypoxia. Thus, herein, we report a methodologic strategy to examine MM cells under physiologic hypoxic conditions in vitro and to decipher and study previously masked hypoxia-specific therapeutic targets such as the cysteine protease LGMN.

Myeloma Cells Switch Osteoblastogenesis to Adipogenesis and Suppress Bone Formation

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3386-3386 ◽  
Author(s):  
Jing Yang ◽  
Zhiqiang Liu ◽  
Huan Liu ◽  
Jin He ◽  
Pei Lin ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Bone Formation ◽  
Osteoblast Differentiation ◽  
Conflicts Of Interest ◽  
Bone Destruction ◽  
Current Treatment ◽  
New Bone Formation ◽  
Myeloma Cells ◽  
Dickkopf 1

Abstract Bone destruction is a hallmark of myeloma, and has a severe impact on patients’ quality of life and survival. Unfortunately, current treatment only offers moderate palliative effects, and this disease remains incurable. The bone changes in myeloma patients results from increased osteoclast-mediated bone resorption and decreased osteoblast-mediated bone formation. In particular, new bone formation that usually occurs at sites of previously resorbed bones is deeply suppressed; as a result, areas of bone destruction rarely heal. Previous studies have shown that myeloma cells inhibit osteoblast differentiation from mesenchymal stem cells (MSCs), and the Wnt/b-catenin signaling pathway is suppressed via myeloma-produced Wnt antagonists such as dickkopf-1. However, the role of dickkopf-1 in myeloma-induced inhibition of bone formation remains controversial since myeloma cells alone do not produce sufficient dickkopf-1 to suppress osteoblast differentiation. In addition, the administration of an antibody against dickkopf-1 in myeloma patients failed to restore new bone formation, indicating there must be an additional mechanism for inhibition of osteoblast differentiation seen in myeloma. While MSCs can differentiate into mature osteoblasts, they are also capable of differentiating into adipocytes, which is a major cell type in marrow stroma. We observed that myeloma cells (cell lines and primary cells isolated from myeloma patients’ bone marrow) injected into human or mouse bone not only reduced osteoblast number, but also increased adipocyte number and activity in bone marrow. Similar observations were seen in the clinical setting where collections of adipocytes were found in the bone marrow of newly diagnosed, untreated myeloma patients. Patients with greater bone destruction had higher adipocyte numbers than those in patients with less bone destruction, indicating a relationship among myeloma cells, adipogenesis, and osteoblastogenesis. We hypothesized that inhibition of osteoblast differentiation is a consequence of myeloma-dependent alterations in the control of the MSCs’ fate into osteoblasts or into adipocytes. In our studies, we co-cultured MSCs with myeloma cells in a mixed medium (that contained both adipocyte and osteoblast media), and we observed co-culture with myeloma cells induced more adipocyte than osteoblast formation. Moreover, co-culture with myeloma cells enhanced adipocyte differentiation in vitro. Interestingly, separation of the cells by transwell inserts significantly reduced such effect. By analysis of the adhesion molecules in myeloma cells, we identified integrin α4β1 as a novel contributor in regulation of adipogenesis and osteoblastogenesis. Thus, our studies indicate that in the presence of myeloma cells, MSCs may be more prone to differentiate into adipocytes than into osteoblasts via α4β1. Our studies also suggest the development of new strategies to improve the care of myeloma patients with bone destruction by targeting α4β1 and its signaling pathways. Disclosures No relevant conflicts of interest to declare.

Antitumor Activity of a Novel Proteasome Inhibitor BSc2118 Against Multiple Myeloma

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 5725-5725
Author(s):  
Meirong Zang ◽  
Lanting Liu ◽  
Xin Li ◽  
Wei Li ◽  
Ulrike Kuckelkorn ◽  
...  
Keyword(s):  
Cell Lines ◽  
Proteasome Inhibitor ◽  
Molecular Mechanisms ◽  
Plasma Cells ◽  
Conflicts Of Interest ◽  
Proteasome Activity ◽  
Autophagy Flux ◽  
Ubiquitinated Proteins ◽  
Rpmi 8226

Abstract Background: Although the first generation of proteasome inhibitor bortezomib is very effective, the development of resistance limits it long-term utility. In this study, we explored the efficiency and molecular mechanisms of the novel, irreversible proteasome inhibitor BSc2118, particularly, the reversal of bortezomib resistance. Materials and Methods: Human MM cell lines (MM.1S, MM.1R, RPMI-8226, U266, NCI-H929) were treated with BSc2118 at various concentrations for 48h, and assessment for cell viability by CCK-8 assay. MM.1S and MM.1R cells were treated with BSc2118 for 24 hours, and cell cycle and apoptosis analysis were conducted by flow cytometry. Associated molecules were detected by qRT-PCR and western blot. Chymotrypsin-like proteasome activity assay was performed by using the 20S proteasome assay kit. Ubiquitinated proteins were isolated and determined with ubiquitin enrichment kit. Results: Our results revealed that treatment of MM cell lines with BSc2118 inhibits the chymotrypsin-like proteasome activity and induces accumulation of ubiquitinated proteins. BSc2118 inhibits MM cell growth and induces MM apoptosis via induction of G2/M phase arrest, activation of cleaved caspase-3, caspase-8 and caspase-9 and PARP, increasing p53, p21 and E2F1, and inhibition of autophagy in MM.1S, MM.1R and RPMI-8226 cell lines. In addition, BSc2118 dramatically inhibits cytokines mRNA, such as IL-6, VEGF and bFGF in both myeloma cells line and primary bone marrow stromal cells from myeloma patients. More importantly, BSc2118 could overcome bortezomib resistance in vitro by using primary CD138 positive plasma cells from bortezomib-resistant myeloma patients and bortezomib resistance cell line ANBL-6 (ANBL-6.BR), most likely as the consequence of inhibition of autophagy flux which is responsible for bortezomib resistance. Conclusion: Our study revealed BSc2118, a novel irreversible proteasome inhibitor, exerts anti-MM effect, mainly through activation of caspase pathway and inhibition of basal autophagy. It is of great importance that BSc2118 could overcome bortezomib resistance via inhibition of autophagy flux. A head to head of BSc2118 versus Bortezomib is performing in human plasmacytoma xenograft tumor model to evaluate drug safety, anti-tumor efficiency, in particular, reversal of bortezomib resistance. Our preclinical study supports clinical evaluation of BSc2118, particularly, overcomes bortezomib resistance, as a potential MM therapy. Disclosures No relevant conflicts of interest to declare.

CD138 Regulates Myeloma Cell Survival, Proliferation, BM Engraftment and Tumor Organization

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2974-2974
Author(s):  
David R Fooksman ◽  
Amitabha Mazumder ◽  
Mark McCarron
Keyword(s):  
Plasma Cells ◽  
Conflicts Of Interest ◽  
Ex Vivo ◽  
Early Stage ◽  
Serum Starvation ◽  
High Dose ◽  
Rapid Reduction ◽  
Myeloma Cells

Abstract Multiple myeloma is the 2nd most common blood cancer in adults with a median survival time of 5 years despite high-dose chemotherapy and bone marrow transplantation interventions. Syndecan-1 or CD138, is a heparan-sulfate coated glycoprotein, which is highly expressed on the surface of plasma cells and myeloma cells, important for adhesion and accumulating survival signals. Expression of CD138 is heterogeneous in myeloma tumors, in vivo and in vitro leading some to speculate it may distinguish stem-like subpopulations. While this role is highly disputed, we investigated the effect of CD138 expression on tumor pathology in vivo. To characterize CD138neg and CD138high subpopulations, we used GFP+ Vk*myc myeloma model from Leif Bergsagel, which develops myeloma tumors in BM and spleen of C57Bl/6 mice. We found CD138high populations were more proliferative in vivo based on EdU incorporation experiments. We transferred equal numbers of sorted subpopulations into hosts and found that CD138high cells generated larger tumors in the BM than CD138neg cells after 12 weeks. Analysis of these tumor-bearing mice revealed that all tumors contained both subpopulations, indicating that these two subsets are hierarchically equivalent. We find that in mice with small tumors, the majority of cells (80% or more) are CD138high cells, while in large tumors, the level drops (to 30-50% of tumor) with higher composition of CD138neg cells. We also find lower CD138 levels on myeloma cells found in the blood compared to BM. Using intravital two-photon time-lapse imaging in the tibial BM, we find that tumor cells from smaller, early stage tumors are physically arrested within the BM parenchyma, while in larger, more advanced tumors, myeloma cells are more motile and active. CD138neg cells were more apoptotic based on ex vivo Annexin V staining following serum starvation. Interestingly, serum starvation led to rapid reduction in CD138 surface expression. Taken together, we propose a model where CD138 expression regulates localization and survival in the BM niche, but is downregulated from the plasma membrane when tumor size outgrows the necessary resources, allowing myeloma cells to migrate and metastasize to distant new locations. Disclosures No relevant conflicts of interest to declare.

HGF inhibits BMP-induced osteoblastogenesis: possible implications for the bone disease of multiple myeloma

Blood ◽  
2006 ◽  
Vol 109 (7) ◽  
pp. 3024-3030 ◽  
Author(s):  
Therese Standal ◽  
Niels Abildgaard ◽  
Unn-Merete Fagerli ◽  
Berit Stordal ◽  
Øyvind Hjertner ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Alkaline Phosphatase ◽  
Bone Formation ◽  
Bone Disease ◽  
Nuclear Translocation ◽  
Osteolytic Lesion ◽  
Bmp Signaling ◽  
Myoid Cell ◽  
Osteoblast Activity

AbstractThe bone disease in multiple myeloma is caused by an uncoupling of bone formation from bone resorption. A key difference between patients with and patients without osteolytic lesion is that the latter have fewer and less active osteoblasts. Hepatocyte growth factor (HGF) is often produced by myeloma cells and is found at high concentrations in the bone marrow of patients with multiple myeloma. Here we show that HGF inhibited bone morphogenetic protein (BMP)–induced in vitro osteoblastogenesis. Thus, HGF inhibited BMP-induced expression of alkaline phosphatase in human mesenchymal stem cells (hMSCs) and the murine myoid cell line C2C12, as well as mineralization by hMSCs. Furthermore, the expression of the osteoblast-specific transcription factors Runx2 and Osterix was reduced by HGF treatment. HGF promoted proliferation of hMSCs, and the BMP-induced halt in proliferation was overridden by HGF, keeping the cells in a proliferative, undifferentiating state. BMP-induced nuclear translocation of receptor-activated Smads was inhibited by HGF, providing a possible explanation of how HGF inhibits BMP signaling. The in vitro data were supported by the observation of a negative correlation between HGF and a marker of osteoblast activity, bone-specific alkaline phosphatase (rho = −0.45, P = .008), in sera from 34 patients with myeloma. These observations suggest that HGF inhibits bone formation in multiple myeloma.

scholarly journals Altering Glycosphingolipid Composition to Improve Multiple Myeloma Bone Complication

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1942-1942
Author(s):  
Houfu Leng ◽  
Adel Ersek ◽  
Emma Morris ◽  
Beatriz Gamez Molina ◽  
Claire M. Edwards ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Side Effects ◽  
Bone Disease ◽  
Bone Destruction ◽  
Germinal Centre ◽  
Nuclear Accumulation ◽  
Dependent Manner ◽  
Osteolytic Bone Disease ◽  
Hematological Cancers

Abstract Multiple myeloma (MM) is an incurable cancer of plasma cells (PC), with a median survival of 5-7 years. Osteolytic bone disease and skeletal complications occur in more than 80% of MM patients and significantly contribute to the morbidity and mortality of these patients. Glycosphingolipid (GSL), an essential constituent of the outer leaflet of the cellular membrane, is altered in MM and other hematological cancers. We previously reported that GM3, a subtype of GSL promotes osteoclastogenesis. On the other hand, the GSL synthase inhibitor N-butyl-deoxynojirimycin (NB-DNJ) reduces myeloma bone disease in the 5TGM1 mouse model of MM. Mechanistically, NB-DNJ prevents osteoclast (OC) development and activation by disrupting RANKL-induced localization of TRAF6 and c-SRC into lipid rafts and preventing nuclear accumulation of the transcriptional activator NFATc1. Although NB-DNJ is an FDA-approved drug treating Gaucher's disease, it has many undesired off-target effects, such as inhibiting lysosomal and plasma membrane Beta-glucocerebrosidase and interfering with intestinal glucosidases which leads to gastrointestinal toxicities and severe weight loss. Therefore, more specific GSL inhibitors are required to minimize the side effects. Here we report a novel GSL inhibitor called Genz112638 with comparable effects as NB-DNJ but reduced side effects. Genz112638 inhibits both OC formation (p < 0.01) and MM cell growth (p < 0.0001) in vitro in a dose-dependent manner. Moreover, compared to NB-DNJ, Genz112638 more significantly improved bone condition and potentially reduced MM burden, as evidenced by the amelioration of bone loss in the 5TGM1 model of myeloma, and a reduction in the proportion of MM within bone marrow and spleen without obvious adverse effects (n=6) (p < 0.01). As excessive malignant PC in MM normally arise from germinal centre, we also checked the effects of Genz112638 on germinal centre reactions in wildtype mice. We found that Genz112638 suppresses the formation of germinal centre B cells in mouse spleen induced by sheep red blood cells (n=7). Thus, Genz112638 may affect the pathogenesis of MM disease at the initial stage. Taken together, our data elucidate a novel specific GSL inhibitor as a promising candidate drug relieving two main features of MM: bone destruction and tumour burden with negligible side effects. In vitro, it decreases OC differentiation and proliferation, and meanwhile decreases MM viability and proliferation. In vivo, it may suppress B cell formation in germinal centre, ameliorate bone destruction, and potentially interfere with the vicious cycle between increased OC and susceptibility to MM. In short, we provide a preclinical platform for GSL inhibition as a new tool against MM and its related complications. Figure. Figure. Disclosures Horwood: Genzyme: Research Funding.

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