Partial characterization of an antigen from a human myeloma cell and its reactivity with an anti-myeloma cell serum.

This report describes studies carried out in an attempt to define the antibody specificity of a rabbit antiserum generated to the RPMI 8226 line of human myeloma cells and then isolate and characterize the antigen. The antiserum reacted to a significantly higher titer in a quantitative semi-micro complement fixation assay with RPMI 8226 cells as compared to the RPMI 4098 line of human lymphocytes or normal human bone-marrow cells, particularly after absorption with RPMI 4098 cells. A similar difference in reactivity was also noted for cell-free lysates of the three different types of cells. A variety of different procedures were carried out to attempt to solubilize the antigens of the RPMI 8226 cell. Of the procedures tried, deoxycholate treatment of sonicated or freeze-thaw extracts, 3 M KCI, autolysis and papain digestion were found to solubilize antigens from RPMI 8226 cells that reacted with anti-RPMI 8226 cell serum absorbed with RPMI 4098 cells. Further, the solubilized RPMI 8226 cell antigens did not react with an antiserum to RPMI 4098 cells. Components solubilized from RPMI 4098 cells by similar procedures did not react with the absorbed anti-RPMI 8226 cell serum to a significant titer. The initial studies carried out to characterize the components solubilized from the RPMI 8226 cell revealed that they were recovered in the included volume after gel filtration on Sephadex G-200 and that this material consisted of three proteins with approximate molecular weights of 66,000, 55,000 and 31,000 daltons as estimated by electrophoresis on SDS-acrylamide gels. These results indicate that the RPMI 8226 line of human myeloma cells possesses antigens not found on the RPMI 4098 line of human lymphocytes that can be solubilized and that react with an antiserum generated to intact RPMI 8226 cells.     

人类骨髓成纤维样基质细胞对多发性骨髓瘤细胞迁移和归巢特性的影响

 目的　观察人类骨髓成纤维样细胞系HFCL对多发性骨髓瘤细胞RPMI8226增殖、迁移和归巢的影响。方法　采用体外细胞培养,建立RPMI8226细胞和HFCL细胞共培养体系,锥虫蓝拒染法测定生长曲线;流式细胞术（FCM）检测细胞周期和黏附分子CD49d的变化;RT-PCR检测CXCR4基因的表达情况。结果　HFCL细胞抑制 RPMI8226细胞生长,且与HFCL细胞直接接触组的抑制作用大于非直接接触组（Transwell）组。RPMI8226细胞与HFCL细胞共培养后,直接接触组G1期细胞增高,S期细胞减少;HFCL细胞下调RPMI8226细胞的CXCR4和CD49d的表达,单独培养组明显高于直接培养组;Transwell组无明显变化。结论　人类骨髓成纤维样细胞HFCL能抑制多发性骨髓瘤细胞RPMI8226的增殖,抑制CXCR4和CD49d的表达,影响骨髓瘤细胞的迁移和归巢。     

Survivin基因调控Notch1信号通路抑制骨髓瘤细胞增殖及侵袭的机制

目的 探讨Survivin基因调控Notch1信号通路对骨髓瘤细胞增殖及侵袭的影响.方法 RT-PCR检测42例骨髓瘤组织及正常骨髓组织中Survivin基因的mRNA表达;NC-siRNA和Survivin-siRNA转染人骨髓瘤细胞株RPMI8226,Western blot检测48 h后各组细胞中Survivin蛋白的表达;台盼蓝拒染法和Transwell小室分别检测细胞活率及侵袭能力;Western blot检测MMP-2、MMP-9、Notch1、Hes1蛋白的表达.结果 Survivin基因在骨髓瘤组织中的mRNA表达显著高于正常骨髓组织(P﹤0.01);转染siRNA后RPMI8226细胞中Survivin蛋白的表达显著降低(P﹤0.01);与对照组及NC-siRNA组的比较,Survivin-siRNA组细胞活率、细胞侵袭数及MMP-2、MMP-9、Notch1、Hes1蛋白表达均显著降低(P﹤0.01).结论 RNA干扰Survivin基因的表达可降低RPMI8226细胞活率及侵袭能力,其机制与抑制Notch1信号通路有关.     

Selective depletion of human myeloma clonogenic stem cells from bone marrow cell preparations by a plasma-cell reactive antibody and complement

The monoclonal antibody MM4 reacts with human myeloma cells from plasma cell dyscrasia (PCD)-derived cell lines and bone marrow (BM) biopsies from PCD patients, but not with normal BM or peripheral blood mononuclear (PBM) cells. We examined cytotoxicity of MM4 and rabbit complement (MM4:C') on mixtures of normal BM mononuclear cells and myeloma cells from three different PCD-derived cell lines, RPMI 8226, GM 1312, or ARH-77. For cell preparations containing 10% myeloma cells, treatment with MM4 (500 micrograms per 10(5) cells, 4 degrees C, 60 min) and two cycles of complement (1:8, 23 degrees C, 2 x 30 min) consistently eliminated 2 logs or more of clonogenic myeloma stem cells, as determined by colony growth assays and limiting dilution analysis (99.4%, 98.9%, and 99.96% reduction of RPMI 8226, GM 1312, and ARH-77 cells, respectively). The majority of normal marrow progenitors were spared (inhibition of CFU-C: 10-13%; BFU-E: 0%). These observations suggest that MM4 may be useful for selective depletion of human myeloma clonogenic stem cells from bone marrow ex vivo.     

细胞融合在多发性骨髓瘤骨病发病机制中的作用探讨

目的 探讨人骨髓基质细胞与人骨髓瘤细胞株RPMI 8226的融合细胞在多发性骨髓瘤骨病发病过程中可能的机制.方法 细胞示踪绿色荧光探针(CMFDA)及红色荧光探针(CMTMR)分另别标记的细胞通过化学促融剂聚乙二醇(PEG-1000)诱导融合,建立细胞融合模型.染色体核型分析,确定融合细胞是否发生细胞核的融合;鉴定融合细胞干性基因及促融相关性基因SIRPα、DC-STAMP的表达情况.结果 PEG-1000能够介导骨髓基质细胞与RPMI 8226细胞融合;超过80％的融合细胞染色体数目在80条左右;融合细胞不仅表现出骨髓基质细胞的特征及干性相关基因c-myc、Klf-4、OCT-4表达阳性,而且融合相关性基因SIRP α及DC-STAMP也表达阳性.结论 骨髓基质细胞与RPMI 8226细胞间可形成融合细胞,融合细胞具有进一步成融的潜力,可能是促进多发性骨髓瘤骨破坏的重要原因之一.     

Establishment of lymphomatous cell lines from bone marrow samples from patients with Burkitt's lymphoma

A total of 233 bone marrow aspirates were obtained from 43 patients with Burkitt's lymphoma (BL). Lymphoma cells were absent and lymphoblastoid cell lines could not be established from 197 samples, which were characterized by limited initial cell proliferation and development of an adherent population, followed by cell death after 2-4 weeks. In 14 aspirates, after a similar pattern of growth, cell proliferation began again after about 6 weeks, with a rapid appearance and growth of cell clumps from the feeder layer--a type of growth typical of spontaneous lymphoblastoid cell lines. In 22 aspirates, growth of malignant cells was observed in culture and cytocentrifuged, stained smears, including marrow samples from 9 patients in whom the presence of BL cells had not been ascertained or even suspected by cytology. Karyotypic anomalies characteristic of BL were found in these cells: t(8;14) in the majority, two t(8;22), two t(2;8), and one t(2;8;9).     

Multiple myeloma regression mediated by bruceantin.

PURPOSE: Bruceantin has been shown to induce cell differentiation in a number of leukemia and lymphoma cell lines. It also down-regulated c-MYC, suggesting a correlation of down-regulation with induction of cell differentiation or cell death. In the present study, we focused on multiple myeloma, using the RPMI 8226 cell line as a model. EXPERIMENTAL DESIGN: The effects of bruceantin on c-MYC levels and apoptosis were examined by immunoblotting, 4',6-diamidino-2-phenylindole staining, evaluation of caspase-like activity, and 3,3'-dihexyloxacarbocyanine iodide staining. The potential of bruceantin to inhibit primary tumor growth was assessed with RPMI 8226 xenografts in SCID mice, and apoptosis in the tumors was evaluated by the terminal deoxynucleotidyl transferase-mediated nick end labeling assay. RESULTS: c-MYC was strongly down-regulated in cultured RPMI 8226 cells by treatment with bruceantin for 24 h. With U266 and H929 cells, bruceantin did not regulate c-MYC in this manner. Apoptosis was induced in the three cell lines. In RPMI 8226 cells, apoptosis occurred through proteolytic processing of procaspases and degradation of poly(ADP-ribose) polymerase. The mitochondrial pathway was also involved. Because RPMI 8226 cells were the most sensitive, they were used in a xenograft model. Bruceantin treatment (2.5-5 mg/kg) resulted in a significant regression of tumors without overt toxicity. Apoptosis was significantly elevated in tumors derived from animals treated with bruceantin (37%) as compared with the control tumors (14%). CONCLUSIONS: Bruceantin interferes with the growth of RPMI 8226 cells in cell culture and xenograft models. These results suggest that bruceantin should be reinvestigated for clinical efficacy against multiple myeloma and other hematological malignancies.     

Granulocyte colony stimulating factor-producing multiple myeloma associated with neutrophilia

We report a case of IgG-kappa multiple myeloma associated with neutrophilia (WBC 31,300/microl, neutrophil 90.5%). Interestingly, the serum level of granulocyte colony stimulating factor (G-CSF) in this patient was elevated to 1,500 pg/ml (normal range: 5.78-27.5). Plasma cells were 35% in the bone marrow and were strongly stained with anti-G-CSF antibody. To directly study the production of G-CSF from plasma cells in this patient, CD138 positive plasma cells were purified from bone marrow of multiple myeloma patients by magnetic sorting. The expression of G-CSF mRNA was observed in CD138 positive plasma cells from this myeloma patient with neutrophilia by RT-PCR. In contrast, the expression of G-CSF mRNA was not detected in CD138 positive plasma cells from the other multiple myeloma patients without neutrophilia and 4 human myeloma cell lines (HS-Sultan, IM9, RPMI8226, U266) by RT-PCR. After the CD138 positive plasma cells were cultured in vitro for 48 h, the production of G-CSF protein was confirmed (71.8 pg/ml) in the supernatant by ELISA. These results indicated plasma cells of this myeloma patient directly produced G-CSF and that this was the primary cause of neutrophilia.     

Production of growth factors by human myeloma cells

Using in vitro-growing myeloma cell lines, we studied the growth factors involved in human multiple myeloma, and particularly the potential of autocrine secretion and response to B-cell growth factor (BCGF) of RPMI 8226, the best-documented Epstein-Barr virus-negative human myeloma cell line. We found that three myeloma cell lines (RPMI 8226, U266, and IM9) produce an autostimulatory growth factor (AGF) and thus increase their own proliferation by 2- to 3-fold in cells cultured at low density. Optimal AGF production was obtained after 24 h of culture at a cell density ranging from 2.5 to 5 million cells/ml. The three myeloma cell lines produce type II BCGF, able to induce the proliferation of highly purified human peripheral blood B-cells, only after anti-mu activation. The BCGF produced by RPMI 8226 can be absorbed onto RPMI 8226 cells together with the RPMI 8226 AGF, and the two are copurified on gel filtration in a peak with an apparent molecular weight of 70,000. RPMI 8226 can be efficiently activated by human high molecular weight BCGF II (Mr 50,000) and less extensively by BCGF I (Mr 12,000). RPMI 8226 does not produce either detectable IL1 or interferons gamma and alpha and IL1 and gamma-IFN had no stimulating effect on RPMI 8226 proliferation. Our findings support the conclusion that RPMI 8226 produces a BCGF II working as an AGF.     

Matrix metalloproteinases-1 and -2, and tissue inhibitor of metalloproteinase-2 production is abnormal in bone marrow stromal cells of multiple myeloma patients

We have investigated the production of metalloproteinases (MMP-1, MMP-2, MMP-9) and tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) in bone marrow stromal cells (BMSCs) of patients with multiple myeloma (MM) and a healthy control. The new findings of this paper is that BMSCs of the MM patients exhibited intrinsic MMP-1, MMP-2 and TIMP-2 overproduction. Production of MMP-1, TIMP-2 and activation of MMP-2 was additionally enhanced in co-cultures of BMSCs with RPMI8226 cells. The ratio between MMP-2 and TIMP-2 was significantly higher in BMSCs of the MM patients than in control. BMSCs of both the control and the MM patients exhibited the presence of MMP-9 latent form, but in co-cultures RPMI8226 cells were the main producers of this metalloproteinase.     

RNA干扰抑制FANCD2基因对多药耐药骨髓瘤细胞株药物敏感性的影响

目的：探讨FA/BRCA（fanconi anemia/BRCA）中siRNA干扰对多药耐药骨髓瘤细胞株的影响.方法：体外培养多发性骨髓瘤细胞RPMI-8226细胞系,通过相应渐增浓度的马法兰药物处理,选择性获得多药耐药的子代肿瘤细胞株RPMI-8226/R细胞.MTT法检测RPMI-8226和RPMI-8226/R细胞马法兰、ADM、VCR、CTX、Ara-C、VP-16及DDP的敏感性.siRNA干扰抑制FA/BRCA途径FANCD2蛋白表达,观察多发性骨髓瘤多药耐药细胞株对烷化剂药物敏感性的变化.结果：成功构建针对FANCD2基因的siRNA,将其转染多药耐药骨髓瘤细胞株,可以抑制细胞中FANCD2基因表达,转染细胞较转染前细胞FANCD2基因表达降低,对烷化剂的敏感性升高.结论：人多发性骨髓瘤多药耐药细胞株RPMI-8226/R其多药耐药性的产生可能与FA/BRCA途径中FANCD2表达增强有关,可通过抑制FANCD2表达而逆转细胞的耐药性达到增强烷化剂对耐药肿瘤细胞的增殖抑制及诱导凋亡作用.沉默FANCD2表达可以提高多药耐药MM细胞对烷化剂的敏感性,而RNA干扰是一种沉默FANCD2表达的理想方法,因此它可能是一种有潜力的耐药MM辅助治疗新方法.     

三七总皂甙对多发性骨髓瘤细胞的增殖抑制作用及机制的研究

目的：观察三七总皂甙（PNS）对多发性骨髓瘤RPMI8226细胞增殖抑制的作用;并观察三七总皂甙与阿霉素（adriamycin,ADM）联合,是否具有协同效应,为三七总皂甙应用于多发性骨髓瘤临床治疗提供一定的实验依据。方法：MTT法检测三七总皂甙对RPMI8226细胞增殖的影响;运用金氏公式分析三七总皂甙与ADM联合的协同效应;RT-PCR法检测Bcl-2、Bax mRNA水平的变化。结果：三七总皂甙可抑制RPMI8226细胞的增殖,并呈剂量依赖性,24h IC50值为213.42±2.21μg/ml;三七总皂甙与ADM联合,表现出协同效应;三七总皂甙与ADM联合处理MM细胞24h后,Bcl-2 mRNA表达较单独应用三七总皂甙或ADM前明显下调,而Bax表达则明显上调。结论：三七总皂甙可以抑制多发性骨髓瘤细胞增殖,联合阿霉素,具有协同效应;其作用可能是通过下调Bcl-2,上调Bax在转录水平的表达而实现的。     

FANCF基因沉默增强多药耐药多发性骨髓瘤细胞株RPMI8226/R对马法兰的敏感性

目的:使用小片段干扰RNA（siRNA）沉默FANCF基因表达,观察其对FA/BRCA途径的影响及对多药耐药多发性骨髓瘤细胞株RPMI8226/R对交联剂马法兰的敏感性变化。方法:FANCF siRNA瞬时转染多药耐药细胞株RPMI8226/R,采用CCK-8法检测转染前后细胞对马法兰的敏感性变化,RT-PCR,western-blot法检测FA/BRCA途径中FANCF、FANCD2、BRCA2基因表达量的改变,彗星实验检测DNA损伤,流式细胞仪检测细胞凋亡率。结果:FANCF siRNA转染耐药骨髓瘤细胞后,对马法兰的IC50值由17.29μmol/L降至4.88μmol/L;western-blot检测出瞬时转染FANCF siRNA后FA/BRCA途径中FANCF、FANCD2、BRCA2 蛋白表达量明显较转染前减低;彗星实验检测出转染后耐药细胞的DNA损伤增多;转染后马法兰诱导细胞凋亡率由（77.67±0.62）%升高至（88.37±0.25）%,提示FANCF基因沉默可使耐药RPMI8226/R细胞对化疗药物马法兰重新恢复敏感性。结论:FANCF基因沉默可抑制FA/BRCA途径中FANCD2及下游BRCA2基因表达,从而阻断FA/BRCA途径介导的DNA修复,增强马法兰对多药耐药骨髓瘤细胞株RPMI8226/R的细胞毒性,增加细胞凋亡率,为解决临床耐药问题提供一个新的思路。     

Elimination of chemoresistant multiple myeloma clonogenic colony-forming cells by combined treatment with a plasma cell-reactive monoclonal antibody and a P-glycoprotein-reactive monoclonal antibody

Patients with multiple myeloma (MM) commonly become refractory to chemotherapy despite a favorable response to induction treatment. We examined the effectiveness of a previously characterized plasma cell-reactive monoclonal antibody, MM4, in eliminating MM clonogenic colony-forming cells (CCC) with a multidrug-resistant (MDR) phenotype. Experiments were performed using MM cell lines that exhibit 6 (RPMI 8226/DOX6)- and 40 (RPMI 8226/DOX40)-fold resistance to doxorubicin (DOX). Both lines were selected from the chemosensitive MM line RPMI 8226/S and were cross-resistant to mitoxantrone, acronycine, etoposide, and vincristine. Surface marker analysis conducted in this study showed that DOX6 and DOX40 overexpressed the MDR1 gene product p170. Both MDR lines remained reactive to the plasma cell-reactive monoclonal antibodies MM4 and PCA-1 and expressed the relevant cytoplasmic immunoglobulin light chain. Treatment with MM4 and rabbit complement (C') was equally cytotoxic to RPMI 8226/S [80 +/- 5.6% (SD)], DOX6 [74 +/- 8.5], and DOX40 cells [75 +/- 11.3%], based on short-term chromium release studies. Furthermore, MM4 + C' deleted up to 3 logs of CCC colonies from chemosensitive and MDR lines (RPMI 8226/S, 99.87 +/- 0.11%; DOX6, 99.91 +/- 0.08%; DOX40, 99.55 +/- 0.44%). By comparison, the P-glycoprotein-reactive monoclonal antibody MRK-16 and C' inhibited tumor colony formation of MDR cells (8226/DOX6, 95.71 +/- 2.51%; 8226/DOX40, 99.61 +/- 0.43%) but affected that of chemosensitive cells only slightly (8.9 +/- 17.8%). In an attempt to optimize the depletion of myeloma CCC, MM4 was used together with MRK-16. This approach resulted in uniform depletion of myeloma clonogenic colony-forming cells from the chemosensitive (98.32 +/- 1.53%, n = 4) and MDR lines (8226/DOX6, 98.83 +/- 0.08%, n = 4; 8226/DOX40 99.29 +/- 0.62, n = 7) but did not result in enhanced CCC depletion. When DOX40 cells were mixed with normal bone marrow (BM) in the ratio of 90:10 (BM:MM), either MM4 or MRK-16 and C' depleted MM colonies (98.8 +/- 0.71% and 98.10 +/- 1.0%, respectively) without affecting the majority of BM progenitor cells. These observations suggest that either MM4 or MRK-16 is useful for depleting MDR myeloma clonogenic colony-forming cells.     

Pharmacological elimination of tumor cells contaminating normal human bone marrow using PTT-119

In this study, we evaluated the inhibitory effects of PTT-119, a new tripeptide which is known to be a bifunctional alkylating agent, on two tumor cell lines with different origins: SK-DHL-2 (B-cell diffuse histiocytic lymphoma cell line) and RPMI 8226 (Multiple myeloma patient cell line) and compared the toxicity of PTT-119 toward normal human bone marrow granulocyte macrophage (CFU-GM), erythroid (BFU-E), and pluripotent (CFU-GEM) progenitors. Reduction of at least four logs was achieved on clonogenic myeloma cells after 1 hr of treatment with 25 micrograms/mL of PTT-119 either in the presence or absence of irradiated bone marrow (BM) cells. More than three and at least four logs of lymphoma cell kill were found after 1 hr of incubation with 25 and 40 micrograms/mL of the tripeptide, respectively. PTT-119 antitumor effects on SK-DHL-2 were only slightly affected in the presence of an excess of BM cells. BM cells treated for 1 hr with 25 micrograms/mL of PTT-119 showed a mean recovery of 4.5, 3.8, and 13.8% of CFU-GM, BFU-E, and CFU-GEM, respectively. The addition of 5- and 10-fold excesses of red blood cells (RBC) produced a slightly higher recovery of these hematopoietic progenitors. These results suggest that PTT-119 may be useful as a chemotherapeutic agent for the ex vivo treatment of bone marrow grafts.     

Habb-e-Asgandh Suppresses Cell Proliferation and Induces Apoptosis through Mitochondria Dysfunction in Multiple Myeloma Cells (RPMI8226)

Objective: This study was conducted to assess the anti-neoplastic properties of Habb-e-Asgandh in multiple myeloma cells (RPMI8226). Methods: Multiple myeloma cells (RPMI8226) were cultured according to the ATCC’s instruction. The anti-proliferative effect of HeA was assessed by MTT assay and proliferating cellnuclear antigen (PCNA) activity. Cell cycle analysis, cellular apoptosis, and mitochondria membrane potential analysis was done by flow cytometry. Total antioxidants, migratory potential, angiogenesis and inflammatory biomarkers were also estimated after treatment of RPMI8226 with HeA. Results: LD30 and LD50 dose of HeA was 0.3mg/ml and 0.5mg/ml respectively determined by MTT assay and also confirmed by a reduced PCNA activity. Cell cycle analysis of RPMI8226 cells revealed that sub-G0/G1 phase increases upon treatment with HeA alone or in combination with lenalidomide. Annexin V-FITC/PI is used to detect early apoptosis, late apoptosis and necrotic cells and results showed that percentage of apoptotic cells increased in RPMI8226 cells after treatment with HeA. Also, HeA induces loss of mitochondria membrane potential (MMP) in MM cells in-vitro as measured by cationic JC1 dye staining. Upon treatment, the abnormal overexpression of oncogenic protein, AKT serine/threonine kinase has also been reduced. Furthermore, anti-oxidants level also increased while migratory potential, angiogenesis and inflammation decreased in multiple myeloma cell line upon treatment with HeA. Conclusion: Collectively, our results demonstrated that integrative therapy of habb-e-asgandh efficiently eliminates the need to use higher dose of lenalidomide for multiple myeloma treatment.     

Paclitaxel‐releasing mesenchymal stromal cells inhibit the growth of multiple myeloma cells in a dynamic 3D culture system

Multiple myeloma is an aggressive tumour able to suppress osteoblastogenesis probably mediated by bone marrow mesenchymal stromal cells (BM‐MSCs) that can also support plasma cell growth/survival. The use of MSCs for multiple myeloma therapy is a controversial topic because of the contradictory results on the capacity of MSCs to inhibit or to promote cancer growth. Our previous studies demonstrated that MSCs could be loaded with Paclitaxel (PTX) and used to deliver the drug in situ in amount affecting tumour growth (in vitro and in vivo). Therefore, independently on the discussed action of MSCs in myeloma, MSCs could represent a ‘trojan horse’ to vehicle and deliver anti‐tumour agents into bone marrow. This study confirms, by an in vitro 3D dynamic culture system, that PTX loaded BM‐MSCs (PTXr‐MSCs) are active on the proliferation of RPMI 8226, a human myeloma cell line. Our results demonstrated a dramatic suppression of myeloma cell growth by PTXr‐MSCs, suggesting that drug loaded MSCs could be a tool to deliver drug into the bone marrow. Drug releasing MSCs provide a therapeutic approach to potentiate the existing treatments against a very aggressive malignancy as multiple myeloma. Copyright © 2016 John Wiley & Sons, Ltd.     

Gene silencing of the BDNF/TrkB axis in multiple myeloma blocks bone destruction and tumor burden in vitro and in vivo

Osteolytic bone diseases are a prominent feature of multiple myeloma (MM), resulting from aberrant osteoclastic bone resorption that is uncoupled from osteoblastic bone formation. Myeloma stimulates osteoclastogenesis, which is largely dependent on an increase in receptor activator of NF‐κB ligand (RANKL) and a decrease in osteoprotegerin (OPG) within the bone marrow milieu. Recently, brain‐derived neurotrophic factor (BDNF) was identified as a MM‐derived factor that correlates with increased RANKL levels and contributes to osteolytic bone destruction in myeloma patients. Because tyrosine receptor kinase B (TrkB), the receptor of BDNF, is abundantly expressed in osteoblasts, we sought to evaluate the role of BDNF/TrkB in myeloma–osteoblast interactions and the effect of this pathway on the RANKL/OPG ratio and osteoclastogenesis. Coculture systems constructed with noncontact transwells revealed that, in vitro, MM‐derived BDNF increased RANKL and decreased OPG production in osteoblasts in a time‐ and dose‐dependent manner. These effects were completely abolished by a specific small interfering RNA for TrkB. BDNF regulates RANKL/OPG expression in osteoblasts through the TrkB/ERK pathway. To investigate the biological effects of BDNF on myeloma in vivo, a SCID‐RPMI8226 mice model was constructed using lentiviral short hairpin RNA‐transfected RPMI8226 cells. In this system, stable knockdown of BDNF in MM cells significantly restored the RANKL/OPG homostasis, inhibited osteolytic bone destruction and reduced angiogenesis and tumor burden. Our studies provide further support for the potential osteoclastogenic effects of BDNF, which mediates stroma–myeloma interactions to disrupt the balance of RANKL/OPG expression, ultimately increasing osteoclastogenesis in MM.