scholarly journals The Role of Marrow Microenvironment in the Growth and Development of Malignant Plasma Cells in Multiple Myeloma

2021 ◽  
Vol 22 (9) ◽  
pp. 4462
Author(s):  
Nikolaos Giannakoulas ◽  
Ioannis Ntanasis-Stathopoulos ◽  
Evangelos Terpos
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Stromal Cells ◽  
Genetic Background ◽  
Growth And Development ◽  
Plasma Cells ◽  
Critical Role ◽  
Bone Marrow Microenvironment ◽  
Myeloma Cells

The development and effectiveness of novel therapies in multiple myeloma have been established in large clinical trials. However, multiple myeloma remains an incurable malignancy despite significant therapeutic advances. Accumulating data have elucidated our understanding of the genetic background of the malignant plasma cells along with the role of the bone marrow microenvironment. Currently, the interaction among myeloma cells and the components of the microenvironment are considered crucial in multiple myeloma pathogenesis. Adhesion molecules, cytokines and the extracellular matrix play a critical role in the interplay among genetically transformed clonal plasma cells and stromal cells, leading to the proliferation, progression and survival of myeloma cells. In this review, we provide an overview of the multifaceted role of the bone marrow microenvironment in the growth and development of malignant plasma cells in multiple myeloma.

The Relationship of Myeloma Cells, Stromal Cells and Monocytes Under Bone Marrow Microenvironment

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 4987-4987
Author(s):  
Hiroshi Ikeda ◽  
Yuka Aoki ◽  
Nasanori Nojima ◽  
Hiroshi Yasui ◽  
Toshiaki Hayashi ◽  
...  
Keyword(s):  
Stem Cells ◽  
Multiple Myeloma ◽  
Bone Marrow ◽  
Cell Proliferation ◽  
Stromal Cells ◽  
Bone Marrow Stromal Cells ◽  
Marrow Stromal Cells ◽  
Myeloma Cells ◽  
Growth And Survival

Abstract Abstract 4987 The Bone marrow (BM) microenvironment plays crucial role in pathogenesis of Multiple myeloma(MM). Myeloma cells contacts with bone marrow stromal cells (BMSCs), which secrete factors/cytokines, promoting tumor cell growth and survival. Paracrine secretion of cytokines(i. e., interleukin-6 (IL-6) insulin-like growth factor-1, inflammatory protein-1a) in BM stromal cells promotes multiple myeloma cell proliferation and protects against drug-induced cytotoxicity. These cytokines provide stimulatory signals for multiple myeloma growth and survival. Bone involvement is a common feature in MM patient, solid and hematologic cancers. MM localizes to the bone in nearly all patients ranges between 40% and 75%. Disease-related skeletal complications result in significant morbidity due to pain, pathologic fractures and spinal cord compression. The bone microenvironment creates a supportive niche for tumor growth. Osteoclasts and bone marrow stromal cells, along with extracellular matrix and cytokines stimulate tumor cell proliferation and confer chemoresistance. Therefore, the reciprocal interactions between tumor cells, osteoclasts, osteoblasts, and bone marrow stromal cells present an important. In current study, monocyte can directly promote mesenchymal stem cells osteogenic differentiation through cell contact interactions, thus resulting in the production of osteogenic factors by the monocytes. This mechanism is mediated by the activation of STAT3 signaling pathway in the mesechymal stem cells that leads to the upregulation of Osteoblasts-associated genes such as Runx2 and alkaline phosphatase (ALP), and the down-regulation of inhibitors such as DKK1 to drive the differentiation of mesechymal stem cells into osteoblasts. In this study, we examined the role of monocyte, component of BM cells, as a potential niche component that supports myeloma cells. We investigated the proliferation of MM cell lines cultured alone or co-cultured with BM stromal cells, monocytes, or a combination of BM stromal cells and monocytes. Consistently, we observed increased proliferation of MM cell lines in the presence of either BM stromal cells or monocytes compared to cell line-only control. Furthermore, the co-culture of BM stromal cells plus monocytes induced the greatest degree of proliferation of myeloma cells. In addition to increased proliferation, BMSCs and monocytes decreased the rate of apoptosis of myeloma cells. Our results therefore suggest that highlights the role of monocyte as an important component of the BM microenvironment. Disclosures: No relevant conflicts of interest to declare.

In the presence of bone marrow stromal cells human multiple myeloma cells become independent of the IL-6/gp130/STAT3 pathway

Blood ◽  
2002 ◽  
Vol 100 (9) ◽  
pp. 3311-3318 ◽  
Author(s):  
Manik Chatterjee ◽  
Dirk Hönemann ◽  
Suzanne Lentzsch ◽  
Kurt Bommert ◽  
Christine Sers ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Stromal Cells ◽  
Bone Marrow Stromal Cells ◽  
Marrow Stromal Cells ◽  
Myeloma Cells ◽  
Farnesyl Transferase ◽  
Stat3 Pathway ◽  
Induced Apoptosis

AbstractThe interleukin 6/glycoprotein 130/signal transducer and activator of transcription 3 (IL-6/gp130/STAT3) pathway has been reported to play an important role in the pathogenesis of multiple myeloma (MM) and for survival of MM cells. However, most data concerning the role of IL-6 and IL-6–triggered signaling pathways were obtained from experiments performed with MM cell lines and without considering the bone marrow microenvironment. Thus, the precise role of IL-6 and its intracellular signaling pathways for survival of human MM cells is still unclear. Here we show that treatment of human MM cells (IL-6–dependent MM cell line INA-6 and primary MM cells) with the IL-6 receptor antagonist Sant7 or with an anti-gp130 monoclonal antibody (mAb) induced apoptosis if the cells were cultured in the absence of bone marrow stromal cells (BMSCs). In contrast, apoptosis could not be observed if the MM cells were cocultured with BMSCs. The analysis of intracellular pathways revealed that Sant7 and anti-gp130 mAb were effectively inhibiting the phosphorylation of gp130 and STAT3 in the absence and presence of BMSCs, whereas ERK1 and ERK2 (ERK1,2) phosphorylation was only slightly affected. In contrast, treatment with the farnesyl transferase inhibitor, FPT III, induced apoptosis in MM cells in the absence or presence of BMSCs and led to a complete inhibition of the Ras/mitogen-activated protein kinase pathway. These observations indicate that the IL-6/gp130/STAT3 pathway is not essential for survival of human myeloma cells if they are grown in the presence of cells from the bone marrow microenvironment. Furthermore, we provide evidence that farnesyl transferase inhibitors might be useful for the development of novel therapeutic strategies for the treatment of MM.

scholarly journals Immunological Dysregulation in Multiple Myeloma Microenvironment

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Alessandra Romano ◽  
Concetta Conticello ◽  
Maide Cavalli ◽  
Calogero Vetro ◽  
Alessia La Fauci ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Stromal Cells ◽  
Plasma Cells ◽  
Clinical Manifestations ◽  
Suppressor Cells ◽  
Matrix Proteins ◽  
Host Immune System ◽  
Hematologic Disease

Multiple Myeloma (MM) is a systemic hematologic disease due to uncontrolled proliferation of monoclonal plasma cells (PC) in bone marrow (BM). Emerging in other solid and liquid cancers, the host immune system and the microenvironment have a pivotal role for PC growth, proliferation, survival, migration, and resistance to drugs and are responsible for some clinical manifestations of MM. In MM, microenvironment is represented by the cellular component of a normal bone marrow together with extracellular matrix proteins, adhesion molecules, cytokines, and growth factors produced by both stromal cells and PC themselves. All these components are able to protect PC from cytotoxic effect of chemo- and radiotherapy. This review is focused on the role of immunome to sustain MM progression, the emerging role of myeloid derived suppressor cells, and their potential clinical implications as novel therapeutic target.

scholarly journals 'Role of bone marrow stromal cells in the growth of human multiple myeloma

Blood ◽  
1991 ◽  
Vol 77 (12) ◽  
pp. 2688-2693 ◽  
Author(s):  
F Caligaris-Cappio ◽  
L Bergui ◽  
MG Gregoretti ◽  
G Gaidano ◽  
M Gaboli ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
B Lymphocytes ◽  
Stromal Cells ◽  
Mononuclear Cells ◽  
Plasma Cells ◽  
Critical Role ◽  
Peripheral Blood Mononuclear ◽  
Human Multiple Myeloma

We have verified the hypothesis that multiple myeloma (MM) may be disseminated by circulating clonogenic cells that selectively home to the bone marrow (BM) to receive the signal(s) leading to proliferation, terminal differentiation, and production of the osteoclast activating factors. Long-term cultures of stromal cells have been developed from the BM of nine patients with MM. These cells were mostly fibroblast- like elements, interspersed with a proportion of scattered macrophages and rare osteoclasts. BM stromal cells were CD54+, produced high levels of interleukin-6 (IL-6) and measurable amounts of IL-1 beta, and were used as feeder layers for autologous peripheral blood mononuclear cells (PBMC). After 3 weeks of cocultures, monoclonal B lymphocytes and plasma cells, derived from PBMC, developed and the number of osteoclasts significantly increased. Both populations grew tightly adherent to the stromal cell layer and their expansion was matched by a sharp increase of IL-6 and by the appearance of IL-3 in the culture supernatant. These data attribute to BM stromal cells a critical role in supporting the growth of B lymphocytes, plasma cells, and osteoclasts and the in vivo dissemination of MM.

scholarly journals The role of bone marrow microenvironment in the progression of multiple myeloma from monoclonal gammopathy of undetermined significance

2021 ◽  
Vol 16 (3) ◽  
pp. 26-32
Author(s):  
A. S. Khudovekova ◽  
Ya. A. Rudenko ◽  
A. E. Dorosevich
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Monoclonal Gammopathy ◽  
Plasma Cells ◽  
Bone Marrow Microenvironment ◽  
Genetic Mutations ◽  
Microbiome Composition ◽  
The Impact ◽  
Undetermined Significance

Multiple myeloma is a tumor of plasma cells, one of the most common malignant blood diseases. It is preceded by a stage called monoclonal gammopathy of undetermined significance, from which true multiple myeloma develops in only a small percentage of cases. It was assumed that this process is associated with the accumulation of genetic mutations, but in recent years there is increasing evidence that the bone marrow microenvironment plays a key role in progression and that it can become a target for therapy that prevents the myeloma development. The review considers the role of mesenchymal stem cells, immune system cells, endotheliocytes, fibroblasts, adipocytes, osteoclasts and osteoblasts in multiple myeloma progression, as well as the impact of the sympathetic nervous system and microbiome composition.

Angiogenesis in Multiple Myeloma (MM): Angiogenic Switch or Reflexion of Plasma Cell Number? A Gene Expression Based Survey in Primary Myeloma Cells and the Bone Marrow Microenvironment.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3405-3405
Author(s):  
Dirk Hose ◽  
John DeVos ◽  
Christiane Heiß ◽  
Jean-Francois Rossi ◽  
Angela Rösen-Wolff ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Plasma Cell ◽  
Empirical Bayes ◽  
Plasma Cells ◽  
De Novo ◽  
Cell Number ◽  
Bone Marrow Microenvironment ◽  
Myeloma Cells ◽  
Angiogenic Switch

Abstract BACKGROUND. Angiogenesis is a hallmark of active multiple myeloma. However, two etiologic hypotheses have been proposed: an angiogenic switch (i.e. differential or de novo expression of pro/antiangiogenic genes in MM), and, alternatively an effect of increased plasma cell number. AIM of this study was to investigate the angiogenic signature of multiple myeloma cells (MMC), normal bone marrow plasma cells (BMPC), the bone marrow microenvironment (BMME) and cellular subfractions therein. PATIENTS AND METHODS. 128 newly diagnosed MM-patients (65 training (TG) / 63 independent validation group (VG)) and 14 normal donors (ND) were included. Bone marrow aspirates were CD138-purified by activated magnetic cell sorting. Whole bone marrow (n=49) and FACSAria sorted subfractions thereof (n=5) were investigated. RNA was in-vitro transcribed and hybridised to Affymetrix HG U133 A+B GeneChip (TG) and HG U133 2.0 plus arrays (VG). Expression data were gcrma-normalised and the empirical Bayes algorithm used. p-Values were adjusted using the Benjamini-Hochberg method (Bioconductor). iFISH was performed on purified MM-cells using probesets for chromosomes 1q21, 9q34, 11q23, 11q13, 13q14, 15q22, 17p13, 19q13, 22q11 and the translocations t(4;14) and t(11;14). HGF expression was verified by real time RT-PCR and western blotting. Based on Medline review, we established a list of 89 pro- and 56 antiangiogenic genes and investigated their expression according to the stage of disease: BMPC vs. MGUS, SD stage I (asymptomatic myeloma) vs. SD stage II/III (symptomatic myeloma requiring therapy). RESULTS. BMPC express pro- (e.g. VEGFA) and antiangiogenic genes (e.g. TIMP2). Only one pro-angiogenic gene (hepatocyte growth factor, HGF) is significantly overexpressed in MMC compared to BMPC. HGF has previously been linked with myeloma progression and induction of angiogenesis. Six antiangiogenic genes (TIMP2, SERPINF1, COL18A1, PF4, THBS1, CXCL14) are downregulated in MMC compared with BMPC. Compared to healthy donors, the BMME of MM shows a significant downregulation of PLAU (urokinase, antiangiogenic) and upregulation of TNF(proangiogenic). CONCLUSION. Upregulation of HGF-expression, downregulation of TIMP2, SERPINF1, COLA18A1, PF4, THBS1 and CXCL14 expression in MMC as well as downregulation of PLAU and upregulation of TNFα in the BMME seem to indicate an “angiogenic switch”. However, given the relatively low number of differentially expressed genes (7/145) and the expression of angiogenic genes by BMPC, an effect caused by an increasing number of plasma cells might be evenly important.

A Novel Role For Histone Deacetylase 11 (HDAC11) In Plasma Cell Differentation and Survival

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 1907-1907
Author(s):  
Eva Sahakian ◽  
Jason B. Brayer ◽  
John Powers ◽  
Mark Meads ◽  
Allison Distler ◽  
...  
Keyword(s):  
Gene Expression ◽  
Multiple Myeloma ◽  
Bone Marrow ◽  
B Cells ◽  
Plasma Cell ◽  
Research Funding ◽  
Plasma Cells ◽  
Myeloma Cells ◽  
Peripheral Blood Plasma

Abstract The role of HDACs in cellular biology, initially limited to their effects upon histones, is now appreciated to encompass more complex regulatory functions that are dependent on their tissue expression, cellular compartment distribution, and the stage of cellular differentiation. Recently, our group has demonstrated that the newest member of the HDAC family of enzymes, HDAC11, is an important regulator of IL-10 gene expression in myeloid cells (Villagra A Nat Immunol. 2009). The role of this specific HDAC in B-cell development and differentiation is however unknown. To answer this question, we have utilized a HDAC11 promoter-driven eGFP reporter transgenic mice (TgHDAC11-eGFP) which allows the monitoring of the dynamic changes in HDAC11 gene expression/promoter activity in B-cells at different maturation stages (Heinz, N Nat. Rev. Neuroscience 2001). First, common lymphoid progenitors are devoid of HDAC11 transcriptional activation as indicated by eGFP expression. In the bone marrow, expression of eGFP moderately increases in Pro-B-cells and transitions to the Pre- and Immature B-cells respectively. Expression of eGFP doubles in the B-1 stage of differentiation in the periphery. Of note, examination of both the bone marrow and peripheral blood plasma cell compartment demonstrated increased expression of eGFP/HDAC11 mRNA at the steady-state. These results were confirmed in plasma cells isolated from normal human subjects in which HDAC11 mRNA expression was demonstrated. Strikingly, analysis of primary human multiple myeloma cells demonstrated a significantly higher HDAC11 mRNA expression in malignant cells as compared to normal plasma cells. Similar results were observed in 4/5 myeloma cell lines suggesting that perhaps HDAC11 expression might provide survival advantage to malignant plasma cells. Support to this hypothesis was further provided by studies in HDAC11KO mice in which we observed a 50% decrease in plasma cells in both the bone marrow and peripheral blood plasma cell compartments relative to wild-type mice. Taken together, we have unveiled a previously unknown role for HDAC11 in plasma cell differentiation and survival. The additional demonstration that HDAC11 is overexpressed in primary human myeloma cells provide the framework for specifically targeting this HDAC in multiple myeloma. Disclosures: Alsina: Millennium: Membership on an entity’s Board of Directors or advisory committees, Research Funding. Baz:Celgene Corporation: Research Funding; Millenium: Research Funding; Bristol Myers Squibb: Research Funding; Novartis: Research Funding; Karyopharm: Research Funding; Sanofi: Research Funding.

Stroma cells and Monocytes make Multiple Myeloma Cells Active In Bone Marrow Microenviroment

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 5333-5333
Author(s):  
Hiroshi Ikeda ◽  
Tadao Ishida ◽  
Toshiaki Hayashi ◽  
Yuka Aoki ◽  
Yasuhisa Shinomura
Keyword(s):  
Stem Cells ◽  
Multiple Myeloma ◽  
Bone Marrow ◽  
Cell Lines ◽  
Stromal Cells ◽  
Conflicts Of Interest ◽  
Cell Contact ◽  
Drug Induced ◽  
Myeloma Cells

Abstract The Bone marrow (BM) microenvironment plays crucial role in pathogenesis of multiple myeloma　(MM). Paracrine secretion of cytokines in BM stromal cells promotes multiple myeloma cell proliferation and protects against drug-induced cytotoxicity. In current study, monocytes, component of BM cells, can directly promote mesenchymal stem cells osteogenic differentiation through cell contact interactions. Down-regulation of inhibitors such as DKK1 drives the differentiation of mesechymal stem cells into osteoblasts. In this study, we examined the role of monocytes as a potential niche component that supports myeloma cells. We investigated the proliferation of MM cell lines cultured alone or co-cultured with BM stromal cells, monocytes, or a combination of BM stromal cells and monocytes. Consistently, we observed increased proliferation of MM cell lines in the presence of either BM stromal cells or monocytes compared to cell line-only control. Furthermore, the co-culture of BM stromal cells plus monocytes induced the greatest degree of proliferation of myeloma cells. In addition to increased proliferation, BMSCs and monocytes decreased the rate of apoptosis of myeloma cells. Our results therefore suggest that highlights the role of monocyte as an important component of the BM microenvironment. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Bone Marrow Adipocyte Shapes Metabolism and Immunity in Tumor Microenvironment to Promote Multiple Myeloma

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 892-892
Author(s):  
Lingling Shu ◽  
Jinyuan Li ◽  
Shuzhao Chen ◽  
Han-Ying Huang ◽  
Yang Li ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Fatty Acid ◽  
Lipid Metabolism ◽  
Lipid Binding ◽  
Bone Marrow Microenvironment ◽  
Acid Uptake ◽  
Fatty Acid Binding ◽  
Myeloma Cells

Abstract Multiple myeloma (MM) often occurs in middle-aged, elderly and obese patients with ectopic accumulation of fat cells in the bone marrow. Bone marrow adipocytes (BMAs) display unique immunomodulatory properties instead of simply providing energy substrates, which can cause distinct change of bone marrow microenvironment. Although BMA accounts for 70% of the total volume of bone marrow, the mechanism on how BMA affects tumor progression remains elusive. This study aims to explore the pathogenesis of BMA in promoting myeloma and new potential treatment strategies targeting bone marrow microenvironment. Newly diagnosed MM patients in our cancer center and their relative healthy controls are recruited. A significant increase of BMA quantity in multiple myeloma patients was observed. Moreover, analysis of transcriptome sequencing data of BMA derived from MM patients demonstrated a distinctive gene expression profiles (Fig A). It worth to note that, expression of fatty acid-binding protein 4 (FABP4, also known as A-FABP or aP2), a member of the FABP family abundantly expressed in adipocytes, functions as a lipid-binding chaperone that regulates trafficking and cellular signaling of fatty acids, and plays an important role in linking lipid metabolism with immunity and inflammation, was increased significantly in BMA of MM patients (Fig B). To further explore the role of FABP4 in pathogenesis in MM, FABP4 knockout (KO) mice and their wide-type (WT) littermates were adopted, and fed with standard chow (STC) or high-fat diet (HFD, 45 kcal % Fat, D12451). FABP4 deficiency significantly attenuated the tumor burden and MM-related osteolytic lesions in mice fed with HFD (Fig C-D). Moreover, levels of pro-inflammatory cytokines including TNFα, IL-6, RANKL and DPP4 were significantly reduced in FABP4 deficient adipocytes (Fig E). Flow cytometry analysis showed that the infiltration and pro-inflammatory polarization (M1/M2) of macrophages (MΦ) decreased significantly in FABP4 KO bone marrow (Fig F). In addition, FABP4 promoted the infiltration of Th1 and Th17 cells, while impaired the recruitment of Th2 and Treg cells (Fig G). Furthermore, administration of exogenous FABP4 recombinant protein significantly increased the fatty acid uptake and oxygen consumption of myeloma cells (Fig H). In contrast, pharmacological inhibition of FABP4 with BMS309403 alleviated the invasion and metastasis of MM in mice fed with HFD (Fig I-J). In summary, BMA increased in MM patients, reshapes the metabolism and immunity in bone marrow microenvironment through regulating FABP4 functions. FABP4 enhanced the energy and lipid metabolism of myeloma cells, and manipulated the bone marrow microenvironment to pro-tumor environment, therefore promoted the proliferation and migration of myeloma cells. This study will not only clarify the critical role of BMA in MM pathogenesis, but also provide therapeutic potential of FABP4 selective inhibitor BMS309403 for multiple myeloma treatment, especially for obese MM patients. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

scholarly journals Annexin II Interactions with the Annexin II Receptor Enhance Multiple Myeloma Cell Adhesion and Growth in the Bone Marrow Microenvironment,

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 3942-3942
Author(s):  
Sonia D'Souza ◽  
Noriyoshi Kurihara ◽  
Yusuke Shiozawa ◽  
Jeena Joseph ◽  
Russell Taichman ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Multiple Myeloma ◽  
Bone Marrow ◽  
Cell Growth ◽  
Cell Lines ◽  
Stromal Cells ◽  
Critical Role ◽  
Myeloma Cell ◽  
Bone Marrow Microenvironment ◽  
Annexin Ii

Abstract Abstract 3942 Background: Multiple myeloma (MM) is an incurable B-cell malignancy that develops in the bone marrow. The marrow microenvironment plays a critical role in supporting homing, lodging, and growth of MM cells by activating signaling pathways in both MM and bone marrow stromal cells (BMSC). We previously showed that annexin II (AXII) is involved in prostate cancer cell lodgment to the bone marrow via the annexin II receptor (AXIIR) expressed on prostate cancer cells. We hypothesized that MM cells use a similar mechanism to lodge and grow in the bone marrow. In support of this hypothesis, we found that MM cell lines and primary MM cells from 8 MM patients express the AXIIR protein, and that MM cells adhered significantly better to BMSC from AXII+/+ mice than from AXII−/− mice. Further, knockdown of AXIIR by siRNA in MM1.S and ANBL-6 MM cells decreased AXII binding and decreased adherence of MM cells to human stromal cells and BMSC from AXII+/+ mice. Furthermore, addition of an anti-AXII antibody to MM1.S cells, did not effect MM cell growth demonstrating that AXII expressed by MM cells does not support MM cell growth. Importantly, soluble AXII was released by osteoclasts into their conditioned media which stimulated the growth of MM cells via ERK1/2 and AKT phosphorylation. In the further study, we further characterized the role of AXIIR in MM-BMSC interactions. Methods: AXIIR expression in MM cells was determined by RT-PCR, Western blotting, and immunocytochemistry. Adhesion and growth assays were performed between MM cells and BMSC or AXII to determine the contribution of the AXII/AXIIR axis in supporting adhesion and growth of MM cells. In addition, MM cells or CD138+ cells from MM patients were treated with AXII to determine AXII-dependent MM cell growth. Further, adhesion and growth assays were performed on MM cells expressing either siAXIIR or shAXIIR. Phosphorylation assays were performed to determine the pathways stimulated by AXII in MM cells. Since OCL secrete large amount of AXII, MM cell growth assays were performed with OCL-CM from AXII+/+ and AXII−/− mice in the presence of an AXII antibody. Results: We now report that in addition to MM1.S and ANBL-6 cells, other MM cell lines, including U266, H929, and OPM2 also express AXIIR, and that AXII stimulated the growth of RPMI8226, ANBL-6 and U266 in addition to MM1.S cells. Finally, an AXIIR antibody prevented adhesion of MM1.S cells to AXII, and that AXII upregulated the adhesion molecule, RhoA in MM cells. Additionally, AXII did not stimulate the proliferation of MM1.SshAXIIR cells compared to MM1.SshControl or untreated MM cells, demonstrating that AXII specifically acts through its receptor, AXIIR on MM cells to promote proliferation. More importantly, AXII stimulated the growth of CD138+ cells obtained from MM patients. Conclusions: Based on our results, we conclude that the interaction between AXII and AXIIR in the bone marrow microenvironment supports adhesion via RhoA and growth of MM cells by stimulating the Erk1/2 and Akt pathways, AXII produced by MM cells does not act in an autocrine manner on MM cell growth. Thus, AXII and AXIIR are key players in MM and targeting the AXII/AXIIR axis may be a novel therapeutic approach for MM. Disclosures: Roodman: Amgen: Consultancy; Millennium: Consultancy.

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