Stroma-dependent Cell Research Articles

Myeloma Exosomes Prime the Microenvironment to Support Survival and Growth of Myeloma Cells

IntroductionMyeloma bone marrow serum primes healthy donor (HD) bone marrow cells to support the survival and growth of myeloma plasma cells (MMPC) in co-culture. Following interaction with the MMPC, the phenotype of the HD bone marrow stroma changes and the expression of immune regulatory factors is increased while expression of genes associated with osteoblastogenesis and WNT signaling is suppressed. The aim of this study was to determine whether exosomes in the myeloma bone marrow serum have a role in priming the microenvironment.MethodsSerum was separated from clotted bone marrow aspirates from myeloma patients obtained during scheduled clinic visits, and from healthy donors of similar ages.Exosomes were prepared from 1-2 ml of serum using Invitrogen’s Total Exosome Isolation kit according to manufacturer’s instruction. Exosomes were 30-130 nm in diameter as determined by Dynamic Light Scatter on a Brookhaven Instruments Corp. ZetaPlus Particle Sizing Software, and visualized by scanning electron microscopy. Small RNA (≤200 nucleotides) was isolated using Qiagen’s miRNeasy kits, quality and quantity assessed with Qubit 2. 96 microRNAs (miRs) were analyzed by qRT-PCR on Fluidigm’s BioMark platform using 96x96 multiplex chips and normalized to spiked in C. elegance miR mimetic.Primary CD138-expressing cells were isolated from EDTA-anticoagulated bone marrow aspirates. Luciferase-expressing stroma-dependent myeloma cells were described previously (Bam, BMC Cancer 2015:864). Healthy donor mesenchymal stem cells (MSC) were prepared from bone particles obtained during orthopedic surgery, and cultured in a-MEM supplemented with 10% FBS.Primary myeloma cells or luciferase-expressing stroma dependent myeloma cells were added to wells containing monolayers of MSC in α-MEM supplemented with 10% FBS in 96 well culture plates. For each experiment 3 conditions were used: A control group, a group to which 10% myeloma bone marrow serum was added, and a third group to which exosomes isolated from a matching bone marrow serum aliquot were added. The number of primary MMPC dictated that these experiments were carried out in duplicates, while the stroma dependent cells were plated in 5 replicates. Viable primary cells counts or luciferase bioluminescence were evaluated after 4 days of co-culture.ResultsExosomes supported survival and growth of primary MMPC in co-culture with HD MSC, but had no effect on MMPC cultured alone, indicating that the myeloma bone marrow serum exosomes prime the MSC to support the MMPC. Exosomes from 5 of the 7 patients supported growth of stroma-dependent myeloma cells co-cultured with HD MSC. In a representative experiment, the bioluminescence of stroma-dependent myeloma cells was 46% higher in co-cultures supplemented with bone marrow serum (p=7.3E-6) and 23% higher (p=2.0E-6) when exosomes were used. The effect was reproduced when primary MMPC were used: in a representative experiment, the number of primary MPC recovered from the co-cultures supplemented with bone marrow serum was 41% higher, and when supplemented with exosomes 28% higher than in controls. Primary MMPC did not survive in the absence of MSCs and bone marrow serum or exosomes did not enhance their survival.ConclusionsExosome from bone marrow serum of myeloma patients prime the bone marrow microenvironment to support survival and growth of primary MMPC. Bone marrow serum is more effective, indicating that other factors in the serum are also important. The differences in microRNA contents between healthy donor and myeloma exosomes may provide an insight of the regulatory mechanisms molding the myeloma bone marrow microenvironment. DisclosuresMorgan:Univ of AR for Medical Sciences: Employment; Celgene: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria; Bristol Meyers: Consultancy, Honoraria; Janssen: Research Funding.

Role of Bruton's tyrosine kinase in myeloma cell migration and induction of bone disease

Myeloma cells typically grow in bone, recruit osteoclast precursors and induce their differentiation and activity in areas adjacent to tumor foci. Bruton's tyrosine kinase (BTK), of the TEC family, is expressed in hematopoietic cells and is particularly involved in B-lymphocyte function and osteoclastogenesis. We demonstrated BTK expression in clinical myeloma plasma cells, interleukin (IL)-6- or stroma-dependent cell lines and osteoclasts. SDF-1 induced BTK activation in myeloma cells and BTK inhibition by small hairpin RNA or the small molecule inhibitor, LFM-A13, reduced their migration toward stromal cell-derived factor-1 (SDF-1). Pretreatment with LFM-A13 also reduced in vivo homing of myeloma cells to bone using bioluminescence imaging in the SCID-rab model. Enforced expression of BTK in myeloma cell line enhanced cell migration toward SDF-1 but had no effect on short-term growth. BTK expression was correlated with cell-surface CXCR4 expression in myeloma cells (n = 33, r = 0.81, P < 0.0001), and BTK gene and protein expression was more profound in cell-surface CXCR4-expressing myeloma cells. BTK was not upregulated by IL-6 while its inhibition had no effect on IL-6 signaling in myeloma cells. Human osteoclast precursors also expressed BTK and cell-surface CXCR4 and migrated toward SDF-1. LFM-A13 suppressed migration and differentiation of osteoclast precursors as well as bone-resorbing activity of mature osteoclasts. In primary myeloma-bearing SCID-rab mice, LFM-A13 inhibited osteoclast activity, prevented myeloma-induced bone resorption and moderately suppressed myeloma growth. These data demonstrate BTK and cell-surface CXCR4 association in myeloma cells and that BTK plays a role in myeloma cell homing to bone and myeloma-induced bone disease. Am. J. Hematol. 88:463-471, 2013. © 2013 Wiley Periodicals, Inc.

Growth Differentation Factor 15 Is a Survival Factor for multiple myeloma cells and its plasma Concentration In Patients Is Related to Reduced Survival

AbstractAbstract 614We previously reported that bone marrow mesenchymal stem cells (BMMSCs) from newly diagnosed multiple myeloma (MM) patients were abnormal. In particular, we showed that Growth Differentiation 15 (GDF15) expression was higher in MM BMMSCs than in normal BMMSCs. GDF15 is a divergent member of the human TGFβ superfamily. GDF15 overexpression has been described in numerous malignancies and its concentration is increased in the serum of patients with glioma, prostate, colorectal or pancreatic cancers. Contradictory data prevent to understand clearly GDF15 implication in pathophysiology of tumors. Furthermore, GDF15 has never been studied in haematological malignancies. Our first objective was thus to determine the effect of human recombinant GDF15 (rGDF15) on MOLP-6 stroma-dependent cell line and MM1.S stroma-independent cell line under serum free culture conditions. rGDF15 could significantly increase cell survival in MOLP-6 but not in MM1.S. Interestingly, rGDF15 was able to induce Akt phosphorylation on Threonine 308 in MOLP-6 and primary MM cells but not in MM1.S cells. Furthermore, pre-treatment of MOLP-6 with Akt pharmacologic inhibitor abrogated the prosurvival effect of GDF15, suggesting an Akt-dependent mechanism. In the same culture conditions, we observed that rGDF15 could abrogate toxicity of drugs classically used in MM treatment (melphalan, bortezomid and lenalidomide) for both cell lines MOLP-6 and MM1.S, suggesting that this cytoprotective effect may be Akt-independent. Because of the in vitro effects of GDF15, our second objective was to determine whether the plasma concentration of GDF15 (pGDF15) in patients with MM may be indicative of the seriousness of the disease or correlate with the response to the treatment. Thus, we investigated the pGDF15 in 131 patients with newly diagnosed MM and 13 healthy subjects. We first found that it was significantly higher for patients with MM (0.90±1.10 ng/mL) than for healthy subjects (0.25±0.08 ng/mL) (P< .001). In patients with MM, pGDF15 correlated with the main prognostic factor of the disease (i.e. International Staging System, b2 microglobulin level, presence or absence of deletion of chromosome 13, and bone status). For the 81 patients with high pGDF15 level (≥ 0.50 ng/mL), the probabilities of event-free and overall survival 30 months after diagnosis were 50% and 75%. For the 50 patients with low pGDF15 level (< 0.5 ng/mL), the probabilities were 80% and 97% (P< .0045 and P< .013, respectively). However, we did not find a clear relationship between pGDF15 and response to treatment. We analysed the impact of prognostic factors on event-free survival for the 131 patients with MM. On univariate analysis, event-free survival was significantly related to age (P= .003), b2-microglobulin level (P= .02) and pGDF-15 level (P= .003). On multivariate analysis, event-free survival was significantly related to age (P= .001) and pGDF15 level (P= .04). Our study demonstrates that GDF15 is a survival and cytoprotective factor for MM cells and that pGDF15 is related to initial parameters of the disease and survival, which specifically implicates the MM microenvironment in the pathophysiology and the prognosis of the disease. Disclosures:No relevant conflicts of interest to declare.

Characterization of Mesenchymal Stem Cells Abnormalities in Multiple Myeloma.

Introduction: The bone marrow microenvironnement (BMMe) play a significant role in the physiopathology of the multiple myeloma (MM). However, its abnormality still remains controversial. To address this question, we studied bone marrow mesenchymal stem cells (MSCs), the only long-lived cells of the BMMe. We compared, at a genomic and functional level, the MSCs isolated from patients with MM, to MSCs isolated from healthy subjects and those with monoclonal gammopathy of unknown significance (MGUS).Material and methods : Bone marrow samples from 26 MM patients, 7 MGUS patients and 11 healthy individuals were compared. The MSCs were selected by their adherence on plastic and were cultured in alpha-MEM medium + 10% SVF and antibiotics during 2 passages (primo-culture = P0 and first passage = P1). The gene expression profiling was carried out by Affymetrix GeneChip microarrays (U133 plus 2.0). The expression of interesting differentially expressed genes was validated by ELISA or qRT-PCR. The phenotype was studied by flow cytometry (CD45, CD90, CD73, CD13, CD14). The CFU-F frequencies in BM samples and in cell suspensions after P0 and P1 were studied as well as the cell productions after P0 and P1. The osteoblastic differentiation was evaluated both by alkaline phosphatase dosing and matrix mineralization quantification. We also carried out co-cultures of the MSCs with CD34+ cells to quantify their hematopoietic supportive potential. Finally XG1 and Molp-6, respectively stroma independent and stroma dependent cell lines, were co-cultured with MSCs to check the capacity of the MSCs to support malignant plasma cell growth.Results: Gene expression profile independently classified the MSCs in a normal and in a MM group. MGUS MSCs were interspersed between those 2 groups. 145 distinct genes were differentially expressed in MM and normal MSCs. Among them, 46% could be involved in tumor-microenvironment cross-talk. Known soluble factors involved in MM physiopathologic features, such as IL-6, IL-1ß, DKK1 and amphiregulin, were identified and new ones found. In particular growth and differentiation factor-15 (GDF-15), already described as a accurate biomarker of numerous tumours, was significantly overexpressed (p<0.001) in MM MSCs both at mRNA and protein levels (183.5 ± 64.9 vs 749 ± 90.9 for mRNA, 1 10−4 pg/cell ± 1.9 10−5 pg/cell vs 4.3 10−4 pg/cell ± 1.4 10−4 pg/cell for protein respectively for normal and MM MSCs). It was also able to induce dose-dependant growth of Molp-6, in the absence of a supportive stroma. The phenotype and the CFU-F frequencies and the cell productions were similar in the 3 groups of MSCs and their hematopoietic supportive capacity was maintained. The MM MSCs complete differentiation towards the osteoblastic lineage, evaluated quantitatively, was faded. And very importantly, MM MSCs constituted a better supportive feeder layer for the Molp-6 cell line as compared to normal MSCs (cell expansion after 7 days : 2.1 ± 0.3 vs 3.3 ± 0.4, p = 0.04, respectively for normal and MM MSCs). On the other hand, the growth of XG1 was not influence by the subject origin of the MSCs.Conclusion: Our results show that the MSCs, like the malignant plasma cells, are abnormal in MM. This confirms the place of microenvironnement in the physiopathology of the MM and makes it possible to identify new potential therapeutic targets.

Mutual Education Between Hematopoietic Cells and Bone Marrow Stromal Cells Through Direct Cell-to-Cell Contact: Factors That Determine the Growth of Bone Marrow Stroma-Dependent Leukemic (HB-1) Cells

A stroma-dependent cell line (HB-1) was established from myelogenous leukemic cells of CBA/N mouse. Characterization of the cells showed that HB-1 proliferated on hematopoietic supportive stromal cells (MS-10), but did not survive or proliferate on hematopoietic nonsupportive cells (MS-K). Direct contact between HB-1 and MS-10 appears to be necessary for HB-1 to proliferate on MS-10. We found that interleukin-1α (IL-1α) produced by MS-10 plays a major role in the survival and proliferation of HB-1. IL-11 did not support the proliferation of HB-1 cells by itself, but enhanced the proliferation of HB-1 cells in the presence of IL-1α. The expression of IL-1α and IL-11 was induced in MS-10 by the direct contact with HB-1 cells, and the expression of IL-1 receptor type I (IL-1RI) and interleukin-11 receptor (IL-11R) was induced in HB-1 cells by the attachment of the cells to MS-10. These findings show the existence of two-way interactions between HB-1 and MS-10.© 1998 by The American Society of Hematology.

Mutual Education Between Hematopoietic Cells and Bone Marrow Stromal Cells Through Direct Cell-to-Cell Contact: Factors That Determine the Growth of Bone Marrow Stroma-Dependent Leukemic (HB-1) Cells

AbstractA stroma-dependent cell line (HB-1) was established from myelogenous leukemic cells of CBA/N mouse. Characterization of the cells showed that HB-1 proliferated on hematopoietic supportive stromal cells (MS-10), but did not survive or proliferate on hematopoietic nonsupportive cells (MS-K). Direct contact between HB-1 and MS-10 appears to be necessary for HB-1 to proliferate on MS-10. We found that interleukin-1α (IL-1α) produced by MS-10 plays a major role in the survival and proliferation of HB-1. IL-11 did not support the proliferation of HB-1 cells by itself, but enhanced the proliferation of HB-1 cells in the presence of IL-1α. The expression of IL-1α and IL-11 was induced in MS-10 by the direct contact with HB-1 cells, and the expression of IL-1 receptor type I (IL-1RI) and interleukin-11 receptor (IL-11R) was induced in HB-1 cells by the attachment of the cells to MS-10. These findings show the existence of two-way interactions between HB-1 and MS-10.© 1998 by The American Society of Hematology.