scholarly journals Ectopic expression of BIRC5-targeting miR-101-3p overcomes bone marrow stroma-mediated drug resistance in multiple myeloma cells

BMC Cancer ◽  
2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Jahangir Abdi ◽  
Nasrin Rastgoo ◽  
Yan Chen ◽  
Guo An Chen ◽  
Hong Chang
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Drug Resistance ◽  
Ectopic Expression ◽  
Luciferase Assay ◽  
Bone Marrow Stroma ◽  
Plate Reader ◽  
Marrow Stroma ◽  
Direct Target ◽  
Fluorescence Plate Reader

Abstract Background Multiple myeloma (MM) cells gain protection against drugs through interaction with bone marrow stromal cells (BMSCs). This form of resistance largely accounts for resistance to therapy in MM patients which warrants further exploration to identify more potential therapeutic targets. Methods We performed miRNA/mRNA qPCR arrays and western blotting to analyze transcriptional and translational changes in MM cells co-cultured with BMSCs. Drug cytotoxicity and apoptosis in MMGFP-BMSC co-cultures were measured using fluorescence plate reader and flowcytometry, respectively. miRNA was overexpressed in MM cell lines using Lentiviral transduction, miRNA-3’UTR binding was examined using luciferase assay. Results We found that BMSCs downregulated miR-101-3p and upregulated survivin (BIRC5) in MM cells. Survivin was downregulated by miR-101-3p overexpression and found to be a direct target of miR-101-3p using 3’UTR luciferase assay. Overexpression of survivin increased viability of MM cells in the presence of anti-myeloma drugs, and miR-101-3p inhibition by anti-miR against miR-101-3p upregulated survivin. Furthermore, overexpression of miR-101-3p or silencing of survivin triggered apoptosis in MM cells and sensitized them to anti-myeloma drugs in the presence of BMSCs overcoming the stroma-induced drug resistance. Conclusions Our study demonstrates that BMSC-induced resistance to drugs is associated with survivin upregulation which is a direct target of miR-101-3p. This study also identifies miR-101-3p-survivin interaction as a druggable target involved in stroma-mediated drug resistance in MM and suggests it for developing more efficient therapeutic strategies.

scholarly journals Repression of Mcl-1 expression by the CDC7/CDK9 inhibitor PHA-767491 overcomes bone marrow stroma-mediated drug resistance in AML

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Eimear O’ Reilly ◽  
Sukhraj Pal S. Dhami ◽  
Denis V. Baev ◽  
Csaba Ortutay ◽  
Anna Halpin-McCormick ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Drug Resistance ◽  
Bone Marrow Stroma ◽  
Marrow Stroma ◽  
Cdk9 Inhibitor

Discovery and Characterization of Macrocyclic Thiopeptide Proteasome Inhibitors for Hematologic Malignancies

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3669-3669
Author(s):  
Sridevi Ponduru ◽  
Raymond Moellering ◽  
Edward Greenberg ◽  
John Paul Ying-Ching Shen ◽  
Benjamin Z Stanton ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Protein Degradation ◽  
High Throughput ◽  
Active Sites ◽  
Proteasome Inhibitors ◽  
Hematologic Malignancies ◽  
Bone Marrow Stroma ◽  
Shh Signaling ◽  
Marrow Stroma

Abstract The ubiquitin proteasome pathway comprises a coordinated, dynamic cellular system critical to cellular metabolism, signaling and proliferation. The expanding clinical utility of the peptide boronate, bortezomib, in the treatment of patients with multiple myeloma and other hematologic malignancies has established the human 26S proteasome as a validated target in cancer. Still, only one FDA-approved proteasome inhibitor presently exists. Restricted activity against one enzymatic function of the proteasome and dose-limiting toxicities associated with bortezomib warrant further discovery efforts aimed at the identification of structurally and functionally distinct protein degradation inhibitors (PDIs). Here, we report a novel family of natural product proteasome inhibitors discovered by high-throughput, high-content screening at the National Cancer Institute Initiative for Chemical Genetics. A primary screen of 14,000 small molecules was performed in 384-well plate format using a cell line stably transfected with a destabilized fluorescent protein chimera. Assay positives were retested in the primary screen in dose-response format. Thiostrepton was selected for further characterization due to its unique macrocyclic chemical structure, the recent publication of its total synthesis, reports of anticancer properties and the lack of prior annotation as a PDI. First, thiostrepton was linked to previously characterized molecules acting on the protein degradation pathways by transcriptional small molecule connectivity mapping (CMAP). Subsequent cell-state analyses confirmed strong induction of functional and annotated gene sets associated with misfolded protein stress and proteasome inhibition. Mechanism of action was confirmed by biochemical profiling of human 20S proteasome active site inhibition and specificity using homogeneous assays and selective substrates for each of three catalytic active sites. Importantly, inhibitory activity of thiostrepton differs from bortezomib by blocking both the chymotryptic-like and PGPH active sites with sub-micromolar potencies. Dose-dependent inhibition of multiple myeloma cell growth was observed, with a concomitant increase in polyubiquitinated protein stress and induction of apoptosis. Inhibition of conferred proliferation by bone marrow stroma was confirmed using a novel miniaturized high-content assay modeling the bone marrow stroma-multiple myeloma microenvironment. Structurally related compounds to thiostrepton, nosiheptide and siomycin, were confirmed also as proteasome inhibitors as above. Our discovery of this class of natural products as proteasome inhibitors and a recent report of siomycin inhibition of Sonic Hedgehog (Shh) signaling begged the question whether established proteasome inhibitors would inhibit Shh signaling in human cancer. This hypothesis was confirmed in a set of reporter-gene assays. In sum, these studies identify thiopeptide macrocycles as a class of naturally-occurring proteasome inhibitors poised for clinical development in hematologic malignancies, establish novel high-throughput assays for modeling MM-stroma microenvironment interactions and pave the way for the development of proteasome inhibitors in disease states where Shh signaling is central to pathogenesis.

Aberrant Expression Of miRNA and mRNA Of Cell Cycle and Adhesion-Related Genes In Bone Marrow Stroma Cells Derived From Patients With Multiple Myeloma

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3149-3149 ◽  
Author(s):  
Rimma Berenstein ◽  
Blau Igor Wolfgang ◽  
Axel Nogai ◽  
Marlies Wächter ◽  
Antonio Pezzutto ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Multiple Myeloma ◽  
Bone Marrow ◽  
Genetic Alterations ◽  
Bone Marrow Stroma ◽  
Aberrant Expression ◽  
Healthy Donors ◽  
Marrow Stroma ◽  
Bone Marrow Stroma Cells

Abstract Multiple myeloma (MM) is a B-cell malignancy characterized by accumulation of malignant plasma cells (PC) within the bone marrow. The bone marrow microenvironment such as bone marrow stroma cells (BMSC) supports MM disease progression, resistance to chemotherapy, protects the tumor cells against apoptosis and causes osteolytic bone disease and angiogenesis. The aim of this study was to identify constitutive genetic alterations in BMSC derived from patients with MM (MM-BMSC) in comparison to BMSC from healthy donors. For BMSC selection, mononuclear cells were isolated from fresh bone marrow aspirates and were further expanded in cell culture. We studied 25 MM patients and 5 healthy donors. Senescence status was determined in passage 1 of cell cultures. MM-BSMC displayed a considerably higher percentage of senescence cells (p<0,05). We investigated the expression of cell cycle and adhesion-associated genes (CCNE1, CCND1, CDKN1B, VCAM, ICAM, IKK-alpha) in BMSC (passage 4) using SYBR-Green Real-Time PCR and relative quantification by linear regression. A downregulation of CCNE1 (p=0,05), CDKN1B (p=0,29), and an upregulation of CCND1 (p=0,05), VCAM-1 (p=0,33), ICAM-1 (p=0,33), and IKK-alpha (p=0,05) was demonstrated. Furthermore, the expression profile of miRNAs, targeting the analyzed mRNA genes or correlating with senescence, was studied (miR-16, miR-221, miR-126, miR-223, miR-485-5p and miR-519d). For miRNA detection treatment with Poly(A)-Polymerase and cDNA-Synthesis with a Poly(T)VN-Adaptor primer were carried out following an amplification with an universal reverse primer corresponding to the adaptor sequence and a miRNA-specific primer. miR-16, miR-223, miR-485-5p and miR-519d were significantly upregulated, (p=0,02; p=0,004; p=0,02; and p=0,002, respectively), whereas miR-221 and miR-126 showed no considerable differences to BMSC obtained from healthy donors. Next we investigated incubation of immunmodulatory drug Lenalidomid in BMSC cultures. Cells were treated with 10 µM Lenalidomid over 72 hours and expression was normalized to a 0,01 % DMSO control. Significant difference in gene expression were visible for ICAM-1 (p=0,01). For CDKN1B (p=0,16) and VCAM-1 (p=0,12) we demonstrated changes in gene expression. Our results indicate aberrant expression of cell cycle and adhesion-related genes, such as CCNE1, CCND1 and CDKN1B VCAM-1, ICAM-1 and IKK-alpha in MM-BMSC as compared with healthy donors. Furthermore, we found significant upregulation of miR-16, miR-223, miR-485-5p and miR-519d. Further investigation are needed to determine molecular mechanisms in MM-BMSC and PC interaction that lead to constitutive changes in BMSC characteristics and gene expression patterns. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Overexpression of c-maf is a frequent oncogenic event in multiple myeloma that promotes proliferation and pathological interactions with bone marrow stroma

Cancer Cell ◽  
2004 ◽  
Vol 5 (2) ◽  
pp. 191-199 ◽  
Author(s):  
Elaine M Hurt ◽  
Adrian Wiestner ◽  
Andreas Rosenwald ◽  
A.L Shaffer ◽  
Elias Campo ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Bone Marrow Stroma ◽  
Marrow Stroma

scholarly journals The sumoylation pathway is dysregulated in multiple myeloma and is associated with adverse patient outcome

Blood ◽  
2010 ◽  
Vol 115 (14) ◽  
pp. 2827-2834 ◽  
Author(s):  
James J. Driscoll ◽  
Dheeraj Pelluru ◽  
Konstantinos Lefkimmiatis ◽  
Mariateresa Fulciniti ◽  
Rao H. Prabhala ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Mammalian Cells ◽  
Treatment Strategies ◽  
Dominant Negative ◽  
Bone Marrow Stroma ◽  
Stroma Cell ◽  
Bone Marrow Stroma Cell ◽  
Marrow Stroma ◽  
Conjugating Enzyme

Abstract Multiple myeloma (MM) is a plasma cell neoplasm that proceeds through a premalignant state of monoclonal gammopathy of unknown significance; however, the molecular events responsible for myelomagenesis remain uncharacterized. To identify cellular pathways deregulated in MM, we addressed that sumoylation is homologous to ubiquitination and results in the attachment of the ubiquitin-like protein Sumo onto target proteins. Sumoylation was markedly enhanced in MM patient lysates compared with normal plasma cells and expression profiling indicated a relative induction of sumoylation pathway genes. The Sumo-conjugating enzyme Ube2I, the Sumo-ligase PIAS1, and the Sumo-inducer ARF were elevated in MM patient samples and cell lines. Survival correlated with expression because 80% of patients with low UBE2I and PIAS1 were living 6 years after transplantation, whereas only 45% of patients with high expression survived 6 years. UBE2I encodes the sole Sumo-conjugating enzyme in mammalian cells and cells transfected with a dominant-negative sumoylation-deficient UBE2I mutant exhibited decreased survival after radiation exposure, impaired adhesion to bone marrow stroma cell and decreased bone marrow stroma cell–induced proliferation. UBE2I confers cells with multiple advantages to promote tumorigenesis and predicts decreased survival when combined with PIAS1. The sumoylation pathway is a novel therapeutic target with implications for existing proteasomal-based treatment strategies.

scholarly journals The Influence of the Bone Marrow Niche on Drug Response Phenotypes of Blood Cancers

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 262-262
Author(s):  
Sophie Rabe ◽  
Eva Schitter ◽  
Tobias Roider ◽  
Peter-Martin Bruch ◽  
Carolin Kolb ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Drug Resistance ◽  
Tumor Cells ◽  
Ex Vivo ◽  
Culture Conditions ◽  
Bone Marrow Stroma ◽  
Spontaneous Apoptosis ◽  
Stroma Cell ◽  
Trisomy 12 ◽  
Marrow Stroma

Abstract Background: Signals provided by the microenvironment can modify and circumvent pathway activities that are therapeutically targeted by drugs. However, a systems-level understanding of how the microenvironment and the genetic and molecular alterations of the tumor interact with each other and contribute to drug resistance is lacking. Methods: To address this unmet need, we established an automated microscopy-based phenotyping platform that uses co-culture conditions mimicking the bone marrow environment. We cultured primary tumor cells from more than 100 leukemia patients (CLL, AML, MCL, T-PLL, HCL) with and without bone marrow stroma cell support in DMEM and 10% human serum and treated each condition with 57 drugs in 3 concentrations. After 72h of incubation, 22 000 images per patient were acquired and processed by our custom made image analysis pipeline. Our set-up allows us to increase sensitivity far beyond simple viability testing, as it reads out additional cell type specific features such as cell morphology, autophagy and cell-cell interactions. Results: Quality assessment revealed that in contrast to mono-culture conditions, assay plate edge effects can be avoided under stable stroma cell co-culture conditions. Correlation of replicated patient samples were comparable between mono- and co-cultures (R2>0.75). In the absence of their native microenvironment, primary leukemia cells undergo spontaneous apoptosis ex-vivo. Viability at culture start was always >90% and dropped to a median of 51% (viability range: 17%-90%) after 72h in mono-cultures. Among CLL samples spontaneous apoptosis was not dependent on either IGHV mutation status or any major cytogenetic risk group. Bone marrow stroma cell co-culture conditions protected tumor cells from spontaneous apoptosis (p=8.2e-6, paired t-test). Patient samples with a high degree of spontaneous apoptosis benefited most from co-culture conditions (p=7.2e-10, Pearson correlation). To model interactions of stroma cell conditions and drug-induced apoptosis we established the following linear model: Viability ~ drug-effect + culture-model + drug-effect:culture-model. While activity of some drugs was significantly altered under co-culture conditions, we could also identify drugs with similar activity in mono- and co-cultures. For instance, the activity of common chemotherapeutics (fludarabine: p=0.002 at 0.6µM, cytarabine: p=0.001 at 1.5µM, ANOVA) or bromodomain inhibitors (I-BET-762: p=5.9e-5 at 4.5µM, JQ1: p=1.5e-8 at 1.5µM, ANOVA) was significantly reduced under co-culture conditions. In contrast, PI3K inhibitors idelalisib and duvelisib had a similar activity in mono-culture and stroma co-culture conditions and might represent a starting point to overcome stroma cell mediated drug resistance. In CLL, we identified IGHV mutation status and trisomy 12 as important determinants of response to kinase inhibitors. We confirmed these findings in stroma cell co-cultures, e.g. a better activity of B-cell receptor inhibitors in trisomy 12 and IGHV unmutated CLL. A systematic comparison of ex-vivo drug response pattern in mono- and co-cultures across 171 drug conditions will be presented. Conclusion: Our results suggest that high throughput co-culture drug testing can be robustly performed and provide an unprecedented understanding of how the stroma cell microenvironment and the genetic make-up of tumor cells contribute to drug resistance and sensitivity. Figure: Over 2 million microscopy images were acquired and analysed to assess drug resistance and sensitivity in a co-culture model of primary leukemia and bone marrow stroma cells. blue= Hoechst33342, green=Calcein AM, red=lysosomal dye NIR Figure 1. Figure 1. Disclosures No relevant conflicts of interest to declare.

CD28 and CD86 Regulate Integrin Surface Expression In Multiple Myeloma

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4450-4450
Author(s):  
Catherine M Gavile ◽  
David Egas ◽  
Gregory H Doho ◽  
Sagar Lonial ◽  
Kelvin P Lee ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Drug Resistance ◽  
Cell Surface ◽  
Plasma Cells ◽  
Myeloma Cell ◽  
Bone Marrow Stroma ◽  
Rna Seq ◽  
Myeloma Cells ◽  
Surface Molecules ◽  
Marrow Stroma

Multiple myeloma is a malignancy of long lived plasma cells. Like normal plasma cells, myeloma cells are dependent on the bone marrow microenvironment for survival. While the specific interactions and downstream signals mediated by the bone marrow stroma have yet to be fully characterized, drug resistance is linked to these pathways, and further understanding will uncover new therapeutic avenues for myeloma. CD28 and CD86 are best known for their role in T-cell activation; however they have recently been shown to play important roles in the generation and survival of normal long lived plasma cells. CD28 is the canonical costimulatory receptor known to activate the PI3K-Akt pathway in T-cells upon binding to CD80 or CD86 from an antigen-presenting cell. CD28 and CD86 are also expressed by normal plasma and myeloma cells, and we have previously shown that both CD28 and CD86 are necessary for myeloma cell survival. Silencing of either CD28 or CD86 results in cell death in 3 human myeloma cell lines (RPMI8226, MM.1s, and KMS18). Interestingly, in 2 cell lines, knockdown of CD86 results in higher levels of cell death than CD28. In these lines, silencing CD28 or addition of a soluble inhibitor CTLA4-Ig (Abatacept), results in an increase in CD86 expression. Taken together, these data suggest that CD28 and CD86 regulate the survival of myeloma cells through either cis or trans signals, and feedback signals from CD28 control CD86 expression. The data also suggest that signaling events result from ligation of either CD28 or CD86. To better define the nature of the survival signals emanating from CD28 and CD86, we performed RNA-Seq on myeloma cells where CD28 or CD86 expression had been silenced. For silencing of CD28 we found 1292, 1195, and 1697 transcripts that were significantly changed compared to vector control in KMS18, MM.1s and RPMI8226, and silencing CD86 results in a similar number of changes (1405, 1200 and 1866 transcripts respectively). Since CD28 and CD86 form a receptor-ligand pair, we focused on genes that were common to silencing of both. Of genes that had significant expression changes compared to vector control, we found 229, 221 and 399 transcripts that were commonly regulated by CD28 and CD86 in KMS18, MM.1s and RPMI8226 respectively. Most transcripts were either upregulated (45.4 to 57.5%) or downregulated (28.8 to 41.5%) by silencing of either CD28 or CD86. A subset of transcripts (13.1 to 14%) showed a pattern of expression similar to CD86 - silencing of CD28 and CD86 had opposite effects on expression. This subset of transcripts may represent genes that are regulated by CD86 signaling, and may explain the difference in sensitivity to CD28 vs. CD86 silencing. Curiously, in KMS18 where this difference was not observed, RNA-Seq indicates that these cells are homozygous for a CD86 SNP that is associated with increased cancer susceptibility and lower transplant rejection, and may represent a hypomorphic allele. Surprisingly, we did not observe any significant changes in either pro- or anti-apoptotic Bcl-2 genes in any cell line except for upregulation in minor transcripts of Bcl2L11 (Bim) in KMS18 cells. This change did not affect overall expression as confirmed by qRT-PCR. However, expression of several cell surface proteins associated with myeloma cell survival did change. Integrin-ß1 (ITGB1) and -ß7 (ITGB7) are surface molecules that facilitate both cell-matrix and cell-cell interactions, and have been implicated in myeloma growth, survival, and drug-resistance. Knockdown of CD28 or CD86 resulted in downregulation of ITGB7 that was confirmed by qRT-PCR. We also saw a reduction of ITGB7 at the cell surface with CD86 knockdown, but not with CD28. ITGB1 expression was reduced at the mRNA and cell surface levels with knockdown of CD86, but was induced with CD28 knockdown. Based on their patterns of expression, ITGB7 may be regulated by CD28 signaling, while ITGB1 may be downstream of CD86 signaling. These data indicate that CD28-86 signaling regulates the expression of integrins on the surface of myeloma cells. Because drug resistance has been linked to the myeloma cells’ interaction with the bone marrow stroma and its resident cells (CAM-DR), these surface molecules could be important mediators of CD28 and CD86 survival signaling. Taken together, our data indicate that targeting CD28-86 signaling is a promising therapeutic approach to CAM-DR, and may be a useful addition to current regimens against myeloma. Disclosures: Lonial: Onyx: Consultancy; Celgene: Consultancy; Millennium: Consultancy; Novartis: Consultancy; BMS: Consultancy; Sanofi: Consultancy; Onyx: Consultancy. Boise:Onyx Pharmaceuticals: Consultancy.

Bone Marrow Stroma (BMS) Prevents Apoptosis of Lymphoma Cells by Upregulation of BMS-Derived B-Cell Activating Factor (BAFF) and Activation of NF-kB.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2378-2378
Author(s):  
Tint Lwin ◽  
Lori A. Hazlehurst ◽  
Lynn C. Moscinski ◽  
William S. Dalton ◽  
Jianguo Tao
Keyword(s):  
Bone Marrow ◽  
Drug Resistance ◽  
Cell Adhesion ◽  
B Cell ◽  
Stromal Cells ◽  
Lymphoma Cell ◽  
Bone Marrow Stroma ◽  
Lymphoma Cells ◽  
Marrow Stroma ◽  
Induced Apoptosis

Abstract Stromal cells are an essential component of the bone marrow microenvironment that regulate or supports tumor survival. The bone marrow stroma has long been recognized as a "sanctuary site" for lymphoma cells during traditional chemotherapy. In this study, we demonstrated that adhesion of the B-cell lymphoma cell lines SUDH-4 and 10 to bone marrow stroma inhibited mitoxantrone-induced apoptosis. This adhesion-dependent inhibition of mitoxantrone-induced apoptosis correlated with decreased activation of caspases- 8 and 9, and cleavage of caspase 3 and PARP. EMSA analysis demonstrated significantly increased NF-kB binding activity in cells adhered to stroma cells compared to lymphoma cells in suspension. This DNA binding activity could be attributed to cell adhesion-mediated proteolysis of p100 NF-kappaB2 resulted in generation of active p52, which translocates to the nucleus in complex with p65 and RelB. Furthermore, co-culture with stromal cells also induced expression of the NF-kB-regulated anti-apoptotic molecules, XIAP, cIAP1 and cIAP2. In addition, because of the knowledge that BAFF shown to be critical for maintenance of normal B cell homeostasis as well as the survival of malignant B cells, we characterized the functional significance of BAFF in BMS-mediated drug resistance and survival. BAFF was detected on BMS cell line HS-5 and BMS cells derived from lymphoma patients by flow cytometry. Concentrations of BAFF were 3- to 25-fold higher in bone marrow aspirate than in peripheral blood. Lymphoma cell adhesion to HS-5 cells significantly increased BAFF secretion evidenced by both ELISA and immunoblotting. Addition of BAFF counteracted mitoxantrone-induced apoptosis, and elicited a reduction in spontaneous apoptosis in primary lymphomas via activation of NF-kB activation. Finally neutralization of BAFF by TACI enhanced lymphoma cell response to chemotherapy and overcame cell-adhesion mediated drug resistance, suggesting that lymphoma cells utilize BAFF as survival factor. These data indicate that stromal cells prevent apoptosis of lymphoma cells by upregulation of BAFF and induction of NF-kB-regulated anti-apoptotic proteins. Bone marrow-derived BAFF plays a key role in lymphoma cell survival and drug resistance in bone marrow microenvironment.

Bortezomib Reverts Stroma-Mediated Resistant to APO2L/TRAIL in Multiple Myeloma.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2806-2806
Author(s):  
Nancy Parquet ◽  
Mark Mead ◽  
Claudio Anasetti ◽  
William S. Dalton ◽  
Lia Perez
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Cancer Cells ◽  
Induced Resistance ◽  
Soluble Factor ◽  
Bone Marrow Stroma ◽  
Myeloma Cells ◽  
Bortezomib Treatment ◽  
Trail Receptors ◽  
Marrow Stroma

Abstract Abstract 2806 Poster Board II-782 Hematopoietic stroma provides a sanctuary for multiple myeloma (MM) cells and promotes resistance to immune control mediated by APO2L/TRAIL in part by increasing synthesis of the anti-apoptotic protein c-FLIP (J Immunol, 180: 3; 2008). Bortezomib, a reversible 26S proteosome inhibitor, sensitizes cancer cells to APO2L/TRAIL induced apoptosis in a variety of malignancies including MM. In addition, it has been well established that bortezomib interferes with the protective interaction between cancer cells and the bone marrow stroma. In this study we tested whether bortezomib can reverse the APO2L/TRAIL environmental mediated-immune resistant (EM-IR). Using MM cell lines (RPMI 8226 and U266) or CD138+ positive selected cells from MM patient's bone marrow, we found that exposure to HS5 stroma cells by direct adhesion or in a transwell system induced resistance to bortezomib (10nM for 24 hours) and that pretreatment with bortezomib (10nM for 20 hours) effectively overcomes APO2L/TRAIL resistance (10ng/mL for 4 additional hours). Conditioned medium made from a 14-day culture of MM patient's bone marrow stroma induced resistance to bortezomib and pretreatment with bortezomib sensitized cells to APO2L/TRAIL induced cell death as shown with HS5 cells. Bortezomib showed not to be cytotoxic to HS5 stroma cells and only MCP-2-3 and IL-10 levels were altered in the stroma-MM milieu within cytokines measured by ELISA array. IL-6, a cytokine shown to induce APO2L/TRAIL mediated resistance, remained unchanged with bortezomib treatment. We found that bortezomib increased expression of TRAIL receptors (DR5, DCR1 and DCR2), but such expression did not predict for sensitivity to apoptosis as DR4 demonstrated to be the receptor responsible for activation of APO2L/TRAIL. Soluble factor(s) released by HS5 stroma increased expression of c-FLIP and induced STAT-3 and ERK phosphorylation in myeloma cells. However, only c-FLIP protein expression was effectively reduced by bortezomib. c-FLIP quantitative-PCR found that HS5 increased transcription only after 20 hours bortezomib treatment and significantly reduces soluble factor(s) induced c-FLIP transcription. In a transwell assay, HS5 stroma cells induced NF-κB activation and the addition of bortezomib diminished its activation at 20 hours. These findings provide the rationale to combine bortezomib and APO2L/TRAIL to disrupt the influence of the stroma microenvironment on myeloma cells. Disclosures: Off Label Use: sirolimus for graft-versus-host disease.

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