Targeting FGFR3 in t(4;14) Mutiple Myeloma: Pre-Clinical Studies of PRO-001, a Novel Anti-FGFR3 Neutralizing Antibody.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2479-2479
Author(s):  
Suzanne Trudel ◽  
Ellen Wei ◽  
Zhi Hua Li ◽  
Eran Rom ◽  
Ira Chumakov ◽  
...  
Keyword(s):  
Growth Factor ◽  
Cell Lines ◽  
Neutralizing Antibody ◽  
Myeloma Cell ◽  
Chromosomal Translocations ◽  
Minimal Growth ◽  
Erk Phosphorylation ◽  
Human Myeloma Cell

Abstract As with other B-cell malignancies, chromosomal translocations to the immunoglobulin heavy-chain (IgH) locus on chromosome 14q32 are believed to be a hallmark of multiple myeloma (MM), occurring in approximately 50% of patients. Identification of these chromosomal translocations has resulted in the discovery of powerful prognostic tools and novel molecular targets that promise to revolutionize the treatment of this malignancy. Five recurrent translocation partners have been defined, resulting in the dysregulation of the genes encoding cyclin D1 and D3, c-maf, mafB and Fibroblast Growth Factor Receptor 3 (FGFR3) together with MMSET. Genetic analysis of 14q32 translocations in MM has identified distinct groups of patients with separate clinical outcomes supporting a biological correlation of these genes in MM. In particular, the t(4;14) translocation portends a particularly bad prognosis. The association of FGFR3 expression with t(4;14) myeloma and the demonstration of the transforming potential of this receptor tyrosine kinase (RTK), make this a particularly attractive target for drug development for this poor prognosis group. We report here the development of a novel and highly specific anti-FGFR3 neutralizing antibody (PRO-001) isolated from a phage display human combinatorial antibody library. PRO-001 binds with high affinity (Kd=1.3 nM) to FGFR3 in in vitro binding assays and blocks ligand-dependent and independent FGFR3 phosphorylation and signal transduction in cell-based assays. Furthermore, PRO-001 potently inhibits FGFR3-dependent solid tumor growth in mouse xenograft models. We found that PRO-001 bound to, and competed with FGF binding to the surface of FGFR3 on human myeloma cell lines. PRO-001 inhibited FGF-induced phosphorylation of wild-type FGFR3 and downstream ERK phosphorylation in stable B9 cell transfectants (B9-WT) and FGFR3 expressing human myeloma cell lines. The antibody inhibited FGF-mediated growth of B9-WT with an IC50 of 3 μg/ml as determined by MTT proliferation assay. Growth of these cells could be rescued by IL-6 demonstrating selectivity of PRO-001 for FGFR3. PRO-001 inhibited the viability of the FGFR3 expressing, human myeloma cell line, UTMC2. Inhibition of viability was still observed when cells were co-cultured with stroma or in the presence of IL-6, a potent growth factor for MM cells. Several myeloma cell lines lacking FGFR3, showed minimal growth inhibition demonstrating selectivity and lack of non-specific toxic at effective dose concentrations. Finally, PRO-001 bound to FGFR3 on the cell surface, inhibited ERK phosphorylation, and induced cytotoxic responses in primary MM samples derived from t(4;14) positive patients. A xenograft mouse model has been established and studies assessing in vivo activity of PRO-001 are planned and will be reported. Taken together, the data demonstrate that PRO-001 is a specific and potent inhibitor of FGFR3 and that it deserves further study for targeted therapy in MM.

Cytotoxic effect in vivo and in vitro of CHS 828 on human myeloma cell lines

2004 ◽  
Vol 15 (1) ◽  
pp. 63-70 ◽  
Author(s):  
Peter Hovstadius ◽  
Elin Lindhagen ◽  
Sadia Hassan ◽  
Kenneth Nilsson ◽  
Helena Jernberg-Wiklund ◽  
...  
Keyword(s):  
Cell Lines ◽  
Cytotoxic Effect ◽  
Myeloma Cell ◽  
Chs 828 ◽  
Human Myeloma Cell

scholarly journals Targeting the insulin-like growth factor-1 receptor to overcome bortezomib resistance in preclinical models of multiple myeloma

Blood ◽  
2012 ◽  
Vol 120 (16) ◽  
pp. 3260-3270 ◽  
Author(s):  
Deborah J. Kuhn ◽  
Zuzana Berkova ◽  
Richard J. Jones ◽  
Richard Woessner ◽  
Chad C. Bjorklund ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Growth Factor ◽  
Cell Lines ◽  
Proteasome Inhibition ◽  
Myeloma Cell ◽  
Resistant Cell ◽  
In Vivo Model ◽  
Insulin Like Growth Factor

Abstract Proteasome inhibition with bortezomib is a validated approach to the treatment of multiple myeloma, but drug resistance often emerges and limits its utility in the retreatment setting. To begin to identify some of the mechanisms involved, we developed bortezomib-resistant myeloma cell lines that, unlike previously reported models, showed no β5 subunit mutations. Instead, up-regulation of the insulin-like growth factor (IGF)–1 axis was identified, with increased autocrine and paracrine secretion of IGF-1, leading to increased activation of the IGF-1 receptor (IGF-1R). Exogenous IGF-1 reduced cellular sensitivity to bortezomib, whereas pharmacologic or small hairpin RNA–mediated IGF-1R suppression enhanced bortezomib sensitivity in cell lines and patient samples. In vitro studies with OSI-906, a clinically relevant dual IGF-1R and insulin receptor inhibitor, showed it acted synergistically with bortezomib, and potently resensitized bortezomib-resistant cell lines and patient samples to bor-tezomib. Importantly, OSI-906 in combination with bortezomib also overcame bor-tezomib resistance in an in vivo model of myeloma. Taken together, these data support the hypothesis that signaling through the IGF-1/IGF-1R axis contributes to acquired bortezomib resistance, and provide a rationale for combining bortezomib with IGF-1R inhibitors like OSI-906 to overcome or possibly prevent the emergence of bortezomib-refractory disease in the clinic.

scholarly journals Exosomal lncRNA PVT1/VEGFA Axis Promotes Colon Cancer Metastasis and Stemness by Downregulation of Tumor Suppressor miR-152-3p

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Shiue-Wei Lai ◽  
Ming-Yao Chen ◽  
Oluwaseun Adebayo Bamodu ◽  
Ming-Shou Hsieh ◽  
Ting-Yi Huang ◽  
...  
Keyword(s):  
Colon Cancer ◽  
Growth Factor ◽  
Cell Lines ◽  
Distant Metastasis ◽  
Cancer Metastasis ◽  
Lovo Cell ◽  
Promoting Effect ◽  
Colon Cancer Metastasis

Background. Treating advanced colon cancer remains challenging in clinical settings because of the development of drug resistance and distant metastasis. Mechanisms underlying the metastasis of colon cancer are complex and unclear. Methods. Computational analysis was performed to determine genes associated with the exosomal long noncoding (lncRNA) plasmacytoma variant translocation 1 (PVT1)/vascular endothelial growth factor A (VEGFA) axis in patients with colon cancer. The biological importance of the exosomal lncRNA PVT1/VEGFA axis was examined in vitro by using HCT116 and LoVo cell lines and in vivo by using a patient-derived xenograft (PDX) mouse model through knockdown (by silencing of PVT1) and overexpression (by adding serum exosomes isolated from patients with distant metastasis (M-exo)). Results. The in silico analysis demonstrated that PVT1 overexpression was associated with poor prognosis and increased expression of metastatic markers such as VEGFA and epidermal growth factor receptor (EGFR). This finding was further validated in a small cohort of patients with colon cancer in whom increased PVT1 expression was correlated with colon cancer incidence, disease recurrence, and distant metastasis. M-exo were enriched with PVT1 and VEGFA, and both migratory and invasive abilities of colon cancer cell lines increased when they were cocultured with M-exo. The metastasis-promoting effect was accompanied by increased expression of Twist1, vimentin, and MMP2. M-exo promoted metastasis in PDX mice. In vitro silencing of PVT1 reduced colon tumorigenic properties including migratory, invasive, colony forming, and tumorsphere generation abilities. Further analysis revealed that PVT1, VEGFA, and EGFR interact with and are regulated by miR-152-3p. Increased miR-152-3p expression reduced tumorigenesis, where increased tumorigenesis was observed when miR-152-3p expression was downregulated. Conclusion. Exosomal PVT1 promotes colon cancer metastasis through its association with EGFR and VEGFA expression. miR-152-3p targets both PVT1 and VEGFA, and this regulatory pathway can be explored for drug development and as a prognostic biomarker.

scholarly journals Paracrine rather than autocrine regulation of myeloma-cell growth and differentiation by interleukin-6

Blood ◽  
1989 ◽  
Vol 73 (2) ◽  
pp. 517-526 ◽  
Author(s):  
B Klein ◽  
XG Zhang ◽  
M Jourdan ◽  
J Content ◽  
F Houssiau ◽  
...  
Keyword(s):  
Growth Factor ◽  
Cell Lines ◽  
Interleukin 6 ◽  
Neutralizing Antibodies ◽  
Myeloma Cell ◽  
B Cell Differentiation ◽  
Myeloma Cells ◽  
Autocrine Regulation ◽  
Spontaneous Proliferation ◽  
Human Myeloma Cell

Abstract To explore the mechanisms involved in the pathogenesis of human multiple myeloma (MM), we investigated the potential role of interleukin-6 (IL-6), a B-cell differentiation factor in humans, and a growth factor for rat/mouse heterohybridomas and murine plasmacytomas. Using a heterohybridoma assay, we found that two well-documented human myeloma cell lines, RPMI 8226 and U266, did not secrete IL-6 and did not express RNA messengers for IL-6. Neutralizing antibodies to IL-6 did not inhibit their proliferation, and recombinant IL-6 did not stimulate it. Taken together, these data show that IL-6 is not the autocrine growth factor of these human myeloma cell lines. A high production of IL-6 was found in the bone marrows of patients with fulminating MM, compared with patients with inactive or slightly active MM, or to healthy donors. This IL-6 production was assigned to adherent cells of the bone-marrow environment but not to myeloma cells. A spontaneous proliferation of myeloma cells freshly isolated from patients was observed in short-term cultures. Recombinant IL-6 was able to amplify it two- to threefold. The spontaneous proliferation of the myeloma cells was inhibited by anti-IL-6 antibodies and reinduced by recombinant IL-6. After 2 to 3 weeks of culture, the myeloma-cell proliferation progressively declined and no IL-6-dependent myeloma cell lines could be obtained despite repeated additions of fresh IL-6 and costimulation with other cytokines such as tumor necrosis factor (TNF)beta, or IL-1 beta. These data demonstrated a paracrine but not autocrine regulation of the growth and differentiation of myeloma cells by IL-6.

scholarly journals Interleukin-6 is a potent myeloma-cell growth factor in patients with aggressive multiple myeloma

Blood ◽  
1989 ◽  
Vol 74 (1) ◽  
pp. 11-13 ◽  
Author(s):  
XG Zhang ◽  
B Klein ◽  
R Bataille
Keyword(s):  
Multiple Myeloma ◽  
Growth Factor ◽  
Cell Growth ◽  
Interleukin 6 ◽  
Myeloma Cell ◽  
S Phase ◽  
Myeloma Cells ◽  
Severity Of The Disease

Abstract It has recently been demonstrated that interleukin-6 (IL-6) is a potent myeloma-cell growth factor in the majority of patients with multiple myeloma (MM). Using an anti-bromodeoxyuridine monoclonal antibody (MoAb) to specifically count myeloma cells in the S-phase (ie, labeling index, LI), we demonstrate that the IL-6 responsiveness of myeloma cells in vitro is directly correlated with their LI in vivo. Myeloma cells from all 13 patients with high LIs in vivo (greater than or equal to 1%) responded in vitro to IL-6, the strongest response occurring in cells from five patients with plasma-cell leukemia. In contrast, the cells of only two of eight patients with low myeloma-cell LIs in vivo (less than 1%) responded to IL-6 in vitro. After seven days of culturing with 1,000 U/mL recombinant IL-6 (rIL-6), the median LI value in the first group of patients (in vivo LI greater than or equal to 1%) was 11%, ie 11 times higher (P less than .01) than the median LI value (1%) in the second group of patients (in vivo LI less than 1%). Thus, the in vitro IL-6 responsiveness of myeloma cells is directly related to their in vivo proliferative status, and hence to the severity of the disease.

Constitutive and Immunoproteasome Inhibitors Increase IκB and Decrease NF-κB Expression In Dendritic Cell

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3493-3493
Author(s):  
Ahmad-Samer Samer Al-Homsi ◽  
Zhongbin Lai ◽  
Tara Sabrina Roy ◽  
Niholas Kouttab
Keyword(s):  
Multiple Myeloma ◽  
T Cell ◽  
Cell Lines ◽  
Mechanism Of Action ◽  
Peripheral Blood ◽  
Research Funding ◽  
Myeloma Cell ◽  
Multiple Myeloma Cell

Abstract Introduction Constitutive and immunoproteasome inhibitors (C&IPI) were thought to suppress nuclear factor-κB (NF-κB) pathway by preventing IκB degradation, which prevents NF-κB translocation into the nucleus. This mechanism of action has since been questioned by a number of studies. First, bortezomib promoted constitutive NF-κB activity in endothelial cell carcinoma. Second, NF-κB constitutive activity was resistant to bortezomib in multiple myeloma cell lines. Third, bortezomib increased IκB mRNA but post-transcriptionally downregulated IκB in normal cells and in multiple myeloma cell lines resulting in induced canonical NF-κB activation. Lastly, bortezomib increased nuclear levels of IκB as opposed to lowering cytoplasmic levels in cutaneous T cell lymphoma cell line suggesting that nuclear translocation of IκB was possibly responsible for NF-κB inhibition. The inhibitory activity of C&IPI on dendritic cells (DC) is of interest in the prevention of graft versus host disease (GvHD). It has been shown that different C&IPI impede DC maturation and T cell priming both in vitro and in vivo. Herein we sought to understand the mechanism of action of proteasome and immunoproteasome inhibitors on DC and to test their effect on IκB and NF-IκB expression. Materials and Methods We first performed RT PCR on lysates of DC obtained from the peripheral blood of 7 patients who received post-transplant cyclophosphamide and bortezomib as prevention of GvHD on a phase I clinical trial. Patients received allogeneic transplantation from matched-related or unrelated donors. Patients received no other immunosuppressive therapy except for rabbit anti-thymocyte globulin for those receiving graft from unrelated donor. Steroids were not allowed on the study. Samples were obtained on days +1, +4, and +7. The results were analyzed in comparison to samples obtained on day 0 before stem cell infusion. We then performed the same experiment on lysates of DC obtained from the peripheral blood of healthy volunteer donors. DC were untreated or incubated with bortezomib (10 nM for 4 h), carfilzomib (30 nM for 1 h), oprozomib (100 nM and 300 nM for 4 h), ONX 0914 (200 nM for 1 h), PR-825 (125 nM for 1 h), or PR-924 (1000 nM for 1 h). The drug concentration and duration of exposure were chosen based on the IC50 on proteasome activity and to reproduce in vivo conditions. We also performed IκB western blot on DC isolated from peripheral blood of healthy volunteers, untreated or incubated with bortezomib (10 nM for 4 h) or oprozomib (300 nM for 4 h). Each experiment was performed at least in triplicate. Results We found that the combination of cyclophosphamide and bortezomib significantly and progressively increased IκB mRNA while decreasing NF-κB mRNA in DC studied ex vivo. We also found that all studied C&IPI increased IκB mRNA to a variable degree while only oprozomib (300 nM) decreased NF-κB mRNA in DC in vitro. Finally, both bortezomib and oprozomib increased IκB protein level in DC in vitro (figure). Conclusion Our data suggest that C&IPI increase IκB expression in DC. As opposed to the previously reported data in other cell types, the effect is not associated with post-transcriptional downregulation. Cyclophosphamide and bortezomib also decrease NF-κB expression in DC in vivo while only oprozomib had the same effect in vitro. The effect of C&IPI on IκB and NF-κB expression may represent a new mechanism of action and suggests their effect may be cell-type dependent. Disclosures: Al-Homsi: Millennium Pharmaceuticals: Research Funding. Off Label Use: The use of cyclophosphamide and bortezomib for GvHD prevention. Lai:Millennium Pharmaceuticals: Research Funding.

siRNA for the Ig Light Chain Constant Region Reduces Light Chain Production and Secretion By Human Plasma Cells and in a Murine Xenograft Model

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 5722-5722
Author(s):  
Xun Ma ◽  
Ping Zhou ◽  
Monika Pilichowska ◽  
Chakra P Chaulagain ◽  
Sandy Wong ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Human Plasma ◽  
Cell Lines ◽  
Light Chain ◽  
Plasma Cells ◽  
Xenograft Model ◽  
Myeloma Cell ◽  
Constant Region

Abstract Background Ig light chain (LC) diseases such as AL amyloidosis and monoclonal light-chain deposition disease are caused by pathologic free LC. Treatment is aimed at eliminating LC production but success is limited. RNA interference (RNAi) can stop LC production but the diversity of LC variable region sequences poses a challenge that targeting consensus sequences in the constant region (CR) of LC mRNA may overcome (Blood 2014;123:3440). We have developed siRNA pools designed to target the κ or λ LC CR mRNA in human plasma cells and impair LC production and secretion, and have shown that the pool targeting the λ LC CR can do so, and can also trigger a terminal unfolded protein response in clones producing intact Ig due to intracellular accumulation of unpaired heavy chains (ibid). Here we report the results of continued in vitro and in vivo testing of these pools in patient specimens and in a murine xenograft model. Methods Pools of siRNA for the κ or λ LC CR (si[IGLCκCR], si[IGLCλCR]) were custom produced with a non-target control (si[-]). They were introduced in vitro into human plasma cells by an optimized streptolysin O-based method (SLO) and in a NOD.SCID xenograft flank plasmacytoma model by in vivo electroporation as per Gene Therapy 2011;18:1150. In vitro we evaluated LC gene expression, production and secretion at 24 hours in human myeloma cell lines and CD138-selected specimens from patients with plasma cell neoplasms, using real-time PCR (qPCR) for LC mRNA, flow cytometry for intracellular LC mean fluorescence intensity (MFI) and ELISA (Bethyl Laboratories) for LC secretion in 24-hour suspension cultures (106 cells/ml). In vivo we inoculated each of the flanks of NOD.SCID mice with 107 human myeloma cells (ALMC-1 or ALMC-2). When plasmacytomas were 0.5cm3 we injected si[IGLCλCR] or si[-] one time to each flank plasmacytoma respectively, allowing each mouse to serve as its own control. Two days later, the mice were sacrificed and the plasmacytomas excised for qPCR for λ LC mRNA and serum was obtained to measure human λ LC levels by ELISA. Results We have previously described results with siRNA targeting the λ LC CR in human cell lines that make λ LC (ALMC-1, ALMC-2, EJM, OPM2, MM.1S, and MM.1R) and in 16 AL λ patient specimens. We demonstrated significant decreases in LC mRNA, intracellular LC MFI, and λ LC secretion by cell lines (Blood 2014;123:3220); moreover, transcriptional profiling indicated minimal off-target effects (ibid; Supplement). We now report that in vitro secretion of λ LC by CD138-selected plasma cells from AL patients (n=3, newly diagnosed λ) treated with si[IGLCλCR] was reduced by 65% from a mean of 3.1 to 1.0µg/ml and that the residual λ LC mRNA was 49% of control. Similarly we treated κ LC secreting human myeloma cell lines with si[IGLCκCR] and si[-] (IM9, H929, JJN-3, and ARH77). By qPCR the residual κ LC mRNA was 13%, by flow cytometry the MFI was reduced by a median of 67.3% (22.5-90.8), and by ELISA mean κ LC secretion was reduced from 3.7 to 0.8µg/ml (P = 0.055, paired t test). We treated CD138-selected κ patient samples (AL 3, LCDD 1, MM 6) in the same way. By qPCR the residual κ LC mRNA was 57% control, by flow cytometry the MFI was reduced by a median of 37.5% (14-69.8), and by ELISA secretion was reduced from 9.4 to 6.5µg/ml (P = 0.02, paired t test). In the murine dual-flank xenograft model employing λ secreting cells, by qPCR there was a reduction in λ LC mRNA with si[IGLCλCR] treatment in 13 of 16 mice (ALMC-1 11/114, ALMC-2 2/2). In these 14, the median λ LC expression was 66% of control (range, 17-97). In 6/13 the average reduction in λ LC expression was 59%. Of note, measurable levels of human λ LC were found in the blood of all mice at sacrifice. Conclusion With one pool of siRNA targeting the constant region of the κ or λ LC we can significantly reduce production and secretion of LC by clonal human plasma cells, including patient cells, and also reduce the expression of LC in xenograft plasmacytomas in vivo. Two methods of siRNA delivery have been employed in this work thus far, SLO and in vivo electroporation, neither of which require endosomal escape. The specificity of the siRNA pools for plasma cell LC genes and the possible receptivity of plasma cells to RNAi are important positive aspects of this work. Further pre-clinical development of Ig LC CR RNAi employing lipid-based nanoparticle platforms is warranted in order to optimize cell-specific delivery, delivery efficiency and siRNA targeting. Disclosures No relevant conflicts of interest to declare.

Effect of the green tea polyphenol epigallocatechin gallate (EGCG) on growth and IL-6 signalling pathways in malignant plasma cells

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 8114-8114
Author(s):  
R. Burger ◽  
H. Czekalla ◽  
K. Richter ◽  
T. Ahrens ◽  
A. Guenther ◽  
...  
Keyword(s):  
Cell Lines ◽  
Green Tea ◽  
Epigallocatechin Gallate ◽  
Myeloma Cell ◽  
Signalling Pathways ◽  
Dependent Manner ◽  
Green Tea Polyphenol ◽  
Dose Dependent ◽  
Human Myeloma Cell

8114 Background: Epigallocatechin gallate (EGCG) is the predominant polyphenolic constituent of green tea leaves that possesses antitumor, antiinflammatory, and antioxidant activity. EGCG exerts its effects through potentially multiple mechanisms including inhibition of growth factor receptor signalling. The compound is currently under investigation in a phase I/II clinical trial for treatment of patients with early stage chronic lymphocytic leukemia at Mayo Clinic. The goal of our study was to examine the in vitro effects of EGCG in multiple myeloma (MM). Methods: A panel of human myeloma cell lines (n=6) including the IL-6 dependent INA-6 cell line was used to evaluate the sensitivity to EGCG. Cells were cultured for three days in the absence or presence of EGCG at concentrations between 6.25 μM and 100 μM. Cell viability was determined in a colorimetric tetrazolium (MTS) based assay and by trypanblue exclusion. For signalling experiments, INA-6 cells were IL-6 and serum starved and then treated with EGCG for two hours before IL-6 was added. Whole cell lysates were prepared and subjected to SDS-PAGE and Western blot analysis. Results: EGCG inhibited the in vitro growth of human myeloma cell lines by inducing cell death in a time and dose-dependent manner. IC50 concentrations were between 12,5 μM and 50 μM. IL-6 mediated growth of INA-6 cells was inhibited at similar doses. The addition of excess amounts of IL-6 could not protect from EGCG induced cytotoxicity. Pretreatment of INA-6 cells with EGCG resulted in a dose-dependent inhibition of IL-6 induced STAT3 tyrosine phosphorylation. In these cells, stimulation with IL-6 leads to upregulation of Mcl-1 expression. In contrast, phosphorylation of p44/p42 MAPK, which is constitutively activated in INA-6 cells, was not affected. Conclusion: EGCG has growth inhibitory activity on myeloma cells. Specific inhibition of signalling pathways that regulate expression of anti-apoptotic proteins could be one mechanism how EGCG exerts its activity. Our work provides the rationale for further studies to evaluate the effect of EGCG not only in B-CLL, but also in plasma cell tumors. No significant financial relationships to disclose.

Effect of a novel agent, SL-401, targeting interleukin-3 (IL-3)-receptor on plasmacytoid dendritic cell (pDC)-induced myeloma cell growth and drug resistance.

2013 ◽  
Vol 31 (15_suppl) ◽  
pp. 8582-8582
Author(s):  
Dharminder Chauhan ◽  
Arghya Ray ◽  
Christopher Brooks ◽  
Eric K. Rowinsky ◽  
Kenneth Carl Anderson
Keyword(s):  
Drug Resistance ◽  
Cell Growth ◽  
Cell Lines ◽  
Plasmacytoid Dendritic Cell ◽  
Myeloma Cell ◽  
Healthy Donors ◽  
Signaling Axis ◽  
Novel Therapeutic Strategies

8582 Background: Multiple myeloma (MM) remains incurable despite novel therapies, highlighting the need for further identification of factors mediating disease progression and drug resistance. The bone marrow (BM) microenvironment confers growth, survival, and drug resistance in MM cells. Our recent study utilized in vitro and in vivo MM xenograft models to show that plasmacytoid dendritic cells (pDCs) were significantly increased in MM BM and promote MM growth (Chauhan et al., Cancer Cell 2009, 16:309). Importantly, we found increased IL-3 levels upon pDC-MM interaction, which in turn, trigger MM cell growth and pDCs survival. IL-3R is highly expressed on pDCs. We utilized SL-401, a novel biologic conjugate that targets IL-3R, to examine whether abrogation of IL-3–IL-3R signaling axis affects pDC-MM interaction and its tumor promoting sequelae. Methods: MM cell lines, patient MM cells, and pDCs from healthy donors or MM patients were utilized to study the anti-MM activity of SL-401. MM cells and pDCs were cultured alone or together in the presence or absence of SL-401, followed by analysis of cell growth or viability. Results: SL-401 significantly decreased the viability of pDCs at low concentrations (IC50: 0.83 ng/ml; P < 0.005, n = 3). SL-401 also decreased the viability of MM cells at clinically achievable doses. Co-culture of pDCs with MM cells induced growth of MM cell lines; and importantly, low doses (0.8 ng/ml) of SL-401 blocked MM cell growth-promoting activity of pDCs. MM patient-derived pDCs induced growth of MM cell lines and primary MM cells as well; conversely, SL-401 inhibited pDC-triggered MM cell growth (P < 0.005, n= 5). Tumor cells from 3 of the 5 patients were from patients whose disease was progressing while on bortezomib, dexamethasone, and lenalidomide therapies. In agreement with these results, SL-401 blocked pDC-induced growth of dexamethasone-resistant MM cell lines. Conclusions: Our study therefore provides the basis for directly targeting pDCs or blocking the pDC-MM interaction, as well as targeting MM, in novel therapeutic strategies with SL-401 to enhance MM cytotoxicity, overcome drug-resistance, and improve patient outcome.

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