Secreted Frizzled-Related Protein-3 (sFRP3) Is Produced by Myeloma Cells and Augments Wnt3a-Induced Differentiation of Mesenchymal Stem Cells and OPG Production in Osteoblasts

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 808-808 ◽  
Author(s):  
Ya-Wei Qiang ◽  
Yu Chen ◽  
Bo Hu ◽  
Wei Qiang ◽  
Christoph Heuck ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Cell Lines ◽  
Bone Disease ◽  
Plasma Cells ◽  
Bone Lesions ◽  
Beta Catenin ◽  
Canonical Wnt Signaling ◽  
Myeloma Cells ◽  
Canonical Wnt ◽  
Msc Differentiation

Abstract Abstract 808 Background: Bone disease is one of the most debilitating complications in patients with multiple myeloma (MM). The molecular mechanisms by which MM triggers bone disease are not fully understood. We have previously demonstrated that Dkk1 is highly expressed in primary MM plasma cells, and associated with bone disease in MM patients by inhibiting Wnt signaling-promoted mesenchymal stem cell differentiation and osteoprotegerin production in osteoblast cells. We have also reported that increase in Wnt signaling in the bone marrow microenvironment by overexpression of Wnt3a in myeloma cells or administration of rWnt3a, or indirectly increasing Wnt signaling by administration of anti-Dkk1 neutralizing antibody also decreased in osteoclast numbers. However, Dkk1 is less frequently expressed in MM cell lines that are derived mostly from late stage of MM; and injection of these MM cell lines into human fetal bone also is able to induce bone lesion in MM animal model. These results indicate that additional factors may be involved in induction of the bone disease at the stage of the disease. The members of the sFRPs family of secreted proteins (including sFRP-1, -2, -3 and -4) directly bind to Wnts, thereby preventing Wnts from binding to the cellular Wnt receptor complex. It has also been reported that sFRP-1 and -2 augment canonical Wnt3a activated signaling in fibroblast. MM cells from pateints with advanced bone lesions express sFRP2 mRNA. Like sFRP2, sFRP3 mRNA is highly expressed in MM plasma cells, but it's function in MM bone disease remains unknown. We sought to investigate the role of sFRP3 in MM-triggered bone lesions using the osteoblast (OB) cell lines CH3T1/2 and C2C12, and serum from MM pateints those MM cells expressed high level of sFRP3. Methods/Results: RT-PCR analysis showed that sFRP3 is expressed in primary MM plasma cells and certain MM cell lines. Recombinant sFRP3 protein did not inhibit, but synergized with Wnt3a to increase beta-catenin protein, while Dkk1 significantly inhibited this process. Similarly, sFRP3 treatment of OB cells increase Wnt-3a-induced TCF transcript activity in OB cells transfected with TOPflash luciferase report constructs. sFRP3 also increased MSC differentiation, as evidenced by increase in alkaline phosphatase activity (ALP) and increased in mineralization by Alizarin red staining. sFRP3 treatment also increases OPG mRNA and protein production in these cells. Similar to sFRP3, sFRP1 and sFRP2 synergistically acted with Wnt3a to induce MSC differentiation and OPG expression in osteoblasts, while Dkk1 significantly inhibited these processes. To confirm the synergistic effects of sFRPs with canonical Wnt signaling on MSC differentiation, we employed R-podin1, a well-known agonist of canonical Wnt signaling. Treatments of MSC cells with R-podin1 led to increase in beta-catenin protein and TCF transcriptional activity and in ALP activity, and increase in OPG mRNA and protein. Pretreatment of the cells with sFRP2 and sFPP3 proteins further enhanced the function of R-podin1. In contrast, Dkk1 protein showed negative effect on R-Spodin1 functions, indicating that sFRP2 and sFRP3 synergized with R-Spodin1 to induce activation of canonical Wnt signaling and subsequent MSC differentiation and OPG production. Conclusion: Taken together, these data suggest that sFRP2 and sFRP3 augment canonical Wnt signaling to induce MSC differentiation and indirectly inhibit osteoclastogenesis by regulating OPG in MSC cells. These results also indicate that Dkk1 may be most important in MM-induced bone disease. Disclosures: Barlogie: Celgene, Genzyme, Novartis, Millennium: Consultancy, Honoraria, Patents & Royalties. Shaughnessy:Myeloma Health, Celgene, Genzyme, Novartis: Consultancy, Employment, Equity Ownership, Honoraria, Patents & Royalties.

Beta-Catenin and N-Cadherin in Myeloma: Implications for Adhesion and Migration.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 2497-2497
Author(s):  
Fenghuang Zhan ◽  
Simona Colla ◽  
Ya-Wei Qiang ◽  
Owen Stephens ◽  
Yongsheng Huang ◽  
...  
Keyword(s):  
Stem Cells ◽  
Wnt Signaling ◽  
Cell Lines ◽  
Plasma Cells ◽  
Myeloma Cell ◽  
Beta Catenin ◽  
Myeloma Cells ◽  
And Migration ◽  
Canonical Wnt

Abstract Increasing evidence suggests that altered Wnt signaling plays an important role in myelomagenesis. We recently discovered that myeloma plasma cells secrete soluble inhibitors of Wnt signaling and these prevent osteoblast differentiation and contribute to development of osteolytic lesions. We have also shown that myeloma plasma cells are capable of activating both canonical and non-canonical Wnt signaling pathways and that this primarily induces morphological changes, invasion and migration through non-canonical signaling. As beta-catenin is the primary effector of canonical Wnt signaling, we investigated the potential role of beta-catenin in primary myeloma. Although beta-catenin can be stabilized upon Wnt-3A treatment of both primary myeloma cells and myeloma cells lines, we were unable to note any effects on proliferation or activation of beta-catenin-TCF targets genes. Western blotting of protein extracts from plasma cells from 69 newly diagnosed cases showed highly variable levels of stable beta-catenin. Using SAM analysis with a 1% false discovery rate we correlated beta-catenin levels with global gene expression levels in these 69 samples and found that high beta-catenin levels were strongly correlated with expression of only a single gene, the neural adhesion molecule N-cadherin (CDH2). Microarray analysis on a large panel of normal and malignant B-cells showed that CDH2 expression was unique to myeloma plasma cells and that CDH2 was expressed highest in hyperdiploid and FGFR3/MMSET-positive cases. As expected CDH2 expression was high in in-vitro-expanded mesenchymal stem cells, osteoblasts and CD34-selected stem cells. In-vitro derived osteoclasts from myeloma patients and normal donors did not express CDH2. N-cadherin was immunoprecipitated from 8 primary myeloma cells and 6 myeloma cell lines and resolved by SDS-PAGE and N-cadherin and beta-catenin were detected in immunoprecipitation complexes following immunoblotting. Moreover, beta-catenin and N-cadherin protein levels showed a high degree of correlation on western blots. Flow cytometery of N-cadherin expression on primary samples showed heterogeneous expression with as little as 15% and as much as 77% of CD38+/CD45− plasma cells expressing the protein. OPM2, JJN3, and ARP1 myeloma cell lines, which express different levels of N-cadherin, were treated with the N-cadherin neutralizing antibody GC-4 and the cells subjected to the transendothelial migration assay. Maximum inhibition was observed for JJN3 cells, with 60% inhibition at 24 hrs, while OPM2 had an intermediate level of inhibition (40%) and ARP1, the only N-cadherin negative line, underwent transendothelial migration as efficiently as control cells. These data suggests that functional adherns junctions of beta-catenin and N-cadherin likely exist on myeloma plasma cells and these junctions may play a role in myeloma biology that centers on cell adhesion and migration and possibly cell-cell communication.

Beta-Catenin Depended and Independent Effects Induced by Myeloma Cells in Human and Murine Osteoblasts and Osteoblast Progenitors.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3433-3433
Author(s):  
Francesca Morandi ◽  
Sara Tagliaferri ◽  
Sabrina Bonomini ◽  
Mirca Lazzaretti ◽  
Luca Ferrari ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Cell Lines ◽  
Osteoblastic Cells ◽  
Beta Catenin ◽  
Canonical Wnt Signaling ◽  
Osteoprogenitor Cell ◽  
Significant Difference ◽  
Bone Biopsies ◽  
Canonical Wnt ◽  
Osteoblast Progenitors

Abstract Osteoblast impairment occurs within myeloma (MM) cell infiltration into the bone marrow (BM). Wnt signaling is involved in the regulation of osteoblast formation. Canonical Wnt signaling pathway is activated by Wnt 1/3a that induce the activation of GSK3/Axin complex leading to the stabilization and nuclear translocation of beta-catenin that in turn activates the transcription system Lef1/TCF. Recently it has been reported that MM cells produce the Wnt inhibitors DKK-1 demonstrating a correlation between its expression and the presence of bone lesions in MM patients. However the effect of MM cells on Wnt signaling cascade in osteoblasts and osteoblast progenitors has not been investigated. To clarify this issue, first we checked DKK-1 production by human myeloma cell lines (HMCLs), purified CD138+ MM cells and BM plasma of MM patients by PCR and ELISA. Following we performed a co-culture system with HMCLs or CD138+ MM cells and either human osteoblast line (HOBIT) and with BM osteoprogenitor cells (PreOB) obtained after differentiation from mesenchymal cells or murine osteoprogenitor cell lines C2C12 and MC3T3. Both DKK-1 positive HMCLs (XG-1 and JJN3) and negative ones (RPMI-8226, OPM-2) have been used in co-culture as well as DKK-1 positive and negative purified CD138+ MM cells. Similarly we tested the effect of BM plasma of MM patients positive and negative for DKK-1 production on both human and murine cells. Wnt signaling in osteoblasts and osteoblast progenitors was evaluated either at mRNA level by specific human and murine Wnt Array kits and by quantitative PCR or at protein one by Western blot analysis for GSK3b/Axin and LEF-1/TCF expression. We evaluated active de-phosphorylated beta-catenin and inactive phosphorilated one by westernblot and by ELISA in cytosolic and nuclear extracts. DKK-1 median levels detected in the conditioned media of XG-1 and JJN3, MM cells and in BM plasma of DKK-1 positve MM patients were 0.60 ng/mL and 0.38 and 8.84 (range: 1.55–91) ng/mL respectively. Any significant inhibitory effect on WNT signaling and active beta-catenin expression and levels was not observed in HOBIT and human PreOB after co-culture with both HMCLs and MM cells or BM plasma independently to DKK-1 expression. On the contrary DKK-1 positive MM cells or BM plasma suppressed active beta-catenin expression in murine osteoprogenitor cell lines in presence of BMP-2. Consistently Wnt3a stimulation as well as anti-DKK-1 abs. did not restore the inhibitory effects on osteoblast formation and differentiation induced by MM cells in human PreOB. Consistently any significant difference was not detected on beta-catenin expression by stromal/osteoblastic cells on bone biopsies by immunohistochemistry between osteolytic (n°=10) and non-osteolytic (N°=10) MM patients. The different behavior between human and murine osteoblastic cells was further investigated. We found that both cells expressed significant levels of active beta-catenin however DKK-1 suppressed active nuclear and cytosol beta-catenin at concentration of 20–30 ng/mL in C2C12 and MC3T3 whereas only DKK-1 concentrations higher to 500 ng/mL are able to inhibited beta-catenin in HOBIT and human PreOB as well as osteoblast formation and differentiation in human BM cultures. In conclusion our data indicate that MM cells block canonical Wnt signaling in murine osteoblastic cells but not in human osteoblasts and osteoblast progenitors. Beta-catenin independent mechanisms could be involved in DKK-1 mediated bone destruction in MM patients.

Expression of Wnt-3a in Myeloma Cells Inhibits the Osteolytic Phenotype In-Vivo.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3420-3420
Author(s):  
Ya-Wei Qiang ◽  
Shmuel Yaccoby ◽  
John D. Shaughnessy
Keyword(s):  
Bone Resorption ◽  
Wnt Signaling ◽  
Myeloma Cell ◽  
Beta Catenin ◽  
Canonical Wnt Signaling ◽  
Myeloma Cell Line ◽  
Myeloma Cells ◽  
Canonical Wnt

Wnt signaling is a highly conserved signal transduction pathway involved in embryonic development. Inappropriate canonical Wnt signaling resulting in beta-catenin stabilization, is associated with several types of human cancers. Multiple myeloma plasma cells express Wnt receptors, Wnt ligands and soluble Wnt inhibitors. Wnt signaling is central to osteoblast and osteoclasts development and secretion of Wnt signaling inhibitors by myeloma cells is thought to contribute to the osteolytic phenotype seen in this disease and prostate cancer. While it is now clear that MM cells can signal through both canonical and non-canonical mechanisms, there are conflicting data as to the direct role of Wnt signaling in myeloma cell biology. Others have shown that Wnts cause proliferation of myeloma cells; while we have shown that canonical Wnts cause morphological changes and migration, but not cell proliferation. To further elucidate the role of canonical Wnt signaling in myeloma and myeloma bone disease we used limiting dilutions in the presence of G418 to create two independent stable clones of the myeloma cell line NCI-H929 expressing Wnt-3A (H929/W3A), which is not expressed in myeloma, and an empty vector (H929/EV). Because Wnt antibodies are not available we cloned Wnt-3A as a fusion protein with hemagglutinin (HA). Western blots against HA revealed a positive band of the expected size only in the H929/W3A clones. GST-E-cadherin binding assay and Western blot analysis revealed elevated levels of total and free beta-catenin in H929/W3A relative to H929/EV, however, there this was not associated with increased growth or proliferation by MTT assay. To determine the in-vivo growth characteristics and effects on bone resorption of Wnt-3A producing cells, we transplanted the lines into a human bone implanted the flank of SCID mice. Tumor growth rate as determined by increased production of human immunoglobulin in mice serum was significantly slower in the Wnt-3A transfected cells relative to controls (P < .05). Loss of bone mineral density (BMD) of the implanted bones engrafted with H929/W3A cells was lower than in bones engrafted with H929/EV cells (P < .05). Reduced tumor burden and BMD loss was also visualized on x-ray radiographs. Taken together these data indicate that all factors promoting bone resorption produced by or elicited by the myeloma cell line H929 are subordinate to canonical Wnt signaling and that prevention of bone destruction may help control myeloma progression.

SFRP4-Mediated Inhibition of Canonical Wnt-Signaling in DLBCL

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 3999-3999
Author(s):  
Raphael Koch ◽  
Bjoern Chapuy
Keyword(s):  
Wnt Signaling ◽  
B Cell ◽  
Cell Lines ◽  
Conflicts Of Interest ◽  
B Cell Lymphoma ◽  
Beta Catenin ◽  
Canonical Wnt Signaling ◽  
Pharmacological Inhibition ◽  
Canonical Wnt ◽  
Large B Cell

Abstract Introduction: Wnt-signaling enhances proliferation in a variety of malignancies including diffuse large B-cell lymphoma (DLBCL) and exosomes, small secreted microvesicles, are known to carry active wnt-molecules to mediate wnt-signaling. We found consistent suppression of SFRP4, an inhibitor of canonical wnt-signaling in DLBCL, elucidated it's mechanism of action and addressed it´s impact on regulating proliferation of diffuse large B-cell lymphomas. We conducted a screen of chemical wnt-inhibitors and assessed wnt-addiction in DLBCL cell lines. Material & Methods: The Cancer Cell Line Encyclopedia (CCLE) was used to assess the transcript abundace of SFRP4 in 18 DLBCL cell lines. SFRP4-expression was confirmed using western blot and immunofluorescence in representative DLBCL cell lines. Purified exosomes of DLBCL cell lines, recombinant human SFRP4 and SFRP4-shRNA were used to address the biological mechanism of SFRP4 action. 5-Azacytidine was used to restore SFRP4-expression. Furthermore shRNA mediated knockdown of beta-catenin and pharmacological inhibition of canonical wnt-signaling using XAV-939, IWP-2, C59 and UM206 were used to address wnt-addiction in DLBCL cell lines. Results: We found SFRP4 to be significantly suppressed in a variety of malignancies, including DLBCL, with promotor methylation as a known mechanism of suppression. SFRP4 was able to suppress exosomal mediated canonical wnt-signaling. SFRP4 inhibited proliferation in DLBCL cell lines and enhanced cytotoxicity of doxorubicin. Treatment with 5-Azacytidine restored expression of SFRP4, induced decline of beta-catenin and suppressed cell proliferation. Knock down of beta-catenin and pharmacological perturbation of canonical wnt-signaling identified wnt-addiction in beta-catenin expressing cell lines in the absence of a MYC translocation or amplification. Conclusions: SFRP4 suppresses proliferation of DLBCL cell lines by antagonizing exosomal mediated canonical wnt-signaling. Pharmacological inhibition of canonical wnt-signaling significantly decreased proliferation of DLBCL cell lines in the absence of genomic alterations involving MYC. Disclosures No relevant conflicts of interest to declare.

Abstract 293: Tcf7l2 Expression And Isoform Switching In Mouse Hearts

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
LU XIAO ◽  
Haiqing Bai ◽  
James Boyer ◽  
Bo Ye ◽  
Ning Hou ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Wnt Signaling ◽  
Stop Codon ◽  
Medical Center ◽  
Premature Stop Codon ◽  
Beta Catenin ◽  
Canonical Wnt Signaling ◽  
Cardiovascular Research ◽  
Reading Frame ◽  
Canonical Wnt

Lu Xiao, Haiqing Bai, James Boyer, Bo Ye, Ning Hou, Haodong Xu, and Faqian Li Department of Pathology and Laboratory Medicine and Cardiovascular Research Institute, University of Rochester Medical Center, Rochester, NY, USA Backgrounds: Canonical Wnt signaling appears to have multiphasic and often antagonistic roles in cardiac development. The molecular mechanism for these opposing actions is not clear. We hypothesized that alternative splicing of TCF7L2, a nuclear interaction partner of beta-catenin is involved in the specificity of canonical Wnt signaling. Methods: RT-PCR were performed on embryonic (E16.5) and neonatal (day 8) hearts with primers spanning the end of first exon and the beginning of last exon and the products were cloned and sequenced. Result: There are totally 18 exons identified so far in TCF7L2. We sequenced 56 clones and 53 clones (29 from day 8) and (24 from E16.5) contained TCF7L2 sequences. No exon 6 or exon 17 was found in TCF7L2 transcripts of mouse hearts. Most clones (more than 80%) from E16.5 and day 8 hearts excluded exon 4. Both E16.5 and day 8 hearts had one clone with exon 9 deletion which does not change reading frame and another with alterations in exon 3 that lead to reading frame shift and premature stop codon. As reported in other organs, there were extensive alternative splicing in the C-terminal exons 14, 15 and 16. The inclusion of exon 14 was more frequently in day 8 (18 of 29, 62%) than in E16.5 (8 of 24, 33%) hearts. The peptide encoded by exon 14 has conserved functional motif. Additionally, this alternative exon usage can change the C-terminus of TCF7L2 to include or exclude the so-called E tail with two binding motifs for C-terminal binding protein. Conclusion: The isoform switch of TCF7L2 occurs in neonatal mouse hearts and may have a role in the terminal differentiation of cardiac myocytes during this period.

Nuclear β-catenin localization is not sufficient for canonical Wnt signaling activation in human melanoma cell lines

2011 ◽  
Vol 45 (5) ◽  
pp. 816-822 ◽  
Author(s):  
K. V. Kulikova ◽  
A. V. Posvyatenko ◽  
N. V. Gnuchev ◽  
G. P. Georgiev ◽  
A. V. Kibardin ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Cell Lines ◽  
Melanoma Cell ◽  
Human Melanoma ◽  
Human Melanoma Cell ◽  
Canonical Wnt Signaling ◽  
Signaling Activation ◽  
Canonical Wnt ◽  
Melanoma Cell Lines

scholarly journals Abi1 loss drives prostate tumorigenesis through activation of EMT and non-canonical WNT signaling

2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Disharee Nath ◽  
Xiang Li ◽  
Claudia Mondragon ◽  
Dawn Post ◽  
Ming Chen ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Wnt Signaling ◽  
Tumor Progression ◽  
Cell Line ◽  
Rna Sequencing ◽  
Cell Lines ◽  
Adaptor Protein ◽  
Prostate Tumor ◽  
Canonical Wnt Signaling ◽  
Canonical Wnt

Abstract Background Prostate cancer development involves various mechanisms, which are poorly understood but pointing to epithelial mesenchymal transition (EMT) as the key mechanism in progression to metastatic disease. ABI1, a member of WAVE complex and actin cytoskeleton regulator and adaptor protein, acts as tumor suppressor in prostate cancer but the role of ABI1 in EMT is not clear. Methods To investigate the molecular mechanism by which loss of ABI1 contributes to tumor progression, we disrupted the ABI1 gene in the benign prostate epithelial RWPE-1 cell line and determined its phenotype. Levels of ABI1 expression in prostate organoid tumor cell lines was evaluated by Western blotting and RNA sequencing. ABI1 expression and its association with prostate tumor grade was evaluated in a TMA cohort of 505 patients and metastatic cell lines. Results Low ABI1 expression is associated with biochemical recurrence, metastasis and death (p = 0.038). Moreover, ABI1 expression was significantly decreased in Gleason pattern 5 vs. pattern 4 (p = 0.0025) and 3 (p = 0.0012), indicating an association between low ABI1 expression and highly invasive prostate tumors. Disruption of ABI1 gene in RWPE-1 cell line resulted in gain of an invasive phenotype, which was characterized by a loss of cell-cell adhesion markers and increased migratory ability of RWPE-1 spheroids. Through RNA sequencing and protein expression analysis, we discovered that ABI1 loss leads to activation of non-canonical WNT signaling and EMT pathways, which are rescued by re-expression of ABI1. Furthermore, an increase in STAT3 phosphorylation upon ABI1 inactivation and the evidence of a high-affinity interaction between the FYN SH2 domain and ABI1 pY421 support a model in which ABI1 acts as a gatekeeper of non-canonical WNT-EMT pathway activation downstream of the FZD2 receptor. Conclusions ABI1 controls prostate tumor progression and epithelial plasticity through regulation of EMT-WNT pathway. Here we discovered that ABI1 inhibits EMT through suppressing FYN-STAT3 activation downstream from non-canonical WNT signaling thus providing a novel mechanism of prostate tumor suppression.

AML Survival and In Vivo Progression Is Dependent On β-Catenin Signaling.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2398-2398
Author(s):  
Elena K Siapati ◽  
Magda Papadaki ◽  
Zoi Kozaou ◽  
Erasmia Rouka ◽  
Evridiki Michali ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Wnt Signaling ◽  
Signaling Pathway ◽  
Cell Lines ◽  
Wnt Signaling Pathway ◽  
Canonical Wnt Signaling ◽  
Down Regulation ◽  
Canonical Wnt

Abstract Abstract 2398 Poster Board II-375 B-catenin is the central effector molecule of the canonical wnt signaling pathway which governs cell fate and differentiation during embryogenesis as well as self-renewal of hematopoietic stem cells. Deregulation of the pathway has been observed in various malignancies including myeloid leukemias where over-expression of β-catenin is an independent adverse prognostic factor. In the present study we examined the functional outcome of stable β-catenin down-regulation through lentivirus-mediated expression of short hairpin RNA (shRNA). Reduction of the β-catenin levels in AML cell lines and patient samples diminished their in vitro proliferation ability without significantly affecting cell viability. In order to study the role of β-catenin in vivo, we transplanted leukemic cell lines with control or reduced levels of β-catenin in NOD/SCID animals and analyzed the engraftment levels in the bone marrow. We observed that while the immediate homing of the cells was not affected by the β-catenin levels, the bone marrow engraftment was directly dependent on its levels. Subsequent examination of bone marrow sections revealed that the reduced engraftment was partly due to the inability of the cells with lower β-catenin levels to dock to the endosteal niches, a finding that was confirmed in competitive repopulation assays with untransduced cells. When we examined the expression levels of adhesion molecules and integrins in engrafted cells in vivo, we observed a significant down-regulation of CD44 expression, a molecule that participates in the interaction of HSCs with the niche. Gene expression analysis of the components of the wnt signaling pathway showed that the pathway is subject to tight transcriptional regulation with minor expression deviations. We did, however, observe an up-regulation in components that participate in the non-canonical wnt signaling pathways such as the WNT5B ligand. Ongoing experiments in normal cord blood CD34+ cells will determine the in vivo role of β-catenin signaling in normal hematopoietic progenitors. In conclusion, our study showed that β-catenin comprises an integral part in the development and progression of AML in vivo, indicating that manipulation of the wnt pathway may hold a therapeutic potential in the management of AML. Disclosures: No relevant conflicts of interest to declare.

Bortezomib Induces Activation of b-Catenin/TCF Signaling Pathway in Multiple Myeloma

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1851-1851
Author(s):  
Ya-Wei Qiang ◽  
Bo Hu ◽  
Yu Chen ◽  
Wei Qiang ◽  
Christoph Heuck ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Wnt Signaling ◽  
Signaling Pathway ◽  
Cell Lines ◽  
Proteasome Inhibitor ◽  
Transcriptional Activity ◽  
Luciferase Reporter ◽  
Canonical Wnt Signaling ◽  
Canonical Wnt ◽  
Dose Dependent

Abstract Abstract 1851 Background: The proteasome inhibitor Bortezomib (Bz) shows significant activity in Multiple Myeloma (MM) by acting on MM cell directly as well as by augmenting bone formation in vitro and in vivo. Its effect on the bone could be traced to promoting differentiation of mesenchymal stem cells into osteoblast cells by regulating BMP2 and canonical Wnt signaling. However, the molecular mechanism mediating the direct anti-MM activity of Bz remains to be fully understood. Initially the rationale for the use of Bz in MM was inhibition of NF-kB signaling, yet subsequent studies showed that Bz actually induces activation of this pathway. In this study, we examined whether Bz regulates the activity of canonical Wnt signaling pathway in MM and whether the growth-inhibition effect of Bz was associated with activation of this pathway by using multiple MM cell lines including EJM, H929, INA6, KMS28BM, JJN3, L363, OPM1, OPM2, RPMI8226, UTMC, XG2 and XG6 as well as primary plasma cells (PC) from six patients with newly diagnosed MM. Methods/Results: Immunoblotting demonstrated that Bz induces stabilization of b-catenin protein in three MM cell lines (H929, OPM2 and UTMC) in a time- and dose-dependent manner. These changes were not seen when the same cell lysate were immunoblotted for other catenin family members, a-catenin and g-catenin. Increased levels of b-catenin protein response to Bz treatment were observed in other 9 MM cell lines (EJM, INA6, KMS28BM, JJN3, L363, OPM1, RPMI8226, XG2 and XG6) and in the 6 CD138+ sorted bone marrow PC from patients with MM. To determine if Bz regulation of b-catenin level is a specific effect of the inhibition of 26S proteasome subunit we treated the same MM cell lines with another proteasome inhibitor, MG132. Similar results were observed in response to MG132 for all four MM cell lines, suggesting the effect of Bz on b-catenin protein is 26S proteosome inhibitor specific. Increases in b-catenin protein levels in MM cells were not due to increased Ctnnb1/CTNNB (b-catenin) gene transcription as b-catenin mRNA did not change in these cells treated with Bz. These results indicate that proteasome inhibition increases b-catenin is independent of transcriptional upregulation. To determine whether Bz induces the nuclear localization and transcriptional activity of b-catenin, cells were incubated with Bz for 6 hours and then fractionated to separate the nuclear and cytoplasmic fractions. Treatment with Bz resulted an increase in nuclear b-catenin as well as b-catenin in cytoplasm in four cell lines including H929, INA6, OPM1 and MM144. Increase in cytoplasmic and nuclear b-catenin was further confirmed by immunofluorescence with antibodies specific for active form of b-catenin. To determine whether Bz affects b-catenin-mediated transcriptional activity, we used a TCF/LEF luciferase reporter construct cloned in lentiviral vector. OPM2 cells were infected with lentiviral particle containing the TCF reporter or containing empty vector and were then treated with serial concentrations of Bz. The luciferase activity exhibited a dose-dependent response to Bz analogous to the stabilization of b-catenin. Similar results were observed in 7 out of 8 MM cell lines compared with untreated control. Stimulation of TCF transcriptional activity by Bz was independent of modifiers of extracellular Wnt ligands, such as Frizzled receptors, LRP5/6 co-receptors and sFRPs or the activation of intracellular GSK3b. Conclusion: These results indicate that Bz augments activation of canonical Wnt signaling by preventing b-catenin protein from proteosome-mediated degradation in MM cells. Concentrations of Bz for stimulating TCF transcriptional activity are comparable to those being used to induce inhibition of MM proliferation. Experiments modulating cytoplasmic as well as the nuclear players and interactions of the Wnt-pathway are ongoing to determine if Bz mediated activation of b-catenin signaling is responsible for its direct anti-MM effect. Disclosures: Barlogie: Celgene, Genzyme, Novartis, Millennium: Consultancy, Honoraria, Patents & Royalties. Shaughnessy:Myeloma Health, Celgene, Genzyme, Novartis: Consultancy, Employment, Equity Ownership, Honoraria, Patents & Royalties.

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