[Show abstract][Hide abstract] ABSTRACT: Glucocorticoid-induced TNF receptor (GITR) plays a crucial role in modulating immune response and inflammation, however the role of GITR in human cancers is poorly understood. In this study, we demonstrated that GITR is inactivated during tumor progression in Multiple Myeloma (MM) through promoter CpG island methylation, mediating gene silencing in primary MM plasma cells and MM cell lines. Restoration of GITR expression in GITR deficient MM cells led to inhibition of MM proliferation in vitro and in vivo and induction of apoptosis. These findings were supported by the presence of induction of p21 and PUMA, two direct downstream targets of p53, together with modulation of NF-κB in GITR-overexpressing MM cells. Moreover, the unbalanced expression of GITR in clonal plasma cells correlated with MM disease progression, poor prognosis and survival. These findings provide novel insights into the pivotal role of GITR in MM pathogenesis and disease progression.
PLoS ONE 06/2013; 8(6):e66982. DOI:10.1371/journal.pone.0066982 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: miR-155 acts as an oncogenic miR in B-cell lymphoproliferative disorders, including Waldenstrom macroglobulinemia (WM) and chronic lymphocytic leukemia, and is therefore a potential target for therapeutic intervention. However, efficient targeting of miRs in tumor cells in vivo remains a significant challenge for the development of miR-155-based therapeutics for the treatment of B-cell malignancies. In the present study, we show that an 8-mer locked nucleic acid anti-miR-155 oligonucleotide targeting the seed region of miR-155 inhibits WM and chronic lymphocytic leukemia cell proliferation in vitro. Moreover, anti-miR-155 delivered systemically showed uptake in the BM CD19(+) cells of WM-engrafted mice, resulting in the up-regulation of several miR-155 target mRNAs in these cells, and decreased tumor growth significantly in vivo. We also found miR-155 levels to be elevated in stromal cells from WM patients compared with control samples. Interestingly, stromal cells from miR-155-knockout mice led to significant inhibition of WM tumor growth, indicating that miR-155 may also contribute to WM proliferation through BM microenvironmental cells. The results of the present study highlight the therapeutic potential of anti-miR-155-mediated inhibition of miR-155 in the treatment of WM.
[Show abstract][Hide abstract] ABSTRACT: The spread of multiple myeloma (MM) involves (re)circulation into the peripheral blood and (re)entrance or homing of MM cells into new sites of the BM. Hypoxia in solid tumors was shown to promote metastasis through activation of proteins involved in the epithelial-mesenchymal transition (EMT) process. We hypothesized that MM-associated hypoxic conditions activate EMT-related proteins and promote metastasis of MM cells. In the present study, we have shown that hypoxia activates EMT-related machinery in MM cells, decreases the expression of E-cadherin, and, consequently, decreases the adhesion of MM cells to the BM and enhances egress of MM cells to the circulation. In parallel, hypoxia increased the expression of CXCR4, consequently increasing the migration and homing of circulating MM cells to new BM niches. Further studies to manipulate hypoxia to regulate tumor dissemination as a therapeutic strategy are warranted.
[Show abstract][Hide abstract] ABSTRACT: The ephrin receptors (Eph) are found in a wide range of cancers and correlate with metastasis. In this study, we characterized the role of Eph-B2 receptor in the interaction of Waldenstrom's macroglobulinemia (WM) cells with the bone marrow microenvironment.
We screened the activity of different receptor tyrosine kinases in WM patients and found that Eph-B2 was overexpressed compared with control. Also, we tested the expression of ephrin-B2 ligand on endothelial cells and bone marrow stromal cells (BMSC) isolated from WM patients. We then tested the role of Eph-B2/Ephrin-B2 interaction in the adhesion of WM cells to endothelial cells and BMSCs; the cell signaling induced by the coculture in both the WM cells and the endothelial cells; WM cell proliferation, apoptosis, and cell cycle in vitro and tumor progression in vivo; and in angiogenesis.
Eph-B2 receptor was found to be activated in WM patients compared with control, with a 5-fold increase in CD19(+) WM cells, and activated cell adhesion signaling, including focal adhesion kinase, Src, P130, paxillin, and cofilin, but decreased WM cell chemotaxis. Ephrin-B2 ligand was highly expressed on endothelial cells and BMSCs isolated from WM patients and on human umbilical vein endothelial cells and induced signaling in the endothelial cells promoting adhesion and angiogenesis. Blocking of ephrin-B2 or Eph-B2 inhibited adhesion, cytoskeletal signaling, proliferation, and cell cycle in WM cells, which was induced by coculture with endothelial cells and decreased WM tumor progression in vivo.
Ephrin-B2/Eph-B2 axis regulates adhesion, proliferation, cell cycle, and tumor progression in vivo through the interaction of WM with the cells in the bone marrow microenvironment.
Clinical Cancer Research 01/2012; 18(1):91-104. DOI:10.1158/1078-0432.CCR-11-0111 · 8.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Interactions between multiple myeloma (MM) cells and the BM microenvironment play a critical role in the pathogenesis of MM and in the development of drug resistance by MM cells. Selectins are involved in extravasation and homing of leukocytes to target organs. In the present study, we focused on adhesion dynamics that involve P-selectin glycoprotein ligand-1 (PSGL-1) on MM cells and its interaction with selectins in the BM microenvironment. We show that PSGL-1 is highly expressed on MM cells and regulates the adhesion and homing of MM cells to cells in the BM microenvironment in vitro and in vivo. This interaction involves both endothelial cells and BM stromal cells. Using loss-of-function studies and the small-molecule pan-selectin inhibitor GMI-1070, we show that PSGL-1 regulates the activation of integrins and downstream signaling. We also document that this interaction regulates MM-cell proliferation in coculture with BM microenvironmental cells and the development of drug resistance. Furthermore, inhibiting this interaction with GMI-1070 enhances the sensitization of MM cells to bortezomib in vitro and in vivo. These data highlight the critical contribution of PSGL-1 to the regulation of growth, dissemination, and drug resistance in MM in the context of the BM microenvironment.
[Show abstract][Hide abstract] ABSTRACT: Mammalian target of rapamycin (mTOR) is a downstream serine/threonine kinase of the PI3K/Akt pathway that integrates signals from the tumor microenvironment to regulate multiple cellular processes. Rapamycin and its analogs have not shown significant activity in multiple myeloma (MM), likely because of the lack of inhibition of TORC2. In the present study, we investigated the baseline activity of the PI3K/Akt/mTOR pathway TORC1/2 in MM cell lines with different genetic abnormalities. TORC1/2 knock-down led to significant inhibition of the proliferation of MM cells, even in the presence of BM stromal cells. We also tested INK128, a dual TORC1/2 inhibitor, as a new therapeutic agent against these MM cell lines. We showed that dual TORC1/2 inhibition is much more active than TORC1 inhibition alone (rapamycin), even in the presence of cytokines or stromal cells. In vitro and in vivo studies showed that p-4EBP1 and p-Akt inhibition could be predictive markers of TORC2 inhibition in MM cell lines. Dual TORC1/2 inhibition showed better inhibition of adhesion to BM microenvironmental cells and inhibition of homing in vivo. These studies form the basis for further clinical testing of TORC1/2 inhibitors in MM.
[Show abstract][Hide abstract] ABSTRACT: Waldenstrom macroglobulinemia (WM) is a low-grade B-cell lymphoproliferative disorder characterized primarily by specific homing and growth of tumor cells within the bone marrow niches. The progressive growth of tumor cells throughout the bone marrow indicates that the tumor cells are capable of homing and adhering to specific niches that allow growth, survival and drug resistance. In this review we highlight the interaction of the tumor cells in WM and the bone marrow microenvironment including bone marrow stromal cells, endothelial cells and mast cells. Migration, adhesion and downstream activation of signaling pathways leads to cell trafficking and cell dissemination in WM. Future therapeutic agents need to target not only the tumor clone, but also its close interaction with the bone marrow microenvironment.
[Show abstract][Hide abstract] ABSTRACT: Waldenstrom macroglobulinemia (WM) is a low-grade B-cell lymphoma characterized by widespread involvement of the bone marrow with lymphoplasmacytic cells. In approximately 20% of patients, the malignant clone also involves the lymph nodes and induces hepatosplenomegaly. The mechanisms by which the tumor cells home to the bone marrow and preferentially reside in the marrow niches are not fully elucidated. In this review, we examine the role of the bone marrow microenvironment in the regulation of cell growth, survival and cell dissemination in WM. We also summarize specific regulators of niche-dependent tumor proliferation in WM. These include chemokines, adhesion molecules, Src/PI3K/Akt/mTOR signaling, NF-kB activation, and micro-RNA regulation in WM. Targeting these pathways in clinical trials could lead to significant responses in this rare disease.
[Show abstract][Hide abstract] ABSTRACT: There is no standard of therapy for the treatment of Waldenström macroglobulinemia (WM), therefore there is a need for the development of new agents. Fibroblast growth factor receptor 3 (FGFR3) was shown to play a major role in several types in cancer. Dovitinib, an inhibitor of FGFR3, was effective in hematologic malignancies. In this study, we tested FGFR3 as a therapeutic target in WM and tested the effect of dovitinib on cell proliferation and apoptosis of WM cells in the context of BM microenvironment. Methods: The expression of FGFR3 in WM cells was tested using immunofluorescence and flow cytometry. Cell signaling in response to stimulation with FGF3 and stromal cells, and its inhibition by dovitinib was performed using immunoblotting. Cell survival and cell proliferation were assessed by MTT and BrdU assays. Apoptosis was measured by detection of APO-2.7 and cleavage of caspase-3 using flow cytometry. Cell cycle was performed by PI staining of cells and flow cytometry. The combinatory effect of dovitinib with other drugs was analyzed using Calcusyn software. The effect of dovitinib was tested in vivo.
FGFR3 was overexpressed in WM cells and its activation induced cell proliferation. Inhibition of FGFR3 with dovitinib decreased cell survival, increased apoptosis, and induced cell cycle arrest. Inhibition of FGFR3 by dovitinib reduced the interaction of WM to bone marrow components, and reversed its proliferative effect. Dovitinib had an additive effect with other drugs. Moreover, dovitinib reduced WM tumor progression in vivo.
We report that FGFR3 is a novel therapeutic target in WM, and suggest dovitinib for future clinical trial the treatment of patients with WM.
Clinical Cancer Research 04/2011; 17(13):4389-99. DOI:10.1158/1078-0432.CCR-10-2772 · 8.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The widespread involvement of the bone marrow with tumor cells indicates that there is continuous cell trafficking of WM cells in and out of the bone marrow leading to cell dissemination in the bone marrow and in the lymph nodes in many patients with WM. The interaction of the WM cells with the bone marrow is critical for the regulation of cell proliferation, cell cycle, drug resistance as well as cell dissemination and trafficking. Advances in understanding the interaction of the tumor clone with the BM microenvironment have led to the development of therapeutic agents that not only target the tumor clone but also regulate the bone marrow microenvironment. Here, we review the role of the cellular and liquid bone marrow compartments in the regulation of cell proliferation and dissemination in WM.
[Show abstract][Hide abstract] ABSTRACT: Epigenetics represent heritable changes in gene expression that are not due to any alteration in the DNA sequence. One of the best-known epigenetic markers is histone acetylation, which has been shown to be deregulated in neoplastic diseases, including B-cell malignancies, such as Waldenström's Macroglobulinemia (WM), a low-grade B-cell lymphoma characterized by the presence of lymphoplasmacytic cells in the bone marrow and a serum monoclonal immunoglobulin M in the circulation. It has been recently demonstrated that microRNAs may be responsible for modulating histone acetylation in WM cells, thus providing the preclinical evidences for using microRNA-based therapeutic strategies in this disease.
[Show abstract][Hide abstract] ABSTRACT: Primary Waldenstrom's Macroglobulinemia (WM) cells present with a significantly higher level of the immunoproteasome compared with the constitutive proteasome. It has been demonstrated that selective inhibition of the chymotrypsin-like (CT-L) activity of constitutive-(c20S) and immuno-(i20S) proteasome represents a valid strategy to induce antineoplastic effect in hematologic tumors. We therefore evaluated carfilzomib, a potent selective, irreversible inhibitor of the CT-L activity of the i20S and c20S in WM cells.
We tested the effect of carfilzomib on survival and proliferation of primary WM cells, as well as of other IgM-secreting lymphoma cell lines. Carfilzomib-dependent mechanisms of induced apoptosis in WM cells, and its effect on WM cells in the context of bone marrow (BM) microenvironment have been also evaluated. Moreover, the combinatory effect of carfilzomib and bortezomib has been investigated. In vivo studies have been performed.
We demonstrated that carfilzomib targeted the CT-L activity of both i20S and c20S, which led to the induction of toxicity in primary WM cells, as well as in other IgM-secreting lymphoma cells. Importantly, carfilzomib targeted WM cells even in the context of BM milieu. In addition, carfilzomib induced apoptosis through c-jun-N-terminal-kinase activation, caspase cleavage, and initiation of unfolded protein response. Importantly, the combination of carfilzomib and bortezomib synergistically inhibited CT-L activity, as well as caspase-, PARP-cleavage and GRP94 expression. Antitumor activity of carfilzomib has been validated in vivo.
These findings suggest that targeting i20S and c20S CT-L activity by carfilzomib represents a valid antitumor strategy in WM and other IgM-secreting lymphomas.
Clinical Cancer Research 02/2011; 17(7):1753-64. DOI:10.1158/1078-0432.CCR-10-2130 · 8.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Waldenström macroglobulinemia (WM) cells present with increased expression of microRNA-206 (miRNA-206) and reduced expression of miRNA-9*. Predicted miRNA-206- and -9*-targeted genes include histone deacetylases (HDACs) and histone acetyl transferases (HATs), indicating that these miRNAs may play a role in regulating histone acetylation. We were able to demonstrate that primary WM cells are characterized by unbalanced expression of HDACs and HATs, responsible for decreased acetylated histone-H3 and -H4, and increased HDAC activity. We next examined whether miRNA-206 and -9* modulate the aberrant expression of HDAC and HATs in WM cells leading to increased transcriptional activity. We found that restoring miRNA-9* levels induced toxicity in WM cells, supported by down-modulation of HDAC4 and HDAC5 and up-regulation of acetyl-histone-H3 and -H4. These, together with inhibited HDAC activity, led to induction of apoptosis and autophagy in WM cells. To further confirm that miRNA-9*-dependent modulation of histone acetylation is responsible for induction of WM cytotoxicity, a novel class of HDAC inhibitor (LBH589) was used; we confirmed that inhibition of HDAC activity leads to toxicity in this disease. These findings confirm that histone-modifying genes and HDAC activity are deregulated in WM cells, partially driven by the aberrant expression of miRNA-206 and -9* in the tumor clone.
[Show abstract][Hide abstract] ABSTRACT: Proteasome inhibition represents a valid antitumor approach and its use has been validated in Waldenström macroglobulinemia (WM), where bortezomib has been successfully tested in clinical trials. Nevertheless, a significant fraction of patients relapses, and many present toxicity due to its off-target effects. Selective inhibition of the chymotrypsin-like (CT-L) activity of constitutive proteasome 20S (c20S) and immunoproteasome 20S (i20S) represents a sufficient and successful strategy to induce antineoplastic effect in hematologic tumors. We therefore studied ONX0912, a novel selective, irreversible inhibitor of the CT-L activity of i20S and c20S. Primary WM cells express higher level of i20S compared with c20S, and that ONX0912 inhibited the CT-L activity of both i20S and c20S, leading to induction of toxicity in primary WM cells, as well as of apoptosis through c-Jun N-terminal kinase activation, nuclear factor kappaB (NF-kappaB) inhibition, caspase cleavage, and initiation of the unfolded protein response. Importantly, ONX0912 exerted toxicity in WM cells, by reducing bone marrow (BM)-derived interleukin-6 (IL-6) and insulin-like growth factor 1 (IGF-1) secretion, thus inhibiting BM-induced p-Akt and phosphorylated extracellular signal-related kinase (p-ERK) activation in WM cells. These findings suggest that targeting i20S and c20S CT-L activity by ONX0912 represents a valid antitumor therapy in WM.
[Show abstract][Hide abstract] ABSTRACT: We have previously shown clinical activity of a mammalian target of rapamycin (mTOR) complex 1 inhibitor in Waldenstrom macroglobulinemia (WM). However, 50% of patients did not respond to therapy. We therefore examined mechanisms of activation of the phosphoinositide 3-kinase (PI3K)/Akt/mTOR in WM, and mechanisms of overcoming resistance to therapy. We first demonstrated that primary WM cells show constitutive activation of the PI3K/Akt pathway, supported by decreased expression of phosphate and tensin homolog tumor suppressor gene (PTEN) at the gene and protein levels, together with constitutive activation of Akt and mTOR. We illustrated that dual targeting of the PI3K/mTOR pathway by the novel inhibitor NVP-BEZ235 showed higher cytotoxicity on WM cells compared with inhibition of the PI3K or mTOR pathways alone. In addition, NVP-BEZ235 inhibited both rictor and raptor, thus abrogating the rictor-induced Akt phosphorylation. NVP-BEZ235 also induced significant cytotoxicity in WM cells in a caspase-dependent and -independent manner, through targeting the Forkhead box transcription factors. In addition, NVP-BEZ235 targeted WM cells in the context of bone marrow microenvironment, leading to significant inhibition of migration, adhesion in vitro, and homing in vivo. These studies therefore show that dual targeting of the PI3K/mTOR pathway is a better modality of targeted therapy for tumors that harbor activation of the PI3K/mTOR signaling cascade, such as WM.
[Show abstract][Hide abstract] ABSTRACT: Waldenstrom macroglobulinemia is a lymphoplasmacytic lymphoma characterized by widespread involvement of the bone marrow. Despite different options of therapy, Waldenstrom macroglobulinemia is still incurable. Src tyrosine kinase has been shown to play a central role in the regulation of a variety of biological processes, such as cell proliferation, migration, adhesion, and survival in solid tumors. We sought to determine whether the protein tyrosine kinase Src regulates adhesion, migration, and survival in Waldenstrom macroglobulinemia.
We tested the expression of Src tyrosine kinase in Waldenstrom macroglobulinemia and normal cells, and the effect of the specific Src inhibitor AZD0530 on the adhesion, migration, cell cycle, and survival of a Waldenstrom macroglobulinemia cell line and patient samples. Moreover, we tested the effect of AZD0530 on cytoskeletal and cell cycle signaling in Waldenstrom macroglobulinemia.
We show that Src is overexpressed in Waldenstrom macroglobulinemia cells compared with control B cells, and that the use of the Src inhibitor AZD0530 led to significant inhibition of adhesion, migration, and cytoskeletal signaling induced by SDF1. Moreover, inhibition of Src activity induced G(1) cell cycle arrest; however, it had minimal effect on survival of Waldenstrom macroglobulinemia cells, and no significant effect on survival of normal cells.
Taken together, these results delineate the role of Src kinase activity in Waldenstrom macroglobulinemia and provide the framework for future clinical trials using Src inhibitors in combination with other drugs to improve the outcome of patients with Waldenstrom macroglobulinemia.
Clinical Cancer Research 09/2009; 15(19):6035-41. DOI:10.1158/1078-0432.CCR-09-0718 · 8.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The interaction of multiple myeloma (MM) cells with the bone marrow (BM) milieu plays a crucial role in MM pathogenesis. Stromal cell-derived factor-1 (SDF1) regulates homing of MM cells to the BM. In this study, we examined the role of RhoA and Rac1 GTPases in SDF1-induced adhesion and chemotaxis of MM. We found that both RhoA and Rac1 play key roles in SDF1-induced adhesion of MM cells to BM stromal cells, whereas RhoA was involved in chemotaxis and motility. Furthermore, both ROCK and Rac1 inhibitors reduced SDF1-induced polymerization of actin and activation of LIMK, SRC, FAK, and cofilin. Moreover, RhoA and Rac1 reduced homing of MM cells to BM niches. In conclusion, we characterized the role of RhoA and Rac1 GTPases in SDF1-induced adhesion, chemotaxis, and homing of MM cells to the BM, providing the framework for targeting RhoA and Rac1 GTPases as novel MM therapy.
[Show abstract][Hide abstract] ABSTRACT: Detailed genomic studies have shown that cytogenetic abnormalities contribute to multiple myeloma (MM) pathogenesis and disease progression. Nevertheless, little is known about the characteristics of MM at the epigenetic level and specifically how microRNAs regulate MM progression in the context of the bone marrow milieu. Therefore, we performed microRNA expression profiling of bone marrow derived CD138(+) MM cells versus their normal cellular counterparts and validated data by qRT-PCR. We identified a MM-specific microRNA signature characterized by down-expression of microRNA-15a/-16 and overexpression of microRNA-222/-221/-382/-181a/-181b (P < .01). We investigated the functional role of microRNA-15a and -16 and showed that they regulate proliferation and growth of MM cells in vitro and in vivo by inhibiting AKT serine/threonine-protein-kinase (AKT3), ribosomal-protein-S6, MAP-kinases, and NF-kappaB-activator MAP3KIP3. Moreover, miRNA-15a and -16 exerted their anti-MM activity even in the context of the bone marrow milieu in vitro and in vivo. These data indicate that microRNAs play a pivotal role in the biology of MM and represent important targets for novel therapies in MM.
[Show abstract][Hide abstract] ABSTRACT: The paradigm for the treatment of monoclonal gammophaties has dramatically changed: based on the understanding of the complex interaction between tumor cells and bone marrow microenvironment and the signaling pathways that are deregulated in this process, a number of novel therapeutic agents are now available. For example, 3 novel agents with a targeted anti-multiple myeloma activity, have been FDA approved for the treatment of this disease, namely bortezomib, thalidomide, and lenalidomide. The success of targeted therapy in myeloma has led to the development and investigation of more than 30 new compounds in this disease and in other plasma cell dyscrasias such as Waldenström's macroglobulinemia (WM), both in the preclinical settings and as part of clinical trials. Among them the role of proteasome inhibitors has been widely dissected providing the preclinical basis for clinical trials of combinations of proteasome inhibitors in WM.