Extramedullary Waldenström macroglobulinemia

Disease assessment in Waldenstrom Macroglobulinemia (WM) is dependent on the percent involvement of B-cell neoplasm in the bone marrow and IgM paraprotein in the serum. A subset of patients also demonstrates extramedullary involvement, which is infrequently examined. The role of extramedullary involvement in the diagnosis and prognosis of WM is poorly understood. The purpose of this study is to report the characteristics of WM patients with extramedullary disease (EMD). Nine hundred and eight-five patients with WM were evaluated at one academic center and the presence of EMD was assessed in these patients. Forty-three (4.4%) patients were identified to have EMD. Nine (21%) patients presented with involvement at WM diagnosis, while 34 (79%) developed EMD post-therapy for WM. Most frequent EMD sites involved were pulmonary (30%), soft tissue (21%), cerebrospinal fluid (23%), renal (8%), and bone (9%). The median overall survival at 10 years was 79% (95% CI: 57-90%). This is the first study to describe the clinical characteristics, response and overall survival in patients with extramedullary WM. Further studies to define the molecular characteristics of this entity and mechanisms of its development are warranted.

The cancer glycome: carbohydrates as mediators of metastasis

Glycosylation is a frequent post-translational modification which results in the addition of carbohydrate determinants, "glycans", to cell surface proteins and lipids. These glycan structures form the "glycome" and play an integral role in cell-cell and cell-matrix interactions through modulation of adhesion and cell trafficking. Glycosylation is increasingly recognized as a modulator of the malignant phenotype of cancer cells, where the interaction between cells and the tumor micro-environment is altered to facilitate processes such as drug resistance and metastasis. Changes in glycosylation of cell surface adhesion molecules such as selectin ligands, integrins and mucins have been implicated in the pathogenesis of several solid and hematological malignancies, often with prognostic implications. In this review we focus on the functional significance of alterations in cancer cell glycosylation, in terms of cell adhesion, trafficking and the metastatic cascade and provide insights into the prognostic and therapeutic implications of recent findings in this fast-evolving niche.

Abstract PR14: In vivo targeting of stromal-derived factor-1 as a strategy to prevent myeloma cell dissemination to distant bone marrow niches

Background. Multiple myeloma (MM) patients present with multiple lytic lesions at diagnosis, indicating the presence of continuous dissemination of MM cells from the primary site of tumor development to multiple distant bone marrow (BM) niches. We hypothesized that stromal-derived factor-1 (SDF1) may represent a target for preventing transition from MGUS (micrometastatic-stage) to active-MM (macrometastatic-stage). We therefore evaluated SDF1 expression in the BM of patients with MGUS, MM, compared to healthy individuals; and tested NOX-A12, a high affinity L-oligonucleotide binder to SDF1, looking at its ability to modulate MM cell tumor growth and homing to the BM in vivo and in vitro.

Methods. SDF1 levels were evaluated by immunohistochemistry on BM specimens of patients with MGUS, active-MM, or healthy individuals; and confirmed by ELISA, using conditioned-medium of BM-mesenchymal stromal cells (BM-MSCs) from MGUS, active-MM and healthy individuals. BM metastatic lesions from primary epithelial tumors were also evaluated. Co-localization of SDF1 with MM cell (MM.1S-GFP+)-enriched BM niches was evaluated using in vivo confocal microscopy. Effect of NOX-A12 on modulating MM cell dissemination was tested in vivo, by using in vivo MM metastasis model. In vivo homing and in vivo tumor growth of MM cells (MM.1S-GFP+/luc+) was assessed by using in vivo confocal microscopy and bioluminescence, in mice treated with 1) vehicle; 2) NOX-A12; 3) bortezomib; 4) NOX-A12+bortezomib. Effects of drug combination on dissemination of MM cells to distant BM niches was evaluated ex vivo by immunofluorescence on explanted femurs. DNA synthesis and adhesion of MM cells in the context of NOX-A12 treated primary MM BM-MSCs in presence or absence of bortezomib were tested by thymidine uptake and adhesion in vitro assay, respectively. Synergism was calculated by using CalcuSyn software.

Results. Patients with active-MM present with higher BM SDF1 expression vs MGUS patients and healthy individuals. Similarly, BM presenting with metastasis from epithelial primary tumors had higher SDF1 levels compared to healthy subjects, thus suggesting the importance of SDF1 in favoring tumor cell metastasis to BM niches. SDF1 co-localized at BM level with MM tumor cells in vivo. In vitro, NOX-A12 induced a dose-dependent de-adhesion of MM cells from the BMSCs supported by inhibition of BM-MSC-mediated phosphorylation of ERK1/2 and cofilin. Importantly, NOX-A12 induced MM cell mobilization from the BM to the peripheral blood (PB) as shown ex vivo by reduction of MM cells in the BM and increased number of MM cells within the PB compared to control mice (P<.05). This was supported by inhibited homing and dissemination of MM cells to the BM of those mice pre-treated with NOX-A12. NOX-A12 enhanced MM cell sensitivity to bortezomib, in vivo: tumor burden was similar between NOX-A12- and control mice whereas bortezomib-treated mice showed significant reduction in tumor growth vs. control (P<.05); importantly, significant reduction of tumor burden in those mice treated with sequential administration of NOX-A12 and bortezomib was observed, compared to bortezomib-treated mice (P <.05). Similarly, NOX-A12+bortezomib combination induced significant inhibition of MM cell homing, as shown by in vivo confocal microscopy. In vitro studies confirmed synergism between NOX-A12 and bortezomib in modulating MM cell survival and adhesion to BM-MSCs.

Conclusion. SDF-1 represents a valid target for inhibiting MM cell dissemination to distant BM niches, thus providing the evidence for using the SDF1 inhibiting spiegelmer NOX-A12 to target MM cells at the stage of micrometastasis (MGUS), thus preventing development of macrometastatic MM.

This abstract is also presented as Poster B80.

Citation Format: Aldo M. Roccaro, Antonio Sacco, Michele Moschetta, Patricia Maiso, Yuji Mishima, Yosra Aljawai, Fabio Facchetti, Anna Kruschinski, Giuseppe Rossi, Irene M. Ghobrial. In vivo targeting of stromal-derived factor-1 as a strategy to prevent myeloma cell dissemination to distant bone marrow niches. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr PR14. doi:10.1158/1538-7445.CHTME14-PR14

Abstract B62: Stroma-derived exosomes mediate progression in multiple meyloma

Background. Bone marrow (BM)-derived mesenchymal stromal cells (MSCs) support multiple myeloma (MM) cell growth, but little is known about the putative mechanisms that may regulate the interaction between clonal MM plasma cells and the surrounding BM milieu. We characterized the role BM-MSC-derived exosomes as key regulators of MM pathogenesis.

Purpose. 1) To determine the ability of BM-MSCs to release and transfer exosomes to MM cells. 2) To determine the role of BM-MSC-derived exosomes in inducing MM tumor growth and MM cell dissemination

Methods. MSCs were collected from BM of healthy subjects and MM patients, showing a multipotent MSC phenotype (CD34-; CD14-; CD45-; CD19-; CD138-; CD73+; CD90+; CD105+; CD106+). Exosomes were collected from conditioned-medium of normal-BM-MSCs and MM-BM-MSCs, or HS-5 cells; and studied using electron microscopy, immunogold-labeling, and western-blot for CD63 and CD81 detection. Transfer of PKH67-fluorescently-labeled-exosomes to MM cells was evaluated by time-lapse confocal microscopy. Transfer of murine-derived miRNA-containing exosomes into human MM cells was evaluated by qRT-PCR (exosomes were collected from BM-MSCs of C57BL/6 miRNA-15a/16-1-/- or C57BL/6 mice). miRNA expression profiling was obtained from normal (n=4) and MM (n=9) BM-MSCs-derived exosomes (TaqMan-human-miRNA-profiling). Normal and MM BM-MSCs-derived exosomes were loaded into tissue-engineered bones (TEB) with MM.1S-GFP+/Luc+ cells: MM cell homing and MM tumor growth have been tested in vivo by using confocal-microscopy and bioluminescence-imaging (BLI), respectively. Loss- and gain-of-function studies were performed using normal-BM-MSCs, MM-BM-MSCs and HS-5 cells transfected with either pre- or anti-miRNA-15a.

Results. Normal-BM-MSCs and MM-BM-MSCs released CD63+/CD81+ exosomes, as confirmed by electron microscopy, immunogold labeling, and western blot. BM-MSCs exosomes are transferred into MM cells, as shown by confocal microscopy; and further validated by qRT-PCR in human MM cell lines incubated with murine (C57BL/6 miRNA-15a/16-1-/- and wild-type) BM-MSCs-derived exosomes. The impact of normal-BM-MSC- and MM-BM-MSC-derived exosomes on MM cell behavior in vivo was next evaluated. MM cells co-cultured with MM BM-MSC-derived exosomes induced rapid tumor growth at the site of the TEB scaffold, as well as rapid dissemination to distant BM niches, as compared to MM cells co-cultured with exosomes derived from normal BM-MSCs. We next performed miRNA expression profiling on exosomes isolated from MSCs, and found increased expression of 24 miRNAs and reduced expression of 3 miRNAs in MM-BM-MSCs-derived exosomes versus normal (1.5 fold-change; P<0.05). Specifically, miRNA15a was significantly lower in MM-BM-MSC-derived exosomes, similarly to primary MM cells that present with reduced miRNA-15a expression. We therefore sought to examine whether lack of transfer of the tumor suppressor miRNA15a can lead to significant change in tumor growth and dissemination in MM, and found that by over-expressing miRNA-15a in normal BM-MSCs and HS-5 cells inhibited MM cell proliferation and adhesion to fibronectin. Next MM cells were cultured in presence of BM-MSCs isolated from either C57BL/6 mice or C57BL/6 miRNA15a/16-1-/-: miRNA15a-deficient BM-MSCs significantly induced MM cell proliferation (P<0.05). Moreover, exosomes isolated from HS-5 pre-miRNA15a-transfected cells both inhibited MM cell proliferation and reduced their adhesion properties.

Conclusion. These findings demonstrate the existence of exosome-driven interactions between the BM milieu and MM cells, suggesting that exosomes might constitute a novel mechanism for intercellular transfer of miRNAs to MM cells.

Citation Format: Aldo M. Roccaro, Antonio Sacco, Patricia Maiso, Michele Moschetta, Salomon Manier, Yuji Mishima, Michaela Reagan, Yosra Aljawai, Irene M. Ghobrial. Stroma-derived exosomes mediate progression in multiple meyloma. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B62. doi:10.1158/1538-7445.CHTME14-B62

Targeting survival and cell trafficking in multiple myeloma and Waldenstrom macroglobulinemia using pan-class I PI3K inhibitor, buparlisib

The phosphatidylinositol-3 kinase (PI3K) pathway is activated in multiple myeloma (MM) and Waldenstrom Macroglobulenima (WM), and plays a crucial role in tumor progression and drug resistance. In this study, we characterized the role of pan-class I PI3K inhibition on cell trafficking and survival of MM and WM cells. We tested the effect of pan-class I PI3K inhibition by siRNA silencing or pharmacologic inhibition with buparlisib on MM cell survival, apoptosis and cell cycle in vitro and tumor growth and mobilization of MM cells in vivo. We then evaluated buparlisib-dependent mechanisms of induced MM cell mobilization. Moreover, the effect of buparlisib on cell survival, apoptosis, and adhesion of WM cells to bone marrow stromal cells (BMSCs) has been evaluated. We showed that buparlisib induced toxicity in MM cells, supported by induction of apoptosis and cell cycle arrest. Buparlisib was also found to reduce tumor progression in vivo. Importantly, buparlisib enhanced MM cell mobilization in vivo which was driven by decreased adhesion of MM cells to BMSCs and increased chemotaxis via up-regulation of CXCR4 expression. Similar to its effects on MM cells, buparlisib also induced cell survival and apoptosis, and decreased adhesion in WM cells. These data highlight the critical contribution of class I PI3K signaling to the regulation of survival and cell dissemination in B-cell malignancies.

Global epigenetic regulation of microRNAs in multiple myeloma

Epigenetic changes frequently occur during tumorigenesis and DNA hypermethylation may account for the inactivation of tumor suppressor genes in cancer cells. Studies in Multiple Myeloma (MM) have shown variable DNA methylation patterns with focal hypermethylation changes in clinically aggressive subtypes. We studied global methylation patterns in patients with relapsed/refractory MM and found that the majority of methylation peaks were located in the intronic and intragenic regions in MM samples. Therefore, we investigated the effect of methylation on miRNA regulation in MM. To date, the mechanism by which global miRNA suppression occurs in MM has not been fully described. In this study, we report hypermethylation of miRNAs in MM and perform confirmation in MM cell lines using bisulfite sequencing and methylation-specific PCR (MSP) in the presence or absence of the DNA demethylating agent 5-aza-2'-deoxycytidine. We further characterized the hypermethylation-dependent inhibition of miR-152, -10b-5p and -34c-3p which was shown to exert a putative tumor suppressive role in MM. These findings were corroborated by the demonstration that the same miRNAs were down-regulated in MM patients compared to healthy individuals, alongside enrichment of miR-152-, -10b-5p, and miR-34c-3p-predicted targets, as shown at the mRNA level in primary MM cells. Demethylation or gain of function studies of these specific miRNAs led to induction of apoptosis and inhibition of proliferation as well as down-regulation of putative oncogene targets of these miRNAs such as DNMT1, E2F3, BTRC and MYCBP. These findings provide the rationale for epigenetic therapeutic approaches in subgroups of MM.

SDF-1 inhibition targets the bone marrow niche for cancer therapy

Bone marrow (BM) metastasis remains one of the main causes of death associated with solid tumors as well as multiple myeloma (MM). Targeting the BM niche to prevent or modulate metastasis has not been successful to date. Here, we show that stromal cell-derived factor-1 (SDF-1/CXCL12) is highly expressed in active MM, as well as in BM sites of tumor metastasis and report on the discovery of the high-affinity anti-SDF-1 PEGylated mirror-image l-oligonucleotide (olaptesed-pegol). In vivo confocal imaging showed that SDF-1 levels are increased within MM cell-colonized BM areas. Using in vivo murine and xenograft mouse models, we document that in vivo SDF-1 neutralization within BM niches leads to a microenvironment that is less receptive for MM cells and reduces MM cell homing and growth, thereby inhibiting MM disease progression. Targeting of SDF-1 represents a valid strategy for preventing or disrupting colonization of the BM by MM cells.

Altered cytokine and chemokine profiles in multiple myeloma and its precursor disease

Currently, no reliable biomarkers are available to predict transformation from smoldering myeloma (SMM) to multiple myeloma (MM). Using an ultrasensitive enzyme-linked immunosorbent assay (ELISA) we assessed the levels of a broad range of cytokines and chemokines in the peripheral blood (PB) and bone marrow (BM) supernatant collected from 14 SMM and 38 MM patients and compared to healthy donors. We found significantly increased levels of key cytokines, in particular CXCL8 (IL-8), associated with progressive disease state (controls→SMM→MM). Cytokine profiles were found similar in PB and BM. Five of fourteen SMM patients (36%) progressed to MM. Our findings, although based on a limited number of patients, suggest that serum-based cytokines may have a future role as biomarkers for disease progression and could potentially be assessed as novel targets for treatment.

Abstract 4855: Proteomic characterization of the extracellular matrix in multiple myeloma

Background:

The extracellular matrix is a major component of the tumor microenvironment, contributing to the regulation of cell survival, proliferation, differentiation and metastasis. In multiple myeloma (MM) ECM components, such as integrins, fibronectin and collagens, have been shown are critical to the pathogenesis of MM and the development of drug resistance. To date, despite some knowledge of the composition of the ECM in tumors, detailed profiling of the composition of the ECM in MM has not been carried out. Recent advances in proteomics have led to the characterization of the ECM and ECM-related proteins (“matrisome”) in normal human tissues and tumors in a systematic and comprehensive approach.

Methods:

Tumor Xenograft models; MM1S-GFP-Luc+ cells (5x106) were injected intravenously into SCID-Bg mice (n=4/group) and animals underwent weekly bioluminescent imaging (BLI). Mice were sacrificed after two weeks in order to mimic early tumor development (luminescence= 1x105 p/sec/cm2/sr). and compared to mice demonstrating high tumor burden (1x108 p/sec/cm2/sr) 5 weeks post injection. Human bone marrow aspirates; Whole bone marrow was obtained from MM patients (newly diagnosed n=9, relapsed n=9) and healthy human donors (n=9) following written informed consent. Sequential extractions of whole pooled bone marrow from mice and individual bone marrow humans was performed using the CNMCS(Cytosol/Nucleus/Membrane/Cytoskeleton) Compartmental Protein Extraction Kit (Cytomol, CA). Following this, proteins underwent reversed-phase high performance liquid chromatography followed by tandem mass spectrometry (MS). Identified peptide spectra were counted as a semi quantitative measure of abundance.

Results:

We detected a total of 1202, 982 and 329 unique proteins from enriched whole bone marrow samples from relapsed patients, newly diagnosed patients and mice, respectively. Of these, critical ECM components such as laminins, matrix metalloproteinases and collagens were found to be enriched in human MM ECM in comparison to healthy donors with increased abundance apparent with disease progression in mice. Specifically Bone Marrow Proteoglycan and Proteoglycan 3 were amongst the ECM proteins significantly enriched in the ECM of newly diagnosed patients. PRG3 is a p53 responsive gene that has been demonstrated to be upregulated in apoptotic cells in several cancers, including CLL. The ECM protein Elastin, the expression of which is closely associated with the invasive/metastatic potential of various cancer types, was also upregulated in the MM ECM where it may play an important role in the tumor-ECM interaction.

Conclusions:

We have profiled the ECM in MM using mass spectrometry with a view to determining the specific components that may be important in MM disease biology. Through this approach molecular mechanisms that influence MM development and progression can be uncovered and potential targets for therapy identified.

Citation Format: Siobhan V. Glavey, Alexandra Naba, Manuela Gambella, Alberto Rocci, Antonio Sacco, John Asara, Antonio Palumbo, Richard O. Hynes, Aldo M. Roccaro, Irene M. Ghobrial. Proteomic characterization of the extracellular matrix in multiple myeloma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4855. doi:10.1158/1538-7445.AM2014-4855

CXCR7-dependent angiogenic mononuclear cell trafficking regulates tumor progression in multiple myeloma

The CXCR4/stromal cell-derived factor-1 (SDF-1) axis is essential for cell trafficking and has been shown to regulate tumor progression and metastasis in many tumors including multiple myeloma (MM). A second chemokine receptor for SDF-1, CXCR7 was discovered recently and found on activated endothelial cells. We examined the role of CXCR7 in angiogenic mononuclear cells (AMCs) trafficking in MM. Our data demonstrate that AMCs are circulating in patients with MM and in vivo studies show that they specifically home to areas of MM tumor growth. CXCR7 expression is important for regulating trafficking and homing of AMCs into areas of MM tumor growth and neoangiogenesis. We demonstrate that the CXCR7 inhibitor, POL6926, abrogated trafficking of AMCs to areas of MM tumor progression leading to a significant inhibition of tumor progression. These effects were through regulation of endothelial cells and not through a direct tumor effect, indicating that targeting a bone marrow microenvironmental cell can lead to a delay in MM tumor progression. In conclusion, our studies demonstrate that CXCR7 may play an important role in the regulation of tumor progression in MM through an indirect effect on the recruitment of AMCs to areas of MM tumor growth in the bone marrow niche.

Role of endothelial progenitor cells in cancer progression

Tumor-associated neovasculature is a critical therapeutic target; however, despite significant progress made in the clinical efficacy of anti-vessel drugs, the effect of these agents remains transient: over time, most patients develop resistance, which inevitably leads to tumor progression. To develop more effective treatments, it is imperative that we better understand the mechanisms involved in tumor vessel formation, how they participate to the tumor progression and metastasis, and the best way to target them. Several mechanisms contribute to the formation of tumor-associated vasculature: i) neoangiogenesis; ii) vascular co-option; iii) mosaicism; iv) vasculogenic mimicry, and v) postnatal vasculogenesis. These mechanisms can also play a role in the development of resistance to anti-angiogenic drugs, and could serve as targets for designing new anti-vascular molecules to treat solid as well as hematological malignancies. Bone marrow-derived endothelial progenitor cell (EPC)-mediated vasculogenesis represents an important new target, especially at the early stage of tumor growth (when EPCs are critical for promoting the "angiogenic switch"), and during metastasis, when EPCs promote the transition from micro- to macro-metastases. In hematologic malignancies, the EPC population could be related to the neoplastic clone, and both may share a common ontogeny. Thus, characterization of tumor-associated EPCs in blood cancers may provide clues for more specific anti-vascular therapy that has both direct and indirect anti-tumor effects. Here, we review the role of vasculogenesis, mediated by bone marrow-derived EPCs, in the progression of cancer, with a particular focus on the role of these cells in promoting progression of hematological malignancies.

Regulation of microRNAs in cancer metastasis

Metastasis is a phenomenon of crucial importance in defining prognosis in patients with cancer and is often responsible for cancer-related mortality. It is known that several steps are necessary for clonal cells to disseminate from their primary tumor site and colonize distant tissues, thus originating metastatic lesions. Therefore, investigating the molecular actors regulating this process may provide helpful insights in the development of efficient therapeutic responses. Recent evidences have indicated the role of microRNAs (miRNAs) in modulating the metastatic process in solid tumors. miRNAs are small regulatory non-coding RNAs that bind to specific target mRNAs, leading to translational repression. miRNAs are known to act as negative regulators of gene expression and are involved in the regulation of biological processes, including cell growth, differentiation and apoptosis, both in physiological conditions and during diseases, such as tumors. In the specific field of tumorigenesis, miRNAs play an important role in mediating oncogenesis and favoring tumor progression, as a result of their ability to modulate epithelial-to-mesenchymal transition (EMT) and other series of events facilitating the formation of metastasis. The role of miRNAs in cancer development has been widely studied and has helped elucidate events such as the change in expression of oncogenes, tumor-suppressors and cancer-related proteins. This review focuses on the mechanisms underlying the role of miRNAs as part of the metastatic process.

The role of miRNAs in plasma cell dyscrasias

Plasma cell dyscrasias are a group of related disorders that have in common the clonal proliferation of plasma cells with resultant production of a monoclonal immunoglobulin that can be detected on serum protein electrophoresis (M-spike). This term incorporates the Plasma Cell Neoplasms along with other related disorders that are not considered malignant. Comprehensive genomic studies have greatly advanced our understanding of the genetic complexity of these diseases in recent years, however they continue to be considered incurable with a highly heterogeneous phenotype. It is clear that a deeper level of knowledge of the biological events underlying the development of these diseases is needed to identify new targets and generate effective novel therapies. MicroRNAs (miRNAs), which are single strand, 20- nucleotide, non-coding RNAs, are key regulators of gene expression and have been reported to exert transcriptional control in multiple myeloma and other plasma cell dyscrasias. miRNAs are now recognized to play a role in many key areas such as cellular proliferation, differentiation, apoptosis and stress response. Substantial advances have been made in recent years in terms of our understanding of the biological role of miRNAs in this complex and diverse set of disorders, leading to the new information, which is of diagnostic and prognostic relevance.

Novel tumor suppressor function of glucocorticoid-induced TNF receptor GITR in multiple myeloma

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.

BM mesenchymal stromal cell-derived exosomes facilitate multiple myeloma progression

BM mesenchymal stromal cells (BM-MSCs) support multiple myeloma (MM) cell growth, but little is known about the putative mechanisms by which the BM microenvironment plays an oncogenic role in this disease. Cell-cell communication is mediated by exosomes. In this study, we showed that MM BM-MSCs release exosomes that are transferred to MM cells, thereby resulting in modulation of tumor growth in vivo. Exosomal microRNA (miR) content differed between MM and normal BM-MSCs, with a lower content of the tumor suppressor miR-15a. In addition, MM BM-MSC-derived exosomes had higher levels of oncogenic proteins, cytokines, and adhesion molecules compared with exosomes from the cells of origin. Importantly, whereas MM BM-MSC-derived exosomes promoted MM tumor growth, normal BM-MSC exosomes inhibited the growth of MM cells. In summary, these in vitro and in vivo studies demonstrated that exosome transfer from BM-MSCs to clonal plasma cells represents a previously undescribed and unique mechanism that highlights the contribution of BM-MSCs to MM disease progression.

Mechanisms of activity of the TORC1 inhibitor everolimus in Waldenstrom macroglobulinemia

PURPOSE

The TORC1 inhibitor everolimus has previously shown significant activity as a single agent in hematologic malignancies, with reported responses of 30% to 70% in Waldenstrom macroglobulinemia. However, the specific mechanisms by which this class of mTOR inhibitors exerts anti-Waldenstrom macroglobulinemia activity have not been fully investigated. We therefore sought to dissect the mechanisms of everolimus-dependent modulation of Waldenstrom macroglobulinemia cell survival.

EXPERIMENTAL DESIGN

We confirmed that everolimus targets mTOR in patients treated with everolimus and responding to therapy. We evaluated the effect of everolimus on proliferation and survival of primary Waldenstrom macroglobulinemia cells, as well as of other IgM-secreting lymphoma cell lines. Everolimus-dependent mechanisms of induced apoptosis and its effect on Waldenstrom macroglobulinemia cells in the context of bone marrow microenvironment have been also evaluated. miRNA-155 loss-of-function studies were conducted. Moreover, the combinatory effect of bortezomib and rituximab has been tested.

RESULTS

We showed that everolimus targeted mTOR downstream signaling pathways, ex vivo, in patients responding to everolimus treatment. Everolimus induced toxicity in primary Waldenstrom macroglobulinemia cells, as well as in other IgM-secreting lymphoma cells, supported by cell-cycle arrest and caspase-dependent and -independent induction of apoptosis. Importantly, everolimus targeted Waldenstrom macroglobulinemia cells even in the context of bone marrow milieu, where it affected migration, adhesion, and angiogenesis. Everolimus-dependent anti-Waldenstrom macroglobulinemia activity was partially driven by miRNA-155. Moreover, everolimus synergized with bortezomib and rituximab in targeting Waldenstrom macroglobulinemia cells, as shown by synergistic inhibition of p65/ and p50/NF-κB activities.

CONCLUSIONS

These findings provide a better understanding of the mechanisms that are responsible for everolimus-induced anti-Waldenstrom macroglobulinemia activity.

Anti-angiogenic therapies in the treatment of Waldenstrom's Macroglobulinemia

Bone marrow microenvironment has been shown to play a crucial role in supporting the pathogenesis and the progression of several B-cell malignancies, including Waldenstrom's Macroglobulinemia (WM). Among the different cell types within the bone marrow milieu, endothelial cells have been proven to support WM cells growth. Based on the understanding of bone marrow neo-angiogenesis in plasma cell dyscrasias, a number of anti-angiogenic molecules are now available for the treatment of these diseases. Indeed, anti-angiogenic drugs, such as proteasome-, proteins kinase-C (PKC)-, phosphatidylinositol 3-kinase/mammalian target of rapamycin (mTOR)-, and histone deacetylase (HDAC)- inhibitors are now available, playing a key role in the treatment of WM both in the preclinical settings and as part of clinical trials.

Cell Trafficking in Multiple Myeloma

Multiple myeloma (MM) is an incurable cancer of terminally differentiated plasma cells (PC) and represents the second most frequent hematologic malignancy in the western world. MM cells localize preferentially to the bone marrow where they interact closely with bone marrow stroma cells (BMSC) and extracellular matrix (ECM) proteins in a reciprocal pro-survival loop. Such a bone marrow niche guarantees a survival advantage for MM cells and has a crucial role in mediating drug resistance to chemotherapy agents. As the name suggests, hallmark characteristic of MM is the ability to localize in multiple, distant bone sites causing disruption of the normal bone architecture and impairment of normal hematopoiesis. The pathogenic mechanisms of MM rely then not only on proliferation of cancerous cells, but also on the ability of myeloma cells to traffic between sites and home to appropriate survival niches. Identifying the mechanisms that regulate the homing of MM cells to the bone marrow, the MM-BMSC interaction and the trafficking of MM cells from the bloodstream to distant bone locations is therefore crucial to design new, more effective therapies capable of overcoming the maladaptive interaction between BMSCs and MM and help in finding a cure for MM.

Eph-B2/ephrin-B2 interaction plays a major role in the adhesion and proliferation of Waldenstrom's macroglobulinemia

PURPOSE

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.

EXPERIMENTAL DESIGN

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.

RESULTS

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.

CONCLUSION

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.

Targeting the bone marrow in Waldenstrom macroglobulinemia

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.

New insights into the pathogenesis and treatment of Waldenstrom macroglobulinemia

PURPOSE OF REVIEW

Waldenstrom macroglobulinemia is a distinct low-grade lymphoproliferative disease. There have been recent significant advances in understanding the underlying pathogenesis of this disease, including genetic and epigenetic regulators of tumor progression.

RECENT FINDINGS

Current studies have shown that the tumor microenvironment plays a critical role in cell proliferation, dissemination, and drug resistance.

SUMMARY

This review provides an update of the advances in the pathogenesis of factors both intrinsic (in the tumor clone) and extrinsic (in the bone marrow microenvironment) that regulate tumor progression in Waldenstrom macroglobulinemia. We next discuss novel agents that have been recently tested in clinical trials based on the advances observed in the pathogenesis of Waldenstrom macroglobulinemia.

Role of microRNAs from monoclonal gammopathy of undetermined significance to multiple myeloma

microRNAs (miRNAs) are increasingly recognized as significant players in oncogenesis and tumor biology through post-transcriptional gene regulation impacting broad pathways of proliferation, differentiation, apoptosis, metastasis, and cell survival. Recent studies have found abnormal expression of miRNAs in multiple myeloma (MM). Currently, the precise role of these miRNAs in the biology of MM remains to be elucidated, although they are predicted to be involved in plasma cell proliferation, survival, homing, or in MM cell interactions with the bone marrow microenvironment. Furthermore, a limited number of studies focusing on MM precursor disease (monoclonal gammopathy of undetermined significance [MGUS]) reveal significant differences in miRNA profiles between MGUS and normal plasma cells. Interestingly, several of the microRNAs differentially expressed in MGUS also show aberrant expression in MM, suggesting a role in early myelomagenesis. miRNA profiles can discriminate molecular subtypes of MM that are defined based on gene expression profiling (GEP) and cytogenetic abnormalities, demonstrating the potential diagnostic/prognostic utility of miRNA profiling for subclassification of MM. Given the relative stability of miRNA and ability to isolate miRNA from routine clinical specimens, miRNA analysis promises to facilitate personalized diagnostics and therapies, and to provide insights into the biology of early myelomagenesis.

Advances in the treatment of monoclonal gammopaties: The emerging role of targeted therapy in plasma cell dyscrasias

The paradigm for the treatment of monoclonal gammopaties has dramatically changed: therapeutic options in multiple myeloma (MM) have evolved from the introduction of melphalan and prednisone in the 1960s, high-dose chemotherapy and stem cell transplantation in the late 1980s and 1990s, to the rapid introduction of small novel molecules within the last seven years. Based on the understanding of the complex interaction of the MM cells with the bone marrow microenvironment and the signaling pathways that are dysregulated in this process, a number of novel therapeutic agents are now available. Specifically, three novel agents with a specific-targeted anti-MM activity, have been FDA-approved for the treatment of this disease, namely Bortezomib, thalidomide, and lenalidomide which are now all playing a key role in the treatment of MM. The success of targeted therapy in MM has since 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 and primary amyloidosis, both in the preclinical settings and as part of clinical trials.

Marizomib, a proteasome inhibitor for all seasons: preclinical profile and a framework for clinical trials

The proteasome has emerged as an important clinically relevant target for the treatment of hematologic malignancies. Since the Food and Drug Administration approved the first-in-class proteasome inhibitor bortezomib (Velcade) for the treatment of relapsed/refractory multiple myeloma (MM) and mantle cell lymphoma, it has become clear that new inhibitors are needed that have a better therapeutic ratio, can overcome inherent and acquired bortezomib resistance and exhibit broader anti-cancer activities. Marizomib (NPI-0052; salinosporamide A) is a structurally and pharmacologically unique β-lactone-γ-lactam proteasome inhibitor that may fulfill these unmet needs. The potent and sustained inhibition of all three proteolytic activities of the proteasome by marizomib has inspired extensive preclinical evaluation in a variety of hematologic and solid tumor models, where it is efficacious as a single agent and in combination with biologics, chemotherapeutics and targeted therapeutic agents. Specifically, marizomib has been evaluated in models for multiple myeloma, mantle cell lymphoma, Waldenstrom's macroglobulinemia, chronic and acute lymphocytic leukemia, as well as glioma, colorectal and pancreatic cancer models, and has exhibited synergistic activities in tumor models in combination with bortezomib, the immunomodulatory agent lenalidomide (Revlimid), and various histone deacetylase inhibitors. These and other studies provided the framework for ongoing clinical trials in patients with MM, lymphomas, leukemias and solid tumors, including those who have failed bortezomib treatment, as well as in patients with diagnoses where other proteasome inhibitors have not demonstrated significant efficacy. This review captures the remarkable translational studies and contributions from many collaborators that have advanced marizomib from seabed to bench to bedside.