Bone Marrow Neovascularization, Plasma Cell Angiogenic Potential, and Matrix Metalloproteinase-2 Secretion Parallel Progression of Human Multiple Myeloma

Different evasion strategies in multiple myeloma

Multiple myeloma is the second most common malignant hematologic malignancy which evolved different strategies for immune escape from the host immune surveillance and drug resistance, including uncontrolled proliferation of malignant plasma cells in the bone marrow, genetic mutations, or deletion of tumor antigens to escape from special targets and so. Therefore, it is a big challenge to efficiently treat multiple myeloma patients. Despite recent applications of immunomodulatory drugs (IMiDS), protease inhibitors (PI), targeted monoclonal antibodies (mAb), and even hematopoietic stem cell transplantation (HSCT), it remains hardly curable. Summarizing the possible evasion strategies can help design specific drugs for multiple myeloma treatment. This review aims to provide an integrative overview of the intrinsic and extrinsic evasion mechanisms as well as recently discovered microbiota utilized by multiple myeloma for immune evasion and drug resistance, hopefully providing a theoretical basis for the rational design of specific immunotherapies or drug combinations to prevent the uncontrolled proliferation of MM, overcome drug resistance and improve patient survival.

The Leucine-Rich α2-Glycoprotein-1 Levels in Patients with Multiple Myeloma

INTRODUCTION

Angiogenesis is considered important in the pathogenesis of multiple myeloma (MM), as well as in the targeted treatment of the disease. Leucine-rich α2-glycoprotein 1 (LRG1) is a protein that participates in angiogenesis and its effect on solid organ tumors has been investigated recently. This study aimed to investigate the relationship between MM and LRG1.

METHODS

The MM patients who admitted to Hatay Mustafa Kemal University Hematology Clinic between September 2021 and October 2022 were included in the study. The study consists of a total of 4 groups: newly diagnosed MM (NDMM), relapsed refractory MM (RRMM), MM in remission (Rem-MM), and control group. Demographic data were retrieved from hospital records. Blood samples of our study groups were centrifuged at 1,500 × g for 10 min and serum was collected. LRG1, IL-6, IL-8, TGF-β1, HIF-1α, FGF-2, and VEGF levels were analyzed in all groups by ELISA method, and statistical analysis was performed.

RESULTS

A total of 112 individuals, including NDMM (n: 27), RRMM (n: 18), Rem-MM (n: 42), and control group (n: 25), were enrolled in the study. Based on the analyses, the NDMM group exhibited significantly elevated levels of LRG1 (p < 0.001), TGF-1 (p < 0.001), and HIF-1α (p = 0.046, p < 0.001, and p = 0.003 compared to the RRMM, Rem-MM, and control groups, respectively) compared to the other groups. LRG1 levels were positively correlated with creatinine (r: 0.363, p = 0.001), calcium (r: 0.344, p = 0.001), total protein (r: 0.473, p < 0.001), erythrocyte sedimentation rate (r: 0.547, p < 0.001), lactate dehydrogenase (r: 0.321, p = 0.003), beta-2-microglobulin (r: 0.312, p = 0.017), IL-6 (r: 0.478, p < 0.001), IL-8 (r: 0.240, p = 0.03), TGF-β1 (r: 0.521, p < 0.001), and HIF-1α (r: 0.321, p = 0.003) levels and were negatively correlated with hemoglobin (r: -0.512, p < 0.001) and albumin (r: -0.549, p < 0.001) levels. Receiver operating characteristics (ROC) analysis revealed the association of LRG1 with the highest AUC value of 0.959 (95% CI: 0.904-1, p < 0.001) and the optimal cut-off value of 534.95 ng/mL (sensitivity: 93% and specificity: 99%) in the NDMM group compared to the control group.

CONCLUSION

In this study, providing data for the first time on LRG1 levels in the setting of MM. LRG1 levels were found to be significantly higher in NDMM patients and in our study discriminate this patient population from RRMM, Rem-MM, and normal controls. Therefore, LRG1 seems to a potential biomarker that should be evaluated in future studies addressing the diagnosis, staging, follow-up, prognosis, and treatment target of MM.

Signaling Pathway Mediating Myeloma Cell Growth and Survival

Simple Summary

The bone marrow (BM) microenvironment plays a crucial role in pathogenesis of multiple myeloma (MM), and delineation of the intracellular signaling pathways activated in the BM microenvironment in MM cells is essential to develop novel therapeutic strategies to improve patient outcome.

Abstract

The multiple myeloma (MM) bone marrow (BM) microenvironment consists of different types of accessory cells. Both soluble factors (i.e., cytokines) secreted from these cells and adhesion of MM cells to these cells play crucial roles in activation of intracellular signaling pathways mediating MM cell growth, survival, migration, and drug resistance. Importantly, there is crosstalk between the signaling pathways, increasing the complexity of signal transduction networks in MM cells in the BM microenvironment, highlighting the requirement for combination treatment strategies to blocking multiple signaling pathways.

Anti-VEGF Drugs in the Treatment of Multiple Myeloma Patients

The interaction between the bone marrow microenvironment and plasma cells plays an essential role in multiple myeloma progression and drug resistance. The vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) pathway in vascular endothelial cells activates and promotes angiogenesis. Moreover, VEGF activates and promotes vasculogenesis and vasculogenic mimicry when it interacts with VEGF receptors expressed in precursor cells and inflammatory cells, respectively. In myeloma bone marrow, VEGF and VEGF receptor expression are upregulated and hyperactive in the stromal and tumor cells. It has been demonstrated that several antiangiogenic agents can effectively target VEGF-related pathways in the preclinical phase. However, they are not successful in treating multiple myeloma, probably due to the vicarious action of other cytokines and signaling pathways. Thus, the simultaneous blocking of multiple cytokine pathways, including the VEGF/VEGFR pathway, may represent a valid strategy to treat multiple myeloma. This review aims to summarize recent advances in understanding the role of the VEGF/VEGFR pathway in multiple myeloma, and mainly focuses on the transcription pathway and on strategies that target this pathway.

The chick embryo chorioallantoic membrane as an in vivo experimental model to study multiple myeloma

The chick embryo chorioallantoic membrane (CAM) has long been used as an in vivo assay for the study of tumor angiogenesis because when tumor grafts are placed at day 6-10 days of incubation the chick's immunocompetent system is not fully developed and the conditions for rejection have not been yet established. All studies for mammalian neoplasms, including multiple myeloma, have utilized tumor cell lines, tumor bioptic specimens, cell suspensions derived from tumors, mouse tumor xenografts bioptic specimens. CAM can also be used to study the effects of anti-angiogenic molecules on tumor cell suspensions of tumor bioptic specimens. This review article summarizes and discussed our experience concerning the use of the CAM to study multiple myeloma.

Variability of serum novel serum peptide biomarkers correlates with the disease states of multiple myeloma

Background

The bone marrow microenvironment provides an optimal substrate for multiple myeloma (MM) initiation and progression. The soluble component of MM niche is dynamic with the disease states of MM. We formerly employed proteomic profiling to construct a MM model. Four peptides constituting the model were selected by supervised neural network algorithm (SNN).

Methods

62 Newly diagnosed (ND) MM and 64 healthy controls (HCs) were picked up for validating the distinguishing capability of the SNN model. Nano-liquid chromatography-electrospray ionization-tandem mass spectrometry was used for peptide identification. MM in different disease states and HCs were choosed for peptides relative intensities comparison. Western blot and ELISA were employed to validate the variability.

Results

The sensitivity and specificity of the independent testing data set for blind validation were 93.55% and 92.19%. The relative intensities of three out of the four peptides were increased in ND and refractory and relapse patients but decreased to that level of HCs in complete remission and very good partial remission patients. Relative intensity of the remaining peptide was negatively associated with MM remission. The peptides sequencing results showed that they were derived from dihydropyrimidinase-like 2, fibrinogen alpha chain, platelet factor 4 and alpha-fetoprotein.

Conclusions

The potential value of the four peptides in monitoring MM treatment response was arised from their close correlation with MM disease states.

Mast Cells and Angiogenesis in Human Plasma Cell Malignancies

Bone marrow angiogenesis plays an important role in the pathogenesis and progression of hematological malignancies. It is well known that tumor microenvironment promotes tumor angiogenesis, proliferation, invasion, and metastasis, and also mediates mechanisms of therapeutic resistance. An increased number of mast cells has been demonstrated in angiogenesis associated with hematological tumors. In this review we focused on the role of mast cells in angiogenesis in human plasma cell malignancies. In this context, mast cells might act as a new target for the adjuvant treatment of these tumors through the selective inhibition of angiogenesis, tissue remodeling and tumor-promoting molecules, permitting the secretion of cytotoxic cytokines and preventing mast cell-mediated immune suppression.

STK405759 as a combination therapy with bortezomib or dexamethasone, in in vitro and in vivo multiple myeloma models

Multiple myeloma (MM) remains an incurable hematological malignancy. Combination regimens of conventional and novel drugs have improved patient’s survival. However, most patients inevitably relapse and become refractory to the current therapeutic armamentarium.

We investigated the efficacy of combining the microtubule-targeting agent STK405759 with dexamethasone or bortezomib in vitro and in vivo.

STK405759 combined with dexamethasone or bortezomib had synergistic cytotoxic activity in RPMIS, CAG and MM1.S human MM cell lines through activation of caspase 2, 3, 8, 9 and PARP. These treatments remained cytotoxic in the presence of bone marrow stroma cells. In other MM cells, including cells resistant to vincristine, melphalan, mitoxantrone or dexamethasone, these combinations decreased significantly survival as compared to single agents.

In in vivo studies, STK405759 disrupted existing blood vessels in xenograft tumors, acting not only as a cytotoxic agent but also as an anti-angiogenic drug. Mice treated with STK405759 in combination with dexamethasone or bortezomib resulted in greater tumor growth inhibition, increased overall response and prolonged survival as compared to as compared to BTZ or DEXA alone. Their anticancer activity was mediated by activation of apoptosis and reduction of tumor microvessel density.

These preclinical studies provide the rationale for future clinical trials of STK405759, dexamethasone and bortezomib combinations to improve the outcome of multiple myeloma patients.

Models for Studying Angiogenesis in Vivo

In vivo and in vitro techniques are available for reseach on the functions of endothelial cells during angiogenesis. In this review we describe and evaluate the methodology and specific features of some of the most frequently used in vivo assays.

Epha3 acts as proangiogenic factor in multiple myeloma

This study investigates the role of ephrin receptor A3 (EphA3) in the angiogenesis of Multiple Myeloma (MM) and the effects of a selective target of EphA3 by a specific monoclonal antibody on primary bone marrow endothelial cells (ECs) of MM patients.

EphA3 mRNA and protein were evaluated in ECs of MM patients (MMECs), in ECs of patients with monoclonal gammopathies of undetermined significance (MGECs) and in ECs of healthy subjects (control ECs). The effects of EphA3 targeting by mRNA silencing (siRNA) or by the anti EphA3 antibody on the angiogenesis were evaluated. We found that EphA3 is highly expressed in MMECs compared to the other EC types. Loss of function of EphA3 by siRNA significantly inhibited the ability of MMECs to adhere to fibronectin, to migrate and to form tube like structures in vitro, without affecting cell proliferation or viability. In addition, gene expression profiling showed that knockdown of EphA3 down modulated some molecules that regulate adhesion, migration and invasion processes. Interestingly, EphA3 targeting by an anti EphA3 antibody reduced all the MMEC angiogenesis-related functions in vitro. In conclusion, our findings suggest that EphA3 plays an important role in MM angiogenesis.

Targeting angiogenesis in multiple myeloma by the VEGF and HGF blocking DARPin® protein MP0250: a preclinical study

The investigational drug MP0250 is a multi-specific DARPin^® molecule that simultaneously binds and neutralizes VEGF and HGF with high specificity and affinity. Here we studied the antiangiogenic effects of the MP0250 in multiple myeloma (MM). In endothelial cells (EC) isolated from bone marrow (BM) of MM patients (MMEC) MP0250 reduces VEGFR2 and cMet phosphorylation and affects their downstream signaling cascades. MP0250 influences the secretory profile of MMEC and inhibits their in vitro angiogenic activities (spontaneous and chemotactic migration, adhesion, spreading and capillarogenesis). Compared to anti-VEGF or anti-HGF neutralizing mAbs, MP0250 strongly reduces capillary network formation and vessel-sprouting in a Matrigel angiogenesis assay. MP0250 potentiates the effect of bortezomib in the same in vitro setting. It significantly reduces the number of newly formed vessels in the choriollantoic membrane assay (CAM) and the Matrigel plug assay. In the syngeneic 5T33MM tumor model, MP0250 decreases the microvessel density (MVD) and the combination MP0250/bortezomib lowers the percentage of idiotype positive cells and the serum levels of M-protein. Overall results define MP0250 as a strong antiangiogenic agent with potential as a novel combination drug for treatment of MM patients.

Microenvironment drug resistance in multiple myeloma: emerging new players

Multiple myeloma (MM) drug resistance (DR) is a multistep transformation process based on a powerful interplay between bone marrow stromal cells and MM cells that allows the latter to escape anti-myeloma therapies. Here we present an overview of the role of the bone marrow microenvironment in both soluble factors-mediated drug resistance (SFM-DR) and cell adhesion-mediated drug resistance (CAM-DR), focusing on the role of new players, namely miRNAs, exosomes and cancer-associated fibroblasts.

Bone Marrow Stroma and Vascular Contributions to Myeloma Bone Homing

PURPOSE OF THE REVIEW

Herein we dissect mechanisms behind the dissemination of cancer cells from primary tumor site to the bone marrow, which are necessary for metastasis development, with a specific focus on multiple myeloma.

RECENT FINDINGS

The ability of tumor cells to invade vessels and reach the systemic circulation is a fundamental process for metastasis development; however, the interaction between clonal cells and the surrounding microenvironment is equally important for supporting colonization, survival, and growth in the secondary sites of dissemination. The intrinsic propensity of tumor cells to recognize a favorable milieu where to establish secondary growth is the basis of the "seed and soil" theory. This theory assumes that certain tumor cells (the "seeds") have a specific affinity for the milieu of certain organs (the "soil"). Recent literature has highlighted the important contributions of the vascular niche to the hospitable "soil" within the bone marrow. In this review, we discuss the crucial role of stromal cells and endothelial cells in supporting primary growth, homing, and metastasis to the bone marrow, in the context of multiple myeloma, a plasma cell malignancy with the unique propensity to primarily grow and metastasize to the bone marrow.

Bone marrow micro-environment is a crucial player for myelomagenesis and disease progression

Despite the advent of many therapeutic agents, such as bortezomib and lenalidomide that have significantly improved the overall survival, multiple myeloma remains an incurable disease. Failure to cure is multifactorial and can be attributed to the underlying genetic heterogeneity of the cancer and to the surrounding micro-environment. Understanding the mutual interaction between myeloma cells and micro-environment may lead to the development of novel treatment strategies able to eradicate this disease. In this review we discuss the principal molecules involved in the micro-environment network in multiple myeloma and the currently available therapies targeting them.

Endothelial progenitor cells in multiple myeloma neovascularization: a brick to the wall

Multiple myeloma (MM) is characterized by the clonal expansion of plasma cells in the bone marrow that leads to events such as bone destruction, anaemia and renal failure. Despite the several therapeutic options available, there is still no effective cure, and the standard survival is up to 4 years. The evolution from the asymptomatic stage of monoclonal gammopathy of undetermined significance to MM and the progression of the disease itself are related to cellular and molecular alterations in the bone marrow microenvironment, including the development of the vasculature. Post-natal vasculogenesis is characterized by the recruitment to the tumour vasculature of bone marrow progenitors, known as endothelial progenitor cells (EPCs), which incorporate newly forming blood vessels and differentiate into endothelial cells. Several processes related to EPCs, such as recruitment, mobilization, adhesion and differentiation, are tightly controlled by cells and molecules in the bone marrow microenvironment. In this review, the bone marrow microenvironment and the mechanisms associated to the development of the neovasculature promoted by EPCs are discussed in detail in both a non-pathological scenario and in MM. The latest developments in therapy targeting the vasculature and EPCs in MM are also highlighted. The identification and characterization of the pathways relevant to the complex setting of MM are of utter importance to identify not only biomarkers for an early diagnosis and disease progression monitoring, but also to reveal intervention targets for more effective therapy directed to cancer cells and the endothelial mediators relevant to neovasculature development.

A loss of host-derived MMP-7 promotes myeloma growth and osteolytic bone disease in vivo

Matrix metalloproteinases (MMPs) play a critical role in cancer pathogenesis, including tumor growth and osteolysis within the bone marrow microenvironment. However, the anti-tumor effects of MMPs are poorly understood, yet have significant implications for the therapeutic potential of targeting MMPs. Host derived MMP-7 has previously been shown to support the growth of bone metastatic breast and prostate cancer. In contrast and underscoring the complexity of MMP biology, here we identified a tumor-suppressive role for host MMP-7 in the progression of multiple myeloma in vivo. An increase in tumor burden and osteolytic bone disease was observed in myeloma-bearing MMP-7 deficient mice, as compared to wild-type controls. We observed that systemic MMP-7 activity was reduced in tumor-bearing mice and, in patients with multiple myeloma this reduced activity was concomitant with increased levels of the endogenous MMP inhibitor, tissue inhibitor of metalloproteinases-1 (TIMP-1). Our studies have identified an unexpected tumour-suppressive role for host-derived MMP-7 in myeloma bone disease in vivo, and highlight the importance of elucidating the effect of individual MMPs in a disease-specific context.

The Low Expression of IL-37 Involved in Multiple Myeloma - Associated Angiogenesis

BACKGROUND Angiogenesis plays a significant role in complex inflammatory and angiogenic processes and is also involved in multiple myeloma (MM) pathogenesis. IL-37 is a proinflammatory cytokine in antitumor activity. Our purpose was to evaluate the IL-37 clinical significance on MM. MATERIAL AND METHODS We measured serum levels of IL-37 in 45 patients with different stages of MM and 30 healthy control subjects and correlated IL-37 with numerous cytokines, such as angiogenesis factors including vascular endothelial growth factor (VEGF) and angiotensin-2 (Ang-2). We also measured the tube formation of human umbilical vein endothelial cells (HUVECs) after pretreatment with recombinant human IL-37 (rhIL-37). RESULTS Serum IL-37 level was lower in the patients with MM than in the healthy control subjects, whereas VEGF and Ang-2 levels were higher, depending on International Staging System stage. Serum IL-37 level had a negative correlation to VEGF and Ang-2 levels, and VEGF had a positive correlation to Ang-2 level. The tube formation of HUVECs was suppressed by the rhIL-37 pretreatment. CONCLUSIONS Our results indicate that serum level of IL-37 plays a part in the pathophysiology of MM progression. Therefore, IL-37 serum level may be a biomarker for disease stage and angiogenesis processes.

Development of Novel Immunotherapies for Multiple Myeloma

Multiple myeloma (MM) is a disorder of terminally differentiated plasma cells characterized by clonal expansion in the bone marrow (BM). It is the second-most common hematologic malignancy. Despite significant advances in therapeutic strategies, MM remains a predominantly incurable disease emphasizing the need for the development of new treatment regimens. Immunotherapy is a promising treatment modality to circumvent challenges in the management of MM. Many novel immunotherapy strategies, such as adoptive cell therapy and monoclonal antibodies, are currently under investigation in clinical trials, with some already demonstrating a positive impact on patient survival. In this review, we will summarize the current standards of care and discuss major new approaches in immunotherapy for MM.

Molecular and clinical significance of fibroblast growth factor 2 (FGF2 /bFGF) in malignancies of solid and hematological cancers for personalized therapies

Fibroblast growth factor (FGF) signaling is essential for normal and cancer biology. Mammalian FGF family members participate in multiple signaling pathways by binding to heparan sulfate and FGF receptors (FGFR) with varying affinities. FGF2 is the prototype member of the FGF family and interacts with its receptor to mediate receptor dimerization, phosphorylation, and activation of signaling pathways, such as Ras-MAPK and PI3K pathways. Excessive mitogenic signaling through the FGF/FGFR axis may induce carcinogenic effects by promoting cancer progression and increasing the angiogenic potential, which can lead to metastatic tumor phenotypes. Dysregulated FGF/FGFR signaling is associated with aggressive cancer phenotypes, enhanced chemotherapy resistance and poor clinical outcomes. In vitro experimental settings have indicated that extracellular FGF2 affects proliferation, drug sensitivity, and apoptosis of cancer cells. Therapeutically targeting FGF2 and FGFR has been extensively assessed in multiple preclinical studies and numerous drugs and treatment options have been tested in clinical trials. Diagnostic assays are used to quantify FGF2, FGFRs, and downstream signaling molecules to better select a target patient population for higher efficacy of cancer therapies. This review focuses on the prognostic significance of FGF2 in cancer with emphasis on therapeutic intervention strategies for solid and hematological malignancies.

Paeoniflorin inhibits proliferation and promotes apoptosis of multiple myeloma cells via its effects on microRNA‑29b and matrix metalloproteinase‑2

Multiple myeloma (MM) is a type of cancer characterized by the excessive proliferation of malignant plasma cells. In China, the incidence of MM has been increasing annually. Paeoniflorin exerts numerous functions, including coronary vessel expansion, and anti‑inflammation and anticancer activities. The present study aimed to investigate the effects of paeoniflorin on the proliferation and apoptosis of SKO‑007 MM cells, via its effects on the regulation of matrix metalloproteinase‑2 (MMP‑2) and microRNA (miR)‑29b. In the present study, an MTT assay was used to analyze the proliferation of SKO‑007 cells treated with paeoniflorin. Annexin V‑fluorescein isothiocyanate/propidium iodide apoptosis and caspase‑3 activation assays were used to detect the levels of cellular apoptosis. The expression levels of MMP‑2 and miR‑29b were detected using gelatin zymography and quantitative‑polymerase chain reaction, respectively. In addition, miR‑29b and anti‑miR‑29b plasmids were transfected into SKO‑007 cells, and the effects of paeoniflorin on cell proliferation and apoptosis were subsequently detected. The results of the present in vitro studies demonstrated that paeoniflorin was able to inhibit the proliferation of SKO‑007 cells in a dose‑ and time‑dependent manner. Furthermore, paeoniflorin effectively increased cell apoptosis, and augmented the activation of caspase‑3 and caspase‑9 in the SKO‑007 cells. The expression levels of MMP‑2 were suppressed following treatment of the SKO‑007 cells with paeoniflorin. In addition, paeoniflorin was able to induce the expression of miR‑29b. Notably, the results of the present study indicated that miR‑29b expression may control the expression of MMP‑2 in SKO‑007 cells. In conclusion, the present study demonstrated that paeoniflorin was able to inhibit cell proliferation and promote apoptosis of MM cells by suppressing the expression of MMP‑2, via the upregulation of miR‑29b.

The KISS1 Receptor as an In Vivo Microenvironment Imaging Biomarker of Multiple Myeloma Bone Disease

Multiple myeloma is one of the most common hematological diseases and is characterized by an aberrant proliferation of plasma cells within the bone marrow. As a result of crosstalk between cancer cells and the bone microenvironment, bone homeostasis is disrupted leading to osteolytic lesions and poor prognosis. Current diagnostic strategies for myeloma typically rely on detection of excess monoclonal immunoglobulins or light chains in the urine or serum. However, these strategies fail to localize the sites of malignancies. In this study we sought to identify novel biomarkers of myeloma bone disease which could target the malignant cells and/or the surrounding cells of the tumor microenvironment. From these studies, the KISS1 receptor (KISS1R), a G-protein-coupled receptor known to play a role in the regulation of endocrine functions, was identified as a target gene that was upregulated on mesenchymal stem cells (MSCs) and osteoprogenitor cells (OPCs) when co-cultured with myeloma cells. To determine the potential of this receptor as a biomarker, in vitro and in vivo studies were performed with the KISS1R ligand, kisspeptin, conjugated with a fluorescent dye. In vitro microscopy showed binding of fluorescently-labeled kisspeptin to both myeloma cells as well as MSCs under direct co-culture conditions. Next, conjugated kisspeptin was injected into immune-competent mice containing myeloma bone lesions. Tumor-burdened limbs showed increased peak fluorescence compared to contralateral controls. These data suggest the utility of the KISS1R as a novel biomarker for multiple myeloma, capable of targeting both tumor cells and host cells of the tumor microenvironment.

Immune responses in multiple myeloma: role of the natural immune surveillance and potential of immunotherapies

Multiple myeloma (MM) is a tumor of terminally differentiated B cells that arises in the bone marrow. Immune interactions appear as key determinants of MM progression. While myeloid cells foster myeloma-promoting inflammation, Natural Killer cells and T lymphocytes mediate protective anti-myeloma responses. The profound immune deregulation occurring in MM patients may be involved in the transition from a premalignant to a malignant stage of the disease. In the last decades, the advent of stem cell transplantation and new therapeutic agents including proteasome inhibitors and immunoregulatory drugs has dramatically improved patient outcomes, suggesting potentially key roles for innate and adaptive immunity in disease control. Nevertheless, MM remains largely incurable for the vast majority of patients. A better understanding of the complex interplay between myeloma cells and their immune environment should pave the way for designing better immunotherapies with the potential of very long term disease control. Here, we review the immunological microenvironment in myeloma. We discuss the role of naturally arising anti-myeloma immune responses and their potential corruption in MM patients. Finally, we detail the numerous promising immune-targeting strategies approved or in clinical trials for the treatment of MM.

Correlation of Mast Cell Density With Angiogenic Cytokines in Patients With Active Multiple Myeloma

PURPOSE

The aim of the study is to estimate whether bone marrow mast cell density (MCD) in multiple myeloma (MM) correlates with circulating levels of various angiogenic factors.

METHODS

In 70 patients with newly diagnosed active MM, we measured MCD using immunohistochemical stain for tryptase and serum levels of matrix metalloproteinase 9 (MMP-9), angiopoietin 2 (ANGIOP-2), and angiogenin (ANG) with ELISA.

FINDINGS

Levels of MCD, ANGIOP-2, and ANG were significantly higher in MM patients compared with the control group. The MMP-9 level was higher in MM patients compared with the control group but without statistical significance. All values were increasing in parallel with clinical stages. Furthermore, MCD correlated positively with MMP-9, ANGIOP-2, and ANG.

IMPLICATIONS

MCs participate in the angiogenic processes of MM, with complex implicated mechanisms. This interplay between MCs and the other participants favors angiogenesis and MM growth.

Thyroid hormone regulates adhesion, migration and matrix metalloproteinase 9 activity via αvβ3 integrin in myeloma cells

Thyroid hormone (3,5,3′-triiodothyronine, T3; L-thyroxine, T4) enhances cancer cell proliferation, invasion and angiogenesis via a discrete receptor located near the RGD recognition site on αvβ3 integrin. Tetraiodothyroacetic acid (tetrac) and its nanoparticulate formulation interfere with binding of T3/T4 to the integrin. This integrin is overexpressed in multiple myeloma (MM) and other cancers. MM cells interact with αvβ3 integrin to support growth and invasion. Matrix metalloproteinases (MMPs) are a family of enzymes active in tissue remodeling and cancer. The association between integrins and MMPs secretion and action is well established. In the current study, we examined the effects of thyroid hormone on myeloma cell adhesion, migration and MMP activity.

We show that T3 and T4 increased myeloma adhesion to fibronectin and induced αvβ3 clustering. In addition, the hormones induced MMP-9 expression and activation via αvβ3 and MAPK induction. Bortezomib, a standard myeloma treatment, caused a decrease in activity/quantity of MMPs and thyroid hormone opposed this effect. RGD peptide and tetrac impaired the production of MMP-9 in cell lines and in primary BM cells from myeloma patients.

In conclusion, thyroid hormone-dependent regulation via αvβ3 of myeloma cell adhesion and MMP-9 production may play a role in myeloma migration and progression.

Modifications of the mouse bone marrow microenvironment favor angiogenesis and correlate with disease progression from asymptomatic to symptomatic multiple myeloma

While multiple myeloma (MM) is almost invariably preceded by asymptomatic monoclonal gammopathy of undetermined significance (MGUS) and/or smoldering MM (SMM), the alterations of the bone marrow (BM) microenvironment that establish progression to symptomatic disease are circumstantial. Here we show that in Vk*MYC mice harboring oncogene-driven plasma cell proliferative disorder, disease appearance associated with substantial modifications of the BM microenvironment, including a progressive accumulation of both CD8⁺ and CD4⁺ T cells with a dominant T helper type 1 (Th1) response. Progression from asymptomatic to symptomatic MM was characterized by further BM accrual of T cells with reduced Th1 and persistently increased Th2 cytokine production, which associated with accumulation of CD206⁺Tie2⁺ macrophages, and increased pro-angiogenic cytokines and microvessel density (MVD). Notably, MVD was also increased at diagnosis in the BM of MGUS and SMM patients that subsequently progressed to MM when compared with MGUS and SMM that remained quiescent. These findings suggest a multistep pathogenic process in MM, in which the immune system may contribute to angiogenesis and disease progression. They also suggest initiating a large multicenter study to investigate MVD in asymptomatic patients as prognostic factor for the progression and outcome of this disease.

Study of prognostic significance of marrow angiogenesis assessment in patients with de novo acute leukemia

BACKGROUND

Angiogenesis is the highly ordered formation of new blood vessels from pre-existing vessels. It is seen throughout growth, in wound healing, menses, and is important in cancer, where pro- and antiangiogenic signals can be released by cancer cells, endothelial cells, stromal cells, blood, and the extracellular matrix. Aim of the study is to use standardized method for counting blood vessels to verify the significance and prognostic value of assessing marrow angiogenesis at diagnosis of de novo acute leukemia.

SUBJECTS AND METHODS

The study included 70 newly diagnosed acute leukemia cases and a control group composed of 35 bone marrow biopsy sections obtained from breast cancer patients. Examination of CD34 immunohistochemically stained sections for the assessment of marrow angiogenesis by quantification of its microvessel density (MVD).

RESULTS

MVD was significantly increased in acute leukemia patients in comparison to control group (P-value <0.001). Increased MVD was associated with unfavorable outcome.

CONCLUSION

The study demonstrated an evidence of increased angiogenesis in acute leukemia detected by high bone marrow MVD which may play a significant role in leukemic process. Understanding its role may help in designing new therapeutic strategies for acute leukemia.

Interleukin-10 Induces Both Plasma Cell Proliferation and Angiogenesis in Multiple Myeloma

In multiple myeloma the angiogenic process is enhanced by various mediators. Among them interleukin-10 (IL-10), secreted mainly by myeloma-associated macrophages seems to participate in myeloma progression with variable manners. The aim of the study was to measure serum levels of IL-10 in various stages of MM patients and to correlate them with various angiogenic cytokines, such as vascular endothelial growth factor and angiopoietin-2 and with known proliferation parameters, such as serum levels of B-cell activating factor and bone marrow infiltration by myeloma plasma cells, in order to explore their clinical significance. We measured serum levels of the above parameters by ELISA in 54 newly diagnosed MM patients. All of them were higher in MM patients and were increasing in parallel with disease progression. Furthermore, IL-10 correlated positively with both angiogenic cytokines and proliferation markers. This correlation of IL-10 with both angiogenic cytokines and markers of disease activity implicates that they all have an important role in MM pathogenesis and progression.

VEGF overexpression is a valuable prognostic factor for non-Hodgkin's lymphoma evidence from a systemic meta-analysis

Vascular endothelial growth factor (VEGF) plays a vital role in the progression of Non-Hodgkin's lymphoma (NHL). Although multiple studies have investigated the relationship between VEGF expression and prognosis of NHL, these studies have yielded conflicting results. Therefore, we performed a meta-analysis to evaluate the role of VEGF in the prognosis of NHL patients. We systematically searched eligible studies from databases and determined that there was a significant correlation between VEGF overexpression and overall survival (HR (hazard ratio) = 1.66, 95% CI: 1.25–2.22, P = 0.001). Based on subgroup analysis by study location, number of patients, the source of VEGF expression, and study design, we found that VEGF overexpression in surgically resected tissue (HR = 1.95, 95% CI: 1.41–2.69, P = 0.000), but not in serum (HR = 1.37, 95% CI: 0.96–1.95, P = 0.087), was associated with poorer prognosis. Additionally, VEGF overexpression did not correlate with performance status, LDH level, IPI score, tumor staging, B symptoms, or NHL relapse. In summary, overexpression of VEGF in lymphoma tissue represents a promising potential prognostic factor in NHL.

Microenvironment and multiple myeloma spread

In patients with multiple myeloma (MM), the bone marrow (BM) contains hematopoietic stem cells (HSCs) and non-hematopoietic cells. HSCs are able to give rise to all types of mature blood cells, while the non hematopoietic component includes mesenchymal stem cells (MSCs), fibroblasts, osteoblasts, osteoclasts, chondroclasts, endothelial cells, endothelial progenitor cells (EPCs), B and T lymphocytes, NK cells, erythrocytes, megakaryocytes, platelets, macrophages and mast cells. All of these cells form specialized "niches" in the BM microenvironment which are close to the vasculature ("vascular niche") or to the endosteum ("osteoblast niche"). The "vascular niche" is rich in blood vessels where endothelial cells and mural cells (pericytes and smooth muscle cells) create a microenvironment that affects the behavior of several stem and progenitor cells. The vessel wall serves as an independent niche for the recruitment of endothelial progenitor cells, MSCs and HSCs. The activation by angiogenic factors and inflammatory cytokines switch the "vascular niche" to promote MM tumor growth and spread. This review will focus on the mechanisms involved in the generation of signals released by endothelial cells in the "vascular niche" that promote tumor growth and spread in MM.

Content of endothelial progenitor cells in autologous stem cell grafts predict survival after transplantation for multiple myeloma

Multiple myeloma (MM) is considered an incurable B cell malignancy, although many patients can benefit from high-dose therapy with autologous stem cell transplantation (ASCT) as a first-line treatment. In non-Hodgkin lymphoma (NHL), ASCT is usually performed after relapse with curative intent. Disease progression is often associated with increased angiogenesis, in which endothelial progenitor cells (EPC) may have a central role. Here, we investigated the clinical impact of EPC levels in peripheral blood stem cell (PBSC) autografts for MM and NHL patients who received ASCT. EPC were identified by flow cytometry as aldehyde dehydrogenase(hi) CD34(+) vascular endothelial growth factor receptor 2(+) CD133(+) cells in both MM and NHL autografts. In MM, there was a positive correlation between EPC percentage and serum (s)-β2-microglobulin levels (r(2) = .371, P = .002). Unlike for NHL patients, MM patients with high numbers of infused EPC (EPC cells per kilogram) during ASCT had significant shorter progression-free survival (PFS) (P = .035), overall survival (P = .044) and time to next treatment (P = .009). In multivariate analysis, EPC cells per kilogram was a significant independent negative prognostic indicator of PFS (P = .03). In conclusion, the presence of high number of EPC in PBSC grafts is associated with adverse prognosis after ASCT in MM.

Vascular endothelial growth factor A (VEGFA) expression in mycosis fungoides

AIMS

High levels of vascular endothelial growth factor A (VEGFA) seem to herald a worse prognosis in mycosis fungoides (MF). In this study, we aimed to characterize more clearly VEGFA gene and protein expression in MF.

METHODS AND RESULTS

First, we compared VEGFA mRNA levels in MF and in normal T lymphocyte samples; significantly higher VEGFA levels were found in MF. We then studied VEGFA expression in different normal T cell subsets, focusing on CD4(+) , CD8(+) , resting and activated T lymphocytes. We applied the gene signatures of the normal T cell subsets to MF samples and found that activated T lymphocytes represented the closest normal counterpart of the tumour. However, VEGFA mRNA levels were significantly higher in MF than in activated normal T cells, suggesting that VEGFA overexpression in MF represents an attribute acquired during neoplastic transformation: no significant VEGFA expression differences were recorded between early and advanced stages. Gene expression profile results were supported by immunohistochemistry in routine sections from 27 MF cases.

CONCLUSIONS

For the first time, we demonstrate VEGFA expression in MF cells, suggesting that the VEGF pathway may be implicated in MF pathogenesis and can represent a novel therapeutic target.

Relevance of the thyroid hormones-αvβ3 pathway in primary myeloma bone marrow cells and to bortezomib action

Thyroid hormones (T3 and T4) induce proliferation in multiple myeloma (MM) cell lines via the αvβ3 integrin-mitogen-activated protein kinase (MAPK) pathway. We further show in primary MM bone marrow (BM) samples (n = 9) induction of cell viability by 1 nM T3 (13%, p < 0.002) and more potently by 100 nM T4 (21-45%, p < 0.0002) and a quick (1 h) and long-lasting (24 h) pERK activation, which was inhibited in the presence of β3 but not β1 blocking antibodies. Involvement of the integrin was further shown by two disintegrins, Arg-Gly-Asp (RGD) and echistatin peptides, which occluded the effects of T3/T4 on viability, proliferating cell nuclear antigen (PCNA) (proliferation marker) and apoptotic gene expression. Lastly, T3/T4 significantly opposed bortezomib (25 nM) cytotoxicy, as confirmed by several methods. In summary, our results imply that endogenous thyroid hormones in myeloma are factors that may support cell growth, with relevance to bortezomib action.

The chick embryo chorioallantoic membrane as a model for tumor biology

Among the in vivo models, the chick embryo chorioallantoic membrane (CAM) has been used to implant several tumor types as well as malignant cell lines to study their growth rate, angiogenic potential and metastatic capability. This review article is focused on the major compelling literature data on the use of the CAM to investigate tumor growth and the metastatic process.

The evaluation of angiogenesis and matrix metalloproteinase-2 secretion in bone marrow of multiple myeloma patients before and after the treatment

PURPOSE

Angiogenesis appears to be a prominent feature of many hematological disorders, particularly in multiple myeloma (MM). Progression in MM also involves secretion of the metaloproteinases (MMPs). In this study, the expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and its receptor, in bone marrow trephine biopsy (TB) of thirty six MM patients before and after the treatment or during progression was examined. The MMP-2 secretion was assessed from the same patients.

MATERIAL/METHODS

Immunohistochemical staining of bone marrow specimens for angiogenic factors and microvessel density (MVD) and bone marrow aspirates for Western blot analysis of MMP-2 expression was performed.

RESULTS

In active, untreated MM patients, we found statistically significant differences in the expression of angiogenic factors according to the patients after the anti-angiogenic treatment. We found statistical differences of the expression of angiogenic factors between the group of patients with a response after the treatment and the patients who had progression during the treatment. The data showed statistically significant decreased MVD after the treatment. The results showed statistically significant differences between initial secretion of MMP-2 in active, untreated MM patients and patients with a response after the treatment and patients with progression during the treatment.

CONCLUSIONS

We showed that not only decreased expression of angiogenic cytokines is present after the anti-angiogenic treatment but also activity of MMP-2 in MM patients who responded to the treatment. Combination therapy with the inhibition of the activity of MMPs could represent an interesting therapeutical approach in MM.

Thalidomide: present and future in multiple myeloma

Multiple myeloma continues to be an incurable disease. The understanding of the disease's pathophysiology has significantly improved over the past few years, partly due to the discovery of the role of immunomodulatory agents and the study of their mechanism of action. Thalidomide, the first of the immunomodulatory family to be used in the management of multiple myeloma, proved not only to be effective in the treatment of multiple myeloma, but also instigated a wide range of in vitro and in vivo studies to define the pathophysiology of the plasma cell dyscrasia. The attention thalidomide has received in the past and recent history has not been without a price. The drug has a side-effect profile that, if managed appropriately, provides the most unique active molecule in the management of the disease, where it maintains the same response rate in newly diagnosed patients as in advanced relapsed/refractory multiple myeloma patients.

The role of inflammatory cells in angiogenesis in multiple myeloma

Both innate and adaptive immune cells are involved in the mechanisms of endothelial cell proliferation, migration and activation, via production and release of a large spectrum of pro-angiogenic mediators, thus creating the specific microenvironment that favors increased rate of tissue vascularization. In this article, we focus on the immune cell component of the angiogenic process occurring during multiple myeloma progression. We also provide information on some anti-angiogenic properties of immune cells that may be applied for a potential pharmacological use as anti-angiogenic agents in the disease treatment.

Prognostic significance of absolute lymphocyte count/absolute monocyte count ratio at diagnosis in patients with multiple myeloma

Background

Absolute lymphocyte count (ALC) in peripheral blood has recently been reported to be an independent prognostic factor in multiple myeloma (MM). Previous studies indicated that the absolute monocyte count (AMC) in peripheral blood reflects the state of the tumor microenvironment in lymphomas. Neither the utility of the AMC nor its relationship with ALC has been studied in MM.

Methods

The prognostic value of ALC, AMC, and the ALC/AMC ratio at the time of diagnosis was retrospectively examined in 189 patients with MM.

Results

On univariate analysis, low ALC (<1,400 cells/µL), high AMC (≥490 cells/µL), and low ALC/AMC ratio (<2.9) were correlated with worse overall survival (OS) (p=.002, p=.038, and p=.001, respectively). On multivariate analysis, the ALC/AMC ratio was an independent prognostic factor (p=.047), whereas ALC and AMC were no longer statistical significant. Low ALC, high AMC, and low ALC/AMC ratio were associated with poor prognostic factors such as high International Staging System stage, plasmablastic morphology, hypoalbuminemia, and high β2-microglobulin.

Conclusions

Univariate analysis demonstrated that changes in ALC, AMC, and the ALC/AMC ratio are associated with patient survival in MM. Multivariate analysis showed that, of these factors, the ALC/AMC ratio was an independent prognostic factor for OS.

Macrophages in multiple myeloma

Tumor associated macrophages (TAMs) are a rich source of pro-angiogenic cytokines and growth factors, and a relationship between the TAMs content, the rate of tumor growth and the extent of vascularization has been shown in several tumors. In this article, we have summarized the literature and our data concerning the involvement of TAMs in angiogenesis occurring in multiple myeloma. Finally, therapeutic aspects concerning the potential role of molecules which inhibit macrophage recruitment in the tumor side are also discussed.

Azaindole derivatives are inhibitors of microtubule dynamics, with anti-cancer and anti-angiogenic activities

BACKGROUND AND PURPOSE

Drugs targeting microtubules are commonly used for cancer treatment. However, the potency of microtubule inhibitors used clinically is limited by the emergence of resistance. We thus designed a strategy to find new cell-permeable microtubule-targeting agents.

EXPERIMENTAL APPROACH

Using a cell-based assay designed to probe for microtubule polymerization status, we screened a chemical library and identified two azaindole derivatives, CM01 and CM02, as cell-permeable microtubule-depolymerizing agents. The mechanism of the anti-tumour effects of these two compounds was further investigated both in vivo and in vitro.

KEY RESULTS

CM01 and CM02 induced G2/M cell cycle arrest and exerted potent cytostatic effects on several cancer cell lines including multidrug-resistant (MDR) cell lines. In vitro experiments revealed that the azaindole derivatives inhibited tubulin polymerization and competed with colchicines for this effect, strongly indicating that tubulin is the cellular target of these azaindole derivatives. In vivo experiments, using a chicken chorioallantoic xenograft tumour assay, established that these compounds exert a potent anti-tumour effect. Furthermore, an assay probing the growth of vessels out of endothelial cell spheroids showed that CM01 and CM02 exert anti-angiogenic activities.

CONCLUSIONS AND IMPLICATIONS

CM01 and CM02 are reversible microtubule-depolymerizing agents that exert potent cytostatic effects on human cancer cells of diverse origins, including MDR cells. They were also shown to inhibit angiogenesis and tumour growth in chorioallantoic breast cancer xenografts. Hence, these azaindole derivatives are attractive candidates for further preclinical investigations.

Cell-surface serglycin promotes adhesion of myeloma cells to collagen type I and affects the expression of matrix metalloproteinases

Serglycin (SG) is mainly expressed by hematopoetic cells as an intracellular proteoglycan. Multiple myeloma cells constitutively secrete SG, which is also localized on the cell surface in some cell lines. In this study, SG isolated from myeloma cells was found to interact with collagen type I (Col I), which is a major bone matrix component. Notably, myeloma cells positive for cell-surface SG (csSG) adhered significantly to Col I, compared to cells lacking csSG. Removal of csSG by treatment of the cells with chondroitinase ABC or blocking of csSG by an SG-specific polyclonal antibody significantly reduced the adhesion of myeloma cells to Col I. Significant up-regulation of expression of the matrix metalloproteinases MMP-2 and MMP-9 at both the mRNA and protein levels was observed when culturing csSG-positive myeloma cells on Col I-coated dishes or in the presence of soluble Col I. MMP-9 and MMP-2 were also expressed in increased amounts by myeloma cells in the bone marrow of patients with multiple myeloma. Our data indicate that csSG of myeloma cells affects key functional properties, such as adhesion to Col I and the expression of MMPs, and imply that csSG may serve as a potential prognostic factor and/or target for pharmacological interventions in multiple myeloma.