Vascular endothelial growth factor triggers signaling cascades mediating multiple myeloma cell growth and migration

The implication of serum HLA-G in angiogenesis of multiple myeloma

BACKGROUND

Despite the advances of therapies, multiple myeloma (MM) remains an incurable hematological cancer that most patients experience relapse. Tumor angiogenesis is strongly correlated with cancer relapse. Human leukocyte antigen G (HLA-G) has been known as a molecule to suppress angiogenesis. We aimed to investigate whether soluble HLA-G (sHLA-G) was involved in the relapse of MM.

METHODS

We first investigated the dynamics of serum sHLA-G, vascular endothelial growth factor (VEGF) and interleukin 6 (IL-6) in 57 successfully treated MM patients undergoing remission and relapse. The interactions among these angiogenesis-related targets (sHLA-G, VEGF and IL-6) were examined in vitro. Their expression at different oxygen concentrations was investigated using a xenograft animal model by intra-bone marrow and skin grafts with myeloma cells.

RESULTS

We found that HLA-G protein degradation augmented angiogenesis. Soluble HLA-G directly inhibited vasculature formation in vitro. Mechanistically, HLA-G expression was regulated by hypoxia-inducible factor-1α (HIF-1α) in MM cells under hypoxia. We thus developed two mouse models of myeloma xenografts in intra-bone marrow (BM) and underneath the skin, and found a strong correlation between HLA-G and HIF-1α expressions in hypoxic BM, but not in oxygenated tissues. Yet when stimulated with IL-6, both HLA-G and HIF-1α could be targeted to ubiquitin-mediated degradation via PARKIN.

CONCLUSION

These results highlight the importance of sHLA-G in angiogenesis at different phases of multiple myeloma. The experimental evidence that sHLA-G as an angiogenesis suppressor in MM may be useful for future development of novel therapies to prevent relapse.

Recent advances and future directions on small molecule VEGFR inhibitors in oncological conditions

"A journey of mixed emotions" is a quote that best describes the progress chart of vascular endothelial growth factor receptor (VEGFR) inhibitors as cancer therapeutics in the last decade. Exhilarated with the Food and Drug Administration (FDA) approvals of numerous VEGFR inhibitors coupled with the annoyance of encountering the complications associated with their use, drug discovery enthusiasts are on their toes with an unswerving determination to enhance the rate of translation of VEGFR inhibitors from preclinical to clinical stage. The recently crafted armory of VEGFR inhibitors is a testament to their growing dominance over other antiangiogenic therapies for cancer treatment. This review perspicuously underscores the earnest attempts of the researchers to extract the antiproliferative potential of VEGFR inhibitors through the design of mechanistically diverse structural assemblages. Moreover, this review encompasses sections on structural/molecular properties and physiological functions of VEGFR, FDA-approved VEGFR inhibitors, and hurdles restricting the activity range/clinical applicability of VEGFR targeting antitumor agents. In addition, tactics to overcome the limitations of VEGFR inhibitors are discussed. A clear-cut viewpoint transmitted through this compilation can provide practical directions to push the cart of VEGFR inhibitors to advanced-stage clinical investigations in diverse malignancies.

MALAT1 regulates network of microRNA-15a/16-VEGFA to promote tumorigenesis and angiogenesis in multiple myeloma

MALAT1 is one of the most hopeful members implicated in angiogenesis in a variety of non-malignant diseases. In multiple myeloma (MM), MALAT1 is recognized as the most highly expressed long non-coding RNA. However, the functional roles of MALAT1 in angiogenesis and the responsible mechanisms have not yet been explored. Herein, we discovered a novel regulatory network dependent on MALAT1 in relation to MM tumorigenesis and angiogenesis. We observed that MALAT1 was upregulated in MM and significantly associated with poor overall survival. MALAT1 knockdown suppressed MM cell proliferation and promoted apoptosis, while restricting endothelial cells angiogenesis. Moreover, MALAT1 directly targeted microRNA-15a/16, and microRNA-15a/16 suppression partly reverted the effects of MALAT1 deletion on MM cells in vitro as well as tumor growth and angiogenesis in vivo. In addition, further study indicated that MALAT1 functioned as a competing endogenous RNA for microRNA-15a/16 to regulate vascular endothelial growth factor A (VEGFA) expression. Our results suggest that MALAT1 plays an important role in the regulatory axis of microRNA-15a/16-VEGFA to promote tumorigenicity and angiogenesis in MM. Consequently, MALAT1 could serve as a novel promising biomarker and a potential antiangiogenic target against MM.

The Clinical Relevance of Selected Cytokines in Newly Diagnosed Multiple Myeloma Patients

Multiple myeloma (MM) is the second most common hematological neoplasm. Cytokines, chemokines, and their receptors, induced by the microenvironment of MM, participate in tumor growth, the attraction of leukocytes, cell homing, and bone destruction. This study aimed to assess the correlation between the pretreatment serum concentrations of interleukin-6 (IL-6), interleukin-8 (IL-8), angiogenic chemokine monocyte chemoattractant protein-1 (MCP-1), and vascular endothelial growth factor (VEGF) and the clinical outcomes and survival of patients newly diagnosed with MM. The study group consisted of 82 individuals. The IL-8 concentration was significantly positively correlated with the age of onset (p = 0.007), the International Staging System (ISS) stage (p = 0.03), the Eastern Cooperative Oncology Group (ECOG) performance status (p < 0.001), the degree of anemia before treatment (p < 0.0001), the degree of kidney disease (p < 0.001), and VEGF (p = 0.0364). Chemotherapy responders had significantly lower concentrations of IL-8 (p < 0.001), IL-6 (p < 0.001), and VEGF (p = 0.04) compared with non-responders. Patients with treatment-induced polyneuropathy had significantly higher levels of IL-8 (p = 0.033). Patients with a high level of IL-6 had a 2-fold higher risk of progression-free survival (PFS) reduction (17 vs. 35 months; HR = 1.89; p = 0.0078), and a more than 2.5-fold higher risk of overall survival (OS) reduction (28 vs. 78 months; HR = 2.62; p < 0.001). High levels of IL-6, IL-8, and VEGF demonstrated significant predictive values for some clinical conditions or outcomes of newly diagnosed MM patients. Patients with an early response to chemotherapy had a significantly lower concentration of these cytokines. A high pretreatment IL-6 concentration was an independent negative prognostic marker for newly diagnosed MM patients.

Computational modeling of multiple myeloma interactions with resident bone marrow cells

The interaction of multiple myeloma with bone marrow resident cells plays a key role in tumor progression and the development of drug resistance. The tumor cell response involves contact-mediated and paracrine interactions. The heterogeneity of myeloma cells and bone marrow cells makes it difficult to reproduce this environment in in-vitro experiments. The use of in-silico established tools can help to understand these complex problems. In this article, we present a computational model based on the finite element method to define the interactions of multiple myeloma cells with resident bone marrow cells. This model includes cell migration, which is controlled by stress-strain equilibrium, and cell processes such as proliferation, differentiation, and apoptosis. A series of computational experiments were performed to validate the proposed model. Cell proliferation by the growth factor IGF-1 is studied for different concentrations ranging from 0-10 ng/mL. Cell motility is studied for different concentrations of VEGF and fibronectin in the range of 0-100 ng/mL. Finally, cells were simulated under a combination of IGF-1 and VEGF stimuli whose concentrations are considered to be dependent on the cancer-associated fibroblasts in the extracellular matrix. Results show a good agreement with previous in-vitro results. Multiple myeloma growth and migration are shown to correlate linearly to the IGF-1 stimuli. These stimuli are coupled with the mechanical environment, which also improves cell growth. Moreover, cell migration depends on the fiber and VEGF concentration in the extracellular matrix. Finally, our computational model shows myeloma cells trigger mesenchymal stem cells to differentiate into cancer-associated fibroblasts, in a dose-dependent manner.

Monoclonal Gammopathies and the Bone Marrow Microenvironment: From Bench to Bedside and Then Back Again

Multiple myeloma (MM) is an incurable hematologic malignancy characterized by a multistep evolutionary pathway, with an initial phase called monoclonal gammopathy of undetermined significance (MGUS), potentially evolving into the symptomatic disease, often preceded by an intermediate phase called "smoldering" MM (sMM). From a biological point of view, genomic alterations (translocations/deletions/mutations) are already present at the MGUS phase, thus rendering their role in disease evolution questionable. On the other hand, we currently know that changes in the bone marrow microenvironment (TME) could play a key role in MM evolution through a progressive shift towards a pro-inflammatory and immunosuppressive shape, which may drive cancer progression as well as clonal plasma cells migration, proliferation, survival, and drug resistance. Along this line, the major advancement in MM patients' survival has been achieved by the introduction of microenvironment-oriented drugs (including immunomodulatory drugs and monoclonal antibodies). In this review, we summarized the role of the different components of the TME in MM evolution from MGUS as well as potential novel therapeutic targets/opportunities.

Bone marrow microenvironment- induced regulation of Bcl-2 family members in multiple myeloma (MM): Therapeutic implications

In Multiple Myeloma (MM) the finely tuned homeostasis of the bone marrow (BM) microenvironment is disrupted. Evasion of programmed cell death (apoptosis) represents a hallmark of cancer. Besides genetic aberrations, the supportive and protective MM BM milieu, which is constituted by cytokines and growth factors, intercellular and cell: extracellular matrix (ECM) interactions and exosomes, in particular, plays a key role in the abundance of pro-survival members of the Bcl-2 family (i.e., Mcl-1, Bcl-2, and Bcl-xL) in tumor cells. Moreover, microenvironmental cues have also an impact on stability- regulating post-translational modifications of anti-apoptotic proteins including de/phosphorylation, polyubiquitination; on their intracellular binding affinities, and localization. Advances of our molecular knowledge on the escape of cancer cells from apoptosis have informed the development of a new class of small molecules that mimic the action of BH3-only proteins. Indeed, approaches to directly target anti-apoptotic Bcl-2 family members are among today's most promising therapeutic strategies and BH3-mimetics (i.e., venetoclax) are currently revolutionizing not only the treatment of CLL and AML, but also hold great therapeutic promise in MM. Furthermore, approaches that activate apoptotic pathways indirectly via modification of the tumor microenvironment have already entered clinical practice. The present review article will summarize our up-to-date knowledge on molecular mechanisms by which the MM BM microenvironment, cytokines, and growth factors in particular, mediates tumor cell evasion from apoptosis. Moreover, it will discuss some of the most promising science- derived therapeutic strategies to overcome Bcl-2- mediated tumor cell survival in order to further improve MM patient outcome.

Biomolecules-releasing click chemistry-based bioadhesives for repairing acetabular labrum tears

Currently, there are no effective clinical or experimental treatments to fully restore the function of the torn acetabular labrum. To fill the gap, here, we report the finding of progenitor cells in labral tissue, which can be recruited and stimulated to repair torn acetabular labral tissue. This study aimed to develop a biomolecule releasing bioadhesive which can speed up labral tissue healing by eliciting autologous labral progenitor cellular responses. A click chemistry-based bioadhesive, capable of releasing biomolecules, was synthesized to exert ~3× adhesion strength compared with fibrin glue. Via the release of platelet-derived growth factor (PDGF), the adhesive was shown to actively recruit and stimulate the proliferation of labral progenitor cells to the tear sites and within the adhesive. Finally, the ability of this biomolecules-releasing adhesive designed to promote labral tissue regeneration was evaluated using discarded human acetabular labrum tissue compared with surgical suture ex vivo. Histological analysis shows that PDGF-releasing bioadhesive yielded significantly more labrum cell responses and extracellular matrix protein (proteoglycan and collagen) production at the tear tissue site than surgical suture controls. The results confirm that the new PDGF-releasing bioadhesive can activate the responses of autologous labral progenitor cells to significantly improve labral tissue regeneration. Clinical significance: These PDGF-releasing bioadhesives may serve as a new and effective tool for repairing and regenerating acetabular labrum tears.

Pathways of Angiogenic and Inflammatory Cytokines in Multiple Myeloma: Role in Plasma Cell Clonal Expansion and Drug Resistance

Multiple myeloma (MM) is the second most common hematological malignancy, and despite the introduction of innovative therapies, remains an incurable disease. Identifying early and minimally or non-invasive biomarkers for predicting clinical outcomes and therapeutic responses is an active field of investigation. Malignant plasma cells (PCs) reside in the bone marrow (BM) microenvironment (BMME) which comprises cells (e.g., tumour, immune, stromal cells), components of the extracellular matrix (ECM) and vesicular and non-vesicular (soluble) molecules, all factors that support PCs’ survival and proliferation. The interaction between PCs and BM stromal cells (BMSCs), a hallmark of MM progression, is based not only on intercellular interactions but also on autocrine and paracrine circuits mediated by soluble or vesicular components. In fact, PCs and BMSCs secrete various cytokines, including angiogenic cytokines, essential for the formation of specialized niches called “osteoblastic and vascular niches”, thus supporting neovascularization and bone disease, vital processes that modulate the pathophysiological PCs–BMME interactions, and ultimately promoting disease progression. Here, we aim to discuss the roles of cytokines and growth factors in pathogenetic pathways in MM and as prognostic and predictive biomarkers. We also discuss the potential of targeted drugs that simultaneously block PCs’ proliferation and survival, PCs–BMSCs interactions and BMSCs activity, which may represent the future goal of MM therapy.

Bone metabolism parameters and their relation to cytogenetics in multiple myeloma

OBJECTIVES

Our aim was to correlate serum levels of selected markers of bone metabolism and bone marrow microenvironment to cytogenetic changes in patients with multiple myeloma (MM).

METHODS

We assed cytogenetic changes in 308 patients and correlated them with the following levels of bone marrow metabolism: thymidine kinase (TK), β2-microglobulin (b-2-m), Dickkopf-1 protein (DKK-1), C-terminal telopeptide collagen-I (ICTP), N-terminal propeptide of type I procollagen (PINP), receptor for interleukin 6 (rIL-6), vascular cell adhesive molecule-1 (VCAM), soluble intercellular adhesion molecule-1, osteoprotegerin (OPG), hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), syndecan-1 (SYN-1) and Fas antigen.

RESULT

Individuals with delRB1 had lower levels of OPG (M = 7.39 vs. 5.46 pmol/L, p = .025) and VEGF (M = 304 vs. 196 pg/ml; p = .036). t(14;16) was associated with higher β2m levels (M = 7.59 vs. 4.13 mg/L; p = .022) and lower DKK-1 levels (M = 4465 ng/L vs. 12,593). The presence of 1q21 gain was associated with higher levels of TK (M = 100.0 vs. 11.0 IU/L, p = .026) and lower levels of PINP (M = 49.3 vs. 67.4 mg/L, p = .030).

CONCLUSIONS

Our analysis has shown, some cytogenetic changes, especially delRB1, t(14;16) and 1q21gain, which affect the components of the cytokine network in multiple myeloma.

Multiple Myeloma Cell-Derived Exosomes: Implications on Tumorigenesis, Diagnosis, Prognosis and Therapeutic Strategies

Multiple myeloma (MM) is a hematological disease that is still not curable. The bone marrow milieu, with cellular and non-cellular elements, participate in the creation of a pro-tumoral environment enhancing growth and survival of MM plasma cells. Exosomes are vesicles oscillating in dimension between 50 nm and 100 nm in size that can be released by various cells and contribute to the pathogenesis and progression of MM. Exosomes enclose proteins, cytokines, lipids, microRNAs, long noncoding RNAs, and circular RNAs able to regulate interactions between MM plasma cells and adjacent cells. Through exosomes, mesenchymal stem cells confer chemoresistance to MM cells, while myeloma cells promote angiogenesis, influence immune response, cause bone lesions, and have an impact on the outcome of MM patients. In this review, we analyze the role played by exosomes in the progression of monoclonal gammopathies and the effects on the proliferation of neoplastic plasma cells, and discuss the possible employment of exosomes as potential targets for the treatment of MM patients.

Pathophysiological role of calcium channels and transporters in the multiple myeloma

Multiple myeloma (MM) is a common malignant tumor of plasma cells. Despite several treatment approaches in the past two decades, MM remains an aggressive and incurable disease in dire need of new treatment strategies. Approximately 70–80% of patients with MM have myeloma bone disease (MBD), often accompanied by pathological fractures and hypercalcemia, which seriously affect the prognosis of the patients. Calcium channels and transporters can mediate Ca²⁺ balance inside and outside of the membrane, indicating that they may be closely related to the prognosis of MM. Therefore, this review focuses on the roles of some critical calcium channels and transporters in MM prognosis, which located in the plasma membrane, endoplasmic reticulum and mitochondria. The goal of this review is to facilitate the identification of new targets for the treatment and prognosis of MM.

Advances in viral oncolytics for treatment of multiple myeloma - a focused review

INTRODUCTION

Oncolytic viruses are genetically engineered viruses that target myeloma-affected cells by detecting specific cell surface receptors (CD46, CD138), causing cell death by activating the signaling pathway to induce apoptosis or by immune-mediated cellular destruction.

AREAS COVERED

This article summarizes oncolytic virotherapy advancements such as the therapeutic use of viruses by targeting cell surface proteins of myeloma cells as well as the carriers to deliver viruses to the target tissues safely. The major classes of viruses that have been studied for this include measles, myxoma, adenovirus, reovirus, vaccinia, vesicular-stomatitis virus, coxsackie, and others. The measles virus acts as oncolytic viral therapy by binding to the CD46 receptors on the myeloma cells to utilize its surface H protein. These H-protein and CD46 interactions lead to cellular syncytia formation resulting in cellular apoptosis. Vesicular-stomatitis virus acts by downregulation of anti-apoptotic factors (Mcl-2, BCL-2). Based upon the published literature searches till December 2020, we have summarized the data supporting the advances in viral oncolytic for the treatment of MM.

EXPERT OPINION

Oncolytic virotherapy is an experimental approach in multiple myeloma (MM); many issues need to be addressed for safe viral delivery to the target tissue.

Therapy Resistance in Cancers: Phenotypic, Metabolic, Epigenetic and Tumour Microenvironmental Perspectives

BACKGROUND

Chemoresistance is a vital problem in cancer therapy where cancer cells develop mechanisms to encounter the effect of chemotherapeutics, resulting in cancer recurrence. In addition, chemotherapy- resistant leads to the formation of a more aggressive form of cancer cells, which, in turn, contributes to the poor survival of patients with cancer.

OBJECTIVE

In this review, we aimed to provide an overview of how the therapy resistance property evolves in cancer cells, contributing factors and their role in cancer chemoresistance, and exemplified the problems of some available therapies.

METHODS

The published literature on various electronic databases including, Pubmed, Scopus, Google scholar containing keywords cancer therapy resistance, phenotypic, metabolic and epigenetic factors, were vigorously searched, retrieved and analyzed.

RESULTS

Cancer cells have developed a range of cellular processes, including uncontrolled activation of Epithelial- Mesenchymal Transition (EMT), metabolic reprogramming and epigenetic alterations. These cellular processes play significant roles in the generation of therapy resistance. Furthermore, the microenvironment where cancer cells evolve effectively contributes to the process of chemoresistance. In tumour microenvironment immune cells, Mesenchymal Stem Cells (MSCs), endothelial cells and cancer-associated fibroblasts (CAFs) contribute to the maintenance of therapy-resistant phenotype via the secretion of factors that promote resistance to chemotherapy.

CONCLUSION

To conclude, as these factors hinder successful cancer therapies, therapeutic resistance property of cancer cells is a subject of intense research, which in turn could open a new horizon to aim for developing efficient therapies.

TAK1 is a pivotal therapeutic target for tumor progression and bone destruction in myeloma

Along with tumor progression, the bone marrow microenvironment is skewed in multiple myeloma (MM), which underlies the unique pathophysiology of MM and confers aggressiveness and drug resistance in MM cells. TGF-b-activated kinase-1 (TAK1) mediates a wide range of intracellular signaling pathways. We demonstrate here that TAK1 is constitutively overexpressed and phosphorylated in MM cells, and that TAK1 inhibition suppresses the activation of NF-κB, p38MAPK, ERK and STAT3 in order to decrease the expression of critical mediators for MM growth and survival, including PIM2, MYC, Mcl- 1, IRF4, and Sp1, along with a substantial reduction in the angiogenic factor VEGF in MM cells. Intriguingly, TAK1 phosphorylation was also induced along with upregulation of vascular cell adhesion molecule-1 (VCAM-1) in bone marrow stromal cells (BMSC) in cocultures with MM cells, which facilitated MM cell-BMSC adhesion while inducing IL-6 production and receptor activator of nuclear factor κ-B ligand (RANKL) expression by BMSC. TAK1 inhibition effectively impaired MM cell adhesion to BMSC to disrupt the support of MM cell growth and survival by BMSC. Furthermore, TAK1 inhibition suppressed osteoclastogenesis enhanced by RANKL in cocultures of bone marrow cells with MM cells, and restored osteoblastic differentiation suppressed by MM cells or inhibitory factors for osteoblastogenesis overproduced in MM. Finally, treatment with the TAK1 inhibitor LLZ1640-2 markedly suppressed MM tumor growth and prevented bone destruction and loss in mouse MM models. Therefore, TAK1 inhibition may be a promising therapeutic option targeting not only MM cells but also the skewed bone marrow microenvironment in 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.

Old Player-New Tricks: Non Angiogenic Effects of the VEGF/VEGFR Pathway in Cancer

Angiogenesis has long been considered to facilitate and sustain cancer growth, making the introduction of anti-angiogenic agents that disrupt the vascular endothelial growth factor/receptor (VEGF/VEGFR) pathway an important milestone at the beginning of the 21st century. Originally research on VEGF signaling focused on its survival and mitogenic effects towards endothelial cells, with moderate so far success of anti-angiogenic therapy. However, VEGF can have multiple effects on additional cell types including immune and tumor cells, by directly influencing and promoting tumor cell survival, proliferation and invasion and contributing to an immunosuppressive microenvironment. In this review, we summarize the effects of the VEGF/VEGFR pathway on non-endothelial cells and the resulting implications of anti-angiogenic agents that include direct inhibition of tumor cell growth and immunostimulatory functions. Finally, we present how previously unappreciated studies on VEGF biology, that have demonstrated immunomodulatory properties and tumor regression by disrupting the VEGF/VEGFR pathway, now provide the scientific basis for new combinational treatments of immunotherapy with anti-angiogenic agents.

The proteasome as a druggable target with multiple therapeutic potentialities: Cutting and non-cutting edges

Ubiquitin Proteasome System (UPS) is an adaptable and finely tuned system that sustains proteostasis network under a large variety of physiopathological conditions. Its dysregulation is often associated with the onset and progression of human diseases; hence, UPS modulation has emerged as a promising new avenue for the development of treatments of several relevant pathologies, such as cancer and neurodegeneration. The clinical interest in proteasome inhibition has considerably increased after the FDA approval in 2003 of bortezomib for relapsed/refractory multiple myeloma, which is now used in the front-line setting. Thereafter, two other proteasome inhibitors (carfilzomib and ixazomib), designed to overcome resistance to bortezomib, have been approved for treatment-experienced patients, and a variety of novel inhibitors are currently under preclinical and clinical investigation not only for haematological malignancies but also for solid tumours. However, since UPS collapse leads to toxic misfolded proteins accumulation, proteasome is attracting even more interest as a target for the care of neurodegenerative diseases, which are sustained by UPS impairment. Thus, conceptually, proteasome activation represents an innovative and largely unexplored target for drug development. According to a multidisciplinary approach, spanning from chemistry, biochemistry, molecular biology to pharmacology, this review will summarize the most recent available literature regarding different aspects of proteasome biology, focusing on structure, function and regulation of proteasome in physiological and pathological processes, mostly cancer and neurodegenerative diseases, connecting biochemical features and clinical studies of proteasome targeting drugs.

C6-ceramide treatment inhibits the proangiogenic activity of multiple myeloma exosomes via the miR-29b/Akt pathway

Background

The increased bone marrow angiogenesis is involved in the progression of multiple myeloma (MM) with the underlying mechanism poorly understood. Cancer-released exosomes could play an important role in the pathological angiogenesis through exosomal microRNAs (miRs) delivery. It is reported that miR-29b played an important role in regulating the tumor angiogenesis.

Methods

In this study, we explored the role of C6-ceramide (C6-cer, a Ceramide pathway activator) in the angiogenic effect of MM exosomes and its potential mechanism. MM cells (OPM2 and RPMI-8226) treated with C6-cer were studied for its effects on the endothelial cell (EC) functions.

Results

Our results showed that exosomes released from MM cells treated by C6-cer (Exo^C6-cer) significantly inhibited the proliferation, migration and tube formation of ECs. For mechanism studies, we found that the level of miR-29b was increased in ECs treated by Exo^C6-cer, while mRNA and protein expressions of Akt3, PI3K and VEGFA were decreased in ECs, indicating the involvement of Akt pathway. Furthermore, downregulation of miR-29b by inhibitor administration could prevent the Exo^C6-cer-induced cell proliferation, migration and angiogenesis of ECs, accompanied with the increased expressions of Akt3, PI3K and VEGFA.

Conclusions

Collectively, our data suggest that Exo^C6-cer-mediated miR-29b expression participates in the progression of MM through suppressing the proliferation, migration and angiogenesis of ECs by targeting Akt signal pathway.

Evaluation of Angiogenesis in Multiple Myeloma by VEGF Immunoexpression and Microvessel Density

Background  Multiple myeloma (MM) is a plasma cell disorder characterized by monoclonal proliferation of plasma cells in bone marrow. Plasmablastic MM is a morphologic subset of MM, containing ≥2% plasmablasts of all plasma cells.

Methods  The study included 30 consecutively diagnosed patients of MM (6 plasmablastic, 24 nonplasmablastic) over a span of 2 years. Angiogenesis in MM was assessed by analysis of vascular endothelial growth factor (VEGF) immunoexpression by plasma cells and microvessel density (MVD) using anti-CD34 antibody. CD34 and VEGF immunohistochemical staining was performed in all the 30 cases. Angiogenesis was studied in relation to plasmablastic morphology and clinical profile to determine if any correlation exists between these.

Results  The mean VEGF expression of 80.83 ± 7.36 in plasmablastic myeloma cases was significantly higher compared with a mean VEGF of 53.54 ±17.09 in nonplasmablastic cases. Most of the cases (66.6%) of plasmablastic myeloma exhibited strong (3+) VEGF expression. The difference in mean VEGF expression between plasmablastic and nonplasmablastic cases was found to be statistically significant ( p = 0.001). The mean MVD in plasmablastic cases was 44.8 ± 3.69, while in the nonplasmablastic category, the mean MVD was 23.7 ± 5.14, difference being statistically significant ( p < 0.05). Also, a positive correlation was found between VEGF expression and MVD.

Conclusion  A moderate/strong VEGF intensity and higher MVD were found in cases of plasmablastic MM, suggesting that a more aggressive histological disease may be associated with increased production of VEGF. This finding might be helpful to identify a subset of patients with adverse prognosis and to provide antiangiogenic therapy to improve their survival. However, studies comprising larger number of patients are required to bring out a statistical significance to further substantiate these findings.

Cytokine-Mediated Dysregulation of Signaling Pathways in the Pathogenesis of Multiple Myeloma

Multiple myeloma (MM) is a hematologic disorder of B lymphocytes characterized by the accumulation of malignant plasma cells (PCs) in the bone marrow. The altered plasma cells overproduce abnormal monoclonal immunoglobulins and also stimulate osteoclasts. The host’s immune system and microenvironment are of paramount importance in the growth of PCs and, thus, in the pathogenesis of the disease. The interaction of MM cells with the bone marrow (BM) microenvironment through soluble factors and cell adhesion molecules causes pathogenesis of the disease through activation of multiple signaling pathways, including NF-κβ, PI3K/AKT and JAK/STAT. These activated pathways play a critical role in the inhibition of apoptosis, sustained proliferation, survival and migration of MM cells. Besides, these pathways also participate in developing resistance against the chemotherapeutic drugs in MM. The imbalance between inflammatory and anti-inflammatory cytokines in MM leads to an increased level of pro-inflammatory cytokines, which in turn play a significant role in dysregulation of signaling pathways and proliferation of MM cells; however, the association appears to be inadequate and needs more research. In this review, we are highlighting the recent findings on the roles of various cytokines and growth factors in the pathogenesis of MM and the potential therapeutic utility of aberrantly activated signaling pathways to manage the MM disease.

Role of the Bone Marrow Milieu in Multiple Myeloma Progression and Therapeutic Resistance

Multiple myeloma (MM) is a cancer of the plasma cells within the bone marrow (BM). Studies have shown that the cellular and noncellular components of the BM milieu, such as cytokines and exosomes, play an integral role in MM pathogenesis and progression by mediating drug resistance and inducing MM proliferation. Moreover, the BM microenvironment of patients with MM facilitates cancer tolerance and immune evasion through the expansion of regulatory immune cells, inhibition of antitumor effector cells, and disruption of the antigen presentation machinery. These are of special relevance, especially in the current era of cancer immunotherapy. An improved understanding of the supportive role of the MM BM microenvironment will allow for the development of future therapies targeting MM in the context of the BM milieu to elicit deeper and more durable responses. In the present review, we have discussed our current understanding of the role of the BM microenvironment in MM progression and resistance to therapy and discuss novel potential approaches to alter its pro-MM function.

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.

Identification of Candidate Genes and Therapeutic Agents for Light Chain Amyloidosis Based on Bioinformatics Approach

Objective

Systemic amyloid light chain (AL) amyloidosis is a rare plasma cell disease. However, the regulatory mechanisms of AL amyloidosis have not been thoroughly uncovered, identification of candidate genes and therapeutic agents for this disease is crucial to provide novel insights into exploring the regulatory mechanisms underlying AL amyloidosis.

Methods

The gene expression profile of GSE73040, including 9 specimens from AL amyloidosis patients and 5 specimens from normal control, was downloaded from GEO datasets. Differentially expressed genes (DEGs) were sorted with regard to AL amyloidosis versus normal control group using Limma package. The gene enrichment analyses including GO and KEGG pathway were performed using DAVID website subsequently. Furthermore, the protein–protein interaction (PPI) network for DEGs was constructed by Cytoscape software and STRING database. DEGs were mapped to the connectivity map datasets to identify potential molecular agents of AL amyloidosis.

Results

A total of 1464 DEGs (727 up-regulated, 737 down-regulated) were identified in AL amyloidosis samples versus control samples, these dysregulated genes were associated with the dysfunction of ribosome biogenesis and immune response. PPI network and module analysis uncovered that several crucial genes were defined as candidate genes, including ITGAM, ITGB2, ITGAX, IMP3 and FBL. More importantly, we identified the small molecular agents (AT-9283, Ritonavir and PKC beta-inhibitor) as the potential drugs for AL amyloidosis.

Conclusion

Using bioinformatics approach, we have identified candidate genes and pathways in AL amyloidosis, which can extend our understanding of the cause and molecular mechanisms, and these crucial genes and pathways could act as biomarkers and therapeutic targets for AL amyloidosis.

Multiple Myeloma: Available Therapies and Causes of Drug Resistance

Multiple myeloma (MM) is the second most common blood cancer. Treatments for MM include corticosteroids, alkylating agents, anthracyclines, proteasome inhibitors, immunomodulatory drugs, histone deacetylase inhibitors and monoclonal antibodies. Survival outcomes have improved substantially due to the introduction of many of these drugs allied with their rational use. Nonetheless, MM patients successively relapse after one or more treatment regimens or become refractory, mostly due to drug resistance. This review focuses on the main drugs used in MM treatment and on causes of drug resistance, including cytogenetic, genetic and epigenetic alterations, abnormal drug transport and metabolism, dysregulation of apoptosis, autophagy activation and other intracellular signaling pathways, the presence of cancer stem cells, and the tumor microenvironment. Furthermore, we highlight the areas that need to be further clarified in an attempt to identify novel therapeutic targets to counteract drug resistance in MM patients.

Xanthohumol exhibits anti-myeloma activity in vitro through inhibition of cell proliferation, induction of apoptosis via the ERK and JNK-dependent mechanism, and suppression of sIL-6R and VEGF production

BACKGROUND

Xanthohumol (XN, a hop-derived prenylflavonoid) was found to exert anticancer effects on various cancer types. However, the mechanisms by which XN affects the survival of multiple myeloma cells (MM) are little known. Therefore, our study was undertaken to address this issue.

METHODS

Anti-proliferative activity of XN towards two phenotypically distinct MM cell lines U266 and RPMI8226 was evaluated with the MTT and BrdU assays. Cytotoxicity was determined with the LDH method, whereas apoptosis was assessed by flow cytometry and fluorescence staining. The expression of cell cycle- and apoptosis-related proteins and the activation status of signaling pathways were estimated by immunoblotting and ELISA assays.

RESULTS

XN reduced the viability of RPMI8226 cells more potently than in U266 cells. It blocked cell cycle progression through downregulation of cyclin D1 and increased p21 expression. The marked apoptosis induction in the XN-treated RPMI8226 cells was related to initiation of mitochondrial and extrinsic pathways, as indicated by the altered p53, Bax, and Bcl-2 protein expression, cleavage of procaspase 8 and 9, and elevated caspase-3 activity. The apoptotic process was probably mediated via ROS overproduction and MAPK (ERK and JNK) activation as N-acetylcysteine, or specific inhibitors of these kinases prevented the XN-induced caspase-3 activity and, hence, apoptosis. Moreover, XN decreased sIL-6R and VEGF production in the studied cells.

CONCLUSIONS

ERK and JNK signaling pathways are involved in XN-induced cytotoxicity against MM cells.

GENERAL SIGNIFICANCE

The advanced understanding of the molecular mechanisms of XN action can be useful in developing therapeutic strategies to treat multiple myeloma.

Lymphocyte Subsets and Inflammatory Cytokines of Monoclonal Gammopathy of Undetermined Significance and Multiple Myeloma

Almost all multiple myeloma (MM) cases have been demonstrated to be linked to earlier monoclonal gammopathy of undetermined significance (MGUS). Nevertheless, there are no identified characteristics in the diagnosis of MGUS that have been helpful in differentiating subjects whose cancer may progress to a malignant situation. Regarding malignancy, the role of lymphocyte subsets and cytokines at the beginning of neoplastic diseases is now incontestable. In this review, we have concentrated our attention on the equilibrium between the diverse lymphocyte subsets and the cytokine system and summarized the current state of knowledge, providing an overview of the condition of the entire system in MGUS and MM. In an age where the therapy of neoplastic monoclonal gammopathies largely relies on drugs capable of acting on the immune system (immunomodulants, immunological checkpoint inhibitors, CAR-T), detailed knowledge of the the differences existing in benign and neoplastic forms of gammopathy is the main foundation for the adequate and optimal use of new drugs.

MPT0G413, A Novel HDAC6-Selective Inhibitor, and Bortezomib Synergistically Exert Anti-tumor Activity in Multiple Myeloma Cells

In multiple myeloma (MM), homeostasis is largely maintained by misfolded protein clearance via the proteasomal and aggresomal pathways. Histone deacetylase 6 (HDAC6) binds polyubiquitinated proteins and dynein motors and transports this protein cargo to the aggresome for further degradation. Accordingly, a combination of an HDAC6 inhibitor and bortezomib (BTZ) could increase ubiquitinated protein accumulation, leading to further apoptosis. Here we evaluated the anti-MM activity of MPT0G413, a novel specific HDAC6 inhibitor, using in vitro and in vivo models. MPT0G413 treatment more significantly inhibited cell growth in MM cells than in normal bone marrow cells. Furthermore, the combination of MPT0G413 and BTZ enhanced polyubiquitinated protein accumulation and synergistically reduced MM viability, increased caspase-3, caspase-8, caspase-9 levels, and cleaved poly (ADP) ribosome polymerase and also inhibited adherence of MM cells to bone marrow stromal cells (BMSC) and reduced VEGF and IL-6 levels and cell growth in a co-culture system. The combination treatment disturbed the bone marrow microenvironment and induced synergic, caspase-dependent apoptosis. Xenograft tumor growth significantly decreased in combination-treated SCID mice. In conclusion, MPT0G413 and BTZ synergistically inhibit MM viability, providing a framework for the clinical evaluation of combined therapies for MM.

[Molecular mechanisms and relationship of M2-polarized macrophages with early response in multiple myeloma]

目的

探讨替代活化型巨噬细胞（M2 MΦ）和多发性骨髓瘤（MM）早期治疗反应的关系及其在发病机制中的可能作用。

方法

采用免疫组化法标记240例MM患者骨髓标本中的MΦ；建立体外M2 MΦ诱导培养体系，构建Transwell共培养模型与RPMI 8226和U266细胞共培养，CCK-8法检测M2 MΦ对细胞增殖的影响，流式细胞术检测对地塞米松（1 µ mol/L）诱导骨髓瘤细胞凋亡的影响，ELISA法检测对TNF-α和IL-6表达的影响，real time PCR法检测对趋化因子、血管内皮生长因子（VEGF）及其受体表达的影响。

结果

①依据骨髓组织M2 MΦ浸润程度将患者分为高浸润组（92例）和低浸润组（148例），高浸润组患者早期治疗有效率明显低于低浸润组，差异有统计学意义（23.9%对73.0%，χ²=60.31，P<0.001）。②培养24、36 h，共培养组细胞增殖能力较对照组显著上升：M2 MΦ+RPMI 8226细胞组与对照组比较，P值分别为0.005、0.020；M2 MΦ+U266细胞与对照组比较，P值分别为0.030、0.020。③地塞米松诱导后，共培养组与对照组比较，RPMI 8226细胞凋亡率下降（29.0%对71.0%，t=4.97，P=0.008），U266细胞凋亡率也下降（24.9%对67.7%，t=6.99，P=0.002）。④共培养48 h后，与对照组比较，加入M2 MΦ后可促进RPMI 8226和U266细胞分泌IL-6、TNF-α，促进表达CCL2、CCL3、CCR2、CCR5、VEGFA、VEGFR-1和VEGFR-2。

结论

MM患者骨髓组织M2 MΦ浸润程度和早期治疗反应相关。M2 MΦ通过促进骨髓瘤细胞分泌系列炎症因子、趋化因子和相关受体的表达，从而促进骨髓瘤细胞增殖以及保护骨髓瘤细胞免于凋亡。

Glucocorticoids in multiple myeloma: past, present, and future

Glucocorticoids are a backbone of treatment for multiple myeloma in both the upfront and relapsed/refractory setting. While glucocorticoids have single agent activity in multiple myeloma, in the modern era, they are paired with novel agents to induce high clinical response rates. On the other hand, toxicities of steroid therapy limit high dose delivery and impact patient quality of life. We provide a history of steroid use in multiple myeloma with the aim to understand how steroids have emerged and persisted in the treatment of multiple myeloma. We review mechanisms of glucocorticoid sensitivity and resistance and highlight potential future directions to evaluate steroid responsiveness. Further research in this area will aid in optimizing steroid utilization and help determine when glucocorticoid therapy may no longer benefit patients.

Effects of VEGF-ANG-1-PLA nano-sustained release microspheres on proliferation and differentiation of ADSCs

The improvement of fat graft viability might depend on the presence of multipotent resident adipose derived stem cells (ADSCs) which is the important component of stromal vascular fraction (SVF). Vascular endothelial growth factor (VEGF) and angiogenin-1 (Ang-1) are responsible for neovascularization. However, their half-life is too short to produce a biological effect. We thus investigated whether VEGF-ANG-1-polylactic acid (PLA) microspheres could enhance the angiogenic properties of ADSCs. PLA microspheres containing VEGF and ANG-1 were prepared by in vitro ultrasonic emulsification and characterized according to their encapsulation efficiency (EE), drug-loading rate (DL), particle size, and drug release. The systemic toxicity of empty loaded nanospheres (NPs) and the ability of these microspheres to promote the proliferation and differentiation of ADSCs were evaluated. The EE and DL were above 86% and 0.0288%, respectively [corrected].The drug release was completed after 20 days. Systemic toxicity was verified in ADSCs that received the unloaded NPs. It was observed that ADSCs treated with VEGF-ANG-1-PLA microspheres had an increase in the proliferation and the number of CD31 positive cells. ADSCs proliferation and differentiation toward endothelial cells (ECs) could be enhanced by the addition of VEGF-ANG-1-PLA nano-sustained release microspheres.

Multiple myeloma cancer stem cells

Multiple myeloma (MM) remains incurable despite much progress that has been made in the treatment of the disease. MM cancer stem cell (MMSC), a rare subpopulation of MM cells with the capacity for self-renewal and drug resistance, is considered to lead to disease relapse. Several markers such as side population (SP) and ALDH1+ have been used to identify MMSCs. However, ideally and more precisely, the identification of the MMSCs should rely on MMSCs phenotype. Unfortunately the MMSC phenotype has not been properly defined yet. Drug resistance is the most important property of MMSCs and contributes to disease relapse, but the mechanisms of drug resistance have not been fully understood. The major signaling pathways involved in the regulation of self-renewal and differentiation of MMSCs include Hedgehog (Hh), Wingless (Wnt), Notch and PI3K/Akt/mTOR. However, the precise role of these signaling pathways needs to be clarified. It has been reported that the microRNA profile of MMSCs is remarkably different than that of non-MMSCs. Therefore, the search for targeting MMSCs has also been focused on microRNAs. Complex and mutual interactions between the MMSC and the surrounding bone marrow (BM) microenvironment sustain self-renewal and survival of MMSC. However, the required molecules for the interaction of the MMSC and the surrounding BM microenvironment need to be further identified. In this review, we summarize the current state of knowledge of MMSCs regarding their phenotype, mechanisms of drug resistance, signaling pathways that regulate MMSCs self-renewal and differentiation, abnormal microRNAs expression, and their interactions with the BM microenvironment.

Inflammatory and Anti-Inflammatory Equilibrium, Proliferative and Antiproliferative Balance: The Role of Cytokines in Multiple Myeloma

Multiple myeloma (MM) is typically exemplified by a desynchronized cytokine system with increased levels of inflammatory cytokines. We focused on the contrast between inflammatory and anti-inflammatory systems by assessing the role of cytokines and their influence on MM. The aim of this review is to summarize the available information to date concerning this equilibrium to provide an overview of the research exploring the roles of serum cytokines in MM. However, the association between MM and inflammatory cytokines appears to be inadequate, and other functions, such as pro-proliferative or antiproliferative effects, can assume the role of cytokines in the genesis and progression of MM. It is possible that inflammation, when guided by cancer-specific Th1 cells, may inhibit tumour onset and progression. In a Th1 microenvironment, proinflammatory cytokines (e.g., IL-6 and IL-1) may contribute to tumour eradication by attracting leucocytes from the circulation and by increasing CD4 ⁺ T cell activity. Hence, caution should be used when considering therapies that target factors with pro- or anti-inflammatory activity. Drugs that may reduce the tumour-suppressive Th1-driven inflammatory immune response should be avoided. A better understanding of the relationship between inflammation and myeloma will ensure more effective therapeutic interventions.

Arg-Leu-Tyr-Glu tetrapeptide inhibits tumor progression by suppressing angiogenesis and vascular permeability via VEGF receptor-2 antagonism

The tetrapeptide Arg-Leu-Tyr-Glu (RLYE) is known to inhibit vascular endothelial growth factor-A (VEGF-A)-induced angiogenesis in vitro. Herein, we examined its underlying mechanism and antitumor activity associated with vascular remodeling. RLYE inhibited VEGF-A-induced angiogenesis in a mouse model and suppressed VEGF-A-induced angiogenic signal cascades in human endothelial cells. However, RLYE showed no inhibitory effect on VEGF-A-induced proliferation and migration of multiple myeloma cells expressing VEGF receptor (VEGFR)-1, but not VEGFR-2. In addition, RLYE showed no inhibitory effect on angiogenic activities induced by VEGF-B, basic fibroblast growth factor, epithermal growth factor, sphingosine-1-phosphate, and placental growth factor. RLYE bound specifically to VEGFR-2 at the VEGF-A binding site, thereby blocking VEGF-A-VEGFR-2 binding and VEGF-A-induced VEGFR-2 internalization. The RLYE peptide inhibited tumor growth and metastasis via suppression of tumor angiogenesis in tumor-bearing mice. Moreover, RLYE showed a synergistic effect of the cytotoxic agent irinotecan on tumor cell apoptosis and tumor progression via tumor vessel normalization due to stabilization of VE-cadherin-mediated adherens junction, improvement of pericyte coverage, and inhibition of vascular leakage in tumors. Our results suggest that RLYE can be used as an antiangiogenic and tumor blood vessel remodeling agent for inhibition of tumor growth and metastasis by antagonizing VEGFR-2, with the synergistic anti-cancer effect via enhancement of drug delivery and therapeutic efficacy.

Microvessel Density as a Surrogate Prognostic Marker in Patients with Multiple Myeloma: A Meta-Analysis

BACKGROUND/AIMS

Bone marrow (BM) angiogenesis is considered a hallmark of multiple myeloma (MM) development and progression, and can be quantified with the use of microvessel density (MVD). The purpose of this study is to provide a review and a meta-analysis of the current literature regarding the prognostic value of MVD in the overall survival (OS) of MM patients.

METHODS

MEDLINE was screened for studies evaluating the OS of MM patients with regard to their MVD count in BM trephine. The pooled hazard ratio (HR) and its associated 95% confidence interval (CI) among MM patients with a high and low MVD count was the primary end point. Secondary outcomes included odds ratios (OR) for 12-, 36-, and 60-month survival.

RESULTS

Ten eligible trials were identified for the analysis of the primary end point and 9 for the secondary end points. Pooled HR for OS was 1.85 (95% CI: 1.25-2.73, p = 0.002). The pooled OR of survival were 1.59 (95% CI: 1.02-2.46, p = 0.04) at 12 months, 2.90 (95% CI: 1.68-5.03, p = 0.0001) at 36 months, and 3.42 (95% CI: 2.41-4.85, p < 0.00001) at 60 months, in favor of the low MVD group.

CONCLUSION

This meta-analysis provides persuasive evidence that MVD has significant impact on the clinical outcome of MM patients.

Mesenchymal stromal cells enhance the suppressive effects ofmyeloid-derived suppressor cells of multiple myeloma

Both mesenchymal stromal cells (MSCs) and myeloid-derived suppressor cells (MDSCs) have immunosuppressive properties, and their presence may confer a worse prognosis upon cancer patients. However, whether MSCs can enhance the immunosuppressive effects of MDSCs in MM remains unknown. We evaluated the influence of MSCs on MDSCs growth, apoptosis, and functions. Our results show that MSCs promote proliferation and inhibit apoptosis in MDSCs. Additionally, MSCs enhance the ability of MDSCs by inhibiting T-cell proliferation and IFN-γ production. Furthermore, both the mRNA and protein levels of Arg1 and NOS2 were upregulated in MDSCs. These results suggest that MSCs may exert immunomodulatory effects on MDSCs by upregulating Arg1 and NOS2.

Nuclear medicine imaging of multiple myeloma, particularly in the relapsed setting

Multiple myeloma (MM) is characterized by a monoclonal plasma cell population in the bone marrow. Lytic lesions occur in up to 90 % of patients. For many years, whole-body X-ray (WBX) was the method of choice for detecting skeleton abnormalities. However, the value of WBX in relapsing disease is limited because lesions persist post-treatment, which restricts the capacity to distinguish between old, inactive skeletal lesions and new, active ones. Therefore, alternative techniques are necessary to visualize disease activity. Modern imaging techniques such as magnetic resonance imaging, positron emission tomography and computed tomography offer superior detection of myeloma bone disease and extramedullary manifestations. In particular, the properties of nuclear imaging enable the identification of disease activity by directly targeting the specific cellular properties of malignant plasma cells. In this review, an overview is provided of the effectiveness of radiopharmaceuticals that target metabolism, surface receptors and angiogenesis. The available literature data for commonly used nuclear imaging tracers, the promising first results of new tracers, and our pilot work indicate that a number of these radiopharmaceutical applications can be used effectively for staging and response monitoring of relapsing MM patients. Moreover, some tracers can potentially be used for radio immunotherapy.

MiR-15a/16 regulates the growth of myeloma cells, angiogenesis and antitumor immunity by inhibiting Bcl-2, VEGF-A and IL-17 expression in multiple myeloma

miRNAs have been reported to be involved in the pathogenesis of many cancers. In this article, we investigated the role and the mechanisms of miR-15a/16 in the pathogenesis of multiple myeloma (MM). We found that miR-15a/16 was down-regulated in bone marrow-derived mononuclear cells (BM-MNCs) of newly diagnosed patients with MM and the downregulation of miR-15a/16 was correlated with International Staging System (ISS) stage. We then demonstrated miR-15a/16 inhibited myeloma cells proliferation, and increased apoptosis rate of U266 cells by suppressing the expression of anti-apoptosis protein Bcl-2. We also found miR-15a/16 could decrease VEGF-A and IL-17 levels in the supernatant of myeloma cells. These results indicate that miR-15a/16 may function as a tumor suppressor in MM through multiple regulatory mechanisms and they may be potential targets for the therapy of MM.

Citrullination of histone H3 drives IL-6 production by bone marrow mesenchymal stem cells in MGUS and multiple myeloma

Multiple myeloma (MM), an incurable plasma cell malignancy, requires localisation within the bone marrow. This microenvironment facilitates crucial interactions between the cancer cells and stromal cell types that permit the tumour to survive and proliferate. There is increasing evidence that the bone marrow mesenchymal stem cell (BMMSC) is stably altered in patients with MM-a phenotype also postulated to exist in patients with monoclonal gammopathy of undetermined significance (MGUS) a benign condition that precedes MM. In this study, we describe a mechanism by which increased expression of peptidyl arginine deiminase 2 (PADI2) by BMMSCs in patients with MGUS and MM directly alters malignant plasma cell phenotype. We identify PADI2 as one of the most highly upregulated transcripts in BMMSCs from both MGUS and MM patients, and that through its enzymatic deimination of histone H3 arginine 26, PADI2 activity directly induces the upregulation of interleukin-6 expression. This leads to the acquisition of resistance to the chemotherapeutic agent, bortezomib, by malignant plasma cells. We therefore describe a novel mechanism by which BMMSC dysfunction in patients with MGUS and MM directly leads to pro-malignancy signalling through the citrullination of histone H3R26.

Expression of vaccinia-related kinase 1 (VRK1) accelerates cell proliferation but overcomes cell adhesion mediated drug resistance (CAM-DR) in multiple myeloma

Objective: Vaccinia-related kinase 1 (VRK1) has been reported to participate in the development of a variety of tumors. However, the role of VRK1 in multiple myeloma (MM) has not been investigated. The present study was undertaken to determine the expression and biologic function of VRK1 in human MM.

Methods: First, we constructed a model of cell adhesion in MM, the mRNA and protein level of VRK1 in suspension and adhesion model was analyzed by RT-PCR and western blot. Then, flow cytometry assay and western blot were used to investigate the mechanism of VRK1 in the proliferation of MM cells. In vitro, following using shRNA interfering VRK1 expression, we performed adhesion assay and cell viability assay to determine the effect of VRK1 on adhesive rate and drug sensitivity.

Results: VRK1 was lowly expressed in adherent MM cells and highly expressed in suspended cells. In addition, VRK1 was positively correlated with the proliferation of MM cells by regulating the expression of cell cycle-related protein, such as cyclinD1, CDK2 and p27^kip1. Furthermore, VRK1 could reverse cell adhesion mediated drug resistance (CAM-DR) by down-regulating the ability of cell adhesion.

Conclusion and discussion: Our data supports a role for VRK1 in MM cell proliferation, adhesion, and drug resistance, and it may pave the way for a novel therapeutic approach for CAM-DR in MM.

Multiple myeloma and persistence of drug resistance in the age of novel drugs (Review)

Multiple myeloma (MM) is a mature B cell neoplasm that results in multi-organ failure. The median age of onset, diverse clinical manifestations, heterogeneous survival rate, clonal evolution, intrinsic and acquired drug resistance have impact on the therapeutic management of the disease. Specifically, the emergence of multidrug resistance (MDR) during the course of treatment contributes significantly to treatment failure. The introduction of the immunomodulatory agents and proteasome inhibitors has seen an increase in overall patient survival, however, for the majority of patients, relapse remains inevitable with evidence that these agents, like the conventional chemotherapeutics are also subject to the development of MDR. Clinical management of patients with MM is currently compromised by lack of a suitable procedure to monitor the development of clinical drug resistance in individual patients. The current MM prognostic measures fail to pick the clonotypic tumor cells overexpressing drug efflux pumps, and invasive biopsy is insufficient in detecting sporadic tumors in the skeletal system. This review summarizes the challenges associated with treating the complex disease spectrum of myeloma, with an emphasis on the role of deleterious multidrug resistant clones orchestrating relapse.

A novel hypoxia-selective epigenetic agent RRx-001 triggers apoptosis and overcomes drug resistance in multiple myeloma cells

The hypoxic bone-marrow (BM) microenvironment confers growth/survival and drug-resistance in multiple myeloma (MM) cells. Novel therapies targeting the MM cell in its hypoxic-BM milieu may overcome drug resistance. Recent studies led to the development of a novel molecule RRx-001 with hypoxia-selective epigenetic and Nitric Oxide-donating properties. Here we demonstrate that RRx-001 decreases the viability of MM cell lines and primary patient cells, as well as overcomes drug-resistance. RRx-001 inhibits MM cell growth in the presence of BM stromal cells. RRx-001 induced apoptosis is associated with: 1) activation of caspases; 2) release of ROS and nitrogen-species; 3) induction of DNA damage via ATM/γ-H2AX; and 4) decrease in DNA methytransferase (DNMT) and global methylation. RNA interference study shows a predominant role of DNMT1 in MM cell survival versus DNMT3a or DNMT3b. Deubiquitylating enzyme USP7 stimulates DNMT1 activity; and conversely, USP7-siRNA reduced DNMT1 activity and decreased MM cell viability. RRx-001 plus USP7 inhibitor P5091 triggered synergistic anti-MM activity. MM xenograft studies show that RRx-001 is well tolerated, inhibits tumor growth, and enhances survival. Combining RRx-001 with pomalidomide, bortezomib or SAHA induces synergistic anti-MM activity. Our results provide the rationale for translation of RRx-001, either alone or in combination, to clinical evaluation in MM.