Dll1/Notch activation accelerates multiple myeloma disease development by promoting CD138+ MM-cell proliferation

Notch signalling: multifaceted role in development and disease

Notch pathway is an evolutionarily conserved signalling system that operates to influence an astonishing array of cell fate decisions in different developmental contexts. Notch signalling plays important roles in many developmental processes, making it difficult to name a tissue or a developing organ that does not depend on Notch function at one stage or another. Thus, dysregulation of Notch signalling is associated with many developmental defects and various pathological conditions, including cancer. Although many recent advances have been made to reveal different aspects of the Notch signalling mechanism and its intricate regulation, there are still many unanswered questions related to how the Notch signalling pathway functions in so many developmental events. The same pathway can be deployed in numerous cellular contexts to play varied and critical roles in an organism's development and this is only possible because of the complex regulatory mechanisms of the pathway. In this review, we provide an overview of the mechanism and regulation of the Notch signalling pathway along with its multifaceted functions in different aspects of development and disease.

Notch3 signaling between myeloma cells and osteocytes in the tumor niche promotes tumor growth and bone destruction

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Notch3 promotes proliferation and enhances the osteoclastogenic potential of multiple myeloma cells.

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Notch3 mediates the communication between myeloma cells and osteocytes that leads to tumor proliferation.

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Newly diagnosed MM patients with high Notch3 expression exhibit upregulation of gene signatures associated with cell proliferation and osteoclast formation.

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Genetic inhibition of Notch3 in MM cells markedly decreases tumor growth and bone destruction in an immunocompetent mouse model of MM disease.

In multiple myeloma (MM), communication via Notch signaling in the tumor niche stimulates tumor progression and bone destruction. We previously showed that osteocytes activate Notch, increase Notch3 expression, and stimulate proliferation in MM cells. We show here that Notch3 inhibition in MM cells reduced MM proliferation, decreased Rankl expression, and abrogated the ability of MM cells to promote osteoclastogenesis. Further, Notch3 inhibition in MM cells partially prevented the Notch activation and increased proliferation induced by osteocytes, demonstrating that Notch3 mediates MM-osteocyte communication. Consistently, pro-proliferative and pro-osteoclastogenic pathways were upregulated in CD138⁺ cells from newly diagnosed MM patients with high vs. low NOTCH3 expression. These results show that NOTCH3 signaling in MM cells stimulates proliferation and increases their osteoclastogenic potential. In contrast, Notch2 inhibition did not alter MM cell proliferation or communication with osteocytes. Lastly, mice injected with Notch3 knock-down MM cells had a 50% decrease in tumor burden and a 50% reduction in osteolytic lesions than mice bearing control MM cells. Together, these findings identify Notch3 as a mediator of cell communication among MM cells and between MM cells and osteocytes in the MM tumor niche and warrant future studies to exploit Notch3 as a therapeutic target to treat MM.

Targeting Notch inhibitors to the myeloma bone marrow niche decreases tumor growth and bone destruction without gut toxicity

Systemic inhibition of Notch with γ-secretase inhibitors (GSI) decreases multiple myeloma (MM) tumor growth, but the clinical use of GSI is limited due to its severe gastrointestinal toxicity. In this study, we generated a GSI Notch inhibitor specifically directed to the bone (BT-GSI). BT-GSI administration decreased Notch target gene expression in the bone marrow, but it did not alter Notch signaling in intestinal tissue or induce gut toxicity. In mice with established human or murine MM, treatment with BT-GSI decreased tumor burden and prevented the progression of MM-induced osteolytic disease by inhibiting bone resorption more effectively than unconjugated GSI at equimolar doses. These findings show that BT-GSI has dual anti-myeloma and anti-restorative properties, supporting the therapeutic approach of bone-targeted Notch inhibition for the treatment of MM and associated bone disease.

The multifunctional role of Notch signaling in multiple myeloma

Multiple myeloma (MM) is a hematologic cancer characterized by uncontrolled growth of malignant plasma cells in the bone marrow and currently is incurable. The bone marrow microenvironment plays a critical role in MM. MM cells reside in specialized niches where they interact with multiple marrow cell types, transforming the bone/bone marrow compartment into an ideal microenvironment for the migration, proliferation, and survival of MM cells. In addition, MM cells interact with bone cells to stimulate bone destruction and promote the development of bone lesions that rarely heal. In this review, we discuss how Notch signals facilitate the communication between adjacent MM cells and between MM cells and bone/bone marrow cells and shape the microenvironment to favor MM progression and bone disease. We also address the potential and therapeutic approaches used to target Notch signaling in MM.

Any closer to successful therapy of multiple myeloma? CAR-T cell is a good reason for optimism

Despite many recent advances on cancer novel therapies, researchers have yet a long way to cure cancer. They have to deal with tough challenges before they can reach success. Nonetheless, it seems that recently developed immunotherapy-based therapy approaches such as adoptive cell transfer (ACT) have emerged as a promising therapeutic strategy against various kinds of tumors even the cancers in the blood (liquid cancers). The hematological (liquid) cancers are hard to be targeted by usual cancer therapies, for they do not form localized solid tumors. Until recently, two types of ACTs have been developed and introduced; tumor-infiltrating lymphocytes (TILs) and chimeric antigen receptor (CAR)-T cells which the latter is the subject of our discussion. It is interesting about engineered CAR-T cells that they are genetically endowed with unique cancer-specific characteristics, so they can use the potency of the host immune system to fight against either solid or liquid cancers. Multiple myeloma (MM) or simply referred to as myeloma is a type of hematological malignancy that affects the plasma cells. The cancerous plasma cells produce immunoglobulins (antibodies) uncontrollably which consequently damage the tissues and organs and break the immune system function. Although the last few years have seen significant progressions in the treatment of MM, still a complete remission remains unconvincing. MM is a medically challenging and stubborn disease with a disappointingly low rate of survival rate. When comparing the three most occurring blood cancers (i.e., lymphoma, leukemia, and myeloma), myeloma has the lowest 5-year survival rate (around 40%). A low survival rate indicates a high mortality rate with difficulty in treatment. Therefore, novel CAR-T cell-based therapies or combination therapies along with CAT-T cells may bring new hope for multiple myeloma patients. CAR-T cell therapy has a high potential to improve the remission success rate in patients with MM. To date, many preclinical and clinical trial studies have been conducted to investigate the ability and capacity of CAR T cells in targeting the antigens on myeloma cells. Despite the problems and obstacles, CAR-T cell experiments in MM patients revealed a robust therapeutic potential. However, several factors might be considered during CAR-T cell therapy for better response and reduced side effects. Also, incorporating the CAT-T cell method into a combinational treatment schedule may be a promising approach. In this paper, with a greater emphasis on CAR-T cell application in the treatment of MM, we will discuss and introduce CAR-T cell's history and functions, their limitations, and the solutions to defeat the limitations and different types of modifications on CAR-T cells.

Computationally-obtained structural insights into the molecular interactions between Pidilizumab and binding partners DLL1 and PD-1

Pidilizumab is a monoclonal antibody tested against several types of malignancies, such as lymphoma and metastatic melanoma, showing promising results. In 2016, the FDA put Pidilizumab's clinical studies on partial hold due to emerging evidence pointing to the antibody target uncertainty. Although initial studies indicated an interaction with the PD-1 checkpoint receptor, recent updates assert that Pidilizumab binds primarily to Notch ligand DLL1. However, a detailed description of which interactions coordinate antibody-antigen complex formation is lacking. Therefore, this study uses computational tools to identify molecular interactions between Pidilizumab and its reported targets PD-1 and DLL1. A docking methodology was validated and applied to determine the binding modes between modeled Pidilizumab scFvs and the two antigens. We used Molecular Dynamics (MD) simulations to verify the complexes' stability and submitted the resulting trajectory files to MM/PBSA and Principal Component Analysis. A set of different prediction tools determined scFv interface hot-spots. Whereas docking and MD simulations revealed that the antibody fragments do not interact straightforwardly with PD-1, ten scFv hot-spots, including Met93 and Leu112, mediated the interaction with the DLL1 C2 domain. The interaction triggered a conformational selection-like effect on DLL1, allowing new hydrogen bonds on the β3-β4 interface loop. The unprecedented structural data on Pidilizumab's interactions provided novel evidence that its legitimate target is the DLL1 protein and offered structural insight on how these molecules interact, shedding light on the pathways that could be affected by the use of this essential immunobiological.Communicated by Ramaswamy H. Sarma.

Metformin Induces Apoptosis and Inhibits Notch1 in Malignant Pleural Mesothelioma Cells

Malignant pleural mesothelioma (MPM) is an aggressive asbestos-related cancer arising from the mesothelial cells lining the pleural cavity. MPM is characterized by a silent clinical progression and a highly resistance to conventional chemo/radio-therapies. MPM patients die in a few months/years from diagnosis. Notch signaling is a well-conserved cell communication system, which regulates many biological processes. In humans, the dysregulation of Notch pathway potentially contributes to cancer onset/progression, including MPM. Metformin is the first-line drug used to treat type 2 diabetes mellitus. Metformin is proven to be an effective antitumor drug in preclinical models of different types of cancer. To date, clinical efficacy is being studied in many clinical trials. In this study, the anti-proliferative effect of metformin on MPM cells and the putative involvement of Notch1 as a mediator of metformin activities, were investigated. MPM cells showed high levels of Notch1 activation compared to normal pleural mesothelial cells. Furthermore, metformin treatment hampered MPM cell proliferation and enhanced the apoptotic process, accompanied by decreased Notch1 activation.

Cell-surface heparan sulfate proteoglycans as multifunctional integrators of signaling in cancer

Proteoglycans (PGs) represent a large proportion of the components that constitute the extracellular matrix (ECM). They are a diverse group of glycoproteins characterized by a covalent link to a specific glycosaminoglycan type. As part of the ECM, heparan sulfate (HS)PGs participate in both physiological and pathological processes including cell recruitment during inflammation and the promotion of cell proliferation, adhesion and motility during development, angiogenesis, wound repair and tumor progression. A key function of HSPGs is their ability to modulate the expression and function of cytokines, chemokines, growth factors, morphogens, and adhesion molecules. This is due to their capacity to act as ligands or co-receptors for various signal-transducing receptors, affecting pathways such as FGF, VEGF, chemokines, integrins, Wnt, notch, IL-6/JAK-STAT3, and NF-κB. The activation of those pathways has been implicated in the induction, progression, and malignancy of a tumor. For many years, the study of signaling has allowed for designing specific drugs targeting these pathways for cancer treatment, with very positive results. Likewise, HSPGs have become the subject of cancer research and are increasingly recognized as important therapeutic targets. Although they have been studied in a variety of preclinical and experimental models, their mechanism of action in malignancy still needs to be more clearly defined. In this review, we discuss the role of cell-surface HSPGs as pleiotropic modulators of signaling in cancer and identify them as promising markers and targets for cancer treatment.

Plasma enhance drug sensitivity to bortezomib by inhibition of cyp1a1 in myeloma cells

Background

Drug resistance is one of the major problems encountered in clinical therapy of multiple myeloma treatment. Combination treatment with several drugs may increase the sensitivity and overcome drug resistance.

Methods

Here, we combined chemotherapy with a newly developed technology, cold atmospheric plasma, to enhance drug sensitivity.

Results

We found that plasma treatment had a synergistic anti-cancer effect with a first line drug (bortezomib). Based on our previous study, we further found that plasma treatment could inhibit Notch pathway and down-regulate cyp1a1 expression and enzyme activity, which contributing to the enhanced drug sensitivity to bortezomib after combination of bortezomib with gas plasma.

Conclusions

Our results showed a new strategy to overcome drug resistance by combination of traditional chemotherapy with cold atmospheric plasma.

Chimeric Antigen Receptor-Modified T Cell Therapy in Multiple Myeloma: Beyond B Cell Maturation Antigen

Chimeric antigen receptor (CAR)-modified T cell therapy is a rapidly emerging immunotherapeutic approach that is revolutionizing cancer treatment. The impressive clinical results obtained with CAR-T cell therapy in patients with acute lymphoblastic leukemia and lymphoma have fueled the development of CAR-T cells targeting other malignancies, including multiple myeloma (MM). The field of CAR-T cell therapy for MM is still in its infancy, but remains promising. To date, most studies have been performed with B cell maturation antigen (BCMA)-targeted CARs, for which high response rates have been obtained in early-phase clinical trials. However, responses are usually temporary, and relapses have frequently been observed. One of the major reasons for relapse is the loss or downregulation of BCMA expression following CAR-T therapy. This has fostered a search for alternative target antigens that are expressed on the MM cell surface. In this review, we provide an overview of myeloma target antigens other than BCMA that are currently being evaluated in pre-clinical and clinical studies.

The Notch ligand DLL1 exerts carcinogenic features in human breast cancer cells

CONCLUSIONS

These findings provide further evidence that DLL1 exerts carcinogenic effects in BC cells. The dissimilar effects of DLL1 downregulation observed amongst MCF-7, BT474, and MDA-MB-231 cells is likely due to their distinctive genetic and biologic characteristics, suggesting that DLL1 contributes to BC through various mechanisms.

Downregulation of syndecan‑1 expression induces activation of hepatic stellate cells via the TGF‑β1/Smad3 signaling pathway

The activation of hepatic stellate cells (HSCs) is considered associated with liver fibrosis. However, the exact role of syndecan‑1 (SDC1), a protein that regulates the interaction between cells and the microenvironment, in the activation of HSCs resulting in liver fibrosis remains elusive. The objective of the present study was to explore the effects and mechanism of action of SDC1 in the activation of HSCs. HSCs were isolated from mouse liver and cultured to detect the expression of SDC1, transforming growth factor (TGF)‑β1, Smad3 and α‑smooth muscle actin (α‑SMA; a marker of HSC activation) by western blotting and reverse transcription‑quantitative PCR. The expression of SDC1 was found to be downregulated, while the expression of TGF‑β1, Smad3 and α‑SMA was upregulated in HSCs during cell culture. In addition, following stimulation of HSCs with recombinant SDC1, the expression of TGF‑β1, Smad3 and α‑SMA in HSCs was downregulated, whereas small interfering RNA targeting Smad3 antagonized the effects of recombinant SDC1 on α‑SMA. Taken together, these data suggest that SDC1 plays a key role in the development of liver fibrosis.

Multiple Myeloma: What Do We Do About Immunodeficiency?

Multiple myeloma (MM) is an incurable hematological malignancy. Immunodeficiency results in the incapability of immunity to eradicate both tumor cells and pathogens. Immunotherapies along with antibiotics and other anti-infectious agents are applied as substitutes for immunity in MM. Immunotherapies including monoclonal antibodies, immune checkpoints inhibitors, affinity- enhanced T cells, chimeric antigen receptor T cells and dendritic cell vaccines are revolutionizing MM treatment. By suppressing the pro-inflammatory milieu and pathogens, prophylactic and therapeutic antibiotics represent anti-tumor and anti-infection properties. It is expected that deeper understanding of infection, immunity and tumor physio-pathologies in MM will accelerate the optimization of combined therapies, thus improving prognosis in MM.

Solamargine inhibits proliferation and promotes apoptosis of CM-319 human chordoma cells through suppression of notch pathway

Background

Solamargine (SM), which represents a natural steroid alkaloid glycoside compound and a cytotoxic agent, has been proved to enhance the sensitivity of lung cancer cells to tumor necrosis factors (TNFs). In this study, we aimed to investigate the roles and mechanisms of SM in chordoma.

Methods

Cell viability, proliferation, apoptosis and cell cycle were measured by cell counting Kit-8 (CCK-8) assay, 5(6)-carboxyfluorescein diacetate succinimidyl ester (CFSE) labeling and flow cytometry (FCM), respectively. Western blot and quantitative real-time reverse transcription PCR (qRT-PCR) assays were performed to detect the expressions of related mRNAs and proteins.

Results

The results revealed that SM distinctly suppressed the proliferation of CM-319 cells. SM significantly induced the CM-319 cells apoptosis through up-regulating the expression levels of Caspase-3/8/9. The cell cycle of CM-319 cells was blocked by SM in G1 phase. Moreover, SM could significantly suppress the Notch pathway in CM-319 cells.

Conclusions

In conclusion, SM suppressed the proliferation and enhanced the apoptosis ability of CM-319 cells via suppressing the Notch pathway. The results suggested that SM might be a novel therapeutic agent and supported the utilization of SM in chordoma.

Understanding Immune Evasion and Therapeutic Targeting Associated with PD-1/PD-L1 Pathway in Diffuse Large B-cell Lymphoma

In tumor microenvironment, the programmed death 1 (PD-1) immune checkpoint has a crucial role of mechanism of T cell exhaustion leading to tumor evasion. Ligands of PD-1, programmed death ligand 1/2 (PD-L1/L2) are over-expressed in tumor cells and participate in prolonged tumor progression and survivals. Recently, clinical trials for patients who failed to obtain an optimal response prior to standardized chemotherapy in several solid cancers have been focused on targeting therapy against PD-1 to reduce disease progression rates and prolonged survivals. Since various inhibitors targeting the immune checkpoint in PD-1/PD-L1 pathway in solid cancers have been introduced, promising approach using anti-PD-1 antibodies were attempted in several types of hematologic malignances. In diffuse large B cell lymphoma (DLBCL) as the most common and aggressive B cell type of non-Hodgkin’s lymphoma, anti-PD-1 and anti-PD-L1 antibodies were studies in various clinical trials. In this review, we summarized the results of several studies associated with PD-1/PD-L1 pathway as an immune evasion mechanism and described clinical trials about targeting therapy against PD-1/PD-L1 pathway in DLBCL.

Re-establishing Apoptosis Competence in Bone Associated Cancers via Communicative Reprogramming Induced Through Notch Signaling Inhibition

Notch and its ligands on adjacent cells are key mediators of cellular communication during developmental choice in embryonic and adult tissues. This communication is frequently altered in the pathological interaction between cancer cells and healthy cells of the microenvironment due to the aberrant expression of tumor derived Notch receptors or ligands, that results in homotypic or heterotypic Notch signaling activation in tumor cells or surrounding stromal cells. A deadly consequence of this pathological communication is pharmacological resistance that results in patient's relapse. We will provide a survey of the role of Notch signaling in the bone marrow (BM), a microenvironment with a very high capacity to support several types of cancer, including primary cancers such as osteosarcoma or multiple myeloma and bone metastases from carcinomas. Moreover, in the BM niche several hematological malignancies maintain a reservoir of cancer stem cells, characterized by higher intrinsic drug resistance. Cell-cell communication in BM-tumor interaction triggers signaling pathways by direct contact and paracrine communication through soluble growth factors or extracellular vesicles, which can deliver specific molecules such as mRNAs, miRNAs, proteins, metabolites, etc. enabling tumor cells to reprogram the healthy cells of the microenvironment inducing them to support tumor growth. In this review we will explore how the dysregulated Notch activity contributes to tumor-mediated reprogramming of the BM niche and drug resistance, strengthening the rationale of a Notch-directed therapy to re-establish apoptosis competence in cancer.

The Emerging Role of Osteocytes in Cancer in Bone

Advances in the last decade have established the osteocyte, the most abundant cell in bone, as a dynamic and multifunctional cell capable of controlling bone homeostasis by regulating the function of both osteoblasts and osteoclasts. In addition, accumulating evidence demonstrates that osteocyte function is altered in several skeletal disorders, and targeting osteocytes and their derived factors improves skeletal health. Despite the remarkable progress in our understanding of osteocyte biology, there has been a paucity of information regarding the role of osteocytes in the progression of cancer in bone. Exciting, recent discoveries suggest that tumor cells communicate with osteocytes to generate a microenvironment that supports the growth and survival of cancer cells and stimulates bone destruction. This review features these novel findings and discussions regarding the impact of chemotherapy on osteocyte function and the potential of targeting osteocytes for the treatment of cancer in bone. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

NOTCH Signaling Is Activated through Mechanical Strain in Human Bone Marrow-Derived Mesenchymal Stromal Cells

Skeletal development and remodeling of adult bone are critically controlled by activated NOTCH signaling in genetically modified mice. It is yet unclear whether NOTCH signaling is activated by mechanical strain sensed by bone cells. We found that expression of specific NOTCH target genes is induced after in vivo tibial mechanical loading in wild-type mice. We further applied mechanical strain through cyclic stretching in human bone marrow-derived mesenchymal stromal cells (BMSCs) in vitro by using a bioreactor system and detected upregulation of NOTCH target gene expression. Inhibition of the NOTCH pathway in primary BMSCs as well as telomerase-immortalized human BMSCs (hMSC-TERT) through the gamma-secretase inhibitor GSI XII blocked mechanotransduction and modulated actin cytoskeleton organization. Short-hairpin RNA gene silencing identified NOTCH2 as the key receptor mediating NOTCH effects on hMSC-TERT cells. Our data indicate a functional link between NOTCH activation and mechanotransduction in human BMSCs. We suggest that NOTCH signaling is an important contributor to molecular mechanisms that mediate the bone formation response to mechanical strain.

Homotypic and Heterotypic Activation of the Notch Pathway in Multiple Myeloma-Enhanced Angiogenesis: A Novel Therapeutic Target?

Interactions of multiple myeloma (MM) cells with endothelial cells (ECs) enhance angiogenesis and MM progression. Here, we investigated the role of Notch signaling in the cross talk between ECs and MM cells enabling angiogenesis. MMECs showed higher expression of Jagged1/2 ligands, of activated Notch1/2 receptors, and of Hes1/Hey1 Notch target genes than ECs from monoclonal gammopathy of undetermined significance patients, suggesting that homotypic activation of Notch pathway occurs in MM. MM cells co-cultured with MMECs triggered Notch activation in these cells through a cell-to-cell contact-dependent way via Jagged1/2, resulting in Hes1/Hey1 overexpression. The angiogenic effect of Notch pathway was analyzed through Notch1/2·siRNAs and the γ-secretase inhibitor MK-0752 by in vitro (adhesion, migration, chemotaxis, angiogenesis) and in vivo (Vk12598/C57B/6 J mouse model) studies. Activated Notch1/2 pathway was associated with the overangiogenic MMEC phenotype: Notch1/2 knockdown or MK-0752 treatment reduced Hes1/Hey1 expression, impairing in vitro angiogenesis of both MMECs alone and co-cultured with MM cells. MM cells were unable to restore angiogenic abilities of treated MMECs, proving that MMEC angiogenic activities closely rely on Notch pathway. Furthermore, Notch1/2 knockdown affected VEGF/VEGFR2 axis, indicating that the Notch pathway interferes with VEGF-mediated control on angiogenesis. MK-0752 reduced secretion of proangiogenic/proinflammatory cytokines in conditioned media, thus inhibiting blood vessel formation in the CAM assay. In the Vk12598/C57B/6 J mouse, MK-0752 treatment restrained angiogenesis by reducing microvessel density. Overall, homotypic and heterotypic Jagged1/2-mediated Notch activation enhances MMECs angiogenesis. Notch axis inhibition blocked angiogenesis in vitro and in vivo, suggesting that the Notch pathway may represent a novel therapeutic target in MM.

Cancer Immunotherapy in Diffuse Large B-Cell Lymphoma

Remarkable progress has been made in the field of cancer immunotherapy in the past few years. Immunotherapy has become a standard treatment option for patients with various cancers, including melanoma, lymphoma, and carcinomas of the lungs, kidneys, bladder, and head and neck. Promising immunotherapy approaches, such as chimeric antigen receptor (CAR) T cell therapy and therapeutic blockade of immune checkpoints, in particular cytotoxic T lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 pathway (PD-1/PD-L1), have boosted the development of new therapeutic regimens for patients with cancer. Immunotherapeutic strategies for diffuse large B-cell lymphoma (DLBCL) include monoclonal anti-CD20 antibody (rituximab), monoclonal anti-PD-1 antibodies (nivolumab and pembrolizumab), monoclonal anti-PD-L1 antibodies (avelumab, durvalumab, and atezolizumab) and chimeric antigen receptor (CAR) T cell therapy. In this review, we outline the latest highlights and progress in using immunotherapy to treat patients with DLBCL, with a focus on the therapeutic blockade of PD-1/PD-L1 and CAR T cell therapy in DLBCL. We also discuss current clinical trials of PD-1/PD-L1 and CAR T cell therapy and review the challenges and opportunities of using immunotherapy for the treatment of DLBCL.

Actin cytoskeleton regulator Arp2/3 complex is required for DLL1 activating Notch1 signaling to maintain the stem cell phenotype of glioma initiating cells

Glioblastoma (GBM) is the most common and lethal primary intracranial tumor. Actin cytoskeleton regulator Arp2/3 complex stimulates glioma cell motility and migration, and thus triggers tumor invasion. However, little is known regarding the role of actin cytoskeleton in maintaining the stem cell phenotype. Here, we showed that Arp2/3 complex improved stem cell phenotype maintenance through sustaining the activated Notch signaling. ShRNA targeting Notch ligand Delta-like 1 (DLL1) decreased CD133 and Nestin expression, and impaired the self-renewal ability of CD133+ U87-MG and U251-MG glioma cells, indicating DLL1/Notch1 signaling promoted stem cell phenotype maintenance. Interestingly, inhibiting Arp2/3 complex also induced the similar effect of shDLL1. Silencing DLL1 in the Arp2/3 inhibited CD133+ cells did not further abrogate the stem cell phenotype, suggesting DLL1 function requires Arp2/3 complex in glioma initiating cells (GICs). However, exogenous soluble DLL1 (sDLL1) instead of endogenous DLL1 rescued the Arp2/3 inhibition-induced stem cell phenotype suppression. The underlying mechanism was that Arp2/3 inhibition impeded DLL1 vesicular transport from cytoplasm to cell membrane, which resulted in DLL1 unable to activate Notch pathway. Furthermore, we illustrated that Arp2/3 inhibition abolished the tumorigenicity of CD133+ U87-MG neurosphere cells in the intracranial model. These findings suggested that cytoskeleton maintained the stem cell phenotype in GBM, which provide novel therapeutic strategy that anti-invasive targeted therapies may help eliminate GICs.

Intracellular ROS mediates gas plasma-facilitated cellular transfection in 2D and 3D cultures

This study reports the potential of cold atmospheric plasma (CAP) as a versatile tool for delivering oligonucleotides into mammalian cells. Compared to lipofection and electroporation methods, plasma transfection showed a better uptake efficiency and less cell death in the transfection of oligonucleotides. We demonstrated that the level of extracellular aqueous reactive oxygen species (ROS) produced by gas plasma is correlated with the uptake efficiency and that this is achieved through an increase of intracellular ROS levels and the resulting increase in cell membrane permeability. This finding was supported by the use of ROS scavengers, which reduced CAP-based uptake efficiency. In addition, we found that cold atmospheric plasma could transfer oligonucleotides such as siRNA and miRNA into cells even in 3D cultures, thus suggesting the potential for unique applications of CAP beyond those provided by standard transfection techniques. Together, our results suggest that cold plasma might provide an efficient technique for the delivery of siRNA and miRNA in 2D and 3D culture models.

Bidirectional Notch Signaling and Osteocyte-Derived Factors in the Bone Marrow Microenvironment Promote Tumor Cell Proliferation and Bone Destruction in Multiple Myeloma

In multiple myeloma, an overabundance of monoclonal plasma cells in the bone marrow induces localized osteolytic lesions that rarely heal due to increased bone resorption and suppressed bone formation. Matrix-embedded osteocytes comprise more than 95% of bone cells and are major regulators of osteoclast and osteoblast activity, but their contribution to multiple myeloma growth and bone disease is unknown. Here, we report that osteocytes in a mouse model of human MM physically interact with multiple myeloma cells in vivo, undergo caspase-3-dependent apoptosis, and express higher RANKL (TNFSF11) and sclerostin levels than osteocytes in control mice. Mechanistic studies revealed that osteocyte apoptosis was initiated by multiple myeloma cell-mediated activation of Notch signaling and was further amplified by multiple myeloma cell-secreted TNF. The induction of apoptosis increased osteocytic Rankl expression, the osteocytic Rankl/Opg (TNFRSF11B) ratio, and the ability of osteocytes to attract osteoclast precursors to induce local bone resorption. Furthermore, osteocytes in contact with multiple myeloma cells expressed high levels of Sost/sclerostin, leading to a reduction in Wnt signaling and subsequent inhibition of osteoblast differentiation. Importantly, direct contact between osteocytes and multiple myeloma cells reciprocally activated Notch signaling and increased Notch receptor expression, particularly Notch3 and 4, stimulating multiple myeloma cell growth. These studies reveal a previously unknown role for bidirectional Notch signaling that enhances MM growth and bone disease, suggesting that targeting osteocyte-multiple myeloma cell interactions through specific Notch receptor blockade may represent a promising treatment strategy in multiple myeloma.

Notch signaling deregulation in multiple myeloma: A rational molecular target

Despite recent therapeutic advances, multiple myeloma (MM) is still an incurable neoplasia due to intrinsic or acquired resistance to therapy. Myeloma cell localization in the bone marrow milieu allows direct interactions between tumor cells and non-tumor bone marrow cells which promote neoplastic cell growth, survival, bone disease, acquisition of drug resistance and consequent relapse. Twenty percent of MM patients are at high-risk of treatment failure as defined by tumor markers or presentation as plasma cell leukemia. Cumulative evidences indicate a key role of Notch signaling in multiple myeloma onset and progression. Unlike other Notch-related malignancies, where the majority of patients carry gain-of-function mutations in Notch pathway members, in MM cell Notch signaling is aberrantly activated due to an increased expression of Notch receptors and ligands; notably, this also results in the activation of Notch signaling in surrounding stromal cells which contributes to myeloma cell proliferation, survival and migration, as well as to bone disease and intrinsic and acquired pharmacological resistance. Here we review the last findings on the mechanisms and the effects of Notch signaling dysregulation in MM and provide a rationale for a therapeutic strategy aiming at inhibiting Notch signaling, along with a complete overview on the currently available Notch-directed approaches.

Modulatory effects of bortezomib on host immune cell functions

Bortezomib is an inhibitor of the ubiquitin-proteasome proteolytic pathway responsible for intracellular protein turnover. Cellular proteins controlled by this pathway represent a diverse group of potential therapeutic targets, particularly in cancer cells, which exploit this proteasomal pathway to promote their growth and diminish apoptosis. Along with inhibiting the proteasome and thus sensitizing tumor cells to apoptosis, bortezomib may also have multiple effects on the host immune responses. This review summarizes the effects that bortezomib may play on immune cell subsets in various disease states in modifying lymphocyte receptors, ligands, the expression of various cytokines and chemokines and their downstream signaling. We also propose steps that can be taken to refine combinatorial strategies that include bortezomib to improve current immunotherapeutic approaches.

Type 2 diabetes-related variants influence the risk of developing multiple myeloma: results from the IMMEnSE consortium

Type 2 diabetes (T2D) has been suggested to be a risk factor for multiple myeloma (MM), but the relationship between the two traits is still not well understood. The aims of this study were to evaluate whether 58 genome-wide-association-studies (GWAS)-identified common variants for T2D influence the risk of developing MM and to determine whether predictive models built with these variants might help to predict the disease risk. We conducted a case-control study including 1420 MM patients and 1858 controls ascertained through the International Multiple Myeloma (IMMEnSE) consortium. Subjects carrying the KCNQ1rs2237892T allele or the CDKN2A-2Brs2383208G/G, IGF1rs35767T/T and MADDrs7944584T/T genotypes had a significantly increased risk of MM (odds ratio (OR)=1.32-2.13) whereas those carrying the KCNJ11rs5215C, KCNJ11rs5219T and THADArs7578597C alleles or the FTOrs8050136A/A and LTArs1041981C/C genotypes showed a significantly decreased risk of developing the disease (OR=0.76-0.85). Interestingly, a prediction model including those T2D-related variants associated with the risk of MM showed a significantly improved discriminatory ability to predict the disease when compared to a model without genetic information (area under the curve (AUC)=0.645 vs AUC=0.629; P=4.05×10(-) (06)). A gender-stratified analysis also revealed a significant gender effect modification for ADAM30rs2641348 and NOTCH2rs10923931 variants (Pinteraction=0.001 and 0.0004, respectively). Men carrying the ADAM30rs2641348C and NOTCH2rs10923931T alleles had a significantly decreased risk of MM whereas an opposite but not significant effect was observed in women (ORM=0.71 and ORM=0.66 vs ORW=1.22 and ORW=1.15, respectively). These results suggest that TD2-related variants may influence the risk of developing MM and their genotyping might help to improve MM risk prediction models.

In Situ OH Generation from O2- and H2O2 Plays a Critical Role in Plasma-Induced Cell Death

Reactive oxygen and nitrogen species produced by cold atmospheric plasma (CAP) are considered to be the most important species for biomedical applications, including cancer treatment. However, it is not known which species exert the greatest biological effects, and the nature of their interactions with tumor cells remains ill-defined. These questions were addressed in the present study by exposing human mesenchymal stromal and LP-1 cells to reactive oxygen and nitrogen species produced by CAP and evaluating cell viability. Superoxide anion (O2-) and hydrogen peroxide (H2O2) were the two major species present in plasma, but their respective concentrations were not sufficient to cause cell death when used in isolation; however, in the presence of iron, both species enhanced the cell death-inducing effects of plasma. We propose that iron containing proteins in cells catalyze O2- and H2O2 into the highly reactive OH radical that can induce cell death. The results demonstrate how reactive species are transferred to liquid and converted into the OH radical to mediate cytotoxicity and provide mechanistic insight into the molecular mechanisms underlying tumor cell death by plasma treatment.

Multiple myeloma-related bone disease: state-of-art and next future treatments

SUMMARY 

Multiple myeloma (MM) is a plasma cell malignancy associated with the development of life-threatening and/or severe osteolytic lesions, which significantly worsen the quality of life of affected patients. MM-related bone disease (BD) is the result of an overwhelming osteoclastic activity, while osteoblast-mediated bone formation is inhibited. Bisphosphonates are still the mainstay of therapy for BD. However, these drugs are associated with mid long-term sequelae. In this work, we review the pathogenesis and currently available therapies of MM-related BD. We describe the most recent and promising findings that may translate in changing the clinical practice in the next future.

Notch signaling drives multiple myeloma induced osteoclastogenesis

Multiple myeloma (MM) is closely associated with bone destruction. Once migrated to the bone marrow, MM cells unbalance bone formation and resorption via the recruitment and maturation of osteoclast precursors. The Notch pathway plays a key role in different types of cancer and drives several biological processes relevant in MM, including cell localization within the bone marrow, proliferation, survival and pharmacological resistance. Here we present evidences that MM can efficiently drive osteoclastogenesis by contemporaneously activating Notch signaling on tumor cells and osteoclasts through the aberrant expression of Notch ligands belonging to the Jagged family. Active Notch signaling in MM cells induces the secretion of the key osteoclastogenic factor, RANKL, which can be boosted in the presence of stromal cells. In turn, MM cells-derived RANKL causes the upregulation of its receptor, RANK, and Notch2 in pre-osteoclasts. Notch2 stimulates osteoclast differentiation by promoting autocrine RANKL signaling. Finally, MM cells through Jagged ligands expression can also activate Notch signaling in pre-osteoclast by direct contact. Such synergism between tumor cells and pre-osteoclasts in MM-induced osteoclastogenesis can be disrupted by silencing tumor-derived Jagged1 and 2. These results make the Jagged ligands new promising therapeutic targets in MM to contrast bone disease and the associated co-morbidities.

Drug resistance in multiple myeloma: latest findings and new concepts on molecular mechanisms

In the era of new and mostly effective therapeutic protocols, multiple myeloma still tends to be a hard-to-treat hematologic cancer. This hallmark of the disease is in fact a sequel to drug resistant phenotypes persisting initially or emerging in the course of treatment. Furthermore, the heterogeneous nature of multiple myeloma makes treating patients with the same drug challenging because finding a drugable oncogenic process common to all patients is not yet feasible, while our current knowledge of genetic/epigenetic basis of multiple myeloma pathogenesis is outstanding. Nonetheless, bone marrow microenvironment components are well known as playing critical roles in myeloma tumor cell survival and environment-mediated drug resistance happening most possibly in all myeloma patients. Generally speaking, however; real mechanisms underlying drug resistance in multiple myeloma are not completely understood. The present review will discuss the latest findings and concepts in this regard. It reviews the association of important chromosomal translocations, oncogenes (e.g. TP53) mutations and deranged signaling pathways (e.g. NFκB) with drug response in clinical and experimental investigations. It will also highlight how bone marrow microenvironment signals (Wnt, Notch) and myeloma cancer stem cells could contribute to drug resistance in multiple myeloma.

Multiple myeloma mesenchymal stromal cells: Contribution to myeloma bone disease and therapeutics

Multiple myeloma is a hematological malignancy in which clonal plasma cells proliferate and accumulate within the bone marrow. The presence of osteolytic lesions due to increased osteoclast (OC) activity and suppressed osteoblast (OB) function is characteristic of the disease. The bone marrow mesenchymal stromal cells (MSCs) play a critical role in multiple myeloma pathophysiology, greatly promoting the growth, survival, drug resistance and migration of myeloma cells. Here, we specifically discuss on the relative contribution of MSCs to the pathophysiology of osteolytic lesions in light of the current knowledge of the biology of myeloma bone disease (MBD), together with the reported genomic, functional and gene expression differences between MSCs derived from myeloma patients (pMSCs) and their healthy counterparts (dMSCs). Being MSCs the progenitors of OBs, pMSCs primarily contribute to the pathogenesis of MBD because of their reduced osteogenic potential consequence of multiple OB inhibitory factors and direct interactions with myeloma cells in the bone marrow. Importantly, pMSCs also readily contribute to MBD by promoting OC formation and activity at various levels (i.e., increasing RANKL to OPG expression, augmenting secretion of activin A, uncoupling ephrinB2-EphB4 signaling, and through augmented production of Wnt5a), thus further contributing to OB/OC uncoupling in osteolytic lesions. In this review, we also look over main signaling pathways involved in the osteogenic differentiation of MSCs and/or OB activity, highlighting amenable therapeutic targets; in parallel, the reported activity of bone-anabolic agents (at preclinical or clinical stage) targeting those signaling pathways is commented.

Notch pathway inhibition controls myeloma bone disease in the murine MOPC315.BM model

Despite evidence that deregulated Notch signalling is a master regulator of multiple myeloma (MM) pathogenesis, its contribution to myeloma bone disease remains to be resolved. Notch promotes survival of human MM cells and triggers human osteoclast activity in vitro. Here, we show that inhibition of Notch through the γ-secretase inhibitor XII (GSI XII) induces apoptosis of murine MOPC315.BM myeloma cells with high Notch activity. GSI XII impairs murine osteoclast differentiation of receptor activator of NF-κB ligand (RANKL)-stimulated RAW264.7 cells in vitro. In the murine MOPC315.BM myeloma model GSI XII has potent anti-MM activity and reduces osteolytic lesions as evidenced by diminished myeloma-specific monoclonal immunoglobulin (Ig)-A serum levels and quantitative assessment of bone structure changes via high-resolution microcomputed tomography scans. Thus, we suggest that Notch inhibition through GSI XII controls myeloma bone disease mainly by targeting Notch in MM cells and possibly in osteoclasts in their microenvironment. We conclude that Notch inhibition is a valid therapeutic strategy in MM.

Fact or fiction--identifying the elusive multiple myeloma stem cell

Multiple Myeloma (MM) is a debilitating disease of proliferating and malignant plasma cells that is currently incurable. The ability of monoclonal recurrence of disease suggests it might arise from a stem cell-like population capable of self-renewal. The difficulty to isolate the cancer stem-like cell in MM has introduced confusion toward this hypothesis. However, recent evidence has suggested that MM originates from the B cell lineage with memory-B cell like features, allowing for self-renewal of the progenitor-like status and differentiation to a monoclonal plasma cell population. Furthermore, this tumor-initiating cell uses signaling pathways and microenvironment similar to the hematopoietic stem cell, though hijacking these mechanisms to create and favor a more tumorigenic environment. The bone marrow niche allows for pertinent evasion, either through avoiding immunosurveillance or through direct interaction with the stroma, inducing quiescence and thus drug resistance. Understanding the interaction of the MM stem cell to the microenvironment and the mechanisms utilized by various stem cell-like populations to allow persistence and therapy-resistance can enable for better targeting of this cell population and potential eradication of the disease.

Multifaceted roles of GSK-3 and Wnt/β-catenin in hematopoiesis and leukemogenesis: opportunities for therapeutic intervention

Glycogen synthase kinase-3 (GSK-3) is well documented to participate in a complex array of critical cellular processes. It was initially identified in rat skeletal muscle as a serine/threonine kinase that phosphorylated and inactivated glycogen synthase. This versatile protein is involved in numerous signaling pathways that influence metabolism, embryogenesis, differentiation, migration, cell cycle progression and survival. Recently, GSK-3 has been implicated in leukemia stem cell pathophysiology and may be an appropriate target for its eradication. In this review, we will discuss the roles that GSK-3 plays in hematopoiesis and leukemogenesis as how this pivotal kinase can interact with multiple signaling pathways such as: Wnt/β-catenin, phosphoinositide 3-kinase (PI3K)/phosphatase and tensin homolog (PTEN)/Akt/mammalian target of rapamycin (mTOR), Ras/Raf/MEK/extracellular signal-regulated kinase (ERK), Notch and others. Moreover, we will discuss how targeting GSK-3 and these other pathways can improve leukemia therapy and may overcome therapeutic resistance. In summary, GSK-3 is a crucial regulatory kinase interacting with multiple pathways to control various physiological processes, as well as leukemia stem cells, leukemia progression and therapeutic resistance. GSK-3 and Wnt are clearly intriguing therapeutic targets.

Notch-directed microenvironment reprogramming in myeloma: a single path to multiple outcomes

Multiple myeloma is a deadly hematopoietic malignancy. Despite therapeutic advances such as autologous stem cell transplantation and novel chemotherapeutics, multiple myeloma remains incurable. Multiple myeloma cell localization in the bone marrow and the cross-talk with the bone niche trigger dramatic alterations in the bone marrow microenvironment critical for tumor progression, resistance to therapies and osteolytic bone destruction. It does not surprise that the molecular bases of such fatal interaction are under examination as source of novel potential pharmacological targets. Among these, the Notch family of receptors and ligands has gained growing interest in the recent years because of their early deregulation in multiple myeloma and their ability to affect multiple features of the disease, including tumor cell growth, drug resistance, angiogenesis and bone lesions. This review will explore the evidences of Notch deregulation in multiple myeloma, the state of the art of the currently known roles of its signaling in the fatal interaction between multiple myeloma cells, extracellular matrix and cells in the bone marrow stroma. Finally, we will present recent findings concerning the arguments for or against a therapy addressed to Notch signaling inhibition in the cure of multiple myeloma.

Dll1/Notch activation contributes to bortezomib resistance by upregulating CYP1A1 in multiple myeloma

One of the greatest challenges in multiple myeloma (MM) treatment is to overcome drug resistance. Many pathways are involved including Notch signaling. Notch receptors are expressed by MM cells and Notch ligand Dll1 is present on bone marrow (BM) stromal cells. In this study, we demonstrate that Dll1 can activate Notch signaling mostly through Notch2 receptor and can contribute to drug resistance to bortezomib, both in murine and human MM cells. Blocking the Notch pathway by DAPT (gamma secretase inhibitor) could reverse this effect and increased sensitivity to bortezomib. We describe the upregulation of CYP1A1, a Cytochrome P450 enzyme involved in drug metabolism, as a possible mechanism of Dll1/Notch induced bortezomib resistance. This was confirmed by inhibition experiments using α-Naphthoflavone or CYP1A1-siRNA that resulted in an increased sensitivity to bortezomib. In addition, in vivo data showed that combination treatment of DAPT with bortezomib was able to increase bortezomib sensitivity and prolonged overall survival in the 5T33MM mouse model. Our data provide a potential strategy to overcome bortezomib resistance by Notch inhibition in MM therapy.