Multiple myeloma dell-derived microvesicles are enriched in CD147 expression and enhance tumor cell proliferation

PD-L1 on large extracellular vesicles is a predictive biomarker for therapy response in tissue PD-L1-low and -negative patients with non-small cell lung cancer

Immunotherapy has revolutionized the treatment of patients with non-small cell lung cancer (NSCLC). High expression of tissue PD-L1 (tPD-L1) is currently the only approved biomarker for predicting treatment response. However, even tPD-L1 low (1-49%) and absent (<1%) patients might benefit from immunotherapy but, to date, there is no reliable biomarker, that can predict response in this particular patient subgroup. This study aimed to test whether tumour-associated extracellular vesicles (EVs) could fill this gap. Using NSCLC cell lines, we identified a panel of tumour-related antigens that were enriched on large EVs (lEVs) compared to smaller EVs. The levels of lEVs carrying these antigens were significantly elevated in plasma of NSCLC patients (n = 108) and discriminated them from controls (n = 77). Among the tested antigens, we focused on programmed cell death ligand 1 (PD-L1), which is a well-known direct target for immunotherapy. In plasma lEVs, PD-L1 was mainly found on a population of CD45- /CD62P+ lEVs and thus seemed to be associated with platelet-derived vesicles. Patients with high baseline levels of PD-L1+ lEVs in blood showed a significantly better response to immunotherapy and prolonged survival. This was particularly true in the subgroup of NSCLC patients with low or absent tPD-L1 expression, thus identifying PD-L1-positive lEVs in plasma as a novel predictive and prognostic marker for immunotherapy.

The Role of Extracellular Vesicles in the Pathogenesis of Hematological Malignancies: Interaction with Tumor Microenvironment; a Potential Biomarker and Targeted Therapy

The tumor microenvironment (TME) plays an important role in the development and progression of hematological malignancies. In recent years, studies have focused on understanding how tumor cells communicate within the TME. In addition to several factors, such as growth factors, cytokines, extracellular matrix (ECM) molecules, etc., a growing body of evidence has indicated that extracellular vesicles (EVs) play a crucial role in the communication of tumor cells within the TME, thereby contributing to the pathogenesis of hematological malignancies. The present review focuses on how EVs derived from tumor cells interact with the cells in the TME, such as immune cells, stromal cells, endothelial cells, and ECM components, and vice versa, in the context of various hematological malignancies. EVs recovered from the body fluids of cancer patients often carry the bioactive molecules of the originating cells and hence can be considered new predictive biomarkers for specific types of cancer, thereby also acting as potential therapeutic targets. Here, we discuss how EVs influence hematological tumor progression via tumor-host crosstalk and their use as biomarkers for hematological malignancies, thereby benefiting the development of potential therapeutic targets.

Uptake-Dependent and -Independent Effects of Fibroblasts-Derived Extracellular Vesicles on Bone Marrow Endothelial Cells from Patients with Multiple Myeloma: Therapeutic and Clinical Implications

Extracellular vesicles (EVs) have emerged as important players in cell-to-cell communication within the bone marrow (BM) of multiple myeloma (MM) patients, where they mediate several tumor-associated processes. Here, we investigate the contribution of fibroblasts-derived EVs (FBEVs) in supporting BM angiogenesis. We demonstrate that FBEVs' cargo contains several angiogenic cytokines (i.e., VEGF, HGF, and ANG-1) that promote an early over-angiogenic effect independent from EVs uptake. Interestingly, co-culture of endothelial cells from MM patients (MMECs) with FBEVs for 1 or 6 h activates the VEGF/VEGFR2, HGF/HGFR, and ANG-1/Tie2 axis, as well as the mTORC2 and Wnt/β-catenin pathways, suggesting that the early over-angiogenic effect is a cytokine-mediated process. FBEVs internalization occurs after longer exposure of MMECs to FBEVs (24 h) and induces a late over-angiogenic effect by increasing MMECs migration, chemotaxis, metalloproteases release, and capillarogenesis. FBEVs uptake activates mTORC1, MAPK, SRC, and STAT pathways that promote the release of pro-angiogenic cytokines, further supporting the pro-angiogenic milieu. Overall, our results demonstrate that FBEVs foster MM angiogenesis through dual time-related uptake-independent and uptake-dependent mechanisms that activate different intracellular pathways and transcriptional programs, providing the rationale for designing novel anti-angiogenic strategies.

Extracellular Vesicles in Multiple Myeloma-Cracking the Code to a Better Understanding of the Disease

Multiple myeloma (MM) is a plasma cell-derived malignancy that stands for around 1.5% of newly discovered cancer cases. Despite constantly improving treatment methods, the disease is incurable with over 13,000 deaths in the US and over 30,000 in Europe. Recent studies suggest that extracellular vesicles (EVs) might play a significant role in the pathogenesis and evolution of MM. Further investigation of their role could prove to be beneficial in establishing new therapies and hence, improve the prognosis of MM patients. What is more, EVs might serve as novel markers in diagnosing and monitoring the disease. Great advancements concerning the position of EVs in the pathophysiology of MM have recently been shown in research and in this review, we would like to delve into the still expanding state of knowledge.

Detection of Measurable Residual Disease Biomarkers in Extracellular Vesicles from Liquid Biopsies of Multiple Myeloma Patients-A Proof of Concept

Monitoring measurable residual disease (MRD) is crucial to assess treatment response in Multiple Myeloma (MM). Detection of MRD in peripheral blood (PB) by exploring Extracellular Vesicles (EVs), and their cargo, would allow frequent and minimally invasive monitoring of MM. This work aims to detect biomarkers of MRD in EVs isolated from MM patient samples at diagnosis and remission and compare the MRD-associated content between BM and PB EVs. EVs were isolated by size-exclusion chromatography, concentrated by ultrafiltration, and characterized according to their size and concentration, morphology, protein concentration, and the presence of EV-associated protein markers. EVs from healthy blood donors were used as controls. It was possible to isolate EVs from PB and BM carrying MM markers. Diagnostic samples had different levels of MM markers between PB and BM paired samples, but no differences between PB and BM were found at remission. EVs concentration was lower in the PB of healthy controls than of patients, and MM markers were mostly not detected in EVs from controls. This study pinpoints the potential of PB EVs from MM remission patients as a source of MM biomarkers and as a non-invasive approach for monitoring MRD.

Biology of the Extracellular Proteasome

Proteasomes are traditionally considered intracellular complexes that play a critical role in maintaining proteostasis by degrading short-lived regulatory proteins and removing damaged proteins. Remarkably, in addition to these well-studied intracellular roles, accumulating data indicate that proteasomes are also present in extracellular body fluids. Not much is known about the origin, biological role, mode(s) of regulation or mechanisms of extracellular transport of these complexes. Nevertheless, emerging evidence indicates that the presence of proteasomes in the extracellular milieu is not a random phenomenon, but rather a regulated, coordinated physiological process. In this review, we provide an overview of the current understanding of extracellular proteasomes. To this end, we examine 143 proteomic datasets, leading us to the realization that 20S proteasome subunits are present in at least 25 different body fluids. Our analysis also indicates that while 19S subunits exist in some of those fluids, the dominant proteasome activator in these compartments is the PA28α/β complex. We also elaborate on the positive correlations that have been identified in plasma and extracellular vesicles, between 20S proteasome and activity levels to disease severity and treatment efficacy, suggesting the involvement of this understudied complex in pathophysiology. In addition, we address the considerations and practical experimental methods that should be taken when investigating extracellular proteasomes. Overall, we hope this review will stimulate new opportunities for investigation and thoughtful discussions on this exciting topic that will contribute to the maturation of the field.

Extracellular vesicle proteomic analysis leads to the discovery of HDGF as a new factor in multiple myeloma biology

HDGF is secreted by and found in multiple myeloma cell extracellular vesicles; it activates AKT and sustains multiple myeloma cell growth.

HDGF polarizes naïve macrophages to an M1 phenotype and generates immunosuppressive M-MDSC.

Identifying factors secreted by multiple myeloma (MM) cells that may contribute to MM tumor biology and progression is of the utmost importance. In this study, hepatoma-derived growth factor (HDGF) was identified as a protein present in extracellular vesicles (EVs) released from human MM cell lines (HMCLs). Investigation of the role of HDGF in MM cell biology revealed lower proliferation of HMCLs following HDGF knockdown and AKT phosphorylation following the addition of exogenous HDGF. Metabolic analysis demonstrated that HDGF enhances the already high glycolytic levels of HMCLs and significantly lowers mitochondrial respiration, indicating that HDGF may play a role in myeloma cell survival and/or act in a paracrine manner on cells in the bone marrow (BM) tumor microenvironment (ME). Indeed, HDGF polarizes macrophages to an M1-like phenotype and phenotypically alters naïve CD14⁺ monocytes to resemble myeloid-derived suppressor cells which are functionally suppressive. In summary, HDGF is a novel factor in MM biology and may function to both maintain MM cell viability as well as modify the tumor ME.

Soluble CD147 (BSG) as a Prognostic Marker in Multiple Myeloma

CD147 (basigin, BSG) is a membrane-bound glycoprotein involved in energy metabolism that plays a role in cancer cell survival. Its soluble form is a promising marker of some diseases, but it is otherwise poorly studied. CD147 is overexpressed in multiple myeloma (MM) and is known to affect MM progression, while its genetic variants are associated with MM survival. In the present study, we aimed to assess serum soluble CD147 (sCD147) expression as a potential marker in MM. We found that sCD147 level was higher in MM patients compared to healthy individuals. It was also higher in patients with more advanced disease (ISS III) compared to both patients with less advanced MM and healthy individuals, while its level was observed to drop after positive response to treatment. Patients with high sCD147 were characterized by worse overall survival. sCD147 level did not directly correlate with bone marrow CD147 mRNA expression. In conclusion, this study suggests that serum sCD147 may be a prognostic marker in MM.

Tumor-derived extracellular vesicles: Potential tool for cancer diagnosis, prognosis, and therapy

Various types of cancer pose a notable threat to human health globally. To date, many researchers have undertaken the search for anticancer therapies. However, many anticancer therapeutic approaches accompany many undesirable hazards. In this respect, extracellular vesicles as a whole gained excessive attention from the research community owing to their remarkable potential for delivery of anticancer agents since they are involved in distal intercellular communication via biological cargoes. With the discovery of the fact that tumor cells discharge huge quantities of EVs, new insights have been developed in cancer diagnosis and treatment. Tumor-derived extracellular vesicles (TD-EVs) can be distinguished from the normal cell-derived EVs due to the presence of specific labels on their surface. TD-EVs carry specific oncogenic proteins and the nucleic acids on their surface membrane that participate in tumor progression. Moreover, the proportion of these nucleic acids and the protein greatly varies among malignant and healthy cell-derived EVs. The diagnostic potential of TD-EVs can be implied for the more precise and early-stage detection of cancer that was impossible in the past. This review examines the recent progress in prognostic, diagnostic, and therapeutic potential of the EVs derived from the tumor cells.

Exosomal tumor necrosis factor-α from hepatocellular cancer cells (Huh-7) promote osteoclast differentiation

Bone is the common extra-hepatic site for cancer metastasis. Hepatic cancer is associated with a higher incidence of pathological fracture. However, this important regulatory mechanism remains unexplored. Thus, exosome-mediated cell-cell communication between hepatocellular cancer and bone might be key to osteolytic bone destruction. Huh-7 exosomes were characterized for size and exosome marker expressions (CD63, Alix). Exosome mediated osteoclast differentiation in the RAW 264.7 cells was monitored from day 1 to 6 and multinucleated osteoclast formation and bone resorption activity were analyzed. The osteoclastogenic factor expressions in the exosomes and osteoclast differentiation markers such as tumor necrosis factor receptor 6 (TRAF6), nuclear factor κB (NF-κB), nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), and cathepsin K (CTSK) were analyzed using western blot. Exosomes released by liver cancer cells (Huh-7) promoted osteoclast differentiation in RAW 264.7 cells. Analysis of osteoclastogenic factors in the exosomes showed that exosomes were specifically enriched with tumor necrosis factor α (TNF-α). Huh-7 exosomes promoted osteoclast differentiation by significantly increasing the number of TRAP-positive multi nucleated osteoclasts and resorption pits. Importantly, exosomes upregulated osteoclast markers TRAF6, NF-κB, and CTSK expressions. Further, neutralizing exosomal TNF-α reverted exosome-mediated osteoclast differentiation in RAW 264.7 cells. Collectively, our findings show that cellular communication of exosomal TNF-α from hepatocellular cancer cells (Huh-7) regulates osteoclast differentiation through NF-κB/CTSK/TRAP expressions. Thus, exosomal TNF-α might act as an important therapeutic target to prevent hepatocellular cancer mediated pathological bone disease.

Specificities of exosome versus small ectosome secretion revealed by live intracellular tracking of CD63 and CD9

Despite their roles in intercellular communications, the different populations of extracellular vesicles (EVs) and their secretion mechanisms are not fully characterized: how and to what extent EVs form as intraluminal vesicles of endocytic compartments (exosomes), or at the plasma membrane (PM) (ectosomes) remains unclear. Here we follow intracellular trafficking of the EV markers CD9 and CD63 from the endoplasmic reticulum to their residency compartment, respectively PM and late endosomes. We observe transient co-localization at both places, before they finally segregate. CD9 and a mutant CD63 stabilized at the PM are more abundantly released in EVs than CD63. Thus, in HeLa cells, ectosomes are more prominent than exosomes. By comparative proteomic analysis and differential response to neutralization of endosomal pH, we identify a few surface proteins likely specific of either exosomes (LAMP1) or ectosomes (BSG, SLC3A2). Our work sets the path for molecular and functional discrimination of exosomes and small ectosomes in any cell type.

Extracellular vesicles (EVs) play a role in intercellular communication, however the precise biogenesis of different populations of EVs are not clear. Here, the authors follow the intracellular trafficking of two proteins before their secretion in EVs and report the biogenesis and protein markers of EV subtypes: ectosomes budding from the plasma membrane as well as exosomes from late endosomes.

Activated fibroblasts enhance cancer cell migration by microvesicles-mediated transfer of Galectin-1

Cancer-associated fibroblasts (CAFs) are one of the main components of the stromal compartment in the tumor microenvironment (TME) and the crosstalk between CAFs and cancer cells is essential for tumor progression and aggressiveness. Cancer cells mediate an activation process, converting normal fibroblasts into CAFs, that are characterized by modified expression of many proteins and increased production and release of microvesicles (MVs), extracellular vesicles generated by outwards budding from the cell membrane. Recent evidence underlined that the uptake of CAF-derived MVs changes the overall protein content of tumor cells. In this paper, we demonstrate that tumor activated fibroblasts overexpress Galectin-1 (Gal-1) and consequently release MVs containing increased levels of this protein. The uptake of Gal-1 enriched MVs by tumor cells leads to the upregulation of its intracellular concentration, that strongly affects cancer cell migration, while neither proliferation nor adhesion are altered. Accordingly, tumor cells co-cultured with fibroblasts silenced for Gal-1 have a reduced migratory ability. The present work reveals the key role of an exogenous protein, Gal-1, derived from activated fibroblasts, in cancer progression, and contributes to clarify the importance of MVs-mediated protein trafficking in regulating tumor-stroma crosstalk.

The "Vesicular Intelligence" Strategy of Blood Cancers

Blood cancers are a heterogeneous group of disorders including leukemia, multiple myeloma, and lymphoma. They may derive from the clonal evolution of the hemopoietic stem cell compartment or from the transformation of progenitors with immune potential. Extracellular vesicles (EVs) are membrane-bound nanovesicles which are released by cells into body fluids with a role in intercellular communication in physiology and pathology, including cancer. EV cargos are enriched in nucleic acids, proteins, and lipids, and these molecules can be delivered to target cells to influence their biological properties and modify surrounding or distant targets. In this review, we will describe the “smart strategy” on how blood cancer-derived EVs modulate tumor cell development and maintenance. Moreover, we will also depict the function of microenvironment-derived EVs in blood cancers and discuss how the interplay between tumor and microenvironment affects blood cancer cell growth and spreading, immune response, angiogenesis, thrombogenicity, and drug resistance. The potential of EVs as non-invasive biomarkers will be also discussed. Lastly, we discuss the clinical application viewpoint of EVs in blood cancers. Overall, blood cancers apply a ‘vesicular intelligence’ strategy to spread signals over their microenvironment, promoting the development and/or maintenance of the malignant clone.

Potential Role of microRNAs in inducing Drug Resistance in Patients with Multiple Myeloma

The prognosis for newly diagnosed subjects with multiple myeloma (MM) has significantly progressed in recent years. However, most MM patients relapse and after several salvage therapies, the onset of multidrug resistance provokes the occurrence of a refractory disease. A continuous and bidirectional exchange of information takes place between the cells of the microenvironment and neoplastic cells to solicit the demands of cancer cells. Among the molecules serving as messengers, there are microRNAs (miRNA), a family of small noncoding RNAs that regulate gene expression. Numerous miRNAs are associated with drug resistance, also in MM, and the modulation of their expression or activity might be explored to reverse it. In this review we report the most recent studies concerning the relationship between miRNAs and chemoresistance to the most frequently used drugs, such as proteasome inhibitors, steroids, alkylating agents and immunomodulators. The experimental use of antagomirs or miRNA mimics have successfully been proven to counteract chemoresistance and display synergistic effects with antimyeloma drugs which could represent a fundamental moment to overcome resistance in MM treatment.

Extracellular vesicles (EVs): What we know of the mesmerizing roles of these tiny vesicles in hematological malignancies?

Cancer is a complex disease in which a bidirectional collaboration between malignant cells and surrounding microenvironment creates an appropriate platform which ultimately facilitates the progression of the disease. The discovery of extracellular vesicles (EVs) was a turning point in the modern era of cancer biology, as their importance in human malignancies has set the stage to widen research interest in the field of cell-to-cell communication. The implication in short- and long-distance interaction via horizontally transfer of cellular components, ranging from non-coding RNAs to functional proteins, as well as stimulating target cells receptors by the means of ligands anchored on their membrane endows these "tiny vesicles with giant impacts" with incredible potential to re-educate normal tissues, and thus, to re-shape the surrounding niche. In this review, we highlight the pathogenic roles of EVs in human cancers, with an extensive focus on the recent advances in hematological malignancies.

High-throughput analysis and functional interpretation of extracellular vesicle content in hematological malignancies

Extracellular vesicles (EVs) are membrane-coated particles secreted by virtually all cell types in response to different stimuli, both in physiological and pathological conditions. Their content generally reflects their biological functions and includes a variety of molecules, such as nucleic acids, proteins and cellular components. The role of EVs as signaling vehicles has been widely demonstrated. In particular, they are actively involved in the pathogenesis of several hematological malignancies (HM), mainly interacting with a number of target cells and inducing functional and epigenetic changes. In this regard, by releasing their cargo, EVs play a pivotal role in the bilateral cross-talk between tumor microenvironment and cancer cells, thus facilitating mechanisms of immune escape and supporting tumor growth and progression. Recent advances in high-throughput technologies have allowed the deep characterization and functional interpretation of EV content. In this review, the current knowledge on the high-throughput technology-based characterization of EV cargo in HM is summarized.

Long-chain polyunsaturated omega-3 fatty acids reduce multiple myeloma exosome-mediated suppression of NK cell cytotoxicity

BACKGROUND

Despite the advances in the treatment of multiple myeloma (MM), complete remission is usually challenging. The interactions between tumor and host cells, in which exosomes (EXs) play critical roles, have been shown to be among the major deteriorative tumor-promoting factors herein. Therefore, any endeavor to beneficially target these EX-mediated interactions could be of high importance.

OBJECTIVES

a) To investigate the effects of myeloma EXs on natural killer (NK) cell functions. b) To check whether treatment of myeloma cells with eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA), two polyunsaturated omega-3 fatty acids with known anti-cancer effects, can modify myeloma EXs in terms of their effects on natural killer functions.

METHODS

L363 cells were treated with either EPA or DHA or left untreated and the released EXs (designated as E-EX, D-EX and C-EX, respectively) were used to treat NK cells for functional studies.

RESULTS

Myeloma EXs (C-EXs) significantly reduced NK cytotoxicity against K562 cells (P ≤ 0.05), while the cytotoxicity suppression was significantly lower (P ≤ 0.05) in the (E-EX)- and (D-EX)-treated NK cells compared to the (C-EX)-treated cells. The expression of the activating NK receptor NKG2D and NK degranulation, after treatment with the EXs, were both altered following the same pattern. However, C-EXs could increase IFN-γ production in NK cells (P < 0.01), which was not significantly affected by EPA/DHA treatment. This indicates a dual effect of myeloma EXs on NK cells functions.

CONCLUSION

Our observations showed that myeloma EXs have both suppressive and stimulatory effects on different NK functions. Treatment of myeloma cells with EPA/DHA can reduce the suppressive effects of myeloma EXs while maintaining their stimulatory effects. These findings, together with the previous findings on the anti-cancer effects of EPA/DHA, provide stronger evidence for the repositioning of the currently existing EPA/DHA supplements to be used in the treatment of MM as an adjuvant treatment. EXs released from L363 (myeloma) cells in their steady state increase IFN-γ production of NK cells, while reduce their cytotoxicity against the K562 cell line (right blue trace). EXs from L363 cells pre-treated with either EPA or DHA are weaker stimulators of IFN-γ production. These EXs also increase NK cytotoxicity and NKG2D expression (left brown trace) compared to the EXs obtained from untreated L363 cells. Based on these findings, myeloma EXs have both suppressive and stimulatory effects on different NK functions depending on the properties of their cells of origin, which can be exploited in the treatment of myeloma.

Microvesicles in Cancer: Small Size, Large Potential

Extracellular vesicles (EV) are secreted by all cell types in a tumor and its microenvironment (TME), playing an essential role in intercellular communication and the establishment of a TME favorable for tumor invasion and metastasis. They encompass a variety of vesicle populations, among them the well-known endosomal-derived small exosomes (Exo), but also larger vesicles (diameter > 100 nm) that are shed directly from the plasma membrane, the so-called microvesicles (MV). Increasing evidence suggests that MV, although biologically different, share the tumor-promoting features of Exo in the TME. Due to their larger size, they can be readily harvested from patients' blood and characterized by routine methods such as conventional flow cytometry, exploiting the plethora of molecules expressed on their surface. In this review, we summarize the current knowledge about the biology and the composition of MV, as well as their role within the TME. We highlight not only the challenges and potential of MV as novel biomarkers for cancer, but also discuss their possible use for therapeutic intervention.

Thyroid tumor cells-fibroblasts crosstalk: role of extracellular vesicles

Tumor-stroma crosstalk leads to a tumor-promoting microenvironment. In this milieu, extracellular vesicles (EVs) are protagonists in cell-cell communication. Despite thyroid cancer being the most common endocrine malignancy, the contribution of the tumor microenvironment to thyroid cancer progression is still largely underexplored. We focused on the role of thyroid tumor cell-fibroblast interaction and EVs as mediators of tumor-stroma interplay, in the promotion of thyroid tumor aggressiveness. Thyroid tumor (TPC-1, 8505c) or non-tumor thyroid cells (NThyOri) were co-cultured with human fibroblasts (Fb). Thyroid cell migration was investigated by the wound-healing assay and actin-network staining. Cell-CD147 expression was characterized by flow cytometry. EVs, obtained by ultracentrifugation of conditioned media (CMs), were characterized by transmission electron-microscopy and CD81 and CD147 expression. Metalloproteinases (MMPs) were evaluated by zymography in CMs. A migratory phenotype was triggered in thyroid tumor cells treated with CMs from Fb or from Fb-thyroid tumor cell co-cultures. Fb-thyroid cell co-cultures induced the secretion of proMMP9 and proMMP2 and led to a significant MMP2 activation in CMs. Fb, thyroid cells and Fb-thyroid cell co-cultures released EVs, and remarkably, EVs released by Fb-thyroid tumor cell co-cultures induced the secretion of proMMP2 and the expression of MMP2 from normal Fb. A significant CD147 expression was demonstrated in Fb-thyroid tumor cell-derived EVs. These findings reveal the role of Fb and thyroid tumor cell-Fb interaction in the promotion of a microenvironment suitable for thyroid tumor progression. Moreover, they highlight, for the first time, the role of thyroid tumor cell-Fb interaction in the production of specialized EVs.

Extracellular Vesicles After Allogeneic Hematopoietic Cell Transplantation: Emerging Role in Post-Transplant Complications

Extracellular vesicles (EVs) play an important role in the cellular crosstalk by transferring bioactive molecules through biological barriers from a cell to another, thus influencing recipient cell functions and phenotype. Therefore, EVs are increasingly being explored as biomarkers of disease progression or response to therapy and as potential therapeutic agents in different contexts including in hematological malignancies. Recently, an EV role has emerged in allogeneic hematopoietic cell transplantation (allo-HCT) as well. Allogeneic hematopoietic cell transplantation often represents the only curative option in several hematological disorders, but it is associated with potentially life-threatening complications that can have a significant impact on clinical outcomes. The most common complications have been well-established and include graft-versus-host disease and infections. Furthermore, relapse remains an important cause of treatment failure. The aim of this review is to summarize the current knowledge, the potential applications, and clinical relevance of EVs in allo-HCT. Herein, we will mainly focus on the immune-modulating properties of EVs, in particular those derived from mesenchymal stromal cells, as potential therapeutic strategy to improve allo-HCT outcome. Moreover, we will briefly describe the main findings on EVs as biomarkers to monitor graft-versus-host disease onset and tumor relapse.

Extracellular Vesicle microRNAs Contribute to the Osteogenic Inhibition of Mesenchymal Stem Cells in Multiple Myeloma

Osteolytic bone disease is the major complication associated with the progression of multiple myeloma (MM). Recently, extracellular vesicles (EVs) have emerged as mediators of MM-associated bone disease by inhibiting the osteogenic differentiation of human mesenchymal stem cells (hMSCs). Here, we investigated a correlation between the EV-mediated osteogenic inhibition and MM vesicle content, focusing on miRNAs. By the use of a MicroRNA Card, we identified a pool of miRNAs, highly expressed in EVs, from MM cell line (MM1.S EVs), expression of which was confirmed in EVs from bone marrow (BM) plasma of patients affected by smoldering myeloma (SMM) and MM. Notably, we found that miR-129-5p, which targets different osteoblast (OBs) differentiation markers, is enriched in MM-EVs compared to SMM-EVs, thus suggesting a selective packaging correlated with pathological grade. We found that miR-129-5p can be transported to hMSCs by MM-EVs and, by the use of miRNA mimics, we investigated its role in recipient cells. Our data demonstrated that the increase of miR-129-5p levels in hMSCs under osteoblastic differentiation stimuli inhibited the expression of the transcription factor Sp1, previously described as a positive modulator of osteoblastic differentiation, and of its target the Alkaline phosphatase (ALPL), thus identifying miR-129-5p among the players of vesicle-mediated bone disease.

MicroRNAs and exosomes: Small molecules with big actions in multiple myeloma pathogenesis

Multiple myeloma (MM), an incurable hematologic malignancy of plasma cells increasing in the bone marrow (BM), has a complex microenvironment made to support proliferation, survival, and drug resistance of tumor cells. MicroRNAs (miRNAs), short non-coding RNAs regulating genes expression at posttranscriptional level, have been indicated to be functionally deregulated or abnormally expressed in MM cells. Moreover, by means of miRNAs, tumor microenvironment also modulates the function of MM cells. Consistently, it has been demonstrated that miRNA levels regulation impairs their interaction with the microenvironment of BM as well as create considerable antitumor feature even capable of overcoming the protective BM milieu. Communication between cancer stromal cells and cancer cells is a key factor in tumor progression. Finding out this interaction is important to develop effective approaches that reverse bone diseases. Exosomes, nano-vehicles having crucial roles in cell-to-cell communication, through targeting their cargos (i.e., miRNAs, mRNAs, DNAs, and proteins), are implicated in MM pathogenesis.

Multiple myeloma-derived exosomes inhibit osteoblastic differentiation and improve IL-6 secretion of BMSCs from multiple myeloma

Bone marrow stromal cells (BMSCs) play a critical role in multiple myeloma (MM) pathogenesis by cell contact, and secretion of cytokines, growth factors and extracellular vesicles. Exosomes are secreted by almost all cell types and are recently reported to mediate local cell-to-cell cross-talk by transferring messenger RNAs, LncRNAs, and proteins. Compelling studies have identified BMSC-derived exosomes induce proliferation, migration, survival, and drug resistance of MM cells. However, whether MM cell-derived exosome also plays a role in function in BMSC remains unclear. Here we investigated the effect of MM cell-derived exosomes on the interleukin (IL)-6 secretion and osteoblastic differentiation capability of BMSC from patients with MM. Furthermore we investigated the IL-6 secretion relative regulation protein APE1 and NF-kB and osteoblastic differentiation protein Runx2 (runt-related gene 2), Osterix and osteocalcin (OCN). Our results showed that MM cell-derived exosomes promoted IL-6 secretion and suppressed osteoblastic differentiation and mineralization of BMSCs. Mechanistically, we demonstrated that MM cell-derived exosomes lead to an increase in APE1 and NF-kB and a reduction in Runx2, Osterix and OCN in BMSCs. Taken together, MM cell-derived exosomes induce the secretion of IL-6 and poor osteoblastic differentiation of BMSCs.

Myeloma-derived extracellular vesicles mediate HGF/c-Met signaling in osteoblast-like cells

Multiple myeloma is an incurable cancer of antibody-producing plasma cells. Hepatocyte growth factor (HGF), a cytokine aberrantly expressed in half of myeloma patients, is involved in myeloma pathogenesis by enhancing myeloma growth and invasiveness, and may play a role in myeloma bone disease by inhibiting osteoblastogenesis. In this study, we investigated whether extracellular vesicles (EVs) may play a role in HGF signaling between myeloma cells and osteoblast-like target cells. EVs from the HGF-positive cell line JJN-3 and the HGF-negative cell line INA-6, and from bone marrow plasma and primary human myeloma cells, were isolated using sequential centrifugation techniques and the presence of HGF on the EV-surface was investigated with ELISA. EVs from both cell lines were added to an established bioassay where HGF is known to induce interleukin-11 secretion in osteoblast-like cells. Our results show that HGF was bound to the surface of JJN-3-derived EVs, while INA-6-derived EVs were negative for HGF. Only JJN-3-derived EVs induced IL-11 secretion in osteoblast-like recipient cells. When osteoblast-like cells were preincubated with a specific HGF-receptor (c-Met) inhibitor, no induction of interleukin-11 was observed. Downstream c-Met phosphorylation was demonstrated by immunoblotting. EVs isolated from bone marrow plasma and primary myeloma cells were HGF-positive for a subset of myeloma patients. Taken together, this work shows for the first time that HGF bound on the surface of myeloma-derived EVs can effectuate HGF/c-Met signaling in osteoblast-like cells. Myeloma-derived EVs may play a role in myeloma bone disease by induction of the osteoclast-activating cytokine interleukin-11 in osteoblasts.

Extracellular Vesicles Enhance Multiple Myeloma Metastatic Dissemination

Extracellular vesicles (EVs) represent a heterogeneous group of membranous structures shed by all kinds of cell types, which are released into the surrounding microenvironment or spread to distant sites through the circulation. Therefore, EVs are key mediators of the communication between tumor cells and the surrounding microenvironment or the distant premetastatic niche due to their ability to transport lipids, transcription factors, mRNAs, non-coding regulatory RNAs, and proteins. Multiple myeloma (MM) is a hematological neoplasm that mostly relies on the bone marrow (BM). The BM represents a highly supportive niche for myeloma establishment and diffusion during the formation of distant bone lesions typical of this disease. This review represents a survey of the most recent evidence published on the role played by EVs in supporting MM cells during the multiple steps of metastasis, including travel and uptake at distant premetastatic niches, MM cell engraftment as micrometastasis, and expansion to macrometastasis thanks to EV-induced angiogenesis, release of angiocrine factors, activation of osteolytic activity, and mesenchymal cell support. Finally, we illustrate the first evidence concerning the dual effect of MM-EVs in promoting both anti-tumor immunity and MM immune escape, and the possible modulation operated by pharmacological treatments.

Role of tumor‑derived extracellular vesicles in cancer progression and their clinical applications (Review)

Extracellular vesicles (EVs), including micro‑vesicles and exosomes, are heterogeneous small membranous vesicles shed from the surface of myriad cells and are crucial in mediating intercellular communication. The vertical trafficking of cargo to the plasma membrane and subsequent redistribution of surface lipids may contribute to EV formation. Tumor‑derived extracellular vesicles (TD‑EVs) can carry complex, bioactive cargo, such as nucleic acids and proteins, during tumor metastasis. Paracrine information gets relayed by TD‑EVs to adjacent tumor cells and this allows a crosstalk between malignant cells. These structures may even move to a distant metastatic lesion and modulate the tumor microenvironment to form a premetastatic niche. Thus, TD‑EVs might be potential biomarkers for tumor development and metastasis. Additionally, EVs are promising candidates for use as cell‑free vaccines or as vehicles for the delivery of specific tumor therapeutic molecules. Genetically modified microvesicles and engineered exosomes have shed light on a novel strategy for tumor‑targeted gene therapy. This review focuses on the role of EVs in tumor development and metastasis and their possible applications in the advanced diagnosis and therapy of cancer and personalized medicine.

An update on extracellular vesicles in multiple myeloma: a focus on their role in cell-to-cell cross-talk and as potential liquid biopsy biomarkers

INTRODUCTION

Multiple myeloma (MM) is characterized by a clonal proliferation of neoplastic plasma cells (PCs) in bone marrow (BM) and the interplay between MM PCs and the BM microenvironment, which plays a relevant role in its pathogenesis. In this important cross-talk, extracellular vesicles (EVs) are active. EVs, including small and medium/large EVs, are lipid bi-layer particles released in circulation by normal and neoplastic cells. A selected cargo of lipids, proteins, and nucleic acids is loaded into EVs, and delivered locally and to distant sites, thus influencing the physiology of recipient cells. In the 'liquid biopsy' context, EVs can be isolated from human biofluids proving to be powerful markers in cancer. Areas covered: Here, we summarize the recent advances on EVs in MM field. Expert commentary: EVs from MM PCs: i) enhance malignant cell proliferation and aggressiveness through an autocrine loop; ii) are able to transfer drug resistance in sensitive-drug cells; iii) stimulate angiogenesis; iv) increase the activity of osteoclasts; v) have immunosuppressive effects. In addition, EVs from MM stromal cells also promote MM cell proliferation and drug resistance. Finally, we underline the importance of EVs as MM potential biomarkers in 'cancer liquid biopsy' and as a potential new therapeutic target.

Multiple myeloma-derived exosomes are enriched of amphiregulin (AREG) and activate the epidermal growth factor pathway in the bone microenvironment leading to osteoclastogenesis

Background

Multiple myeloma (MM) is a clonal plasma cell malignancy associated with osteolytic bone disease. Recently, the role of MM-derived exosomes in the osteoclastogenesis has been demonstrated although the underlying mechanism is still unknown. Since exosomes-derived epidermal growth factor receptor ligands (EGFR) are involved in tumor-associated osteolysis, we hypothesize that the EGFR ligand amphiregulin (AREG) can be delivered by MM-derived exosomes and participate in MM-induced osteoclastogenesis.

Methods

Exosomes were isolated from the conditioned medium of MM1.S cell line and from bone marrow (BM) plasma samples of MM patients. The murine cell line RAW264.7 and primary human CD14⁺ cells were used as osteoclast (OC) sources.

Results

We found that AREG was specifically enriched in exosomes from MM samples and that exosomes-derived AREG led to the activation of EGFR in pre-OC, as showed by the increase of mRNA expression of its downstream SNAIL in both RAW264.7 and CD14⁺ cells. The presence of neutralizing anti-AREG monoclonal antibody (mAb) reverted this effect. Consequently, we showed that the effect of MM-derived exosomes on osteoclast differentiation was inhibited by the pre-treatment of exosomes with anti-AREG mAb. In addition, we demonstrated the ability of MM-derived AREG-enriched exosomes to be internalized into human mesenchymal stromal cells (MSCs) blocking osteoblast (OB) differentiation, increasing MM cell adhesion and the release of the pro-osteoclastogenic cytokine interleukin-8 (IL8). Accordingly, anti-AREG mAb inhibited the release of IL8 by MSCs suggesting that both direct and indirect effects are responsible for AREG-enriched exosomes involvement on MM-induced osteoclastogenesis.

Conclusions

In conclusion, our data indicate that AREG is packed into MM-derived exosomes and implicated in OC differentiation through an indirect mechanism mediated by OBs.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0689-y) contains supplementary material, which is available to authorized users.

Tumor-derived extracellular vesicles inhibit osteogenesis and exacerbate myeloma bone disease

Background: As a hallmark driver of multiple myeloma (MM), MM bone disease (MBD) is unique in that it is characterized by severely impaired osteoblast activity resulting from blocked osteogenesis in bone marrow-derived mesenchymal stem cells (BM-MSCs). The mechanisms underlying this preferential blockade are incompletely understood.

Methods: miRNA expression of MM cell-derived extracellular vesicles (MM-EVs) was detected by RNA sequencing. MM-EVs impaired osteogenesis and exacerbated MBD were in vitro and in vivo validated by histochemical staining, qPCR and micro-CT. We additionally examined the correlation between CD138⁺ circulating EVs (cirEVs) count and bone lesion in de novo MM patients.

Results: Here, by sequencing and bioinformatics analysis, we found that MM-EVs were enriched in various molecules negatively regulating osteogenesis. We experimentally verified that MM-EVs inhibited BM-MSC osteogenesis, induced elevated expression of miR-103a-3p inhibiting osteogenesis in BM-MSCs, and increased cell viability and interleukin-6 secretion in MM cells. In a mouse model, MM-EVs that were injected into the marrow space of the left tibia led to impaired osteogenesis and exacerbated MBD and MM progression. Furthermore, the levels of CD138⁺ cirEVs in the peripheral blood were positively correlated with the number of MM bone lesions in MM patients.

Conclusions: These findings suggest that MM-EVs play a pivotal role in the development of severely impaired osteoblast activity, which represents a novel biomarker for the precise diagnosis of MBD and a compelling rationale for exploring MM-EVs as a therapeutic target.

Transmembrane Protease TMPRSS11B Promotes Lung Cancer Growth by Enhancing Lactate Export and Glycolytic Metabolism

Pathways underlying metabolic reprogramming in cancer remain incompletely understood. We identify the transmembrane serine protease TMPRSS11B as a gene that promotes transformation of immortalized human bronchial epithelial cells (HBECs). TMPRSS11B is upregulated in human lung squamous cell carcinomas (LSCCs), and high expression is associated with poor survival of non-small cell lung cancer patients. TMPRSS11B inhibition in human LSCCs reduces transformation and tumor growth. Given that TMPRSS11B harbors an extracellular (EC) protease domain, we hypothesized that catalysis of a membrane-bound substrate modulates tumor progression. Interrogation of a set of soluble receptors revealed that TMPRSS11B promotes solubilization of Basigin, an obligate chaperone of the lactate monocarboxylate transporter MCT4. Basigin release mediated by TMPRSS11B enhances lactate export and glycolytic metabolism, thereby promoting tumorigenesis. These findings establish an oncogenic role for TMPRSS11B and provide support for the development of therapies that target this enzyme at the surface of cancer cells.

Extracellular vesicles of multiple myeloma cells utilize the proteasome inhibitor mechanism to moderate endothelial angiogenesis

Bone marrow microenvironment is known to support angiogenesis, thus contributing to progression of multiple myeloma (MM). Bortezomib, a proteasome inhibitor (PI) widely used in MM treatment, has anti-angiogenic activity. Extracellular vesicles (EVs), shedding from cell surface, serve as mediators in cell-to-cell communication. We have hypothesized that MM cells (MMCs) treated with bortezomib generate EVs that could diminish angiogenesis, thus limiting MM progression. In the present study, EVs were obtained from MMCs (RPMI-8226), untreated (naïve) or pre-treated with bortezomib. EVs were outlined using NanoSight, FACS, protein arrays and proteasome activity assays. The impact of MMC-EVs on endothelial cell (EC) functions was assessed, employing XTT assay, Boyden chamber and Western blot. A high apoptosis level (annexin V binding 70.25 ± 16.37%) was observed in MMCs following exposure to bortezomib. Compared to naïve EVs, a large proportion of bortezomib-induced EVs (Bi-EVs) were bigger in size (> 300 nm), with higher levels of annexin V binding (p = 0.0043).They also differed in content, presenting with increased levels of pro-inflammatory proteins, reduced levels of pro-angiogenic growth factors (VEGFA, PDGF-BB, angiogenin), and displayed lower proteasome activity. Naïve EVs were found to promote EC migration and proliferation via ERK1/2 and JNK1/2/3 phosphorylation, whereas Bi-EVs inhibited these functions. Moreover, Bi-EVs appeared to reduce EC proteasome activity. EVs released from apoptotic MMCs following treatment with bortezomib can promote angiogenesis suppression by decreasing proliferation and migration of EC. These activities are found to be mediated by specific signal transduction pathways.

Daratumumab induces CD38 internalization and impairs myeloma cell adhesion

Daratumumab (Dara), a human immunoglobulin G1 kappa (IgG1κ) monoclonal anti-CD38 antibody, has been approved by the U.S. Food and Drug Administration for the treatment of relapsed multiple myeloma (MM) as a single agent as well as in combination with immunomodulatory drugs (IMiDs) and proteasome inhibitors (PI). Although the scientific rationale behind the use of Dara in combination with IMiDs has been extensively explored, the molecular mechanisms underlying Dara-PI regimens have not yet been investigated. Here, we demonstrate that CD38 on the surface of MM cells is rapidly internalized after Dara treatment; we also show that Dara treatment impairs MM cell adhesion, an effect that can be rescued by using the endocytosis inhibitor Dynasore. Finally, we show that Dara potentiates bortezomib (BTZ) killing of MM cells in vitro and in vivo, independent of its function as an immune activator. In conclusion, our data show that Dara impairs MM cell adhesion, which results in an increased sensitivity of MM to proteasome inhibition.

New role of hypoxia in pathophysiology of multiple myeloma through miR-210

Bone is one of the most common sites of complication in multiple myeloma (MM) progression and bone remodeling gets definitively perturbed during disease progression. Hypoxia and miR-210 play an important role in hematological malignancies. In an attempt to elucidate the specificity of the pathways of hypoxia and miR-210 in suppression of osteoblastic differentiation in MM patients, we examined the effect of miR-210 and hypoxia on expression of important cytokines and genes of myeloma cells. Differentiation of BM-MSCs towards osteoblastic cells in response to microvesicles (MVs) was also investigated. Finally, we proposed a molecular model on how HIF-1α may promote bone lesions in MM patients. To validate the effect of miR-210 and HIF-1α on targeted genes, the shRNA of HIF-1α and off-hsa-miR-210 were transfected into RPMI-8226 cells. BM-MSCs were cultured in osteoblastic inducer and 50 µg/mL of MVs derived from both hypoxic and normoxic myeloma cells. We designed an in vitro study to establish the effects of HIF-1α and miR-210 on the crosstalk between MM and osteoblasts. We here showed that hypoxia-induced miR-210 increased the mRNA expression of VLA-4, CXCR4, IL-6 and TGF-β in myeloma cells. MiR-210 is mandatory for the hypoxia-increased resistance of MM cells to melphalan. Moreover, MVs derived from hypoxic myeloma cells substantially decreased osteoblast differentiation. Considered comprehensively, our findings explain one of the reasons of bone loss that occurs at the sites of MM and a nascent crosstalk model in MM pathogenesis.

Extracellular vesicle-mediated cell-cell communication in haematological neoplasms

Crosstalk between bone marrow tumour cells and surrounding cells, including bone marrow mesenchymal stromal cells (BM-MSCs), endothelial cells and immune cells, is important for tumour growth in haematological neoplasms. In addition to conventional signalling pathways, extracellular vesicles (EVs), which are endosome-derived vesicles containing proteins, mRNAs, lipids and miRNAs, can facilitate modulation of the bone marrow microenvironment without directly contacting non-tumourous cells. In this review, we discuss the current understanding of EV-mediated cell-cell communication in haematological neoplasms, particularly leukaemia and multiple myeloma. We highlight the actions of tumour and BM-MSC EVs in multiple myeloma. The origin of EVs, their tropism and mechanism of EV transfer are emerging issues that need to be addressed in EV-mediated cell-cell communication in haematological neoplasms.This article is part of the discussion meeting issue 'Extracellular vesicles and the tumour microenvironment'.

Extracellular Vesicles: A New Prospective in Crosstalk between Microenvironment and Stem Cells in Hematological Malignancies

The bone marrow (BM) microenvironment in hematological malignancies (HMs) comprises heterogeneous populations of neoplastic and nonneoplastic cells. Cancer stem cells (CSCs), neoplastic cells, hematopoietic stem cells (HSCs), and mesenchymal stromal/stem cells (MSCs) are all components of this microenvironment. CSCs are the HM initiators and are associated with neoplastic growth and drug resistance, while HSCs are able to reconstitute the entire hematopoietic system; finally, MSCs actively support hematopoiesis. In some HMs, CSCs and neoplastic cells compromise the normal development of HSCs and perturb BM-MSCs. In response, "reprogrammed" MSCs generate a favorable environment to support neoplastic cells. Extracellular vesicles (EVs) are an important cell-to-cell communication type in physiological and pathological conditions. In particular, in HMs, EV secretion participates to unidirectional and bidirectional interactions between neoplastic cells and BM cells. The transfer of EV molecular cargo triggers different responses in target cells; in particular, malignant EVs modify the BM environment in favor of neoplastic cells at the expense of normal HSCs, by interfering with antineoplastic immunity and participating in resistance to treatment. Here, we review the role of EVs in BM cell communication in physiological conditions and in HMs, focusing on the effects of BM niche EVs on HSCs and MSCs.

Microvesicles released from multiple myeloma cells are equipped with ectoenzymes belonging to canonical and non-canonical adenosinergic pathways and produce adenosine from ATP and NAD. Oncoimmunology 2018;7:e1458809. [PMID: 30221054 DOI: 10.1080/2162402x.2018.1458809]

Multiple myeloma (MM) derives from malignant transformation of plasma cells (PC), which accumulate in the bone marrow (BM), where microenvironment supports tumor growth and inhibits anti-tumor immune responses. Adenosine (ADO), an immunosuppressive molecule, is produced within MM patients' BM by adenosinergic ectoenzymes, starting from ATP (CD39/CD73) or NAD⁺ [CD38/CD203a(PC-1)/CD73]. These ectoenzymes form a discontinuous network expressed by different BM cells. We investigated the expression and function of ectoenzymes on microvesicles (MVs) isolated from BM plasma samples of patients with MM, using asymptomatic forms of monoclonal gammopathy of undetermined significance (MGUS) and smoldering MM (SMM) as controls. The percentage of MVs expressing ectoenzymes at high levels was higher when derived from MM patients than controls. BM CD138⁺ PC from MM patients expressed high levels of all ectoenzymes. Paired MVs samples confirmed a higher percentage of MVs with high ectoenzymes expression in MM patients than controls. Pooled MVs from MM patients or controls were tested for ADO production. The catabolism of ATP, NAD⁺, ADPR and AMP to ADO was higher in MVs from MM patients than in those from controls. In conclusion, our results confirmed the hypothesis that MVs in MM niche are main contributor of ADO production. The ability of MVs to reach biological fluids strongly support the view that MVs may assume diagnostic and pathogenetic roles.

Extracellular vesicle cross-talk in the bone marrow microenvironment: implications in multiple myeloma

The bone marrow (BM) represents a complex microenvironment containing stromal cells, immune cells, osteoclasts, osteoblasts, and hematopoietic cells, which are crucial for the immune response, bone formation, and hematopoiesis. Apart from soluble factors and direct cell-cell contact, extracellular vesicles (EVs), including exosomes, were recently identified as a third mediator for cell communication. Solid evidence has already demonstrated the involvement of various BM-derived cells and soluble factors in the regulation of multiple biological processes whereas the EV-mediated message delivery system from the BM has just been explored in recent decades. These EVs not only perform physiological functions but can also play a role in cancer development, including in Multiple Myeloma (MM) which is a plasma cell malignancy predominantly localized in the BM. This review will therefore focus on the multiple functions of EVs derived from BM cells, the manipulation of the BM by cancer-derived EVs, and the role of BM EVs in MM progression.

Procoagulant and immunogenic properties of melanoma exosomes, microvesicles and apoptotic vesicles

Extracellular vesicles (EV) are lipid particles released from eukaryotic cells into the extracellular fluid. Depending on the cell type or mechanism of release, vesicles vary in form and function and exert distinct functions in coagulation and immunity. Tumor cells may constitutively shed vesicles known as exosomes or microvesicles (MV). Alternatively, apoptosis induces the release of apoptotic blebs or vesicles (ApoV) from the plasma membrane. EV have been implicated in thrombotic events (the second highest cause of death in cancer patients) and tumor vesicles contribute to the anti-cancer immune response. In this study, we utilized the well characterized B16 melanoma model to determine the molecular composition and procoagulant and immunogenic potential of exosomes, MV and ApoV. Distinct patterns of surface and cytoplasmic molecules (tetraspanins, integrins, heat shock proteins and histones) were expressed between the vesicle types. Moreover, in vitro coagulation assays revealed that membrane-derived vesicles, namely MV and ApoV, were more procoagulant than exosomes–with tissue factor and phosphatidylserine critical for procoagulant activity. Mice immunized with antigen-pulsed ApoV and challenged with B16 tumors were protected out to 60 days, while lower protection rates were afforded by MV and exosomes. Together the results demonstrate distinct phenotypic and functional differences between vesicle types, with important procoagulant and immunogenic functions emerging for membrane-derived MV and ApoV versus endosome-derived exosomes. This study highlights the potential of EV to contribute to the prothrombotic state, as well as to anti-cancer immunity.

Extracellular Vesicles in Hematological Malignancies: From Biology to Therapy

Extracellular vesicles (EVs) are a heterogeneous group of particles, between 15 nanometers and 10 microns in diameter, released by almost all cell types in physiological and pathological conditions, including tumors. EVs have recently emerged as particularly interesting informative vehicles, so that they could be considered a true "cell biopsy". Indeed, EV cargo, including proteins, lipids, and nucleic acids, generally reflects the nature and status of the origin cells. In some cases, EVs are enriched of peculiar molecular cargo, thus suggesting at least a degree of specific cellular packaging. EVs are identified as important and critical players in intercellular communications in short and long distance interplays. Here, we examine the physiological role of EVs and their activity in cross-talk between bone marrow microenvironment and neoplastic cells in hematological malignancies (HMs). In these diseases, HM EVs can modify tumor and bone marrow microenvironment, making the latter "stronger" in supporting malignancy, inducing drug resistance, and suppressing the immune system. Moreover, EVs are abundant in biologic fluids and protect their molecular cargo against degradation. For these and other "natural" characteristics, EVs could be potential biomarkers in a context of HM liquid biopsy and therapeutic tools. These aspects will be also analyzed in this review.

Roles and Modalities of Ectonucleotidases in Remodeling the Multiple Myeloma Niche

Ectoenzymes are cell surface molecules, which represent functional bridges between the environment and the cytoplasm. One set of ectoenzymes—CD39, CD38, CD203a, and CD73—leads to the generation of adenosine (ADO) by metabolizing ATP and NAD⁺. While ADO is known to control inflammation and suppress immune responses, other aspects of ADO function are still obscure, mainly due to its short half-life in biological fluids. Human multiple myeloma (MM) grows in the closed system of the bone marrow (BM) niche representing an ideal setting for studying ectoenzymes and their products. Another source of information on ectoenzyme function may derive from in vivo results of anti-CD38 antibody therapy in MM. Current results, obtained from in vitro models and from preliminary in vivo findings, indicate that ectoenzymes produce ADO locally in the BM niche. Furthermore, MM cells release microvesicles (MV), which thanks to their molecular cargo and surface ectoenzymes may function as particulate communicators outside of the niche. During anti-CD38 antibody therapy, the MV carry therapeutic IgG, determining that the prevalent orientation of MV will be toward cells and tissues expressing receptors for the IgG Fc domain. The resulting picture is one where MM adopts an immune escape strategy based on reshaping the environmental niche. This adaptation is followed by actions of MV that are exerted in biological fluids and circulating immune cells. By coating FcRs⁺ cells, MV modify pericellular spaces, reproducing the metabolic halo generated by ectoenzymes within closed systems.

Extracellular vesicles and blood diseases

Extracellular vesicles (EVs) are small membrane vesicles released from many different cell types by the exocytic budding of the plasma membrane in response to cellular activation or apoptosis. EVs disseminate various bioactive effectors originating from the parent cells and transfer functional RNA and protein between cells, enabling them to alter vascular function and induce biological responses involved in vascular homeostasis. Although most EVs in human blood originate from platelets, EVs are also released from leukocytes, erythrocytes, endothelial cells, smooth muscle cells, and cancer cells. EVs were initially thought to be small particles with procoagulant activity; however, they can also evoke cellular responses in the immediate microenvironments and transport microRNAs (miRNA) into target cells. In this review, we summarize the recent literature relevant to EVs, including a growing list of clinical disorders that are associated with elevated EV levels. These studies suggest that EVs play roles in various blood diseases.

Biology and biogenesis of shed microvesicles

The ability of cells to transmit bioactive molecules to recipient cells and the extracellular environment is a fundamental requirement for both normal physiology and disease pathogenesis. It has traditionally been thought that soluble factors released from cells were responsible for this cellular signaling but recent research has revealed a fundamental role for microvesicles in this process. Microvesicles are heterogeneous membrane-bound sacs that are shed from the surface of cells into the extracellular environment in a highly regulated process. They are shed following the selective incorporation of a host of molecular cargo including multiple types of proteins and nucleic acids. In addition to providing new insight into the etiology of complex human diseases, microvesicles also show great promise as a tool for advanced diagnosis and therapy as we move forward into a new age of personalized medicine. Here we review current status of the rapidly evolving field of microvesicle biology, highlighting critical regulatory roles for several small GTPases in the biology and biogenesis of shed microvesicles.

Hepatic sinusoids in liver injury, inflammation, and fibrosis: new pathophysiological insights

Changes of hepatic sinusoids are crucial in the pathogenesis of liver cirrhosis and portal hypertension. Liver injury leads to distinct morphological abnormalities such as loss of sinusoidal fenestration, vasoconstriction, and angiogenesis as well as molecular changes. Communication between the two key cells in this hepatic microenvironment-hepatic stellate cells (HSC) and sinusoidal endothelial cells (SEC)-has been studied for many years and several canonical pathways have been elucidated, such as decreased eNOS activity or increased PDGF and TGF-β production leading to activation and migration of HSC. In recent studies, alternative pathways of intercellular communication in liver diseases have been described such as cell-derived extracellular vesicles called exosomes, which deliver cell compounds to their target cells. Moreover, such extracellular vesicles may link injury to inflammation in alcoholic hepatitis. While inflammation leading to liver fibrosis has been studied in detail, in some circumstances pathways other than the known canonical inflammatory pathways may contribute to hepatic fibrogenesis. For example, in congestive hepatopathy, sinusoidal dilatation and fibrosis have been shown to be mediated by non-inflammatory mechanisms and associated with sinusoidal thrombi. A recently developed murine model further enables experimental studies of this disease entity. Increasing knowledge about these alternative disease pathways in liver injury, inflammation, and fibrosis may reveal possible target molecules for future therapies. This article builds upon a seminar given at the recent 3rd JSGE International Topic Conference in Sendai, Japan, and reviews the areas outlined above.

Involvement of multiple myeloma cell-derived exosomes in osteoclast differentiation

Bone disease is the most frequent complication in multiple myeloma (MM) resulting in osteolytic lesions, bone pain, hypercalcemia and renal failure. In MM bone disease the perfect balance between bone-resorbing osteoclasts (OCs) and bone-forming osteoblasts (OBs) activity is lost in favour of OCs, thus resulting in skeletal disorders. Since exosomes have been described for their functional role in cancer progression, we here investigate whether MM cell-derived exosomes may be involved in OCs differentiation. We show that MM cells produce exosomes which are actively internalized by Raw264.7 cell line, a cellular model of osteoclast formation. MM cell-derived exosomes positively modulate pre-osteoclast migration, through the increasing of CXCR4 expression and trigger a survival pathway. MM cell-derived exosomes play a significant pro-differentiative role in murine Raw264.7 cells and human primary osteoclasts, inducing the expression of osteoclast markers such as Cathepsin K (CTSK), Matrix Metalloproteinases 9 (MMP9) and Tartrate-resistant Acid Phosphatase (TRAP). Pre-osteoclast treated with MM cell-derived exosomes differentiate in multinuclear OCs able to excavate authentic resorption lacunae. Similar results were obtained with exosomes derived from MM patient's sera. Our data indicate that MM-exosomes modulate OCs function and differentiation. Further studies are needed to identify the OCs activating factors transported by MM cell-derived exosomes.

Mesenchymal stem cells secretomes' affect multiple myeloma translation initiation

Bone marrow mesenchymal stem cells' (BM-MSCs) role in multiple myeloma (MM) pathogenesis is recognized. Recently, we have published that co-culture of MM cell lines with BM-MSCs results in mutual modulation of phenotype and proteome (via translation initiation (TI) factors eIF4E/eIF4GI) and that there are differences between normal donor BM-MSCs (ND-MSCs) and MM BM-MSCs (MM-MSCs) in this crosstalk. Here, we aimed to assess the involvement of soluble BM-MSCs' (ND, MM) components, more easily targeted, in manipulation of MM cell lines phenotype and TI with specific focus on microvesicles (MVs) capable of transferring critical biological material. We applied ND and MM-MSCs 72h secretomes to MM cell lines (U266 and ARP-1) for 12-72h and then assayed the cells' (viability, cell count, cell death, proliferation, cell cycle, autophagy) and TI (factors: eIF4E, teIF4GI; regulators: mTOR, MNK1/2, 4EBP; targets: cyclin D1, NFκB, SMAD5, cMyc, HIF1α). Furthermore, we dissected the secretome into >100kDa and <100kDa fractions and repeated the experiments. Finally, MVs were isolated from the ND and MM-MSCs secretomes and applied to MM cell lines. Phenotype and TI were assessed. Secretomes of BM-MSCs (ND, MM) significantly stimulated MM cell lines' TI, autophagy and proliferation. The dissected secretome yielded different effects on MM cell lines phenotype and TI according to fraction (>100kDa- repressed; <100kDa- stimulated) but with no association to source (ND, MM). Finally, in analyses of MVs extracted from BM-MSCs (ND, MM) we witnessed differences in accordance with source: ND-MSCs MVs inhibited proliferation, autophagy and TI whereas MM-MSCs MVs stimulated them. These observations highlight the very complex communication between MM and BM-MSCs and underscore its significance to major processes in the malignant cells. Studies into the influential MVs cargo are underway and expected to uncover targetable signals in the regulation of the TI/proliferation/autophagy cascade.

The potential diagnostic power of extracellular vesicle analysis for multiple myeloma

Multiple myeloma (MM) is a hematologic malignancy of plasma cells (PCs). In the United States, MM accounts for approximately 1% of all diagnoses and 2% of all cancer-related deaths. Although MM is a treatable disease, most patients eventually relapse, and despite the development of numerous treatment options it is still considered incurable. Mechanisms of communication between MM-PCs and bone marrow microenvironment, including cell-cell contacts and release of pro-survival factors, promote cancer cell survival and drug resistance. Recently, the importance of extracellular vesicles (EVs) as mechanisms of communication between MM cells and other cells in the microenvironment has been reported. In this review, the authors provide the update on the biology and clinical aspects of EVs in MM.

Metabolic exchanges within tumor microenvironment

Tumor progression toward malignancy often requires a metabolic rewiring of cancer cells to meet changes in metabolic demand to forefront nutrient and oxygen withdrawal, together with strong anabolic requests to match high proliferation rate. Tumor microenvironment highly contributes to metabolic rewiring of cancer cells, fostering complete nutrient exploitation, favoring OXPHOS of lipids and glutamine at the expense of glycolysis and enhancing exchanges via extracellular microvesicles or exosomes of proteins, lipids and small RNAs among tumor and stromal cells. Noteworthy, the same molecular drivers of metabolic reprogramming within tumor and stroma are also able to elicit motility, survival and self-renewal on cancer cells, thereby sustaining successful escaping strategies to circumvent the hostile hypoxic, acidic and inflammatory environment. This review highlights the emerging role of nutrients and vesicle-mediated exchanges among tumor and stromal cells, defining their molecular pathways and offering new perspectives to develop treatments targeting this complex metabolic rewiring.

Exosome Adherence and Internalization by Hepatic Stellate Cells Triggers Sphingosine 1-Phosphate-dependent Migration

Exosomes are cell-derived extracellular vesicles thought to promote intercellular communication by delivering specific content to target cells. The aim of this study was to determine whether endothelial cell (EC)-derived exosomes could regulate the phenotype of hepatic stellate cells (HSCs). Initial microarray studies showed that fibroblast growth factor 2 induced a 2.4-fold increase in mRNA levels of sphingosine kinase 1 (SK1). Exosomes derived from an SK1-overexpressing EC line increased HSC migration 3.2-fold. Migration was not conferred by the dominant negative SK1 exosome. Incubation of HSCs with exosomes was also associated with an 8.3-fold increase in phosphorylation of AKT and 2.5-fold increase in migration. Exosomes were found to express the matrix protein and integrin ligand fibronectin (FN) by Western blot analysis and transmission electron microscopy. Blockade of the FN-integrin interaction with a CD29 neutralizing antibody or the RGD peptide attenuated exosome-induced HSC AKT phosphorylation and migration. Inhibition of endocytosis with transfection of dynamin siRNA, the dominant negative dynamin GTPase construct Dyn2K44A, or the pharmacological inhibitor Dynasore significantly attenuated exosome-induced AKT phosphorylation. SK1 levels were increased in serum exosomes derived from mice with experimental liver fibrosis, and SK1 mRNA levels were up-regulated 2.5-fold in human liver cirrhosis patient samples. Finally, S1PR2 inhibition protected mice from CCl4-induced liver fibrosis. Therefore, EC-derived SK1-containing exosomes regulate HSC signaling and migration through FN-integrin-dependent exosome adherence and dynamin-dependent exosome internalization. These findings advance our understanding of EC/HSC cross-talk and identify exosomes as a potential target to attenuate pathobiology signals.

NAD⁺-Metabolizing Ectoenzymes in Remodeling Tumor-Host Interactions: The Human Myeloma Model

Nicotinamide adenine dinucleotide (NAD⁺) is an essential co-enzyme reported to operate both intra- and extracellularly. In the extracellular space, NAD⁺ can elicit signals by binding purinergic P2 receptors or it can serve as the substrate for a chain of ectoenzymes. As a substrate, it is converted to adenosine (ADO) and then taken up by the cells, where it is transformed and reincorporated into the intracellular nucleotide pool. Nucleotide-nucleoside conversion is regulated by membrane-bound ectoenzymes. CD38, the main mammalian enzyme that hydrolyzes NAD⁺, belongs to the ectoenzymatic network generating intracellular Ca(2+)-active metabolites. Within this general framework, the extracellular conversion of NAD⁺ can vary significantly according to the tissue environment or pathological conditions. Accumulating evidence suggests that tumor cells exploit such a network for migrating and homing to protected areas and, even more importantly, for evading the immune response. We report on the experience of this lab to exploit human multiple myeloma (MM), a neoplastic expansion of plasma cells, as a model to investigate these issues. MM cells express high levels of surface CD38 and grow in an environment prevalently represented by closed niches hosted in the bone marrow (BM). An original approach of this study derives from the recent use of the clinical availability of therapeutic anti-CD38 monoclonal antibodies (mAbs) in perturbing tumor viability and enzymatic functions in conditions mimicking what happens in vivo.