The systemic cytokine environment is permanently altered in multiple myeloma

Effects of mesenchymal stem cells from different sources on the biological functions of multiple myeloma cells

BACKGROUND

The therapeutic benefits of mesenchymal stromal cells (MSCs) are largely dependent on paracrine factors, but the supernatants of the different MSCs may have different effects on multiple myeloma (MM) cells. Therefore, this study compared supernatants of bone marrow-derived mesenchymal stromal cells (BM-MSCs) with umbilical cord wharton's jelly's mesenchymal stem cells (UC-WJ MSCs) in different states (non-senescent and replicative senescence) on the MM cells.

METHODS

We extracted human BM-MSCs and UC-WJ MSCs in vitro and used H2O2 to induce replicative senescence. Concentrated supernatants from MSCs and senescent MSCs (SMSCs) were added to MM cells. Cell proliferation, the cell cycle, apoptosis, cell migration, tumor stemness factor expression, and cytokine expression levels were analyzed. Transcription regulation of signaling pathways was discussed.

RESULTS

We successfully isolated and identified BM-MSCs, UC-WJ MSCs, and SMSCs. When concentrated supernatants from BM-MSCs, UC-WJ MSCs, senescent BM-MSCs (SBM-MSCs), senescent UCWJ MSCs (SUC-WJ MSCs) were used to treat MM cells, BMMSCs and SBM-MSCs supernatants promoted the proliferation of MM cells, with a more pronounced effect by SBM-MSCs. UC-WJ MSCs and SUC-WJ MSCs supernatants inhibited the viability and proliferation of MM cells. BM-MSCs and SBM-MSCs supernatants increased the proportion of MM cells in the S-phase, with the effect of SBM-MSCs being more evident. UC-WJ MSCs and SUC-WJ MSCs supernatants arrested MM cells in the G0/G1 phase. BM-MSCs and SBM-MSCs supernatants enhanced the migration and tumor stemness of MM cells, with SBMMSCs having a more dramatic effect. UC-WJ MSCs and SUC-WJ MSCs supernatants inhibited the migration and tumor stemness of MM cells, with UC-WJ MSCs having a more inhibitory effect. IL-6 and VEGFA expression correlated negatively with the survival of patients with MM according to online database analysis, in addition, we found that the expression of IL-6 and VEGFA was higher in MM patients through GEO database analysis. BM-MSCs and SBM-MSCs supernatants treatment increased the expression of IL-6 and VEGFA on MM cells, while UC-WJ MSCs and SUC-WJ MSCs supernatants inhibited their expression. Signal pathway validation showed that the biological function of MSCs in MM is closely related to the PI3K/AKT/NF-κB pathway.

CONCLUSION

The supernatants of BM-MSCs promote the proliferation of MM cells, On the contrary, the supernatants of UC-WJ MSCs inhibit MM cell proliferation. We observed that MSCs from different sources and different states have contrasting biological functions in MM cells. Furthermore, this research was provided to the optimal cancer gene therapy vector for MM was UC-WJ MSCs, even UC-WJ MSCs was in the state of senescence.

Comprehensive analysis of serum cytokines in patients with multiple myeloma before and after lenalidomide and dexamethasone

Multiple myeloma (MM) is an incurable B-cell malignancy often accompanied by profound immunodeficiency. Lenalidomide (Len) is an immunomodulatory drug that exerts promising therapeutic effects on MM through the immune system. However, predictive markers related to the effects of Len treatment are not fully understood. This study aimed to identify candidate biomarkers for predicting the clinical efficacy of Len and dexamethasone (Ld) therapy through a comprehensive analysis of serum cytokines. The levels of 48 cytokines in the serum of patients with MM just before Ld therapy (n = 77), at the time of best response (n = 56), and at disease progression (n = 49) were measured and evaluated. Patients with high IL-18 and M-CSF levels showed significantly shorter progression-free survival and overall survival (OS). In contrast, patients with high PDGF-BB levels had longer survival. Moreover, low levels of G-CSF, IL-7, IL-8, and SDF-1α were associated with shorter OS after Ld therapy. During Ld therapy, pro-inflammatory cytokines such as IL-2Rα, IL-18, and TNF-α were decreased, while IFN-γ was increased. IL-4 and IL-6 levels increased during disease progression. In conclusion, this study provides a better understanding of the association between cytokines and the efficacy of Ld therapy as well as the unique changes in cytokines related to inflammatory and immune responses during Ld therapy.

Exploring the potential of combining IL-2-activated NK cells with an anti-PDL1 monoclonal antibody to target multiple myeloma-associated macrophages

Multiple myeloma (MM) is an incurable disease, characterized by malignant plasma cells in the bone marrow. MM growth is largely dependent on the tumor microenvironment (TME), consisting of complex cellular networks that shape a tumor-permissive environment. Within the TME, tumor-associated cells (TAC) comprise heterogeneous cell populations that collectively support immunosuppression. Reshaping the TME toward an immunostimulatory environment may enhance effectiveness of immunotherapies. Here, we investigated interactions between donor-derived natural killer (NK) cells and TAC, like tumor-associated macrophages (TAM) and M1 macrophages, and assessed whether anti-tumor effector functions of NK cells could be enhanced by an ADCC-triggering antibody targeting macrophages. Monocytes were polarized in vitro toward either M1 or TAM before co-culture with high-dose IL-2-activated NK cells. NK cell responses were assessed by measuring degranulation (CD107a) and IFN-γ production. We found that NK cells degranulated and produced IFN-γ upon interaction with both macrophage types. NK cell responses against PD-L1⁺ M1 macrophages could be further enhanced by Avelumab, an anti-PD-L1- and ADCC-inducing antibody. Additionally, NK cell responses were influenced by HLA class I, shown by stronger degranulation in NK cell subsets for which the corresponding HLA ligand was absent on the macrophage target cells (KIR-ligand mismatch) compared to degranulation in the presence of the HLA ligand (KIR-ligand match). Our results suggest that NK cells could, next to killing tumor cells, get activated upon interaction with TAC, like M1 macrophages and TAMs, and that NK cells combined with PD-L1 blocking antibodies with ADCC potential could, through IFN-γ secretion, promote a more immune-favorable TME.

Molecular Features of the Mesenchymal and Osteoblastic Cells in Multiple Myeloma

Multiple myeloma (MM) is a monoclonal gammopathy characterized by biological heterogeneity and unregulated proliferation of plasma cells (PCs) in bone marrow (BM). MM is a multistep process based on genomic instability, epigenetic dysregulation and a tight cross-talk with the BM microenvironment that plays a pivotal role supporting the proliferation, survival, drug-resistance and homing of PCs. The BM microenvironment consists of a hematopoietic and a non-hematopoietic compartment, which cooperate to create a tumor environment. Among the non-hematopoietic component, mesenchymal stromal cells (MSCs) and osteoblasts (OBs) appear transcriptionally and functionally different in MM patients compared to healthy donors (HDs) and to patients with pre-malignant monoclonal gammopathies. Alterations of both MSCs and OBs underly the osteolytic lesions that characterize myeloma-associated bone disease. In this review, we will discuss the different characteristics of MSCs and OBs in MM patients, analyzing the transcriptome, the deregulated molecular pathways and the role performed by miRNAs and exosome in the pathophysiology of MM.

Immune senescence in multiple myeloma-a role for mitochondrial dysfunction?

Age-related immune dysfunction is primarily mediated by immunosenescence which results in ineffective clearance of infective pathogens, poor vaccine responses and increased susceptibility to multi-morbidities. Immunosenescence-related immunometabolic abnormalities are associated with accelerated aging, an inflammatory immune response (inflammaging) and ultimately frailty syndromes. In addition, several conditions can accelerate the development of immunosenescence, including cancer. This is a bi-directional interaction since inflammaging may create a permissive environment for tumour development. Multiple myeloma (MM) is a mature B-cell malignancy that presents in the older population. MM exemplifies the interaction of age- (Host Response Biology; HRB) and disease-related immunological dysfunction, contributing to the development of a frailty syndrome which impairs the therapeutic impact of recent advances in treatment strategies. Understanding the mechanisms by which accelerated immunological aging is induced and the ways in which a tumour such as MM influences this process is key to overcoming therapeutic barriers. A link between cellular mitochondrial dysfunction and the acquisition of an abnormal immune phenotype has recently been described and has widespread physiological consequence beyond the impact on the immune system. Here we outline our current understanding of normal immune aging, describe the mechanism of immunometabolic dysfunction in accelerating this process, and propose the role these processes are playing in the pathogenesis of MM.

Host-microbe interactions and outcomes in multiple myeloma and hematopoietic stem cell transplantation

Microbiota are essential to normal immune development and there is growing recognition of its importance to human health and disease and deepening understanding of the complexity of host-microbe interactions in the human gut and other tissues. Commensal microbes not only can influence host immunity locally through impacts of bioactive microbial metabolites and direct interactions with epithelial cells and innate immune receptors but also can exert systemic immunomodulatory effects via impacts on host immune cells capable of trafficking beyond the gut. Emerging data suggest microbiota influence the development of multiple myeloma (MM), a malignancy of the immune system derived from immunoglobulin-producing bone marrow plasma cells, through the promotion of inflammation. Superior treatment outcomes for MM correlate with a higher abundance of commensal microbiota capable of influencing inflammatory responses through the production of butyrate. In patients with hematologic malignancies, higher levels of diversity of the gut microbiota correlate with superior outcomes after hematopoietic stem cell transplantation. Correlative data support the impact of commensal microbiota on survival, risk of infection, disease relapse, and graft-versus-host disease (GVHD) after transplant. In this review, we will discuss the current understanding of the role of host-microbe interactions and the inflammatory tumor microenvironment of multiple myeloma, discuss data describing the key role of microbiota in hematopoietic stem cell transplantation for treatment of hematologic malignancies, and highlight several possible concepts for interventions directed at the gut microbiota to influence treatment outcomes.

Natural Killer Cells in the Malignant Niche of Multiple Myeloma

Natural killer (NK) cells represent a subset of CD3- CD7+ CD56+/dim lymphocytes with cytotoxic and suppressor activity against virus-infected cells and cancer cells. The overall potential of NK cells has brought them to the spotlight of targeted immunotherapy in solid and hematological malignancies, including multiple myeloma (MM). Nonetheless, NK cells are subjected to a variety of cancer defense mechanisms, leading to impaired maturation, chemotaxis, target recognition, and killing. This review aims to summarize the available and most current knowledge about cancer-related impairment of NK cell function occurring in MM.

Pretreatment Serum Levels of IL-1 Receptor Antagonist and IL-4 Are Predictors of Overall Survival in Multiple Myeloma Patients Treated with Bortezomib

Multiple myeloma (MM) is characterized by the malignant proliferation of monoclonal plasma cells in the bone marrow with an elevation in monoclonal paraprotein, renal impairment, hypercalcemia, lytic bony lesions, and anemia. Immune cells and associated cytokines play a significant role in MM growth, progression, and dissemination. While some cytokines and their clinical significance are well described in MM biology, others remain relatively unknown. The present study examines the influence on progression-free survival (PFS) and overall survival (OS) by the serum levels of 27 selected cytokines in 61 newly diagnosed MM patients receiving first-line therapy with bortezomib-based regimens. The measurements were performed using a Bio-Rad Bio-Plex Pro Human Cytokine 27-Plex Assay and a MAGPIX Multiplex Reader, based on the Bio-Plex® 200 System (Bio-Rad). The following levels were determined: IL-1β, IL-1Ra, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-12, IL-13, IL-15, IL-17, Eotaxin, FGF, G-CSF, GM-CSF, IFN-γ, IP-10, MCP-1, MIP-1α, MIP-1β, PDGF-BB, RANTES, TNF-α, and VEGF. Most patients received a VCD chemotherapy regimen (bortezomib, cyclophosphamide, and dexamethasone). In the final multivariate model, IL-13 cytokine level (HR 0.1411, 95% CI: 0.0240-0.8291, p = 0.0302) and ASCT (HR 0.3722, 95% CI: 0.1826-0.7585, p = 0.0065) significantly impacted PFS. Furthermore, ASCT (HR 0.142, 95% CI: 0.046-0.438, p = 0.0007), presence of bone disease at diagnosis (HR 3.826, 95% CI: 1.471-9.949, p = 0.0059), and two cytokine levels-IL-1Ra (HR 1.017, 95% CI: 1.004-1.030, p = 0.0091) and IL-4 (HR 0.161, 95% CI: 0.037-0.698, p = 0.0147)-were independent predictors of OS. Three clusters of MM patients were identified with different cytokine profiles. In conclusion, serum pretreatment levels of IL-13 and IL-4 are predictors of better PFS and OS, respectively, whereas IL-1Ra pretreatment levels negatively impact OS in MM patients treated with bortezomib-based chemotherapy. Cytokine signature profile may have a potential influence on the outcome of patients treated with bortezomib.

Aging-associated immune system changes in multiple myeloma: The dark side of the moon

Multiple myeloma (MM) is a disease of the elderly. Changes that occur in the immune system with aging, also known as immunosenescence, have been associated with decreased tumor immunosurveillance and are thought to contribute to the development of MM and other cancers in the elderly. Once MM establishes itself in the bone marrow, immunosenescence related changes have been observed in the immune tumor microenvironment (iTME) and are driven by the malignant cells. The efficacy of novel immunotherapies used to treat MM has been blunted by detrimental iTME changes that occur at later disease stages and are, to some extent, driven by prior therapies. In this review, we discuss general changes that occur in the immune system with aging as well as our current knowledge of immunosenescence in MM. We discuss the differences and overlap between T cell senescence and exhaustion as well as potential methods to prevent or reverse immunosenescence. We focus predominantly on T cell immunosenescence which has been better evaluated in this disease and is more pertinent to novel MM immunotherapies. Our lack of understanding of the drivers of immunosenescence at each stage of the disease, from precursor stages to heavily pretreated MM, represents a major barrier to improving the efficacy of novel and existing therapies.

Treatment Induced Cytotoxic T-Cell Modulation in Multiple Myeloma Patients

The biology of plasma cell dyscrasias (PCD) involves both genetic and immune-related factors. Since genetic lesions are necessary but not sufficient for Multiple Myeloma (MM) evolution, several authors hypothesized that immune dysfunction involving both B and T cell counterparts plays a key role in the pathogenesis of the disease. The aim of this study is to evaluate the impact of cornerstone treatments for Multiple Myeloma into immune system shaping. A large series of 976 bone marrow samples from 735 patients affected by PCD was studied by flow analysis to identify discrete immune subsets. Treated MM samples displayed a reduction of CD4+ cells (p<0.0001) and an increase of CD8+ (p<0.0001), CD8+/DR+ (p<0.0001) and CD3+/CD57+ (p<0.0001) cells. Although these findings were to some extent demonstrated also following bortezomib treatment, a more pronounced cytotoxic polarization was shown after exposure to autologous stem cell transplantation (ASCT) and Lenalidomide (Len) treatment. As a matter of fact, samples of patients who received ASCT (n=110) and Len (n=118) were characterized, towards untreated patients (n=138 and n=130, respectively), by higher levels of CD8+ (p<0.0001 and p<0.0001, respectively), CD8+/DR+ (p=0.0252 and p=0.0001, respectively) and CD3+/CD57+ cells (p<0.0001 and p=0.0006, respectively) and lower levels of CD4+ lymphocytes (p<0.0001 and p=0.0005, respectively). We demonstrated that active MM patients are characterized by a relevant T cell modulation and that most of these changes are therapy-related. Current Myeloma treatments, notably ASCT and Len treatments, polarize immune system towards a dominant cytotoxic response, likely contributing to the anti-Myeloma effect of these regimens.

Complement C3a activates osteoclasts by regulating the PI3K/PDK1/SGK3 pathway in patients with multiple myeloma

OBJECTIVE

Myeloma bone disease (MBD) is the most common complication of multiple myeloma (MM). Our previous study showed that the serum levels of C3/C4 in MM patients were significantly positively correlated with the severity of bone disease. However, the mechanism of C3a/C4a in osteoclasts MM patients remains unclear.

METHODS

The formation and function of osteoclasts were analyzed after adding C3a/C4a in vitro. RNA-seq analysis was used to screen the potential pathways affecting osteoclasts, and the results were verified by Western blot, qRT-PCR, and pathway inhibitors.

RESULTS

The osteoclast area per view induced by 1 μg/mL (mean ± SD: 50.828 ± 12.984%) and 10 μg/mL (53.663 ± 12.685%) of C3a was significantly increased compared to the control group (0 μg/mL) (34.635 ± 8.916%) (P < 0.001 and P < 0.001, respectively). The relative mRNA expressions of genes, OSCAR/TRAP/RANKL/cathepsin K, induced by 1 μg/mL (median: 5.041, 3.726, 1.638, and 4.752, respectively) and 10 μg/mL (median: 5.140, 3.702, 2.250, and 5.172, respectively) of C3a was significantly increased compared to the control group (median: 3.137, 2.004, 0.573, and 2.257, respectively) (1 μg/mL P = 0.001, P = 0.003, P < 0.001, and P = 0.008, respectively; 10 μg/mL: P < 0.001, P = 0.019, P < 0.001, and P = 0.002, respectively). The absorption areas of the osteoclast resorption pits per view induced by 1 μg/mL (mean ± SD: 51.464 ± 11.983%) and 10 μg/mL (50.219 ± 12.067%) of C3a was also significantly increased (33.845 ± 8.331%) (P < 0.001 and P < 0.001, respectively) compared to the control. There was no difference between the C4a and control groups. RNA-seq analysis showed that C3a promoted the proliferation of osteoclasts using the phosphoinositide 3-kinase (PI3K) signaling pathway. The relative expressions of PIK3CA/phosphoinositide dependent kinase-1 (PDK1)/serum and glucocorticoid inducible protein kinases (SGK3) genes and PI3K/PDK1/p-SGK3 protein in the C3a group were significantly higher than in the control group. The activation role of C3a in osteoclasts of MM patients was reduced by the SGK inhibitor (EMD638683).

CONCLUSIONS

C3a activated osteoclasts by regulating the PI3K/PDK1/SGK3 pathways in MM patients, which was reduced using a SGK inhibitor. Overall, our results identified potential therapeutic targets and strategies for MBD patients.

Quantitative polymerase Chain reaction profiling of microRNAs in peripheral lymph-monocytes from MGUS subjects

Monoclonal gammopathy of undetermined significance (MGUS) is a pre-malignant abnormality of plasma cells, with increased serum levels of immunoglobulins. Patients with MGUS may evolve to multiple myeloma through a multistep process including deregulated gene expression. microRNAs are small non-coding RNA molecules involved in post-transcriptional regulation of crucial biological processes, such as morphogenesis, cell differentiation, apoptosis, and cancer. This study aimed to evaluate microRNA expression on peripheral lymph-monocytes from MGUS subjects compared with healthy controls using qPCR arrays. Blood samples were collected by venipuncture from fifteen, newly diagnosed MGUS patients and fifteen healthy subjects. A further group (validation group) of six newly diagnosed MGUS patients and five healthy control were enrolled for the validation of miRNAs and their mRNAs target. The study was conducted performing miProfile miRNA qPCR arrays, followed by validation of miRNAs and related mRNA targets through RT-qPCR. The functional interaction between microRNAs and target gene were obtained by Ingenuity Pathways Analysis (IPA). IPA network analysis identified only molecules and relationships experimentally observed in peripheral lymphomonocytes. The following miRNAs :133a-3p, 16-5p, 291-3p, 23a-3p, 205-5p, 17-5p, 7a-5p, 221-3p, 30c-5p, 126a-3p,155-5p, let-7a-5p and 26a-5p, involved in the regulation of genes with a role in lymphocyte homeostasis, cell proliferation, apoptosis, and multiple myeloma (MM) progression, were differently expressed in MGUS with respect to healthy subjects. This miRNA signature and its relative targets could be considered for the formulation of new therapeutic strategies in the prophylaxis or treatment of monoclonal gammopathies.

Continuous lenalidomide and low-dose dexamethasone in patients with transplant-ineligible newly diagnosed MM: FIRST trial subanalysis of Canadian/US patients

The phase 3 FIRST trial demonstrated significant improvement in progression-free survival (PFS) and overall survival (OS) with an immune-stimulatory agent, lenalidomide, in combination with low-dose dexamethasone until disease progression (Rd continuous) vs melphalan +prednisone + thalidomide (MPT) in transplant-ineligible patients with newly diagnosed multiple myeloma (NDMM). Rd continuous similarly extended PFS vs fixed-duration Rd for 18 cycles (Rd18). Outcomes in the Canadian/US subgroup (104 patients per arm) are reported in this analysis. Rd continuous demonstrated a significant improvement in PFS vs MPT (median, 29.3 vs 20.2 months; HR, 0.69 [95% CI, 0.49-0.97]; p = 0.03326) and an improvement vs Rd18 (median, 21.9 months). Median OS was 56.9 vs 46.8 months with Rd continuous vs MPT (p = 0.15346) and 59.5 months with Rd18. The overall response rate was higher with Rd continuous and Rd18 (78.8% and 79.8%) vs MPT (65.4%). In the 49.0%, 52.9%, and 29.8% of patients with at least very good partial response in the Rd continuous, Rd18, and MPT arms, respectively, the median PFS was 56.0, 30.9, and 40.2 months, respectively. The most common grade 3/4 treatment-emergent adverse events were neutropenia (28.4%, 30.1%, and 52.0%), anemia (23.5%, 21.4%, and 23.5%), and infections (37.3%, 30.1%, and 24.5%) with Rd continuous, Rd18, and MPT, respectively. These results were consistent with those in the intent-to-treat population, confirming the benefit of Rd continuous vs MPT in the Canadian/US subgroup and supporting the role of Rd continuous as a standard of care for transplant-ineligible patients with NDMM.

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

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

Cytokine and Chemokine Profile in Patients with Multiple Myeloma Treated with Bortezomib

The aim of the study was to determine the levels of selected cytokines and chemokines in the serum of multiple myeloma (MM) patients treated with bortezomib-based regimens. A total of 71 MM patients were examined: 41 with primary refractory disease (17) or early relapse (28), and 30 who were bortezomib sensitive with no progression for at least six months. Patients who demonstrated CR or PR after bortezomib-based therapies longer than six months after treatment discontinuation were designated bortezomib sensitive. Serum cytokine levels were assayed with Bio-Rad Bio-Plex Pro Human Cytokine 27-Plex Assay on the MAGPIX Multiplex Reader and the Bio-Plex® 200 System (Bio-Rad). Higher levels of MIP-1α and lower levels of MIP-1β and IL-9 were associated with better responses to bortezomib-based treatment, and higher levels of IL-1ra and IL-8 were associated with bone involvement. MCP-1 was elevated in patients with hemoglobin < 10 g/dl compared to those without anemia. The levels of IL-8, MIP-1α, and TNF-α were significantly higher in patients with renal insufficiency. Only MIP-1α was elevated in patients with hypercalcemia compared to patients with normal calcium levels. In conclusion, distinct cytokines are involved in the pathogenesis of MM and may play a prominent role in the prediction of treatment response. However, a single measurement of serum cytokines should be interpreted with caution and further studies are needed.

Characteristics of MGUS and Multiple Myeloma According to the Target of Monoclonal Immunoglobulins, Glucosylsphingosine, or Epstein-Barr Virus EBNA-1

Chronic stimulation by infectious or self-antigens initiates subsets of monoclonal gammopathies of undetermined significance (MGUS), smoldering multiple myeloma (SMM), or multiple myeloma (MM). Recently, glucosylsphingosine (GlcSph) was reported to be the target of one third of monoclonal immunoglobulins (Igs). In this study of 233 patients (137 MGUS, 6 SMM, 90 MM), we analyzed the GlcSph-reactivity of monoclonal Igs and non-clonal Igs. The presence of GlcSph-reactive Igs in serum was unexpectedly frequent, detected for 103/233 (44.2%) patients. However, GlcSph was targeted by the patient’s monoclonal Ig for only 37 patients (15.9%); for other patients (44 MGUS, 22 MM), the GlcSph-reactive Igs were non-clonal. Then, the characteristics of patients were examined: compared to MM with an Epstein-Barr virus EBNA-1-reactive monoclonal Ig, MM patients with a GlcSph-reactive monoclonal Ig had a mild presentation. The inflammation profiles of patients were similar except for moderately elevated levels of 4 cytokines for patients with GlcSph-reactive Igs. In summary, our study highlights the importance of analyzing clonal Igs separately from non-clonal Igs and shows that, if autoimmune responses to GlcSph are frequent in MGUS/SMM and MM, GlcSph presumably represents the initial pathogenic event for ~16% cases. Importantly, GlcSph-initiated MM appears to be a mild form of MM disease.

Vγ9Vδ2 T Cells as Strategic Weapons to Improve the Potency of Immune Checkpoint Blockade and Immune Interventions in Human Myeloma

The advent of immune checkpoint (ICP) blockade has introduced an unprecedented paradigm shift in the treatment of cancer. Though very promising, there is still a substantial proportion of patients who do not respond or develop resistance to ICP blockade. In vitro and in vivo models are eagerly needed to identify mechanisms to maximize the immune potency of ICP blockade and overcome primary and acquired resistance to ICP blockade. Vγ9Vδ2 T cells isolated from the bone marrow (BM) from multiple myeloma (MM) are excellent tools to investigate the mechanisms of resistance to PD-1 blockade and to decipher the network of mutual interactions between PD-1 and the immune suppressive tumor microenvironment (TME). Vγ9Vδ2 T cells can easily be interrogated to dissect the progressive immune competence impairment generated in the TME by the long-lasting exposure to myeloma cellss. BM MM Vγ9Vδ2 T cells are PD-1⁺ and anergic to phosphoantigen (pAg) stimulation; notably, single agent PD-1 blockade is insufficient to fully recover their anti-tumor activity in vitro indicating that additional players are involved in the anergy of Vγ9Vδ2 T cells. In this mini-review we will discuss the value of Vγ9Vδ2 T cells as investigational tools to improve the potency of ICP blockade and immune interventions in MM.

Aging- and vascular-related pathologies

Our aging population is set to grow considerably in the coming decades. In fact, the number of individuals older than 65 years will double by 2050. This projected increase in people living with extended life expectancy represents an inevitable upsurge in the presentation of age-related pathologies. However, our current understanding of the impact of aging on a number of biological processes is unfortunately inadequate. Cardiovascular, cerebrovascular, and neurodegenerative diseases are particularly prevalent in the elderly population. Intriguingly, these pathologies are all associated with vascular dysfunction, suggesting that the process of aging can induce structural and functional impairments in vascular networks. Together with elevated cell senescence, pre-existing comorbidities, and the emerging concept of age-associated inflammatory imbalance, impaired vascular functions can significantly increase one's risk in acquiring age-related diseases. In this short review, we highlight some current clinical and experimental evidence of how biological aging contributes to three vascular-associated pathologies: atherosclerosis, stroke, and Alzheimer's disease.

The insulin-like growth factor system in multiple myeloma: diagnostic and therapeutic potential

Multiple myeloma (MM) is a highly heterogeneous plasma cell malignancy. The MM cells reside in the bone marrow (BM), where reciprocal interactions with the BM niche foster MM cell survival, proliferation, and drug resistance. As in most cancers, the insulin-like growth factor (IGF) system has been demonstrated to play a key role in the pathogenesis of MM. The IGF system consists of IGF ligands, IGF receptors, IGF binding proteins (IGFBPs), and IGFBP proteases and contributes not only to the survival, proliferation, and homing of MM cells, but also MM-associated angiogenesis and osteolysis. Furthermore, increased IGF-I receptor (IGF-IR) expression on MM cells correlates with a poor prognosis in MM patients. Despite the prominent role of the IGF system in MM, strategies targeting the IGF-IR using blocking antibodies or small molecule inhibitors have failed to translate into the clinic. However, increasing preclinical evidence indicates that IGF-I is also involved in the development of drug resistance against current standard-of-care agents against MM, including proteasome inhibitors, immunomodulatory agents, and corticoids. IGF-IR targeting has been able to overcome or revert this drug resistance in animal models, enhancing the efficacy of standard-of-care agents. This finding has generated renewed interest in the therapeutic potential of IGF-I targeting in MM. The present review provides an update of the impact of the different IGF system components in MM and discusses the diagnostic and therapeutic potentials.

Restoring Natural Killer Cell Immunity against Multiple Myeloma in the Era of New Drugs

Transformed plasma cells in multiple myeloma (MM) are susceptible to natural killer (NK) cell-mediated killing via engagement of tumor ligands for NK activating receptors or “missing-self” recognition. Similar to other cancers, MM targets may elude NK cell immunosurveillance by reprogramming tumor microenvironment and editing cell surface antigen repertoire. Along disease continuum, these effects collectively result in a progressive decline of NK cell immunity, a phenomenon increasingly recognized as a critical determinant of MM progression. In recent years, unprecedented efforts in drug development and experimental research have brought about emergence of novel therapeutic interventions with the potential to override MM-induced NK cell immunosuppression. These NK-cell enhancing treatment strategies may be identified in two major groups: (1) immunomodulatory biologics and small molecules, namely, immune checkpoint inhibitors, therapeutic antibodies, lenalidomide, and indoleamine 2,3-dioxygenase inhibitors and (2) NK cell therapy, namely, adoptive transfer of unmanipulated and chimeric antigen receptor-engineered NK cells. Here, we summarize the mechanisms responsible for NK cell functional suppression in the context of cancer and, specifically, myeloma. Subsequently, contemporary strategies potentially able to reverse NK dysfunction in MM are discussed.

Pro-inflammatory State in Monoclonal Gammopathy of Undetermined Significance and in Multiple Myeloma Is Characterized by Low Sialylation of Pathogen-Specific and Other Monoclonal Immunoglobulins

Multiple myeloma (MM) and its pre-cancerous stage monoclonal gammopathy of undetermined significance (MGUS) allow to study immune responses and the chronology of inflammation in the context of blood malignancies. Both diseases are characterized by the production of a monoclonal immunoglobulin (mc Ig) which for subsets of MGUS and MM patients targets pathogens known to cause latent infection, a major cause of inflammation. Inflammation may influence the structure of both polyclonal (pc) Ig and mc Ig produced by malignant plasma cells via the sialylation of Ig Fc fragment. Here, we characterized the sialylation of purified mc and pc IgGs from 148 MGUS and MM patients, in comparison to pc IgGs from 46 healthy volunteers. The inflammatory state of patients was assessed by the quantification in serum of 40 inflammation-linked cytokines, using Luminex technology. While pc IgGs from MGUS and MM patients showed heterogeneity in sialylation level, mc IgGs from both MGUS and MM patients exhibited a very low level of sialylation. Furthermore, mc IgGs from MM patients were less sialylated than mc IgGs from MGUS patients (p < 0.01), and mc IgGs found to target an infectious pathogen showed a lower level of sialylation than mc IgGs of undetermined specificity (p = 0.048). Regarding inflammation, 14 cytokines were similarly elevated with a p value < 0.0001 in MGUS and in MM compared to healthy controls. MM differed from MGUS by higher levels of HGF, IL-11, RANTES and SDF-1-α (p < 0.05). MGUS and MM patients presenting with hyposialylated pc IgGs had significantly higher levels of HGF, IL-6, tumor necrosis factor-α, TGF-β1, IL-17, and IL-33 compared to patients with hyper-sialylated pc IgGs (p < 0.05). In MGUS and in MM, the degree of sialylation of mc and pc IgGs and the levels of four cytokines important for the anti-microbial response were correlated, either positively (IFN-α2, IL-13) or negatively (IL-17, IL-33). Thus in MGUS as in MM, hyposialylation of mc IgGs is concomitant with increased levels of cytokines that play a major role in inflammation and anti-microbial response, which implies that infection, inflammation, and abnormal immune response contribute to the pathogenesis of MGUS and MM.

Predicting Risk of Infection in Patients with Newly Diagnosed Multiple Myeloma: Utility of Immune Profiling

Background

A translational study in patients with myeloma to determine the utility of immune profiling to predict infection risk in patients with hematological malignancy was conducted.

Methods

Baseline, end of induction, and maintenance peripheral blood mononuclear cells from 40 patients were evaluated. Immune cell populations and cytokines released from 1 × 10⁶ cells/ml cultured in the presence of a panel of stimuli (cytomegalovirus, influenza, S. pneumoniae, phorbol myristate acetate/ionomycin) and in media alone were quantified. Patient characteristics and infective episodes were captured from clinical records. Immunological variables associated with increased risk for infection in the 3-month period following sample collection were identified using univariate analysis (p < 0.05) and refined with multivariable analysis to define a predictive immune profile.

Results

525 stimulant samples with 19,950 stimulant–cytokine combinations across three periods were studied, including 61 episodes of infection. Mitogen-stimulated release of IL3 and IL5 were significantly associated with increased risk for subsequent infection during maintenance therapy. A lower Th1/Th2 ratio and higher cytokine response ratios for IL5 and IL13 during maintenance therapy were also significantly associated with increased risk for infection. On multivariable analysis, only IL5 in response to mitogen stimulation was predictive of infection. The lack of cytokine response and numerical value of immune cells were not predictive of infection.

Conclusion

Profiling cytokine release in response to mitogen stimulation can assist with predicting subsequent onset of infection in patients with hematological malignancy during maintenance therapy.

Potential humoral mediators of remote ischemic preconditioning in patients undergoing surgical coronary revascularization

Remote ischemic preconditioning (RIPC) by repeated brief cycles of limb ischemia/reperfusion may reduce myocardial ischemia/reperfusion injury and improve patients‘ prognosis after elective coronary artery bypass graft (CABG) surgery. The signal transducer and activator of transcription (STAT)5 activation in left ventricular myocardium is associated with RIPC´s cardioprotection. Cytokines and growth hormones typically activate STATs and could therefore act as humoral transfer factors of RIPC´s cardioprotection. We here determined arterial plasma concentrations of 25 different cytokines, growth hormones, and other factors which have previously been associated with cardioprotection, before (baseline)/after RIPC or placebo (n = 23/23), respectively, and before/after ischemic cardioplegic arrest in CABG patients. RIPC-induced protection was reflected by a 35% reduction of serum troponin I release. With the exception of interleukin-1α, none of the humoral factors changed in their concentrations after RIPC or placebo, respectively. Interleukin-1α, when normalized to baseline, increased after RIPC (280 ± 56%) but not with placebo (97 ± 15%). The interleukin-1α concentration remained increased until after ischemic cardioplegic arrest and was also higher than with placebo in absolute concentrations (25 ± 6 versus 16 ± 3 pg/mL). Only interleukin-1α possibly fulfills the criteria which would be expected from a substance to be released in response to RIPC and to protect the myocardium during ischemic cardioplegic arrest.

Serum protein fingerprinting by PEA immunoassay coupled with a pattern-recognition algorithms distinguishes MGUS and multiple myeloma

Serum protein fingerprints associated with MGUS and MM and their changes in MM after autologous stem cell transplantation (MM-ASCT, day 100) remain unexplored. Using highly-sensitive Proximity Extension ImmunoAssay on 92 cancer biomarkers (Proseek Multiplex, Olink), enhanced serum levels of Adrenomedullin (ADM, Pcorr= .0004), Growth differentiation factor 15 (GDF15, Pcorr= .003), and soluble Major histocompatibility complex class I-related chain A (sMICA, Pcorr= .023), all prosurvival and chemoprotective factors for myeloma cells, were detected in MM comparing to MGUS. Comparison of MGUS and healthy subjects revealed elevation of angiogenic and antia-poptotic midkine (Pcorr= .0007) and downregulation of Transforming growth factor beta 1 (TGFB1, Pcorr= .005) in MGUS. Importantly, altered serum pattern was associated with MM-ASCT compared to paired MM at the diagnosis as well as to healthy controls, namely by upregulated B-Cell Activating Factor (sBAFF) (Pcorr< .006) and sustained elevation of other pro-tumorigenic factors. In conclusion, the serum fingerprints of MM and MM-ASCT were characteristic by elevated levels of prosurvival and chemoprotective factors for myeloma cells.

The effect of marrow stromal cells on TRAF6 expression levels in myeloma cells

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is an important E3 ubiquitin ligase, which is key to immunity. TRAF6 has been implicated in the invasive growth and metastasis of various types of cancer, including squamous cell carcinoma, gastric cancer, myelodysplastic syndromes and acute myeloid leukemia. In the present study, associations between multiple myeloma (MM) and TRAF6, its downstream component nuclear factor-κB (NF-κB) and bone marrow stromal cells (MSC) were investigated. The TRAF6 protein expression levels of 18 patients were positively correlated with the protein levels of β-2 microglobulin (r²=0.3472; P=0.01) and negatively correlated with albumin protein levels (r²=0.5494; P=0.0004). In vitro expression of the TRAF6 protein, phosphorylated transcription factor p65 and phosphorylated p100 in myeloma cell lines was induced by MSCs from patients with MM. In addition, the in vitro expression of TRAF6 was associated with an enhanced proliferation rate of myeloma cells, which was blocked by silencing TRAF6 using small interfering RNA. Due to the association between the TRAF6-NF-κB signaling pathway in myeloma cells and MSCs, this signaling pathway may be a useful prognostic and therapeutic target in myeloma.

A mathematical model of cell equilibrium and joint cell formation in multiple myeloma

In Multiple Myeloma Bone Disease healthy bone remodelling is affected by tumour cells by means of paracrine cytokinetic signalling in such a way that osteoclast formation is enhanced and the growth of osteoblast cells inhibited. The participating cytokines are described in the literature. Osteoclast-induced myeloma cell growth is also reported. Based on existing mathematical models for healthy bone remodelling a three-way equilibrium model is presented for osteoclasts, osteoblasts and myeloma cell populations to describe the progress of the illness in a scenario in which there is a secular increase in the cytokinetic interactive effectiveness of paracrine processes. The equilibrium state for the system is obtained. The paracrine interactive effectiveness is explored by parameter variation and the stable region in the parameter space is identified. Then recently-discovered joint myeloma-osteoclast cells are added to the model to describe the populations inside lytic lesions. It transpires that their presence expands the available parameter space for stable equilibrium, thus permitting a detrimental, larger population of osteoclasts and myeloma cells. A possible relapse mechanism for the illness is explored by letting joint cells dissociate. The mathematics then permits the evaluation of the evolution of the cell populations as a function of time during relapse.

Osteolytic lesions, cytogenetic features and bone marrow levels of cytokines and chemokines in multiple myeloma patients: Role of chemokine (C-C motif) ligand 20

The relationship between bone marrow (BM) cytokine and chemokine levels, cytogenetic profiles and skeletal involvement in multiple myeloma (MM) patients is not yet defined. This study investigated a cohort of 455 patients including monoclonal gammopathy of uncertain significance (MGUS), smoldering MM and symptomatic MM patients. Skeletal surveys, positron emission tomography (PET)/computerized tomography (CT) and magnetic resonance imaging (MRI) were used to identify myeloma bone disease. Significantly higher median BM levels of both C-C motif Ligand (CCL)3 and CCL20 were found in MM patients with radiographic evidence of osteolytic lesions as compared with those without, and in all MM patients with positive PET/CT scans. BM levels of CCL3, CCL20, Activin-A and Dickkopf-1 (DKK-1) were significantly higher in patients with high bone disease as compared with patients with low bone disease. Moreover, CCL20 BM levels were significant predictors of osteolysis on X-rays by multivariate logistic analysis. On the other hand, DKK-1 levels were related to the presence of MRI lesions independently of the osteolysis at the X-rays. Our data define the relationship between bone disease and the BM cytokine and chemokine patterns highlighting the tight relationship between CCL20 BM levels and osteolysis in MM.

Pulmonary hypertension complicating multiple myeloma

Pulmonary hypertension (PH) is an infrequently reported complication of multiple myeloma (MM). PH has been more commonly associated with amyloidosis, myeloproliferative diseases, and the POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, skin changes) syndrome. PH in MM is typically mild to moderate and may be secondary to a variety of conditions, which include left ventricular dysfunction, high-output cardiac failure, chronic kidney disease, treatment-related toxicities, and precapillary involvement. We describe 3 patients with MM and severe PH. Each patient underwent right heart catheterization. All patients demonstrated elevated pulmonary pressures, transpulmonary gradients, and pulmonary vascular resistance. Each patient was ultimately treated with pulmonary vasodilator therapy with improvement in cardiopulmonary symptoms. Additional studies are needed to define the prevalence, prognosis, and pathogenesis of PH in this complex population and to help clarify who may benefit from targeted PH therapy.

Anergic bone marrow Vγ9Vδ2 T cells as early and long-lasting markers of PD-1-targetable microenvironment-induced immune suppression in human myeloma

Vγ9Vδ2 T cells have a natural inclination to recognize malignant B cells in vitro via receptors for stress-induced self-ligands and TCR-dependent recognition of phosphoantigens (pAgs) generated in the mevalonate (Mev) pathway. This inclination is continuously challenged in vivo by the immune suppression operated by tumor cells. Multiple myeloma (MM) is a prototypic B-cell malignancy in which myeloma cells subvert the local microenvironment to reshape antitumor immune responses. In this study, we have investigated the immune competence of bone marrow (BM) Vγ9Vδ2 T cells in a large series of MM patients. We have found that the BM microenvironment significantly hampers the pAg-reactivity of BM Vγ9Vδ2 T cells, which become largely PD-1⁺ and are surrounded by PD-L1⁺ myeloma cells and increased numbers of PD-L1⁺ myeloid-derived suppressor cells (MDSC). Vγ9Vδ2 T-cell dysfunction is an early event that can be already detected in individuals with monoclonal gammopathy of undetermined significance (MGUS) and not fully reverted even when MM patients achieve clinical remission. Anti-PD-1 treatment increases the cytotoxic potential of Vγ9Vδ2 T cells by almost 5-fold after pAg stimulation, and appears to be a promising strategy for effective immune interventions in MM.

IL10 receptor is a novel therapeutic target in DLBCLs

Diffuse large B-cell lymphoma (DLBCL) is a biologically and clinically heterogeneous disease with marked genomic instability and variable response to conventional R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone) chemotherapy. More clinically aggressive cases of DLBCLs have high level of circulating interleukin 10 (IL10) cytokine and evidence of activated intracellular STAT3 (signal transducer and activator of transcription 3) signaling. We investigated the role of IL10 and its surface receptor in supporting the neoplastic phenotype of DLBCLs. We determined that IL10RA gene is amplified in 21% and IL10RB gene in 10% of primary DLBCLs. Gene expression of IL10, IL10RA and IL10RB was markedly elevated in DLBCLs. We hypothesized that DLBCLs depend for their proliferation and survival on IL10-STAT3 signaling and that blocking the IL10 receptor (IL10R) would induce cell death. We used anti-IL10R blocking antibody, which resulted in a dose-dependent cell death in all tested activated B-cell-like subtype of DLBCL cell lines and primary DLBCLs. Response of germinal center B-cell-like subtype of DLBCL cell lines to anti-IL10R antibody varied from sensitive to resistant. Cells underwent cell cycle arrest, followed by induction of apoptosis. Cell death depended on inhibition of STAT3 and, to a lesser extent, STAT1 signaling. Anti-IL10R treatment resulted in interruption of IL10-IL10R autostimulatory loop. We thus propose that IL10R is a novel therapeutic target in DLBCLs.

Dkk-1 and IL-7 in plasma of patients with multiple myeloma prevent differentiation of mesenchymal stem cells into osteoblasts

Bone disease is the leading cause of morbidity associated with multiple myeloma (MM). Lytic bone lesions have been detected in 90% of patients diagnosed with MM and present a great therapeutic challenge. After the removal of the tumor burden, the bone lesions persist and the bone remodeling homeostasis is not restored even in patients in clinical remission. To determine whether systemic factors generated by malignant MM cells can skew the osteoblast (OB) differentiation program of normal mesenchymal stem cells (MSCs), we generated an immortalized bone marrow MSC line (hTERT-MSC). The hTERT-MSCs were exposed to plasma from healthy donors and patients with MM. Cells grown in media supplemented with plasma from MM patients failed to differentiate into OBs, while the hTERT-MSCs grown in the presence of normal human plasma generated OB clusters that mineralized calcium, expressed Runx2, and were positive for alkaline phosphatase, fibronectin, collagen I, osteocalcin, and osteopontin. Blocking Dickkopf-1 (Dkk-1) and interleukin-7 (IL-7) in MM plasma restored proper OB differentiation of hTERT-MSCs. Finally, we show that hTERT-MSCs cultured in the presence of MM plasma adopt a cancer-associated stroma phenotype. Thus, we show, that systemic factors present in the plasma of patients with MM affect the behavior of non-malignant MSCs and contribute to the sustained bone disease reported in MM.

Myeloid-derived suppressor cells in multiple myeloma: pre-clinical research and translational opportunities

Immunosuppressive cells have been reported to play an important role in tumor-progression mainly because of their capability to promote immune-escape, angiogenesis, and metastasis. Among them, myeloid-derived suppressor cells (MDSCs) have been recently identified as immature myeloid cells, induced by tumor-associated inflammation, able to impair both innate and adaptive immunity. While murine MDSCs are usually identified by the expression of CD11b and Gr1, human MDSCs represent a more heterogeneous population characterized by the expression of CD33 and CD11b, low or no HLA-DR, and variable CD14 and CD15. In particular, the last two may alternatively identify monocyte-like or granulocyte-like MDSC subsets with different immunosuppressive properties. Recently, a substantial increase of MDSCs has been found in peripheral blood and bone marrow (BM) of multiple myeloma (MM) patients with a role in disease progression and/or drug resistance. Pre-clinical models recapitulating the complexity of the MM-related BM microenvironment (BMM) are major tools for the study of the interactions between MM cells and cells of the BMM (including MDSCs) and for the development of new agents targeting MM-associated immune-suppressive cells. This review will focus on current strategies for human MDSCs generation and investigation of their immunosuppressive function in vitro and in vivo, taking into account the relevant relationship occurring within the MM–BMM. We will then provide trends in MDSC-associated research and suggest potential application for the treatment of MM.

Identification of proteins found to be significantly altered when comparing the serum proteome from Multiple Myeloma patients with varying degrees of bone disease

Background

Bone destruction is a feature of multiple myeloma, characterised by osteolytic bone destruction due to increased osteoclast activity and suppressed or absent osteoblast activity. Almost all multiple myeloma patients develop osteolytic bone lesions associated with severe and debilitating bone pain, pathologic fractures, hypercalcemia, and spinal cord compression, as well as increased mortality. Biomarkers of bone remodelling are used to identify disease characteristics that can help select the optimal management of patients. However, more accurate biomarkers are needed to effectively mirror the dynamics of bone disease activity.

Results

A label-free mass spectrometry-based strategy was employed for discovery phase analysis of fractionated patient serum samples associated with no or high bone disease. A number of proteins were identified which were statistically significantly correlated with bone disease, including enzymes, extracellular matrix glycoproteins, and components of the complement system.

Conclusions

Enzyme-linked immunosorbent assay of complement C4 and serum paraoxonase/arylesterase 1 indicated that these proteins were associated with high bone disease in a larger independent cohort of patient samples. These biomolecules may therefore be clinically useful in assessing the extent of bone disease.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-904) contains supplementary material, which is available to authorized users.

The bone marrow of myeloma patients is steadily inhabited by a normal-sized pool of functional regulatory T cells irrespectiveof the disease status

Conflicting data have been reported about the frequency and function of regulatory T cells in multiple myeloma. Most studies have investigated peripheral blood rather than bone marrow Tregs and side-by-side comparisons with bone marrow from healthy donors have still not been made. In this study, we show that regulatory T-cells total count, subset distribution, and expression of chemokine receptors are similar in the bone marrow of myeloma patients and healthy donors. Regulatory T cells are not recruited by myeloma cells in the bone marrow and their counts are unaffected by the tumor burden and the disease status. The diversity of T-cell receptor repertoire is highly preserved ensuring broad reactivity and effective suppressor function. Our results indicate that regulatory T cells may not be the main players of immunological tolerance to myeloma cells under base-line conditions, but their fully preserved immune competence may promote their inadvertent activation and blunt T-cell driven anti-myeloma immune interventions even after myeloma cells have successfully been cleared by chemotherapy.