Natural killer T cell defects in multiple myeloma and the impact of lenalidomide therapy

Obesity as a risk factor for multiple myeloma: insight on the role of adipokines

Multiple myeloma (MM) is a hematologic disorder characterized by the accumulation of malignant plasma cells in the bone marrow. Genetic and environmental factors are contributed to the etiology of MM. Notably, studies have shown that obesity increases the risk of MM and worsens outcomes for MM patients. Adipokines play an important role in mediating the close association between MM and metabolic derangements. In this review, we summarize the epidemiologic studies to show that the risk of MM is increased in obese. Accumulating clinical evidence suggests that adipokines could display a correlation with MM. In vitro and in vivo studies have shown that adipokines are linked to MM, including roles in the biological behavior of MM cells, cancer-associated bone loss, the progression of MM, and drug resistance. Current and potential therapeutic strategies targeted to adipokines are discussed, proposing that adipokines can guide early patient diagnosis and treatment.

Single-cell technologies in multiple myeloma: new insights into disease pathogenesis and translational implications

Multiple myeloma (MM) is a hematological malignancy characterized by clonal proliferation of plasma cells. Although therapeutic advances have been made to improve clinical outcomes and to prolong patients' survival in the past two decades, MM remains largely incurable. Single-cell sequencing (SCS) is a powerful method to dissect the cellular and molecular landscape at single-cell resolution, instead of providing averaged results. The application of single-cell technologies promises to address outstanding questions in myeloma biology and has revolutionized our understanding of the inter- and intra-tumor heterogeneity, tumor microenvironment, and mechanisms of therapeutic resistance in MM. In this review, we summarize the recently developed SCS methodologies and latest MM research progress achieved by single-cell profiling, including information regarding the cancer and immune cell landscapes, tumor heterogeneities, underlying mechanisms and biomarkers associated with therapeutic response and resistance. We also discuss future directions of applying transformative SCS approaches with contribution to clinical translation.

Improving NK cell function in multiple myeloma with NKTR-255, a novel polymer-conjugated human IL-15

Multiple myeloma (MM) is characterized by an immunosuppressive microenvironment that enables tumor development. One of the mechanisms of immune evasion used by MM cells is the inhibition of natural killer (NK) cell effector functions; thus, the restoration of NK cell antitumor activity represents a key goal to increase tumor cell recognition, avoid tumor escape and potentially enhancing the effect of other drugs. In this study, we evaluated the ability of the investigational medicine NKTR-255, an IL-15 receptor agonist, to engage the IL-15 pathway and stimulate NK cells against MM cells. We observed that incubation with NKTR-255 was able to tilt the balance toward an activated phenotype in NK cells isolated from peripheral blood mononuclear cells of patients with MM, with increased expression of activating receptors on the surface of treated NK cells. This resulted in an enhanced degranulation, cytokine release, and anti-tumor cytotoxicity when the NK cells were exposed to both MM cell lines and primary MM cells. We further evaluated the in vivo effect of NKTR-255 in fully humanized immunocompetent mice subcutaneously engrafted with H929 MM cells. Compared with placebo, weekly injection of the mice with NKTR-255 increased the number of circulating NK cells in peripheral blood and delayed tumor growth. Finally, we observed that combination of NKTR-255 with the anti-CD38 antibody, daratumumab, was effective against MM cells in vitro and in vivo. Taken together, our data suggest a significant impact of NKTR-255 in inducing NK cell function against MM cells with important translational implications.

CAR-T cell therapy in multiple myeloma: Current limitations and potential strategies

Over the last decade, the survival outcome of patients with multiple myeloma (MM) has been substantially improved with the emergence of novel therapeutic agents, such as proteasome inhibitors, immunomodulatory drugs, anti-CD38 monoclonal antibodies, selective inhibitors of nuclear export (SINEs), and T cell redirecting bispecific antibodies. However, MM remains an incurable neoplastic plasma cell disorder, and almost all MM patients inevitably relapse due to drug resistance. Encouragingly, B cell maturation antigen (BCMA)-targeted chimeric antigen receptor T (CAR-T) cell therapy has achieved impressive success in the treatment of relapsed/refractory (R/R) MM and brought new hopes for R/R MM patients in recent years. Due to antigen escape, the poor persistence of CAR-T cells, and the complicated tumor microenvironment, a significant population of MM patients still experience relapse after anti-BCMA CAR-T cell therapy. Additionally, the high manufacturing costs and time-consuming manufacturing processes caused by the personalized manufacturing procedures also limit the broad clinical application of CAR-T cell therapy. Therefore, in this review, we discuss current limitations of CAR-T cell therapy in MM, such as the resistance to CAR-T cell therapy and the limited accessibility of CAR-T cell therapy, and summarize some optimization strategies to overcome these challenges, including optimizing CAR structure, such as utilizing dual-targeted/multi-targeted CAR-T cells and armored CAR-T cells, optimizing manufacturing processes, combing CAR-T cell therapy with existing or emerging therapeutic approaches, and performing subsequent anti-myeloma therapy after CAR-T cell therapy as salvage therapy or maintenance/consolidation therapy.

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.

Absolute Lymphocyte Counts After Lenalidomide Initiation may Predict the Prognosis of Patients With Relapsed or Refractory Multiple Myeloma

BACKGROUND/AIM

We assessed the prognosis of patients with refractory or relapsed multiple myeloma (RRMM) by focusing on the change in absolute lymphocyte counts (ALCs) after lenalidomide and dexamethasone (Ld) initiation.

PATIENTS AND METHODS

In total, 72 patients with RRMM were treated with Ld. ALCs were evaluated before treatment and at 1, 2, and 3 months after Ld initiation. The median ALCs in the entire cohort before and at 1, 2, 3 months after Ld initiation were 1,131, 1,059, 1,222, and 1,162/μl, respectively.

RESULTS

ALCs before Ld initiation did not affect time to next treatment (TNT) or overall survival (OS). However, the patients with ALCs equal to or greater than the median at 3 months showed relatively better TNT than those with lower lymphocyte counts, with a significant difference. OS was also significantly longer in patients with higher ALCs.

CONCLUSION

Immunomodulation by lenalidomide may improve prognosis in patients with RRMM.

Understanding the Role of T-Cells in the Antimyeloma Effect of Immunomodulatory Drugs

Immunomodulatory drugs (IMiDs) are effective treatments for patients with multiple myeloma. IMiDs have pleotropic effects including targeting the myeloma cells directly, and improving the anti-myeloma immune response. In the absence of myeloma cells, lenalidomide and pomalidomide induce CD4⁺ T cell secretion of IL-2 and indirect activation of Natural Killer (NK) cells. In the context of T cell receptor ligation, IMiDs enhance T cell proliferation, cytokine release and Th1 responses, both in vivo and in vitro. Furthermore, combination treatment of IMiDs and myeloma-targeting monoclonal antibodies eg. daratumumab (anti-CD38) and elotuzumab (anti-SLAMF7), checkpoint inhibitors, or bispecific T cell engagers showed synergistic effects, mainly via enhanced T and NK cell dependent cellular toxicity and T cell proliferation. Conversely, the corticosteroid dexamethasone can impair the immune modulatory effects of IMiDs, indicating that careful choice of myeloma drugs in combination with IMiDs is key for the best anti-myeloma therapeutic efficacy. This review presents an overview of the role for T cells in the overall anti-myeloma effects of immunomodulatory drugs.

Co-evolution of Immune Response in Multiple Myeloma: Implications for Immune Prevention

Multiple myeloma (MM), a malignant neoplasm of plasma cells that reside in the bone marrow (BM), is universally preceded by a precursor state termed monoclonal gammopathy of undetermined significance (MGUS). Many individuals with MGUS never progress to MM or progress over many years. Therefore, MGUS provides a unique opportunity to surveil changes in the BM tumor microenvironment throughout disease progression. It is increasingly appreciated that MGUS cells carry many of the genetic changes found in MM. Prior studies have also shown that MGUS cells can be recognized by the immune system, leading to early changes in the BM immune environment compared to that of healthy individuals, including alterations in both innate and adaptive immunity. Progression to clinical MM is associated with attrition of T cells with stem memory-like features and instead accumulation of T cells with more terminally differentiated features. Recent clinical studies have suggested that early application of immune-modulatory drugs, which are known to activate both innate and adaptive immunity, can delay the progression to clinical MM. Understanding the biology of how the immune response and tumors coevolve over time is needed to develop novel immune-based approaches to achieve durable and effective prevention of clinical malignancy.

Preclinical Evaluation of Invariant Natural Killer T Cells Modified with CD38 or BCMA Chimeric Antigen Receptors for Multiple Myeloma

Due to the CD1d restricted recognition of altered glycolipids, Vα24-invariant natural killer T (iNKT) cells are excellent tools for cancer immunotherapy with a significantly reduced risk for graft-versus-host disease when applied as off-the shelf-therapeutics across Human Leukocyte Antigen (HLA) barriers. To maximally harness their therapeutic potential for multiple myeloma (MM) treatment, we here armed iNKT cells with chimeric antigen receptors (CAR) directed against the MM-associated antigen CD38 and the plasma cell specific B cell maturation antigen (BCMA). We demonstrate that both CD38- and BCMA-CAR iNKT cells effectively eliminated MM cells in a CAR-dependent manner, without losing their T cell receptor (TCR)-mediated cytotoxic activity. Importantly, iNKT cells expressing either BCMA-CARs or affinity-optimized CD38-CARs spared normal hematopoietic cells and displayed a Th1-like cytokine profile, indicating their therapeutic utility. While the costimulatory domain of CD38-CARs had no influence on the cytotoxic functions of iNKT cells, CARs containing the 4-1BB domain showed a better expansion capacity. Interestingly, when stimulated only via CD1d+ dendritic cells (DCs) loaded with α-galactosylceramide (α-GalCer), both CD38- and BCMA-CAR iNKT cells expanded well, without losing their CAR- or TCR-dependent cytotoxic activities. This suggests the possibility of developing an off-the-shelf therapy with CAR iNKT cells, which might even be boostable in vivo by administration α-GalCer pulsed DCs.

Actors on the Scene: Immune Cells in the Myeloma Niche

Two mechanisms are involved in the immune escape of cancer cells: the immunoediting of tumor cells and the suppression of the immune system. Both processes have been revealed in multiple myeloma (MM). Complex interactions between tumor plasma cells and the bone marrow (BM) microenvironment contribute to generate an immunosuppressive milieu characterized by high concentration of immunosuppressive factors, loss of effective antigen presentation, effector cell dysfunction, and expansion of immunosuppressive cell populations, such as myeloid-derived suppressor cells, regulatory T cells and T cells expressing checkpoint molecules such as programmed cell death 1. Considering the great immunosuppressive impact of BM myeloma microenvironment, many strategies to overcome it and restore myeloma immunosurveillance have been elaborated. The most successful ones are combined approaches such as checkpoint inhibitors in combination with immunomodulatory drugs, anti-monoclonal antibodies, and proteasome inhibitors as well as chimeric antigen receptor (CAR) T cell therapy. How best to combine anti-MM therapies and what is the optimal timing to treat the patient are important questions to be addressed in future trials. Moreover, intratumor MM heterogeneity suggests the crucial importance of tailored therapies to identify patients who might benefit the most from immunotherapy, reaching deeper and more durable responses.

T-Cell Large Granular Lymphocytic Leukemia with Extremely Rare Immunophenotype (CD4/CD8 Double-Positive) Followed by Multiple Myeloma Diagnosis

T-cell large granular lymphocytic leukemia is characterized by clonal expansion of a CD3⁺/CD57⁺ subpopulation, which are typically CD8⁺ positive cytotoxic T- cells, and can only be diagnosed if there is a persistent, greater than 6 months, elevation of LGL in the blood (usually 2–20 × 10⁹/L), in the absence of an identifiable cause. T-LGLL has been associated with reactive conditions such as autoimmune diseases and viral infections and has also been reported in association with hematologic and non-hematologic malignancies. We report a case of asymptomatic CD4/CD8 double-positive T-LGLL. Flow cytometry on peripheral blood revealed a subpopulation of CD4/CD8 double-positive T cells expressing CD57 and cTIA. Clonality was established by flow cytometric analysis of T-cell receptor V(â) region repertoire which showed that >70% of the cells failed to express any of the tested V(â) regions. Clonality was further confirmed by PCR with the detection of clonal TCR beta and TCR gamma gene rearrangements. Six months later, she presented with persistent lower back pain and diagnosed with IgG kappa multiple myeloma. CD4/CD8 double-positive T-large granular leukemia is the first case reported in the literature. This rare phenotype is either underreported or a truly rare clinical entity. More studies are warranted to characterize the pathogenesis and clinical characteristics of this group of patients and to further assess the relationship between multiple myeloma and T-LGLL as a cause-and-effect relationship or simply related to the time at which diagnosis has been made.

Single-cell RNA sequencing reveals compromised immune microenvironment in precursor stages of multiple myeloma

Precursor states of Multiple Myeloma (MM) and its native tumor microenvironment need in-depth molecular characterization to better stratify and treat patients at risk. Using single-cell RNA sequencing of bone marrow cells from precursor stages, MGUS and smoldering myeloma (SMM), to full-blown MM alongside healthy donors, we demonstrate early immune changes during patient progression. We find NK cell abundance is frequently increased in early stages, and associated with altered chemokine receptor expression. As early as SMM, we show loss of GrK⁺ memory cytotoxic T-cells, and show their critical role in MM immunosurveillance in mouse models. Finally, we report MHC class II dysregulation in CD14⁺ monocytes, which results in T cell suppression in vitro. These results provide a comprehensive map of immune changes at play over the evolution of pre-malignant MM, which will help develop strategies for immune-based patient stratification.

Navigating the Role of CD1d/Invariant Natural Killer T-cell/Glycolipid Immune Axis in Multiple Myeloma Evolution: Therapeutic Implications

Multiple myeloma (MM) is an incurable B-cell malignancy. The immunotherapeutic approach for MM therapy is evolving. The Cd1d/invariant natural killer T-cell/glycolipid immune axis belongs to the innate immunity, and we have highlighted role in myeloma pathogenesis in the present study. The recent development of the chimeric antigen receptor (CAR19)-invariant natural killer T-cells resulted in our renewed interest in this immune system and offer new perspectives for future anti-MM immunotherapies.

NK and NKT Cell-Mediated Immune Surveillance against Hematological Malignancies

Recent cancer treatment modalities have been intensively focused on immunotherapy. The success of chimeric antigen receptor T cell therapy for treatment of refractory B cell acute lymphoblastic leukemia has pushed forward research on hematological malignancies. Among the effector types of innate lymphocytes, natural killer (NK) cells show great importance in immune surveillance against infectious and tumor diseases. Particularly, the role of NK cells has been argued in either elimination of target tumor cells or escape of tumor cells from immune surveillance. Therefore, an NK cell activation approach has been explored. Recent findings demonstrate that invariant natural killer T (iNKT) cells capable of producing IFN-γ when optimally activated can promptly trigger NK cells. Here, we review the role of NKT and/or NK cells and their interaction in anti-tumor responses by highlighting how innate immune cells recognize tumors, exert effector functions, and amplify adaptive immune responses. In addition, we discuss these innate lymphocytes in hematological disorders, particularly multiple myeloma and acute myeloid leukemia. The immune balance at different stages of both diseases is explored in light of disease progression. Various types of innate immunity-mediated therapeutic approaches, recent advances in clinical immunotherapies, and iNKT-mediated cancer immunotherapy as next-generation immunotherapy are then discussed.

Trabectedin triggers direct and NK-mediated cytotoxicity in multiple myeloma

BACKGROUND

Genomic instability is a feature of multiple myeloma (MM), and impairment in DNA damaging response (DDR) has an established role in disease pathobiology. Indeed, a deregulation of DNA repair pathways may contribute to genomic instability, to the establishment of drug resistance to genotoxic agents, and to the escape from immune surveillance. On these bases, we evaluated the role of different DDR pathways in MM and investigated, for the first time, the direct and immune-mediated anti-MM activity of the nucleotide excision repair (NER)-dependent agent trabectedin.

METHODS

Gene-expression profiling (GEP) was carried out with HTA2.0 Affymetrix array. Evaluation of apoptosis, cell cycle, and changes in cytokine production and release have been performed in 2D and 3D Matrigel-spheroid models through flow cytometry on MM cell lines and patients-derived primary MM cells exposed to increasing nanomolar concentrations of trabectedin. DNA-damage response has been evaluated through Western blot, immunofluorescence, and DNA fragmentation assay. Trabectedin-induced activation of NK has been assessed by CD107a degranulation. miRNAs quantification has been done through RT-PCR.

RESULTS

By comparing GEP meta-analysis of normal and MM plasma cells (PCs), we observed an enrichment in DNA NER genes in poor prognosis MM. Trabectedin triggered apoptosis in primary MM cells and MM cell lines in both 2D and 3D in vitro assays. Moreover, trabectedin induced DDR activation, cellular stress with ROS production, and cell cycle arrest. Additionally, a significant reduction of MCP1 cytokine and VEGF-A in U266-monocytes co-cultures was observed, confirming the impairment of MM-promoting milieu. Drug-induced cell stress in MM cells led to upregulation of NK activating receptors ligands (i.e., NKG2D), which translated into increased NK activation and degranulation. Mechanistically, this effect was linked to trabectedin-induced inhibition of NKG2D-ligands negative regulators IRF4 and IKZF1, as well as to miR-17 family downregulation in MM cells.

CONCLUSIONS

Taken together, our findings indicate a pleiotropic activity of NER-targeting agent trabectedin, which appears a promising candidate for novel anti-MM therapeutic strategies.

Impact of lenalidomide maintenance on the immune environment of multiple myeloma patients with low tumor burden after autologous stem cell transplantation

Lenalidomide is a potent anti-myeloma drug with immunomodulatory properties. It is increasingly used in a low-dose maintenance setting to prolong remission duration after standard treatment. Data on the in vivo effects of lenalidomide are scarce and sometimes different from the well-described in vitro effects. We therefore evaluated the numerical, phenotypical and functional impact of lenalidomide maintenance on several immune cell types in a cohort of seventeen homogeneously treated myeloma patients achieving a low residual myeloma burden after a bortezomib based-induction followed by autologous stem cell transplantation. Lenalidomide maintenance: 1) increased the fraction of naïve CD8⁺ T cells and several memory T-cell subsets, 2) reduced the numbers of terminal effector CD8⁺ T cells, 3) resulted in a higher expression of co-stimulatory molecules on resting T cells and of the inhibitory checkpoint molecules LAG-3 on CD4⁺ T cells and TIM-3 on CD4⁺ and CD8⁺ T cells, 4) reduced the number of TIGIT⁺ CD8⁺ T cells, 5) increased the number of regulatory T cells with a phenotype associated with strong suppressive capacity. Purified CD8⁺ T cells showed increased and more polyfunctional recall viral responses. However, PBMC responses were not enhanced during lenalidomide maintenance and CD4⁺ T-cell responses specific for the myeloma-associated antigen MAGE-C1 even tended to become lower. We conclude that lenalidomide maintenance after autologous stem cell transplantation has complex pleotropic effects on the immune environment. Immune interventions such as anti-myeloma vaccination should include measures to tackle an expanded inhibitory Treg compartment.

Enumeration, functional responses and cytotoxic capacity of MAIT cells in newly diagnosed and relapsed multiple myeloma

Mucosal-associated invariant T (MAIT) cells are T cells that recognise vitamin-B derivative Ag presented by the MHC-related-protein 1 (MR1) antigen-presenting molecule. While MAIT cells are highly abundant in humans, their role in tumour immunity remains unknown. Here we have analysed the frequency and function of MAIT cells in multiple myeloma (MM) patients. We show that MAIT cell frequency in blood is reduced compared to healthy adult donors, but comparable to elderly healthy control donors. Furthermore, there was no evidence that MAIT cells accumulated at the disease site (bone marrow) of these patients. Newly diagnosed MM patient MAIT cells had reduced IFNγ production and CD27 expression, suggesting an exhausted phenotype, although IFNγ-producing capacity is restored in relapsed/refractory patient samples. Moreover, immunomodulatory drugs Lenalidomide and Pomalidomide, indirectly inhibited MAIT cell activation. We further show that cell lines can be pulsed with vitamin-B derivative Ags and that these can be presented via MR1 to MAIT cells in vitro, to induce cytotoxic activity comparable to that of natural killer (NK) cells. Thus, MAIT cells are reduced in MM patients, which may contribute to disease in these individuals, and moreover, MAIT cells may represent new immunotherapeutic targets for treatment of MM and other malignancies.

Deficient invariant natural killer T cells had impaired regulation on osteoclastogenesis in myeloma bone disease

Recent research showed that invariant natural killer T (iNKT) cells take part in the regulation of osteoclastogenesis. While the role of iNKT cells in myeloma bone disease (MBD) remains unclear. In our study, the quantity of iNKT cells and the levels of cytokines produced by them were measured by flow cytometry. iNKT cells and osteoclasts were induced from peripheral blood mononuclear cells after activation by α‐GalCer or RANKL in vitro. Then, gene expressions and the levels of cytokines were determined by RT‐PCR and ELISA, respectively. The results showed that the quantity of iNKT and production of IFN‐γ by iNKT cells were significantly decreased in newly diagnosed MM (NDMM), and both negatively related with severity of bone disease. Then, the osteoclasts from healthy controls were cultured in vitro and were found to be down‐regulated after α‐GalCer‐stimulated, while there was no significant change with or without α‐GalCer in NDMM patients, indicating that the regulation of osteoclastogenesis by iNKT cells was impaired. Furthermore, the inhibition of osteoclastogenesis by iNKT cells was regulated by IFN‐γ production, which down‐regulated osteoclast‐associated genes. In conclusion, the role of α‐GalCer‐stimulated iNKT cells in regulation of osteoclastogenesis was impaired in MBD, as a result of iNKT cell dysfunction.

Invariant Natural Killer T Cells in Immune Regulation of Blood Cancers: Harnessing Their Potential in Immunotherapies

Invariant natural killer T (iNKT) cells are a unique innate T lymphocyte population that possess cytolytic properties and profound immunoregulatory activities. iNKT cells play an important role in the immune surveillance of blood cancers. They predominantly recognize glycolipid antigens presented on CD1d, but their activation and cytolytic activities are not confined to CD1d expressing cells. iNKT cell stimulation and subsequent production of immunomodulatory cytokines serve to enhance the overall antitumor immune response. Crucially, the activation of iNKT cells in cancer often precedes the activation and priming of other immune effector cells, such as NK cells and T cells, thereby influencing the generation and outcome of the antitumor immune response. Blood cancers can evade or dampen iNKT cell responses by downregulating expression of recognition receptors or by actively suppressing or diverting iNKT cell functions. This review will discuss literature on iNKT cell activity and associated dysregulation in blood cancers as well as highlight some of the strategies designed to harness and enhance iNKT cell functions against blood cancers.

Activation of NK cells and disruption of PD-L1/PD-1 axis: two different ways for lenalidomide to block myeloma progression

Natural Killer (NK) cells play a critical role against tumor cells in hematological malignancies. Their activating receptors are essential in tumor cell killing. In Multiple Myeloma (MM) patients, NK cell differentiation, activation and cytotoxic potential are strongly impaired leading to MM escape from immune surveillance in tissues and bone marrow. Mechanisms used by MM to affect NK cell functions are mediated by the release of soluble factors, the expression of activating and inhibitory NK cell ligands, and the expression of immune check-point inhibitors. Lenalidomide represents an efficient clinical approach in MM treatment to improve patients' survival. Lenalidomide does not only promotes tumor apoptosis, but also stimulates T and NK cells, thereby facilitating NK-mediated tumor recognition and killing. This occurs since Lenalidomide acts on several critical points: stimulates T cell proliferation and cytokine secretion; decreases the expression of the immune check-point inhibitor Programmed Death-1 (PD-1) on both T and NK cells in MM patients; decreases the expression of both PD-1 and PD-L1 on MM cells; promotes MM cell death and abrogates MM/stromal microenvironment cross-talk, a process known to promote the MM cell survival and proliferation. This leads to the inhibition of the negative signal induced by PD-1/PD-L1 axis on NK cells, restoring NK cell cytotoxic functions. Given the importance of an effective immune response to counteract the MM progression and the promising approaches using anti-PD-1/PD-L1 strategies, we will discuss in this review how Lenalidomide could represent an adequate approach to re-establish the recognition against MM by exhausted NK cell.

Leptin receptor antagonism of iNKT cell function: a novel strategy to combat multiple myeloma

A hallmark of bone marrow changes with aging is the increase in adipocyte composition, but how this impacts development of multiple myeloma (MM) is unknown. Here, we report the role of the adipokine leptin as master regulator of anti-myeloma tumor immunity by modulating the invariant natural killer T (iNKT) cell function. A marked increase in serum leptin levels and leptin receptor (LR) expression on iNKT cells in MM patients and the 5T33 murine MM model was observed. MM cells and leptin synergistically counteracted anti-tumor functionality of both murine and human iNKT cells. In vivo blockade of LR signaling combined with iNKT stimulation resulted in superior anti-tumor protection. This was linked to persistent IFN-γ secretion upon repeated iNKT cell stimulation and a restoration of the dynamic antigen-induced motility arrest as observed by intravital microscopy, thereby showing alleviation of iNKT cell anergy. Overall our data reveal the LR axis as novel therapeutic target for checkpoint inhibition to treat MM.

A phase 1b study of isatuximab plus lenalidomide and dexamethasone for relapsed/refractory multiple myeloma

This phase 1b, open-label, dose-escalation study assessed the safety, efficacy, and pharmacokinetics of anti-CD38 monoclonal antibody isatuximab given in 2 schedules (3, 5, or 10 mg/kg every other week [Q2W] or 10 or 20 mg/kg weekly [QW] for 4 weeks and then Q2W thereafter [QW/Q2W]), in combination with lenalidomide 25 mg (days 1-21) and dexamethasone 40 mg (QW), in patients with relapsed/refractory multiple myeloma (RRMM). Patients received 28-day treatment cycles; the primary objective was to determine the maximum tolerated dose (MTD) of isatuximab with lenalidomide and dexamethasone. Fifty-seven patients (median 5 [range 1-12] prior regimens; 83% refractory to previous lenalidomide therapy) were treated. Median duration of dosing was 36.4 weeks; 15 patients remained on treatment at data cutoff. Isatuximab-lenalidomide-dexamethasone was generally well tolerated with only 1 dose-limiting toxicity reported (grade 3 pneumonia at 20 mg/kg QW/Q2W); the MTD was not reached. The most common isatuximab-related adverse events were infusion-associated reactions (IARs) (56%), which were grade 1/2 in 84% of patients who had an IAR and predominantly occurred during the first infusion. In the efficacy-evaluable population, the overall response rate (ORR) was 56% (29/52) and was similar between the 10 mg/kg Q2W and 10 and 20 mg/kg QW/Q2W cohorts. The ORR was 52% in 42 evaluable lenalidomide-refractory patients. Overall median progression-free survival was 8.5 months. Isatuximab exposure increased in a greater than dose-proportional manner; isatuximab and lenalidomide pharmacokinetic parameters appeared independent. These data suggest that isatuximab combined with lenalidomide and dexamethasone is active and tolerated in heavily pretreated patients with RRMM. This trial was registered at www.clinicaltrials.gov as #NCT01749969.

The T Cell in Myeloma

An active role for the immune system in controlling the malignant plasma cell clone in myeloma has been postulated for many years. The clinical states of monoclonal gammopathy of undetermined significance, plateau phase disease, and smoldering myeloma all suggest that a significant host-tumor interaction is taking place. The fundamental role of the cytotoxic T cell in tumor elimination and control has been exemplified by the dramatic efficacy of adoptive T-cell therapies in many hemopoietic malignancies. However, tumor-host cross-talk results in suppression of the endogenous cytotoxic T-cell response against the malignant plasma cell. Whereas patients with myeloma do not clinically exhibit a T-cell immunodeficiency state, with, for example, increased mycobacterial infections, a number of abnormalities of T-cell function are evident. The major abnormalities of T cells include clonal expansions and associated immunosenescence, alterations of regulatory T cells/T helper 17 cells (Treg/Th17 ratio) and acquired membrane abnormalities, due to trogocytosis, which result in acquired Treg cells. Dendritic cell dysfunction associated with impaired antigen processing and presentation caused by abnormalities of the bone marrow microenvironment plays an additional role. In this perspective, we examine the T-cell abnormalities in myeloma and postulate that, whereas cytotoxic T cells interacting with the tumor are dysfunctional, residual T cells still function adequately against external pathogens and thus protect patients from the infections normally associated with a generalized T-cell immunodeficiency state. The so-called 3 E's of host-tumor interaction (elimination, equilibrium, and escape) are clearly reflected in the immune landscape and clinical behavior of myeloma.

Circulating immune cell phenotype can predict the outcome of lenalidomide plus low-dose dexamethasone treatment in patients with refractory/relapsed multiple myeloma

Although the antimyeloma effect of lenalidomide is associated with activation of the immune system, the exact in vivo immunomodulatory mechanisms of lenalidomide combined with low-dose dexamethasone (Len-dex) in refractory/relapsed multiple myeloma (RRMM) patients remain unclear. In this study, we analyzed the association between immune cell populations and clinical outcomes in patients receiving Len-dex for the treatment of RRMM. Peripheral blood samples from 90 RRMM patients were taken on day 1 of cycles 1 (baseline), 2, 3, and 4 of Len-dex therapy. Peripheral blood CD3(+), CD4(+), and CD8(+) cell frequencies were significantly decreased by 3 cycles of therapy, whereas NK cell frequency was significantly increased after the 3rd cycle. For the myeloid-derived suppressor cell (MDSC) subset, the frequency of granulocytic MDSCs transiently increased after the 1st cycle, whereas there was an increase in monocytic MDSC (M-MDSC) frequency after the 1st and 3rd cycles. Among 81 evaluable patients, failure to achieve a response of VGPR or greater was associated with a decrease in CD8(+) cell frequency and increase in M-MDSC frequency after 3 cycles of Len-dex treatment. A high proportion of natural killer T (NKT)-like cells (CD3(+)/CD56(+)) prior to Len-dex treatment might predict a longer time to progression. In addition, patients with a smaller decrease in the frequency of both CD3(+) cells and CD8(+) cells by 3 cycles exhibited a longer time to the next treatment. These results demonstrated that early changes in immune cell subsets are useful immunologic indicators of the efficacy of Len-dex treatment in RRMM.

Lenalidomide enhances myeloma-specific T-cell responses in vivo and in vitro

Immunomodulation is an important part of lenalidomide's mode of action. We analyzed the impact of lenalidomide on T cells from patients with multiple myeloma during lenalidomide therapy in vivo and in patients with lenalidomide-refractory disease in vitro Patients enrolled in the German Speaking Myeloma Multicenter Group (GMMG) MM5 trial received a consolidation therapy with two cycles of lenalidomide after autologous stem cell transplantation (ASCT). Half of the study population continued treatment with lenalidomide maintenance therapy for 2 y, while the other patients received lenalidomide maintenance therapy until complete remission. We analyzed 58 patients with (n = 30) or without (n = 28) lenalidomide therapy and 12 patients refractory to lenalidomide with regards to their anti-myeloma-specific T-cell responses displayed by IFNγ, Granzyme B, and Perforin secretion. The immunophenotype of T-cells was investigated by flow cytometry. Significantly, more myeloma-specific T-cell responses were observed in patients during lenalidomide therapy, compared to patients without treatment. Furthermore, we found on T-cells from patients treated with lenalidomide a decreased CD45RA expression, indicating a maturated immunophenotype and a decreased expression of CD57, indicating functional T cells. An improved myeloma-specific T-cell response was observed in 6 out of 12 heavily pretreated patients (refractory to lenalidomide) after in vitro incubation with lenalidomide. Complementary to the results in vivo, lenalidomide decreased CD45RA expression on T cells in vitro.

A case of refractory multiple myeloma with proliferation of large granular lymphocytes by lenalidomide treatment and its association with clinical efficacy

A 72-year-old Japanese male was diagnosed as having monoclonal gammopathy of undetermined significance and was followed up without therapy. Three years later, the patient progressed to symptomatic multiple myeloma. Melphalan + prednisolone was administered as first-line chemotherapy for ~6 years. Since the patient was judged to exhibit refractory multiple myeloma, he subsequently received radiation therapy on the lumbar spine. The patient was enrolled in a clinical trial and received lenalidomide + lowdose dexamethasone (Rd) therapy. The patient achieved very good partial remission following four cycles of Rd. At this time, large granular lymphocytes (LGLs) increased to 25-40% of peripheral blood leukocytes, however, the LGLs were present in the blood (~8%) prior to lenalidomide treatment. By flow cytometry of surface antigens, it was revealed that the LGLs were positive for cluster of differnetiation (CD)2, 7, 8, 16, 56, and 57, and human leukocyte antigen-D related, however, were negative for CD3, 4 and 5, suggesting that these LGLs predominantly exhibited an natural killer (NK) cell phenotype. T-cell receptor β gene rearrangement was not detected by polymerase chain reaction. A ⁵¹Cr release assay was performed to investigate whether the NK cells actually possessed activity. A low level of M protein was sustained for ~15 months. This implied the enhancement of immune activation during lenalidomide treatment. The present case study suggested that LGL cells induced by lenalidomide may contribute to long-term restraint of myeloma cells. This immune system component may contribute to disease control.

Regulation of NKT Cell Localization in Homeostasis and Infection

Natural killer T (NKT) cells are a specialized subset of T lymphocytes that regulate immune responses in the context of autoimmunity, cancer, and microbial infection. Lipid antigens derived from bacteria, parasites, and fungi can be presented by CD1d molecules and recognized by the canonical T cell receptors on NKT cells. Alternatively, NKT cells can be activated through recognition of self-lipids and/or pro-inflammatory cytokines generated during infection. Unlike conventional T cells, only a small subset of NKT cells traffic through the lymph nodes under homeostatic conditions, with the largest NKT cell populations localizing to the liver, lungs, spleen, and bone marrow. This is thought to be mediated by differences in chemokine receptor expression profiles. However, the impact of infection on the tissue localization and function of NKT remains largely unstudied. This review focuses on the mechanisms mediating the establishment of peripheral NKT cell populations during homeostasis and how tissue localization of NKT cells is affected during infection.

Induction of potent NK cell-dependent anti-myeloma cytotoxic T cells in response to combined mapatumumab and bortezomib

There is increasing evidence that some cancer therapies can promote tumor immunogenicity to boost the endogenous antitumor immune response. In this study, we used the novel combination of agonistic anti-TRAIL-R1 antibody (mapatumumab, Mapa) with low dose bortezomib (LDB) for this purpose. The combination induced profound myeloma cell apoptosis, greatly enhanced the uptake of myeloma cell apoptotic bodies by dendritic cell (DC) and induced anti-myeloma cytotoxicity by both CD8⁺ T cells and NK cells. Cytotoxic lymphocyte expansion was detected within 24 h of commencing therapy and was maximized when myeloma-pulsed DC were co-treated with low dose bortezomib and mapatumumab (LDB+Mapa) in the presence of NK cells. This study shows that Mapa has two distinct but connected modes of action against multiple myeloma (MM). First, when combined with LDB, Mapa produced powerful myeloma cell apoptosis; secondly, it promoted DC priming and an NK cell-mediated expansion of anti-myeloma cytotoxic lymphocyte (CTL). Overall, this study indicates that Mapa can be used to drive potent anti-MM immune responses.

Prognostic indicators of lenalidomide for multiple myeloma: consensus and controversy

The long-term outcome of multiple myeloma (MM) has been greatly improved through new agents, one being lenalidomide (LEN). Based upon the findings of in vitro experiments, its mode of action against MM occurs through a combination of direct tumoricidal effects on myeloma cells, modulatory effects on tumor immunity and tumor microenvironment-regulatory effects. However, it has not been clearly defined whether the clinical response and long-term outcome of MM with LEN treatment truly reflect the mechanisms of action of LEN proposed by in vitro studies. To ascertain what is known and what remains to be elucidated with LEN, we review the current literature on the mode of action of LEN in association with myeloma pathophysiology, and discuss the prognostic indicators in the treatment of MM with LEN.

The cellular immune system in myelomagenesis: NK cells and T cells in the development of myeloma [corrected] and their uses in immunotherapies

As vast strides are being made in the management and treatment of multiple myeloma (MM), recent interests are increasingly focusing on understanding the development of the disease. The knowledge that MM develops exclusively from a protracted phase of monoclonal gammopathy of undetermined significance provides an opportunity to study tumor evolution in this process. Although the immune system has been implicated in the development of MM, the scientific literature on the role and status of various immune components in this process is broad and sometimes contradictory. Accordingly, we present a review of cellular immune subsets in myelomagenesis. We summarize the current literature on the quantitative and functional profiles of natural killer cells and T-cells, including conventional T-cells, natural killer T-cells, γδ T-cells and regulatory T-cells, in myelomagenesis. Our goal is to provide an overview of the status and function of these immune cells in both the peripheral blood and the bone marrow during myelomagenesis. This provides a better understanding of the nature of the immune system in tumor evolution, the knowledge of which is especially significant considering that immunotherapies are increasingly being explored in the treatment of both MM and its precursor conditions.

An emerging role for immune regulatory subsets in chronic lymphocytic leukaemia

The last few years has seen the burgeoning of a new category of therapeutics for cancer targeting immune regulatory pathways. Antibodies that block the PD-1/PD-L1 interaction are perhaps the most prominent of these new anti-cancer therapies, but several other inhibitory receptor ligand interactions have also shown promise as targets in clinical trials, including CTLA-4/CD80 and Lag-3/MHC class II. Related to this is a rapidly improving knowledge of 'regulatory' lymphocyte lineages, including NKT cells, MAIT cells, B regulatory cells and others. These cells have potent cytokine responses that can influence the functioning of other immune cells and many researchers believe that they could be effective targets for therapies designed to enhance immune responses to cancer. This review will outline our current understanding of FOXP3+ 'Tregs', NKT cells, MAIT cells and B regulatory cells immune regulatory cell populations in cancer, with a particular focus on chronic lymphocytic leukaemia (CLL). We will discuss evidence linking CLL with immune regulatory dysfunction and the potential for new therapies targeting regulatory cells.

Pathogenesis beyond the cancer clone(s) in multiple myeloma

Over the past 4 decades, basic research has provided crucial information regarding the cellular and molecular biology of cancer. In particular, the relevance of cancer microenvironment (including both cellular and noncellular elements) and the concept of clonal evolution and heterogeneity have emerged as important in cancer pathogenesis, immunologic escape, and resistance to therapy. Multiple myeloma (MM), a cancer of terminally differentiated plasma cells, is emblematic of the impact of cancer microenvironment and the role of clonal evolution. Although genetic and epigenetic aberrations occur in MM and evolve over time under the pressure of exogenous stimuli, they are also largely present in premalignant plasma cell dyscrasia such as monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM), suggesting that genetic mutations alone are necessary, but not sufficient, for myeloma transformation. The role of bone marrow microenvironment in mediating survival, proliferation, and resistance to therapy in myeloma is well established; and although an appealing speculation, its role in fostering the evolution of MGUS or SMM into MM is yet to be proven. In this review, we discuss MM pathogenesis with a particular emphasis on the role of bone marrow microenvironment.

Cereblon binding molecules in multiple myeloma

Immunomodulation is an established treatment strategy in multiple myeloma with thalidomide and its derivatives lenalidomide and pomalidomide as its FDA approved representatives. Just recently the method of action of these cereblon binding molecules was deciphered and results from large phase 3 trials confirmed the backbone function of this drug family in various combination therapies. This review details the to-date knowledge concerning mechanism of IMiD action, clinical applications and plausible escape mechanisms in which cells may become resistant/refractory to cereblon binding molecule based treatment.

Natural killer T cells: drivers or passengers in preventing human disease?

Natural killer T (NKT) cells are credited with regulatory roles in immunity against cancers, autoimmune diseases, allergies, and bacterial and viral infections. Studies in mice and observational research in patient groups have suggested that NKT cell-based therapies could be used to prevent or treat these diseases, yet the translation into clinical settings has been disappointing. We support the view that NKT cells have regulatory characteristics that could be exploited in clinical settings, but there are doubts about the natural roles of NKT cells in vivo and whether NKT cell defects are fundamental drivers of disease in humans. In this Opinion article, we discuss the uncertainties and opportunities regarding NKT cells in humans, and the potential for NKT cells to be manipulated to prevent or treat disease.