Expression of programmed death-1 on lymphocytes in myeloma patients is lowered during lenalidomide maintenance

Immunomodulatory drugs: a promising clinical ally for cancer immunotherapy

While immunomodulatory imide drugs (IMiDs) have been authorised for treatment of haematological cancers for over two decades, the appreciation of their ability to stimulate antitumour T cell and natural killer (NK) cell responses is relatively recent. Clinical trial data increasingly show that targeted immunotherapies, such as antibodies, T cells, and vaccines, improve outcomes when delivered in combination with the IMiD derivatives lenalidomide or pomalidomide. Here, we review these clinical data to highlight the relevance of IMiDs in combinatorial immunotherapy for both haematological and solid tumours. Further research into the molecular mechanisms of IMiDs and an increased understanding of their immunomodulatory effects may refine the specific applications of IMiDs and improve the design of future clinical trials, moving IMiDs to the forefront of combinatorial cancer immunotherapy.

Lenalidomide arrests cell cycle and modulates PD1-dependent downstream mTOR intracellular signals in melanoma cells

Despite numerous efforts to define the best therapeutic strategies in advanced melanoma, the response of many patients remains heterogeneous and of short duration. Lenalidomide, an immunomodulating drug, has shown anti-inflammatory, antiangiogenic and anticancer properties in haematological disorders; however, few preclinical data support the rationale for using this drug in melanoma patients. In this study, we investigate lenalidomide's potential role in melanoma by focusing on the in-vitro drug's antiproliferative activity. The antiproliferative action of lenalidomide was evaluated on two melanoma cell lines by MTT assay, cell cycle and apoptosis assay. P21 protein levels were evaluated with droplet digital PCR (ddPCR) and western blot analysis while his interaction with specific cyclin-dependent kinase (CDK) was assessed by immunoprecipitation test. The biological effect and molecular mechanisms of programmed cell death-1 (PD-1) in the regulation of proliferation were evaluated using ddPCR, flow cytometry, western blot and small interfering RNA transfection. We observed that lenalidomide exerts a cytostatic effect in melanoma cell lines by inducing cell cycle arrest in the G0-G1 phase through p21 upregulation and modulation of CDK complexes. Furthermore, we found that lenalidomide has an antiproliferative action through the downregulation of melanoma-PD1 expression and consequently the alteration of intracellular signaling of mammalian target of rapamycin/S6. The present study aims to provide new insights into the role of lenalidomide in melanoma and suggesting to potentially translating these findings into a clinical setting to use immunomodulatory derivatives for blocking the pro-tumorigenic activity of the melanoma through the PD-1/PD-L1 axis.

Bispecific Antibodies in Hematological Malignancies: A Scoping Review

Bispecific T-cell engagers (BiTEs) and bispecific antibodies (BiAbs) have revolutionized the treatment landscape of hematological malignancies. By directing T cells towards specific tumor antigens, BiTEs and BiAbs facilitate the T-cell-mediated lysis of neoplastic cells. The success of blinatumomab, a CD19xCD3 BiTE, in acute lymphoblastic leukemia spearheaded the expansive development of BiTEs/BiAbs in the context of hematological neoplasms. Nearly a decade later, numerous BiTEs/BiAbs targeting a range of tumor-associated antigens have transpired in the treatment of multiple myeloma, non-Hodgkin's lymphoma, acute myelogenous leukemia, and acute lymphoblastic leukemia. However, despite their generally favorable safety profiles, particular toxicities such as infections, cytokine release syndrome, myelosuppression, and neurotoxicity after BiAb/BiTE therapy raise valid concerns. Moreover, target antigen loss and the immunosuppressive microenvironment of hematological neoplasms facilitate resistance towards BiTEs/BiAbs. This review aims to highlight the most recent evidence from clinical trials evaluating the safety and efficacy of BiAbs/BiTEs. Additionally, the review will provide mechanistic insights into the limitations of BiAbs whilst outlining practical applications and strategies to overcome these limitations.

The pathogenetic significance of exhausted T cells in a mouse model of mature B cell neoplasms

Dysfunctional anti-tumor immunity has been implicated in the pathogenesis of mature B cell neoplasms, such as multiple myeloma and B cell lymphoma; however, the impact of exhausted T cells on disease development remains unclear. Therefore, the present study investigated the features and pathogenetic significance of exhausted T cells using a mouse model of de novo mature B cell neoplasms, which is likely to show immune escape similar to human patients. The results revealed a significant increase in PD-1+ Tim-3- and PD-1+ Tim-3+ T cells in sick mice. Furthermore, PD-1+ Tim-3+ T cells exhibited direct cytotoxicity with a short lifespan, showing transcriptional similarities to terminally exhausted T cells. On the other hand, PD-1+ Tim-3- T cells not only exhibited immunological responsiveness but also retained stem-like transcriptional features, suggesting that they play a role in the long-term maintenance of anti-tumor immunity. In PD-1+ Tim-3- and PD-1+ Tim-3+ T cells, the transcription factors Tox and Nr4a2, which reportedly contribute to the progression of T cell exhaustion, were up-regulated in vivo. These transcription factors were down-regulated by IMiDs in our in vitro T cell exhaustion analyses. The prevention of excessive T cell exhaustion may maintain effective anti-tumor immunity to cure mature B cell neoplasms.

Bispecific Antibodies in Multiple Myeloma: Opportunities to Enhance Efficacy and Improve Safety

Multiple myeloma (MM) is the second most common haematological neoplasm of adults in the Western world. Overall survival has doubled since the advent of proteosome inhibitors (PIs), immunomodulatory agents (IMiDs), and monoclonal antibodies. However, patients with adverse cytogenetics or high-risk disease as determined by the Revised International Staging System (R-ISS) continue to have poorer outcomes, and triple-refractory patients have a median survival of less than 1 year. Bispecific antibodies (BsAbs) commonly bind to a tumour epitope along with CD3 on T-cells, leading to T-cell activation and tumour cell killing. These treatments show great promise in MM patients, with the first agent, teclistamab, receiving regulatory approval in 2022. Their potential utility is hampered by the immunosuppressive tumour microenvironment (TME), a hallmark of MM, which may limit efficacy, and by undesirable adverse events, including cytokine release syndrome (CRS) and infections, some of which may be fatal. In this review, we first consider the means of enhancing the efficacy of BsAbs in MM. These include combining BsAbs with other drugs that ameliorate the effect of the immunosuppressive TME, improving target availability, the use of BsAbs directed against multiple target antigens, and the optimal time in the treatment pathway to employ BsAbs. We then discuss methods to improve safety, focusing on reducing infection rates associated with treatment-induced hypogammaglobulinaemia, and decreasing the frequency and severity of CRS. BsAbs offer a highly-active therapeutic option in MM. Improving the efficacy and safety profiles of these agents may enable more patients to benefit from these novel therapies and improve outcomes for patients with high-risk disease.

Small-Molecule Compounds Boost CAR-T Cell Therapy in Hematological Malignancies

OPINION STATEMENT

Although chimeric antigen receptor T cell immunotherapy has been successfully applied in patients with hematological malignancies, several obstacles still need to be overcome, such as high relapse rates and side effects. Overcoming the limitations of CAR-T cell therapy and boosting the efficacy of CAR-T cell therapy are urgent issues that must be addressed. The exploration of small-molecule compounds in combination with CAR-T cell therapies has achieved promising success in pre-clinical and clinical studies in recent years. Protein kinase inhibitors, demethylating drugs, HDAC inhibitors, PI3K inhibitors, immunomodulatory drugs, Akt inhibitors, mTOR inhibitors, and Bcl-2 inhibitors exhibited potential synergy in combination with CAR-T cell therapy. In this review, we will discuss the recent application of these combination therapies for improved outcomes of CAR-T cell therapy.

Relapsed/Refractory Multiple Myeloma: A Review of Available Therapies and Clinical Scenarios Encountered in Myeloma Relapse

Multiple myeloma remains an incurable disease with the usual disease course requiring induction therapy, autologous stem cell transplantation for eligible patients, and long-term maintenance. Risk stratification tools and cytogenetic alterations help inform individualized therapeutic choices for patients in hopes of achieving long-term remissions with preserved quality of life. Unfortunately, relapses occur at different stages of the course of the disease owing to the biological heterogeneity of the disease. Addressing relapse can be complex and challenging as there are both therapy- and patient-related factors to consider. In this broad scoping review of available therapies in relapsed/refractory multiple myeloma (RRMM), we cover the pharmacologic mechanisms underlying active therapies such as immunomodulatory agents (IMiDs), proteasome inhibitors (PIs), monoclonal antibodies (mAbs), traditional chemotherapy, and Venetoclax. We then review the clinical data supporting the use of these therapies, organized based on drug resistance/refractoriness, and the role of autologous stem cell transplant (ASCT). Approaches to special situations during relapse such as renal impairment and extramedullary disease are also covered. Lastly, we look towards the future by briefly reviewing the clinical data supporting the use of chimeric antigen receptor (CAR-T) therapy, bispecific T cell engagers (BITE), and Cereblon E3 Ligase Modulators (CELMoDs).

Single-cell transcriptome profiling reveals the key role of ZNF683 in natural killer cell exhaustion in multiple myeloma

BACKGROUNDS

Decreased cytotoxicity of natural killer (NK) cells has been shown in multiple myeloma (MM). However, the underlying molecular mechanisms remain unclear. Here, by using single-cell RNA sequencing analysis and in vitro experiments, we aim to uncover and validate molecularly distinctive insights into identifying regulators for NK cell exhaustion and provide potential targets for novel immune therapies in MM.

METHODS

Single-cell RNA sequencing was conducted in the bone marrow and peripheral blood samples from 10 newly diagnosed MM patients and three healthy volunteers. Based on the cluster-defining differentially expressed genes, we named and estimated functional states of each cluster via bioinformatics analyses. Functional significance of key findings obtained from sequencing analysis was examined in a series of in vitro experiments, including luciferase reporter assay, lentiviral expression vector construction, NK cell transfection, RT-qPCR, flow cytometry, and cytotoxicity assay.

RESULTS

We classified NK cells into seven distinct clusters and confirmed that a subset of ZNF683⁺ NK cells were enriched in MM patients with 'exhausted' transcriptomic profile, featuring as decreased expression of activating receptors and cytolytic molecules, as well as increased expression of inhibitory receptors. Next, we found a significant downregulation of SH2D1B gene that encodes EAT-2, an adaptor protein of activating receptor SLAMF7, in ZNF683⁺ NK cells from MM patients versus healthy volunteers. We further proved that ZNF683 transfection in NK cells significantly downregulated SH2D1B expression via directly binding to the promoter of SH2D1B, leading to NK cell cytotoxic activity impairment and exhausted phenotypes acquisition. In contrast, ZNF683 knockout in NK cells from MM patients increased cytotoxic activity and reversed NK cell exhaustion.

CONCLUSIONS

In summary, our findings uncover an important mechanism of ZNF683⁺ NK cell exhaustion and suggest that transcriptional suppressor ZNF683 as a potential useful therapeutic target in immunotherapy of MM.

Reshaping the tumor microenvironment: The versatility of immunomodulatory drugs in B-cell neoplasms

Immunomodulatory drugs (IMiDs) such as thalidomide, lenalidomide and pomalidomide are antitumor compounds that have direct tumoricidal activity and indirect effects mediated by multiple types of immune cells in the tumor microenvironment (TME). IMiDs have shown remarkable therapeutic efficacy in a set of B-cell neoplasms including multiple myeloma, B-cell lymphomas and chronic lymphocytic leukemia. More recently, the advent of immunotherapy has revolutionized the treatment of these B-cell neoplasms. However, the success of immunotherapy is restrained by immunosuppressive signals and dysfunctional immune cells in the TME. Due to the pleiotropic immunobiological properties, IMiDs have shown to generate synergetic effects in preclinical models when combined with monoclonal antibodies, immune checkpoint inhibitors or CAR-T cell therapy, some of which were successfully translated to the clinic and lead to improved responses for both first-line and relapsed/refractory settings. Mechanistically, despite cereblon (CRBN), an E3 ubiquitin ligase, is considered as considered as the major molecular target responsible for the antineoplastic activities of IMiDs, the exact mechanisms of action for IMiDs-based TME re-education remain largely unknown. This review presents an overview of IMiDs in regulation of immune cell function and their utilization in potentiating efficacy of immunotherapies across multiple types of B-cell neoplasms.

Highly proliferative and functional PD-1+ and TIM-3+ T cells are transiently increased in multiple myeloma following autologous hematopoietic stem cell transplantation

The aim of our prospective study was to assess recovery dynamics and functional characteristics of PD-1⁺ and TIM-3⁺ T cells in multiple myeloma (MM) patients following high-dose chemotherapy (HDCT) with autologous hematopoietic stem cell transplantation (AHSCT). Peripheral blood, autograft and bone marrow samples were obtained from 46 MM patients before conditioning, at the engraftment, following six and 12 months post-transplant. Frequencies of CD4⁺ and CD8⁺ T cells expressing PD-1 and TIM-3 and intracellular expression of Ki-67 and Granzyme B were evaluated. Counts of PD-1⁺ and TIM-3⁺ T cells at the engraftment were significantly higher comparing with the levels before HDCT and 6-12 months following AHSCT. The post-transplant increase in the studied subsets was due to a temporary enhancement in proliferation activity. The cytotoxic potential of PD-1- and TIM-3-expressing CD8⁺ T cells was higher at the engraftment comparing with the pre-transplant and remained at the same level for at least 12 months. The increase in CD4⁺PD-1⁺ and CD8⁺TIM-3⁺ T cells at the engraftment was associated with higher absolute counts of their reinfused counterparts. Circulating PD-1⁺ CD8⁺ and TIM-3⁺ CD4⁺ T cells were increased in patients after post-transplant relapse comparing with the ones in remission. Homeostatic proliferation plays a key role in the upregulation of inhibitory checkpoint receptors on functional T cells under lymphopenic conditions. In this regard, it is difficult to predict both the efficacy and adverse reactions of therapy with checkpoint inhibitors on the course of MM after HDCT with AHSCT. Précis. Homeostatic proliferation plays apparently a key role in the upregulation of PD-1 and TIM-3 on functional T cells after AHSCT and appears to be a normal physiological process, contrary to relapse-associated increase in PD-1⁺ and TIM-3⁺ T cells.

The evolving status of immunotherapies in multiple myeloma: the future role of bispecific antibodies

Treatment outcomes in multiple myeloma (MM) have improved dramatically over the past 10 years. However, patients with high-risk disease such as those with Stage III disease by the Revised International Staging System, the presence of adverse cytogenetics, or who are refractory to proteosome inhibitors, immunomodulatory drugs and monoclonal antibodies may have dismal outcomes. These patients represent an urgent ongoing need in MM. One of the hallmarks of MM is immune dysfunction and a tumour-permissive immune microenvironment. Ameliorating the immune-paresis could lead to improved outcomes. The role of immunotherapies has been growing at an exponential pace with numerous agents under development in clinical trials. In the present review, we provide an overview of immunotherapies in MM, focussing on bispecific antibodies (BsAbs). We review efficacy outcomes from the published clinical trials and consider the important safety aspects of these therapies, in particular the risk of cytokine-release syndrome and immune effector cell-associated neurotoxicity syndrome, and how these compare with patients receiving chimeric antigen receptor T cells. We discuss the MM epitopes being targeted by BsAbs, either in clinical or preclinical stages, and we consider where these therapies might best fit within the future ever-changing paradigm of MM treatment.

What is the future of immunotherapy in multiple myeloma?

The treatment of multiple myeloma (MM) is currently being redefined by humoral and cellular immunotherapies. For decades, there was limited belief in immune-based anti-MM therapy as a result of the moderate graft-versus-myeloma effect of allogeneic stem cell transplantation. Today, monoclonal antibodies comprise the new backbone of anti-MM therapy, and T-cell therapies targeting BCMA are emerging as the most potent single agents for MM treatment. Herein, we present our assessment of and vision for MM immunotherapy in the short and midterm.

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.

A Journey Through Myeloma Evolution: From the Normal Plasma Cell to Disease Complexity

The knowledge of cancer origin and the subsequent tracking of disease evolution represent unmet needs that will soon be within clinical reach. This will provide the opportunity to improve patient's stratification and to personalize treatments based on cancer biology along its life history. In this review, we focus on the molecular pathogenesis of multiple myeloma (MM), a hematologic malignancy with a well-known multi-stage disease course, where such approach can sooner translate into a clinical benefit. We describe novel insights into modes and timing of disease initiation. We dissect the biology of the preclinical and pre-malignant phases, elucidating how knowledge of the genomics of the disease and the composition of the microenvironment allow stratification of patients based on risk of disease progression. Then, we explore cell-intrinsic and cell-extrinsic drivers of MM evolution to symptomatic disease. Finally, we discuss how this may relate to the development of refractory disease after treatment. By integrating an evolutionary view of myeloma biology with the recent acquisitions on its clonal heterogeneity, we envision a way to drive the clinical management of the disease based on its detailed biological features more than surrogates of disease burden.

Quantitative and functional characteristics of circulating and bone marrow PD-1- and TIM-3-positive T cells in treated multiple myeloma patients

The aim of the present work was to evaluate counts and functional properties of PD-1⁺ and TIM-3⁺ T cells in peripheral blood (PB) and bone marrow (BM) of multiple myeloma (MM) patients following the induction therapy. Sixty patients were enrolled in the study, CD4⁺ and CD8⁺ T cells expressing PD-1 and TIM-3, intracellular production of IFNγ and intracellular expression of Granzyme B were assessed. Relative counts of the majority of circulating PD-1⁺, TIM-3⁺ and PD-1⁺TIM-3⁺ T cells were higher in MM patients with disease progression compared with individuals in remission. Frequencies of almost all evaluated PD-1⁺ and TIM-3⁺ T cell subsets were higher in BM samples compared with PB; circulating CD4⁺PD-1⁺, CD8⁺PD-1⁺, CD8⁺TIM-3⁺, CD8⁺PD-1⁺TIM-3⁺ T cells positively correlated with the same BM subsets. Circulating CD4⁺ T cells, expressing PD-1 and TIM-3 (including co-expressing subset), as well as CD8⁺PD-1⁺TIM-3⁺ T cells, and BM CD8⁺PD-1⁺ T cells correlated with serum B2-M levels. Sufficient frequencies of GrB⁺ and IFNγ⁺ subsets in PD-1-expressing T cells indicated their retained functional properties. TIM-3-expressing T cells and double positive PD-1⁺TIM-3⁺ populations showed diminished cytotoxic and cytokine-producing ability and therefore might be attributed to the exhausted compartment. To identify T cell exhaustion, it is necessary to evaluate T cells co-expressing PD-1, TIM-3 and other inhibitory signal molecules and to study their functional properties. Sustained functionality of PD-1-positive T cells may explain low efficacy and frequent immune-mediated adverse events during anti-PD-1 therapy in MM.

CAR T-Cells in Multiple Myeloma: State of the Art and Future Directions

Despite recent therapeutic advances, the prognosis of multiple myeloma (MM) patients remains poor. Thus, new strategies to improve outcomes are imperative. Chimeric antigen receptor (CAR) T-cell therapy has changed the treatment landscape of B-cell malignancies, providing a potentially curative option for patients who are refractory to standard treatment. Long-term remissions achieved in patients with acute lymphoblastic leukemia and Non-Hodgkin Lymphoma encouraged its further development in MM. B-cell maturation antigen (BCMA)-targeted CAR T-cells have established outstanding results in heavily pre-treated patients. However, several other antigens such as SLAMF7 and CD44v6 are currently under investigation with promising results. Idecabtagene vicleucel is expected to be approved soon for clinical use. Unfortunately, relapses after CAR T-cell infusion have been reported. Hence, understanding the underlying mechanisms of resistance is essential to promote prevention strategies and to enhance CAR T-cell efficacy. In this review we provide an update of the most recent clinical and pre-clinical data and we elucidate both, the potential and the challenges of CAR T-cell therapy in the future.

Bispecific Antibodies: A New Era of Treatment for Multiple Myeloma

Despite the introduction of novel agents such as proteasome inhibitors, immunomodulatory drugs, and autologous stem cell transplant, multiple myeloma (MM) largely remains an incurable disease. In recent years, monoclonal antibody-based treatment strategies have been developed to target specific surface antigens on MM cells. Treatment with bispecific antibodies (bsAbs) is an immunotherapeutic strategy that leads to an enhanced interaction between MM cells and immune effector cells, e.g., T-cells and natural killer cells. With the immune synapse built by bsAbs, the elimination of MM cells can be facilitated. To date, bsAbs have demonstrated encouraging results in preclinical studies, and clinical trials evaluating bsAbs in patients with MM are ongoing. Early clinical data show the promising efficacy of bsAbs in relapsed/refractory MM. Together with chimeric antigen receptor-modified (CAR)-T-cells, bsAbs represent a new dimension of precision medicine. In this review, we provide an overview of rationale, current clinical development, resistance mechanisms, and future directions of bsAbs in MM.

Checkpoint Inhibitors and Engineered Cells: New Weapons for Natural Killer Cell Arsenal Against Hematological Malignancies

Natural killer (NK) cells represent one of the first lines of defense against malignant cells. NK cell activation and recognition are regulated by a balance between activating and inhibitory receptors, whose specific ligands can be upregulated on tumor cells surface and tumor microenvironment (TME). Hematological malignancies set up an extensive network of suppressive factors with the purpose to induce NK cell dysfunction and impaired immune-surveillance ability. Over the years, several strategies have been developed to enhance NK cells-mediated anti-tumor killing, while other approaches have arisen to restore the NK cell recognition impaired by tumor cells and other cellular components of the TME. In this review, we summarize and discuss the strategies applied in hematological malignancies to block the immune check-points and trigger NK cells anti-tumor effects through engineered chimeric antigen receptors.

Immunomodulatory Drugs in the Context of Autologous Hematopoietic Stem Cell Transplantation Associate With Reduced Pro-tumor T Cell Subsets in Multiple Myeloma

Immunomodulatory drugs (IMiDs) are effective therapeutics for multiple myeloma (MM), where in different clinical settings they exert their function both directly on MM cells and indirectly by modulating immune cell subsets, although with not completely defined mechanisms. Here we studied the role of IMiDs in the context of autologous hematopoietic stem cell transplantation on the T cell subset distribution in the bone marrow of newly diagnosed MM patients. We found that after transplantation pro-tumor Th17-Th1 and Th22 cells and their related cytokines were lower in patients treated with IMiDs during induction chemotherapy compared to untreated patients. Of note, lower levels of IL-17, IL-22, and related IL-6, TNF-α, IL-1β, and IL-23 in the bone marrow sera correlated with treatment with IMiDs and favorable clinical outcome. Collectively, our results suggest a novel anti-inflammatory role for IMiDs in MM.

Clinical and biological characteristics of myeloma patients influence response to elotuzumab combination therapy

Based on ELOQUENT-2, combination therapy with the monoclonal antibody elotuzumab was approved for relapsed/refractory multiple myeloma in the US and Europe. However, outside clinical trials, the optimal integration of elotuzumab into the sequence of treatment lines remains to be determined. Therefore, we analyzed safety and efficacy of elotuzumab/immunomodulatory drug combinations in a real-life cohort of 33 patients from our institution. The most frequent grade 3/4 adverse event was lymphopenia which did not increase the incidence of viral reactivations. After a median of four prior treatment lines, an overall response rate of 60% and a median progression-free survival (PFS) of 8 months were observed. The presence of cytogenetic high-risk status had no impact on PFS while low disease burden and high numbers of natural killer (NK)-cells at treatment initiation were associated with longer PFS. We observed an extramedullary relapse in three patients, associated with reduced expression of the elotuzumab target antigen SLAMF7 on extramedullary myeloma cells in one patient. Thus, biomarkers like disease burden, NK-cell count and SLAMF7 expression on myeloma cells may help to define myeloma patients with high likelihood to respond to elotuzumab treatment. Prospective trials investigating these biomarkers in larger patient cohorts are highly warranted.

Lenalidomide and Programmed Death-1 Blockade Synergistically Enhances the Effects of Dendritic Cell Vaccination in a Model of Murine Myeloma

The therapeutic efficacy of dendritic cell (DC)-based immunotherapy may be potentiated in combination with other anticancer therapies that enhance DC function by modulating immune responses and the tumor microenvironment. In this study, we investigated the efficacy of DC vaccination in combination with lenalidomide and programmed death (PD)-1 blockade in a model of murine myeloma. MOPC-315 cell lines were injected subcutaneously to establish myeloma-bearing mice and the following five test groups were established: PBS control, DCs, DCs + lenalidomide, DCs + PD-1 blockade, and DCs + lenalidomide + PD-1 blockade. The combination of DCs plus lenalidomide and PD-1 blockade more potently inhibited tumor growth compared to the other groups. This effect was associated with a reduction in immune suppressor cells (such as myeloid-derived suppressor cells, M2 macrophages, and regulatory T cells) and an increase in immune effector cells [such as CD4⁺ and CD8⁺ T cells, natural killer (NK) cells, and M1 macrophages] in the spleen. Functional activities of cytotoxic T lymphocytes and NK cells were also enhanced by the triple combination. Levels of immunosuppressive cytokines, such as TGF-β and IL-10, were significantly reduced in the tumor microenvironment. These findings suggest that the combination of DCs plus lenalidomide and PD-1 blockade synergistically establishes a robust anti-myeloma immunity through a two-way mechanism, which inhibits immunosuppressive cells while activating effector cells with superior polarization of the Th1/Th2 balance in favor of the tumor immune response. This result should provide an experimental ground for incorporating check point inhibitors to existing immunotherapeutic modalities against multiple myeloma.