Successful cross-presentation of allogeneic myeloma cells by autologous alpha-type 1-polarized dendritic cells as an effective tumor antigen in myeloma patients with matched monoclonal immunoglobulins

Novel Immunotherapeutic Agents for the Treatment of Multiple Myeloma

Multiple myeloma (MM) is a B-cell malignancy characterized by the abnormal proliferation of clonal plasma cells in the bone marrow leading to end-organ manifestations. Despite the advancement in the therapy and care of patients with MM, relapse and resistance to standard therapy remain significant. The development of immunotherapy as a treatment modality for many types of cancers has led investigators to explore its use in MM in order to elicit myeloma-targeted immune responses, especially given that immune dysregulation is an underlying feature in the pathogenesis and progression of MM. In this concise review, we discuss the different advances in the immune-based therapy of MM, from immunomodulation, vaccines, to monoclonal antibodies, checkpoint inhibitors, adoptive T-cell therapies, and future promising therapies under investigation.

The Deubiquitinase Inhibitor b-AP15 and Its Effect on Phenotype and Function of Monocyte-Derived Dendritic Cells

The ubiquitin-proteasome system is elementary for cellular protein degradation and gained rising attention as a new target for cancer therapy due to promising clinical trials with bortezomib, the first-in class proteasome inhibitor meanwhile approved for multiple myeloma and mantle cell lymphoma. Both bortezomib and next-generation proteasome inhibitors mediate their effects by targeting the 20S core particle of the 26S proteasome. The novel small molecule inhibitor b-AP15 affects upstream elements of the ubiquitin-proteasome cascade by suppressing the deubiquitinase activity of both proteasomal regulatory 19S subunits and showed promising anticancer activity in preclinical models. Nonetheless, effects of inhibitors on the ubiquitin-proteasome system are not exclusively restricted to malignant cells: alteration of natural killer cell-mediated immune responses had already been described for drugs targeting either 19S or 20S proteasomal subunits. Moreover, it has been shown that bortezomib impairs dendritic cell (DC) phenotype and function at different levels. In the present study, we comparatively analyzed effects of bortezomib and b-AP15 on monocyte-derived DCs. In line with previous results, bortezomib exposure impaired maturation, antigen uptake, migration, cytokine secretion and immunostimulation, whereas treatment with b-AP15 had no compromising effects on these DC features. Our findings warrant the further investigation of b-AP15 as an alternative to clinically approved proteasome inhibitors in the therapy of malignancies, especially in the context of combinatorial treatment with DC-based immunotherapies.

Immunotherapy for the treatment of multiple myeloma

Immunotherapy has recently emerged as a promising treatment for multiple myeloma (MM). There are now several monoclonal antibodies that target specific surface antigens on myeloma cells or the checkpoints of immune and myeloma cells. Elotuzumab (targeting SLAMF7), daratumumab (targeting CD38), and pembrolizumab (targeting PD-1) have shown clinical activity in clinical studies with relapsed/refractory MM. Dendritic cell vaccination is a safe strategy that has shown some efficacy in a subset of myeloma patients and may become a crucial part of MM treatment when combined with immunomodulatory drugs or immune check-point blockade. Genetically engineered T cells, such as chimeric antigen receptor T cells or T cell receptor-engineered T cells, have also shown encouraging results in recent clinical studies of patients with MM. In this paper, we discuss recent progress in immunotherapy for the treatment of MM.

Branched Polyethylenimine-Superparamagnetic Iron Oxide Nanoparticles (bPEI-SPIONs) Improve the Immunogenicity of Tumor Antigens and Enhance Th1 Polarization of Dendritic Cells

Nanoparticles in the field of dendritic cell (DC) research are emerging as a promising method of enhancing the efficacy of cancer immunotherapy. We investigated the effect of branched polyethylenimine-superparamagnetic iron oxide nanoparticles (bPEI-SPIONs) on tumor cells loaded onto DCs. The tumor antigens were prepared as follows: (1) apoptotic U266 cells with ultraviolet B (UVB) irradiation followed by a 2 h incubation in the absence (2 h postirradiated cells) or (2) presence of bPEI-SPIONs (bPEI-SPION 2 h postirradiated cells) and (3) apoptotic U266 cells with UVB irradiation followed by an overnight 16 h incubation (16 h postirradiated cells). bPEI-SPIONs render U266 cells sensitive to UVB irradiation through reactive oxygen species production to accelerate apoptotic death. The 2 h postirradiated cells and bPEI-SPION 2 h postirradiated cells released immunogenic proteins, including Hsp70, Hsp90, and HMGB1. The DCs loaded with bPEI-SPION 2 h postirradiated cells showed the highest IL-12p70 production and Th1 polarization compared with other DCs. These results suggest that bPEI-SPIONs are a promising method of enhancing the immunogenicity of tumor cells and promoting Th1 polarization of DCs loaded with these tumor cells.

Vaccination of multiple myeloma: Current strategies and future prospects

Tumor immunotherapy holds great promise in controlling multiple myeloma (MM) and may provide an alternative treatment modality to conventional chemotherapy for MM patients. For this reason, a major area of investigation is the development of cancer vaccines to generate myeloma-specific immunity. Several antigens that are able to induce specific T-cell responses are involved in different critical mechanisms for cell differentiation, inhibition of apoptosis, demethylation and proliferation. Strategies under development include infusion of vaccine-primed and ex vivo expanded/costimulated autologous T cells after high-dose melphalan, genetic engineering of autologous T cells with receptors for myeloma-specific epitopes, administration of dendritic cell/plasma cell fusions and administration expanded marrow-infiltrating lymphocytes. In addition, novel immunomodulatory drugs may synergize with immunotherapies. The task ahead is to evaluate these approaches in appropriate clinical settings, and to couple them with strategies to overcome mechanisms of immunoparesis as a means to induce more robust clinically significant immune responses.

Dendritic Cell-Based Cancer Immunotherapy against Multiple Myeloma: From Bench to Clinic

Although the introduction of stem cell transplantation and novel agents has improved survival, multiple myeloma (MM) is still difficult to cure. Alternative approaches are clearly needed to prolong the survival of patients with MM. Dendritic cell (DC) therapy is a very promising tool immunologically in MM. We developed a method to generate potent DCs with increased Th1 polarization and migration ability for inducing strong myeloma-specific cytotoxic T lymphocytes. In this review, we discuss how the efficacy of cancer immunotherapy using DCs can be improved in MM.

Evolution of cellular immunotherapy: from allogeneic transplant to dendritic cell vaccination as treatment for multiple myeloma

The promise of cellular therapy as treatment for multiple myeloma is highlighted by the observation that allogeneic transplantation results in durable remissions in a subset of patients. The potency of the graft-versus-myeloma effect is supported by the decreased risk of relapse seen in patients with graft-versus-host disease and disease response following donor lymphocyte infusions. However, the lack of specificity of the alloreactive lymphocytes limits their therapeutic efficacy and results in significant treatment-related morbidity and mortality. A major area of investigation is the development of cancer vaccines to generate myeloma-specific immunity that selectively targets malignant cells while minimizing toxicity to normal tissues. Critical elements required to develop an effective vaccine strategy involve the identification of myeloma-associated antigens, enhancement of antigen presentation, and reversing the immunosuppressive milieu induced by the disease. Dendritic cells are potent APCs that represent an ideal platform for vaccination. Strategies for vaccine design include the loading of individual antigens as well as the use of whole tumor cells as a source of myeloma antigens. Vaccination has been examined in the postautologous transplant setting in which disease cytoreduction and depletion of Tregs is associated with enhanced vaccine response. Recent efforts have also included exploration of immune modulatory agents that target inhibitory pathways to enhance vaccine response and create a more durable antitumor immunity.

Lymphocyte-polarized dendritic cells are highly effective in inducing tumor-specific CTLs

High activity of dendritic cells (DCs) in inducing cytotoxic T cells (CTLs) led to their application as therapeutic cancer vaccines. The ability of DCs to produce IL-12p70 is one of the key requirements for effective CTL induction and a predictive marker of their therapeutic efficacy in vivo. We have previously reported that defined cocktails of cytokines, involving TNFα and IFNγ, induce mature type-1 polarized DCs (DC1s) which produce strongly elevated levels of IL-12 and CXCL10/IP10 upon CD40 ligation compared to "standard" PGE₂-matured DCs (sDCs; matured with IL-1β, IL-6, TNFα, and PGE₂) and show higher CTL-inducing activity. Guided by our observations that DC1s can be induced by TNFα- and IFNγ-producing CD8⁺ T cells, we have tested the feasibility of using lymphocytes to generate DC1s in a clinically-compatible process, to limit the need for clinical-grade recombinant cytokines and the associated costs. CD3/CD28 activation of bulk lymphocytes expanded them and primed them for effective production of IFNγ and TNFα following restimulation. Restimulated lymphocytes, or their culture supernatants, enhanced the maturation status of immature (i)DCs, elevating their expression of CD80, CD83 and CCR7, and the ability to produce IL-12p70 and CXCL10 upon subsequent CD40 ligation. The "lymphocyte-matured" DC1s showed elevated migration in response to the lymph-node-directing chemokine, CCL21, when compared to iDCs. When loaded with antigenic peptides, supernatant-matured DCs induced much high levels of CTLs recognizing tumor-associated antigenic epitope, than PGE₂-matured DCs from the same donors. These results demonstrate the feasibility of generation of polarized DC1s using autologous lymphocytes.

Cellular immunotherapy using dendritic cells against multiple myeloma

Cellular therapy with dendritic cells (DCs) is emerging as a useful immunotherapeutic tool to treat multiple myeloma (MM). DC-based idiotype vaccination was recently suggested to induce idiotype-specific immune responses in MM patients. However, the clinical results so far have been largely disappointing, and the clinical effectiveness of such vaccinations in MM still needs to be demonstrated. DC-based therapies against MM may need to be boosted with other sources of tumor-associated antigens, and potent DCs should be recruited to increase the effectiveness of treatment. DCs with both high migratory capacity and high cytokine production are very important for effective DC-based cancer vaccination in order to induce high numbers of Th1-type CD4⁺ T cells and CD8⁺ cytotoxic T lymphocytes. The tumor microenvironment is also important in the regulation of tumor cell growth, proliferation, and the development of therapeutic resistance after treatment. In this review, we discuss how the efficacy of DC vaccination in MM can be improved. In addition, novel treatment strategies that target not only myeloma cells but also the tumor microenvironment are urgently needed to improve treatment outcomes.

Immunotherapy using dendritic cells against multiple myeloma: how to improve?

Multiple myeloma (MM) is a good target disease in which one can apply cellular immunotherapy, which is based on the graft-versus-myeloma effect. This role of immune effector cells provides the framework for the development of immune-based therapeutic options that use antigen-presenting cells (APCs) with increased potency, such as dendritic cells (DCs), in MM. Current isolated idiotype (Id), myeloma cell lysates, myeloma dying cells, DC-myeloma hybrids, or DC transfected with tumor-derived RNA has been used for immunotherapy with DCs. Immunological inhibitory cytokines, such as TGF-β, IL-10, IL-6 and VEGF, which are produced from myeloma cells, can modulate antitumor host immune response, including the abrogation of DC function, by constitutive activation of STAT3. Therefore, even the immune responses have been observed in clinical trials, the clinical response was rarely improved following DC vaccinations in MM patients. We are going to discuss how to improve the efficacy of DC vaccination in MM.