Fusion of dendritic cells with multiple myeloma cells results in maturation and enhanced antigen presentation

Chimeric Antigen Receptor T Cells in Multiple Myeloma

Multiple myeloma is the second most common hematological malignancy with an approximate incidence of up to 8.5 cases per 100,000 persons per year. Over the last decade, therapy for multiple myeloma has undergone a revolutionary change. Chimeric antigen receptor (CAR) T-cell therapy has played a major role in this evolution. In this review, we discuss the existing state of CAR T-cell therapy in myeloma while evaluating several newer therapies and targets expected in the near future.

Manufacturing Dendritic Cells for Immunotherapy: Monocyte Enrichment

Dendritic cells play a key role in activation of the immune system as potent antigen-presenting cells. This pivotal position, along with the ability to generate dendritic cells from monocytes and ready uptake of antigen, makes them an intriguing vehicle for immunotherapy for a variety of indications. Since the first reported trial using dendritic cells in 1995, they have been used in trials all over the world for a plethora of indications. Monocyte-derived dendritic cells are generated from whole blood or apheresis products by culturing enriched monocytes in the presence of interleukin (IL)-4 and granulocyte-macrophage colony-stimulating factor (GM-CSF). A variety of methods can be used for enrichment of monocytes for generation of clinical-grade dendritic cells and are summarized herein.

Dendritic cells as cancer therapeutics

The ability of immune therapies to control cancer has recently generated intense interest. This therapeutic outcome is reliant on T cell recognition of tumour cells. The natural function of dendritic cells (DC) is to generate adaptive responses, by presenting antigen to T cells, hence they are a logical target to generate specific anti-tumour immunity. Our understanding of the biology of DC is expanding, and they are now known to be a family of related subsets with variable features and function. Most clinical experience to date with DC vaccination has been using monocyte-derived DC vaccines. There is now growing experience with alternative blood-derived DC derived vaccines, as well as with multiple forms of tumour antigen and its loading, a wide range of adjuvants and different modes of vaccine delivery. Key insights from pre-clinical studies, and lessons learned from early clinical testing drive progress towards improved vaccines. The potential to fortify responses with other modalities of immunotherapy makes clinically effective "second generation" DC vaccination strategies a priority for cancer immune therapists.

Consolidation and Maintenance Therapies for Newly Diagnosed Multiple Myeloma in the Era of Novel Agents

Advances in therapy in multiple myeloma have resulted in significant improvements in patient outcomes; however, relapse remains problematic. Strategies to improve outcomes following autologous stem cell transplantation (ASCT) include consolidation to intensify therapy and improve depth of response and maintenance therapy to achieve long-term disease control. Immunomodulatory drugs (IMiDs), including thalidomide and lenalidomide, are appealing as maintenance therapy given their oral administration; however, the cumulative toxicities of thalidomide have limited its efficacy in maintenance therapy. Maintenance lenalidomide is better tolerated, and multiple studies have demonstrated an improvement in progression-free survival (PFS), but its impact on overall survival (OS) remains controversial. Additional concerns regarding the risk of second primary malignancies and significant cost of long-term lenalidomide therapy have also been raised. Proteasome inhibitors, particularly, bortezomib have also been incorporated in consolidation and maintenance regimens alone or in combination with an IMiD. Preliminary studies have suggested bortezomib maintenance may benefit patients with adverse cytogenetics, including t(4;14) and deletion 17p. Determination of the optimal consolidation and maintenance regimen and duration of therapy post-transplantation is a focus of several ongoing randomized studies.

Extracellular matrix and the myeloid-in-myeloma compartment: balancing tolerogenic and immunogenic inflammation in the myeloma niche

The last 10-15 years have witnessed a revolution in treating multiple myeloma, an incurable cancer of Ab-producing plasma cells. Advances in myeloma therapy were ushered in by novel agents that remodel the myeloma immune microenvironment. The first generation of novel agents included immunomodulatory drugs (thalidomide analogs) and proteasome inhibitors that target crucial pathways that regulate immunity and inflammation, such as NF-κB. This paradigm continued with the recent regulatory approval of mAbs (elotuzumab, daratumumab) that impact both tumor cells and associated immune cells. Moreover, recent clinical data support checkpoint inhibition immunotherapy in myeloma. With the success of these agents has come the growing realization that the myeloid infiltrate in myeloma lesions-what we collectively call the myeloid-in-myeloma compartment-variably sustains or deters tumor cells by shaping the inflammatory milieu of the myeloma niche and by promoting or antagonizing immune-modulating therapies. The myeloid-in-myeloma compartment includes myeloma-associated macrophages and granulocytes, dendritic cells, and myeloid-derived-suppressor cells. These cell types reflect variable states of differentiation and activation of tumor-infiltrating cells derived from resident myeloid progenitors in the bone marrow-the canonical myeloma niche-or myeloid cells that seed both canonical and extramedullary, noncanonical niches. Myeloma-infiltrating myeloid cells engage in crosstalk with extracellular matrix components, stromal cells, and tumor cells. This complex regulation determines the composition, activation state, and maturation of the myeloid-in-myeloma compartment as well as the balance between immunogenic and tolerogenic inflammation in the niche. Redressing this balance may be a crucial determinant for the success of antimyeloma immunotherapies.

Bone marrow stroma protects myeloma cells from cytotoxic damage via induction of the oncoprotein MUC1

Multiple myeloma (MM) is a lethal haematological malignancy that arises in the context of a tumour microenvironment that promotes resistance to apoptosis and immune escape. In the present study, we demonstrate that co-culture of MM cells with stromal cells results in increased resistance to cytotoxic and biological agents as manifested by decreased rates of cell death following exposure to alkylating agents and the proteosome inhibitor, bortezomib. To identify the mechanism of increased resistance, we examined the effect of the co-culture of MM cells with stroma cells, on expression of the MUC1 oncogene, known to confer tumour cells with resistance to apoptosis and necrosis. Co-culture of stroma with MM cells resulted in increased MUC1 expression by tumour cells. The effect of stromal cell co-culture on MUC1 expression was not dependent on cell contact and was therefore thought to be due to soluble factors secreted by the stromal cells into the microenvironment. We demonstrated that MUC1 expression was mediated by interleukin-6 and subsequent up-regulation of the JAK-STAT pathway. Interestingly, the effect of stromal cell co-culture on tumour resistance was partially reversed by silencing of MUC1 in MM cells, consistent with the potential role of MUC1 in mediating resistance to cytotoxic-based therapies.

New Strategies in Multiple Myeloma: Immunotherapy as a Novel Approach to Treat Patients with Multiple Myeloma

Multiple myeloma is a B-cell malignancy characterized by proliferation of monoclonal plasma cells in the bone marrow. Although new therapeutic options introduced in recent years have resulted in improved survival outcomes, multiple myeloma remains incurable for a large number of patients, and new treatment options are urgently needed. Over the last 5 years, there has been a renewed interest in the clinical potential of immunotherapy for the treatment of multiple myeloma. Clinical progression of myeloma is known to be associated with progressive immune dysregulation and loss of immune surveillance that contribute to disease progression in association with progressive genetic complexity, rendering signaling-based treatments less effective. A variety of strategies to reverse the multiple myeloma-induced immunosuppression has been developed either in the form of immunomodulatory drugs, checkpoint inhibitors, mAbs, engineered T cells, and vaccines. They have shown encouraging results in patients with relapsed refractory multiple myeloma and hold great promise in further improving patient outcomes in multiple myeloma. This review will summarize the major approaches in multiple myeloma immunotherapies and discuss the mechanisms of action and clinical activity of these strategies. Clin Cancer Res; 22(24); 5959-65. ©2016 AACR.

The Role of Immunotherapy in Multiple Myeloma

Multiple myeloma is the second most common hematologic malignancy. The treatment of this disease has changed considerably over the last two decades with the introduction to the clinical practice of novel agents such as proteasome inhibitors and immunomodulatory drugs. Basic research efforts towards better understanding of normal and missing immune surveillence in myeloma have led to development of new strategies and therapies that require the engagement of the immune system. Many of these treatments are under clinical development and have already started providing encouraging results. We, for the second time in the last two decades, are about to witness another shift of the paradigm in the management of this ailment. This review will summarize the major approaches in myeloma immunotherapies.

Immunotherapy strategies in multiple myeloma

Multiple myeloma (MM) is a B-cell malignancy characterized by the clonal proliferation of malignant plasma cells in the bone marrow and the development of osteolytic bone lesions. MM has emerged as a paradigm within the cancers for the success of drug discovery and translational medicine. This article discusses immunotherapy as an encouraging option for the goal of inducing effective and long-lasting therapeutic outcome. Divided into two distinct approaches, passive or active, immunotherapy, which targets tumor-associated antigens has shown promising results in multiple preclinical and clinical studies.

Sequential infusion of donor-derived dendritic cells with donor lymphocyte infusion for relapsed hematologic cancers after allogeneic hematopoietic stem cell transplantation

Donor lymphocyte infusion (DLI) is often given to induce a graft-versus-leukemia (GVL) effect after allogeneic hematopoietic stem cell transplantation (HSCT). However, efficacy of DLI is limited in most hematologic cancers. As antigen presenting cells, dendritic cells (DC) bolster immune responses. We conducted a Phase I trial testing the coinfusion of DC followed by DLI. DC were generated by culturing peripheral blood mononuclear cells from HLA matched-related donors in GM-CSF and IL-4 for 7 days, followed by TNF-α for 3 days. DC were administered intravenously on 3 dose levels (5 × 10(6) ; 1 × 10(7) ; 5 × 10(7) cells). DLI (3 × 10(7) CD3+ cells/kg) was administered intravenously 1 day after the DC. Sixteen patients with hematologic cancers relapsed after HSCT were treated. A maximum tolerated dose for DC was not reached. Two of 16 patients met criteria for DLT within 10 weeks of the infusion: 1 idiopathic respiratory failure, 1 ventricular cardiac arrest. None developed grade III/IV GVHD. One patient developed grade II acute intestinal graft-vs.-host disease (GVHD) and 1 chronic GVHD within 6 months of the infusion. Both resolved with corticosteroids. Four of 14 patients evaluable for disease response achieved durable remissions and are alive and cancer free 6.7, 8.4, 8.8, and 10.1 years from infusion. Sequential infusion of donor-derived DC with DLI is feasible in patients with relapsed hematologic cancers after allogeneic HSCT. Future studies may consider donor DC preloaded with tumor antigens to investigate whether DC infusion could augment the GVL effect.

Dendritic cell cancer vaccines: from the bench to the bedside

The recognition that the development of cancer is associated with acquired immunodeficiency, mostly against cancer cells themselves, and understanding pathways inducing this immunosuppression, has led to a tremendous development of new immunological approaches, both vaccines and drugs, which overcome this inhibition. Both "passive" (e.g. strategies relying on the administration of specific T cells) and "active" vaccines (e.g. peptide-directed or whole-cell vaccines) have become attractive immunological approaches, inducing cell death by targeting tumor-associated antigens. Whereas peptide-targeted vaccines are usually directed against a single antigen, whole-cell vaccines (e.g. dendritic cell vaccines) are aimed to induce robust responsiveness by targeting several tumor-related antigens simultaneously. The combination of vaccines with new immuno-stimulating agents which target "immunosuppressive checkpoints" (anti-CTLA-4, PD-1, etc.) is likely to improve and maintain immune response induced by vaccination.

T cell-based targeted immunotherapies for patients with multiple myeloma

Despite high-dose chemotherapy followed by autologs stem-cell transplantation as well as novel therapeutic agents, multiple myeloma (MM) remains incurable. Following the general trend towards personalized therapy, targeted immunotherapy as a new approach in the therapy of MM has emerged. Better progression-free survival and overall survival after tandem autologs/allogeneic stem cell transplantation suggest a graft versus myeloma effect strongly supporting the usefulness of immunological therapies for MM patients. How to induce a powerful antimyeloma effect is the key issue in this field. Pivotal is the definition of appropriate tumor antigen targets and effective methods for expansion of T cells with clinical activity. Besides a comprehensive list of tumor antigens for T cell-based approaches, eight promising antigens, CS1, Dickkopf-1, HM1.24, Human telomerase reverse transcriptase, MAGE-A3, New York Esophageal-1, Receptor of hyaluronic acid mediated motility and Wilms' tumor gene 1, are described in detail to provide a background for potential clinical use. Results from both closed and on-going clinical trials are summarized in this review. On the basis of the preclinical and clinical data, we elaborate on three encouraging therapeutic options, vaccine-enhanced donor lymphocyte infusion, chimeric antigen receptors-transfected T cells as well as vaccines with multiple antigen peptides, to pave the way towards clinically significant immune responses against MM.

Proceedings from the National Cancer Institute's Second International Workshop on the Biology, Prevention, and Treatment of Relapse after Hematopoietic Stem Cell Transplantation: part II. Autologous Transplantation-novel agents and immunomodulatory strategies

In the National Cancer Institute's Second International Workshop on the Biology, Prevention, and Treatment of Relapse after Hematopoietic Stem Cell Transplantation, the Scientific/Educational Session on Autologous Transplantation addressed the role of novel agents and immunomodulatory strategies in management of relapse after autologous hematopoietic stem cell transplantation (AHSCT). Concepts were illustrated through in-depth discussion of multiple myeloma, with broader discussion of areas relevant for relapse of other malignancies as well as in the setting of allogeneic transplantation. Dr. Hari provided an overview of the epidemiology of relapse after AHSCT in multiple myeloma, addressing clinical patterns, management implications, and treatment options at relapse, highlighting the implications of novel therapeutic agents in initial, maintenance, and relapse treatment. Dr. Avigan discussed current concepts in tumor vaccine design, including whole cell and antigen-specific strategies, use of an AHSCT platform to reverse tumor-associated immunosuppression and tolerance, and combining vaccines with immunomodulatory agents to promote establishment of durable antitumor immunity. Dr. Hsu reviewed the immunogenetics of natural killer (NK) cells and general NK biology, the clinical importance of autologous NK activity (eg, lymphoma and neuroblastoma), the impact of existing therapies on promotion of NK cell activity (eg, immunomodulatory drugs, monoclonal antibodies), and strategies for enhancing autologous and allogeneic NK cell effects through NK cell gene profiling.

Vaccination with dendritic cell/tumor fusions following autologous stem cell transplant induces immunologic and clinical responses in multiple myeloma patients

PURPOSE

A multiple myeloma vaccine has been developed whereby patient-derived tumor cells are fused with autologous dendritic cells, creating a hybridoma that stimulates a broad antitumor response. We report on the results of a phase II trial in which patients underwent vaccination following autologous stem cell transplantation (ASCT) to target minimal residual disease.

EXPERIMENTAL DESIGN

Twenty-four patients received serial vaccinations with dendritic cell/myeloma fusion cells following posttransplant hematopoietic recovery. A second cohort of 12 patients received a pretransplant vaccine followed by posttransplant vaccinations. Dendritic cells generated from adherent mononuclear cells cultured with granulocyte macrophage colony-stimulating factor, interleukin-4, and TNF-α were fused with autologous bone marrow-derived myeloma fusion cells using polyethylene glycol. Fusion cells were quantified by determining the percentage of cells that coexpress dendritic cell and myeloma fusion antigens.

RESULTS

The posttransplant period was associated with reduction in general measures of cellular immunity; however, an increase in CD4 and CD8(+) myeloma-specific T cells was observed after ASCT that was significantly expanded following posttransplant vaccination. Seventy-eight percent of patients achieved a best response of complete response (CR)+very good partial response (VGPR) and 47% achieved a CR/near CR (nCR). Remarkably, 24% of patients who achieved a partial response following transplant were converted to CR/nCR after vaccination and at more than 3 months posttransplant, consistent with a vaccine-mediated effect on residual disease.

CONCLUSIONS

The posttransplant period for patients with multiple myeloma provides a unique platform for cellular immunotherapy in which vaccination with dendritic cell/myeloma fusion fusions resulted in the marked expansion of myeloma-specific T cells and cytoreduction of minimal residual disease.

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.

Dendritic/tumor fusion cells as cancer vaccines

A promising cancer vaccine involves the fusion of dendritic cells (DCs) with tumor cells such that a broad array of tumor antigens are presented in the context of DC-mediated costimulation and stimulatory cytokines. In diverse animal models, vaccination with DC/tumor fusions results in protection from an otherwise lethal challenge of tumor cells and eradication of established disease. In phase I clinical studies, vaccination with DC/tumor fusions was well tolerated, and induced immunologic responses in the majority of patients and clinical responses in a subset. Vaccine efficacy may be blunted by the immunosuppressive milieu characteristic of patients with malignancy, including the increased presence of regulatory T cells, and inhibitory pathways such as the PD-1/PDL-1 pathway. A current focus of research interest lies in enhancing response to cancer vaccines, by combining vaccination with tumor cytoreduction, regulatory T-cell depletion, and blockade of critical inhibitory pathways.

Lenalidomide enhances anti-myeloma cellular immunity

Lenalidomide is an effective therapeutic agent for multiple myeloma that exhibits immunomodulatory properties including the activation of T and NK cells. The use of lenalidomide to reverse tumor-mediated immune suppression and amplify myeloma-specific immunity is currently being explored. In the present study, we examined the effect of lenalidomide on T-cell activation and its ability to amplify responses to a dendritic cell-based myeloma vaccine. We demonstrate that exposure to lenalidomide in the context of T-cell expansion with direct ligation of CD3/CD28 complex results in polarization toward a Th1 phenotype characterized by increased IFN-γ, but not IL-10 expression. In vitro exposure to lenalidomide resulted in decreased levels of regulatory T cells and a decrease in T-cell expression of the inhibitory marker, PD-1. Lenalidomide also enhanced T-cell proliferative responses to allogeneic DCs. Most significantly, lenalidomide treatment potentiated responses to the dendritic cell/myeloma fusion vaccine, which were characterized by increased production of inflammatory cytokines and increased cytotoxic lymphocyte-mediated lysis of autologous myeloma targets. These findings indicate that lenalidomide enhances the immunologic milieu in patients with myeloma by promoting T-cell proliferation and suppressing inhibitory factors, and thereby augmenting responses to a myeloma-specific tumor vaccine.

Optical nanomanipulations of malignant cells: controlled cell damage and fusion

Specifically targeting and manipulating living cells is a key challenge in biomedicine and in cancer research in particular. Several studies have shown that nanoparticles irradiated by intense lasers are capable of conveying damage to nearby cells for various therapeutic and biological applications. In this work ultrashort laser pulses and gold nanospheres are used for the generation of localized, nanometric disruptions on the membranes of specifically targeted cells. The high structural stability of the nanospheres and the resonance pulse irradiation allow effective means for controlling the induced nanometric effects. The technique is demonstrated by inducing desired death mechanisms in epidermoid carcinoma and Burkitt lymphoma cells, and initiating efficient cell fusion between various cell types. Main advantages of the presented approach include low toxicity, high specificity, and high flexibility in the regulation of cell damage and cell fusion, which would allow it to play an important role in various future clinical and scientific applications.

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.

The 39th David A. Karnofsky Lecture: bench-to-bedside translation of targeted therapies in multiple myeloma

Multiple myeloma (MM) is a remarkable example of rapid bench-to-bedside translation in new drug development. The proteasome inhibitor bortezomib and immunomodulatory drug lenalidomide targeted MM cells in the bone marrow (BM) microenvironment to overcome conventional drug resistance in laboratory and animal models and were rapidly translated into clinical trials demonstrating their efficacy in patients with relapsed and then newly diagnosed MM, with a doubling of the median survival as a direct result. The future is even brighter. First, immune-based therapies are being developed (eg, elotuzumab monoclonal antibody [MoAb]; CD138DM immunotoxin; MM cell-dendritic cell vaccines; CD138, CS-1, and XBP-1 peptide vaccines; anti-17 MoAb; and other treatments to overcome causes of immune dysfunction). Second, promising next-generation agents target the MM cell in its microenvironment (eg, deubiquitinating enzyme inhibitors; chymotryptic [carfilzomib, Onyx 0912, MLN 9708] and broader [NPI-0052] proteasome inhibitors; immunoproteasome inhibitors; and pomalidamide). Moreover, agents targeting bone biology (eg, zoledronic acid, anti-DKK-1 MoAb, anti-B-cell activating factor MoAb and bortezomib, Btk inhibitor) show promise not only in preserving bone integrity but also against MM. Third, rationally based combination therapies, including bortezomib with Akt, mammalian target of rapamycin, or histone deacetylase inhibitors, are active even in bortezomib-refractory MM. Finally, genomics is currently being used in the definition of MM heterogeneity, new target discovery, and development of personalized therapy. Myeloma therefore represents a paradigm for targeting the tumor in its microenvironment, which has already markedly improved patient outcome in MM and has great potential in other hematologic malignancies and solid tumors as well.

New Insights into Therapeutic Targets in Myeloma

Patient outcome in multiple myeloma (MM) has been remarkably improved due to the use of combination therapies including proteasome inhibitors and immunomodulatory drugs, which target the tumor in its BM microenvironment. Ongoing efforts to improve the treatment paradigm even further include using oncogenomics to better characterize molecular pathogenesis and to develop refined patient stratification and personalized medicine in MM; using models of MM in its BM milieu to identify novel targets and to validate next-generation therapeutics directed at these targets; developing immune-based therapies including mAbs, immunotoxins targeting MM cells and cytokines, and novel vaccine strategies; and using functional oncogenomics to inform the design of novel combination therapies. With continued rapid evolution of progress in these areas, MM will be a chronic illness with sustained complete response in a significant number of patients.

Identification of novel myeloma-specific XBP1 peptides able to generate cytotoxic T lymphocytes: a potential therapeutic application in multiple myeloma

The purpose of these studies was to identify HLA-A2⁺ immunogenic peptides derived from XBP1 antigens to induce a multiple myeloma (MM)-specific immune response. Six native peptides from non-spliced XBP1 antigen and three native peptides from spliced XBP1 antigen were selected and evaluated for their HLA-A2 specificity. Among them, XBP1_184–192, XBP1 SP_196–204 and XBP1 SP_367–375 peptides showed the highest level of binding affinity, but not stability to HLA-A2 molecules. Novel heteroclitic XBP1 peptides, YISPWILAV or YLFPQLISV, demonstrated a significant improvement in HLA-A2 stability from their native XBP1_184–192 or XBP1 SP_367–375 peptide, respectively. Cytotoxic T lymphocytes generated by repeated stimulation of CD3⁺ T cells with each HLA-A2-specific heteroclitic peptide showed an increased percentage of CD8⁺ (cytotoxic) and CD69⁺/CD45RO⁺ (activated memory) T cells and a lower percentage of CD4⁺ (helper) and CD45RA⁺/CCR7⁺ (naïve) T cells, which were distinct from the control T cells. Functionally, the CTLs demonstrated MM-specific and HLA-A2-restricted proliferation, IFN-γ secretion and cytotoxic acivity in response to MM cell lines and importantly, cytotoxicty against primary MM cells. These data demonstrate the distinct immunogenic characteristics of unique heteroclitic XBP1 peptides which induce MM-specific CTLs and highlights their potential application for immunotherapy to treat the patients with MM or its pre-malignant condition.

HER-2/neu tolerant and non-tolerant mice for fine assessment of antimetastatic potency of dendritic cell-tumor cell hybrid vaccines

Main obstacles to cancer vaccine efficacy are pre-existing antigenic load and immunoescape mechanisms, including tolerance against self tumor-associated antigens. Here we explored the role of tolerance in an antimetastatic vaccine approach based on dendritic cell-tumor cell (DC-TC) hybrids, thanks to the comparison between BALB-neuT mice, transgenic for and tolerant to rat HER-2/neu, with their non-tolerant strain of origin BALB/c. Allogeneic DC-TC hybrid vaccine displayed a high antimetastatic activity in non-tolerant mice, but was far less effective in tolerant mice, even with intensified vaccine schedule. Tolerant BALB-neuT mice revealed a reduced ability to mount polarized Th1 responses. A further attempt to increase the antimetastatic activity by using LPS-matured DC hybrids failed. Allogeneic LPS-matured DC-TC hybrids induced high IFN-γ levels, but concomitantly also the highest production of IL-4 and IL-10 suggesting activation of mechanisms sustaining regulatory cells able to blunt vaccine efficacy. Our data in tolerant versus non-tolerant hosts suggest that clinical translation of effective DC-based strategies could benefit from more extensive investigations in tolerant transgenic models.

Immunologic monitoring of cellular responses by dendritic/tumor cell fusion vaccines

Although dendritic cell (DC)- based cancer vaccines induce effective antitumor activities in murine models, only limited therapeutic results have been obtained in clinical trials. As cancer vaccines induce antitumor activities by eliciting or modifying immune responses in patients with cancer, the Response Evaluation Criteria in Solid Tumors (RECIST) and WHO criteria, designed to detect early effects of cytotoxic chemotherapy in solid tumors, may not provide a complete assessment of cancer vaccines. The problem may, in part, be resolved by carrying out immunologic cellular monitoring, which is one prerequisite for rational development of cancer vaccines. In this review, we will discuss immunologic monitoring of cellular responses for the evaluation of cancer vaccines including fusions of DC and whole tumor cell.

Dendritic cell-tumor cell hybrids and immunotherapy: what's next?

Dendritic cells (DC) are professional antigen-presenting cells currently being used as a cellular adjuvant in cancer immunotherapy strategies. Unfortunately, DC-based vaccines have not demonstrated spectacular clinical results. DC loading with tumor antigens and DC differentiation and activation still require optimization. An alternative technique for providing antigens to DC consists of the direct fusion of dendritic cells with tumor cells. These resulting hybrid cells may express both major histocompatibility complex (MHC) class I and II molecules associated with tumor antigens and the appropriate co-stimulatory molecules required for T-cell activation. Initially tested in animal models, this approach has now been evaluated in clinical trials, although with limited success. We summarize and discuss the results from the animal studies and first clinical trials. We also present a new approach to inducing hybrid formation by expression of viral fusogenic membrane glycoproteins.

New insights into therapeutic targets in myeloma

Patient outcome in multiple myeloma (MM) has been remarkably improved due to the use of combination therapies including proteasome inhibitors and immunomodulatory drugs, which target the tumor in its BM microenvironment. Ongoing efforts to improve the treatment paradigm even further include using oncogenomics to better characterize molecular pathogenesis and to develop refined patient stratification and personalized medicine in MM; using models of MM in its BM milieu to identify novel targets and to validate next-generation therapeutics directed at these targets; developing immune-based therapies including mAbs, immunotoxins targeting MM cells and cytokines, and novel vaccine strategies; and using functional oncogenomics to inform the design of novel combination therapies. With continued rapid evolution of progress in these areas, MM will be a chronic illness with sustained complete response in a significant number of patients.

Regulation of tumor immunity by tumor/dendritic cell fusions

The goal of cancer vaccines is to induce antitumor immunity that ultimately will reduce tumor burden in tumor environment. Several strategies involving dendritic cells- (DCs)- based vaccine incorporating different tumor-associated antigens to induce antitumor immune responses against tumors have been tested in clinical trials worldwide. Although DCs-based vaccine such as fusions of whole tumor cells and DCs has been proven to be clinically safe and is efficient to enhance antitumor immune responses for inducing effective immune response and for breaking T-cell tolerance to tumor-associated antigens (TAAs), only a limited success has occurred in clinical trials. This paper reviews tumor immune escape and current strategies employed in the field of tumor/DC fusions vaccine aimed at enhancing activation of TAAs-specific cytotoxic T cells in tumor microenvironment.

Survival of human multiple myeloma cells is dependent on MUC1 C-terminal transmembrane subunit oncoprotein function

The MUC1 C-terminal transmembrane subunit (MUC1-C) oncoprotein is a direct activator of the canonical nuclear factor-kappaB (NF-kappaB) RelA/p65 pathway and is aberrantly expressed in human multiple myeloma cells. However, it is not known whether multiple myeloma cells are sensitive to the disruption of MUC1-C function for survival. The present studies demonstrate that peptide inhibitors of MUC1-C oligomerization block growth of human multiple myeloma cells in vitro. Inhibition of MUC1-C function also blocked the interaction between MUC1-C and NF-kappaB p65 and activation of the NF-kappaB pathway. In addition, inhibition of MUC1-C in multiple myeloma cells was associated with activation of the intrinsic apoptotic pathway and induction of late apoptosis/necrosis. Primary multiple myeloma cells, but not normal B-cells, were also sensitive to MUC1-C inhibition. Significantly, treatment of established U266 multiple myeloma xenografts growing in nude mice with a lead candidate MUC1-C inhibitor resulted in complete tumor regression and lack of recurrence. These findings indicate that multiple myeloma cells are dependent on intact MUC1-C function for constitutive activation of the canonical NF-kappaB pathway and for their growth and survival.

Fusions of dendritic cells with breast carcinoma stimulate the expansion of regulatory T cells while concomitant exposure to IL-12, CpG oligodeoxynucleotides, and anti-CD3/CD28 promotes the expansion of activated tumor reactive cells

Vaccination of patients with dendritic cell (DC)/breast carcinoma fusions stimulated antitumor immune responses in a majority of patients with metastatic disease but only a subset demonstrate evidence of tumor regression. To define the factors that limit vaccine efficacy, we examined the biological characteristics of DC/breast carcinoma fusions as APCs and the nature of the vaccine-mediated T cell response. We demonstrate that fusion of DCs with breast carcinoma cells up-regulates expression of costimulatory and maturation markers and results in high levels of expression of IL-12 consistent with their role as activated APCs. Fusion cells also express the chemokine receptor CCR7, consistent with their ability to migrate to the draining lymph node. However, DC/breast cancer fusions stimulate a mixed T cell response characterized by the expansion of both activated and regulatory T cell populations, the latter of which is characterized by expression of CTLA-4, FOXP3, IL-10, and the suppression of T cell responses. Our results demonstrate that IL-12, IL-18, and TLR 9 agonist CpG oligodeoxynucleotides reduce the level of fusion-mediated regulatory T cell expansion. Our results also demonstrate that sequential stimulation with DC/breast carcinoma fusions and anti-CD3/CD28 results in the marked expansion of activated tumor-specific T cells. These findings suggest that DC/breast carcinoma fusions are effective APCs, but stimulate inhibitory T cells that limit vaccine efficacy. In contrast, exposure to TLR agonists, stimulatory cytokines, and anti-CD3/CD28 enhances vaccine efficacy by limiting the regulatory T cell response and promoting expansion of activated effector cells.

The malignant clone and the bone-marrow environment

Multiple myeloma (MM) is characterized by the clonal expansion of monoclonal immunoglobulin-secreting plasma cells within the bone marrow (BM). It has become clear that the intimate reciprocal relationship between the tumor cell clone and the niches of the BM microenvironment plays a pivotal pathophysiologic role in MM. We and others have identified several new molecular targets and derived novel therapies which induce cytotoxicity against MM cells in the BM milieu, including thalidomide, bortezomib, and lenalidomide. Importantly, these agents induce tumor-cell death, as well as inhibit MM-cell-BM-stromal-cell (BMSC) adhesion and related tumor-cell growth, survival, and migration. Moreover, they block both constitutive and MM-cell binding-induced growth factor and cytokine secretion in BMSCs. Further, they also block tumor angiogenesis and can augment anti-MM immunity. Although all three of these agents are now FDA-approved to treat MM, patients inevitably relapse, and further improvements remain urgently needed. Here we review our current knowledge of the MM cell clone, as well as the impact of the BM microenvironment on tumor-cell growth, survival, migration and drug resistance. Delineating the mechanisms and sequelae of the reciprocal relationship between the MM cell clone, distinct BM extracellular matrix proteins, and accessory cell compartments may provide the basis for new effective therapeutic strategies to re-establish BM homeostasis and thereby improve MM patient outcome.

Phase I/II study of vaccination with electrofused allogeneic dendritic cells/autologous tumor-derived cells in patients with stage IV renal cell carcinoma

In the present study, we assessed the feasibility, toxicity, immunologic response, and clinical efficacy of vaccination with allogeneic dendritic cell (DC)/tumor fusions in patients with metastatic renal cell carcinoma (RCC). Patients with stage IV RCC with accessible tumor lesions or independent therapeutic indications for nephrectomy were eligible for enrollment. Tumors were processed into single cell suspensions and cryopreserved. DCs were generated from adherent peripheral blood mononuclear cells isolated from normal volunteers and cultured with granulocyte macrophage colony-stimulating factor, interleukin-4, and tumor necrosis factor-alpha. DCs were fused to patient derived RCC with serial electrical pulses. Patients received up to 3 vaccinations at a fixed dose of 4x10(7) to 1x10(8) cells administered at 6-week intervals. Twenty-four patients underwent vaccination. Twenty-one and 20 patients were evaluable for immunologic and clinical response, respectively. DCs demonstrated a characteristic phenotype with prominent expression of HLA class II and costimulatory molecules. A mean fusion efficiency of 20% was observed, determined by the percent of cells coexpressing DC and tumor antigens. No evidence of significant treatment related toxicity or auto-immunity was observed. Vaccination resulted in antitumor immune responses in 10/21 evaluable patients as manifested by an increase in CD4 and/or CD8 T-cell expression of interferon-gamma after ex vivo exposure to tumor lysate. Two patients demonstrated a partial clinical response by Response Evaluation Criteria in Solid Tumors criteria and 8 patients had stabilization of their disease. Vaccination of patients with RCC with allogeneic DC/tumor fusions was feasible, well tolerated, and resulted in immunologic and clinical responses in a subset of patients.

Targeted therapy of multiple myeloma based upon tumor-microenvironmental interactions

Multiple myeloma (MM) remains incurable, but recent advances in genomics and proteomics have allowed for advances in our understanding of disease pathogenesis, identified novel therapeutic targets, allowed for molecular classification, and provided the scientific rationale for combining targeted therapies to increase tumor cell cytotoxicity and abrogate drug resistance. Besides these advances, recognition of the role of the bone marrow (BM) milieu in conferring growth, survival, and drug resistance in MM cells, both in laboratory and animal models, has allowed for the establishment of a new treatment paradigm targeting the tumor cell and its microenvironment to overcome drug resistance and improve patient outcomes in MM. In particular, thalidomide, bortezomib, and lenalidamide all overcome conventional drug resistance, not only by directly inducing tumor cell cytotoxicity, but by inhibiting adhesion of MM cells to BM. This abrogates constitutive and MM-binding-induced transcription and secretion of cytokines, inhibits angiogenesis, and augments host anti-MM immunity. These three drugs have rapidly translated from bench to bedside and in treatment protocols of MM, first in patients with relapsed refractory disease, and then alone and in combination in newly diagnosed patients. Promising novel targeted agents include the novel proteasome inhibitor NPI-0052 and the heat shock protein inhibitor KOS-953. Importantly, gene-array, proteomic, and cell-signaling studies have not only helped to identify in vivo mechanisms of action and drug resistance to novel agents, but also aided in the design of promising combination-therapy protocols.

Preclinical development of hybrid cell vaccines for multiple myeloma

Immunotherapy may provide alternative or supplementary treatment of multiple myeloma (MM). We propose that hybrid cells, formed by fusing professional antigen-presenting cells with malignant plasma cells, would induce immune responses capable of mediating tumour regression. The human B-lymphoblastoid cell line, HMy2, was fused in vitro with CD138+ bead-separated myeloma plasma cells from five patients with MM. The hybrid cell lines generated in these studies grew stably in tissue culture, and maintained their phenotypic and functional characteristics, providing self-renewing cell lines with potential for therapeutic vaccination. The hybrid cells stimulated allogeneic and autologous T-cell proliferative responses in vitro to a considerably greater degree than their respective parent myeloma plasma cells, and directly activated both CD4+ and CD8+ T-cell responses. The enhanced T-cell stimulation correlated with expression of CD80 on the hybrid cells, and was inhibited by CTLA4-Ig fusion protein. The hybrid cell lines expressed several tumour-associated antigens known to be expressed in myeloma. These data show that self-replicating cell lines with enhanced immunostimulatory properties and potential for therapeutic vaccination can be generated by in vitro fusion of ex vivo myeloma cells and B-lymphoblastoid cell lines.

Receptor-Mediated Delivery of Antigens to Dendritic Cells: Anticancer Applications

Recently, there has been a surge of interest in the use of ex vivo antigen-pulsed dendritic cells (DCs) in the immunotherapy for cancer. DCs are powerful adjuvants with the ability to prime naive CD4+ and CD8+ T cells. As antigen sources, various preparations, including peptides, proteins, crude tumor lysates, and DCs transfected or transformed with various viruses, have been used. These procedures that involve the isolation of patient DCs and reintroduction after in vitro manipulation are time-consuming and expensive. The DC populations used frequently in ex vivo clinical studies are IL-4 and GM-CSF cultured DCs that may not represent the in vivo DC populations. An attractive method of targeting in vivo DCs is to utilize various ligands or antibodies that bind discrete populations of DCs. These cell surface receptors will direct the antigen to different antigen processing pathways depending on the targeted receptor to induce cytotoxic T cell or T helper responses. This review will discuss the various approaches and receptors that have been used for antigen targeting that may eventually be translated to alternative DC-based immunotherapies.

Fusion of CpG-ODN-stimulating dendritic cells with Lewis lung cancer cells can enhance anti-tumor immune responses

Immunogenicity of tumor cells is generally weak. Therefore, dendritic cells (DCs) have been used to boost anti-tumor responses of DC-based vaccines. DC function is highly dependent on its subsets and the level of its maturation. Nowadays, DC/tumor cell fusion vaccines are already used in clinical trials, and there are numerous studies discussing the effects of cytidine-phosphate-guanosine-containing oligonucleotides (CpG-ODN) on various cell types including DC. CpG-ODN a powerful immuno-stimulant can drive DCs fully mature, thus improve the efficacy of vaccine therapy. There are two simple ways to help load tumor antigens onto DCs by direct contact with cells themselves: fusion or co-culture of DCs with whole tumor cells. In this study, we combined these two approaches to improve the efficacy of DC/tumor cell-based vaccine. Mature DCs are adept at presenting processed Ag to T cells with loss of its capacity to capture Ag, while immature DCs are on the contrary. Our results emphasize the necessity of considering the stage of DC maturation and corresponding choice of tumor antigen delivery when designing approaches for prophylaxis or therapy of tumors using DC-based immunization protocols. We used CpG-ODN-1826-stimulated mature DCs and non-CpG-ODN-stimulating DCs as sources of tumor antigen carriers to investigate the appropriate Ag-loading ways between fusion and co-culture. Our results displayed that DC/tumor vaccine using CpG-ODN-stimulating mature DCs fused, not co-cultured, with tumor cells can generate a consistent and highly effective anti-tumor immune responses in vivo.

Vaccine strategies to treat lymphoproliferative disorders

Lymphoproliferative disorders, including follicular lymphoma (FL), multiple myeloma (MM) and chronic lymphatic leukaemia (CLL), are slowly progressive malignancies which remain incurable despite advances in therapy. Harnessing the immune system to recognise and destroy tumours is a promising new approach to treating these diseases. Dendritic cells (DC) are unique antigen-presenting cells that play a central role in the initiation and direction of immune responses. DC loaded ex vivo with tumour-associated antigens and administered as a vaccine have already shown promise in early clinical trials for a number of lymphoproliferative disorders, but the need for improvement is widely agreed. Recent advances in the understanding of basic DC biology and lessons from early clinical trials have provided exciting new insights into the generation of anti-tumour immune responses and the design of vaccine strategies. In this review we provide an overview of our current understanding of DC biology and their function in patients with lymphoproliferative disorders. We discuss the current status of clinical trials and new approaches to exploit the antigen presenting capacity of DC to design vaccines of the future.