Dendritic cell vaccination combined with CTLA4 blockade in patients with metastatic melanoma

Enhancing Dendritic Cell Cancer Vaccination: The Synergy of Immune Checkpoint Inhibitors in Combined Therapies

Dendritic cell (DC) cancer vaccines are a promising therapeutic approach, leveraging the immune system to fight tumors. These vaccines utilize DCs' ability to present tumor-associated antigens to T cells, triggering a robust immune response. DC vaccine development has progressed through three generations. The first generation involved priming DCs with tumor-associated antigens or messenger RNA outside the body, showing limited clinical success. The second generation improved efficacy by using cytokine mixtures and specialized DC subsets to enhance immunogenicity. The third generation used blood-derived DCs to elicit a stronger immune response. Clinical trials indicate that cancer vaccines have lower toxicity than traditional cytotoxic treatments. However, achieving significant clinical responses with DC immunotherapy remains challenging. Combining DC vaccines with immune checkpoint inhibitors (ICIs), such as anticytotoxic T-lymphocyte Antigen 4 and antiprogrammed death-1 antibodies, has shown promise by enhancing T-cell responses and improving clinical outcomes. These combinations can transform non-inflamed tumors into inflamed ones, boosting ICIs' efficacy. Current research is exploring new checkpoint targets like LAG-3, TIM-3, and TIGIT, considering their potential with DC vaccines. Additionally, engineering T cells with chimeric antigen receptors or T-cell receptors could further augment the antitumor response. This comprehensive strategy aims to enhance cancer immunotherapy, focusing on increased efficacy and improved patient survival rates.

Immunotherapy combination approaches: mechanisms, biomarkers and clinical observations

The approval of the first immune checkpoint inhibitors provided a paradigm shift for the treatment of malignancies across a broad range of indications. Whereas initially, single-agent immune checkpoint inhibition was used, increasing numbers of patients are now treated with combination immune checkpoint blockade, where non-redundant mechanisms of action of the individual agents generally lead to higher response rates. Furthermore, immune checkpoint therapy has been combined with various other therapeutic modalities, including chemotherapy, radiotherapy and other immunotherapeutics such as vaccines, adoptive cellular therapies, cytokines and others, in an effort to maximize clinical efficacy. Currently, a large number of clinical trials test combination therapies with an immune checkpoint inhibitor as a backbone. However, proceeding without inclusion of broad, if initially exploratory, biomarker investigations may ultimately slow progress, as so far, few combinations have yielded clinical successes based on clinical data alone. Here, we present the rationale for combination therapies and discuss clinical data from clinical trials across the immuno-oncology spectrum. Moreover, we discuss the evolution of biomarker approaches and highlight the potential new directions that comprehensive biomarker studies can yield.

Adjuvant dendritic cell therapy in stage IIIB/C melanoma: the MIND-DC randomized phase III trial

Autologous natural dendritic cells (nDCs) treatment can induce tumor-specific immune responses and clinical responses in cancer patients. In this phase III clinical trial (NCT02993315), 148 patients with resected stage IIIB/C melanoma were randomized to adjuvant treatment with nDCs (n = 99) or placebo (n = 49). Active treatment consisted of intranodally injected autologous CD1c+ conventional and plasmacytoid DCs loaded with tumor antigens. The primary endpoint was the 2-year recurrence-free survival (RFS) rate, whereas the secondary endpoints included median RFS, 2-year and median overall survival, adverse event profile, and immunological response The 2-year RFS rate was 36.8% in the nDC treatment group and 46.9% in the control group (p = 0.31). Median RFS was 12.7 months vs 19.9 months, respectively (hazard ratio 1.25; 90% CI: 0.88-1.79; p = 0.29). Median overall survival was not reached in both treatment groups (hazard ratio 1.32; 90% CI: 0.73-2.38; p = 0.44). Grade 3-4 study-related adverse events occurred in 5% and 6% of patients. Functional antigen-specific T cell responses could be detected in 67.1% of patients tested in the nDC treatment group vs 3.8% of patients tested in the control group (p < 0.001). In conclusion, while adjuvant nDC treatment in stage IIIB/C melanoma patients generated specific immune responses and was well tolerated, no benefit in RFS was observed.

Advances in dendritic cell vaccination therapy of cancer

Traditionally, vaccines have helped eradication of several infectious diseases and also saved millions of lives in the human history. Those prophylactic vaccines have acted through inducing immune responses against a live attenuated, killed organism or antigenic subunits to protect the recipient against a real infection caused by the pathogenic microorganism. Nevertheless, development of anticancer vaccines as valuable targets in human health has faced challenges and requires further optimizations. Dendritic cells (DCs) are the most potent antigen presenting cells (APCs) that play essential roles in tumor immunotherapies through induction of CD8+ T cell immunity. Accordingly, various strategies have been tested to employ DCs as therapeutic vaccines for exploiting their activity against tumor cells. Application of whole tumor cells or purified/recombinant antigen peptides are the most common approaches for pulsing DCs, which then are injected back into the patients. Although some hopeful results are reported for a number of DC vaccines tested in animal and clinical trials of cancer patients, such approaches are still inefficient and require optimization. Failure of DC vaccination is postulated due to immunosuppressive tumor microenvironment (TME), overexpression of checkpoint proteins, suboptimal avidity of tumor-associated antigen (TAA)-specific T lymphocytes, and lack of appropriate adjuvants. In this review, we have an overview of the current experiments and trials evaluated the anticancer efficacy of DC vaccination as well as focusing on strategies to improve their potential including combination therapy with immune checkpoint inhibitors (ICIs).

Phase I/II study of multipeptide cancer vaccine IMA901 after single-dose cyclophosphamide in Japanese patients with advanced renal cell cancer with long-term follow up

BACKGROUND

IMA901 is the first therapeutic vaccine for renal cell cancer (RCC). It contains multiple tumor-associated peptides (TUMAPs) that are naturally present in human cancers.

METHODS

In a phase I/II study, we treated a total of 10 Japanese patients with advanced RCC who were human leukocyte antigen A (HLA-A)*02 +. Vaccination involved i.d. injection of GM-CSF (75 μg), followed within 15-30 min by i.d. injection of IMA901 (containing 413 μg of each peptide). No treatment with either anticancer agents or immunosuppressants was allowed within 4 weeks before entering the trial. Patients were scheduled to receive 7 vaccinations during the first 5 weeks of treatment (induction period), followed by 10 further vaccinations at 3-week intervals for up to 30 weeks (maintenance period). The primary endpoints were safety and tolerability, while the secondary endpoints were PFS, OS, and immunogenicity.

RESULTS

There were no treatment-related serious adverse events or deaths during the study period. When the response was assessed after 4 months, 10% of patients showed a partial response, 80% had stable disease, and 10% had progressive disease. Among patients in whom the T-cell response was analyzed, five patients showed a vaccine-induced T-cell response against at least one HLA class I-restricted TUMAP and two patients had T-cell responses to multiple TUMAPs. PFS was 5.5 months and OS was 18 months.

CONCLUSIONS

This study demonstrated the safety and tolerability of IMA901 vaccine in Japanese RCC patients, and also showed that vaccination elicited an immune response.

The effects of dendritic cell-based vaccines in the tumor microenvironment: Impact on myeloid-derived suppressor cells

Dendritic cells (DCs) are a heterogenous population of professional antigen presenting cells whose main role is diminished in a variety of malignancies, including cancer, leading to ineffective immune responses. Those mechanisms are inhibited due to the immunosuppressive conditions found in the tumor microenvironment (TME), where myeloid-derived suppressor cells (MDSCs), a heterogeneous population of immature myeloid cells known to play a key role in tumor immunoevasion by inhibiting T-cell responses, are extremely accumulated. In addition, it has been demonstrated that MDSCs not only suppress DC functions, but also their maturation and development within the myeloid linage. Considering that an increased number of DCs as well as the improvement in their functions boost antitumor immunity, DC-based vaccines were developed two decades ago, and promising results have been obtained throughout these years. Therefore, the remodeling of the TME promoted by DC vaccination has also been explored. Here, we aim to review the effectiveness of different DCs-based vaccines in murine models and cancer patients, either alone or synergistically combined with other treatments, being especially focused on their effect on the MDSC population.

What’s next for cancer vaccines

Cancer vaccines have been shown clinically to drive tumor-reactive cell activation, proliferation, and effector function. Unfortunately, tumor eradication by treatment with cancer vaccines has been unsuccessful in many patients. Critical steps are under way to improve vaccine efficacy and combine them with immunotherapy and standard-of-care treatments.

The soldiers needed to be awakened: Tumor-infiltrating immune cells

In the tumor microenvironment, tumor-infiltrating immune cells (TIICs) are a key component. Different types of TIICs play distinct roles. CD8+ T cells and natural killer (NK) cells could secrete soluble factors to hinder tumor cell growth, whereas regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) release inhibitory factors to promote tumor growth and progression. In the meantime, a growing body of evidence illustrates that the balance between pro- and anti-tumor responses of TIICs is associated with the prognosis in the tumor microenvironment. Therefore, in order to boost anti-tumor response and improve the clinical outcome of tumor patients, a variety of anti-tumor strategies for targeting TIICs based on their respective functions have been developed and obtained good treatment benefits, including mainly immune checkpoint blockade (ICB), adoptive cell therapies (ACT), chimeric antigen receptor (CAR) T cells, and various monoclonal antibodies. In recent years, the tumor-specific features of immune cells are further investigated by various methods, such as using single-cell RNA sequencing (scRNA-seq), and the results indicate that these cells have diverse phenotypes in different types of tumors and emerge inconsistent therapeutic responses. Hence, we concluded the recent advances in tumor-infiltrating immune cells, including functions, prognostic values, and various immunotherapy strategies for each immune cell in different tumors.

Dendritic Cell-Based Immunotherapy in Hot and Cold Tumors

Dendritic cells mediate innate and adaptive immune responses and are directly involved in the activation of cytotoxic T lymphocytes that kill tumor cells. Dendritic cell-based cancer immunotherapy has clinical benefits. Dendritic cell subsets are diverse, and tumors can be hot or cold, depending on their immunogenicity; this heterogeneity affects the success of dendritic cell-based immunotherapy. Here, we review the ontogeny of dendritic cells and dendritic cell subsets. We also review the characteristics of hot and cold tumors and briefly introduce therapeutic trials related to hot and cold tumors. Lastly, we discuss dendritic cell-based cancer immunotherapy in hot and cold tumors.

Dendritic cell transfer for cancer immunotherapy

Dendritic cells (DCs) play a major role in cancer immunosurveillance as they bridge innate and adaptive immunity by detecting tumor-associated antigens and presenting them to T lymphocytes. The adoptive transfer of antigen loaded DCs has been proposed as an immunotherapeutic approach for the treatment of various types of cancer. Nevertheless, despite promising preclinical data, the therapeutic efficacy of DC transfer is still deceptive in cancer patients. Here we summarize recent findings in DC biology with a special focus on the development of actionable therapeutic strategies and discuss experimental and clinical approaches that aim at improving the efficacy of DC-based immunotherapies, including, but not limited to, optimized DC production and antigen loading, stimulated maturation, the co-treatment with additional immunotherapies, as well as the inhibition of DC checkpoints.

Dendritic cell-based cancer immunotherapy in the era of immune checkpoint inhibitors: From bench to bedside

Dendritic cells (DCs) can present tumoral antigens to T-cells and stimulate T-cell-mediated anti-tumoral immune responses. In addition to uptaking, processing, and presenting tumoral antigens to T-cells, co-stimulatory signals have to be established between DCs with T-cells to develop anti-tumoral immune responses. However, most of the tumor-infiltrated immune cells are immunosuppressive in the tumor microenvironment (TME), paving the way for immune evasion of tumor cells. This immunosuppressive TME has also been implicated in suppressing the DC-mediated anti-tumoral immune responses, as well. Various factors, i.e., immunoregulatory cells, metabolic factors, tumor-derived immunosuppressive factors, and inhibitory immune checkpoint molecules, have been implicated in developing the immunosuppressive TME. Herein, we aimed to review the biology of DCs in developing T-cell-mediated anti-tumoral immune responses, the significance of immunoregulatory cells in the TME, metabolic barriers contributing to DCs dysfunction in the TME, tumor-derived immunosuppressive factors, and inhibitory immune checkpoint molecules in DC-based cell therapy outcomes. With reviewing the ongoing clinical trials, we also proposed a novel therapeutic strategy to increase the efficacy of DC-based cell therapy. Indeed, the combination of DC-based cell therapy with monoclonal antibodies against novel immune checkpoint molecules can be a promising strategy to increase the response rate of patients with cancers.

Immunological responses to adjuvant vaccination with combined CD1c+ myeloid and plasmacytoid dendritic cells in stage III melanoma patients

We evaluated the immunological responses of lymph-node involved (stage III) melanoma patients to adjuvant dendritic cell vaccination with subsets of naturally occurring dendritic cells (nDCs). Fifteen patients with completely resected stage III melanoma were randomized to receive adjuvant dendritic cell vaccination with CD1c⁺ myeloid dendritic cells (cDC2s), plasmacytoid dendritic cells (pDCs) or the combination. Immunological response was the primary endpoint and secondary endpoints included safety and survival. In 80% of the patients, antigen-specific CD8⁺ T cells were detected in skin test-derived T cells and in 55% of patients, antigen-specific CD8⁺ T cells were detectable in peripheral blood. Functional interferon-γ-producing T cells were found in the skin test of 64% of the patients. Production of nDC vaccines meeting release criteria was feasible for all patients. Vaccination only induced grade 1-2 adverse events, mainly consisting of fatigue. In conclusion, adjuvant dendritic cell vaccination with cDC2s and/or pDCs is feasible, safe and induced immunological responses in the majority of stage III melanoma patients.

T cell receptor (TCR) signaling in health and disease

Interaction of the T cell receptor (TCR) with an MHC-antigenic peptide complex results in changes at the molecular and cellular levels in T cells. The outside environmental cues are translated into various signal transduction pathways within the cell, which mediate the activation of various genes with the help of specific transcription factors. These signaling networks propagate with the help of various effector enzymes, such as kinases, phosphatases, and phospholipases. Integration of these disparate signal transduction pathways is done with the help of adaptor proteins that are non-enzymatic in function and that serve as a scaffold for various protein-protein interactions. This process aids in connecting the proximal to distal signaling pathways, thereby contributing to the full activation of T cells. This review provides a comprehensive snapshot of the various molecules involved in regulating T cell receptor signaling, covering both enzymes and adaptors, and will discuss their role in human disease.

Blood DCs activated with R848 and poly(I:C) induce antigen-specific immune responses against viral and tumor-associated antigens

Monocyte-derived Dendritic cells (DCs) have successfully been employed to induce immune responses against tumor-associated antigens in patients with various cancer entities. However, objective clinical responses have only been achieved in a minority of patients. Additionally, generation of GMP-compliant DCs requires time- and labor-intensive cell differentiation. In contrast, Blood DCs (BDCs) require only minimal ex vivo handling, as differentiation occurs in vivo resulting in potentially better functional capacities and survival. We aimed to identify a protocol for optimal in vitro activation of BDCs including the three subsets pDCs, cDC1s, and cDC2s. We evaluated several TLR ligand combinations and demonstrated that polyinosinic:polycytidylic acid [poly(I:C)] and R848, ligands for TLR3 and TLR7/8, respectively, constituted the optimal combination for inducing a positive co-stimulatory profile in all BDC subsets. In addition, TLR3 and TLR7/8 activation led to high secretion of IFN-α and IL-12p70. Simultaneous as opposed to separate tailored activation of pDCs and cDCs increased immunostimulatory capacities, suggesting that BDC subsets engage in synergistic cross-talk during activation. Stimulation of BDCs with this protocol resulted in enhanced migration, high NK-cell activation, and potent antigen-specific T-cell induction.

We conclude that simultaneous activation of all BDC subsets with a combination of R848 + poly(I:C) generates highly immunostimulatory DCs. These results support further investigation and clinical testing, as standalone or in conjunction with other immunotherapeutic strategies including adoptive T-cell transfer and checkpoint inhibition.

Modulation of the immune response by heterogeneous monocytes and dendritic cells in lung cancer

Different subpopulations of monocytes and dendritic cells (DCs) may have a key impact on the modulation of the immune response in malignancy. In this review, we summarize the monocyte and DCs heterogeneity and their function in the context of modulating the immune response in cancer. Subgroups of monocytes may play opposing roles in cancer, depending on the tumour growth and progression as well as the type of cancer. Monocytes can have pro-tumour and anti-tumour functions and can also differentiate into monocyte-derived DCs (moDCs). MoDCs have a similar antigen presentation ability as classical DCs, including cross-priming, a process by which DCs activate CD8 T-cells by cross-presenting exogenous antigens. DCs play a critical role in generating anti-tumour CD8 T-cell immunity. DCs have plastic characteristics and show distinct phenotypes depending on their mature state and depending on the influence of the tumour microenvironment. MoDCs and other DC subsets have been attracting increased interest owing to their possible beneficial effects in cancer immunotherapy. This review also highlights key strategies deploying specific DC subpopulations in combination with other therapies to enhance the anti-tumour response and summarizes the latest ongoing and completed clinical trials using DCs in lung cancer.

Vaccines as Priming Tools for T Cell Therapy for Epithelial Cancers

Simple Summary

Despite all of the impressive progress that has been made in the field of cancer therapy, cancer continues to devastate the lives of many. Recent efforts have focused on taking advantage of the patients’ immune system, modifying and employing it to attack cancer cells more efficiently. Therapeutic cancer vaccines are part of the armamentarium used for that purpose. In this review, we discuss the role of the immune system in the fight against cancer, the various strategies that are aimed at engaging the immune system, and how therapeutic cancer vaccines can be used as a self-standing strategy or as a means to leverage other immunotherapies to deliver more efficient results. We elaborate on the obstacles that are present, why immune therapies do not work equally well on all patients, and how vaccines can potentially play a role in improving cancer outcomes.

Abstract

Impressive progress has recently been made in the field of cancer immunotherapy with the adoptive transfer of T cells, a successful personalized strategy, and checkpoint inhibitors (CPI) having extended the survival of numerous patients. However, not all patients have been able to benefit from these innovations. A key determinant of the responsiveness to cancer immunotherapies is the presence of T cells within the tumors. These tumor-infiltrating lymphocytes (TILs) are crucial in controlling tumor growth and their activity is being potentiated by immunotherapies. Although some epithelial cancers are associated with spontaneous T-cell and B-cell responses, which makes them good candidates for immunotherapies, it remains to create strategies that would promote lymphocyte infiltration and enable sustained immune responses in immune-resistant tumors. Therapeutic cancer vaccines hold the potential of being able to render “cold”, poorly infiltrated tumors into “hot” tumors that would be receptive to cellular immunotherapies. In this review, we elaborate on the obstacles that need to be overcome and the strategies that are being explored to that end, including various types of antigen repertoires and different vaccine platforms and combinations with other available treatments.

Dendritic Cells and Cancer Immunotherapy: The Adjuvant Effect

Dendritic cells (DCs) are immune specialized cells playing a critical role in promoting immune response against antigens, and may represent important targets for therapeutic interventions in cancer. DCs can be stimulated ex vivo with pro-inflammatory molecules and loaded with tumor-specific antigen(s). Protocols describing the specific details of DCs vaccination manufacturing vary widely, but regardless of the employed protocol, the DCs vaccination safety and its ability to induce antitumor responses is clearly established. Many years of studies have focused on the ability of DCs to provide overall survival benefits at least for a selection of cancer patients. Lessons learned from early trials lead to the hypothesis that, to improve the efficacy of DCs-based immunotherapy, this should be combined with other treatments. Thus, the vaccine’s ultimate role may lie in the combinatorial approaches of DCs-based immunotherapy with chemotherapy and radiotherapy, more than in monotherapy. In this review, we address some key questions regarding the integration of DCs vaccination with multimodality therapy approaches for cancer treatment paradigms.

Recent Advances and Future Perspective of DC-Based Therapy in NSCLC

Current treatment for patients with non-small-cell lung cancer (NSCLC) is suboptimal since therapy is only effective in a minority of patients and does not always induce a long-lasting response. This highlights the importance of exploring new treatment options. The clinical success of immunotherapy relies on the ability of the immune system to mount an adequate anti-tumor response. The activation of cytotoxic T cells, the effector immune cells responsible for tumor cell killing, is of paramount importance for the immunotherapy success. These cytotoxic T cells are primarily instructed by dendritic cells (DCs). DCs are the most potent antigen-presenting cells (APCs) and are capable of orchestrating a strong anti-cancer immune response. DC function is often suppressed in NSCLC. Therefore, resurrection of DC function is an interesting approach to enhance anti-cancer immune response. Recent data from DC-based treatment studies has given rise to the impression that DC-based treatment cannot induce clinical benefit in NSCLC by itself. However, these are all early-phase studies that were mainly designed to study safety and were not powered to study clinical benefit. The fact that these studies do show that DC-based therapies were well-tolerated and could induce the desired immune responses, indicates that DC-based therapy is still a promising option. Especially combination with other treatment modalities might enhance immunological response and clinical outcome. In this review, we will identify the possibilities from current DC-based treatment trials that could open up new venues to improve future treatment.

TriMix and tumor antigen mRNA electroporated dendritic cell vaccination plus ipilimumab: link between T-cell activation and clinical responses in advanced melanoma

Background

We previously reported that dendritic cell-based mRNA vaccination plus ipilimumab (TriMixDC-MEL IPI) results in an encouraging rate of tumor responses in patients with pretreated advanced melanoma. Here, we report the TriMixDC-MEL IPI-induced T-cell responses detected in the peripheral blood.

Methods

Monocyte-derived dendritic cells electroporated with mRNA encoding CD70, CD40 ligand, and constitutively active TLR4 (TriMix) as well as the tumor-associated antigens tyrosinase, gp100, MAGE-A3, or MAGE-C2 were administered together with IPI for four cycles. For 18/39 patients, an additional vaccine was administered before the first IPI administration. We evaluated tumor-associated antigen specific T-cell responses in previously collected peripheral blood mononuclear cells, available from 15 patients.

Results

Vaccine-induced enzyme-linked immunospot assay responses detected after in vitro T-cell stimulation were shown in 12/15 patients. Immune responses detected in patients with a complete or partial response were significantly stronger and broader, and exhibited a higher degree of multifunctionality compared with responses in patients with stable or progressive disease. CD8+ T-cell responses from patients with an ongoing clinical response, either elicited by TriMixDC-MEL IPI or on subsequent pembrolizumab treatment, exhibited the highest degree of multifunctionality.

Conclusions

TriMixDC-MEL IPI treatment results in robust CD8+ T-cell responses in a meaningful portion of stage III or IV melanoma patients, and obviously in patients with a clinical response. The levels of polyfunctional and multiantigen T-cell responses measured in patients with a complete response, particularly in patients evidently cured after 5+ years of follow-up, may provide a benchmark for the level of immune stimulation needed to achieve a durable clinical remission.

Trial registration number

NCT01302496.

Randomized phase II trial of lymphodepletion plus adoptive cell transfer of tumor-infiltrating lymphocytes, with or without dendritic cell vaccination, in patients with metastatic melanoma

BACKGROUND

The adoptive transfer of tumor-infiltrating lymphocytes (TIL) has demonstrated robust efficacy in metastatic melanoma patients. Tumor antigen-loaded dendritic cells (DCs) are believed to optimally activate antigen-specific T lymphocytes. We hypothesized that the combined transfer of TIL, containing a melanoma antigen recognized by T cells 1 (MART-1) specific population, with MART-1-pulsed DC will result in enhanced proliferation and prolonged survival of transferred MART-1 specific T cells in vivo ultimately leading to improved clinical responses.

DESIGN

We tested the combination of TIL and DC in a phase II clinical trial of patients with advanced stage IV melanoma. HLA-A0201 patients whose early TIL cultures demonstrated reactivity to MART-1 peptide were randomly assigned to receive TIL alone or TIL +DC pulsed with MART-1 peptide. The primary endpoint was to evaluate the persistence of MART-1 TIL in the two arms. Secondary endpoints were to evaluate clinical response and survival.

RESULTS

Ten patients were given TIL alone while eight patients received TIL+DC vaccine. Infused MART-1 reactive CD8⁺ TIL were tracked in the blood over time by flow cytometry and results show good persistence in both arms, with no difference in the persistence of MART-1 between the two arms. The objective response rate was 30% (3/10) in the TIL arm and 50% (4/8) in the TIL+DC arm. All treatments were well tolerated.

CONCLUSIONS

The combination of TIL +DC showed no difference in the persistence of MART-1 TIL compared with TIL therapy alone. Although more patients showed a clinical response to TIL+DC therapy, this study was not powered to resolve differences between groups.

TRIAL REGISTRATION NUMBER

NCT00338377.

Quality Verification with a Cluster-Controlled Manufacturing System to Generate Monocyte-Derived Dendritic Cells

Dendritic cell (DC) vaccines for cancer immunotherapy have been actively developed to improve clinical efficacy. In our previous report, monocyte−derived DCs induced by interleukin (IL)−4 with a low−adherence dish (low−adherent IL-4−DCs: la−IL-4−DCs) improved the yield and viability, as well as relatively prolonged survival in vitro, compared to IL-4−DCs developed using an adherent culture protocol. However, la−IL-4−DCs exhibit remarkable cluster formation and display heterogeneous immature phenotypes. Therefore, cluster formation in la−IL-4−DCs needs to be optimized for the clinical development of DC vaccines. In this study, we examined the effects of cluster control in the generation of mature IL-4−DCs, using cell culture vessels and measuring spheroid formation, survival, cytokine secretion, and gene expression of IL-4−DCs. Mature IL-4−DCs in cell culture vessels (cluster−controlled IL-4−DCs: cc−IL-4−DCs) displayed increased levels of CD80, CD86, and CD40 compared with that of la−IL-4−DCs. cc−IL-4−DCs induced antigen−specific cytotoxic T lymphocytes (CTLs) with a human leukocyte antigen (HLA)−restricted melanoma antigen recognized by T cells 1 (MART−1) peptide. Additionally, cc−IL-4−DCs produced higher levels of IFN−γ, possessing the CTL induction. Furthermore, DNA microarrays revealed the upregulation of BCL2A1, a pro−survival gene. According to these findings, the cc−IL-4−DCs are useful for generating homogeneous and functional IL-4−DCs that would be expected to promote long−lasting effects in DC vaccines.

Immune checkpoints and cancer development: Therapeutic implications and future directions

Over the past few decades, different inhibitory receptors have been identified, which have played prominent roles in reducing anti-tumor immune responses. The role of immune checkpoint inhibitors in cancer was revealed by critical blockade of the cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) and programmed cell death protein-1 (PD-1) checkpoints. Immune checkpoint inhibitors, including anti-PD-1 (nivolumab and pembrolizumab), anti-PD-L1 (Atezolizumab, avelumab, and duravulumab), and anti-CTLA-4 (ipilimumab, tremelimumab), are currently FDA-approved treatment options for a broad range of cancer types. However, regarding immunotherapy advances in recent years, most studies have been focused on finding the antibodies against other inhibitory immune checkpoints in the tumor microenvironment such as lymphocyte activation gene-3 (LAG-3), T cell immunoglobulin, and mucin domain 3 (TIM-3), B7-homolog 3 (B7-H3), V-domain immunoglobulin-containing suppressor of T-cell activation (VISTA), diacylglycerol kinase-α (DGK-α), T cell immunoglobulin and ITIM domain (TIGIT), and B and T lymphocyte attenuator (BTLA). This immune checkpoint exerts differential inhibitory impacts on various types of lymphocytes. The suppression of immune responses demonstrates a surprising synergy with PD-1. Therefore, most antibodies against these immune checkpoints are undertaking clinical trials for cancer immunotherapy of advanced solid tumors and hematologic malignancies. In this review, we will summarize recent findings of immune checkpoint and the role of monoclonal antibodies in cancer immunotherapy targeting these receptors.

Emerging dynamics pathways of response and resistance to PD-1 and CTLA-4 blockade: tackling uncertainty by confronting complexity

Immune checkpoint inhibitors provide considerable therapeutic benefit in a range of solid cancers as well as in a subgroup of hematological malignancies. Response rates are however suboptimal, and despite considerable efforts, predicting response to immune checkpoint inhibitors ahead of their administration in a given patient remains elusive. The study of the dynamics of the immune system and of the tumor under immune checkpoint blockade brought insight into the mechanisms of action of these therapeutic agents. Equally relevant are the mechanisms of adaptive resistance to immune checkpoint inhibitors that have been uncovered through this approach. In this review, we discuss the dynamics of the immune system and of the tumor under immune checkpoint blockade emanating from recent studies on animal models and humans. We will focus on mechanisms of action and of resistance conveying information predictive of therapeutic response.

TIL therapy broadens the tumor-reactive CD8(+) T cell compartment in melanoma patients

There is strong evidence that both adoptive T cell transfer and T cell checkpoint blockade can lead to regression of human melanoma. However, little data are available on the effect of these cancer therapies on the tumor-reactive T cell compartment. To address this issue we have profiled therapy-induced T cell reactivity against a panel of 145 melanoma-associated CD8(+) T cell epitopes. Using this approach, we demonstrate that individual tumor-infiltrating lymphocyte cell products from melanoma patients contain unique patterns of reactivity against shared melanoma-associated antigens, and that the combined magnitude of these responses is surprisingly low. Importantly, TIL therapy increases the breadth of the tumor-reactive T cell compartment in vivo, and T cell reactivity observed post-therapy can almost in full be explained by the reactivity observed within the matched cell product. These results establish the value of high-throughput monitoring for the analysis of immuno-active therapeutics and suggest that the clinical efficacy of TIL therapy can be enhanced by the preparation of more defined tumor-reactive T cell products.

Personalized neoantigen pulsed dendritic cell vaccine for advanced lung cancer

Neoantigens are considered to be ultimate target of tumor immunotherapy due to their high tumor specificity and immunogenicity. Dendritic cell (DCs) vaccines based on neoantigens have exciting effects in treatment of some malignant tumors and are a promising therapeutic modality. Lung cancer is a lethal disease with the highest morbidity and mortality rate in the world. Despite the rapid development of targeted therapy and immune checkpoint inhibitors for lung cancer in recent years, their efficacy is still unsatisfactory overall. Therefore, there is an urgent unmet clinical need for lung cancer treatment. Here, we attempted to treat lung cancer using a personalized neoantigen peptide-pulsed autologous DC vaccine and conducted a single-arm, 2 medical centers, pilot study initiated by the investigator (ChiCTR-ONC-16009100, NCT02956551). The patients enrolled were patients with heavily treated metastatic lung cancer. Candidate neoantigens were derived from whole-exome sequencing and RNA sequencing of fresh biopsy tissues as well as bioinformatics analysis. A total of 12 patients were enrolled in this study. A total of 85 vaccine treatments were administered with a median value of 5 doses/person (range: 3-14 doses/person). In total, 12-30 peptide-based neoantigens were selected for each patient. All treatment-related adverse events were grade 1-2 and there were no delays in dosing due to toxic effects. The objective effectiveness rate was 25%; the disease control rate was 75%; the median progression-free survival was 5.5 months and the median overall survival was 7.9 months. This study provides new evidence for neoantigen vaccine therapy and new therapeutic opportunities for lung cancer treatment.

Cutaneous melanoma and the immunotherapy revolution (Review)

In a relatively short period of time, treatment strategies for metastatic melanoma have radically changed leading to an unprecedented improvement in patient survival. In this period, immunotherapy options have evolved from cytokine‑based approaches to antibody‑mediated inhibition of immune checkpoints, cancer vaccines and pharmacological modulation of the melanoma microenvironment. Combination of immunotherapy strategies and the association of immune checkpoint inhibitors (ICIs) with BRAF V600 targeted therapy show encouraging results. The future of drug development in this field is promising. The comprehension of primary and acquired resistance mechanisms to ICIs and the dissection of melanoma immunobiology will be instrumental for the development of new treatment strategies and to improve clinical trial design. Moreover, biomarker discovery will help patient stratification and management during immunotherapy treatment. In this review, we summarize landmark clinical trials of immune checkpoint inhibitors in advanced melanoma and discuss the rational for immunotherapy combinations. Immunotherapy approaches at early stage of clinical development and recent advances in melanoma immunotherapy biomarker development are also discussed.

Antitumour dendritic cell vaccination in a priming and boosting approach

Mobilizing antitumour immunity through vaccination potentially constitutes a powerful anticancer strategy but has not yet provided robust clinical benefits in large patient populations. Although major hurdles still exist, we believe that currently available strategies for vaccines that target dendritic cells or use them to present antitumour antigens could be integrated into existing clinical practice using prime-boost approaches. In the priming phase, these approaches capitalize on either standard treatment modalities to trigger in situ vaccination and release tumour antigens or vaccination with dendritic cells loaded with tumour lysates or patient-specific neoantigens. In a second boost phase, personalized synthetic vaccines specifically boost T cells that were triggered during the priming phase. This immunotherapy approach has been enabled by the substantial recent improvements in dendritic cell vaccines. In this Perspective, we discuss these improvements, highlight how the prime-boost approach can be translated into clinical practice and provide solutions for various anticipated hurdles.

Breakthrough concepts in immune-oncology: Cancer vaccines at the bedside

Clinical approval of the immune checkpoint blockade (ICB) agents for multiple cancer types has reinvigorated the long-standing work on cancer vaccines. In the pre-ICB era, clinical efforts focused on the Ag, the adjuvants, the formulation, and the mode of delivery. These translational efforts on therapeutic vaccines range from cell-based (e.g., dendritic cells vaccine Sipuleucel-T) to DNA/RNA-based platforms with various formulations (liposome), vectors (Listeria monocytogenes), or modes of delivery (intratumoral, gene gun, etc.). Despite promising preclinical results, cancer vaccine trials without ICB have historically shown little clinical activity. With the anticipation and expansion of combinatorial immunotherapeutic trials with ICB, the cancer vaccine field has entered the personalized medicine arena with recent advances in immunogenic neoantigen-based vaccines. In this article, we review the literature to organize the different cancer vaccines in the clinical space, and we will discuss their advantages, limits, and recent progress to overcome their challenges. Furthermore, we will also discuss recent preclinical advances and clinical strategies to combine vaccines with checkpoint blockade to improve therapeutic outcome and present a translational perspective on future directions.

Ex vivo-generated dendritic cell-based vaccines in melanoma: the role of nanoparticulate delivery systems

Melanoma is a poor immunogenic cancer and many treatment strategies have been used to enhance specific or nonspecific immunity against it. Dendritic cell (DC)-based cancer vaccine is the most effective therapies that have been used so far. Meanwhile, the efficacy of DC-based immunotherapy relies on critical factors relating to DCs such as the state of maturation and proper delivery of antigens. In this regard, the use of nanoparticulate delivery systems for effective delivery of antigen to ex vivo-generated DC-based vaccines that also poses adjuvanticity would be an ideal approach. In this review article, we attempt to summarize the role of different types of nanoparticulate antigen delivery systems used in the development of ex vivo-generated DC-based vaccines against melanoma and describe their adjuvanticity in mediation of DC maturation, cytoplasmic presentation of antigens to MHC class I molecules, which led to potent antigen-specific immune responses. As were represented, cationic liposomes were the most used approach, which suggest its potential applicability as delivery systems for further experiments in combination with either adjuvants or monoclonal antibodies.

Response and survival of metastatic melanoma patients treated with immune checkpoint inhibition for recurrent disease on adjuvant dendritic cell vaccination

Vaccination with autologous dendritic cells (DC) loaded ex vivo with melanoma-associated antigens is currently being tested as an adjuvant treatment modality for resected locoregional metastatic (stage III) melanoma. Based on its mechanism of action, DC vaccination might potentiate the clinical efficacy of concurrent or sequential immune checkpoint inhibition (ICI). The purpose of this study was to determine the efficacy of ICI administered following recurrent disease during, or after, adjuvant DC vaccination. To this end, we retrospectively analyzed clinical responses of 51 melanoma patients with either irresectable stage III or stage IV disease treated with first- or second-line ICI following recurrence on adjuvant DC vaccination. Patients were analyzed according to the form of ICI administered: PD-1 inhibition monotherapy (nivolumab or pembrolizumab), ipilimumab monotherapy or combined treatment with ipilimumab and nivolumab. Treatment with first- or second-line PD-1 inhibition monotherapy after recurrence on adjuvant DC vaccination resulted in a response rate of 52%. In patients treated with ipilimumab monotherapy and ipilimumab-nivolumab response rates were 35% and 75%, respectively. In conclusion, ICI is effective in melanoma patients with recurrent disease on adjuvant DC vaccination.

Antimesothelioma Immunotherapy by CTLA-4 Blockade Depends on Active PD1-Based TWIST1 Vaccination

Checkpoint immunotherapy is a major breakthrough for cancer treatment, yet its efficacy is often limited against many types of malignancies, including malignant mesothelioma. Considering that the immunotherapeutic efficacy depends on immunosurveillance, we sought to develop an active immunization method to break immune tolerance to tumor self-antigen. Here, we demonstrated that TWIST1, the basic helix-loop-helix transcription factor, was associated with human mesothelioma tumorigenesis and required for the invasion and metastasis of mesothelioma in the immune-competent murine AB1 model. When conventional TWIST1 vaccines were not effective in vivo, programmed cell death protein 1 (PD1)-based vaccination provided prophylactic control by inducing long-lasting TWIST1-specific T cell responses against both subcutaneous and metastatic mesothelioma lethal challenges. Furthermore, while CTLA-4 blockade alone did not show any immunotherapeutic efficacy against established mesothelioma, its combination with PD1-based vaccination resulted in 60% complete remission. Mechanistically, these functional T cells recognized a novel highly conserved immunodominant TWIST1 epitope, exhibited cytotoxic activity and long-term memory, and led to durable tumor regression and survival benefit against established AB1 mesothelioma and 4T1 breast cancer. We concluded that PD1-based vaccination controls mesothelioma by breaking immune tolerance to the tumor self-antigen TWIST1. Our results warrant clinical development of the PD1-based vaccination to enhance immunotherapy against a wide range of TWIST1-expressing tumors.

Autologous monocyte-derived DC vaccination combined with cisplatin in stage III and IV melanoma patients: a prospective, randomized phase 2 trial

BACKGROUND

Autologous dendritic cell (DC) vaccines can induce tumor-specific T cells, but their effect can be counteracted by immunosuppressive mechanisms. Cisplatin has shown immunomodulatory effects in vivo which may enhance efficacy of DC vaccination.

METHODS

This is a prospective, randomized, open-label phase 2 study (NCT02285413) including stage III and IV melanoma patients receiving 3 biweekly vaccinations of gp100 and tyrosinase mRNA-loaded monocyte-derived DCs with or without cisplatin. Primary objectives were to study immunogenicity and feasibility, and secondary objectives were to assess toxicity and survival.

RESULTS

Twenty-two stage III and 32 stage IV melanoma patients were analyzed. Antigen-specific CD8⁺ T cells were found in 44% versus 67% and functional T cell responses in 28% versus 19% of skin-test infiltrating lymphocytes in patients receiving DC vaccination with and without cisplatin, respectively. Four patients stopped cisplatin because of toxicity and continued DC monotherapy. No therapy-related grade 3 or 4 adverse events occurred due to DC monotherapy. During combination therapy, one therapy-related grade 3 adverse event, decompensated heart failure due to fluid overload, occurred. The clinical outcome parameters did not clearly suggest significant differences.

CONCLUSIONS

Combination of DC vaccination and cisplatin in melanoma patients is feasible and safe, but does not seem to result in more tumor-specific T cell responses or improved clinical outcome, when compared to DC vaccination monotherapy.

Immune checkpoint inhibitor-associated pituitary-adrenal dysfunction: A systematic review and meta-analysis

With the growing use of immune checkpoint inhibitors (ICIs), case reports of rare yet life-threatening pituitary-adrenal dysfunctions, particularly for hypopituitarism, are increasingly being published. In this analysis, we focus on these events by including the most recent publications and reports from early phase I/II and phase III clinical trials and comparing the incidence and risks across different ICI regimens. PubMed, Embase, and the Cochrane Library were systematically searched from inception to April 2019 for clinical trials that reported on pituitary-adrenal dysfunction. The rates of events, odds ratios (ORs), and 95% confidence intervals (CIs) were obtained using random effects meta-analysis. The analyses included data from 160 trials involving 40 432 participants. The rate was 2.43% (95% CI, 1.73%-3.22%) for all-grade adrenal insufficiency and 3.25% (95% CI, 2.15%-4.51%) for hypophysitis. Compared with the placebo or other therapeutic regimens, ICI agents were associated with a higher incidence of serious-grade adrenal insufficiency (OR 3.19, 95% CI, 1.84 to 5.54) and hypophysitis (OR 4.77, 95% CI, 2.60 to 8.78). Among 71 serious-grade hypopituitarism instances in 12 336 patients, there was a significant association between ICIs and hypopituitarism (OR 3.62, 95% CI, 1.86 to 7.03). Substantial heterogeneity was noted across the studies for the rates of these events, which in part was attributable to the different types of ICIs and varied phases of the clinical trials. Although the rates of these events were low, the risk was increased following ICI-based treatment, particularly for CTLA-4 inhibitors, which were associated with a higher incidence of pituitary-adrenal dysfunction than PD-1/PD-L1 inhibitors.

The impact of CTLA-4 blockade and interferon-α on clonality of T-cell repertoire in the tumor microenvironment and peripheral blood of metastatic melanoma patients

Patients with metastatic melanoma were treated with tremelimumab and interferon-α (IFN) in a previously reported clinical trial [NCT00610857]. Responses were assessed by RECIST criteria as complete (CR) or partial (PR), stable disease (SD) or progressive disease (PD). In this study, T-cell receptor (TCR) beta-chain repertoire was immunosequenced in peripheral blood mononuclear cells (PBMC) specimens (N = 33) and tumor samples (N = 18) utilizing the immunoSEQ® Assay to determine repertoire clonality and T cell fractions at pre-treatment (tumor and PBMC), one month (PBMC) and 3 months (PBMC) time points and evaluate its association with clinical outcomes. In the pretreatment tumor microenvironment (TME), T cell clonality was significantly (p = .035) different and greater in patients who achieved disease control (CR, PR, SD) versus those with non-disease control (PD) as best response to treatment. Further, there was significantly (p = .001) increased TCR fraction in tissue of responders (CR, PR) versus non-responders (PD, SD). In examining T cell clonality in the circulation (PBMC), no significant associations were found in the pretreatment samples. However, early on-treatment (4 weeks) there was a significant decrease in T cell clonality that was associated with improved overall survival (p = .01) and progression-free survival (p = .04). In addition, analysis of temporal changes in tumor-infiltrating lymphocytes (TIL) and peripheral TCR repertoire revealed that responders had significantly higher clonal expansion of TIL in the circulation at 4 weeks than non-responders (p = .036). Our study provided interesting mechanistic data related to CTLA-4 Blockade and IFN and potential biomarkers of immunotherapeutic benefit.

Enhancing Dendritic Cell Therapy in Solid Tumors with Immunomodulating Conventional Treatment

Dendritic cells (DCs) are the most potent antigen-presenting cells and are the key initiator of tumor-specific immune responses. These characteristics are exploited by DC therapy, where DCs are ex vivo loaded with tumor-associated antigens (TAAs) and used to induce tumor-specific immune responses. Unfortunately, clinical responses remain limited to a proportion of the patients. Tumor characteristics and the immunosuppressive tumor microenvironment (TME) of the tumor are likely hampering efficacy of DC therapy. Therefore, reducing the immunosuppressive TME by combining DC therapy with other treatments could be a promising strategy. Initially, conventional cancer therapies, such as chemotherapy and radiotherapy, were thought to specifically target cancerous cells. Recent insights indicate that these therapies additionally augment tumor immunity by targeting immunosuppressive cell subsets in the TME, inducing immunogenic cell death (ICD), or blocking inhibitory molecules. Therefore, combining DC therapy with registered therapies such as chemotherapy, radiotherapy, or checkpoint inhibitors could be a promising treatment strategy to improve the efficacy of DC therapy. In this review, we evaluate various clinical applicable combination strategies to improve the efficacy of DC therapy.

Therapeutic Cancer Vaccine and Combinations With Antiangiogenic Therapies and Immune Checkpoint Blockade

Considering the high importance of immune surveillance and immune escape in the evolution of cancer, the development of immunotherapeutic strategies has become a major field of research in recent decades. The considerable therapeutic breakthrough observed when targeting inhibitory immune checkpoint molecules has highlighted the need to find approaches enabling the induction and proper activation of an immune response against cancer. In this context, therapeutic vaccination, which can induce a specific immune response against tumor antigens, is an important approach to consider. However, this strategy has its advantages and limits. Considering its low clinical efficacy, approaches combining therapeutic cancer vaccine strategies with other immunotherapies or targeted therapies have been emphasized. This review will list different cancer vaccines, with an emphasis on their targets. We highlight the results and limits of vaccine strategies and then describe strategies that combine therapeutic vaccines and antiangiogenic therapies or immune checkpoint blockade. Antiangiogenic therapies and immune checkpoint blockade are of proven clinical efficacy for some indications, but are limited by toxicity and the development of resistance. Their combination with therapeutic vaccines could be a way to improve therapeutic outcome by specifically stimulating the immune system and considering a global approach to tumor microenvironment remodeling.

Human Dendritic Cells: Their Heterogeneity and Clinical Application Potential in Cancer Immunotherapy

Dendritic cells (DC) are professional antigen presenting cells, uniquely able to induce naïve T cell activation and effector differentiation. They are, likewise, involved in the induction and maintenance of immune tolerance in homeostatic conditions. Their phenotypic and functional heterogeneity points to their great plasticity and ability to modulate, according to their microenvironment, the acquired immune response and, at the same time, makes their precise classification complex and frequently subject to reviews and improvement. This review will present general aspects of the DC physiology and classification and will address their potential and actual uses in the management of human disease, more specifically cancer, as therapeutic and monitoring tools. New combination treatments with the participation of DC will be also discussed.

A CD40 Agonist and PD-1 Antagonist Antibody Reprogram the Microenvironment of Nonimmunogenic Tumors to Allow T-cell-Mediated Anticancer Activity

In cancers with tumor-infiltrating lymphocytes (TILs), monoclonal antibodies (mAbs) that block immune checkpoints such as CTLA-4 and PD-1/PD-L1 promote antitumor T-cell immunity. Unfortunately, most cancers fail to respond to single-agent immunotherapies. T regulatory cells, myeloid derived suppressor cells (MDSCs), and extensive stromal networks within the tumor microenvironment (TME) dampen antitumor immune responses by preventing T-cell infiltration and/or activation. Few studies have explored combinations of immune-checkpoint antibodies that target multiple suppressive cell populations within the TME, and fewer have studied the combinations of both agonist and antagonist mAbs on changes within the TME. Here, we test the hypothesis that combining a T-cell-inducing vaccine with both a PD-1 antagonist and CD40 agonist mAbs (triple therapy) will induce T-cell priming and TIL activation in mouse models of nonimmunogenic solid malignancies. In an orthotopic breast cancer model and both subcutaneous and metastatic pancreatic cancer mouse models, only triple therapy was able to eradicate most tumors. The survival benefit was accompanied by significant tumor infiltration of IFNγ-, Granzyme B-, and TNFα-secreting effector T cells. Further characterization of immune populations was carried out by high-dimensional flow-cytometric clustering analysis and visualized by t-distributed stochastic neighbor embedding (t-SNE). Triple therapy also resulted in increased infiltration of dendritic cells, maturation of antigen-presenting cells, and a significant decrease in granulocytic MDSCs. These studies reveal that combination CD40 agonist and PD-1 antagonist mAbs reprogram immune resistant tumors in favor of antitumor immunity.

Combination Strategies to Optimize Efficacy of Dendritic Cell-Based Immunotherapy

Dendritic cells (DCs) are antigen-presenting cells (APCs) that are essential for the activation of immune responses. In various malignancies, these immunostimulatory properties are exploited by DC-therapy, aiming at the induction of effective anti-tumor immunity by vaccination with ex vivo antigen-loaded DCs. Depending on the type of DC-therapy used, long-term clinical efficacy upon DC-therapy remains restricted to a proportion of patients, likely due to lack of immunogenicity of tumor cells, presence of a stromal compartment, and the suppressive tumor microenvironment (TME), thereby leading to the development of resistance. In order to circumvent tumor-induced suppressive mechanisms and unleash the full potential of DC-therapy, considerable efforts have been made to combine DC-therapy with chemotherapy, radiotherapy or with checkpoint inhibitors. These combination strategies could enhance tumor immunogenicity, stimulate endogenous DCs following immunogenic cell death, improve infiltration of cytotoxic T lymphocytes (CTLs) or specifically deplete immunosuppressive cells in the TME, such as regulatory T-cells and myeloid-derived suppressor cells. In this review, different strategies of combining DC-therapy with immunomodulatory treatments will be discussed. These strategies and insights will improve and guide DC-based combination immunotherapies with the aim of further improving patient prognosis and care.

Re-induction using whole cell melanoma vaccine genetically modified to melanoma stem cells-like beyond recurrence extends long term survival of high risk resected patients - updated results

BACKGROUND

AGI-101H is an allogeneic gene modified whole cell therapeutic melanoma vaccine, evaluated in over 400 melanoma patients in the adjuvant and therapeutic settings. We present updated long-term survival results from two single-arm, phase II adjuvant trials (Trial 3 and Trial 5) with the focus on treatment beyond recurrence of the disease.

METHODS

Patients with resected high-risk melanoma (stage IIIB-IV) were enrolled to Trial 3 (n = 99) and Trial 5 (n = 97). The primary endpoint was disease-free survival (DFS), and the secondary was overall survival (OS). In the induction phase, the vaccine was administered every 2 weeks (eight times), followed by the maintenance phase every month until progression. At progression, maintenance was continued or re-induction was applied with or without surgery.

RESULTS

In Trial 3, the 10-year DFS was equal to 33.0% overall and to 52.4, 25.0, and 8.7% for stage IIIB, IIIC, and stage IV patients, respectively. In Trial 5, the overall 10-year DFS was equal to 24.2%, and to 37.5, 18.0, and 17.6% for stage IIIB, IIIC, and stage IV patients, respectively. In Trial 3, the 10-year OS was equal to 42.3% overall, and to 59.5, 37.5, and 17.4% for stage IIIB, IIIC, and stage IV patients, respectively. In Trial 5, the 10-year OS was equal to 34.3% overall and to 46.9, 28.0, and 29.4% for stage IIIB, IIIC, and stage IV patients, respectively. Among the 65 patients of Trial 3 who developed progression, 43 received re-induction with (n = 22) or without (n = 21) surgery. Two patients received surgery without re-induction. All the 22 progressing patients, who did not receive re-induction, died. Among the 75 patients of Trial 5 who experienced progression, 39 received re-induction with (n = 21) or without (n = 18) surgery. Among the 36 progressing patients who did not receive the re-induction, 35 died. Surgery and re-induction reduced (independently) the increase of mortality after progression in both trials, with the effect of re-induction reaching statistical significance in Trial 5.

CONCLUSIONS

Vaccination beyond recurrence of the disease with additional re-induction combined with surgery or alone increased long term survival of melanoma patients. However, further studies on larger patient cohorts are required.

TRIAL REGISTRATION

Central Evidence of Clinical Trials (EudraCT Number 2008-003373-40 ).

Does the Immunocompetent Status of Cancer Patients Have an Impact on Therapeutic DC Vaccination Strategies?

Although different types of therapeutic vaccines against established cancerous lesions in various indications have been developed since the 1990s, their clinical benefit is still very limited. This observed lack of effectiveness in cancer eradication may be partially due to the often deficient immunocompetent status of cancer patients, which may facilitate tumor development by different mechanisms, including immune evasion. The most frequently used cellular vehicle in clinical trials are dendritic cells (DCs), thanks to their crucial role in initiating and directing immune responses. Viable vaccination options using DCs are available, with a positive toxicity profile. For these reasons, despite their limited therapeutic outcomes, DC vaccination is currently considered an additional immunotherapeutic option that still needs to be further explored. In this review, we propose potential actions aimed at improving DC vaccine efficacy by counteracting the detrimental mechanisms recognized to date and implicated in establishing a poor immunocompetent status in cancer patients.

PEGylated tumor cell membrane vesicles as a new vaccine platform for cancer immunotherapy

Despite the promise and advantages of autologous cancer cell vaccination, it remains challenging to induce potent anti-tumor immune responses with traditional immunization strategies with whole tumor cell lysate. In this study, we sought to develop a simple and effective approach for therapeutic vaccination with autologous whole tumor cell lysate. Endogenous cell membranes harvested from cancer cells were formed into PEGylated nano-vesicles (PEG-NPs). PEG-NPs exhibited good serum stability in vitro and draining efficiency to local lymph nodes upon subcutaneous administration in vivo. Vaccination with PEG-NPs synthesized from murine melanoma cells elicited 3.7-fold greater antigen-specific cytotoxic CD8+ T lymphocyte responses, compared with standard vaccination with freeze-thawed lysate in tumor-bearing mice. Importantly, in combination with anti-programmed death-1 (αPD-1) IgG immunotherapy, PEG-NP vaccination induced 4.2-fold higher frequency of antigen-specific T cell responses (P < 0.0001) and mediated complete tumor regression in 63% of tumor-bearing animals (P < 0.01), compared with FT lysate + αPD-1 treatment that exhibited only 13% response rate. In addition, PEG-NPs + αPD-1 IgG combination immunotherapy protected all survivors against a subsequent tumor cell re-challenge. These results demonstrate a general strategy for eliciting anti-tumor immunity using endogenous cancer cell membranes formulated into stable vaccine nanoparticles.

Empowering dendritic cell cancer vaccination: the role of combinatorial strategies

Dendritic cells (DCs) are bone marrow-derived immune cells that play a crucial role in inducing the adaptive immunity and supporting the innate immune response independently from T cells. In the last decade, DCs have become a hopeful instrument for cancer vaccines that aims at re-educating the immune system, leading to a potent anti-cancer immune response able to overcome the immunosuppressive tumor microenvironment (TME). Although several studies have indicated that DC-based vaccines are feasible and safe, the clinical advantages of DC vaccination as monotherapy for most of the neoplasms remain a distant target. Recently, many reports and clinical trials have widely used innovative combinatorial therapeutic strategies to normalize the immune function in the TME and synergistically enhance DC function. This review will describe the most relevant and updated evidence of the anti-cancer combinatorial approaches to boost the clinical potency of DC-based vaccines.

GM-CSF Culture Revisited: Preparation of Bulk Populations of Highly Pure Dendritic Cells from Mouse Bone Marrow

Dendritic cells (DC) loaded with specific peptides are strongly immunogenic for T cells and can be used for cancer immunotherapy. For immunogenic tumors such as melanoma, injection of autologous DC loaded with tumor cell extracts or peptides can induce tumor regression but in only a small proportion of patients. Nevertheless, recent studies on the efficacy of checkpoint blockade for boosting antitumor immunity plus advances in defining tumor neoantigens are stimulating renewed interest in DC immunotherapy. Despite intensive investigation, however, preparation of bulk populations of mature DC has proved difficult, and most preparations contain a significant proportion of potentially tolerogenic immature DC. In this study, we have modified the well-established GM-CSF culture system to prepare substantial quantities of highly pure (>95%) mature DC from mouse bone marrow cells and defined their progenitors. We show that obtaining high yields and purity of DC are heavily dependent on cell density in the cultures and the tempo of addition of growth and maturation stimuli. When loaded with specific peptide, the DC are strongly immunogenic for CD4 and CD8 T cells in vivo and elicit effective antitumor immunity.

Dendritic Cell Cancer Therapy: Vaccinating the Right Patient at the Right Time

Immune checkpoint inhibitors propelled the field of oncology with clinical responses in many different tumor types. Superior overall survival over chemotherapy has been reported in various metastatic cancers. Furthermore, prolonged disease-free and overall survival have been reported in the adjuvant treatment of stage III melanoma. Unfortunately, a substantial portion of patients do not obtain a durable response. Therefore, additional strategies for the treatment of cancer are still warranted. One of the numerous options is dendritic cell vaccination, which employs the central role of dendritic cells in activating the innate and adaptive immune system. Over the years, dendritic cell vaccination was shown to be able to induce an immunologic response, to increase the number of tumor infiltrating lymphocytes and to provide overall survival benefit for at least a selection of patients in phase II studies. However, with the success of immune checkpoint inhibition in several malignancies and considering the plethora of other treatment modalities being developed, it is of utmost importance to delineate the position of dendritic cell therapy in the treatment landscape of cancer. In this review, we address some key questions regarding the integration of dendritic cell vaccination in future cancer treatment paradigms.

Targeting myeloid-derived suppressor cells using all-trans retinoic acid in melanoma patients treated with Ipilimumab

BACKGROUND

Immune checkpoint inhibitors have improved overall survival rates for many cancers, yet the majority of patients do not respond to treatment and succumb to disease progression. One tumor-related mechanism limiting the efficacy of immunotherapies in melanoma is the recruitment and expansion of myeloid-derived suppressor cells (MDSCs). Therefore, targeting MDSCs in combination with immunotherapies is an attractive strategy to improve response rates and effectiveness.

METHODS

We tested this strategy by designing a randomized phase II clinical trial treating advanced melanoma patients with either Ipilimumab monotherapy or Ipilimumab plus all-trans retinoic acid (ATRA). Clinicaltrails.gov identifier (NCT02403778). The frequency of circulating MDSCs and the activation of CD8(+) T cells was measured by flow cytometry. Expression of immunosuppressive genes was measured with quantitative real time-PCR. T cell suppressive functions were measured by mixed lymphocyte reaction.

RESULTS

Here we show that in vitro treatment with ATRA decreases immunosuppressive function of MDSCs in mixed lymphocyte reactions. Additionally, ATRA reduces the expression of immunosuppressive genes including PD-L1, IL-10, and indoleamine 2,3‑dioxygenase by MDSCs. Furthermore, the addition of ATRA to standard of care Ipilimumab therapy appears safe, as ATRA did not increase the frequency of grade 3 or 4 adverse events. Finally, ATRA significantly decreased the frequency of circulating MDSCs compared to Ipilimumab treatment alone in advanced-stage melanoma patients.

CONCLUSIONS

These results illustrate the importance of MDSCs in immunotherapy resistance and provide evidence that targeting MDSCs in cancer patients may augment immunotherapeutic approaches.

Mechanisms regulating T-cell infiltration and activity in solid tumors

T-lymphocytes play a critical role in cancer immunity as evidenced by their presence in resected tumor samples derived from long-surviving patients, and impressive clinical responses to various immunotherapies that reinvigorate them. Indeed, tumors can upregulate a wide array of defense mechanisms, both direct and indirect, to suppress the ability of Tcells to reach the tumor bed and mount curative responses upon infiltration. In addition, patient and tumor genetics, previous antigenic experience, and the microbiome, are all important factors in shaping the T-cell repertoire and sensitivity to immunotherapy. Here, we review the mechanisms that regulate T-cell homing, infiltration, and activity within the solid tumor bed. Finally, we summarize different immunotherapies and combinatorial treatment strategies that enable the immune system to overcome barriers for enhanced tumor control and improved patient outcome.