Polarized dendritic cells as cancer vaccines: directing effector-type T cells to tumors

Revolutionizing cancer care strategies: immunotherapy, gene therapy, and molecular targeted therapy

Despite the availability of technological advances in traditional anti-cancer therapies, there is a need for more precise and targeted cancer treatment strategies. The wide-ranging shortfalls of conventional anticancer therapies such as systematic toxicity, compromised life quality, and limited to severe side effects are major areas of concern of conventional cancer treatment approaches. Owing to the expansion of knowledge and technological advancements in the field of cancer biology, more innovative and safe anti-cancerous approaches such as immune therapy, gene therapy and targeted therapy are rapidly evolving with the aim to address the limitations of conventional therapies. The concept of immunotherapy began with the capability of coley toxins to stimulate toll-like receptors of immune cells to provoke an immune response against cancers. With an in-depth understating of the molecular mechanisms of carcinogenesis and their relationship to disease prognosis, molecular targeted therapy approaches, that inhibit or stimulate specific cancer-promoting or cancer-inhibitory molecules respectively, have offered promising outcomes. In this review, we evaluate the achievement and challenges of these technically advanced therapies with the aim of presenting the overall progress and perspective of each approach.

Dendritic cell vaccines improve the glioma microenvironment: Influence, challenges, and future directions

INTRODUCTION

Gliomas, especially the glioblastomas, are one of the most aggressive intracranial tumors with poor prognosis. This might be explained by the heterogeneity of tumor cells and the inhibitory immunological microenvironment. Dendritic cells (DCs), as the most potent in vivo functional antigen-presenting cells, link innate immunity with adaptive immunity. However, their function is suppressed in gliomas. Therefore, overcoming the dysfunction of DCs in the TME might be critical to treat gliomas.

METHOD

In this paper we proposed the specificity of the glioma microenvironment, analyzed the pathways leading to the dysfunction of DCs in tumor microenvironment of patients with glioma, summarized influence of DC-based immunotherapy on the tumor microenvironment and proposed new development directions and possible challenges of DC vaccines.

RESULT

DC vaccines can improve the immunosuppressive microenvironment of glioma patients. It will bring good treatment prospects to patients. We also proposed new development directions and possible challenges of DC vaccines, thus providing an integrated understanding of efficacy on DC vaccines for glioma treatment.

Antitumor activity of recombinant oncolytic vaccinia virus with human IL2

The tumor microenvironment is highly immunosuppressive. The genetically modified oncolytic vaccinia virus (OVV) is a promising vector for cancer immunotherapy. The aim of the present study was to assess the antitumor effects of human interleukin-2 (hIL2)-armed OVV in vitro. The hIL2 gene was inserted into a thymidine kinase and the viral growth factor double deleted oncolytic VV (VVDD) to generate recombinant hIL2-armed OVV (rVVDD-hIL2). Viral replication capacity in A549 cells was quantified by plaque titration on CV-1 cells. Production of hIL2 in cancer cells infected by rVVDD-hIL2 was measured by enzyme-linked immunosorbent assay. Finally, 3-(4,5-dimethylthiazol-2-yl)-5-(3-arboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay was performed to assess the antitumor effects of rVVDD-hIL2. The results showed that rVVDD-hIL2 viral particles expressed increasing levels of hIL2 in human and murine cancer cell lines with growing multiplicities of infection (MOIs). The insertion of the hIL2 gene did not impair the replication capacity of VV, and the rVVDD-hIL2 virus killed cancer cells efficaciously. The lytic effects of the recombinant oncolytic virus on tumor cells increased with the growing MOIs. In conclusion, these findings suggest that hIL2-armed VVDD effectively infects and lyses tumor cells, with high expression of hIL2.

Generation of high cross-presentation ability human dendritic cells by combination of interleukin 4, interferon β and GM-CSF

Dendritic cell (DC)-based immunotherapies have been utilized for the treatment of numerous diseases. However, the conventional generation strategies of DCs in vitro require 7 days and these DCs showed an unsatisfactory function, which prompted us to explore new approaches. We found that in vitro culture of human CD14⁺ cells, in the medium containing granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-4, as well as interferon β (IFN-β) for 48 h, followed by the maturation stimuli of IL-1β and poly I:C for another 24 h can be differentiated into high cross-presentation ability DCs (G4B-DCs). These DCs express high levels of CD11c, CD86, and HLA-DR, producing a high level of tumor necrosis factor α (TNF-α). Of note, compared with the conventional DCs, G4B-DCs showed a higher ability to promote allogeneic naïve CD4⁺ T cell and CD8⁺ T cell proliferation and interferon (IFN)-γ production. These DCs also have the remarkable ability to induce Flu-M1-specific CD8⁺ T cells. In addition, we found that these G4B-DCs express partially the cDC1 phenotype. These data indicate that G4B-DC is unique and may provide a relatively rapid alternative method for potential clinical use.

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.

Fecal microbiota composition associates with the capacity of human peripheral blood monocytes to differentiate into immunogenic dendritic cells in vitro

Although promising for active immunization in cancer patients, dendritic cells (DCs) vaccines generated in vitro display high inter-individual variability in their immunogenicity, which mostly limits their therapeutic efficacy. Gut microbiota composition is a key emerging factor affecting individuals' immune responses, but it is unknown how it affects the variability of donors' precursor cells to differentiate into immunogenic DCs in vitro. By analyzing gut microbiota composition in 14 healthy donors, along with the phenotype and cytokines production by monocyte-derived DCs, we found significant correlations between immunogenic properties of DC and microbiota composition. Namely, donors who had higher α-diversity of gut microbiota and higher abundance of short-chain fatty acid (SCFAs) and SCFA-producing bacteria in feces, displayed lower expression of CD1a on immature (im)DC and higher expression of ILT-3, costimulatory molecules (CD86, CD40) proinflammatory cytokines (TNF-α, IL-6, IL-8) and IL-12p70/IL-10 ratio, all of which correlated with their lower maturation potential and immunogenicity upon stimulation with LPS/IFNγ, a well-known Th1 polarizing cocktail. In contrast, imDCs generated from donors with lower α-diversity and higher abundance of Bifidobacterium and Collinsella in feces displayed higher CD1a expression and higher potential to up-regulate CD86 and CD40, increase TNF-α, IL-6, IL-8 production, and IL-12p70/IL-10 ratio upon stimulation. These results emphasize the important role of gut microbiota on the capacity of donor precursor cells to differentiate into immunogenic DCs suitable for cancer therapy, which could be harnessed for improving the actual and future DC-based cancer therapies.

Personalized Neoantigen-Pulsed DC Vaccines: Advances in Clinical Applications

In the past few decades, great progress has been made in the clinical application of dendritic cell (DC) vaccines loaded with personalized neoantigens. Personalized neoantigens are antigens arising from somatic mutations in cancers, with specificity to each patient. DC vaccines work based on the fundamental characteristics of DCs, which are professional antigen-presenting cells (APCs), responsible for the uptake, processing, and presentation of antigens to T cells to activate immune responses. Neoantigens can exert their antitumor effects only after they are taken up by APCs and presented to T cells. In recent years, neoantigen-based personalized tumor therapeutic vaccines have proven to be safe, immunogenic and feasible treatment strategies in patients with melanoma and glioblastoma that provide new hope in the treatment of cancer patients and a new approach to cure cancer. In addition, according to ClinicalTrials.gov, hundreds of registered DC vaccine trials are either completed or ongoing worldwide, of which 9 are in early phase I, 191 in phase I, 166 in phase II and 8 in phase III. Hundreds of clinical studies on therapeutic tumor vaccines globally have proven that DC vaccines are stable, reliable and very safe. However, in this process, many other factors still limit the effectiveness of the vaccine. This review will focus on the current research progress on personalized neoantigen-pulsed DC vaccines, their limitations and future research directions of DC vaccines loaded with neoantigens. This review aims to provide a better understanding of DCs biology and manipulation of activated DCs for DCs researchers to produce the next generation of highly efficient cancer vaccines for patients.

Therapeutic tumor vaccines — a rising star to benefit cancer patients

Malignant tumors are still a worldwide threat to human health. Tumor treatment strategies are constantly evolving, and the advent of tumor immunotherapy has brought up hope to many types of tumors, especially for those that are refractory to conventional therapies including surgery, radiotherapy, and chemotherapy. Tumor vaccines can initiate or amplify an anti-tumor immune response in tumor patients through active immunization, and therefore occupy an important position in tumor immunotherapy. The main types of tumor vaccines include tumor cell vaccines, dendritic cell vaccines, polypeptide vaccines and nucleic acid vaccines. Due to factors such as poor antigen selection and suppressive tumor microenvironment, earliest tumor vaccines on clinical trials failed to achieve satisfactory clinical effects. However, with the development of second-generation genome sequencing technologies and bioinformatics tools, it is possible to predict neoantigens generated by tumor-specific mutations and therefore prepare personalized vaccines. This article summarizes the global efforts in developing tumor vaccines and highlights several representative tumor vaccines in each category.

Monocytes complexed to platelets differentiate into functionally deficient dendritic cells

In addition to their role in hemostasis, platelets store numerous immunoregulatory molecules such as CD40L, TGFβ, β2-microglobulin, and IL-1β and release them upon activation. Previous studies indicate that activated platelets form transient complexes with monocytes, especially in HIV infected individuals and induce a proinflammatory monocyte phenotype. Because monocytes can act as precursors of dendritic cells (DCs) during infection/inflammation as well as for generation of DC-based vaccine therapies, we evaluated the impact of activated platelets on monocyte differentiation into DCs. We observed that in vitro cultured DCs derived from platelet-monocyte complexes (PMCs) exhibit reduced levels of molecules critical to DC function (CD206, dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin, CD80, CD86, CCR7) and reduced antigen uptake capacity. DCs derived from PMCs also showed reduced ability to activate naïve CD4+ and CD8+ T cells, and secrete IL-12p70 in response to CD40L stimulation, resulting in decreased ability to promote type-1 immune responses to HIV antigens. Our results indicate that formation of complexes with activated platelets can suppress the development of functional DCs from such monocytes. Disruption of PMCs in vivo via antiplatelet drugs such as Clopidogrel/Prasugrel or the application of platelet-free monocytes for DCs generation in vitro, may be used to enhance immunization and augment the immune control of HIV.

Personalized cancer vaccine strategy elicits polyfunctional T cells and demonstrates clinical benefits in ovarian cancer

T cells are important for controlling ovarian cancer (OC). We previously demonstrated that combinatorial use of a personalized whole-tumor lysate-pulsed dendritic cell vaccine (OCDC), bevacizumab (Bev), and cyclophosphamide (Cy) elicited neoantigen-specific T cells and prolonged OC survival. Here, we hypothesize that adding acetylsalicylic acid (ASA) and low-dose interleukin (IL)-2 would increase the vaccine efficacy in a recurrent advanced OC phase I trial (NCT01132014). By adding ASA and low-dose IL-2 to the OCDC-Bev-Cy combinatorial regimen, we elicited vaccine-specific T-cell responses that positively correlated with patients' prolonged time-to-progression and overall survival. In the ID8 ovarian model, animals receiving the same regimen showed prolonged survival, increased tumor-infiltrating perforin-producing T cells, increased neoantigen-specific CD8⁺ T cells, and reduced endothelial Fas ligand expression and tumor-infiltrating T-regulatory cells. This combinatorial strategy was efficacious and also highlighted the predictive value of the ID8 model for future ovarian trial development.

Phase II Trial of Adjuvant Dendritic Cell Vaccine in Combination with Celecoxib, Interferon-α, and Rintatolimod in Patients Undergoing Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy for Peritoneal Metastases

BACKGROUND

Peritoneal metastases portend poor prognosis in the setting of standard chemotherapy. Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) improves outcomes, but relapse is common. We report a phase II trial evaluating the safety and efficacy of adjuvant αDC1 vaccination with chemokine modulation (CKM) after CRS/HIPEC.

METHODS

Patients undergoing CRS/HIPEC for appendiceal cancer, colorectal cancer, or peritoneal mesothelioma were enrolled. In addition to standard adjuvant chemotherapy, patients received intranodal and intradermal injections of autologous tumor-loaded αDC1 vaccine. After each vaccine booster, patients received CKM over 4 days, consisting of celecoxib, interferon (IFN)-α, and rintatolimod.

RESULTS

Forty-six patients underwent CRS/HIPEC followed by αDC1 treatment, including 24 appendiceal primaries, 20 colorectal, and 2 mesotheliomas. DC maturation was successful, with 97% expressing HLA-DR and CD86. Tumor cell recovery from peritoneal tumors was challenging, resulting in only 17% of patients receiving the target dose of αDC1. The αDC1 and CKM regimen was well tolerated. CKM successfully modulated serum inflammatory cytokine and chemokine levels. Median progression-free survival (PFS) for appendiceal primaries was 50.4, 34.2, and 8.9 months for grade 1, 2, and 3 tumors, respectively, while median PFS for colorectal cancer was 20.5 and 8.9 months for moderately and poorly differentiated tumors, respectively.

CONCLUSIONS

Adjuvant autologous tumor antigen-loaded αDC1 vaccine and CKM is well tolerated. The mucinous nature of peritoneal metastases limits the feasibility of obtaining adequate autologous tumor cells. The improvement in median PFS did not meet our predefined thresholds, leading us to conclude that αDC1 vaccination is not appropriate for patients undergoing CRS/HIPEC for peritoneal metastases.

Usefulness of IL-21, IL-7, and IL-15 conditioned media for expansion of antigen-specific CD8+ T cells from healthy donor-PBMCs suitable for immunotherapy

Clonal anergy and depletion of antigen-specific CD8+ T cells are characteristics of immunosuppressed patients such as cancer and post-transplant patients. This has promoted translational research on the adoptive transfer of T cells to restore the antigen-specific cellular immunity in these patients. In the present work, we compared the capability of PBMCs and two types of mature monocyte-derived DCs (moDCs) to prime and to expand ex-vivo antigen-specific CD8+ T cells using culture conditioned media supplemented with IL-7, IL-15, and IL-21. The data obtained suggest that protocols involving moDCs are as efficient as PBMCs-based cultures in expanding antigen-specific CD8+ T cell to ELA and CMV model epitopes. These three gamma common chain cytokines promote the expansion of naïve-like and central memory CD8+ T cells in PBMCs-based cultures and the expansion of effector memory T cells when moDCs were used. Our results provide new insights into the use of media supplemented with IL-7, IL-15, and IL-21 for the in-vitro expansion of early-differentiated antigen-specific CD8+ T cells for immunotherapy purposes.

Advances in Anti-Cancer Immunotherapy: Car-T Cell, Checkpoint Inhibitors, Dendritic Cell Vaccines, and Oncolytic Viruses, and Emerging Cellular and Molecular Targets

Unlike traditional cancer therapies, such as surgery, radiation and chemotherapy that are typically non-specific, cancer immunotherapy harnesses the high specificity of a patient’s own immune system to selectively kill cancer cells. The immune system is the body’s main cancer surveillance system, but cancers may evade destruction thanks to various immune-suppressing mechanisms. We therefore need to deploy various immunotherapy-based strategies to help bolster the anti-tumour immune responses. These include engineering T cells to express chimeric antigen receptors (CARs) to specifically recognise tumour neoantigens, inactivating immune checkpoints, oncolytic viruses and dendritic cell (DC) vaccines, which have all shown clinical benefit in certain cancers. However, treatment efficacy remains poor due to drug-induced adverse events and immunosuppressive tendencies of the tumour microenvironment. Recent preclinical studies have unveiled novel therapies such as anti-cathepsin antibodies, galectin-1 blockade and anti-OX40 agonistic antibodies, which may be utilised as adjuvant therapies to modulate the tumour microenvironment and permit more ferocious anti-tumour immune response.

Therapeutic Cancer Vaccination with Ex Vivo RNA-Transfected Dendritic Cells-An Update

Over the last two decades, dendritic cell (DC) vaccination has been studied extensively as active immunotherapy in cancer treatment and has been proven safe in all clinical trials both with respect to short and long-term side effects. For antigen-loading of dendritic cells (DCs) one method is to introduce mRNA coding for the desired antigens. To target the whole antigenic repertoire of a tumor, even the total tumor mRNA of a macrodissected biopsy sample can be used. To date, reports have been published on a total of 781 patients suffering from different tumor entities and HIV-infection, who have been treated with DCs loaded with mRNA. The majority of those were melanoma patients, followed by HIV-infected patients, but leukemias, brain tumors, prostate cancer, renal cell carcinomas, pancreatic cancers and several others have also been treated. Next to antigen-loading, mRNA-electroporation allows a purposeful manipulation of the DCs’ phenotype and function to enhance their immunogenicity. In this review, we intend to give a comprehensive summary of what has been published regarding clinical testing of ex vivo generated mRNA-transfected DCs, with respect to safety and risk/benefit evaluations, choice of tumor antigens and RNA-source, and the design of better DCs for vaccination by transfection of mRNA-encoded functional proteins.

Immune Escape after Hematopoietic Stem Cell Transplantation (HSCT): From Mechanisms to Novel Therapies

Acute myeloid leukemia (AML) is the most common type of acute leukemia in adults. Recent advances in understanding its molecular basis have opened the way to new therapeutic strategies, including targeted therapies. However, despite an improvement in prognosis it has been documented in recent years (especially in younger patients) that allogenic hematopoietic stem cell transplantation (allo-HSCT) remains the only curative treatment in AML and the first therapeutic option for high-risk patients. After allo-HSCT, relapse is still a major complication, and is observed in about 50% of patients. Current evidence suggests that relapse is not due to clonal evolution, but instead to the ability of the AML cell population to escape immune control by a variety of mechanisms including the altered expression of HLA-molecules, production of anti-inflammatory cytokines, relevant metabolic changes and expression of immune checkpoint (ICP) inhibitors capable of “switching-off” the immune response against leukemic cells. Here, we review the main mechanisms of immune escape and identify potential strategies to overcome these mechanisms.

The clinical application of cancer immunotherapy based on naturally circulating dendritic cells

Dendritic cells (DCs) can initiate and direct adaptive immune responses. This ability is exploitable in DC vaccination strategies, in which DCs are educated ex vivo to present tumor antigens and are administered into the patient with the aim to induce a tumor-specific immune response. DC vaccination remains a promising approach with the potential to further improve cancer immunotherapy with little or no evidence of treatment-limiting toxicity. However, evidence for objective clinical antitumor activity of DC vaccination is currently limited, hampering the clinical implementation. One possible explanation for this is that the most commonly used monocyte-derived DCs may not be the best source for DC-based immunotherapy. The novel approach to use naturally circulating DCs may be an attractive alternative. In contrast to monocyte-derived DCs, naturally circulating DCs are relatively scarce but do not require extensive culture periods. Thereby, their functional capabilities are preserved, the reproducibility of clinical applications is increased, and the cells are not dysfunctional before injection. In human blood, at least three DC subsets can be distinguished, plasmacytoid DCs, CD141⁺ and CD1c⁺ myeloid/conventional DCs, each with distinct functional characteristics. In completed clinical trials, either CD1c⁺ myeloid DCs or plasmacytoid DCs were administered and showed encouraging immunological and clinical outcomes. Currently, also the combination of CD1c⁺ myeloid and plasmacytoid DCs as well as the intratumoral use of CD1c⁺ myeloid DCs is under investigation in the clinic. Isolation and culture strategies for CD141⁺ myeloid DCs are being developed. Here, we summarize and discuss recent clinical developments and future prospects of natural DC-based immunotherapy.

The clinical application of cancer immunotherapy based on naturally circulating dendritic cells

Dendritic cells (DCs) can initiate and direct adaptive immune responses. This ability is exploitable in DC vaccination strategies, in which DCs are educated ex vivo to present tumor antigens and are administered into the patient with the aim to induce a tumor-specific immune response. DC vaccination remains a promising approach with the potential to further improve cancer immunotherapy with little or no evidence of treatment-limiting toxicity. However, evidence for objective clinical antitumor activity of DC vaccination is currently limited, hampering the clinical implementation. One possible explanation for this is that the most commonly used monocyte-derived DCs may not be the best source for DC-based immunotherapy. The novel approach to use naturally circulating DCs may be an attractive alternative. In contrast to monocyte-derived DCs, naturally circulating DCs are relatively scarce but do not require extensive culture periods. Thereby, their functional capabilities are preserved, the reproducibility of clinical applications is increased, and the cells are not dysfunctional before injection. In human blood, at least three DC subsets can be distinguished, plasmacytoid DCs, CD141+ and CD1c+ myeloid/conventional DCs, each with distinct functional characteristics. In completed clinical trials, either CD1c+ myeloid DCs or plasmacytoid DCs were administered and showed encouraging immunological and clinical outcomes. Currently, also the combination of CD1c+ myeloid and plasmacytoid DCs as well as the intratumoral use of CD1c+ myeloid DCs is under investigation in the clinic. Isolation and culture strategies for CD141+ myeloid DCs are being developed. Here, we summarize and discuss recent clinical developments and future prospects of natural DC-based immunotherapy.

An accelerated, clinical-grade protocol to generate high yields of type 1-polarizing messenger RNA-loaded dendritic cells for cancer vaccination

BACKGROUND

Many efforts have been devoted to improve the performance of dendritic cell (DC)-based cancer vaccines. Ideally, a DC vaccine should induce robust type 1-polarized T-cell responses and efficiently expand antigen (Ag)-specific cytotoxic T-cells, while being applicable regardless of patient human leukocyte antigen (HLA) type. Production time should be short, while maximally being good manufacturing practice (GMP)-compliant. We developed a method that caters to all of these demands and demonstrated the superiority of the resulting product compared with DCs generated using a well-established "classical" protocol.

METHODS

Immunomagnetically purified monocytes were cultured in a closed system for 3 days in GMP-compliant serum-free medium and cytokines, and matured for 24 h using monophosphoryl lipid A (MPLA)+ interferon-gamma (IFN-γ). Mature DCs were electroporated with messenger RNA (mRNA) encoding full-length antigen and cryopreserved. "Classical" DCs were cultured for 8 days in flasks, with one round of medium and cytokine supplementation, and matured with tumor necrosis factor alpha (TNF-α) + prostaglandin E2 (PGE2) during the last 2 days.

RESULTS

Four-day MPLA/IFN-γ-matured DCs were superior to 8-day TNF-α/PGE2-matured DCs in terms of yield, co-stimulatory/co-inhibitory molecule expression, resilience to electroporation and cryopreservation and type 1-polarizing cytokine and chemokine release after cell thawing. Electroporated and cryopreserved DCs according to our protocol efficiently present epitopes from tumor antigen-encoding mRNA, inducing a strong expansion of antigen-specific CD8+ T-cells with full cytolytic capacity.

CONCLUSION

We demonstrate using a GMP-compliant culture protocol the feasibility of generating high yields of mature DCs in a short time, with a superior immunogenic profile compared with 8-day TNF-α/PGE2-matured DCs, and capable of inducing vigorous cytotoxic T-cell responses to antigen from electroporated mRNA. This method is now being applied in our clinical trial program.

Strategies to Genetically Modulate Dendritic Cells to Potentiate Anti-Tumor Responses in Hematologic Malignancies

Dendritic cell (DC) vaccination has been investigated as a potential strategy to target hematologic malignancies, while generating sustained immunological responses to control potential future relapse. Nonetheless, few clinical trials have shown robust long-term efficacy. It has been suggested that a combination of surmountable shortcomings, such as selection of utilized DC subsets, DC loading and maturation strategies, as well as tumor-induced immunosuppression may be targeted to maximize anti-tumor responses of DC vaccines. Generation of DC from CD34+ hematopoietic stem and progenitor cells (HSPCs) may provide potential in patients undergoing allogeneic HSPC transplantations for hematologic malignancies. CD34+ HSPC from the graft can be genetically modified to optimize antigen presentation and to provide sufficient T cell stimulatory signals. We here describe beneficial (gene)-modifications that can be implemented in various processes in T cell activation by DC, among which major histocompatibility complex (MHC) class I and MHC class II presentation, DC maturation and migration, cross-presentation, co-stimulation, and immunosuppression to improve anti-tumor responses.

Tumor lysate particle loaded dendritic cell vaccine: preclinical testing of a novel personalized cancer vaccine

Aim: We developed a novel approach to efficiently deliver autologous tumor antigens to the cytoplasm of dendritic cells (DC) using yeast cell wall particles (YCWP). Materials and Methods: Loading of YCWP, leakage of protein from loaded YCWP and cytoplasmic delivery of YCWP content was assessed using fluorescent-tagged experiments. Spectrophotometric analysis compared the epitope-specific T-cell responses following antigen presentation via YCWP versus exogenous loading. The in vivo effectiveness of tumor lysate (TL) particle loaded DC (TLPLDC) vaccine was assessed using murine melanoma models. Results: In fluorescence-tagged experiments, YCWP efficiently delivered antigen to the cytoplasm of DC. TLPLDC loading was more effective than conventional exogenous loading of DC. Finally, in murine melanoma models, TLPLDC outperformed an analogous dendritoma vaccine. Conclusion: The TLPLDC vaccine is commercially scalable and holds the potential of producing personalized vaccines.

Exosomes derived from cancerous and non-cancerous cells regulate the anti-tumor response in the tumor microenvironment

The tumor microenvironment (TME) is a unique platform of cancer biology that considers the local cellular environment in which a tumor exists. Increasing evidence points to the TME as crucial for either promoting immune tumor rejection or protecting the tumor. The TME includes surrounding blood vessels, the extracellular matrix (ECM), a variety of immune and regulatory cells, and signaling factors. Exosomes have emerged to be molecular contributors in cancer biology, and to modulate and affect the constituents of the TME. Exosomes are small (40-150 nm) membrane vesicles that are derived from an endocytic nature and are later excreted by cells. Depending on the cells from which they originate, exosomes can play a role in tumor suppression or tumor progression. Tumor-derived exosomes (TDEs) have their own unique phenotypic functions. Evidence points to TDEs as key players involved in tumor growth, tumorigenesis, angiogenesis, dysregulation of immune cells and immune escape, metastasis, and resistance to therapies, as well as in promoting anti-tumor response. General exosomes, TDEs, and their influence on the TME are an area of promising research that may provide potential biomarkers for therapy, potentiation of anti-tumor response, development of exosome-based vaccines, and exosome-derived nanocarriers for drugs.

Hematologic neoplasms: Dendritic cells vaccines in motion

Dendritic cells (DCs) are bone-marrow-derived immune cells accounted for a key role in cancer vaccination as potent antigen-presenting cells within the immune system. Cancer microenvironment can modulate DCs maturation resulting in their accumulation into functional states associated with a reduced antitumor immune response. In this regard, a successful cancer vaccine needs to mount a potent antitumor immune response able to overcome the immunosuppressive tumor milieu. As a consequence, DCs-based approaches are a safe and promising strategy for improving the therapeutic efficacy in hematological malignancies, particularly in combinations with additional treatments. This review summarizes the most significant evidence about the immunotherapeutic strategies performed to target hematologic neoplasms including the tumoral associated antigens (TAA) pulsed on DCs, whole tumor cell vaccines or leukemia-derived DCs.

Dendritic cell based vaccination strategy: an evolving paradigm

Malignant gliomas (MG), tumors of glial origin, are the most commonly diagnosed primary intracranial malignancies in adults. Currently available treatments have provided only modest improvements in overall survival and remain limited by inevitable local recurrence, necessitating exploration of novel therapies. Among approaches being investigated, one of the leading contenders is immunotherapy, which aims to modulate immune pathways to stimulate the selective destruction of malignant cells. Dendritic cells (DCs) are potent initiators of adaptive immune responses and therefore crucial players in the development and success of immunotherapy. Clinical trials of various DC-based vaccinations have demonstrated the induction of anti-tumor immune responses and prolonged survival in the setting of many cancers. In this review, we summarize current literature regarding DCs and their role in the tumor microenvironment, their application and current clinical use in immunotherapy, current challenges limiting their efficacy in anti-cancer therapy, and future avenues for developing successful anti-tumor DC-based vaccines.

Dendritic Cell-Based Immunotherapy: State of the Art and Beyond

Dendritic cell (DC) vaccination in cancer patients aims to induce or augment an effective antitumor immune response against tumor antigens and was first explored in a clinical trial in the 1990s. More than two decades later, numerous clinical trials have been performed or are ongoing with a wide variety of DC subsets, culture protocols, and treatment regimens. The safety of DC vaccination and its ability to induce antitumor responses have clearly been established; however, although scattered patients with long-term benefit were reported, DC vaccines have not yet fulfilled their promise, perhaps mainly due to the lack of large-scale well-conducted phase II/III trials. To allow meaningful multicenter phase III trials, the production of DC vaccines should be standardized between centers which is now becoming feasible. To improve the efficacy of DC-based immunotherapy, it could be combined with other treatments.

Pathogen-Associated Molecular Patterns Induced Crosstalk between Dendritic Cells, T Helper Cells, and Natural Killer Helper Cells Can Improve Dendritic Cell Vaccination

A coordinated cellular interplay is of crucial importance in both host defense against pathogens and malignantly transformed cells. The various interactions of Dendritic Cells (DC), Natural Killer (NK) cells, and T helper (Th) cells can be influenced by a variety of pathogen-associated molecular patterns (PAMPs) and will lead to enhanced CD8⁺ effector T cell responses. Specific Pattern Recognition Receptor (PRR) triggering during maturation enables DC to enhance Th1 as well as NK helper cell responses. This effect is correlated with the amount of IL-12p70 released by DC. Activated NK cells are able to amplify the proinflammatory cytokine profile of DC via the release of IFN-γ. The knowledge on how PAMP recognition can modulate the DC is of importance for the design and definition of appropriate therapeutic cancer vaccines. In this review we will discuss the potential role of specific PAMP-matured DC in optimizing therapeutic DC-based vaccines, as some of these DC are efficiently activating Th1, NK cells, and cytotoxic T cells. Moreover, to optimize these vaccines, also the inhibitory effects of tumor-derived suppressive factors, for example, on the NK-DC crosstalk, should be taken into account. Finally, the suppressive role of the tumor microenvironment in vaccination efficacy and some proposals to overcome this by using combination therapies will be described.

CXCL11-Armed oncolytic poxvirus elicits potent antitumor immunity and shows enhanced therapeutic efficacy

We have armed a tumor-selective oncolytic vaccinia virus (vvDD) with the chemokine (CK) CXCL11, in order to enhance its ability to attract CXCR3⁺ antitumor CTLs and possibly NK cells to the tumor microenvironment (TME) and improve its therapeutic efficacy. As expected, vvDD-CXCL11 attracted high numbers of tumor-specific T cells to the TME in a murine AB12 mesothelioma model. Intratumoral virus-directed CXCL11 expression enhanced local numbers of CD8⁺ CTLs and levels of granzyme B, while reducing expression of several suppressive molecules, TGF-β, COX2, and CCL22 in the TME. Unexpectedly, we observed that vvDD-CXCL11, but not parental vvDD, induced a systemic increase in tumor-specific IFNγ-producing CD8⁺ T cells in the spleen and other lymph organs, indicating the induction of systemic antitumor immunity. This effect was associated with enhanced therapeutic efficacy and a survival benefit in tumor-bearing mice treated with vvDD-CXCL11, mediated by CD8⁺ T cells and IFNγ, but not CD4⁺ T cells. These results demonstrate that intratumoral expression of CXCL11, in addition to promoting local trafficking of T cells and to a lesser extent NK cells, has a novel function as a factor eliciting systemic immunity to cancer-associated antigens. Our data provide a rationale for expressing CXCL11 to enhance the therapeutic efficacy of oncolytic viruses (OVs) and cancer vaccines.

Dendritic cell immunotherapy for brain tumors

Glioblastomas are characterized by immunosuppression, rapid proliferation, angiogenesis, and invasion into the surrounding brain parenchyma. Limitations in current therapeutic approaches have spurred the development of personalized, patient-specific treatments. Among these, active immunotherapy has emerged as a viable option for glioma treatment. The ability to generate an immune response utilizing patient-derived dendritic cells (DCs) (professional antigen-presenting cells) is especially attractive. This approach to glioma treatment allows for the immunologic targeting and destruction of malignant cells. Data acquired in multiple pre-clinical models and clinical trials have shown significant responses and prolonged survival. Here we provide an overview of the current status of DC vaccination for the treatment of gliomas.

Cytokine-induced killer cells co-cultured with dendritic cells loaded with the protein lysate produced by radiofrequency ablation induce a specific antitumor response

Radiofrequency ablation (RFA) causes coagulative necrosis of tumor tissue and the production of local tumor protein debris. These fragments of tumor protein debris contain a large number of various antigens, which can stimulate a specific cellular immune response. In the present study, dendritic cells (DCs) were loaded with tumor protein lysate antigens that were produced in situ by RFA, and were used to treat murine colon carcinoma in combination with cytokine-induced killer (CIK) cells. Subsequent to the treatment of murine colon carcinoma by RFA, the in situ supernatant of tumor lysis was collected and the DCs were loaded with the lysate antigen to generate Ag-DCs. CIK cells induced from the spleen cells of mice were co-cultured with Ag-DCs to generate Ag-DC-CIK cells. The results revealed that the Ag-DC-CIK cells exhibited strong antitumor activity in vitro and in vivo. The morphology and immunophenotypes of these cells were determined using microscopy and flow cytometry, respectively. The cytotoxic activity of Ag-DC-CIK cells was determined using a CCK-8 assay. To establish a mouse model, mice were randomized into Ag-DC-CIK, DC-CIK, CIK and PBS control groups and monitored for tumor growth and survival time. ANOVA was used to compare the trends in the three groups for implanted tumor volumes. The log-rank test was used to compare the survival time. The present findings indicated that DCs loaded with the protein lysate antigens of tumors, produced in situ by RFA, combined with CIK cells may be a novel strategy for cancer treatment.

Extracorporeal photopheresis promotes IL-1β production

Extracorporeal photopheresis (ECP) is a widely used clinical cell-based therapy exhibiting efficacy in heterogenous immune-mediated diseases such as cutaneous T cell lymphoma, graft-versus-host disease, and organ allograft rejection. Despite its documented efficacy in cancer immunotherapy, little is known regarding the induction of immunostimulatory mediators by ECP. In this article, we show that ECP promotes marked release of the prototypic immunostimulatory cytokine IL-1β. ECP primes IL-1β production and activates IL-1β maturation and release in the context of caspase-1 activation in monocytes and myeloid dendritic cells. Of interest, IL-1β maturation by ECP was fully intact in murine cells deficient in caspase-1, suggesting the predominance of an inflammasome-independent pathway for ECP-dependent IL-1β maturation. Clinically, patient analysis revealed significantly increased IL-1β production in stimulated leukapheresis concentrates and peripheral blood samples after ECP. Collectively, these results provide evidence for promotion of IL-1β production by ECP and offer new insight into the immunostimulatory capacity of ECP.

Novel N-amidinopiperidine-based proteasome inhibitor preserves dendritic cell functionality and rescues their Th1-polarizing capacity in Ramos-conditioned tumor environment

The tumor microenvironment represents a burden that hampers the proper activation of immune cells, including the dendritic cells (DCs). It is, therefore, desired that the important characteristics of a given anticancer drug candidate be seen as consisting not solely of its antitumor properties, but that it also lacks potential side effects that could additionally constrain the development and function of immune cells associated with tumor immunity. We have previously identified compounds with a N-amidinopiperidine scaffold that selectively induce apoptosis in Burkitt's lymphoma cells through proteasome inhibition. Here, we demonstrate that SPI-15 affected neither the viability of DCs nor their differentiation. In addition, the compound had no significant effect on their cytokine secretion or allostimulatory capacity. Moreover, DC functionality in the context of tumor microenvironment was also unaffected, as demonstrated by experiments performed on DCs differentiated in Ramos-conditioned media in the presence or absence of SPI-15. The cytokine profile and functional assays revealed that SPI-15 rescues DC differentiation from the immunosuppressive environment produced by Ramos cells; this was seen by their reacquired ability to induce IFN-γ-secretion from naïve CD4(+)CD45RA(+) T cells and the consequently induced Th1-effector differentiation. Herein, we present novel characteristics of an N-amidinopiperidine-based protease inhibitor whose anticancer properties are not associated with the immunosuppression of DCs. We propose future studies toward the design of structurally similar compounds with the aim of developing potent anticancer drugs with minimal negative effects on crucial factors involved in tumor immunity.

Enhancing dendritic cell-based vaccination for highly aggressive glioblastoma

INTRODUCTION

Patients with primary glioblastoma (GBM) have a dismal prognosis despite standard therapy, which can induce potentially deleterious side effects. Arming the immune system is an alternative therapeutic approach, as its cellular effectors and inherent capacity for memory can be utilized to specifically target invasive tumor cells, while sparing collateral damage to otherwise healthy brain parenchyma.

AREAS COVERED

Active immunotherapy is aimed at eliciting a specific immune response against tumor antigens. Dendritic cells (DCs) are one of the most potent activators of de novo and recall immune responses and are thus a vehicle for successful immunotherapy. Currently, investigators are optimizing DC vaccines by enhancing maturation status and migratory potential to induce more potent antitumor responses. An update on the most recent DC immunotherapy trials is provided.

EXPERT OPINION

Targeting of unique antigens restricted to the tumor itself is the most important parameter in advancing DC vaccines. In order to overcome intrinsic mechanisms of immune evasion observed in GBM, the future of DC-based therapy lies in a multi-antigenic vaccine approach. Successful targeting of multiple antigens will require a comprehensive understanding of all immunologically relevant oncological epitopes present in each tumor, thereby permitting a rational vaccine design.

Adaptive Resistance to Immunotherapy Directed Against p53 Can be Overcome by Global Expression of Tumor-Antigens in Dendritic Cells

Immunotherapy of cancer utilizes dendritic cells (DCs) for antigen presentation and the induction of tumor-specific immune responses. However, the therapeutic induction of anti-tumor immunity is limited by tumor escape mechanisms. In this study, immortalized dendritic D2SC/1 cells were transduced with a mutated version of the p53 tumor suppressor gene, p53M234I, or p53C132F/E168G, which are overexpressed in MethA fibrosarcoma tumor cells. In addition, D2SC/1 cells were fused with MethA tumor cells to generate a vaccine that potentially expresses a large repertoire of tumor-antigens. Cellular vaccines were transplanted onto Balb/c mice and MethA tumor growth and anti-tumor immune responses were examined in vaccinated animals. D2SC/1–p53M234I and D2SC/1–p53C132F/E168G cells induced strong therapeutic and protective MethA tumor immunity upon transplantation in Balb/c mice. However, in a fraction of immunized mice MethA tumor growth resumed after an extended latency period. Analysis of these tumors indicated loss of p53 expression. Mice, pre-treated with fusion hybrids generated from D2SC/1 and MethA tumor cells, suppressed MethA tumor growth and averted adaptive immune escape. Polyclonal B-cell responses directed against various MethA tumor proteins could be detected in the sera of D2SC/1–MethA inoculated mice. Athymic nude mice and Balb/c mice depleted of CD4⁺ or CD8⁺ T-cells were not protected against MethA tumor cell growth after immunization with D2SC/1–MethA hybrids. Our results highlight a potential drawback of cancer immunotherapy by demonstrating that the induction of a specific anti-tumor response favors the acquisition of tumor phenotypes promoting immune evasion. In contrast, the application of DC/tumor cell fusion hybrids prevents adaptive immune escape by a T-cell dependent mechanism and provides a simple strategy for personalized anti-cancer treatment without the need of selectively priming the host immune system.

Therapeutic cancer vaccines and combination immunotherapies involving vaccination

Recent US Food and Drug Administration approvals of Provenge(®) (sipuleucel-T) as the first cell-based cancer therapeutic factor and ipilimumab (Yervoy(®)/anticytotoxic T-lymphocyte antigen-4) as the first "checkpoint blocker" highlight recent advances in cancer immunotherapy. Positive results of the clinical trials evaluating additional checkpoint blocking agents (blockade of programmed death [PD]-1, and its ligands, PD-1 ligand 1 and 2) and of several types of cancer vaccines suggest that cancer immunotherapy may soon enter the center stage of comprehensive cancer care, supplementing surgery, radiation, and chemotherapy. This review discusses the current status of the clinical evaluation of different classes of therapeutic cancer vaccines and possible avenues for future development, focusing on enhancing the magnitude and quality of cancer-specific immunity by either the functional reprogramming of patients' endogenous dendritic cells or the use of ex vivo-manipulated dendritic cells as autologous cellular transplants. This review further discusses the available strategies aimed at promoting the entry of vaccination-induced T-cells into tumor tissues and prolonging their local antitumor activity. Finally, the recent improvements to the above three modalities for cancer immunotherapy (inducing tumor-specific T-cells, prolonging their persistence and functionality, and enhancing tumor homing of effector T-cells) and rationale for their combined application in order to achieve clinically effective anticancer responses are addressed.

OK-432 synergizes with IFN-γ to confer dendritic cells with enhanced antitumor immunity

Generation of functional dendritic cells (DCs) with boosted immunity after the withdrawal of initial activation/maturation conditions remains a significant challenge. In this study, we investigated the impact of a newly developed maturation cocktail consisting of OK-432 and interferon-gamma (IFN-γ) on the function of human monocyte-derived DCs (MoDCs). We found that OK-432 plus IFN-γ stimulation could induce significantly stronger expression of surface molecules, production of cytokines, as well as migration of DCs compared with OK-432 stimulation alone. Most importantly, DCs matured with OK-432 plus IFN-γ-induced maintained secretion of interleukin-12 (IL-12)p70 in secondary culture after stimulus withdrawal. Functionally, OK-432 plus IFN-γ-conditioned DCs induce remarkable Th1 and Tc1 responses more effectively than OK-432 alone, even more than the use of α-type-1 cytokine cocktail. As a result, DCs matured with OK-432 plus IFN-γ can prime stronger cytotoxic lymphocyte (CTL) and natural killer (NK) cell response against tumor cells in vitro. Peripheral blood mononuclear cells activated by DCs matured with OK-432 plus IFN-γ also showed greater tumor growth inhibition in vivo in null mice. Molecular mechanistic analysis showed that DC maturation using IFN-γ in concert with OK-432 involves the activation of p38 and nuclear factor-kappa B (NF-κB) pathways. This study provided a novel strategy to generate more potent immune segments in DC vaccine.

Immune adjuvants as critical guides directing immunity triggered by therapeutic cancer vaccines

Tumor growth is controlled by natural antitumor immune responses alone or by augmented immune reactivity resulting from different forms of immunotherapy, which has demonstrated clinical benefit in numerous studies, although the overall percentage of patients with durable clinical responses remains limited. This is attributed to the heterogeneity of the disease, the inclusion of late-stage patients with no other treatment options and advanced tumor-associated immunosuppression, which may be consolidated by certain types of chemotherapy. Despite variable responsiveness to distinct types of immunotherapy, therapeutic cancer vaccination has shown meaningful efficacy for a variety of cancers. A key step during cancer vaccination involves the appropriate modeling of the functional state of dendritic cells (DCs) capable of co-delivering four critical signals for proper instruction of tumor antigen-specific T cells. However, the education of DCs, either directly in situ, or ex vivo by various complex procedures, lacks standardization. Also, it is questioned whether ex vivo-prepared DC vaccines are superior to in situ-administered adjuvant-guided vaccines, although both approaches have shown success. Evaluation of these variables is further complicated by a lack of consensus in evaluating vaccination clinical study end points. We discuss the role of signals needed for the preparation of classic in situ and modern ex vivo DC vaccines capable of proper reprogramming of antitumor immune responses in patients with cancer.

Dendritic cells in cancer immunotherapy: vaccines and combination immunotherapies

Dendritic cells (DCs) are specialized immunostimulatory cells involved in the induction and regulation of immune responses. The feasibility of large-scale ex vivo generation of DCs from patients' monocytes allows for therapeutic application of ex vivo-cultured DCs to bypass the dysfunction of endogenous DCs, restore immune surveillance, induce cancer regression or stabilization or delay or prevent its recurrence. While the most common paradigm of the therapeutic application of DCs reflects their use as cancer 'vaccines', additional and potentially more effective possibilities include the use of patients' autologous DCs as parts of more comprehensive therapies involving in vivo or ex vivo induction of tumor-reactive T cells and the measures to counteract systemic and local immunosuppression in tumor-bearing hosts. Ex vivo-cultured DCs can be instructed to acquire distinct functions relevant for the induction of effective cancer immunity (DC polarization), such as the induction of different effector functions or different homing properties of tumor-specific T cells (delivery of 'signal 3' and 'signal 4'). These considerations highlight the importance of the application of optimized conditions for the ex vivo culture of DCs and the potential combination of DC therapies with additional immune interventions to facilitate the entry of DC-induced T cells to tumor tissues and their local antitumor functions.

Oncolytic viruses as therapeutic cancer vaccines

Oncolytic viruses (OVs) are tumor-selective, multi-mechanistic antitumor agents. They kill infected cancer and associated endothelial cells via direct oncolysis, and uninfected cells via tumor vasculature targeting and bystander effect. Multimodal immunogenic cell death (ICD) together with autophagy often induced by OVs not only presents potent danger signals to dendritic cells but also efficiently cross-present tumor-associated antigens from cancer cells to dendritic cells to T cells to induce adaptive antitumor immunity. With this favorable immune backdrop, genetic engineering of OVs and rational combinations further potentiate OVs as cancer vaccines. OVs armed with GM-CSF (such as T-VEC and Pexa-Vec) or other immunostimulatory genes, induce potent anti-tumor immunity in both animal models and human patients. Combination with other immunotherapy regimens improve overall therapeutic efficacy. Coadministration with a HDAC inhibitor inhibits innate immunity transiently to promote infection and spread of OVs, and significantly enhances anti-tumor immunity and improves the therapeutic index. Local administration or OV mediated-expression of ligands for Toll-like receptors can rescue the function of tumor-infiltrating CD8⁺ T cells inhibited by the immunosuppressive tumor microenvironment and thus enhances the antitumor effect. Combination with cyclophosphamide further induces ICD, depletes Treg, and thus potentiates antitumor immunity. In summary, OVs properly armed or in rational combinations are potent therapeutic cancer vaccines.

Immune response, clinical outcome and safety of dendritic cell vaccine in combination with cytokine-induced killer cell therapy in cancer patients

The aim of the present study was to determine the clinical value of autologous immunocyte therapy as a standard treatment regimen for patients with cancer. A total of 121 patients with cancer were included in this study. Subsequent to performing leukapheresis using the Fresenius Kabi System, 1×10⁷ dendritic cells (DCs) for the vaccine and 1×10⁹ cytokine-induced killer (CIK) cells for injection were prepared. An analysis of the immune phenotypes of HLA2DR, CD80 and CD83 for the DCs and of CD3, CD8 and CD56 for the CIK cells, as well as negative detection of bacteria and endotoxin, were used as the quality standards. The delayed-type hyper-sensitivity (DTH) skin test was used to measure the immune response, while physical strength, appetite and sleeping status were analyzed for the clinical outcome. Fever, insomnia, anorexia, joint soreness and skin rashes were recorded as side-effects. Patients received the DC vaccination once a week for six weeks and a CIK cell injection six times within four days. In total, 121 cancer patients with primary tumors located in the colorectum (43.0%), lung (15.7%), breast (11.6%), kidney (5.8%), stomach (4.1%) and other regions (19.8%) were included in the study. A positive cell-mediated cytotoxicity response rate of 76.9% was detected by the DTH skin tests. Improvements in physical strength, appetite and sleeping status were observed in 94.1, 83.9 and 76.3% of cases, respectively. None of the serious adverse side-effects that commonly occur during chemotherapy and radiotherapy were observed. During therapy, 69 cases developed a fever that was resolved with antipyretics, dexamethasone or physical cooling, while 28 cases developed insomnia combined with excitement, 19 cases complained of anorexia, 11 cases complained of joint soreness, which was alleviated using analgesics, and 8 cases developed skin rashes. The combined use of CIK cells with a DC-based cancer vaccination strategy may be used to target innate and adaptive immune mechanisms and synergistically promote positive clinical outcomes. The therapy was safe and no serious adverse side-effects similar to those caused by chemotherapy and radiotherapy were observed. The regimen may have a beneficial effect in the future treatment of patients with cancer.

In vivo intracellular oxygen dynamics in murine brain glioma and immunotherapeutic response of cytotoxic T cells observed by fluorine-19 magnetic resonance imaging

Noninvasive biomarkers of anti-tumoral efficacy are of great importance to the development of therapeutic agents. Tumor oxygenation has been shown to be an important indicator of therapeutic response. We report the use of intracellular labeling of tumor cells with perfluorocarbon (PFC) molecules, combined with quantitative ¹⁹F spin-lattice relaxation rate (R₁) measurements, to assay tumor cell oxygen dynamics in situ. In a murine central nervous system (CNS) GL261 glioma model, we visualized the impact of Pmel-1 cytotoxic T cell immunotherapy, delivered intravenously, on intracellular tumor oxygen levels. GL261 glioma cells were labeled ex vivo with PFC and inoculated into the mouse striatum. The R₁ of ¹⁹F labeled cells was measured using localized single-voxel magnetic resonance spectroscopy, and the absolute intracellular partial pressure of oxygen (pO₂) was ascertained. Three days after tumor implantation, mice were treated with 2×10⁷ cytotoxic T cells intravenously. At day five, a transient spike in pO₂ was observed indicating an influx of T cells into the CNS and putative tumor cell apoptosis. Immunohistochemistry and quantitative flow cytometry analysis confirmed that the pO₂ was causally related to the T cells infiltration. Surprisingly, the pO₂ spike was detected even though few (∼4×10⁴) T cells actually ingress into the CNS and with minimal tumor shrinkage. These results indicate the high sensitivity of this approach and its utility as a non-invasive surrogate biomarker of anti-cancer immunotherapeutic response in preclinical models.

Langerhans cells and T cells sense cell dysplasia in oral leukoplakias and oral squamous cell carcinomas--evidence for immunosurveillance

Leukoplakias (LPLs) are lesions in the oral mucosa that may develop into oral squamous cell carcinoma (OSCC). The objective of this study was to assess presence and distribution of dendritic Langerhans cells (LCs) and T cells in patients with LPLs with or without cell dysplasia and in oral squamous cell carcinoma (OSCC). Biopsy specimens from patients with leukoplakias (LPLs) with or without dysplasia and oral squamous cell carcinoma (OSCC) were immunostained with antibodies against CD1a, Langerin, CD3, CD4, CD8 and Ki67, followed by quantitative analysis. Analyses of epithelium and connective tissue revealed a significantly higher number of CD1a + LCs in LPLs with dysplasia compared with LPLs without dysplasia. Presence of Langerin + LCs in epithelium did not differ significantly between LPLs either with or without dysplasia and OSCC. T cells were found in significantly increased numbers in LPLs with dysplasia and OSCC. The number of CD4+ cells did not differ significantly between LPLs with and without dysplasia, but a significant increase was detected when comparing LPLs with dysplasia with OSCC. CD8+ cells were significantly more abundant in OSCC and LPLs with dysplasia compared with LPLs without dysplasia. Proliferating cells (Ki67+) were significantly more abundant in OSCC compared to LPLs with dysplasia. Confocal laser scanning microscopy revealed colocalization of LCs and T cells in LPLs with dysplasia and in OSCC. LCs and T cells are more numerous in tissue compartments with dysplastic epithelial cells and dramatically increase in OSCC. This indicates an ongoing immune response against cells with dysplasia.

Immunotherapy of cancer in 2012

The immunotherapy of cancer has made significant strides in the past few years due to improved understanding of the underlying principles of tumor biology and immunology. These principles have been critical in the development of immunotherapy in the laboratory and in the implementation of immunotherapy in the clinic. This improved understanding of immunotherapy, enhanced by increased insights into the mechanism of tumor immune response and its evasion by tumors, now permits manipulation of this interaction and elucidates the therapeutic role of immunity in cancer. Also important, this improved understanding of immunotherapy and the mechanisms underlying immunity in cancer has fueled an expanding array of new therapeutic agents for a variety of cancers. Pegylated interferon-α2b as an adjuvant therapy and ipilimumab as therapy for advanced disease, both of which were approved by the United States Food and Drug Administration for melanoma in March 2011, are 2 prime examples of how an increased understanding of the principles of tumor biology and immunology have been translated successfully from the laboratory to the clinical setting. Principles that guide the development and application of immunotherapy include antibodies, cytokines, vaccines, and cellular therapies. The identification and further elucidation of the role of immunotherapy in different tumor types, and the development of strategies for combining immunotherapy with cytotoxic and molecularly targeted agents for future multimodal therapy for cancer will enable even greater progress and ultimately lead to improved outcomes for patients receiving cancer immunotherapy.

Enhancement of protective immunity against intracellular bacteria using type-1 polarized dendritic cell (DC) vaccine

The development of effective vaccine strategies for intracellular bacteria, including tuberculosis, is one of the major frontiers of medical research. Our previous studies showed that dendritic cell (DC) vaccine is a promising approach for eliciting protective immunity against intracellular bacteria. However, it has been reported that standard fully mature DCs show reduced ability to produce IL-12p70 upon subsequent interaction with antigen (Ag)-specific T cells, limiting their in vivo performance for vaccines. Recently, we found that such "DC exhaustion" could be prevented by the presence of IL-4 and IFN-γ during the maturation of mouse DCs (type-1 polarization), resulting in improved induction of anti-tumor immunity in cancer. Here we show that such type-1 polarized DCs promote dramatic enhancement of protective immunity against an intracellular bacterium, Listeria monocytogenes. Murine bone marrow-derived DCs were cultured and matured with LPS, IL-4 and IFN-γ (type-1 polarized DCs), and with LPS alone (non-polarized DCs). DCs were loaded with listeriolysin O (LLO) 91-99, H2-K(d)-restricted epitope of L. monocytogenes, and were injected into naïve BALB/c mice intravenously. Type-1 polarized DCs produced significantly higher levels of IL-12p70 than non-polarized DCs in vitro, and this vaccine strongly enhanced LLO 91-99-specific CD8(+) T cells exhibiting epitope-specific cytotoxic activity and IFN-γ production, leading to significant induction of protective immunity against L. monocytogenes. Type-1 polarized DCs are potential candidates for enhancing protective immunity in the design of effective vaccination strategies against intracellular bacteria.

Differential effects of monophosphoryl lipid A and cytokine cocktail as maturation stimuli of immunogenic and tolerogenic dendritic cells for immunotherapy

Immunotherapy using monocyte-derived dendritic cells (MDDC) is increasingly being considered as alternative therapeutic approach in cancer, infectious diseases and also in autoimmunity when patients are not responsive to conventional treatments. In general, generation of MDDC from monocytes is induced in the presence of GM-CSF and IL-4, and a maturation stimulus is added to the culture to obtain mature DCs suitable for therapy. For DC maturation, different combinations of pro-inflammatory mediators and Toll-like receptor ligands have been tested, obtaining DCs that differ in their properties and the type of immune response they promote. Therefore, it is necessary to find an optimal cytokine environment for DC maturation to obtain a cellular product suitable for DC-based immunotherapeutic protocols. In this study, we have evaluated in vitro the effects of different maturation stimuli on the viability, phenotype, cytokine profile, stability and functionality of immunogenic and tolerogenic (1α,25-dihydroxyvitamin D(3)-treated) MDDC. Maturation was induced using the clinical grade TLR4-agonist: monophosphoryl lipid A (LA), compared to the traditional cytokine cocktail (CC; clinical grade TNF-α, IL-1β, PGE2) and a combination of both. Our results showed the combination of CC+LA rendered a potent immunogenic DC population that induced the production of IFN-γ and IL-17 in allogeneic co-cultures, suggesting a Th17 polarization. Moreover, these immunogenic DCs showed a high surface expression of CD83, CD86, HLA-DR and secretion of IL-12p70. When aiming to induce tolerance, using LA to generate mature TolDC did not represent a clear advantage, and the stability and the suppressive capability exhibited by CC-matured TolDC may represent the best option. Altogether, these findings demonstrate the relevance of an appropriate maturation stimulus to rationally modulate the therapeutic potential of DCs in immunotherapy.

Pilot clinical trial of type 1 dendritic cells loaded with autologous tumor lysates combined with GM-CSF, pegylated IFN, and cyclophosphamide for metastatic cancer patients

Twenty-four patients with metastatic cancer received two cycles of four daily immunizations with monocyte-derived dendritic cells (DC). DC were incubated with preheated autologous tumor lysate and subsequently with IFN-α, TNF-α, and polyinosinic:polycytidylic acid to attain type 1 maturation. One DC dose was delivered intranodally, under ultrasound control, and the rest intradermally in the opposite thigh. Cyclophosphamide (day -7), GM-CSF (days 1-4), and pegIFN alpha-2a (days 1 and 8) completed each treatment cycle. Pretreatment with cyclophosphamide decreased regulatory T cells to levels observed in healthy subjects both in terms of percentage and in absolute counts in peripheral blood. Treatment induced sustained elevations of IL-12 in serum that correlated with the output of IL-12p70 from cultured DC from each individual. NK activity in peripheral blood was increased and also correlated with the serum concentration of IL-12p70 in each patient. Circulating endothelial cells decreased in 17 of 18 patients, and circulating tumor cells markedly dropped in 6 of 19 cases. IFN-γ-ELISPOT responses to DC plus tumor lysate were observed in 4 of 11 evaluated cases. Tracing DC migration with [(111)In] scintigraphy showed that intranodal injections reached deeper lymphatic chains in 61% of patients, whereas with intradermal injections a small fraction of injected DC was almost constantly shown to reach draining inguinal lymph nodes. Five patients experienced disease stabilization, but no objective responses were documented. This combinatorial immunotherapy strategy is safe and feasible, and its immunobiological effects suggest potential activity in patients with minimal residual disease. A randomized trial exploring this hypothesis is currently ongoing.

Dendritic cells in cancer immunotherapy: vaccines or autologous transplants?

Dendritic cells (DCs) are the most powerful immunostimulatory cells specialized in the induction and regulation of immune responses. Their properties and the feasibility of their large-scale ex vivo generation led to the application of ex vivo-educated DCs to bypass the dysfunction of endogenous DCs in cancer patients and to induce therapeutic anti-cancer immunity. While multiple paradigms of therapeutic application of DCs reflect their consideration as cancer "vaccines", numerous features of DC-based vaccination resemble those of autologous transplants, resulting in challenges and opportunities that distinguish them from classical vaccines. In addition to the functional heterogeneity of DC subsets and plasticity of the individual DC types, the unique features of DCs are the kinetic character of their function, limited functional stability, and the possibility to imprint in maturing DCs distinct functions relevant for the induction of effective cancer immunity, such as the induction of different effector functions or different homing properties of tumor-specific T cells (delivery of "signal 3" and "signal 4"). These considerations highlight the importance of the application of optimized, potentially patient-specific conditions of ex vivo culture of DCs and their delivery, with the logistic and regulatory implications shared with transplantation and other surgical procedures.

Overlapping, additive and counterregulatory effects of type II and I interferons on myeloid dendritic cell functions

Dendritic cells (DCs) are central player in immunity by bridging the innate and adaptive arms of the immune system (IS). Interferons (IFNs) are one of the most important factors that regulate both innate and adaptive immunity too. Thus, the understanding of how type II and I IFNs modulate the immune-regulatory properties of DCs is a central issue in immunology. In this paper, we will address this point in the light of the most recent literature, also highlighting the controversial data reported in the field. According to the wide literature available, type II as well as type I IFNs appear, at the same time, to collaborate, to induce additive effects or overlapping functions, as well as to counterregulate each one's effects on DC biology and, in general, the immune response. The knowledge of these effects has important therapeutic implications in the treatment of infectious/autoimmune diseases and cancer and indicates strategies for using IFNs as vaccine adjuvants and in DC-based immune therapeutic approaches.