Delivery of dendritic cells engineered to secrete IFN-alpha into central nervous system tumors enhances the efficacy of peripheral tumor cell vaccines: dependence on apoptotic pathways

Ribonucleic Acid Engineering of Dendritic Cells for Therapeutic Vaccination: Ready 'N Able to Improve Clinical Outcome?

Targeting and exploiting the immune system has become a valid alternative to conventional options for treating cancer and infectious disease. Dendritic cells (DCs) take a central place given their role as key orchestrators of immunity. Therapeutic vaccination with autologous DCs aims to stimulate the patient's own immune system to specifically target his/her disease and has proven to be an effective form of immunotherapy with very little toxicity. A great amount of research in this field has concentrated on engineering these DCs through ribonucleic acid (RNA) to improve vaccine efficacy and thereby the historically low response rates. We reviewed in depth the 52 clinical trials that have been published on RNA-engineered DC vaccination, spanning from 2001 to date and reporting on 696 different vaccinated patients. While ambiguity prevents reliable quantification of effects, these trials do provide evidence that RNA-modified DC vaccination can induce objective clinical responses and survival benefit in cancer patients through stimulation of anti-cancer immunity, without significant toxicity. Succinct background knowledge of RNA engineering strategies and concise conclusions from available clinical and recent preclinical evidence will help guide future research in the larger domain of DC immunotherapy.

The Role of TRAIL/DRs in the Modulation of Immune Cells and Responses

Expression of TRAIL (tumor necrosis factor–related apoptosis–inducing ligand) by immune cells can lead to the induction of apoptosis in tumor cells. However, it becomes increasingly clear that the interaction of TRAIL and its death receptors (DRs) can also directly impact immune cells and influence immune responses. Here, we review what is known about the role of TRAIL/DRs in immune cells and immune responses in general and in the tumor microenvironment in particular.

Current Options and Future Directions in Immune Therapy for Glioblastoma

Glioblastoma is in need of innovative treatment approaches. Immune therapy for cancer refers to the use of the body's immune system to target malignant cells in the body. Such immune therapeutics have recently been very successful in treating a diverse group of cancerous lesions. As a result, many new immune therapies have gained Food and Drug Administration approval for the treatment of cancer, and there has been an explosion in the study of immune therapeutics for cancer treatment over the past few years. However, the immune suppression of glioblastoma and the unique immune microenvironment of the brain make immune therapeutics more challenging to apply to the brain than to other systemic cancers. Here, we discuss the existing barriers to successful immune therapy for glioblastoma and the ongoing development of immune therapeutics. We will discuss the discovery and classification of immune suppressive factors in the glioblastoma microenvironment; the development of vaccine-based therapies; the use of convection-enhanced delivery to introduce tumoricidal viruses into the tumor microenvironment, leading to secondary immune responses; the emerging use of adoptive cell therapy in the treatment of glioblastoma; and future frontiers, such as the use of cerebral microdialysis for immune monitoring and the use of sequencing to develop patient-specific therapeutics. Armed with a better understanding of the challenges inherent in immune therapy for glioblastoma, we may soon see more successes in immune-based clinical trials for this deadly disease.

Two-photon probes for in vivo multicolor microscopy of the structure and signals of brain cells

Imaging the brain of living laboratory animals at a microscopic scale can be achieved by two-photon microscopy thanks to the high penetrability and low phototoxicity of the excitation wavelengths used. However, knowledge of the two-photon spectral properties of the myriad fluorescent probes is generally scarce and, for many, non-existent. In addition, the use of different measurement units in published reports further hinders the design of a comprehensive imaging experiment. In this review, we compile and homogenize the two-photon spectral properties of 280 fluorescent probes. We provide practical data, including the wavelengths for optimal two-photon excitation, the peak values of two-photon action cross section or molecular brightness, and the emission ranges. Beyond the spectroscopic description of these fluorophores, we discuss their binding to biological targets. This specificity allows in vivo imaging of cells, their processes, and even organelles and other subcellular structures in the brain. In addition to probes that monitor endogenous cell metabolism, studies of healthy and diseased brain benefit from the specific binding of certain probes to pathology-specific features, ranging from amyloid-β plaques to the autofluorescence of certain antibiotics. A special focus is placed on functional in vivo imaging using two-photon probes that sense specific ions or membrane potential, and that may be combined with optogenetic actuators. Being closely linked to their use, we examine the different routes of intravital delivery of these fluorescent probes according to the target. Finally, we discuss different approaches, strategies, and prerequisites for two-photon multicolor experiments in the brains of living laboratory animals.

Immunomodulatory and antitumor effects of type I interferons and their application in cancer therapy

During the last decades, the pleiotropic antitumor functions exerted by type I interferons (IFNs) have become universally acknowledged, especially their role in mediating interactions between the tumor and the immune system. Indeed, type I IFNs are now appreciated as a critical component of dendritic cell (DC) driven T cell responses to cancer. Here we focus on IFN-α and IFN-β, and their antitumor effects, impact on immune responses and their use as therapeutic agents. IFN-α/β share many properties, including activation of the JAK-STAT signaling pathway and induction of a variety of cellular phenotypes. For example, type I IFNs drive not only the high maturation status of DCs, but also have a direct impact in cytotoxic T lymphocytes, NK cell activation, induction of tumor cell death and inhibition of angiogenesis. A variety of stimuli, including some standard cancer treatments, promote the expression of endogenous IFN-α/β, which then participates as a fundamental component of immunogenic cell death. Systemic treatment with recombinant protein has been used for the treatment of melanoma. The induction of endogenous IFN-α/β has been tested, including stimulation through pattern recognition receptors. Gene therapies involving IFN-α/β have also been described. Thus, harnessing type I IFNs as an effective tool for cancer therapy continues to be studied.

The development of dendritic cell vaccine-based immunotherapies for glioblastoma

In this review, we focus on the biologic advantages of dendritic cell-based vaccinations as a therapeutic strategy for cancer as well as preclinical and emerging clinical data associated with such approaches for glioblastoma patients.

Principles of immunology and its nuances in the central nervous system

Cancer immunotherapy represents the biggest change in the cancer treatment landscape in the last several years. Indeed, the clinical successes in several cancer types have generated widespread enthusiasm that immune-based treatments may influence the management of patients with malignant brain tumors as well. A number of promising clinical trials in this area are currently ongoing in neuro-oncology, and a wave of additional efforts are sure to follow. However, the basic immunology underlying immunotherapy-and the nuances unique to the immunobiology in the central nervous system-is often not in the daily lexicon of the practicing neuro-oncologist and neurosurgeon. To this end, here we provide a timely and working overview of key principles of fundamental immunology as a pragmatic context for understanding where therapeutic efforts may act in the cellular dynamics of the immune response. Moreover, we review the issues of lymphatic drainage, antigen presentation, and the blood-brain barrier as considerations that are germane to thinking about immunity to tumors arising in the brain. Together, these topics will provide a foundation for the exciting efforts in immune-based treatments that will hopefully provide real benefit to brain tumor patients.

Cellular immunotherapy for malignant gliomas

INTRODUCTION

Cancer immunotherapy has made much progress in recent years. Clinical trials evaluating a variety of immunotherapeutic approaches are underway in patients with malignant gliomas. Thanks to recent advancements in cell engineering technologies, infusion of ex vivo prepared immune cells have emerged as promising strategies of cancer immunotherapy.

AREAS COVERED

Herein, the authors review recent and current studies using cellular immunotherapies for malignant gliomas. Specifically, they cover the following areas: a) cellular vaccine approaches using tumor cell-based or dendritic cell (DC)-based vaccines, and b) adoptive cell transfer (ACT) approaches, including lymphokine-activated killer (LAK) cells, γδ T cells, tumor-infiltrating lymphocytes (TIL), chimeric antigen receptor (CAR)-T cells and T-cell receptor (TCR) transduced T cells.

EXPERT OPINION

While some of the recent studies have shown promising results, the ultimate success of cellular immunotherapy in brain tumor patients would require improvements in the following areas: 1) feasibility in producing cellular therapeutics; 2) identification and characterization of targetable antigens given the paucity and heterogeneity of tumor specific antigens; 3) the development of strategies to promote effector T-cell trafficking; 4) overcoming local and systemic immune suppression, and 5) proper interpretation of imaging data for brain tumor patients receiving immunotherapy.

Engineering monocyte-derived dendritic cells to secrete interferon-α enhances their ability to promote adaptive and innate anti-tumor immune effector functions

Dendritic cell (DC) vaccination has demonstrated potential in clinical trials as a new effective cancer treatment, but objective and durable clinical responses are confined to a minority of patients. Interferon (IFN)-α, a type-I IFN, can bolster anti-tumor immunity by restoring or increasing the function of DCs, T cells and natural killer (NK) cells. Moreover, type-I IFN signaling on DCs was found to be essential in mice for tumor rejection by the innate and adaptive immune system. Targeted delivery of IFN-α by DCs to immune cells could boost the generation of anti-tumor immunity, while avoiding the side effects frequently associated with systemic administration. Naturally circulating plasmacytoid DCs, major producers of type-I IFN, were already shown capable of inducing tumor antigen-specific T cell responses in cancer patients without severe toxicity, but their limited number complicates their use in cancer vaccination. In the present work, we hypothesized that engineering easily generated human monocyte-derived mature DCs to secrete IFN-α using mRNA electroporation enhances their ability to promote adaptive and innate anti-tumor immunity. Our results show that IFN-α mRNA electroporation of DCs significantly increases the stimulation of tumor antigen-specific cytotoxic T cell as well as anti-tumor NK cell effector functions in vitro through high levels of IFN-α secretion. Altogether, our findings mark IFN-α mRNA-electroporated DCs as potent inducers of both adaptive and innate anti-tumor immunity and pave the way for clinical trial evaluation in cancer patients.

Overview of current immunotherapeutic strategies for glioma

In the last decade, numerous studies of immunotherapy for malignant glioma (glioblastoma multiforme) have brought new knowledge and new hope for improving the prognosis of this incurable disease. Some clinical trials have reached Phase III, following positive outcomes in Phase I and II, with respect to safety and immunological end points. Results are encouraging especially when considering the promise of sustained efficacy by inducing antitumor immunological memory. Progress in understanding the mechanisms of tumor-induced immune suppression led to the development of drugs targeting immunosuppressive checkpoints, which are used in active clinical trials for glioblastoma multiforme. Insights related to the heterogeneity of the disease bring new challenges for the management of glioma and underscore a likely cause of therapeutic failure. An emerging therapeutic strategy is represented by a combinatorial, personalized approach, including the standard of care: surgery, radiation, chemotherapy with added active immunotherapy and multiagent targeting of immunosuppressive checkpoints.

Increasing glioma-associated monocytes leads to increased intratumoral and systemic myeloid-derived suppressor cells in a murine model

BACKGROUND

Patients with glioblastoma multiforme (GBM) exhibit marked intratumoral and systemic immunosuppression. GBM is heavily infiltrated with monocytic cells. Monocytes contacting GBM cells develop features of immunosuppressive myeloid-derived suppressor cells (MDSCs), which are elevated in GBM patients. Therefore, we hypothesized that circulating MDSC levels could be raised in vivo by increasing glioma-associated macrophages.

METHODS

GL261-luciferase glioma was implanted intracranially in C57BL/6 mice with or without additional normal syngeneic CD11b+ monocytes. Tumor growth and intratumoral and systemic MDSC (CD11b+/Gr-1+) levels were determined. Green fluorescent protein (GFP)-transgenic monocytes were coinjected intracranially with GL261-luciferase cells. GFP+ cell frequency among splenic and bone marrow MDSCs was determined. Impact of increased MDSC's on spontaneous immune responses to tumor cells expressing a model antigen (ovalbumin [OVA]) was determined.

RESULTS

Tumors grew faster and MDSC's were increased in tumor, spleen, and bone marrow in mice receiving GL261-Luc plus monocytes. Many (30%-50%) systemic MDSC's were GFP+ in mice receiving intracranial tumor plus GFP-transgenic monocytes, suggesting that they originated from glioma-associated monocytes. Tumor-infiltrating OVA-specific CD8+ T cells were markedly reduced in mice receiving GL261-OVA and monocytes compared with mice receiving GL261-OVA alone.

CONCLUSIONS

Increasing glioma-associated macrophages in intracranial GL261 glioma decreases survival and markedly increases intratumoral and systemic MDSC's, many of which originate directly from glioma-associated macrophages. This is associated with decreased spontaneous immune responses to a model antigen. To our knowledge, this is the first evidence in cancer that systemic MDSC's can arise directly from normal monocytes that have undergone intratumoral immunosuppressive education.

Immunocompetent murine models for the study of glioblastoma immunotherapy

Glioblastoma remains a lethal diagnosis with a 5-year survival rate of less than 10%. (NEJM 352:987-96, 2005) Although immunotherapy-based approaches are capable of inducing detectable immune responses against tumor-specific antigens, improvements in clinical outcomes are modest, in no small part due to tumor-induced immunosuppressive mechanisms that promote immune escape and immuno-resistance. Immunotherapeutic strategies aimed at bolstering the immune response while neutralizing immunosuppression will play a critical role in improving treatment outcomes for glioblastoma patients. In vivo murine models of glioma provide an invaluable resource to achieving that end, and their use is an essential part of the preclinical workup for novel therapeutics that need to be tested in animal models prior to testing experimental therapies in patients. In this article, we review five contemporary immunocompetent mouse models, GL261 (C57BL/6), GL26 (C57BL/6) CT-2A (C57BL/6), SMA-560 (VM/Dk), and 4C8 (B6D2F1), each of which offer a suitable platform for testing novel immunotherapeutic approaches.

Cancer immunotherapy using virally transduced dendritic cells: animal studies and human clinical trials

The immune system uses a process known as 'immunosurveillance' to help prevent the outgrowth of tumors. In cancer immunotherapy, a major goal is for immunity against tumor-associated antigens to be generated or strengthened in patients. To achieve this goal, several approaches have been tested, including the use of highly potent antigen-presenting cells called dendritic cells (DCs), which can activate T cells efficiently. Presentation of peptides derived from tumor antigens on the surface of DCs can stimulate strong antitumor immunity. Using recombinant viral vectors encoding tumor-associated antigens, DCs can be engineered efficiently to express sustained levels of tumor-antigen peptides. This review discusses the effectiveness of virally transduced DCs in treating tumors and generating antigen-specific T-cell responses. It covers mouse and nonhuman primate studies, preclinical in vitro human cell experiments and clinical trials.

Immune modulation of the tumor microenvironment for enhancing cancer immunotherapy

There is much promise in the use of immunotherapy for the treatment of cancer. Approaches such as those using antibodies or adoptive cell transfer can mediate complete tumor regression in a proportion of patients. However, the tumor microenvironment can inhibit immune responses leading to ineffective or suboptimal responses of tumors to immunotherapy in the majority of cases. As our knowledge of the tumor microenvironment increases, many strategies are emerging for changing the immunosuppressive nature of the tumor toward a microenvironment able to support immunity. These strategies aim to enhance the ability of immunotherapies to initiate effective immune responses able to destroy tumors. In this article, we review approaches that use immunomodulators specifically to modify the tumor microenvironment, and their use in combination with other immune-based strategies for cancer therapy.

Oncolytic Newcastle Disease Virus as Cutting Edge between Tumor and Host

Oncolytic viruses (OVs) replicate selectively in tumor cells and exert anti-tumor cytotoxic activity. Among them, Newcastle Disease Virus (NDV), a bird RNA virus of the paramyxovirus family, appears outstanding. Its anti-tumor effect is based on: (i) oncolytic activity and (ii) immunostimulation. Together these activities facilitate the induction of post-oncolytic adaptive immunity. We will present milestones during the last 60 years of clinical evaluation of this virus. Two main strategies of clinical application were followed using the virus (i) as a virotherapeutic agent, which is applied systemically or (ii) as an immunostimulatory agent combined with tumor cells for vaccination of cancer patients. More recently, a third strategy evolved. It combines the strategies (i) and (ii) and includes also dendritic cells (DCs). The first step involves systemic application of NDV to condition the patient. The second step involves intradermal application of a special DC vaccine pulsed with viral oncolysate. This strategy, called NDV/DC, combines anti-cancer activity (oncolytic virotherapy) and immune-stimulatory properties (oncolytic immunotherapy) with the high potential of DCs (DC therapy) to prime naive T cells. The aim of such treatment is to first prepare the cancer-bearing host for immunocompetence and then to instruct the patient's immune system with information about tumor-associated antigens (TAAs) of its own tumor together with danger signals derived from virus infection. This multimodal concept should optimize the generation of strong polyclonal T cell reactivity targeted against the patient's TAAs and lead to the establishment of a long-lasting memory T cell repertoire.

Integration of epidemiology, immunobiology, and translational research for brain tumors

We recently identified a pivotal role for the host type I interferon (IFN) pathway in immunosurveillance against de novo mouse glioma development, especially through the regulation of immature myeloid cells (IMCs) in the glioma microenvironment. The present paper summarizes our published work in a number of areas. We have identified single-nucleotide polymorphisms (SNPs) in human IFN genes that dictate altered prognosis of patients with glioma. One of these SNPs (rs12553612) is located in the promoter of IFNA8 and influences its activity. Conversely, recent epidemiologic data show that chronic use of nonsteroidal anti-inflammatory drugs lowers the risk of glioma. We translated these findings back to our de novo glioma model and found that cyclooxygenase-2 inhibition enhances antiglioma immunosurveillance by reducing glioma-associated IMCs. Taken together, these findings suggest that alterations in myeloid cell function condition the brain for glioma development. Finally, in preliminary work, we have begun applying novel immunotherapeutic approaches to patients with low-grade glioma with the aim of preventing malignant transformation. Future research will hopefully better integrate epidemiological, immunobiological, and translational techniques to develop novel, preventive approaches for malignant gliomas.

Combined Tbet and IL12 gene therapy elicits and recruits superior antitumor immunity in vivo

We have recently shown that intratumor (i.t.) injection of syngenic dendritic cells (DC) engineered to express the transcription factor Tbet (TBX21) promotes protective type-1 T cell-mediated immunity via a mechanism that is largely interleukin (IL)-12p70-independent. Since IL-12 is a classical promoter of type-1 immunity, the current study was undertaken to determine whether gene therapy using combined Tbet and IL-12 complementary DNA (cDNA) would yield improved antitumor efficacy based on the complementary/synergistic action of these biologic modifiers. Mice bearing established subcutaneous (s.c.) tumors injected with DC concomitantly expressing ectopic Tbet and IL12 (i.e., DC.Tbet/IL12) displayed superior (i) rates of tumor rejection and extended overall survival, (ii) cross-priming of Tc1 reactive against antigens expressed within the tumor microenvironment, and (iii) infiltration of CD8(+) T cells into treated tumors in association with elevated locoregional production of CXCR3 ligand chemokines. In established bilateral tumor models, i.t. delivery of DC.Tbet/IL12 into a single lesion led to slowed growth or regression at both tumor sites. Furthermore, DC.Tbet/IL12 pulsed with tumor antigen-derived peptides and injected as a therapy distal to the tumor site prevented tumor growth and activated robust antigen-specific Tc1 responses. These data support the translation use of combined Tbet and IL-12p70 gene therapy in the cancer setting.

High FOXP3+ regulatory T-cell density in the sentinel lymph node is associated with downstream non-sentinel lymph-node metastasis in gastric cancer

Background:

We aimed to evaluate the immunologic nature of sentinel lymph nodes (SLNs) in gastric cancer patients and to determine whether it can predict non-SLN metastasis.

Methods:

Sentinel lymph node samples were collected from 64 gastric carcinoma patients who had undergone gastrectomy with SLN biopsy. One representative SLN sample was selected from each patient and was subjected to immunostaining for CD8, CD57, FOXP3, and DC-LAMP. The numbers of marker-positive cells in each sample were counted. The relationships between various immune cell densities and clinicopathologic parameters or metastasis status of SLNs and non-SLNs were sought.

Results:

High FOXP3+ Treg density of the SLN was found to be significantly associated with the presence of metastasis in either SLNs or non-SLNs. DC-LAMP+ cell density of the SLN was the highest at the isolated tumours cell level, and this decreased along with an increase in tumour metastasis in either SLNs or non-SLNs. Univariate and multivariate logistic regression models revealed that high FOXP3+ Treg density of the SLN was an independently significant predictor of non-SLN metastasis.

Conclusions:

This study is the first to indicate an important role of SLNs in metastatic dissemination of gastric cancer. Our findings suggest that Tregs could be a new therapeutic target for regulating the metastasis of gastric cancer.

Engineering dendritic cells to enhance cancer immunotherapy

Cancer immunotherapy aims to establish immune-mediated control of tumor growth by priming T-cell responses to target tumor-associated antigens. Three signals are required for T-cell activation: (i) presentation of cognate antigen in self MHC molecules; (ii) costimulation by membrane-bound receptor-ligand pairs; and (iii) soluble factors to direct polarization of the ensuing immune response. The ability of dendritic cells (DCs) to provide all three signals required for T-cell activation makes them an ideal cancer vaccine platform. Several strategies have been developed to enhance and control antigen presentation, costimulation, and cytokine production. In this review, we discuss progress toward developing DC-based cancer vaccines by genetic modification using RNA, DNA, and recombinant viruses. Furthermore, the ability of DC-based vaccines to activate natural killer (NK) and B-cells, and the impact of gene modification strategies on these populations is described. Clinical trials using gene-modified DCs have shown modest results, therefore, further considerations for DC manipulation to enhance their clinical efficacy are also discussed.

Experimental immunotherapy for malignant glioma: lessons from two decades of research in the GL261 model

Nearly twenty years of experimental immunotherapy for malignant glioma yielded important insights in the mechanisms governing glioma immunology. Still considered promising, it is clear that immunotherapy does not on its own represent the magic bullet in glioma therapy. In this review, we summarize the major immunotherapeutic achievements in the mouse GL261 glioma model, which has emerged as the gold standard syngeneic model for experimental glioma therapy. Gene therapy, monoclonal antibody treatment, cytokine therapy, cell transfer strategies and dendritic cell therapy were hereby considered. Apart from the considerable progress made in understanding glioma immunology in this model, we also addressed its most pertinent issues and shortcomings. Despite these, the GL261 model will remain indispensable in glioma research since it is a fast, highly reproducible and easy-to-establish model system.

Designing the optimal vaccine: the importance of cytokines and dendritic cells

Many vaccines existing today provide strong protection against a wide variety of infectious organisms, and these consist of either live attenuated or inactivated microorganisms. Most of these vaccines were developed empirically and there has not been a clear understanding of the immunological principles that contribute to this success. Recent advances in systems biology are being applied to the study of vaccines in order to determine which immunological parameters are the best predictors of success. New approaches to vaccine development include the identification of peptide epitopes and the manipulation of the immune response to generate the most appropriate response. Vaccines are being developed to prevent and/or treat such conditions as cancer and autoimmunity in addition to infectious diseases. Vaccines targeting this diverse group of diseases may need to elicit very different types of immune responses. Recent advances in our understanding of the functions of dendritic cells (DC) and cytokines in orchestrating qualitatively different immune responses has allowed the design of vaccines that can elicit immune responses appropriate for cancer, autoimmunity or infectious organisms. This review will focus on recent advances in the ways DC and cytokines can be used to develop the most appropriate and effective vaccines.

Intra-tumoral dendritic cells increase efficacy of peripheral vaccination by modulation of glioma microenvironment

Pilot data showed that adding intratumoral (IT) injection of dendritic cells (DCs) prolongs survival of patients affected by glioblastoma multiforme (GBM) treated by subcutaneous (SC) delivery of DCs. Using a murine model resembling GBM, we investigated the immunological mechanisms underlying this effect. C57BL6/N mice received brain injections of GL261 glioma cells. Seven days later, mice were treated by 3 SC injections of DCs with or without 1 IT injection of DCs. DC maturation, induced by pulsing with GL261 lysates, was necessary to develop effective immune responses. IT injection of pulsed (pDC), but not unpulsed DCs (uDC), increased significantly the survival, either per se or in combination with SC-pDC (P < .001 vs controls). Mice treated by IT-pDC plus SC-pDC survived longer than mice treated by SC-pDC only (P = .03). Injected pDC were detectable in tumor parenchyma, but not in cervical lymph nodes. In gliomas injected with IT-pDC, CD8+ cells were significantly more abundant and Foxp3+ cells were significantly less abundant than in other groups. Using real-time polymerase chain reaction, we also found enhanced expression of IFN-gamma and TNF-alpha and decreased expression of transforming growth factor-beta (TGF-beta) and Foxp3 in mice treated with SC-pDC and IT-pDC. In vitro, pDC produced more TNF-alpha than uDC: addition of TNF-alpha to the medium decreased the proliferation of glioma cells. Overall, the results suggest that IT-pDC potentiates the anti-tumor immune response elicited by SC-pDC by pro-immune modulation of cytokines in the tumor microenvironment, decrease of Treg cells, and direct inhibition of tumor proliferation by TNF-alpha.

Magnetic resonance imaging-guided adoptive cellular immunotherapy of central nervous system tumors with a T1 contrast agent

Dendritic cells (DCs) are the most effective antigen-presenting cells (APCs) and are used in a variety of immunotherapeutic approaches. Adoptive cellular immunotherapy (ACI) of cancer using DCs has attracted much interest due to their capacity to promote immunity in prophylactic and therapeutic protocols. As one approach, DCs are injected into patients or tumor-bearing animals, to trigger specific antitumor immunity. In that framework, several approaches to DC delivery have been reported, including direct intratumoral injection; this has yielded positive but variable results. The underlying reasons for this have not been fully determined, but major hypotheses include technical difficulties in delivering cells into tumors and tumor-mediated immunosuppression. Image-guided ACI offers the potential to establish that DCs are efficiently delivered to the tumor site, which might eliminate some of the variability. Therefore, we developed highly sensitive methods for monitoring the injection or trafficking of DCs into tumors using a clinically approved formulation of a gadolinium-based magnetic resonance imaging (MRI) contrast agent, Gd(III)-HP-DO3A (ProHance). We determined the labeling efficiency of DCs with this formulation; that labeling DCs with this agent did not inhibit expression of surface markers important for antigen presentation and activation of naive T cells; that their capacity to interact with natural killer (NK) cells was not reduced; and that their migration was not diminished. Further, we determined that ProHance-labeled DCs can be effectively imaged in vivo in established central nervous system tumors.

Immunotherapy of diffuse gliomas: biological background, current status and future developments

Despite aggressive multimodal treatment approaches, the prognosis for patients with diffuse gliomas remains disappointing. Glioma cells often extensively infiltrate in the surrounding brain parenchyma, a phenomenon that helps them to escape surgical removal, radiation exposure and chemotherapy. Moreover, conventional therapy is often associated with considerable local and systemic side effects. Therefore, the development of novel therapeutic approaches is essential to improve the outcome of these patients. Immunotherapy offers the opportunity to specifically target residual radio-and chemoresistant tumor cells without damaging healthy neighboring brain tissue. Significant progress has been made in recent years both in understanding the mechanisms of immune regulation in the central nervous system (CNS) as well as tumor-induced and host-mediated immunosuppression elicited by gliomas. In this review, after discussing the special requirements needed for the initiation and control of immune responses in the CNS, we focus on immunological phenomena observed in glioma patients, discuss different immunological approaches to attack glioma-associated target structures and touch on further strategies to improve the efficacy of immunotherapy of gliomas.

Dendritic cell therapy of high-grade gliomas

The prognosis of patients with malignant glioma is poor in spite of multimodal treatment approaches consisting of neurosurgery, radiochemotherapy and maintenance chemotherapy. Among innovative treatment strategies like targeted therapy, antiangiogenesis and gene therapy approaches, immunotherapy emerges as a meaningful and feasible treatment approach for inducing long-term survival in at least a subpopulation of these patients. Setting up immunotherapy for an inherent immunosuppressive tumor located in an immune-privileged environment requires integration of a lot of scientific input and knowledge of both tumor immunology and neuro-oncology. The field of immunotherapy is moving into the direction of active specific immunotherapy using autologous dendritic cells (DCs) as vehicle for immunization. In the translational research program of the authors, the whole cascade from bench to bed to bench of active specific immunotherapy for malignant glioma is covered, including proof of principle experiments to demonstrate immunogenicity of patient-derived mature DCs loaded with autologous tumor lysate, preclinical in vivo experiments in a murine orthotopic glioma model, early phase I/II clinical trials for relapsing patients, a phase II trial for patients with newly diagnosed glioblastoma (GBM) for whom immunotherapy is integrated in the current multimodal treatment, and laboratory analyses of patient samples. The strategies and results of this program are discussed in the light of the internationally available scientific literature in this fast-moving field of basic science and translational clinical research.

Brain tumor immunotherapy with type-1 polarizing strategies

Although the safety of vaccine approaches for central nervous system (CNS) malignancies has been established in early phase clinical trials, the success of a vaccine strategy will depend critically on the ability of effector T cells to home in to CNS tumors and durably exert antitumor effects. Based on our recent studies, efficient CNS tumor homing is a characteristic of cytotoxic T lymphocytes (CTLs) with a type 1 phenotype (Tc1), and this appears to be related to the Tc1 response to the type 1 CXC chemokine ligand (CXCL) 10 [also known as interferon (IFN)-inducible protein (IP)-10] and expression of an integrin receptor very late antigen (VLA)-4 on Tc1. In addition, we have previously shown that direct intratumoral delivery of dendritic cells (DCs) ex vivo engineered to secrete IFN-alpha further enhances Tc1 homing via upregulation of CXCL10/IP-10 in the tumor microenvironment. As a means to induce IFN-alpha and CXCL10/IP-10 in the CNS tumor microenvironment in a clinically feasible manner, we used administration of polyinosinic-polycytidylic acid stabilized by lysine and carboxymethylcellulose (poly-ICLC), a ligand for toll-like receptor 3 and melanoma differentiation-associated gene 5 (MDA5) in combination with vaccinations targeting CTL epitopes derived from glioma-associated antigens (GAAs). The combination of subcutaneous vaccination and i.m. poly-ICLC administration remarkably promoted systemic induction of antigen GAA-specific Tc1s expressing VLA-4 in the CNS tumors and improved the survival of tumor-bearing mice in the absence of detectable autoimmunity. Based on these data, we have implemented a phase I/II vaccination study using type 1 polarizing DCs loaded with GAA peptides in combination with poly-ICLC in patients with recurrent malignant glioma.

Recent Advances of Dendritic Cells (DCs)-Based Immunotherapy for Malignant Gliomas

Immunotherapy is a new light of hope for the treatment of malignant gliomas. The brain is no longer believed to be an immunologically privileged organ. The major advantage of immunotherapy is the tumor-specific cytotoxic effect on the tumor cells with minimal side effects. Autologous dendritic cells (DCs)-based immunotherapy is a promising and feasible method. DCs are the most potent antigen-presenting cells (APCs). DCs prime T lymphocytes by epitopic major histocompatibility (MHC) class I and II for CD8+ cytotoxic T lymphocytes (CTLs) and CD4+ T helper cells, respectively. From the tissue specimen examination after DCs-based immunotherapy, CD8+ CTLs have replaced T regulatory cells (Tregs) as the major dominant tissue infiltrating lymphocytes (TILs). CD8+ CTLs play a key role in the tumor response, which may also be effective against cancer stem cells. DCs themselves also produce many cytokines including interferon-γ and interleukin (IL-2) to kill the tumor cells. From the preliminary better outcomes in the literature for malignant gliomas, DC-based immunotherapy may improve tumor response by increasing the survival rate and time. It is recommended that DC-based immunotherapy is applied as soon as possible with conjunctive radiotherapy and chemotherapy. Malignant gliomas have heterogeneity of tissue-associated antigens (TAAs). To find universal common antigens through different kinds of tumor culture may be the essential issue for tumor vaccine development in the future.

The antitumor and immunoadjuvant effects of IFN-alpha in combination with recombinant poxvirus vaccines

PURPOSE

IFN-alpha is a pleiotropic cytokine possessing immunomodulatory properties that may improve the efficacy of therapeutic cancer vaccines. The aim of this study was to evaluate the effectiveness and compatibility of combining recombinant IFN-alpha with poxvirus vaccines targeting the human carcinoembryonic antigen (CEA) in murine models of colorectal and pancreatic adenocarcinomas, where CEA is a self-antigen.

EXPERIMENTAL DESIGN

The phenotypic and functional effects of IFN-alpha were evaluated in the draining inguinal lymph nodes of tumor-free mice. We studied the effect of the site of IFN-alpha administration (local versus distal) on antigen-specific immune responses to poxvirus vaccination. Mechanistic studies were conducted to assess the efficacy of IFN-alpha and CEA-directed poxvirus vaccines in tumor-bearing CEA transgenic mice.

RESULTS

We identified a dose and schedule of IFN-alpha that induced a locoregional expansion of the draining inguinal lymph nodes and improved cellular cytotoxicity (natural killer and CD8(+)) and antigen presentation. Suppression of the vaccinia virus was avoided by administering IFN-alpha distal to the site of vaccination. The combination of IFN-alpha and vaccine inhibited tumor growth, improved survival, and elicited CEA-specific CTL responses in mice with CEA(+) adenocarcinomas. In mice with pancreatic tumors, IFN-alpha slowed tumor growth, induced CTL activity, and increased CD8(+) tumor-infiltrating lymphocytes.

CONCLUSIONS

These data suggest that IFN-alpha can be used as a biological response modifier with antigen-directed poxvirus vaccines to yield significant therapeutic antitumor immune responses. This study provides the rationale and mechanistic insights to support a clinical trial of this immunotherapeutic strategy in patients with CEA-expressing carcinomas.

Effective immunotherapy against murine gliomas using type 1 polarizing dendritic cells--significant roles of CXCL10

In an attempt to develop effective vaccines against central nervous system (CNS) tumors, we evaluated the ability of vaccines with standard dendritic cells (DC) versus type 1 polarizing DCs (DC1) to induce glioma-specific type 1 CTLs with CNS tumor-relevant homing properties and the mechanism of their action. C57BL/6 mouse-derived bone marrow cells were cultured with mouse granulocyte/macrophage colony-stimulating factor (GM-CSF) for 6 days, and CD11c(+) cells were subsequently cultured with GM-CSF, rmIFN-gamma, rmIFN-alpha, rmIL-4, and polyinosinic-polycytidylic acid stabilized by lysine and carboxymethylcellulose for 24 hours to generate DC1s. In analogy to their human counterparts, mouse DC1s exhibited surface marker profiles of mature DCs and produced high levels of IL-12 and CXCL10. Importantly for their application as cancer vaccines, such DC1s stably retained their type 1 phenotype even when exposed to type 2-promoting or regulatory T cell (Treg)-promoting environments. Consistently, mouse DC1s induced antigen-specific type 1 CTLs more efficiently than nonpolarized DCs in vitro. DC1s given s.c. migrated into draining lymph nodes, induced antigen-specific CTLs, and suppressed Treg accumulation. In addition, s.c. immunization with DC1s loaded with glioma-associated antigen (GAA)-derived CTL epitope peptides prolonged the survival of CNS GL261 glioma-bearing mice, which was associated with efficient CNS glioma homing of antigen-specific CTLs. Intratumoral injections of GAA peptide-loaded DC1s further enhanced the anti-CNS glioma effects of DC1-based s.c. immunization. Interestingly, the antitumor functions were abrogated with CXCL10(-/-) mouse-derived DC1s. Collectively, these findings show the anti-CNS glioma effects of DC1-based therapy and a novel role of CXCL10 in the immunologic and therapeutic activity of DC-based cancer vaccines.

Immunotherapeutic approaches for glioma

The development of effective immunotherapy strategies for glioma requires adequate understanding of the unique immunological microenvironment in the central nervous system (CNS) and CNS tumors. Although the CNS is often considered to be an immunologically privileged site and poses unique challenges for the delivery of effector cells and molecules, recent advances in technology and discoveries in CNS immunology suggest novel mechanisms that may significantly improve the efficacy of immunotherapy against gliomas. In this review, we first summarize recent advances in the CNS and CNS tumor immunology. We address factors that may promote immune escape of gliomas. We also review advances in passive and active immunotherapy strategies for glioma, with an emphasis on lessons learned from recent early-phase clinical trials. We also discuss novel immunotherapy strategies that have been recently tested in non-CNS tumors and show great potential for application to gliomas. Finally, we discuss how each of these promising strategies can be combined to achieve clinical benefit for patients with gliomas.

Harnessing T-Cell Immunity to Target Brain Tumors

T-cell mediated immunotherapy is a conceptually attractive treatment option to envisage for glioma, since T lymphocytes can actively seek out neoplastic cells in the brain, and they have the potential to safely and specifically eliminate tumor. Some antigenic targets on glioma cells are already defined, and we can be optimistic that more will be discovered from progress in T-cell epitope identification and gene expression profiling of brain tumors. In parallel, advances in immunology (regional immunology, neuroimmunology, tumor immunology) now equip us to build upon the results from current immunotherapy trials in which the safety and feasibility of brain tumor immunotherapy have already been confirmed. We can now look to the next phase of immunotherapy, in which we must harness the most promising basic science advances and existing clinical expertise, and apply these to randomized clinical trials to determine the real clinical impact and applicability of these approaches for treating patients with currently incurable malignant brain tumors.

Alpha-fetoprotein and other tumour-associated antigens for immunotherapy of hepatocellular cancer

BACKGROUND

Hepatocellular carcinoma (HCC) is a leading cause of cancer death, with few treatment options for advanced disease.

OBJECTIVES

Here, we review the aetiology of HCC and focus on recent data on tumour-associated antigens (TAA) for HCC, their functions and potential use as immunological targets for immune-based therapy for HCC. In addition, we examine some aspects of antigen presentation within the liver.

RESULTS/CONCLUSIONS

alpha-Fetoprotein (AFP) has been investigated for many years as a TAA, and has been tested in recent clinical trials. More recently, additional TAA have been identified and new therapeutic approaches have been investigated which may be testable clinically in this difficult disease setting.

Inhibition of STAT3 promotes the efficacy of adoptive transfer therapy using type-1 CTLs by modulation of the immunological microenvironment in a murine intracranial glioma

A variety of cancers, including malignant gliomas, show aberrant activation of STAT3, which plays a pivotal role in negative regulation of antitumor immunity. We hypothesized that inhibition of STAT3 signals would improve the efficacy of T cell adoptive transfer therapy by reversal of STAT3-induced immunosuppression in a murine GL261 intracranial glioma model. In vitro treatment of GL261 cells with JSI-124, a STAT3 inhibitor, reversed highly phosphorylated status of STAT3. Systemic i.p. administration of JSI-124 in glioma-bearing immunocompetent mice, but not athymic mice, resulted in prolonged survival, suggesting a role of adaptive immunity in the antitumor effect. Furthermore, JSI-124 promoted maturation of tumor-infiltrating CD11c(+) dendritic cells and activation of tumor-conditioned cytotoxic T cells, enhanced dendritic cells and GL261 production of CXCL-10, a critical chemokine for attraction of Tc1 cells. When i.p. JSI-124 administration was combined with i.v. transfer of Pmel-I mouse-derived type-1 CTLs (Tc1), glioma-bearing mice exhibited prolonged survival compared with i.p. JSI-124 or i.v. Tc1 therapy alone. Flow cytometric analyses of brain infiltrating lymphocytes revealed that JSI-124-treatment enhanced the tumor-homing of i.v. transferred Tc1 cells in a CXCL-10-dependent fashion. Systemic JSI-124 administration also up-regulated serum IL-15 levels, and promoted the persistence of transferred Tc1 in the host. These data suggest that systemic inhibition of STAT3 signaling can reverse the suppressive immunological environment of intracranial tumor bearing mice both systemically and locally, thereby promoting the efficacy of adoptive transfer therapy with Tc1.

Sentinel lymph node as a target of molecular diagnosis of lymphatic micrometastasis and local immunoresponse to malignant cells

The sentinel lymph node (SLN) is defined as the lymph node(s) first receiving lymphatic drainage from the site of the primary tumor. The histopathological status of SLN is one of the most significant predictors of recurrence and overall survival for most clinical stage I/II solid tumors. Recent progress in molecular techniques has demonstrated the presence of micrometastatic tumor cells in SLN. There is now a growing body of data to support the clinical relevance of SLN micrometastasis in a variety of solid tumors. Increasing the sensitivity of occult tumor cell detection in the SLN, using molecular-based analysis, should enable a more accurate understanding of the clinical significance of various patterns of micrometastatic nodal disease. The establishment of metastasis to SLN might not be simply reflected by the flow dynamics of lymphatic fluid that drains from the primary site to the SLN, and the transportation of viable cancer cells. Recent studies have demonstrated that primary tumors can actively induce lymphangiogenesis and promote SLN metastasis. Moreover chemokine receptors in tumor cells may facilitate organ-specific tumor metastasis in many human cancers and some experimental models. In contrast, recent clinical and preclinical studies regard SLN as the first lymphoid organ to respond to tumor antigenic stimulation. SLN dramatically show morphological, phenotypical and functional changes that indicate immune suppression by tumor cells. The immune suppression in SLN results in failure of prevention or eradication of tumor metastasis. The mechanism of immunomodulation remains unclear; however, several regulatory molecules produced by tumor cells and tumor-associated macrophages or lymphocytes are likely to be responsible for inducing the immune suppression in SLN. Further studies may develop a novel immunotherapy that overcomes tumor-induced immune suppression and can prevent or eradicate SLN metastasis.

Anti-tumor activity and trafficking of self, tumor-specific T cells against tumors located in the brain

It is commonly believed that T cells have difficulty reaching tumors located in the brain due to the presumed "immune privilege" of the central nervous system (CNS). Therefore, we studied the biodistribution and anti-tumor activity of adoptively transferred T cells specific for an endogenous tumor-associated antigen (TAA), gp100, expressed by tumors implanted in the brain. Mice with pre-established intracranial (i.c.) tumors underwent total body irradiation (TBI) to induce transient lymphopenia, followed by the adoptive transfer of gp100(25-33)-specific CD8+ T cells (Pmel-1). Pmel-1 cells were transduced to express the bioluminescent imaging (BLI) gene luciferase. Following adoptive transfer, recipient mice were vaccinated with hgp100(25-33) peptide-pulsed dendritic cells (hgp100(25-33)/DC) and systemic interleukin 2 (IL-2). This treatment regimen resulted in significant reduction in tumor size and extended survival. Imaging of T cell trafficking demonstrated early accumulation of transduced T cells in lymph nodes draining the hgp100(25-33)/DC vaccination sites, the spleen and the cervical lymph nodes draining the CNS tumor. Subsequently, transduced T cells accumulated in the bone marrow and brain tumor. BLI could also detect significant differences in the expansion of gp100-specific CD8+ T cells in the treatment group compared with mice that did not receive either DC vaccination or IL-2. These differences in BLI correlated with the differences seen both in survival and tumor infiltrating lymphocytes (TIL). These studies demonstrate that peripheral tolerance to endogenous TAA can be overcome to treat tumors in the brain and suggest a novel trafficking paradigm for the homing of tumor-specific T cells that target CNS tumors.

Flt3L and TK gene therapy eradicate multifocal glioma in a syngeneic glioblastoma model

The disseminated characteristics of human glioblastoma multiforme (GBM) make it a particularly difficult tumor to treat with long-term efficacy. Most preclinical models of GBM involve treatment of a single tumor mass. For therapeutic outcomes to translate from the preclinical to the clinical setting, induction of an antitumor response capable of eliminating multifocal disease is essential. We tested the hypothesis that expression of Flt3L (human soluble FMS-like tyrosine kinase 3 ligand) and TK (herpes simplex virus type 1-thymidine kinase) within brain gliomas would mediate regression of the primary, treated tumor mass and a secondary, untreated tumor growing at a distant site from the primary tumor and the site of therapeutic vector injection. In both the single-GBM and multifocal-GBM models used, all saline-treated control animals succumbed to tumors by day 22. Around 70% of the animals bearing a single GBM mass treated with an adenovirus expressing Flt3L (AdFlt3L) and an adenovirus expressing TK (AdTK + GCV) survived long term. Approximately 50% of animals bearing a large primary GBM that were implanted with a second GBM in the contralateral hemisphere at the same time the primary tumors were being treated with AdFlt3L and AdTK also survived long term. A second multifocal GBM model, in which bilateral GBMs were implanted simultaneously and only the right tumor mass was treated with AdFlt3L and AdTK, also demonstrated long-term survival. While no significant difference in survival was found between unifocal and multifocal GBM-bearing animals treated with AdFlt3L and AdTK, both treatments were statistically different from the saline-treated control group (p < 0.05). Our results demonstrate that combination therapy with AdFlt3L and AdTK can eradicate multifocal brain tumor disease in a syngeneic, intracranial GBM model.

Transposon-based interferon gamma gene transfer overcomes limitations of episomal plasmid for immunogene therapy of glioblastoma

Despite improvements in gene delivery technology, transient expression of plasmid DNA has limited the efficacy of nonviral vectors applied to cancer gene therapy. We previously developed plasmid DNA vectors capable of transgene integration and long-term expression in human glioblastoma cells by utilizing the Sleeping Beauty (SB) transposable element. In this study, we compared the efficacy of interferon gamma (IFN-gamma) immunogene therapy using episomal or SB vectors in a syngeneic GL261 glioma model. Gene delivery was achieved by intratumoral convection-enhanced delivery of DNA/polyethylenimine complexes. Only mice treated with SB transposase-encoding DNA to facilitate chromosomal integration exhibited a significant increase in survival (P<0.05). SB-mediated intratumoral gene transfer caused sustained IFN-gamma expression assessed by reverse transcription-polymerase chain reaction, of both vector-derived and endogenous IFN-gamma, whereas expression following episomal plasmid gene transfer was undetectable within 2 weeks. Median survival was enhanced further when SB-mediated IFN-gamma gene transfer was combined with CpG oligodeoxynucleotides as adjuvant therapy. Prolonged survival positively correlated with tumor regression measured by in vivo bioluminescent imaging, and enhanced T-cell activation revealed by the ELISPOT assay. SB appears to improve the efficacy of cytokine gene therapy using nonviral vectors by enhancing the duration of transgene expression.

Dendritic cell-based active specific immunotherapy for malignant glioma

Immunotherapy is an appealing therapeutic modality for malignant gliomas because of its potential to selectively target residual tumor cells that have invaded the normal brain. Most immunotherapeutic studies are designed to exploit the capacity of dendritic cells for inducing cell-mediated effects as well as immune memory responses for destroying residual tumor cells and preventing recurrence. Although initial clinical studies on dendritic cell-based immunotherapy resulted in very limited success, they have prompted many new studies on exploring strategies to induce a more robust antitumor immune response by using novel adjuvants for maturation and activation of dendritic cells. More studies have focused on the mechanisms of immune suppression by tumor cells and the role of regulatory T cells in tumor growth and progression. In this article, the authors review the evolution of dendritic cell-based immunotherapeutic strategies for adjuvant treatment of malignant gliomas. The authors also discuss how new knowledge on tumor-intrinsic mechanisms of tolerance induction and immunosuppression are likely to shape the future of immunotherapy for high-grade gliomas.

Toll like receptor-3 ligand poly-ICLC promotes the efficacy of peripheral vaccinations with tumor antigen-derived peptide epitopes in murine CNS tumor models

Background

Toll-like receptor (TLR)3 ligands serve as natural inducers of pro-inflammatory cytokines capable of promoting Type-1 adaptive immunity, and TLR3 is abundantly expressed by cells within the central nervous system (CNS). To improve the efficacy of vaccine strategies directed against CNS tumors, we evaluated whether administration of a TLR3 ligand, polyinosinic-polycytidylic (poly-IC) stabilized with poly-lysine and carboxymethylcellulose (poly-ICLC) would enhance the anti-CNS tumor effectiveness of tumor peptide-based vaccinations.

Methods

C57BL/6 mice bearing syngeneic CNS GL261 glioma or M05 melanoma received subcutaneous (s.c.) vaccinations with synthetic peptides encoding CTL epitopes- mEphA2 (671–679), hgp100 (25–33) and mTRP-2 (180–188) for GL261, or ovalbumin (OVA: 257–264) for M05. The mice also received intramuscular (i.m.) injections with poly-ICLC.

Results

The combination of subcutaneous (s.c.) peptide-based vaccination and i.m. poly-ICLC administration promoted systemic induction of antigen (Ag)-specific Type-1 CTLs expressing very late activation antigen (VLA)-4, which confers efficient CNS-tumor homing of vaccine-induced CTLs based on experiments with monoclonal antibody (mAb)-mediated blockade of VLA-4. In addition, the combination treatment allowed expression of IFN-γ by CNS tumor-infiltrating CTLs, and improved the survival of tumor bearing mice in the absence of detectable autoimmunity.

Conclusion

These data suggest that poly-ICLC, which has been previously evaluated in clinical trials, can be effectively combined with tumor Ag-specific vaccine strategies, thereby providing a greater index of therapeutic efficacy.

Cellules dendritiques et gliomes : un espoir en immunothérapie ?

Immunotherapy has been explored for several decades to try to improve the prognosis of gliomas, but until recently no therapeutic benefit has been achieved. The discovery of dendritic cells, the most potent professional antigen presenting cells to initiate specific immune response, and the possibility of producing them ex vivo gave rise to new protocols of active immunotherapy. In oncology, promising experimental and clinical therapeutic results were obtained using these dendritic cells loaded with tumor antigen. Patients bearing gliomas have deficit antigen presentation making this approach rational. In several experimental glioma models, independent research teams have showed specific antitumor responses using these dendritic cells. Phase I/II clinical trials have demonstrated the feasibility and the tolerance of this immunotherapeutic approach. In neuro-oncology, the efficiency of such an approach remains to be established, similarly in oncology where positive phase III studies are missing. Nevertheless, dendritic cells comprise a complex network which is only partially understood and capable of generating either immunotolerance or immune response. Numerous parameters remain to be explored before any definitive conclusion about their utility as an anticancer weapon can be drawn. It seems however logical that immunotherapy with dendritic cells could prevent or delay tumor recurrence in patients with minor active disease. A review on glioma and dendritic cells is presented.

Tumour-induced immune modulation of sentinel lymph nodes

Sentinel lymph nodes (SLNs), being the first nodes to receive lymph from a primary tumour and the preferential site of initial tumour metastases, are intensively exposed to the bioactive products of tumour cells and other associated cells. This makes them ideal for studies of the factors that determine selective tissue susceptibility to metastases. We postulate that tumour-induced immune modulation of SLNs facilitates lymph-node metastases by inhibiting the generation of tumour-specific cytotoxic T cells that are active against tumour cells of primary and metastatic melanomas. Immune modulation of the lymph nodes can be reversed by granulocyte/macrophage colony-stimulating factor (GM-CSF), a finding that has implications for the future therapy of lymph-node metastases.

Adoptive transfer of type 1 CTL mediates effective anti-central nervous system tumor response: critical roles of IFN-inducible protein-10

The development of effective immunotherapeutic strategies for central nervous system (CNS) tumors requires a firm understanding of factors regulating the trafficking of tumor antigen-specific CTLs into CNS tumor lesions. Using C57BL/6 mice bearing intracranial (i.c.) ovalbumin-transfected melanoma (M05), we evaluated the efficacy and tumor homing of i.v. transferred type 1 or 2 CTLs (Tc1 or Tc2, respectively) prepared from ovalbumin-specific T-cell receptor-transgenic OT-1 mice. We also tested our hypothesis that intratumoral (i.t.) delivery of dendritic cells that had been transduced with IFN-alpha cDNA (DC-IFN-alpha) would enhance the tumor-homing and antitumor effectiveness of adoptively transferred Tc1 via induction of an IFN-gamma-inducible protein 10 (IP-10). In vitro, DC-IFN-alpha induced IP-10 production by M05 and enhanced the cytolytic activity of Tc1. In vivo, i.v. transferred Tc1 trafficked efficiently into i.c. M05 and mediated antitumor responses more effectively than Tc2, and their effect was IP-10 dependent. I.t. injections of DC-IFN-alpha remarkably enhanced the tumor homing, therapeutic efficacy, and in situ IFN-gamma production of i.v. delivered Tc1, resulting in the long-term survival and persistence of systemic ovalbumin-specific immunity. These data suggest that Tc1-based adoptive transfer therapy may represent an effective modality for CNS tumors, particularly when combined with strategies that promote a type 1 polarized tumor microenvironment.