Adoptive immunotherapy in patients with recurrent malignant glioma: preliminary results of using autologous whole-tumor vaccine plus granulocyte-macrophage colony–stimulating factor and adoptive transfer of anti-CD3–activated lymphocytes

Glioblastoma vaccines: past, present, and opportunities

Glioblastoma (GBM) is one of the most lethal central nervous systems (CNS) tumours in adults. As supplements to standard of care (SOC), various immunotherapies improve the therapeutic effect in other cancers. Among them, tumour vaccines can serve as complementary monotherapy or boost the clinical efficacy with other immunotherapies, such as immune checkpoint blockade (ICB) and chimeric antigen receptor T cells (CAR-T) therapy. Previous studies in GBM therapeutic vaccines have suggested that few neoantigens could be targeted in GBM due to low mutation burden, and single-peptide therapeutic vaccination had limited efficacy in tumour control as monotherapy. Combining diverse antigens, including neoantigens, tumour-associated antigens (TAAs), and pathogen-derived antigens, and optimizing vaccine design or vaccination strategy may help with clinical efficacy improvement. In this review, we discussed current GBM therapeutic vaccine platforms, evaluated and potential antigenic targets, current challenges, and perspective opportunities for efficacy improvement.

Therapeutic cell-based vaccines for glioblastoma multiforme

Glioblastoma multiforme (GBM), a highly aggressive tumor, poses significant challenges in achieving successful treatment outcomes. Conventional therapeutic modalities including surgery, radiation, and chemotherapy have demonstrated limited efficacy, primarily attributed to the complexities associated with drug delivery to the tumor site and tumor heterogeneity. To address this critical need for innovative therapies, the potential of cancer vaccines utilizing tumor cells and dendritic cells has been explored for GBM treatment. This article provides a comprehensive review of therapeutic vaccinations employing cell-based vaccine strategies for the management of GBM. A meticulous evaluation of 45 clinical trials involving more than 1500 participants revealed that cell-based vaccinations have exhibited favorable safety profiles with minimal toxicity. Moreover, these vaccines have demonstrated modest improvements in overall survival and progression-free survival among patients. However, certain limitations still persist. Notably, there is a need for advancements in the development of potent antigens to evoke immune responses, as well as the optimization of dosage regimens. Consequently, while cell-based vaccinations show promise as a potential therapeutic approach for GBM, further research is imperative to overcome the current limitations. The ultimate objective is to surmount these obstacles and establish cell-based vaccinations as a standard therapeutic modality for GBM.

B7H3-targeting chimeric antigen receptor modification enhances antitumor effect of Vγ9Vδ2 T cells in glioblastoma

BACKGROUND

Glioblastoma (GBM) is a highly aggressive primary brain tumor with a poor prognosis. This study investigates the therapeutic potential of human Vγ9Vδ2 T cells in GBM treatment. The sensitivity of different glioma specimens to Vγ9Vδ2 T cell-mediated cytotoxicity is assessed using a patient-derived tumor cell clusters (PTCs) model.

METHODS

The study evaluates the anti-tumor effect of Vγ9Vδ2 T cells in 26 glioma cases through the PTCs model. Protein expression of BTN2A1 and BTN3A1, along with gene expression related to lipid metabolism and glioma inflammatory response pathways, is analyzed in matched tumor tissue samples. Additionally, the study explores two strategies to re-sensitize tumors in the weak anti-tumor effect (WAT) group: utilizing a BTN3A1 agonistic antibody or employing bisphosphonates to inhibit farnesyl diphosphate synthase (FPPS). Furthermore, the study investigates the efficacy of genetically engineered Vγ9Vδ2 T cells expressing Car-B7H3 in targeting diverse GBM specimens.

RESULTS

The results demonstrate that Vγ9Vδ2 T cells display a stronger anti-tumor effect (SAT) in six glioma cases, while showing a weaker effect (WAT) in twenty cases. The SAT group exhibits elevated protein expression of BTN2A1 and BTN3A1, accompanied by differential gene expression related to lipid metabolism and glioma inflammatory response pathways. Importantly, the study reveals that the WAT group GBM can enhance Vγ9Vδ2 T cell-mediated killing sensitivity by incorporating either a BTN3A1 agonistic antibody or bisphosphonates. Both approaches support TCR-BTN mediated tumor recognition, which is distinct from the conventional MHC-peptide recognition by αβ T cells. Furthermore, the study explores an alternative strategy by genetically engineering Vγ9Vδ2 T cells with Car-B7H3, and both non-engineered and Car-B7H3 Vγ9Vδ2 T cells demonstrate promising efficacy in vivo, underscoring the versatile potential of Vγ9Vδ2 T cells for GBM treatment.

CONCLUSIONS

Vγ9Vδ2 T cells demonstrate a robust anti-tumor effect in some glioma cases, while weaker in others. Elevated BTN2A1 and BTN3A1 expression correlates with improved response. WAT group tumors can be sensitized using a BTN3A1 agonistic antibody or bisphosphonates. Genetically engineered Vγ9Vδ2 T cells, i.e.,  Car-B7H3, show promising efficacy. These results together highlight the versatility of Vγ9Vδ2 T cells for GBM treatment.

A Holistic Approach to Hard-to-Treat Cancers: The Future of Immunotherapy for Glioblastoma, Triple Negative Breast Cancer, and Advanced Prostate Cancer

Immunotherapy represents an attractive avenue for cancer therapy due to its tumour specificity and relatively low frequency of adverse effects compared to other treatment modalities. Despite many advances being made in the field of cancer immunotherapy, very few immunotherapeutic treatments have been approved for difficult-to-treat solid tumours such as triple negative breast cancer (TNBC), glioblastoma multiforme (GBM), and advanced prostate cancer (PCa). The anatomical location of some of these cancers may also make them more difficult to treat. Many trials focus solely on immunotherapy and have failed to consider or manipulate, prior to the immunotherapeutic intervention, important factors such as the microbiota, which itself is directly linked to lifestyle factors, diet, stress, social support, exercise, sleep, and oral hygiene. This review summarises the most recent treatments for hard-to-treat cancers whilst factoring in the less conventional interventions which could tilt the balance of treatment in favour of success for these malignancies.

Immunotherapy and radiation for high-grade glioma: a narrative review

Glioblastoma and other high-grade gliomas (HGGs) are the most common and deadly primary brain tumors. Due to recent advances in immunotherapy and improved clinical outcomes in other disease sites, the study of immunotherapy in HGG has increased significantly. Herein, we summarize and evaluate existing evidence and ongoing clinical trials investigating the use of immunotherapy in the treatment of HGG, including therapeutic vaccination, immune checkpoint inhibition, adoptive lymphocyte transfer, and combinatorial approaches utilizing radiation and multiple modalities of immunotherapy. Special attention is given to the mechanisms by which radiation may improve immunogenicity in HGG, why this motivates the study of radiation in combination with immunotherapy, and how to determine optimal dosing and scheduling of radiation. Though larger randomized controlled trials have not consistently shown improvements in clinical outcomes, this area of research is still in its early stages and a number of important lessons can be taken away from the studies that have been completed to date. Many studies found a subset of patients who experienced durable responses, and analysis of their immune cells and tumor cells can be used to identify biomarkers that predict therapeutic response, as well as additional glioma-specific targets that can enhance therapeutic efficacy in a challenging tumor type.

Clinical implication of cellular vaccine in glioma: current advances and future prospects

Gliomas, especially glioblastomas, represent one of the most aggressive and difficult-to-treat human brain tumors. In the last few decades, clinical immunotherapy has been developed and has provided exceptional achievements in checkpoint inhibitors and vaccines for cancer treatment. Immunization with cellular vaccines has the advantage of containing specific antigens and acceptable safety to potentially improve cancer therapy. Based on T cells, dendritic cells (DC), tumor cells and natural killer cells, the safety and feasibility of cellular vaccines have been validated in clinical trials for glioma treatment. For TAA engineered T cells, therapy mainly uses chimeric antigen receptors (IL13Rα2, EGFRvIII and HER2) and DNA methylation-induced technology (CT antigen) to activate the immune response. Autologous dendritic cells/tumor antigen vaccine (ADCTA) pulsed with tumor lysate and peptides elicit antigen-specific and cytotoxic T cell responses in patients with malignant gliomas, while its pro-survival effect is biased. Vaccinations using autologous tumor cells modified with TAAs or fusion with fibroblast cells are characterized by both effective humoral and cell-mediated immunity. Even though few therapeutic effects have been observed, most of this therapy showed safety and feasibility, asking for larger cohort studies and better guidelines to optimize cellular vaccine efficiency in anti-glioma therapy.

Autologous cancer cell vaccination, adoptive T-cell transfer, and interleukin-2 administration results in long-term survival for companion dogs with osteosarcoma

Background

Osteosarcoma (OSA) in dogs is an aggressive bone tumor with frequent chemotherapy failure and translational relevance for human health.

Hypothesis/Objectives

We hypothesized that dogs with OSA could be treated safely by ex vivo activated T‐cells that were generated by autologous cancer vaccination and supported by interleukin‐2 (IL‐2) treatment with survival more than twice that reported for amputation alone.

Animals

Osteosarcoma‐bearing dogs (n = 14) were enrolled in a single‐arm prospective trial after complete staging before amputation. Four healthy dogs also were treated in a safety study.

Methods

Autologous cancer cell vaccinations were administered intradermally and dogs underwent leukapheresis. Mononuclear cell products were stimulated ex vivo with a T‐cell‐activating agent. Activated product was transfused and 5 SC IL‐2 injections were administered q48h. Dogs were monitored for metastasis by thoracic radiography every 3 months.

Results

Autologous cancer cell vaccine and activated cellular therapy (ACT) products were successfully generated. Toxicity was minimal after premedicants were instituted before ACT. With premedication, all toxicities were grade I/II. Median disease‐free interval for all dogs was 213 days. One dog developed cutaneous metastasis but then experienced spontaneous complete remission. Median survival time for all dogs was 415 days. Five dogs survived >730 days.

Conclusions and Clinical Importance

This immunotherapy protocol without cytotoxic chemotherapy is safe and tolerable. Compared to historical amputation reports, survival was notably prolonged in this group of patients. Additional prospective studies are warranted to elucidate active immunologic mechanisms and further improve disease response and survival.

Adoptive immunotherapies in neuro-oncology: classification, recent advances, and translational challenges

Background:

Adoptive immunotherapies are among the pillars of ongoing biological breakthroughs in neuro-oncology, as their potential applications are tremendously wide. The present literature review comprehensively classified adoptive immunotherapies in neuro-oncology, provides an update, and overviews the main translational challenges of this approach.

Methods:

The PubMed/MEDLINE platform, Medical Subject Heading (MeSH) database, and ClinicalTrials.gov website were the sources. The MeSH terms “Immunotherapy, Adoptive,” “Cell- and Tissue-Based Therapy,” “Tissue Engineering,” and “Cell Engineering” were combined with “Central Nervous System,” and “Brain.” “Brain tumors” and “adoptive immunotherapy” were used for a further unrestricted search. Only articles published in the last 5 years were selected and further sorted based on the best match and relevance. The search terms “Central Nervous System Tumor,” “Malignant Brain Tumor,” “Brain Cancer,” “Brain Neoplasms,” and “Brain Tumor” were used on the ClinicalTrials.gov website.

Results:

A total of 79 relevant articles and 16 trials were selected. T therapies include chimeric antigen receptor T (CAR T) cell therapy and T cell receptor (TCR) transgenic therapy. Natural killer (NK) cell-based therapies are another approach; combinations are also possible. Trials in phase 1 and 2 comprised 69% and 31% of the studies, respectively, 8 of which were concluded. CAR T cell therapy targeting epidermal growth factor receptor variant III (EGFRvIII) was demonstrated to reduce the recurrence rate of glioblastoma after standard-of-care treatment.

Conclusion:

Adoptive immunotherapies can be classified as T, NK, and NKT cell-based. CAR T cell therapy redirected against EGFRvIII has been shown to be the most promising treatment for glioblastoma. Overcoming immune tolerance and immune escape are the main translational challenges in the near future of neuro-oncology. (www.actabiomedica.it)

Assessment of the efficacy of passive cellular immunotherapy for glioma patients

To evaluate the therapeutic efficacy of passive cellular immunotherapy for glioma, a total of 979 patients were assigned to the meta-analysis. PubMed and the Cochrane Central Register of Controlled Trials were searched initially from February 2018 and updated in April 2019. The overall survival (OS) rates and Karnofsky performance status (KPS) values of patients who underwent passive cellular immunotherapy were compared to those of patients who did not undergo immunotherapy. The proportion of survival rates was also evaluated in one group of clinical trials. Pooled analysis was performed with random- or fixed-effects models. Clinical trials of lymphokine-activated killer cells, cytotoxic T lymphocytes, autologous tumor-specific T lymphocytes, chimeric antigen receptor T cells, cytokine-induced killer cells, cytomegalovirus-specific T cells, and natural killer cell therapies were selected. Results showed that treatment of glioma with passive cellular immunotherapy was associated with a significantly improved 0.5-year OS (p = 0.003) as well as improved 1-, 1.5-, and 3-year OS (p ≤ 0.05). A meta-analysis of 206 patients in one group of clinical trials with 12-month follow-up showed that the overall pooled survival rate was 37.9% (p = 0.003). Analysis of KPS values demonstrated favorable results for the immunotherapy arm (p < 0.001). Thus, the present meta-analysis showed that passive cellular immunotherapy prolongs survival and improves quality of life for glioma patients, suggesting that it has some clinical benefits.

Biohybrid Vaccines for Improved Treatment of Aggressive Melanoma with Checkpoint Inhibitor

Recent approaches in the treatment of cancer focus on involving the immune system to control the tumor growth. The administration of immunotherapies, like checkpoint inhibitors, has shown impressive results in the long term survival of patients. Cancer vaccines are being investigated as further tools to prime tumor-specific immunity. Biomaterials show potential as adjuvants in the formulation of vaccines, and biomimetic elements derived from the membrane of tumor cells may widen the range of antigens contained in the vaccine. Here, we show how mice presenting an aggressive melanoma tumor model treated twice with the complete nanovaccine formulation showed control on the tumor progression, while in a less aggressive model, the animals showed remission and control on the tumor progression, with a modification in the immunological profile of the tumor microenvironment. We also prove that co-administration of the nanovaccine together with a checkpoint inhibitor increases the efficacy of the treatment (87.5% of the animals responding, with 2 remissions) compared to the checkpoint inhibitor alone in the B16.OVA model. Our platform thereby shows potential applications as a cancer nanovaccine in combination with the standard clinical care treatment for melanoma cancers.

Anti-glioma effect of intracranial vaccination with tumor cell lysate plus flagellin in mice

The adjuvant effects of flagellin on regulation of immune response have been proved; whether flagellin could assist tumor cell lysate (TCL) to enhance anti-glioma immunity remains to be investigated. This study tests a hypothesis that therapeuticly intracranial administration with flagellin plus TCL enhances the effects of specific immunotherapy on glioma in mice. In this study, GL261 cells were transferred into C57BL/6 mice and the GL261-bearing mice were subcutaneously or intracranially inoculated with flagellin plus TCL, flagellin, TCL or saline. Our results showed that prophylacticly subcutaneous administration with TCL and flagellin could induce potent cytotoxic T lymphocyte (CTL) and prolong the survival of GL261-bearing mice significantly, but therapeuticly subcutaneous administration failed to. However, therapeuticly intracranial administration of TCL plus flagellin could prolong the survival. Moreover, intracranial administration of flagellin could recruit CD4⁺ T cells and CD8⁺ T cells to brain tissues, induce proliferation of natural killer (NK) cells, CD4⁺ T cells and CD8⁺ T cells in peripheral blood mononuclear cells and induce to splenomegaly. The results suggested that flagellin could be acted as an efficient adjuvant for TCL based vaccine.

Antitumor activity of CAR-T cells targeting the intracellular oncoprotein WT1 can be enhanced by vaccination

The recent success of chimeric antigen receptor (CAR)-T cell therapy for treatment of hematologic malignancies supports further development of treatments for both liquid and solid tumors. However, expansion of CAR-T cell therapy is limited by the availability of surface antigens specific for the tumor while sparing normal cells. There is a rich diversity of tumor antigens from intracellularly expressed proteins that current and conventional CAR-T cells are unable to target. Furthermore, adoptively transferred T cells often suffer from exhaustion and insufficient expansion, in part, because of the immunosuppressive mechanisms operating in tumor-bearing hosts. Therefore, it is necessary to develop means to further activate and expand those CAR-T cells in vivo. The Wilms tumor 1 (WT1) is an intracellular oncogenic transcription factor that is an attractive target for cancer immunotherapy because of its overexpression in a wide range of leukemias and solid tumors, and a low level of expression in normal adult tissues. In the present study, we developed CAR-T cells consisting of a single chain variable fragment (scFv) specific to the WT1_235-243/HLA-A*2402 complex. The therapeutic efficacy of our CAR-T cells was demonstrated in a xenograft model, which was further enhanced by vaccination with dendritic cells (DCs) loaded with the corresponding antigen. This enhanced efficacy was mediated, at least partly, by the expansion and activation of CAR-T cells. CAR-T cells shown in the present study not only demonstrate the potential to expand the range of targets available to CAR-T cells, but also provide a proof of concept that efficacy of CAR-T cells targeting peptide/major histocompatibility complex can be boosted by vaccination.

Current and emerging EGFR therapies for glioblastoma

Glioblastomas (GBMs) are the most lethal and hard to treat malignancies in clinical practice. The standard of care for treating GBM involving surgery and adjuvant radiotherapy and concomitant temozolomide (TMZ) has remained virtually unchanged in the past decade. Molecular targeted therapies against cancer-specific structures have reported mediocre results in the treatment of GBM, due to multiple factors such as the presence of the blood brain barrier or a vast array of molecular alterations which greatly hinder the action of the most therapeutic agents. One such therapy is directed against the epidermal growth factor (EGF) and its' receptor (EGFR) using either monoclonal antibodies or tyrosine kinase inhibitors. Even though anti-EGF/EGFR treatment produced encouraging results in other forms of cancer it failed to present any clinical benefit for patients with GBM. Lately, immunotherapies that focus on using the host's own immune system against cancer cells have gained popularity, with approaches like peptide vaccination being successfully used in clinical trials for different types of malignancies. These immune-based therapies could hold the key to improving both the prognosis and quality of life for patients suffering for cancers previously considered incurable, such as GBM.

The Potential of Cellular- and Viral-Based Immunotherapies for Malignant Glioma-Dendritic Cell Vaccines, Adoptive Cell Transfer, and Oncolytic Viruses

PURPOSE OF REVIEW

Malignant gliomas, including glioblastoma and anaplastic astrocytoma, are the most frequent primary brain tumors and present with many treatment challenges. In this review, we discuss the potential of cellular- and viral-based immunotherapies in the treatment of malignant glioma, specifically focusing on dendritic cell vaccines, adoptive cell therapy, and oncolytic viruses.

RECENT FINDINGS

Diverse cellular- and viral-based strategies have been engineered and optimized to generate either a specific or broad antitumor immune response in malignant glioma. Due to their successes in the preclinical arena, many of these therapies have undergone phase I and II clinical testing. These early clinical trials have demonstrated the feasibility, safety, and efficacy of these immunotherapies. Dendritic cell vaccines, adoptive cell transfer, and oncolytic viruses may have a potential role in the treatment of malignant glioma. However, these modalities must be investigated in well-designed phase III trials to prove their efficacy.

Improving Adoptive T Cell Therapy: The Particular Role of T Cell Costimulation, Cytokines, and Post-Transfer Vaccination

Adoptive cellular therapy (ACT) is a form of immunotherapy whereby antigen-specific T cells are isolated or engineered, expanded ex vivo, and transferred back to patients. Clinical benefit after ACT has been obtained in treatment of infection, various hematological malignancies, and some solid tumors; however, due to poor functionality and persistence of the transferred T cells, the efficacy of ACT in the treatment of most solid tumors is often marginal. Hence, much effort is undertaken to improve T cell function and persistence in ACT and significant progress is being made. Herein, we will review strategies to improve ACT success rates in the treatment of cancer and infection. We will deliberate on the most favorable phenotype for the tumor-specific T cells that are infused into patients and on how to obtain T cells bearing this phenotype by applying novel ex vivo culture methods. Moreover, we will discuss T cell function and persistence after transfer into patients and how these factors can be manipulated by means of providing costimulatory signals, cytokines, blocking antibodies to inhibitory molecules, and vaccination. Incorporation of these T cell stimulation strategies and combinations of the different treatment modalities are likely to improve clinical response rates further.

Immunotherapy in glioblastoma: emerging options in precision medicine

Immunotherapy for glioblastoma (GBM) provides a unique opportunity for targeted therapies for each patient, addressing individual variability in genes, tumor biomarkers and clinical profile. As immunotherapy has the potential to specifically target tumor cells with minimal risk to normal tissue, several immunotherapeutic strategies are currently being evaluated in clinical trials in GBM. With the Precision Medicine Initiative being announced in the President's State of the Union Address in 2016, GBM immunotherapy provides a useful platform for changing the landscape in treating patients with difficult disease.

Stereotaxic administrations of allogeneic human Vγ9Vδ2 T cells efficiently control the development of human glioblastoma brain tumors

Glioblastoma multiforme (GBM) represents the most frequent and deadliest primary brain tumor. Aggressive treatment still fails to eliminate deep brain infiltrative and highly resistant tumor cells. Human Vγ9Vδ2 T cells, the major peripheral blood γδ T cell subset, react against a wide array of tumor cells and represent attractive immune effector T cells for the design of antitumor therapies. This study aims at providing a preclinical rationale for immunotherapies in GBM based on stereotaxic administration of allogeneic human Vγ9Vδ2 T cells. The feasibility and the antitumor efficacy of stereotaxic Vγ9Vδ2 T cell injections have been investigated in orthotopic GBM mice model using selected heterogeneous and invasive primary human GBM cells. Allogeneic human Vγ9Vδ2 T cells survive and patrol for several days within the brain parenchyma following adoptive transfer and can successfully eliminate infiltrative GBM primary cells. These striking observations pave the way for optimized stereotaxic antitumor immunotherapies targeting human allogeneic Vγ9Vδ2 T cells in GBM patients.

Immunomonitoring in glioma immunotherapy: current status and future perspectives

Given the continued poor clinical outcomes and refractory nature of glioblastoma multiforme to traditional interventions, immunotherapy is gaining traction due to its potential for specific tumor-targeting and long-term antitumor protective surveillance. Currently, development of glioma immunotherapy relies on overall survival as an endpoint in clinical trials. However, the identification of surrogate immunologic biomarkers can accelerate the development of successful immunotherapeutic strategies. Immunomonitoring techniques possess the potential to elucidate immunological mechanisms of antitumor responses, monitor disease progression, evaluate therapeutic effect, identify candidates for immunotherapy, and serve as prognostic markers of clinical outcome. Current immunomonitoring assays assess delayed-type hypersensitivity, T cell proliferation, cytotoxic T-lymphocyte function, cytokine secretion profiles, antibody titers, and lymphocyte phenotypes. Yet, no single immunomonitoring technique can reliably predict outcomes, relegating immunological markers to exploratory endpoints. In response, the most recent immunomonitoring assays are incorporating emerging technologies and novel analysis techniques to approach the goal of identifying a competent immunological biomarker which predicts therapy responsiveness and clinical outcome. This review addresses the current status of immunomonitoring in glioma vaccine clinical trials with emphasis on correlations with clinical response.

An Eighteen Serum Cytokine Signature for Discriminating Glioma from Normal Healthy Individuals

Glioblastomas (GBM) are largely incurable as they diffusely infiltrate adjacent brain tissues and are difficult to diagnose at early stages. Biomarkers derived from serum, which can be obtained by minimally invasive procedures, may help in early diagnosis, prognosis and treatment monitoring. To develop a serum cytokine signature, we profiled 48 cytokines in sera derived from normal healthy individuals (n = 26) and different grades of glioma patients (n = 194). We divided the normal and grade IV glioma/GBM serum samples randomly into equal sized training and test sets. In the training set, the Prediction Analysis for Microarrays (PAM) identified a panel of 18 cytokines that could discriminate GBM sera from normal sera with maximum accuracy (95.40%) and minimum error (4.60%). The 18-cytokine signature obtained in the training set discriminated GBM sera from normal sera in the test set as well (accuracy 96.55%; error 3.45%). Interestingly, the 18-cytokine signature also differentiated grade II/Diffuse Astrocytoma (DA) and grade III/Anaplastic Astrocytoma (AA) sera from normal sera very efficiently (DA vs. normal–accuracy 96.00%, error 4.00%; AA vs. normal–accuracy 95.83%, error 4.17%). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis using 18 cytokines resulted in the enrichment of two pathways, cytokine-cytokine receptor interaction and JAK-STAT pathways with high significance. Thus our study identified an 18-cytokine signature for distinguishing glioma sera from normal healthy individual sera and also demonstrated the importance of their differential abundance in glioma biology.

Distribution and characterization of tumor-associated macrophages/microglia in rat C6 glioma

Immunity responses and immunotherapy are novel areas of research for the pathological development and treatment of glioma, the most common brain cancer. Characterization of the subpopulations of infiltrated immune cells may aid in our understanding of the tumor immune response and contribute to the identification of cellular targets for selective immunotherapy. Using a rat C6 glioma model, the present study observed a significant heterogeneity of active macrophages and microglia, including cluster of differentiation 8 (CD8)⁺, endothelial monocyte-activating polypeptide II (EMAPII)⁺ and ED1⁺ cells, mostly in the areas of compact tumor growth and inside or around the pannecrosis. Moreover, the CD8⁺ cells were similar to reactive ED1⁺ and EMAPII⁺ microglia/macrophages in morphology and distribution, but different from the W3/13⁺ T cells. These observations suggest that different subtypes of macrophages and microglia are involved in glioma development and thus, may be potential targets for immunotherapeutic antitumor strategies.

Immunobiology and immunotherapeutic targeting of glioma stem cells

For decades human brain tumors have confounded our efforts to effectively manage and treat patients. In adults, glioblastoma multiforme is the most common malignant brain tumor with a patient survival of just over 14 months. In children, brain tumors are the leading cause of solid tumor cancer death and gliomas account for one-fifth of all childhood cancers. Despite advances in conventional treatments such as surgical resection, radiotherapy, and systemic chemotherapy, the incidence and mortality rates for gliomas have essentially stayed the same. Furthermore, research efforts into novel therapeutics that initially appeared promising have yet to show a marked benefit. A shocking and somewhat disturbing view is that investigators and clinicians may have been targeting the wrong cells, resulting in the appearance of the removal or eradication of patient gliomas only to have brain cancer recurrence. Here we review research progress in immunotherapy as it pertains to glioma treatment and how it can and is being adapted to target glioma stem cells (GSCs) as a means of dealing with this potential paradigm.

A new hope in immunotherapy for malignant gliomas: adoptive T cell transfer therapy

Immunotherapy emerged as a promising therapeutic approach to highly incurable malignant gliomas due to tumor-specific cytotoxicity, minimal side effect, and a durable antitumor effect by memory T cells. But, antitumor activities of endogenously activated T cells induced by immunotherapy such as vaccination are not sufficient to control tumors because tumor-specific antigens may be self-antigens and tumors have immune evasion mechanisms to avoid immune surveillance system of host. Although recent clinical results from vaccine strategy for malignant gliomas are encouraging, these trials have some limitations, particularly their failure to expand tumor antigen-specific T cells reproducibly and effectively. An alternative strategy to overcome these limitations is adoptive T cell transfer therapy, in which tumor-specific T cells are expanded ex vivo rapidly and then transferred to patients. Moreover, enhanced biologic functions of T cells generated by genetic engineering and modified immunosuppressive microenvironment of host by homeostatic T cell expansion and/or elimination of immunosuppressive cells and molecules can induce more potent antitumor T cell responses and make this strategy hold promise in promoting a patient response for malignant glioma treatment. Here we will review the past and current progresses and discuss a new hope in adoptive T cell therapy for malignant gliomas.

The value of EGFRvIII as the target for glioma vaccines

Malignant brain tumors continue to be rapidly progressive and resistant to most treatments. Even with state-of-the-art standard of care (surgery, chemotherapy, and radiotherapy) long-term survival in the last 80 years improved from 6 to 15 months. Improved imaging has also likely contributed to prolonged survival. Immunotherapy for cancer dates back to publications from 1742. The central idea is that the immune system can detect and eliminate foreign antigens, either from infectious agents or tumors, and thus could be therapeutic in brain tumors. Recent introduction of immune modulators of cytotoxic T-lymphocyte antigen (CTLA)-4 and programmed cell death 1/programmed cell death 1 ligand (PD-1/PDL1) add much excitement to this field. For brain tumors, there are several ongoing phase I and III trials to determine whether any of the current immunotherapy approaches can demonstrate activity in randomized, controlled double-blinded trials-with ongoing and historical trials presented in tables within the manuscript. Immunotherapy has explored the use of various types of antigens (obtained either from homogenates of patients' tumors or synthetically produced), and various immunization procedures and adjuvants. Glioma antigens have also been isolated from the patients' own tumor, then produced in vitro (for example the glioma antigen EGFRvIII), and used to immunize patients directly, or with carriers such as dendritic cells with or without additional adjuvants. Several of these practical approaches are currently in phase III trials. Remaining challenges are how to increase the percentage of complete responses and response duration, and the enigmatic absence of an almost total lack of adverse brain inflammation following immunization of brain tumor patients, as has been observed following immunization against brain antigens in other diseases, such as Alzheimer's Disease.

Glioblastoma multiforme: State of the art and future therapeutics

BACKGROUND

Glioblastoma multiforme (GBM) is the most common and lethal primary malignancy of the central nervous system (CNS). Despite the proven benefit of surgical resection and aggressive treatment with chemo- and radiotherapy, the prognosis remains very poor. Recent advances of our understanding of the biology and pathophysiology of GBM have allowed the development of a wide array of novel therapeutic approaches, which have been developed. These novel approaches include molecularly targeted therapies, immunotherapies, and gene therapy.

METHODS

We offer a brief review of the current standard of care, and a survey of novel therapeutic approaches for treatment of GBM.

RESULTS

Despite promising results in preclinical trials, many of these therapies have demonstrated limited therapeutic efficacy in human clinical trials. Thus, although survival of patients with GBM continues to slowly improve, treatment of GBM remains extremely challenging.

CONCLUSION

Continued research and development of targeted therapies, based on a detailed understanding of molecular pathogenesis can reasonably be expected to yield improved outcomes for patients with GBM.

Recombinant adenoviral vector expressing human wild-type p53, GM-CSF, and B7-1 genes suppresses the growth of glioma in vivo

Malignant gliomas are the most common of primary brain tumors and have been proven incurable with conventional treatments. Evidence have shown that a recombinant adenoviral vector expressing human wild-type p53, granulocyte-macrophage colony-stimulating factor (GM-CSF), and B7-1 genes (BB-102) may have antitumor effects in vitro. In this study, we investigated the effects of BB-102-based vaccine on glioma in vivo. An animal model using nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice with human immune system was established. The mice were vaccinated with inactivated U251 glioma cells transduced with BB-102 or adenoviral vector expressing green fluorescence protein (Ad-GFP) as a control and followed by the challenge of live U251 glioma cells. Tumor growth and antitumor responses were measured. Data showed that mice vaccinated with BB-102 had significantly reduced local tumor growth compared to mice with Ad-GFP vaccination or the control group. Histopathological analysis displayed low tumor cell density and significant infiltration of human peripheral blood lymphocytes (HuPBLs) in the tumor tissues of mice transduced with BB-102. Immunohistochemical analysis showed that mutant p53 was not expressed in tumor tissues of mice with BB-102 vaccination, and the expression level of Ki67 was significantly lower in the tumor tissues of the BB-102 group than those in the Ad-GFP group or the control group. Further study demonstrated that mice with BB-102 vaccination had significantly increased total T cell numbers, total T cell proportion, CD4+ T cell proportion, and CD8+ T cell proportion in spleens, as well as higher value of IgG, IgA, and IgE in sera. These data suggest that the recombinant adenoviral vector expressing human wild-type p53, GM-CSF, and B7-1 genes could suppress glioma in NOD/SCID mice model and might be considered as a novel strategy for glioma therapy.

Immune-checkpoint blockade and active immunotherapy for glioma

Cancer immunotherapy has made tremendous progress, including promising results in patients with malignant gliomas. Nonetheless, the immunological microenvironment of the brain and tumors arising therein is still believed to be suboptimal for sufficient antitumor immune responses for a variety of reasons, including the operation of “immune-checkpoint” mechanisms. While these mechanisms prevent autoimmunity in physiological conditions, malignant tumors, including brain tumors, actively employ these mechanisms to evade from immunological attacks. Development of agents designed to unblock these checkpoint steps is currently one of the most active areas of cancer research. In this review, we summarize recent progresses in the field of brain tumor immunology with particular foci in the area of immune-checkpoint mechanisms and development of active immunotherapy strategies. In the last decade, a number of specific monoclonal antibodies designed to block immune-checkpoint mechanisms have been developed and show efficacy in other cancers, such as melanoma. On the other hand, active immunotherapy approaches, such as vaccines, have shown encouraging outcomes. We believe that development of effective immunotherapy approaches should ultimately integrate those checkpoint-blockade agents to enhance the efficacy of therapeutic approaches. With these agents available, it is going to be quite an exciting time in the field. The eventual success of immunotherapies for brain tumors will be dependent upon not only an in-depth understanding of immunology behind the brain and brain tumors, but also collaboration and teamwork for the development of novel trials that address multiple layers of immunological challenges in gliomas.

Clinical trials in cellular immunotherapy for brain/CNS tumors

High-grade gliomas are the most common type of primary malignant brain/CNS tumor. There have been only modest advances in surgical techniques, radiotherapy and chemotherapy for high-grade gliomas over the past several decades. None of these have provided a major improvement in survival for patients. Recently, immunotherapy has been explored for the treatment of high-grade gliomas. Immunotherapy capitalizes on the specificity of the host immune system to selectively target tumor cells for destruction, while sparing normal brain parenchyma, thus making it a particularly attractive option. This article provides a comprehensive review of published clinical trials evaluating cellular immunotherapy in primary brain/CNS tumors.

Vaccine strategies for glioblastoma: progress and future directions

Recent advances in glioblastoma therapy have led to optimism that more effective therapies will improve outcomes. Immunotherapy is a promising approach that has demonstrated the potential to eradicate cancer cells with cellular-level accuracy while minimizing damage to surrounding healthy tissue. Several vaccination strategies have been evaluated for activity against glioblastoma in clinical trials. These include peptide vaccines, polyvalent dendritic cell vaccines, heat shock protein vaccines and adoptive immunotherapy. In this review, we highlight clinical trials representative of each of these approaches and discuss strategies for integrating these therapies into routine patient care.

Cell-based immunotherapy against gliomas: from bench to bedside

Glioblastoma (GBM) comprises 51% of all gliomas and is the most malignant form of brain tumors with a median survival of 18-21 months. Standard-of-care treatment includes maximal surgical resection of the tumor mass in combination with radiation and chemotherapy. However, as the poor survival rate indicates, these treatments have not been effective in preventing disease progression. Cellular immunotherapy is currently being explored as therapeutic approach to treat malignant brain tumors. In this review, we discuss advances in active, passive, and vaccine-based immunotherapeutic strategies for gliomas both at the bench and in the clinic.

Passive immunotherapeutic strategies for the treatment of malignant gliomas

This review provides historical and recent perspectives related to passive immunotherapy for high-grade gliomas. The authors discuss approaches that use lymphokine-activated killer cells, cytotoxic T lymphocytes, and monoclonal antibodies.

Integration of autologous dendritic cell-based immunotherapy in the standard of care treatment for patients with newly diagnosed glioblastoma: results of the HGG-2006 phase I/II trial

PURPOSE

Dendritic cell (DC)-based tumor vaccination has rendered promising results in relapsed high-grade glioma patients. In the HGG-2006 trial (EudraCT 2006-002881-20), feasibility, toxicity, and clinical efficacy of the full integration of DC-based tumor vaccination into standard postoperative radiochemotherapy are studied in 77 patients with newly diagnosed glioblastoma.

PATIENTS AND METHODS

Autologous DC are generated after leukapheresis, which is performed before the start of radiochemotherapy. Four weekly induction vaccines are administered after the 6-week course of concomitant radiochemotherapy. During maintenance chemotherapy, 4 boost vaccines are given. Feasibility and progression-free survival (PFS) at 6 months (6mo-PFS) are the primary end points. Overall survival (OS) and immune profiling, rather than monitoring, as assessed in patients' blood samples, are the secondary end points. Analysis has been done on intent-to-treat basis.

RESULTS

The treatment was feasible without major toxicity. The 6mo-PFS was 70.1 % from inclusion. Median OS was 18.3 months. Outcome improved significantly with lower EORTC RPA classification. Median OS was 39.7, 18.3, and 10.7 months for RPA classes III, IV, and V, respectively. Patients with a methylated MGMT promoter had significantly better PFS (p = 0.0027) and OS (p = 0.0082) as compared to patients with an unmethylated status. Exploratory "immunological profiles" were built to compare to clinical outcome, but no statistical significant evidence was found for these profiles to predict clinical outcome.

CONCLUSION

Full integration of autologous DC-based tumor vaccination into standard postoperative radiochemotherapy for newly diagnosed glioblastoma seems safe and possibly beneficial. These results were used to power the currently running phase IIb randomized clinical trial.

Cellular-based immunotherapies for patients with glioblastoma multiforme

Treatment of patients with glioblastoma multiforme (GBM) remains to be a challenge with a median survival of 14.6 months following diagnosis. Standard treatment options include surgery, radiation therapy, and systemic chemotherapy with temozolomide. Despite the fact that the brain constitutes an immunoprivileged site, recent observations after immunotherapies with lysate from autologous tumor cells pulsed on dendritic cells (DCs), peptides, protein, messenger RNA, and cytokines suggest an immunological and even clinical response from immunotherapies. Given this plethora of immunomodulatory therapies, this paper gives a structure overview of the state-of-the art in the field. Particular emphasis was also put on immunogenic antigens as potential targets for a more specific stimulation of the immune system against GBM.

Adoptive cell transfer therapy for malignant gliomas

To date, various adoptive immunotherapies have been attempted for treatment of malignant gliomas using nonspecific and/or specific effector cells. Since the late 1980s, with the development of rIL-2, the efficacy of lymphokine-activated killer (LAK) cell therapy with or without rIL-2 for malignant gliomas had been tested with some modifications in therapeutic protocols. With advancements in technology, ex vivo expanded tumor specific cytotoxic T-lymphocytes (CTL) or those lineages were used in clinical trials with higher tumor response rates. In addition, combinations of those adoptive cell transfer using LAK cells, CTLs or natural killer (NK) cells with autologous tumor vaccine (ATV) therapy were attempted. Also, a strategy of high-dose (or lymphodepleting) chemotherapy followed by adoptive cell transfer has been drawing attentions recently. The most important role of these clinical studies using cell therapy was to prove that these ex vivo expanded effector cells could kill tumor cells in vivo. Although recent clinical results could demonstrate radiologic tumor shrinkage in a number of cases, cell transfer therapy alone has been utilized less frequently, because of the high cost of ex vivo cell expansion, the short duration of antitumor activity in vivo, and the recent shift of interest to vaccine immunotherapy. Nevertheless, NK cell therapy using specific feeder cells or allergenic NK cell lines have potentials to be a good choice of treatment because of easy ex vivo expansion and their efficacy especially when combined with vaccine therapy as they are complementary to each other. Also, further studies are expected to clarify the efficacy of the high-dose chemotherapy followed by a large scale cell transfer therapy as a new therapeutic strategy for malignant gliomas.

Cytokine therapy

Cytokines are a heterogeneous group of soluble small polypeptides or glycoproteins, which exert pleiotropic and redundant effects that promote growth, differentiation and activation of normal cells. Cytokines can have either pro- or anti-inflammatory activity and immunosuppressive activity, depending on the microenvironments. The tumor microenvironment consists of a variable combination of tumor cells, endothelial cells and infiltrating leukocytes, such as macrophages, T-lymphocytes, natural killer (NK) cells, B cells and antigen-presenting cells (APCs). Cytokine production acts as a means of communication in the tumor microenvironment. In this article, we review the cross-talk between cytokines in the tumor environment and the cytokine therapies that have been used till date for glioma treatment.

Antigen-receptor gene-modified T cells for treatment of glioma

Immunological effector cells and molecules have been shown to access intracranial tumor sites despite the existence of blood brain barrier (BBB) or immunosuppressive mechanisms associated with brain tumors. Recent progress in T-cell biology and tumor immunology made possible to develop strategies of tumor-associated antigen-specific immunotherapeutic approaches such as vaccination with defined antigens and adoptive T-cell therapy with antigen-specific T cells including gene-modified T cells for the treatment of patients with brain tumors. An array of recent reports on the trials of active and passive immunotherapy for patients with brain tumors have documented safety and some preliminary clinical efficacy, although the ultimate judgment for clinical benefits awaits rigorous evaluation in trials of later phases. Nevertheless, treatment with lymphocytes that are engineered to express tumor-specific receptor genes is a promising immunotherapy against glioma, based on the significant efficacy reported in the trials for patients with other types of malignancy. Overcoming the relative difficulty to apply immunotherapeutic approach to intracranial region, current advances in the understanding of human tumor immunology and the gene-therapy methodology will address the development of effective immunotherapy of brain tumors.

Immunotherapy for the treatment of glioblastoma

Glioblastoma, the most aggressive primary brain tumor, thrives in a microenvironment of relative immunosuppression within the relatively immune-privileged central nervous system. Despite treatments with surgery, radiation therapy, and chemotherapy, prognosis remains poor. The recent success of immunotherapy in the treatment of other cancers has renewed interest in vaccine therapy for the treatment of gliomas. In this article, we outline various immunotherapeutic strategies, review recent clinical trials data, and discuss the future of vaccine therapy for glioblastoma.

Challenges in immunotherapy presented by the glioblastoma multiforme microenvironment

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor in adults. Despite intensive treatment, the prognosis for patients with GBM remains grim with a median survival of only 14.6 months. Immunotherapy has emerged as a promising approach for treating many cancers and affords the advantages of cellular-level specificity and the potential to generate durable immune surveillance. The complexity of the tumor microenvironment poses a significant challenge to the development of immunotherapy for GBM, as multiple signaling pathways, cytokines, and cell types are intricately coordinated to generate an immunosuppressive milieu. The development of new immunotherapy approaches frequently uncovers new mechanisms of tumor-mediated immunosuppression. In this review, we discuss many of the current approaches to immunotherapy and focus on the challenges presented by the tumor microenvironment.

Understanding the role of cytokines in Glioblastoma Multiforme pathogenesis

Cytokines play a significant role in cancer diagnosis, prognosis and therapy. The immune system's failure to recognize the malignant tumor cells and mount an effective response may be the result of tumor-associated cytokine deregulation. Glioblastoma Multiforme (GBM) has a characteristic cytokine expression pattern, and abnormalities in cytokine expression have been implicated in gliomagenesis. Within the heterogeneous GBM microenvironment, the tumor cells, normal brain cells, immune cells, and stem cells interact with each other through the complex cytokine network. This review summarizes the current understanding of the functions of key cytokines on GBM, and highlights potential therapeutic applications targeting these cytokines.

Immunotherapy coming of age: what will it take to make it standard of care for glioblastoma?

With the recent approval by the FDA of an immunotherapy for prostate cancer and another positive immunotherapy trial in melanoma, immunotherapy may finally be coming of age. So what will it take for it to become part of the standard treatment for glioblastoma? To put this question into perspective, we summarize critical background information in neuro-immunology, address immunotherapy clinical trial design, and discuss a number of extrinsic factors that will impact the development of immunotherapy in neuro-oncology.

Cellular and vaccine therapeutic approaches for gliomas

Despite new additions to the standard of care therapy for high grade primary malignant brain tumors, the prognosis for patients with this disease is still poor. A small contingent of clinical researchers are focusing their efforts on testing the safety, feasibility and efficacy of experimental active and passive immunotherapy approaches for gliomas and are primarily conducting Phase I and II clinical trials. Few trials have advanced to the Phase III arena. Here we provide an overview of the cellular therapies and vaccine trials currently open for patient accrual obtained from a search of http://www.clinicaltrials.gov. The search was refined with terms that would identify the Phase I, II and III immunotherapy trials open for adult glioma patient accrual in the United States. From the list, those that are currently open for patient accrual are discussed in this review. A variety of adoptive immunotherapy trials using ex vivo activated effector cell preparations, cell-based and non-cell-based vaccines, and several combination passive and active immunotherapy approaches are discussed.

Overview of cellular immunotherapy for patients with glioblastoma

High grade gliomas (HGG) including glioblastomas (GBM) are the most common and devastating primary brain tumours. Despite important progresses in GBM treatment that currently includes surgery combined to radio- and chemotherapy, GBM patients' prognosis remains very poor. Immunotherapy is one of the new promising therapeutic approaches that can specifically target tumour cells. Such an approach could also maintain long term antitumour responses without inducing neurologic defects. Since the past 25 years, adoptive and active immunotherapies using lymphokine-activated killer cells, cytotoxic T cells, tumour-infiltrating lymphocytes, autologous tumour cells, and dendritic cells have been tested in phase I/II clinical trials with HGG patients. This paper inventories these cellular immunotherapeutic strategies and discusses their efficacy, limits, and future perspectives for optimizing the treatment to achieve clinical benefits for GBM patients.

Immune therapeutic targeting of glioma cancer stem cells

Glioblastoma multiforme (GBM) is a lethal cancer that responds poorly to radiotherapy and chemotherapy. Glioma cancer stem cells (gCSCs) have been shown to recapitulate the characteristic features of GBM and to mediate chemotherapy and radiation resistance. Immunotherapeutic targeting of this cell population holds therapeutic promise but must be considered in the context of the immunosuppressive properties mediated by the gCSC. Recent findings have indicated that this goal will be challenging because the gCSC can suppress both the innate and adaptive immune systems by a variety of gCSC-secreted products and cell-membrane interactions. In this review article, we will attempt to reconcile the disparate research findings regarding the potential of immune targeting of the gCSC and propose several novel solutions.