Dendritic cell vaccination in glioblastoma patients induces systemic and intracranial T-cell responses modulated by the local central nervous system tumor microenvironment

Immunosuppressive tumor-infiltrating myeloid cells mediate adaptive immune resistance via a PD-1/PD-L1 mechanism in glioblastoma

Background

Adaptive immune resistance in the tumor microenvironment appears to attenuate the immunotherapeutic targeting of glioblastoma (GBM). In this study, we identified a tumor-infiltrating myeloid cell (TIM) population that expands in response to dendritic cell (DC) vaccine treatment. The aim of this study was to understand how this programmed death ligand 1 (PD-L1)-expressing population restricts activation and tumor-cytolytic function of vaccine-induced tumor-infiltrating lymphocytes (TILs).

Methods

To test this hypothesis in our in vivo preclinical model, we treated mice bearing intracranial gliomas with DC vaccination ± murine anti-PD-1 monoclonal antibody (mAb) blockade or a colony stimulating factor 1 receptor inhibitor (CSF-1Ri) (PLX3397) and measured overall survival. We then harvested and characterized the PD-L1+ TIM population and its role in TIL activation and tumor cytolysis in vitro.

Results

Our data indicated that the majority of PD-L1 expression in the GBM environment is contributed by TIMs rather than by tumor cells themselves. While PD-1 blockade partially reversed the TIL dysfunction, targeting TIMs directly with CSF-1Ri altered TIM expression of key chemotactic factors associated with promoting increased TIL infiltration after vaccination. Neither PD-1 mAb nor CSF-1Ri had a demonstrable therapeutic benefit alone, but when combined with DC vaccination, a significant survival benefit was observed. When the tripartite regimen was given (DC vaccine, PD-1 mAb, PLX3397), long-term survival was noted together with an increase in the number of TILs and TIL activation.

Conclusion

Together, these studies elucidate the role that TIMs play in mediating adaptive immune resistance in the GBM microenvironment and provide evidence that they can be manipulated pharmacologically with agents that are clinically available. Development of immune resistance in response to active vaccination in GBM can be reversed with dual administration of CSF-1Ri and PD-1 mAb.

Vaccination in the immunotherapy of glioblastoma

Glioblastoma remains one of the most common central nervous system tumors with an extremely poor prognosis. Recently, rapid progress in immunotherapy has provided new options for the treatment of glioblastoma. Vaccination, the primary method of immunotherapy, stimulates the body's tumor-specific immune response by the injection of foreign antigens. Peptide vaccines involve the injection of tumor-specific antigens, such as EGFRvIII or heat-shock proteins. Cell-based vaccines, which primarily include dendritic cell vaccines and tumor cell vaccines, involve injections of ex vivo-modified cells. Despite the encouraging results of phase I/II clinical trials, no successful phase III clinical trials involving glioblastoma immunotherapy, including glioblastoma vaccinations, have been reported to date. In this review, the authors summarize the published outcomes of glioblastoma vaccine therapy, explore its future prospects based on ongoing clinical trials, and discuss combined therapy as a future direction for glioblastoma treatment.

Contributions of immune cell populations in the maintenance, progression, and therapeutic modalities of glioma

Immunotherapies are becoming a promising strategy for malignant disease. Selectively directing host immune responses to target cancerous tissue is a milestone of human health care. The roles of the innate and adaptive immune systems in both cancer progression and elimination are now being realized. Defining the immune cell environment and identifying the contributions of each sub-population of these cells has lead to an understanding of the immunotherapeutic processes, and demonstrated the potential of the immune system to drive cancer shrinkage and sustained immunity against disease. Poorly treated diseases, such as high-grade glioma, suffer from lack of therapeutic efficacy and rapid progression. Immunotherapeutic success in other solid malignancies, such as melanoma, now provides the principals for which this treatment paradigm can be adapted for primary brain cancers. The central nervous system is complex, and relative contributions of immune sub-populations to high grade glioma progression are not fully characterized. Here, we summarize recent research in both animal and humans which add to the knowledge base of how innate and adaptive immune cells contribute to glioma progression, and outline work which has demonstrated their potential to elicit anti-tumorigenic responses. Additionally, we highlight Neuropilin 1, a cell surface receptor protein, describe its signaling functions in the context of immunity, and point to its potential to slow glioma progression.

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.

Complete remission of rare adenocarcinoma of the oropharynx with APCEDEN® (dendritic cell-based vaccine): a case report

APCEDEN^® is an autologous monocyte‐derived dendritic cell‐based immunotherapy. A 58‐year‐old man with adenocarcinoma of oropharynx shows complete remission after receiving APCEDEN^® in conjunction with Geftinib validated by reduction in size, whereas Gefitinib alone lead to disease progression.

Chemokines as adjuvants for immunotherapy: implications for immune activation with CCL3

INTRODUCTION

Immunotherapy embodies any approach that manipulates the immune system for therapeutic benefit. In this regard, various clinical trials have employed direct vaccination with patient-specific dendritic cells or adoptive T cell therapy to target highly aggressive tumors. Both modalities have demonstrated great specificity, an advantage that is unmatched by other treatment strategies. However, their full potential has yet to be realized. Areas covered: In this review, we provide an overview of chemokines in pathogen and anti-tumor immune responses and discuss further improving immunotherapies by arming particular chemokine axes. Expert commentary: The chemokine macrophage inflammatory protein-1 alpha (MIP-1α, CCL3) has emerged as a potent activator of both innate and adaptive responses. Specifically, CCL3 plays a critical role in recruiting distinct immune phenotypes to intratumoral sites, is a pivotal player in regulating lymph node homing of dendritic cell subsets, and induces antigen-specific T cell responses. The recent breadth of literature outlines the various interactions of CCL3 with these cellular subsets, which have now served as a basis for immunotherapeutic translation.

Detection of immune responses after immunotherapy in glioblastoma using PET and MRI

Contrast-enhanced MRI is typically used to follow treatment response and progression in patients with glioblastoma (GBM). However, differentiating tumor progression from pseudoprogression remains a clinical dilemma largely unmitigated by current advances in imaging techniques. Noninvasive imaging techniques capable of distinguishing these two conditions could play an important role in the clinical management of patients with GBM and other brain malignancies. We hypothesized that PET probes for deoxycytidine kinase (dCK) could be used to differentiate immune inflammatory responses from other sources of contrast-enhancement on MRI. Orthotopic malignant gliomas were established in syngeneic immunocompetent mice and then treated with dendritic cell (DC) vaccination and/or PD-1 mAb blockade. Mice were then imaged with [¹⁸F]-FAC PET/CT and MRI with i.v. contrast. The ratio of contrast enhancement on MRI to normalized PET probe uptake, which we term the immunotherapeutic response index, delineated specific regions of immune inflammatory activity. On postmortem examination, FACS-based enumeration of intracranial tumor-infiltrating lymphocytes directly correlated with quantitative [¹⁸F]-FAC PET probe uptake. Three patients with GBM undergoing treatment with tumor lysate-pulsed DC vaccination and PD-1 mAb blockade were also imaged before and after therapy using MRI and a clinical PET probe for dCK. Unlike in mice, [¹⁸F]-FAC is rapidly catabolized in humans; thus, we used another dCK PET probe, [¹⁸F]-clofarabine ([¹⁸F]-CFA), that may be more clinically relevant. Enhanced [¹⁸F]-CFA PET probe accumulation was identified in tumor and secondary lymphoid organs after immunotherapy. Our findings identify a noninvasive modality capable of imaging the host antitumor immune response against intracranial tumors.

Identification of T cell target antigens in glioblastoma stem-like cells using an integrated proteomics-based approach in patient specimens

Glioblastoma (GBM) is a highly aggressive brain tumor and still remains incurable. Among others, an immature subpopulation of self-renewing and therapy-resistant tumor cells-often referred to as glioblastoma stem-like cells (GSCs)-has been shown to contribute to disease recurrence. To target these cells personalized immunotherapy has gained a lot of interest, e.g. by reactivating pre-existing anti-tumor immune responses against GSC antigens. To identify T cell targets commonly presented by GSCs and their differentiated counterpart, we used a proteomics-based separation of GSC proteins in combination with a T cell activation assay. Altogether, 713 proteins were identified by LC-ESI-MS/MS mass spectrometry. After a thorough filtering process, 32 proteins were chosen for further analyses. Immunogenicity of corresponding peptides was tested ex vivo. A considerable number of these antigens induced T cell responses in GBM patients but not in healthy donors. Moreover, most of them were overexpressed in primary GBM and also highly expressed in recurrent GBM tissues. Interestingly, expression of the most frequent T cell target antigens could also be confirmed in quiescent, slow-cycling GSCs isolated in high purity by the DEPArray technology. Finally, for a subset of these T cell target antigens, an association between expression levels and higher T cell infiltration as well as an increased expression of positive immune modulators was observed. In summary, we identified novel immunogenic proteins, which frequently induce tumor-specific T cell responses in GBM patients and were also detected in vitro in therapy-resistant quiescent, slow-cycling GSCs. Stable expression of these T cell targets in primary and recurrent GBM support their suitability for future clinical use.

miR-181d regulates human dendritic cell maturation through NF-κB pathway

OBJECTIVES

MicroRNAs (miRNAs) are considered as the cellular regulators which post-transcriptionally modulate gene expression in diverse biological processes including cell development and immunity. In this study, we investigated functions of miR-181d in dendritic cells (DCs) maturation, and the underlying mechanisms were also explored.

MATERIALS AND METHODS

Here we did the miRNA screening in human DCs in response to lipopolysaccharides (LPS) by quantitative real-time PCR (qRT-PCR). The expressions of DCs maturation markers were measured after miRNA mimics transfections. The pharmacological inhibitors of signalling pathways were applied to examine miR-181d effect on DCs maturation by Western blot. Luciferase assay and mixed lymphocyte reaction (MLR) were also performed to reveal the target gene of miR-181d and test the viability of T cells treated with miR-181d transfected DCs.

RESULTS

Overexpression of miR-181d per se is sufficient to promote DCs maturation, and up-regulate CD80 and CD83 expressions without LPS. Besides, we showed that miR-181d activated NF-κB pathway and also promoted the expression of pro-inflammatory cytokine IL12 and TNF-α. Inhibition of NF-κB pathway suppressed DCs maturation. Luciferase reporter assay and target gene knockdown assay indicated that miR-181d targets regulator cylindromatosis (CYLD), a primary negative regulator of NF-κB pathway. MLR assay showed that miR-181d-transfected DCs could promote T-cell proliferation than iDCs in vitro.

CONCLUSION

Our study demonstrates that miR-181d is required for DCs maturation through the activation of NF-κB pathway by targeting CYLD.

Autologous Heat Shock Protein Peptide Vaccination for Newly Diagnosed Glioblastoma: Impact of Peripheral PD-L1 Expression on Response to Therapy

Purpose: Standard therapy for newly diagnosed glioblastoma (GBM) is surgical resection, followed by concurrent radiotherapy and temozolomide chemotherapy. In this phase II clinical trial, the addition of an autologous heat-shock protein vaccine to standard therapy was evaluated. Tumor-induced immunosuppression, mediated by expression of PD-L1 on tumor and circulating immune cells, may impact the efficacy of vaccination. Expression of PD-L1 on peripheral myeloid cells was evaluated for the first time as a predictor of survival.Experimental Design: In this single arm, phase II study, adult patients with GBM underwent surgical resection followed by standard radiation and chemotherapy. Autologous vaccine (Prophage) was generated from resected tumors and delivered in weekly vaccinations after completion of radiotherapy. The primary endpoint was overall survival.Results: Forty-six patients received the vaccine with a median overall survival of 23.8 months [95% confidence interval (CI), 19.8-30.2]. Median overall survival for patients with high PD-L1 expression on myeloid cells was 18.0 months (95% CI, 10.0-23.3) as compared with 44.7 months (95% CI, incalculable) for patients with low PD-L1 expression (hazard ratio 3.3; 95% CI, 1.4-8.6; P = 0.007). A multivariate proportional hazards model revealed MGMT methylation, Karnofsky performance status, and PD-L1 expression as the primary independent predictors of survival.Conclusions: Vaccination with autologous tumor-derived heat shock proteins may improve survival for GBM patients when combined with standard therapy and warrants further study. Systemic immunosuppression mediated by peripheral myeloid expression of PD-L1 is a recently identified factor that may significantly impact vaccine efficacy. Clin Cancer Res; 23(14); 3575-84. ©2017 AACR.

LPS alters the immuno-phenotype of glioma and glioma stem-like cells and induces in vivo antitumor immunity via TLR4

BACKGROUND

This study examined the ability of lipopolysaccharide (LPS) to affect glioma and glioma stem-like cells (GSCs) in vitro and to induce antitumor immunity in vivo and the role of TLR4 in these processes.

METHODS

Using RT-PCR and immunohistochemistry, we examined the expression of TLR4 in 34 glioblastoma clinical samples. Using real time-PCR, western blot and ELISA analyses, the effect of LPS stimulation on the expression of immune related molecules was evaluated in RG2 and U87 GSCs. Control or LPS-pretreated RG2 GSCs were intracranially or subcutaneously implanted into wild-type or nude Fisher 344 rats. Histopathological examinations were used to assess tumor progression and immune infiltration and Kaplan-Meier analyses to compare survival times of the animal models.

RESULTS

TLR4 was highly expressed in glioblastoma clinical samples. In vitro LPS stimulation for 6 h significantly altered expression of immune related molecules in RG2 and U87 GSCs. However, prolonged LPS stimulation diminished this effect. Rats inoculated intracranially with LPS-pretreated RG2 GSCs survived significantly longer than rats inoculated with control RG2 GSCs. In vivo, LPS-pretreated RG2 GSCs expressed higher levels of MHC molecules, CXCL10 and TNF-α and recruited more CD8⁺ lymphocytes. However, intratumoral LPS treatment was not equally beneficial. Furthermore, the in vitro and in vivo effects of LPS stimulation appeared to be largely TLR4-dependent.

CONCLUSION

LPS pretreatment promotes the recognition and eradication of tumor GSCs in vivo when the immune function of the tumor-bearing host is intact. In addition, our data indicate a complex relationship between bacterial infection and glioma prognosis.

Immunotherapy for Brain Tumors

Glioblastoma (GBM) is the most lethal form of brain tumor and remains a large, unmet medical need. This review focuses on recent advances in the neurosciences that converge with the broader field of immuno-oncology. Recent findings in neuroanatomy provide a basis for new approaches of cellular therapies for tumors that involve the CNS. The ultimate success of immunotherapy in the CNS will require improved imaging technologies and methods for analysis of the tumor microenvironment in patients with GBM. It is likely that combinatorial approaches with targeted immunotherapies will be required to exploit the vulnerabilities of GBM and other brain tumors.

Cellular immunotherapy of cancer: an overview and future directions

The clinical success of checkpoint inhibitors has led to a renaissance of interest in cancer immunotherapies. In particular, the possibility of ex vivo expanding autologous lymphocytes that specifically recognize tumor cells has attracted much research and clinical trial interest. In this review, we discuss the historical background of tumor immunotherapy using cell-based approaches, and provide some rationale for overcoming current barriers to success of autologous immunotherapy. An overview of adoptive transfer of lymphocytes, tumor infiltrating lymphocytes and dendritic cell therapies is provided. We conclude with discussing the possibility of gene-manipulating immune cells in order to augment therapeutic activity, including silencing of the immune-suppressive zinc finger orphan nuclear receptor, NR2F6, as an attractive means of overcoming tumor-associated immune suppression.

Emerging immunotherapies for glioblastoma

INTRODUCTION

Immunotherapy for brain cancer has evolved dramatically over the past decade, owed in part to our improved understanding of how the immune system interacts with tumors residing within the central nervous system (CNS). Glioblastoma (GBM), the most common primary malignant brain tumor in adults, carries a poor prognosis (<15 months) and only few advances have been made since the FDA's approval of temozolomide (TMZ) in 2005. Importantly, several immunotherapies have now entered patient trials based on promising preclinical data, and recent studies have shed light on how GBM employs a slew of immunosuppressive mechanisms that may be targeted for therapeutic gain. Altogether, accumulating evidence suggests immunotherapy may soon earn its keep as a mainstay of clinical management for GBM.

AREAS COVERED

Here, we review cancer vaccines, checkpoint inhibitors, adoptive T-cell immunotherapy, and oncolytic virotherapy.

EXPERT OPINION

Checkpoint blockade induces antitumor activity by preventing negative regulation of T-cell activation. This platform, however, depends on an existing frequency of tumor-reactive T cells. GBM tumors are exceptionally equipped to prevent this, occupying low levels of antigen expression and elaborate mechanisms of immunosuppression. Therefore, checkpoint blockade may be most effective when used in combination with a DC vaccine or adoptively transferred tumor-specific T cells generated ex vivo. Both approaches have been shown to induce endogenous immune responses against tumor antigens, providing a rationale for use with checkpoint blockade where both primary and secondary responses may be potentiated.

A phase II trial of autologous dendritic cell vaccination and radiochemotherapy following fluorescence-guided surgery in newly diagnosed glioblastoma patients

Background

Prognosis of patients with glioblastoma multiforme (GBM) remains dismal, with median overall survival (OS) of about 15 months. It is therefore crucial to search alternative strategies that improve these results obtained with conventional treatments. In this context, immunotherapy seems to be a promising therapeutic option. We hypothesized that the addition of tumor lysate-pulsed autologous dendritic cells (DCs) vaccination to maximal safe resection followed by radiotherapy and concomitant and adjuvant temozolomide could improve patients’ survival.

Methods

We conducted a phase-II clinical trial of autologous DCs vaccination in patients with newly diagnosed patients GBM who were candidates to complete or near complete resection. Candidates were finally included if residual tumor volume was lower than 1 cc on postoperative radiological examination. Autologous DCs were generated from peripheral blood monocytes and pulsed with autologous whole tumor lysate. The vaccination calendar started before radiotherapy and was continued during adjuvant chemotherapy. Progression free survival (PFS) and OS were analyzed with the Kaplan–Meier method. Immune response were assessed in blood samples obtained before each vaccines.

Results

Thirty-two consecutive patients were screened, one of which was a screening failure due to insufficient resection. Median age was 61 years (range 42–70). Karnofsky performance score (KPS) was 90–100 in 29%, 80 in 35.5% and 60–70 in 35.5% of cases. MGMT (O⁶-methylguanine-DNA-methyltransferase) promoter was methylated in 45.2% of patients. No severe adverse effects related to immunotherapy were registered. Median PFS was 12.7 months (CI 95% 7–16) and median OS was 23.4 months (95% CI 16–33.1). Increase in post-vaccination tumor specific immune response after vaccines (proliferation or cytokine production) was detected in 11/27 evaluated patients. No correlation between immune response and survival was found.

Conclusions

Our results suggest that the addition of tumor lysate-pulsed autologous DCs vaccination to tumor resection and combined radio-chemotherapy is feasible and safe. A multicenter randomized clinical trial is warranted to evaluate the potential survival benefit of this therapeutic approach.

Trial registration This phase-II trial was registered as EudraCT: 2009-009879-35 and ClinicalTrials.gov Identifier: NCT01006044 retrospectively registered

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1202-z) contains supplementary material, which is available to authorized users.

History and current state of immunotherapy in glioma and brain metastasis

Malignant brain tumors such as glioblastoma (GBM) and brain metastasis have poor prognosis despite conventional therapies. Successful use of vaccines and checkpoint inhibitors in systemic malignancy has increased the hope that immune therapies could improve survival in patients with brain tumors. Manipulating the immune system to fight malignancy has a long history of both modest breakthroughs and pitfalls that should be considered when applying the current immunotherapy approaches to patients with brain tumors. Therapeutic vaccine trials for GBM date back to the mid 1900s and have taken many forms; from irradiated tumor lysate to cell transfer therapies and peptide vaccines. These therapies were generally well tolerated without significant autoimmune toxicity, however also did not demonstrate significant clinical benefit. In contrast, the newer checkpoint inhibitors have demonstrated durable benefit in some metastatic malignancies, accompanied by significant autoimmune toxicity. While this toxicity was not unexpected, it exceeded what was predicted from pre-clinical studies and in many ways was similar to the prior trials of immunostimulants. This review will discuss the history of these studies and demonstrate that the future use of immune therapy for brain tumors will likely need a personalized approach that balances autoimmune toxicity with the opportunity for significant survival benefit.

Dendritic cell based vaccination strategy: an evolving paradigm

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

Tumor Vaccines for Malignant Gliomas

Despite continued research efforts, glioblastoma multiforme (GBM) remains the deadliest brain tumor. Immunotherapy offers a novel way to treat this disease, the genetic signature of which is not completely elucidated. Additionally, these tumors are known to induce immunosuppression in the surrounding tumor microenvironment via an array of mechanisms, making effective treatment all the more difficult. The immunotherapeutic strategy of using tumor vaccines offers a way to harness the activity of the host immune system to potentially control tumor progression. GBM vaccines can react to a variety of tumor-specific antigens, which can be harvested from the patient's unique pathological condition using selected immunotherapy techniques. This article reviews the rationale behind and development of GBM vaccines, the relevant clinical trials, and the challenges involved in this treatment strategy.

Immune infiltration of tumor microenvironment following immunotherapy for glioblastoma multiforme

Autologous dentritic cell immunotherapy has been proven effective in treating tumors outside the central nervous system. Current evidence from phase I and II trials suggest a similar efficacy for central nervous system tumors as well and that an active immune response against these tumors can be generated. We aim to review the literature to identify the types of immune responses against gliomas found to be generated by dendritic cell vaccinations and the types of immune cells subsequently infiltrating the glioma microenvironment. A systematic review of the literature was performed by searching the online databases PubMEd, Google Scholar, and EMBASE with use of the keywords intratumoral, infiltration, lymphocytic, vaccination and gliomas. Seven studies reporting lymphocytic infiltration of gliomas microenvironment were identified. Three studies (42.8%) reported presence of tumor infiltrating lymphocytes in 50%, 50% and 28.6% of included patients respectively in the post-vaccination specimens that were not present in the pre-vaccination samples. The remaining 4 (57.2%) reported an up to 6-fold increase in the number of pre-existing lymphocytes following vaccination. Present data indicate that tumor infiltration by lymphocytes can be induced by dentritic cell immunotherapy and that this may positively affect clinical outcome. It still remains unclear which factors influence the above reaction and therefore prediction of response to treatment is still not possible.

Immunological Aspects of Malignant Gliomas

Glioblastoma Multiforme (GBM) is the most common malignant primary brain neoplasm having a mean survival time of <24 months. This figure remains constant, despite significant progress in medical research and treatment. The lack of an efficient anti-tumor immune response and the micro-invasive nature of the glioma malignant cells have been explained by a multitude of immune-suppressive mechanisms, proven in different models. These immune-resistant capabilities of the tumor result in a complex interplay this tumor shares with the immune system. We present a short review on the immunology of GBM, discussing the different unique pathological and molecular features of GBM, current treatment modalities, the principles of cancer immunotherapy and the link between GBM and melanoma. Current knowledge on immunological features of GBM, as well as immunotherapy past and current clinical trials, is discussed in an attempt to broadly present the complex and formidable challenges posed by GBM.

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.

The inflammatory cytokine IL-22 promotes murine gliomas via proliferation

Interleukin (IL)-22 is newly identified proinflammatory cytokine involved in the T helper (Th)17 and Th22 response. However, the possible role of IL-22 in glioma remains uncertain. The results of the present study demonstrated higher expression levels of IL-22 and the receptor IL-22BP in the brain of GL261 glioma-inoculation mice, suggesting the regulatory role of IL-22 in glioma. Injection of IL-22 increased the severity of glioma in vivo and higher expression levels of IL-6, IL-1β and tumor necrosis factor (TNF)-α were detected in the brain using ELISA following IL-22 injection. To elucidate the mechanism underlying the effects of IL-22, the present study aimed firstly to determine the expression levels of IL-22 receptor in a glioma cell line via reverse transcription quantitative polymerase chain reaction. IL-22 treatment significantly increased the expression levels of signal transducer and activator of transcription (STAT)3 and the mRNA expression levels of STAT6 compared with the vehicle control. These results suggested that IL-22 may activate the Janus kinase (JAK)/STAT signaling pathway in glioma. Furthermore, IL-22 positively regulated the proliferation of glioma, consistent with its role in vivo. Conversely, IL-22-deficient mice exhibited prolonged survival compared with wild-type (WT) mice, and the expression levels of inflammatory cytokines were decreased in the brain of IL-22 knock-out (KO) mice compared with WT mice. Concordant with these results, it was observed that IL-22-neutralising antibody was able to increase the survival of mice with glioma and attenuate the disease by significantly reducing the cytokine levels in the brain. In conclusion, the results of the present study demonstrated that expression levels of IL-22 in the brain of mice with glioma may enhance symptoms due to the increased cytokine production of IL-6, IL-1β and TNF-α; this is consistent with IL-6/JAK/STAT signalling activation in vitro. Decreasing the expression levels of IL-22, achieved either with IL-22-KO mice or IL-22-neutralising antibody demonstrated protective effects on glioma development. Therefore, IL-22 may serve as a potential therapeutic target for glioma.

The Safety of available immunotherapy for the treatment of glioblastoma

INTRODUCTION

Glioblastoma (GBM) is the most common malignant primary brain tumor in adults. Current standard of care involves maximal surgical resection combined with adjuvant chemoradiation. Growing support exists for a role of immunotherapy in treating these tumors with the goal of targeted cytotoxicity. Here we review data on the safety for current immunotherapies being tested in GBM. Areas covered: Safety data from published clinical trials, including ongoing clinical trials were reviewed. Immunotherapeutic classes currently under investigation in GBM include various vaccination strategies, adoptive T cell immunotherapy, immune checkpoint blockade, monoclonal antibodies, and cytokine therapies. Trials include children, adolescents, and adults with either primary or recurrent GBM. Expert opinion: Based on the reviewed clinical trials, the current immunotherapies targeting GBM are safe and well-tolerated with minimal toxicities which should be noted. However, the gains in patient survival have been modest. A safe and well-tolerated combinatory immunotherapeutic approach may be essential for optimal efficacy towards GBM.

Recent advances and future of immunotherapy for glioblastoma

INTRODUCTION

Outcome for glioma (GBM) remains dismal despite advances in therapeutic interventions including chemotherapy, radiotherapy and surgical resection. The overall survival benefit observed with immunotherapies in cancers such as melanoma and prostate cancer has fuelled research into evaluating immunotherapies for GBM.

AREAS COVERED

Preclinical studies have brought a wealth of information for improving the prognosis of GBM and multiple clinical studies are evaluating a wide array of immunotherapies for GBM patients. This review highlights advances in the development of immunotherapeutic approaches. We discuss the strategies and outcomes of active and passive immunotherapies for GBM including vaccination strategies, gene therapy, check point blockade and adoptive T cell therapies. We also focus on immunoediting and tumor neoantigens that can impact the efficacy of immunotherapies.

EXPERT OPINION

Encouraging results have been observed with immunotherapeutic strategies; some clinical trials are reaching phase III. Significant progress has been made in unraveling the molecular and genetic heterogeneity of GBM and its implications to disease prognosis. There is now consensus related to the critical need to incorporate tumor heterogeneity into the design of therapeutic approaches. Recent data also indicates that an efficacious treatment strategy will need to be combinatorial and personalized to the tumor genetic signature.

Antigen-specific immunoreactivity and clinical outcome following vaccination with glioma-associated antigen peptides in children with recurrent high-grade gliomas: results of a pilot study

Recurrent high-grade gliomas (HGGs) of childhood have an exceedingly poor prognosis with current therapies. Accordingly, new treatment approaches are needed. We initiated a pilot trial of vaccinations with peptide epitopes derived from glioma-associated antigens (GAAs) overexpressed in these tumors in HLA-A2+ children with recurrent HGG that had progressed after prior treatments. Peptide epitopes for three GAAs (EphA2, IL13Rα2, survivin), emulsified in Montanide-ISA-51, were administered subcutaneously adjacent to intramuscular injections of poly-ICLC every 3 weeks for 8 courses, followed by booster vaccines every 6 weeks. Primary endpoints were safety and T-cell responses against the GAA epitopes, assessed by enzyme-linked immunosorbent spot (ELISPOT) analysis. Treatment response was evaluated clinically and by magnetic resonance imaging. Twelve children were enrolled, 6 with glioblastoma, 5 with anaplastic astrocytoma, and one with malignant gliomatosis cerebri. No dose-limiting non-CNS toxicity was encountered. ELISPOT analysis, in ten children, showed GAA responses in 9: to IL13Rα2 in 4, EphA2 in 9, and survivin in 3. One child had presumed symptomatic pseudoprogression, discontinued vaccine therapy, and responded to subsequent treatment. One other child had a partial response that persisted throughout 2 years of vaccine therapy, and continues at >39 months. Median progression-free survival (PFS) from the start of vaccination was 4.1 months and median overall survival (OS) was 12.9 months. 6-month PFS and OS were 33 and 73 %, respectively. GAA peptide vaccination in children with recurrent malignant gliomas is generally well tolerated, and has preliminary evidence of immunological and modest clinical activity.

Immunotherapy for neuro-oncology: the critical rationale for combinatorial therapy

A successful therapeutic paradigm established historically in oncology involves combining agents with potentially complementary mechanisms of antitumor activity into rationally designed regimens. For example, cocktails of cytotoxic agents, which were carefully designed based on mechanisms of action, dose, and scheduling considerations, have led to dramatic improvements in survival including cures for childhood leukemia, Hodgkin's lymphoma, and several other complex cancers. Outcome for glioblastoma, the most common primary malignant CNS cancer, has been more modest, but nonetheless our current standard of care derives from confirmation that combination therapy surpasses single modality therapy. Immunotherapy has recently come of age for medical oncology with exciting therapeutic benefits achieved by several types of agents including vaccines, adoptive T cells, and immune checkpoint inhibitors against several types of cancers. Nonetheless, most benefits are relatively short, while others are durable but are limited to a minority of treated patients. Critical factors limiting efficacy of immunotherapeutics include insufficient immunogenicity and/or inadequate ability to overcome immunosuppressive factors exploited by tumors. The paradigm of rationally designed combinatorial regimens, originally established by cytotoxic therapy for oncology, may also prove relevant for immunotherapy. Realization of the true therapeutic potential of immunotherapy for medical oncology and neuro-oncology patients may require development of combinatorial regimens that optimize immunogenicity and target tumor adaptive immunosuppressive factors.

Vaccination strategies for neuro-oncology

Vaccination against cancer-associated antigens has long held the promise of inducting potent antitumor immunity, targeted cytotoxicity while sparing normal tissues, and long-lasting immunologic memory that can provide surveillance against tumor recurrence. Evaluation of vaccination strategies in preclinical brain tumor models has borne out the capacity for the immune system to effectively and safely eradicate established tumors within the central nervous system. Early phase clinical trials have established the feasibility, safety, and immunogenicity of several vaccine platforms, predominantly in patients with glioblastoma. Definitive demonstration of clinical benefit awaits further study, but initial results have been encouraging. With increased understanding of the stimulatory and regulatory pathways that govern immunologic responses and the enhanced capacity to identify novel antigenic targets using genomic interrogation of tumor cells, vaccination platforms for patients with malignant brain tumors are advancing with increasing personalized complexity and integration into combinatorial treatment paradigms.

CD8 T Cell-Independent Antitumor Response and Its Potential for Treatment of Malignant Gliomas

Malignant brain tumors continue to represent a devastating diagnosis with no real chance for cure. Despite an increasing list of potential salvage therapies, standard-of-care for these patients has not changed in over a decade. Immunotherapy has been seen as an exciting option, with the potential to offer specific and long lasting tumor clearance. The “gold standard” in immunotherapy has been the development of a tumor-specific CD8 T cell response to potentiate tumor clearance and immunological memory. While many advances have been made in the field of immunotherapy, few therapies have seen true success. Many of the same principles used to develop immunotherapy in tumors of the peripheral organs have been applied to brain tumor immunotherapy. The immune-specialized nature of the brain should call into question whether this approach is appropriate. Recent results from our own experiments require a rethinking of current dogma. Perhaps a CD8 T cell response is not sufficient for an organ as immunologically unique as the brain. Examination of previously elucidated principles of the brain’s immune-specialized status and known immunological preferences should generate discussion and experimentation to address the failure of current therapies.

Past, present and forecast of transfusion medicine: What has changed and what is expected to change?

Blood transfusion is the second most used medical procedures in health care systems worldwide. Over the last few decades, significant changes have been evolved in transfusion medicine practices. These changes were mainly needed to increase safety, efficacy, and availability of blood products as well as reduce recipients' unnecessary exposure to allogeneic blood. Blood products collection, processing, and storage as well as transfusion practices throughout all patient populations were the main stream of these changes. Health care systems across the world have adopted some or most of these changes to reduce transfusion risks, to improve overall patients' outcome, and to reduce health care costs. In this article, we are going to present and discuss some of these recent modifications and their impact on patients' safety.

Tumor antigen-specific T cells for immune monitoring of dendritic cell-treated glioblastoma patients

BACKGROUND AIMS

CD8(+) T cells are part of the adaptive immune system and, as such, are responsible for the elimination of tumor cells. Dendritic cells (DC) are professional antigen-presenting cells (APC) that activate CD8(+) T cells. Effector CD8(+) T cells in turn mediate the active immunotherapeutic response of DC vaccination against the aggressive glioblastoma (GBM). The lack of tumor response assays complicates the assessment of treatment success in GBM patients.

METHODS

A novel assay to identify specific cytotoxicity of activated T cells by APC was evaluated. Tumor antigen-pulsed DCs from HLA-A*02-positive GBM patients were cultivated to stimulate autologous cytotoxic T lymphocytes (CTL) over a 12-day culture period. To directly correlate antigen specificity and cytotoxic capacity, intracellular interferon (IFN)-γ fluorescence flow cytometry-based measurements were combined with anti-GBM tumor peptide dextramer staining. IFN-γ response was quantified by real-time polymerase chain reaction (PCR), and selected GBM genes were compared with healthy human brain cDNA by single specific primer PCR characterization.

RESULTS

Using CTL of GBM patients stimulated with GBM lysate-pulsed DCs increased IFN-γ messenger RNA levels, and intracellular IFN-γ protein expression was positively correlated with specificity against GBM antigens. Moreover, the GBM peptide-specific CD8(+) T-cell response correlated with specific GBM gene expression. Following DC vaccination, GBM patients showed 10-fold higher tumor-specific signals compared with unvaccinated GBM patients.

DISCUSSION

These data indicate that GBM tumor peptide-dextramer staining of CTL in combination with intracellular IFN-γ staining may be a useful tool to acquire information on whether a specific tumor antigen has the potential to induce an immune response in vivo.

PD-1 blockade enhances the vaccination-induced immune response in glioma

DC vaccination with autologous tumor lysate has demonstrated promising results for the treatment of glioblastoma (GBM) in preclinical and clinical studies. While the vaccine appears capable of inducing T cell infiltration into tumors, the effectiveness of active vaccination in progressively growing tumors is less profound. In parallel, a number of studies have identified negative costimulatory pathways, such as programmed death 1/programmed death ligand 1 (PD-1/PD-L1), as relevant mediators of the intratumoral immune responses. Clinical responses to PD-1 pathway inhibition, however, have also been varied. To evaluate the relevance to established glioma, the effects of PD-1 blockade following DC vaccination were tested in intracranial (i.c.) glioma tumor- bearing mice. Treatment with both DC vaccination and PD-1 mAb blockade resulted in long-term survival, while neither agent alone induced a survival benefit in animals with larger, established tumors. This survival benefit was completely dependent on CD8⁺ T cells. Additionally, DC vaccine plus PD-1 mAb blockade resulted in the upregulation of integrin homing and immunologic memory markers on tumor-infiltrating lymphocytes (TILs). In clinical samples, DC vaccination in GBM patients was associated with upregulation of PD-1 expression in vivo, while ex vivo blockade of PD-1 on freshly isolated TILs dramatically enhanced autologous tumor cell cytolysis. These findings strongly suggest that the PD-1/PD-L1 pathway plays an important role in the adaptive immune resistance of established GBM in response to antitumor active vaccination and provide us with a rationale for the clinical translation of this combination therapy.

Review of hematological indices of cancer patients receiving combined chemotherapy & radiotherapy or receiving radiotherapy alone

We observed the outcomes of chemotherapy with radiotherapy (CR) or radiotherapy (RT) alone for cancer patients of larynx, breast, blood and brain origins through complete blood count (CBC). Following were more depressed in CR patients: mean corpuscular hemoglobin-MCH & lymphocytes-LYM, hematocrit, mean corpuscular hemoglobin concentration-MCHC, hemoglobin-HB and red blood cells-RBC. In RT patients, following were more depressed: LYM, MCH and MCHC. Overall, in all cancer patients, the lymphocytes were depressed 52%. There existed a significant difference between white blood cells and RBC in both CR and RT patients. A significant moderate negative correlation is found in HB with the dose range 30-78 (Gray) given to the CR cancer patients. More number of CBC parameters affected in patients treated with CR and RT; but in less percentage as compared to patients who treated with RT alone. The cancer patients suffered from anemia along with immune modulations from the treatments.

Improving vaccine efficacy against malignant glioma

The effective treatment of adult and pediatric malignant glioma is a significant clinical challenge. In adults, glioblastoma (GBM) accounts for the majority of malignant glioma diagnoses with a median survival of 14.6 mo. In children, malignant glioma accounts for 20% of primary CNS tumors with a median survival of less than 1 y. Here, we discuss vaccine treatment for children diagnosed with malignant glioma, through targeting EphA2, IL-13Rα2 and/or histone H3 K27M, while in adults, treatments with RINTEGA, Prophage Series G-100 and dendritic cells are explored. We conclude by proposing new strategies that are built on current vaccine technologies and improved upon with novel combinatorial approaches.

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.

Investigational new drugs for brain cancer

INTRODUCTION

Despite substantial improvements in standards of care, the most common aggressive pediatric and adult high-grade gliomas (HGG) carry uniformly fatal diagnoses due to unique treatment limitations, high recurrence rates and the absence of effective treatments following recurrence. Recent advancements in our understanding of the pathophysiology, genetics and epigenetics as well as mechanisms of immune surveillance during gliomagenesis have created new knowledge to design more effective and target-directed therapies to improve patient outcomes.

AREAS COVERED

In this review, the authors discuss the critical genetic, epigenetic and immunologic aberrations found in gliomas that appear rational and promising for therapeutic developments in the presence and future. The current state of the latest therapeutic developments including tumor-specific targeted drug therapies, metabolic targeting, epigenetic modulation and immunotherapy are summarized and suggestions for future directions are offered. Furthermore, they highlight contemporary issues related to the clinical development, such as challenges in clinical trials and toxicities.

EXPERT OPINION

The commitment to understanding the process of gliomagenesis has created a catalogue of aberrations that depict multiple mechanisms underlying this disease, many of which are suitable to therapeutic inhibition and are currently tested in clinical trials. Thus, future treatment endeavors will employ multiple treatment modalities that target disparate tumor characteristics personalized to the patient's individual tumor.

Immune responses and outcome after vaccination with glioma-associated antigen peptides and poly-ICLC in a pilot study for pediatric recurrent low-grade gliomas

BACKGROUND

Low-grade gliomas (LGGs) are the most common brain tumors of childhood. Although surgical resection is curative for well-circumscribed superficial lesions, tumors that are infiltrative or arise from deep structures are therapeutically challenging, and new treatment approaches are needed. Having identified a panel of glioma-associated antigens (GAAs) overexpressed in these tumors, we initiated a pilot trial of vaccinations with peptides for GAA epitopes in human leukocyte antigen-A2+ children with recurrent LGG that had progressed after at least 2 prior regimens.

METHODS

Peptide epitopes for 3 GAAs (EphA2, IL-13Rα2, and survivin) were emulsified in Montanide-ISA-51 and administered subcutaneously adjacent to intramuscular injections of polyinosinic-polycytidylic acid stabilized by lysine and carboxymethylcellulose every 3 weeks for 8 courses, followed by booster vaccines every 6 weeks. Primary endpoints were safety and T-lymphocyte responses against GAA epitopes. Treatment response was evaluated clinically and by MRI.

RESULTS

Fourteen children were enrolled. Other than grade 3 urticaria in one child, no regimen-limiting toxicity was encountered. Vaccination induced immunoreactivity to at least one vaccine-targeted GAA in all 12 evaluable patients: to IL-13Rα2 in 3, EphA2 in 11, and survivin in 3. One child with a metastatic LGG had asymptomatic pseudoprogression noted 6 weeks after starting vaccination, followed by dramatic disease regression with >75% shrinkage of primary tumor and regression of metastatic disease, persisting >57 months. Three other children had sustained partial responses, lasting >10, >31, and >45 months, and one had a transient response.

CONCLUSIONS

GAA peptide vaccination in children with recurrent LGGs is generally well tolerated, with preliminary evidence of immunological and clinical activity.

Prioritization schema for immunotherapy clinical trials in glioblastoma

BACKGROUND

Emerging immunotherapeutic strategies for the treatment of glioblastoma (GBM) such as dendritic cell (DC) vaccines, heat shock proteins, peptide vaccines, and adoptive T-cell therapeutics, to name a few, have transitioned from the bench to clinical trials. With upcoming strategies and developing therapeutics, it is challenging to critically evaluate the practical, clinical potential of individual approaches and to advise patients on the most promising clinical trials.

METHODS

The authors propose a system to prioritize such therapies in an organized and data-driven fashion. This schema is based on four categories of factors: antigenic target robustness, immune-activation and -effector responses, preclinical vetting, and early evidence of clinical response. Each of these categories is subdivided to focus on the most salient elements for developing a successful immunotherapeutic approach for GBM, and a numerical score is generated.

RESULTS

The Score Card reveals therapeutics that have the most robust data to support their use, provides a reference prioritization score, and can be applied in a reiterative fashion with emerging data.

CONCLUSIONS

The authors hope that this schema will give physicians an evidence-based and rational framework to make the best referral decisions to better guide and serve this patient population.

Stress Response Leading to Resistance in Glioblastoma-The Need for Innovative Radiotherapy (iRT) Concepts

Glioblastoma (GBM) is the most common and most aggressive malignant primary brain tumor in adults. In spite of multimodal therapy concepts, consisting of surgery, radiotherapy and chemotherapy, the median survival, merely 15–18 months, is still poor. Mechanisms for resistance of GBM to radio(chemo)therapy are not fully understood yet and due to the genetic heterogeneity within the tumor including radiation-resistant tumor stem cells, there are several factors leading to therapy failure. Recent research revealed that, hypoxia during radiation and miRNAs may adversely affect the therapeutic response to radiotherapy. Further molecular alterations and prognostic markers like the DNA-repair protein O6-methylguanine-DNA methyltransferase (MGMT), anti-apoptotic molecular chaperones, and/or the activity of aldehyde dehydrogenase 1 (ALDH1) have also been identified to play a role in the sensitivity to cytostatic agents. Latest approaches in the field of radiotherapy to use particle irradiation or dose escalation strategies including modern molecular imaging, however, need further evaluation with regard to long-term outcome. In this review we focus on current information about the mechanisms and markers that mediate resistance to radio(chemo)therapy, and discuss the opportunities of Innovative Radiotherapy (iRT) concepts to improve treatment options for GBM patients.

Immunotherapy with dendritic cells loaded with glioblastoma stem cells: from preclinical to clinical studies

Different approaches have been explored to raise effective antitumor responses against glioblastoma (GBM), the deadliest of primary brain tumors. In many clinical studies, cancer vaccines have been based on dendritic cells (DCs) loaded with peptides, representing one or more specific tumor antigens or whole lysates as a source of multiple antigens. Randomized clinical trials using DCs are ongoing, and results of efficacy are not yet available. Such strategies are feasible and safe; however, immune-suppressive microenvironment, absence of appropriate specific epitopes to target, and cancer immunoediting can limit their efficacy. The aim of this review is to describe how the definition of novel and more specific targets may increase considerably the possibility of successful DC immunotherapy. By proposing to target glioblastoma stem-like cells (GSCs), the immune response will be pointed to eradicating factors and pathways highly relevant to GBM biology. Preclinical observations on efficacy, and preliminary results of immunotherapy trials, encourage exploring the clinical efficacy of DC immunotherapy in GBM patients using high-purity, GSC-loaded DC vaccines.

Principles of immunotherapy

Gliomas are the most common primary brain tumors of the central nervous system, and carry a grim prognosis. Novel approaches utilizing the immune system as adjuvant therapy are quickly emerging as viable and effective options. Immunotherapeutic strategies being investigated to treat glioblastoma include: vaccination therapy targeted against either specific tumor antigens or whole tumor lysate, adoptive cellular therapy with cytotoxic T lymphocytes, chimeric antigen receptors and bi-specific T-cell engaging antibodies allowing circumvention of major histocompatibility complex restriction, aptamer therapy with aims for more efficient target delivery, and checkpoint blockade in order to release the tumor-mediated inhibition of the immune system. Given the heterogeneity of glioblastoma and its ability to gain mutations throughout the disease course, multifaceted treatment strategies utilizing multiple forms of immunotherapy in combination with conventional therapy will be most likely to succeed moving forward.

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.

DCVax®-L--developed by Northwest Biotherapeutics

Dendritic cell (DC) immunotherapy is emerging as a potential addition to the standard of care in the treatment of glioblastoma multiforme (GBM). In the last decade or so various research groups have conducted phase I and II trials of DC-immunotherapy on patients with newly diagnosed (ND) and recurrent GBM and other high-grade gliomas in an attempt to improve the poor prognosis. Results show an increase in overall survival (OS), while vaccination-related side effects are invariably mild. Northwest Biotherapeutics, Inc., Bethesda, Maryland, U.S.A. (NWBT) developed the DCVax®-L vaccine as an adjunct to the treatment of GBM. It is currently under evaluation in a phase III trial in patients with ND-GBM, which is the only ongoing trial of its kind. In this review current data and perspectives of this product are examined.

Efficacy of systemic adoptive transfer immunotherapy targeting NY-ESO-1 for glioblastoma

BACKGROUND

Immunotherapy is an ideal treatment modality to specifically target the diffusely infiltrative tumor cells of malignant gliomas while sparing the normal brain parenchyma. However, progress in the development of these therapies for glioblastoma has been slow due to the lack of immunogenic antigen targets that are expressed uniformly and selectively by gliomas.

METHODS

We utilized human glioblastoma cell cultures to induce expression of New York-esophageal squamous cell carcinoma (NY-ESO-1) following in vitro treatment with the demethylating agent decitabine. We then investigated the phenotype of lymphocytes specific for NY-ESO-1 using flow cytometry analysis and cytotoxicity against cells treated with decitabine using the xCelligence real-time cytotoxicity assay. Finally, we examined the in vivo application of this immune therapy using an intracranially implanted xenograft model for in situ T cell trafficking, survival, and tissue studies.

RESULTS

Our studies showed that treatment of intracranial glioma-bearing mice with decitabine reliably and consistently induced the expression of an immunogenic tumor-rejection antigen, NY-ESO-1, specifically in glioma cells and not in normal brain tissue. The upregulation of NY-ESO-1 by intracranial gliomas was associated with the migration of adoptively transferred NY-ESO-1-specific lymphocytes along white matter tracts to these tumors in the brain. Similarly, NY-ESO-1-specific adoptive T cell therapy demonstrated antitumor activity after decitabine treatment and conferred a highly significant survival benefit to mice bearing established intracranial human glioma xenografts. Transfer of NY-ESO-1-specific T cells systemically was superior to intracranial administration and resulted in significantly extended and long-term survival of animals.

CONCLUSION

These results reveal an innovative, clinically feasible strategy for the treatment of glioblastoma.

Personalized approaches to active immunotherapy in cancer

Immunotherapy is emerging as a promising anti-cancer curative modality. However, in contrast to recent advances obtained employing checkpoint blockade agents and T cell therapies, clinical efficacy of therapeutic cancer vaccines is still limited. Most vaccination attempts in the clinic represent "off-the shelf" approaches since they target common "self" tumor antigens, shared among different patients. In contrast, personalized approaches of vaccination are tailor-made for each patient and in spite being laborious, hold great potential. Recent technical advancement enabled the first steps in the clinic of personalized vaccines that target patient-specific mutated neo-antigens. Such vaccines could induce enhanced tumor-specific immune response since neo-antigens are mutation-derived antigens that can be recognized by high affinity T cells, not limited by central tolerance. Alternatively, the use of personalized vaccines based on whole autologous tumor cells, overcome the need for the identification of specific tumor antigens. Whole autologous tumor cells could be administered alone, pulsed on dendritic cells as lysate, DNA, RNA or delivered to dendritic cells in-vivo through encapsulation in nanoparticle vehicles. Such vaccines may provide a source for the full repertoire of the patient-specific tumor antigens, including its private neo-antigens. Furthermore, combining next-generation personalized vaccination with other immunotherapy modalities might be the key for achieving significant therapeutic outcome.

Challenges and future perspectives of T cell immunotherapy in cancer

Since the formulation of the tumour immunosurveillance theory, considerable focus has been on enhancing the effectiveness of host antitumour immunity, particularly with respect to T cells. A cancer evades or alters the host immune response by various ways to ensure its development and survival. These include modifications of the immune cell metabolism and T cell signalling. An inhibitory cytokine milieu in the tumour microenvironment also leads to immune suppression and tumour progression within a host. This review traces the development in the field and attempts to summarize the hurdles that the approach of adoptive T cell immunotherapy against cancer faces, and discusses the conditions that must be improved to allow effective eradication of cancer.