A pilot study of IL-2Rα blockade during lymphopenia depletes regulatory T-cells and correlates with enhanced immunity in patients with glioblastoma

Antisense targeting of FOXP3+ Tregs to boost anti-tumor immunity

Our goal is to improve the outcomes of cancer immunotherapy by targeting FOXP3+ T-regulatory (Treg) cells with a next generation of antisense oligonucleotides (ASO), termed FOXP3 AUMsilence ASO. We performed in vitro experiments with human healthy donor PBMC and clinical samples from patients with lung cancer, mesothelioma and melanoma, and tested our approach in vivo using ASO FOXP3 in syngeneic murine cancer models and in humanized mice. ASO FOXP3 had no effects on cell viability or cell division, did not affect expression of other FOXP members, but decreased expression of FOXP3 mRNA in PBMC by 54.9% and in cancer samples by 64.7%, with corresponding 41.0% (PBMC) and 60.0% (cancer) decreases of Treg numbers (all p<0.0001). Hence, intratumoral Treg were more sensitive to the effects of ASO FOXP3 than peripheral blood Tregs. Isolated human Treg, incubated with ASO FOXP3 for 3.5 hours, had significantly impaired suppressive function (66.4%) versus Scramble control. In murine studies, we observed a significant inhibition of tumor growth, while 13.6% (MC38) to 22% (TC1) of tumors were completely resorbed, in conjunction with ~50% decrease of Foxp3 mRNA by qPCR and decreased numbers of intratumoral Tregs. In addition, there were no changes in FOXP3 mRNA expression or in the numbers of Tregs in draining lymph nodes and in spleens of tumor bearing mice, confirming that intratumoral Treg had enhanced sensitivity to ASO FOXP3 in vivo compared to other Treg populations. ASO FOXP3 Treg targeting in vivo and in vitro was accompanied by significant downregulation of multiple exhaustion markers, and by increased expression of perforin and granzyme-B by intratumoral T cells. To conclude, we report that targeting the key Treg transcription factor FOXP3, with ASO FOXP3, has a powerful anti-tumoral effect and enhances T cell response in vitro and in vivo.

Immunotherapeutic Strategies for the Treatment of Glioblastoma: Current Challenges and Future Perspectives

Despite decades of research and the best up-to-date treatments, grade 4 Glioblastoma (GBM) remains uniformly fatal with a patient median overall survival of less than 2 years. Recent advances in immunotherapy have reignited interest in utilizing immunological approaches to fight cancer. However, current immunotherapies have so far not met the anticipated expectations, achieving modest results in their journey from bench to bedside for the treatment of GBM. Understanding the intrinsic features of GBM is of crucial importance for the development of effective antitumoral strategies to improve patient life expectancy and conditions. In this review, we provide a comprehensive overview of the distinctive characteristics of GBM that significantly influence current conventional therapies and immune-based approaches. Moreover, we present an overview of the immunotherapeutic strategies currently undergoing clinical evaluation for GBM treatment, with a specific emphasis on those advancing to phase 3 clinical studies. These encompass immune checkpoint inhibitors, adoptive T cell therapies, vaccination strategies (i.e., RNA-, DNA-, and peptide-based vaccines), and virus-based approaches. Finally, we explore novel innovative strategies and future prospects in the field of immunotherapy for GBM.

Targeting inflammation as cancer therapy

Inflammation has accompanied human beings since the emergence of wounds and infections. In the past decades, numerous efforts have been undertaken to explore the potential role of inflammation in cancer, from tumor development, invasion, and metastasis to the resistance of tumors to treatment. Inflammation-targeted agents not only demonstrate the potential to suppress cancer development, but also to improve the efficacy of other therapeutic modalities. In this review, we describe the highly dynamic and complex inflammatory tumor microenvironment, with discussion on key inflammation mediators in cancer including inflammatory cells, inflammatory cytokines, and their downstream intracellular pathways. In addition, we especially address the role of inflammation in cancer development and highlight the action mechanisms of inflammation-targeted therapies in antitumor response. Finally, we summarize the results from both preclinical and clinical studies up to date to illustrate the translation potential of inflammation-targeted therapies.

Acquisition of suppressive function by conventional T cells limits antitumor immunity upon Treg depletion

Regulatory T (Treg) cells contribute to immune homeostasis but suppress immune responses to cancer. Strategies to disrupt Treg cell-mediated cancer immunosuppression have been met with limited clinical success, but the underlying mechanisms for treatment failure are poorly understood. By modeling Treg cell-targeted immunotherapy in mice, we find that CD4+ Foxp3- conventional T (Tconv) cells acquire suppressive function upon depletion of Foxp3+ Treg cells, limiting therapeutic efficacy. Foxp3- Tconv cells within tumors adopt a Treg cell-like transcriptional profile upon ablation of Treg cells and acquire the ability to suppress T cell activation and proliferation ex vivo. Suppressive activity is enriched among CD4+ Tconv cells marked by expression of C-C motif receptor 8 (CCR8), which are found in mouse and human tumors. Upon Treg cell depletion, CCR8+ Tconv cells undergo systemic and intratumoral activation and expansion, and mediate IL-10-dependent suppression of antitumor immunity. Consequently, conditional deletion of Il10 within T cells augments antitumor immunity upon Treg cell depletion in mice, and antibody blockade of IL-10 signaling synergizes with Treg cell depletion to overcome treatment resistance. These findings reveal a secondary layer of immunosuppression by Tconv cells released upon therapeutic Treg cell depletion and suggest that broader consideration of suppressive function within the T cell lineage is required for development of effective Treg cell-targeted therapies.

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.

Harnessing type I interferon-mediated immunity to target malignant brain tumors

Type I interferons have long been appreciated as a cytokine family that regulates antiviral immunity. Recently, their role in eliciting antitumor immune responses has gained increasing attention. Within the immunosuppressive tumor microenvironment (TME), interferons stimulate tumor-infiltrating lymphocytes to promote immune clearance and essentially reshape a "cold" TME into an immune-activating "hot" TME. In this review, we focus on gliomas, with an emphasis on malignant glioblastoma, as these brain tumors possess a highly invasive and heterogenous brain TME. We address how type I interferons regulate antitumor immune responses against malignant gliomas and reshape the overall immune landscape of the brain TME. Furthermore, we discuss how these findings can translate into future immunotherapies targeting brain tumors in general.

CD103+ regulatory T cells underlie resistance to radio-immunotherapy and impair CD8+ T cell activation in glioblastoma

Glioblastomas are aggressive primary brain tumors with an inherent resistance to T cell-centric immunotherapy due to their low mutational burden and immunosuppressive tumor microenvironment. Here we report that fractionated radiotherapy of preclinical glioblastoma models induce a tenfold increase in T cell content. Orthogonally, spatial imaging mass cytometry shows T cell enrichment in human recurrent tumors compared with matched primary glioblastoma. In glioblastoma-bearing mice, α-PD-1 treatment applied at the peak of T cell infiltration post-radiotherapy results in a modest survival benefit compared with concurrent α-PD-1 administration. Following α-PD-1 therapy, CD103⁺ regulatory T cells (Tregs) with upregulated lipid metabolism accumulate in the tumor microenvironment, and restrain immune checkpoint blockade response by repressing CD8⁺ T cell activation. Treg targeting elicits tertiary lymphoid structure formation, enhances CD4⁺ and CD8⁺ T cell frequency and function and unleashes radio-immunotherapeutic efficacy. These results support the rational design of therapeutic regimens limiting the induction of immunosuppressive feedback pathways in the context of T cell immunotherapy in glioblastoma.

Glutamine supplementation attenuates intestinal apoptosis by inducing heat shock protein 70 in heatstroke rats

BACKGROUND

Heatstroke is the most hazardous heat-related illness and has a high fatality rate. We investigated whether glutamine supplementation could have a protective effect on heatstroke rats.

METHODS

Twenty-five 12-week-old male Wistar rats (weight 305±16 g) were randomly divided into a control group (n=5), heatstroke (HS) group (n=10), and heatstroke+glutamine (HSG) group (n=10). Seven days before heat exposure, glutamine (0.4 g/[kg·d]) was administered to the rats in the HSG group by gavage every day. Three hours after heat exposure, serum samples were collected to detect white blood cells, coagulation indicators, blood biochemical indicators, and inflammatory cytokines in the rats. The small intestine tissue was stained to analyze pathological structural changes and apoptosis. Finally, immunohistochemistry and Western blotting were used to analyze the expression levels of heat shock protein 70 (HSP70). Multiple comparisons were analyzed by using one-way analysis of variance, and the Bonferroni test was conducted for the post hoc comparisons.

RESULTS

After heat exposure, the core temperature of the HS group (40.65±0.31 °C) was higher than the criterion of heatstroke, whereas the core temperature of the HSG group (39.45±0.14 °C) was lower than the criterion. Glutamine supplementation restored the increased white blood cells, coagulation indicators, blood biochemical indicators, and inflammatory cytokines that were induced by heatstroke to normal levels. The intestinal mucosa was injured, and the structure of tight junctions was damaged in the HS group; however, the structure of intestinal mucosal epithelial cells was stable in the HSG group. Glutamine supplementation alleviated intestinal apoptosis and up-regulated HSP70 expression.

CONCLUSION

Glutamine supplementation may alleviate intestinal apoptosis by inducing the expression of HSP70 and have a protective effect on heatstroke rats.

Recent Advances in Glioma Cancer Treatment: Conventional and Epigenetic Realms

Glioblastoma (GBM) is the most typical and aggressive form of primary brain tumor in adults, with a poor prognosis. Successful glioma treatment is hampered by ineffective medication distribution across the blood-brain barrier (BBB) and the emergence of drug resistance. Although a few FDA-approved multimodal treatments are available for glioblastoma, most patients still have poor prognoses. Targeting epigenetic variables, immunotherapy, gene therapy, and different vaccine- and peptide-based treatments are some innovative approaches to improve anti-glioma treatment efficacy. Following the identification of lymphatics in the central nervous system, immunotherapy offers a potential method with the potency to permeate the blood-brain barrier. This review will discuss the rationale, tactics, benefits, and drawbacks of current glioma therapy options in clinical and preclinical investigations.

Immunology Meets Bioengineering: Improving the Effectiveness of Glioblastoma Immunotherapy

Glioblastoma (GBM) therapy has seen little change over the past two decades. Surgical excision followed by radiation and chemotherapy is the current gold standard treatment. Immunotherapy techniques have recently transformed many cancer treatments, and GBM is now at the forefront of immunotherapy research. GBM immunotherapy prospects are reviewed here, with an emphasis on immune checkpoint inhibitors and oncolytic viruses. Various forms of nanomaterials to enhance immunotherapy effectiveness are also discussed. For GBM treatment and immunotherapy, we outline the specific properties of nanomaterials. In addition, we provide a short overview of several 3D (bio)printing techniques and their applications in stimulating the GBM microenvironment. Lastly, the susceptibility of GBM cancer cells to the various immunotherapy methods will be addressed.

Harnessing cytokines and chemokines for cancer therapy

During the past 40 years, cytokines and cytokine receptors have been extensively investigated as either cancer targets or cancer treatments. A strong preclinical rationale supports therapeutic strategies to enhance the growth inhibitory and immunostimulatory effects of interferons and interleukins, including IL-2, IL-7, IL-12 and IL-15, or to inhibit the inflammatory and tumour-promoting actions of cytokines such as TNF, IL-1β and IL-6. This rationale is underscored by the discovery of altered and dysregulated cytokine expression in all human cancers. These findings prompted clinical trials of several cytokines or cytokine antagonists, revealing relevant biological activity but limited therapeutic efficacy. However, most trials involved patients with advanced-stage disease, which might not be the optimal setting for cytokine-based therapy. The advent of more effective immunotherapies and an increased understanding of the tumour microenvironment have presented new approaches to harnessing cytokine networks in the treatment of cancer, which include using cytokine-based therapies to enhance the activity or alleviate the immune-related toxicities of other treatments as well as to target early stage cancers. Many challenges remain, especially concerning delivery methods, context dependencies, and the pleiotropic, redundant and often conflicting actions of many cytokines. Herein, we discuss the lessons learnt from the initial trials of single-agent cytokine-based therapies and subsequent efforts to better exploit such agents for the treatment of solid tumours.

Is There a Role for Immunotherapy in Central Nervous System Cancers?

Glioblastoma has emerged as an immunotherapy-refractory tumor based on negative phase III studies of anti-programmed cell death-1 therapy among newly diagnosed as well as recurrent patients. In addition, although much work on vaccine and cellular approaches is ongoing, therapeutic benefit with these approaches has been underwhelming. Much scientific insight into the multitiered layers of immunosuppression exploited by glioblastoma tumors is emerging that sheds light on the explanation for the disappointing results to date and highlights possible therapeutic avenues that may offer a better likelihood of therapeutic benefit for immune-based therapies.

New Immunotherapeutic Approaches for Glioblastoma

Glioblastoma (GBM) is the most common primary malignant brain tumor with a high mortality rate. The current treatment consists of surgical resection, radiation, and chemotherapy; however, the median survival rate is only 12-18 months despite these alternatives, highlighting the urgent need to find new strategies. The heterogeneity of GBM makes this tumor difficult to treat, and the immunotherapies result in an attractive approach to modulate the antitumoral immune responses favoring the tumor eradication. The immunotherapies for GMB including monoclonal antibodies, checkpoint inhibitors, vaccines, and oncolytic viruses, among others, have shown favorable results alone or as a multimodal treatment. In this review, we summarize and discuss promising immunotherapies for GBM currently under preclinical investigation as well as in clinical trials.

Optimizing T Cell-Based Therapy for Glioblastoma

Evading T cell surveillance is a hallmark of cancer. Patients with solid tissue malignancy, such as glioblastoma (GBM), have multiple forms of immune dysfunction, including defective T cell function. T cell dysfunction is exacerbated by standard treatment strategies such as steroids, chemotherapy, and radiation. Reinvigoration of T cell responses can be achieved by utilizing adoptively transferred T cells, including CAR T cells. However, these cells are at risk for depletion and dysfunction as well. This review will discuss adoptive T cell transfer strategies and methods to avoid T cell dysfunction for the treatment of brain cancer.

Challenging Hurdles of Current Targeting in Glioblastoma: A Focus on Immunotherapeutic Strategies

Glioblastoma is the most frequent primary neoplasm of the central nervous system and still suffers from very poor therapeutic impact. No clear improvements over current standard of care have been made in the last decade. For other cancers, but also for brain metastasis, which harbors a very distinct biology from glioblastoma, immunotherapy has already proven its efficacy. Efforts have been pursued to allow glioblastoma patients to benefit from these new approaches, but the road is still long for broad application. Here, we aim to review key glioblastoma immune related characteristics, current immunotherapeutic strategies being explored, their potential caveats, and future directions.

The Therapeutic Potential of Regulatory T Cells: Challenges and Opportunities

Regulatory T cells (Tregs) are an immunosuppressive subgroup of CD4+ T cells which are identified by the expression of forkhead box protein P3 (Foxp3). The modulation capacity of these immune cells holds an important role in both transplantation and the development of autoimmune diseases. These cells are the main mediators of self-tolerance and are essential for avoiding excessive immune reactions. Tregs play a key role in the induction of peripheral tolerance that can prevent autoimmunity, by protecting self-reactive lymphocytes from the immune reaction. In contrast to autoimmune responses, tumor cells exploit Tregs in order to prevent immune cell recognition and anti-tumor immune response during the carcinogenesis process. Recently, numerous studies have focused on unraveling the biological functions and principles of Tregs and their primary suppressive mechanisms. Due to the promising and outstanding results, Tregs have been widely investigated as an alternative tool in preventing graft rejection and treating autoimmune diseases. On the other hand, targeting Tregs for the purpose of improving cancer immunotherapy is being intensively evaluated as a desirable and effective method. The purpose of this review is to point out the characteristic function and therapeutic potential of Tregs in regulatory immune mechanisms in transplantation tolerance, autoimmune diseases, cancer therapy, and also to discuss that how the manipulation of these mechanisms may increase the therapeutic options.

Temozolomide treatment outcomes and immunotherapy efficacy in brain tumor

INTRODUCTION

Glioblastoma (GBM) has a survival rate of around 2 years with aggressive current standard of care. While other tumors have responded favorably to trials combining immunotherapy and chemotherapy, GBM remains uniformly deadly with minimal increases in overall survival. GBM differ from others due to being isolated behind the blood brain barrier, increased heterogeneity and mutational burden, and immunosuppression from the brain environment and tumor itself.

METHODS

We have reviewed clinical and preclinical studies investigating how different doses (dose intense (DI) and metronomic) and timing of immunotherapy following TMZ treatment can eradicate tumor cells, alter tumor mutational burden, and change immune cells.

RESULTS

Recent clinical trials with standard of care (SoC), DI and metronomic TMZ regimes are no able to completely eradicate GBM. Elevated TMZ levels in DI treatment can overcome MGMT resistance but may result in hypermutation of surviving tumor cells. Higher levels of TMZ will also generate a higher degree of lymphopenia compared to SoC and metronomic regimes in preclinical studies.

CONCLUSION

The different levels of lymphopenia and tumor eradication discussed in this review suggest possible beneficial pairings between immunotherapy and TMZ treatment. Treatments resulting in profound lymphopenia will allow for expansion of vaccine specific T cells or of CAT T cells. Clinical and preclinical studies are currently comparing different combinations of TMZ and immunotherapy timing to treat GBM through a balance between tumor killing and immune cell expansion. More frequent immune monitoring time points in ongoing clinical trials are crucial for further development of these combinations.

Randomized Controlled Immunotherapy Clinical Trials for GBM Challenged

Simple Summary

Although multiple meta-analyses on active specific immunotherapy treatment for glioblastoma multiforme (GBM) have demonstrated a significant prolongation of overall survival, no single research group has succeeded in demonstrating the efficacy of this type of treatment in a prospective, double-blind, placebo-controlled, randomized clinical trial. In this paper, we explain how the complexity of the tumor biology and tumor–host interactions make proper stratification of a control group impossible. The individualized characteristics of advanced therapy medicinal products for immunotherapy contribute to heterogeneity within an experimental group. The dynamics of each tumor and in each patient aggravate comparative stable patient groups. Finally, combinations of immunotherapy strategies should be integrated with first-line treatment. We illustrate the complexity of a combined first-line treatment with individualized multimodal immunotherapy in a group of 70 adults with GBM and demonstrate that the integration of immunogenic cell death treatment within maintenance chemotherapy followed by dendritic cell vaccines and maintenance immunotherapy might provide a step towards improving the overall survival rate of GBM patients.

Abstract

Immunotherapies represent a promising strategy for glioblastoma multiforme (GBM) treatment. Different immunotherapies include the use of checkpoint inhibitors, adoptive cell therapies such as chimeric antigen receptor (CAR) T cells, and vaccines such as dendritic cell vaccines. Antibodies have also been used as toxin or radioactive particle delivery vehicles to eliminate target cells in the treatment of GBM. Oncolytic viral therapy and other immunogenic cell death-inducing treatments bridge the antitumor strategy with immunization and installation of immune control over the disease. These strategies should be included in the standard treatment protocol for GBM. Some immunotherapies are individualized in terms of the medicinal product, the immune target, and the immune tumor–host contact. Current individualized immunotherapy strategies focus on combinations of approaches. Standardization appears to be impossible in the face of complex controlled trial designs. To define appropriate control groups, stratification according to the Recursive Partitioning Analysis classification, MGMT promotor methylation, epigenetic GBM sub-typing, tumor microenvironment, systemic immune functioning before and after radiochemotherapy, and the need for/type of symptom-relieving drugs is required. Moreover, maintenance of a fixed treatment protocol for a dynamic, deadly cancer disease in a permanently changing tumor–host immune context might be inappropriate. This complexity is illustrated using our own data on individualized multimodal immunotherapies for GBM. Individualized medicines, including multimodal immunotherapies, are a rational and optimal yet also flexible approach to induce long-term tumor control. However, innovative methods are needed to assess the efficacy of complex individualized treatments and implement them more quickly into the general health system.

IDH-mutant gliomas harbor fewer regulatory T cells in humans and mice

The metabolic gene isocitrate dehydrogenase 1 (IDH1) is commonly mutated in lower grade glioma (LGG) and secondary glioblastoma (GBM). Regulatory T cells (Tregs) play a significant role in the suppression of antitumor immunity in human glioma. Given the importance of Tregs in the overall framework of designing immune-based therapies, a better understanding on their association with IDH mutational status remains of critical clinical importance. Using multispectral imaging analysis, we compared the incidence of Tregs in IDH-mutant and IDH wild-type glioma from patient tumor samples of LGG. An orthotopic IDH-mutant murine model was generated to evaluate the role of mutant IDH on Treg infiltration by immunohistochemistry. When compared to IDH wild-type controls, Tregs are disproportionally underrepresented in mutant disease, even when taken as a proportion of all infiltrating T cells. Our findings suggest that therapeutic agents targeting Tregs may be more appropriate in modulating the immune response to wild-type disease.

Immunotherapy in Glioblastoma: Current Shortcomings and Future Perspectives

Glioblastomas are aggressive, fast-growing primary brain tumors. After standard-of-care treatment with radiation in combination with temozolomide, the overall prognosis of newly diagnosed patients remains poor, with a 2-year survival rate of less than 20%. The remarkable survival benefit gained with immunotherapy in several extracranial tumor types spurred a variety of experimental intervention studies in glioblastoma patients. These ranged from immune checkpoint inhibition to vaccinations and adoptive T cell therapies. Unfortunately, almost all clinical outcomes were universally disappointing. In this perspective, we provide an overview of immune interventions performed to date in glioblastoma patients and re-evaluate their performance. We argue that shortcomings of current immune therapies in glioblastoma are related to three major determinants of resistance, namely: low immunogenicity; immune privilege of the central nervous system; and immunosuppressive micro-environment. In this perspective, we propose strategies that are guided by exact shortcomings to sensitize glioblastoma prior to treatment with therapies that enhance numbers and/or activation state of CD8 T cells.

Alterations of the tumor microenvironment in glioblastoma following radiation and temozolomide with or without bevacizumab

Background

The immunosuppressive tumor microenvironment (TME) contributes to the tumor progression and treatment failure. Our previous study demonstrated alterations in the TME during bevacizumab (Bev) therapy in human glioblastoma (GB) specimens obtained from patients who underwent surgical resection. Continuous Bev administration downregulates the expression of programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1), suppresses the infiltration of tumor associated macrophages (TAMs) and regulatory T cells (Tregs), and increases cytotoxic T lymphocytes (CTLs) infiltration. However, one may argue that these immunosupportive effects might also be induced by radiation therapy (RT) or temozolomide (TMZ), and they cannot necessarily be attributed to Bev alone.

Methods

In the present study, changes in the molecules relevant to the TME were analyzed by immunohistochemistry using paired pre- and post-treatment samples of malignant glioma specimens from 15 patients who received RT and TMZ therapy without Bev.

Results

The expression levels of CD34, vascular endothelial growth factor (VEGF)-A, VEGF receptor 2 (VEGFR2), HIF-1α, CA9, nestin, CD4, CD8, CD163, PD-1, and PD-L1 were not significantly changed after the treatment with RT and TMZ. However, VEGFR1 expression and the number of Foxp3-positive cells tended to be upregulated and increased after the treatment (P=0.058, P=0.082, respectively).

Conclusions

This was the first study to show the alterations of TME following RT and TMZ therapy using paired pre- and post-treatment malignant glioma samples. Long-term treatment of RT and TMZ might worsen immunosuppressive TME in malignant gliomas.

[Metformin inhibits proliferation and functions of regulatory T cells in acidic environment]

OBJECTIVE

To investigate the regulatory effect of metformin on regulatory T cells (Treg) in acidic environment.

METHODS

CD4⁺ CD25⁺ Treg cells were obtained by magnetic bead sorting. Treg and conventional T cells (Tcon) cells were cultured for 24-72 h in pH 7.4 or pH 6.7 medium, and the cell proliferation, apoptosis and Foxp3 expression were detected by flow cytometry. Real-time PCR was used to detect the expression levels of the genes related with glucose metabolism. Thirty-two C57BL/6 male mouse models bearing subcutaneous prostate cancer xenograft derived from RM-1 cells were randomized into 4 equal groups for treatment with PBS, metformin, tumor vaccine, or both metformin and the vaccine. The treatment started on the 4th day following tumor cell injection, and metformin (100 mg/kg) or PBS was administered by intraperitoneal injection on a daily basis; the vaccine was intramuscularly injected every 4 days. The tumor size was continuously monitored, and the mice were euthanized on day 25 after tumor implantation to obtain tumor and blood samples. Flow cytometry was used to detect the changes in CD4⁺, CD8⁺, CD4⁺Foxp3⁺ cell subsets in the tumor tissue and peripheral blood.

RESULTS

Treg cells showed significantly enhanced proliferation (P < 0.05) while the proliferation of Tcon cells was suppressed in acidic medium (P < 0.001). Treg cells cultured in acidic medium showed significantly increased expressions of OXPHOS-related genes pgc1a (P < 0.001) and cox5b (P < 0.01), which did not vary significantly in Tcon cells in acidic medium. Treg cells exhibited significantly decreased apoptosis in acidic medium (P < 0.01) with increased Foxp3⁺ cells (P < 0.001) and intracellular alkaline levels (P < 0.01). Metformin obviously reversed the acid tolerance of Treg cells without producing significant effect on Tcon cells. In the animal experiment, both metformin (P < 0.05) and vaccine (P < 0.01) alone reduced the tumor volume, but their combined treatment more potently reduced the tumor volume (P < 0.001). Metformin alone did not obviously affect CD4⁺ cells or CD8⁺ cells but significantly decreased the percentage of CD4⁺Foxp3⁺ (P < 0.05); the vaccine alone significantly increased CD4⁺ cells and CD8⁺ cells (P < 0.001) and also the percentage of CD4⁺Foxp3⁺ cells (P < 0.05). The combined treatment, while reducing the percentage of CD4⁺Foxp3⁺cells to a level lower than that in the vaccine group (P < 0.01), produced the strongest effect to increase CD4⁺ cells and CD8⁺ cells (P < 0.01).

CONCLUSIONS

Metformin can inhibit the proliferation and function of regulatory T cells in an acidic environment and enhance the effect of tumor vaccine by reducing the proportion of Treg cells in vivo to achieve the anti-tumor effect.

Regulatory T cells in breast cancer as a potent anti-cancer therapeutic target

Despite marked advances in treatment approaches, breast cancer is still going to be more prevalent, worldwide. High levels of regulatory T (Treg) cells have repeatedly been demonstrated in circulation, lymph nodes, and tumor samples from patients with various cancer types. The transcription factor Forkhead box protein 3 (Foxp3)-expressing Treg cells have the high suppressive potential of the immune system and are fundamental in preserving immune homeostasis and self-tolerance. However, they enhance tumor development by curbing efficient anti-tumor immune mechanisms in malignancies. Moreover, the accumulation of Treg cells in breast tumors is related to the short overall survival of patients. Treg cell frequency has been applied as an independent predicting factor to diagnose patients with a high risk of relapse. Pulling out all populations of Treg cells to promote the efficacy of anticancer treatment methods may potentially lead to hazardous autoimmune disorders. Thus, realizing the exact structure of tumor-infiltrating Treg cells is pivotal to efficiently target Treg cells in tumors. There are exclusive and non-exclusive approaches to lower down and degrade the number/function of Treg cells. These approaches can include inhibiting tumoral migration, depletion, interference with function, and utilizing T cell plasticity. This review article attempts to clarify the implications concerning the involvement of Treg cells in breast cancer progression and discuss the current approaches in the treatment of this cancer via modulation of Treg cells function.

The role of vascular endothelial growth factor in the hypoxic and immunosuppressive tumor microenvironment: perspectives for therapeutic implications

The microvasculature and immune cells are major components of the tumor microenvironment (TME). Hypoxia plays a pivotal role in the TME through hypoxia-inducible factor 1-alpha (HIF-1α) which upregulates vascular endothelial growth factor (VEGF). VEGF, an angiogenesis stimulator, suppresses tumor immunity by inhibiting the maturation of dendritic cells, and induces immunosuppressive cells such as regulatory T cells, tumor-associated macrophages, and myeloid-derived suppressor cells. HIF-1α directly induces immune checkpoint molecules. VEGF/VEGF receptor (VEGFR)-targeted therapy as a cancer treatment has not only anti-angiogenic effects, but also immune-supportive effects. Anti-angiogenic therapy has the potential to change the immunological "cold tumors" into the "hot tumors". Glioblastoma (GB) is a hypervascular tumor with high VEGF expression which leads to development of an immuno suppressive TME. Therefore, in the last decade, several combination immunotherapies with anti-angiogenic agents have been developed for numerous tumors including GBs. In particular, combination therapy with an immune checkpoint inhibitor and VEGF/VEGFR-targeted therapy has been suggested as a synergic treatment strategy that may show favorable changes in the TME. In this article, we discuss the cross talk among immunosuppressive cells exposed to VEGF in the hypoxic TME of GBs. Current efficient combination strategies using VEGF/VEGFR-targeted therapy are reviewed and proposed as novel cancer treatments.

Temozolomide for immunomodulation in the treatment of glioblastoma

Temozolomide is the most widely used chemotherapy for patients with glioblastoma (GBM) despite the fact that approximately half of treated patients have temozolomide resistance and all patients eventually fail therapy. Due to the limited efficacy of existing therapies, immunotherapy is being widely investigated for patients with GBM. However, initial immunotherapy trials in GBM patients have had disappointing results as monotherapy. Therefore, combinatorial treatment strategies are being investigated. Temozolomide has several effects on the immune system that are dependent on mode of delivery and the dosing strategy, which may have unpredicted effects on immunotherapy. Here we summarize the immune modulating role of temozolomide alone and in combination with immunotherapies such as dendritic cell vaccines, T-cell therapy, and immune checkpoint inhibitors for patients with GBM.

Radiation and Immunotherapy in High-grade Gliomas: Where Do We Stand?

High-grade glioma is the most common primary brain tumor, with glioblastoma multiforme (GBM) accounting for 52% of all brain tumors. The current standard of care (SOC) of GBM involves surgery followed by adjuvant fractionated radiotherapy and chemotherapy. However, little progress has been made in extending overall survival, progression-free survival, and quality of life. Attempts to characterize and customize treatment of GBM have led to mitigating the deleterious effects of radiotherapy using hypofractionated radiotherapy, as well as various immunotherapies as a promising strategy for the incurable disease. A combination of radiotherapy and immunotherapy may prove to be even more effective than either alone, and preclinical evidence suggests that hypofractionated radiotherapy can actually prime the immune system to make immunotherapy more effective. This review addresses the complications of the current radiotherapy regimen, various methods of immunotherapy, and preclinical and clinical data from combined radioimmunotherapy trials.

Histone deacetylase enzymes and selective histone deacetylase inhibitors for antitumor effects and enhancement of antitumor immunity in glioblastoma

Glioblastoma multiforme (GBM), which is the most common primary central nervous system malignancy in adults, has long presented a formidable challenge to researchers and clinicians alike. Dismal 5-year survival rates of the patients with these tumors and the ability of the recurrent tumors to evade primary treatment strategies have prompted a need for alternative therapies in the treatment of GBM. Histone deacetylase (HDAC) inhibitors are currently a potential epigenetic therapy modality under investigation for use in GBM with mixed results. While these agents show promise through a variety of proposed mechanisms in the pre-clinical realm, only several of these agents have shown this same promise when translated into the clinical arena, either as monotherapy or for use in combination regimens. This review will examine the current state of use of HDAC inhibitors in GBM, the mechanistic rationale for use of HDAC inhibitors in GBM, and then examine an exciting new mechanistic revelation of certain HDAC inhibitors that promote antitumor immunity in GBM. The details of this antitumor immunity will be discussed with an emphasis on application of this antitumor immunity towards developing alternative therapies for treatment of GBM. The final section of this article will provide an overview of the current state of immunotherapy targeted specifically to GBM.

Combining radiation therapy and cancer immune therapies: From preclinical findings to clinical applications

Besides its direct cytotoxic effect on the tumor cells, radiation therapy is also able to elicit an immune-mediated systemic anti-tumor response, resulting in tumor regression in irradiated sites but also within distant out of field secondary lesions and providing a long-term anti-tumor response. It is now clear that associating ionizing radiation with immune therapies can enhance radio-induced anti-tumor immune responses. Over the last decade, such a combination aroused considerable interest among the scientific community, with many preclinical models and clinical trials, using many types of immune therapies and radiation regimens. In this article, we summarize the main mechanisms underlying radio-induced anti-tumor responses. We will then present an extended overview of the recent preclinical and clinical research built on this background of combined radiation and immune therapy, shedding light on what we know so far about such a promising strategy.

The promises of immunotherapy in gliomas

PURPOSE OF REVIEW

Also owing to the limited efficacy of targeted therapies, there has been a renewed interest in targeting gliomas with immunotherapy. But despite considerable efforts using sophisticated approaches, proof of efficacy beyond case studies is still lacking. The purpose of this review is to summarize and discuss current immunotherapeutic approaches and efforts to understand mechanisms of response and resistance.

RECENT FINDINGS

The recent failure of large randomized clinical trials using targeted vaccines and checkpoint inhibitors to improve clinical outcome have underlined the grand challenges in this therapeutic arena and illustrated the necessity to understand the biology of immunotherapeutic interventions before conducting large randomized studies. However, these failures should not distract us from continuing to optimize immunotherapeutic concepts. The recent developments in transgenic T cell technologies and personalized vaccines but also rational combinatorial approaches offer tremendous opportunities and should be exploited carefully in early scientifically driven clinical trials.

SUMMARY

A profound understanding of the cellular and molecular mechanisms of response and resistance to immunotherapy to be gained from these thoroughly designed clinical trials will be essential to carve out successful strategies in selected patient populations.

T-cell Dysfunction in Glioblastoma: Applying a New Framework

A functional, replete T-cell repertoire is an integral component to adequate immune surveillance and to the initiation and maintenance of productive antitumor immune responses. Glioblastoma (GBM), however, is particularly adept at sabotaging antitumor immunity, eliciting severe T-cell dysfunction that is both qualitative and quantitative. Understanding and countering such dysfunction are among the keys to harnessing the otherwise stark potential of anticancer immune-based therapies. Although T-cell dysfunction in GBM has been long described, newer immunologic frameworks now exist for reclassifying T-cell deficits in a manner that better permits their study and reversal. Herein, we divide and discuss the various T-cell deficits elicited by GBM within the context of the five relevant categories: senescence, tolerance, anergy, exhaustion, and ignorance. Categorization is appropriately made according to the molecular bases of dysfunction. Likewise, we review the mechanisms by which GBM elicits each mode of T-cell dysfunction and discuss the emerging immunotherapeutic strategies designed to overcome them. Clin Cancer Res; 24(16); 3792-802. ©2018 AACR.

Immunotherapies for malignant glioma

Glioblastoma multiforme (GBM) is a highly malignant primary brain cancer with a dreadful overall survival and for which treatment options are limited. Recent breakthroughs in novel immune-related treatment strategies for cancer have spurred interests in usurping the power of the patient's immune system to recognize and eliminate GBM. Here, we discuss the unique properties of GBM's tumor microenvironment, the effects of GBM standard on care therapy on tumor-associated immune cells, and review several approaches aimed at therapeutically targeting the immune system for GBM treatment. We believe that a comprehensive understanding of the intricate micro-environmental landscape of GBM will abound into the development of novel immunotherapy strategies for GBM patients.

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.

Mathematical modeling of tumor-induced immunosuppression by myeloid-derived suppressor cells: Implications for therapeutic targeting strategies

Myeloid-derived suppressor cells (MDSCs) belong to immature myeloid cells that are generated and accumulated during the tumor development. MDSCs strongly suppress the anti-tumor immunity and provide conditions for tumor progression and metastasis. In this study, we present a mathematical model based on ordinary differential equations (ODE) to describe tumor-induced immunosuppression caused by MDSCs. The model consists of four equations and incorporates tumor cells, cytotoxic T cells (CTLs), natural killer (NK) cells and MDSCs. We also provide simulation models that evaluate or predict the effects of anti-MDSC drugs (e.g., l-arginine and 5-Fluorouracil (5-FU)) on the tumor growth and the restoration of anti-tumor immunity. The simulated results obtained using our model were in good agreement with the corresponding experimental findings on the expansion of splenic MDSCs, immunosuppressive effects of these cells at the tumor site and effectiveness of l-arginine and 5-FU on the re-establishment of antitumor immunity. Regarding this latter issue, our predictive simulation results demonstrated that intermittent therapy with low-dose 5-FU alone could eradicate the tumors irrespective of their origins and types. Furthermore, at the time of tumor eradication, the number of CTLs prevailed over that of cancer cells and the number of splenic MDSCs returned to the normal levels. Finally, our predictive simulation results also showed that the addition of l-arginine supplementation to the intermittent 5-FU therapy reduced the time of the tumor eradication and the number of iterations for 5-FU treatment. Thus, the present mathematical model provides important implications for designing new therapeutic strategies that aim to restore antitumor immunity by targeting MDSCs.

Phenotypic and Functional Properties of Tumor-Infiltrating Regulatory T Cells

Regulatory T (Treg) cells maintain immune homeostasis by suppressing excessive immune responses. Treg cells induce tolerance against self- and foreign antigens, thus preventing autoimmunity, allergy, graft rejection, and fetus rejection during pregnancy. However, Treg cells also infiltrate into tumors and inhibit antitumor immune responses, thus inhibiting anticancer therapy. Depleting whole Treg cell populations in the body to enhance anticancer treatments will produce deleterious autoimmune diseases. Therefore, understanding the precise nature of tumor-infiltrating Treg cells is essential for effectively targeting Treg cells in tumors. This review summarizes recent results relating to Treg cells in the tumor microenvironment, with particular emphasis on their accumulation, phenotypic, and functional properties, and targeting to enhance the efficacy of anticancer treatment.

How immunotherapies are targeting the glioblastoma immune environment

The diagnosis of glioblastoma remains one of the most dismal in medical practice, with current standard care only providing a median survival of 14.6 months. The need for new therapies is desperately clear. Components of the tumour microenvironment are demonstrating growing importance in the field, given they allow the tumour to utilise pathways involved in autoimmune prevention, something that enables the tumour's establishment and growth. As with many different cancers, the search for a new standard has progressed to the design of immunotherapies, which aim to counteract the immune changes within this microenvironment. Serotherapy, adoptive lymphocyte transfer, peptide and dendritic cell vaccines and a range of other methods are currently under investigation, while intracranial infection has also been researched for its capacity to reverse glioblastoma mediated immunosuppression. Some of these new therapies have shown promise, but it is a long road ahead before their incorporation into glioblastoma standard therapy.

Advances in immunotherapy for pediatric acute myeloid leukemia

INTRODUCTION

Achieving better disease control in patients diagnosed with acute myeloid leukemia (AML) has proven challenging. Overall survival has been impacted by addressing treatment related mortality with focused supportive care measures. Despite this improvement, it remains difficult to induce durable leukemia remissions despite aggressive chemotherapeutic regimens. The addition of hematopoietic stem cell transplants (HSCT) has allowed further treatment intensification and provided the benefit of graft-versus-leukemia (GVL) effect. However, HSCT carries the risk of transplant related morbidities, particularly GVHD, and anti-tumor responsiveness is still suboptimal. Thus, there is a need for alternate therapies. Immunotherapy has the potential to address this need. Areas covered: Expert opinion: The elusiveness of an ideal surface antigen target together with an immunosuppressive leukemic microenvironment add to the already difficult challenge in developing AML-targeted immunotherapies. Though many hurdles remain, recent translational discovery and progressive clinical advances anticipate exciting future developments.

AREAS COVERED

This review highlights promises and challenges to immune-based therapies for AML. It aims to summarize immunotherapeutic strategies trialed in AML patients to date, inclusive of: antibodies, vaccines, and cellular therapy. It emphasizes those being used in the pediatric population, but also includes adult clinical trials and translational science that may ultimately extend to pediatric patients.

Vaccine strategies for the treatment of lymphoma: preclinical progress and clinical trial update

The clonal B-cell immunoglobulin idiotype found on the surface of lymphomas was the first targeted tumor-specific antigen, and combinations of idiotype with classical and novel adjuvants were shown to stimulate robust humoral and cellular responses, though clinical efficacy was more variable. Cellular and in situ vaccination to help target a wider array of tumor-specific antigens have also been able to stimulate tumor-specific cellular responses, though their clinical success has also been limited. Our growing understanding of the role of regulatory cells and the immunosuppressive tumor microenvironment, along with a wide variety of immunomodulatory agents developed as of late, offer promising adjuvants to potentiate the immune responses elicited by these vaccine protocols and to achieve durable remissions.

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.

Conversion to mycophenolate mofetil monotherapy in liver recipients: Calcineurin inhibitor levels are key

 The use of calcineurin inhibitors (CNI) after liver transplantation is associated with post-transplant nephrotoxicity. Conversion to mycophenolate mofetil (MMF) monotherapy improves renal function, but is related to graft rejection in some recipients. Our aim was to identify variables associated with rejection after conversion to MMF monotherapy. Conversion was attempted in 40 liver transplant recipients. Clinical variables were determined and peripheral mononuclear blood cells were immunophenotyped during a 12-month follow-up. Conversion was classified as successful (SC) if rejection did not occur during the follow-up. MMF conversion was successful with 28 patients (70%) and was associated with higher glomerular filtration rates at the end of study. It also correlated with increased time elapsed since transplantation, low baseline CNI levels (Tacrolimus ≤ 6.5 ng/mL or Cyclosporine ≤ 635 ng/mL) and lower frequency of tacrolimus use. The only clinical variable independently related to SC in multivariate analysis was low baseline CNI levels (p = 0.02, OR: 6.93, 95%, CI: 1.3-29.7). Mean baseline fluorescent intensity of FOXP3+ T cells was significantly higher among recipients with SC. In conclusion, this study suggests that baseline CNI levels can be used to identify recipients with higher probability of SC to MMF monotherapy. Clinicaltrials.gov identification: NCT01321112.

Immunotherapy of Malignant Tumors in the Brain: How Different from Other Sites?

Immunotherapy is now advancing at remarkable pace for tumors located in various tissues, including the brain. Strategies launched decades ago, such as tumor antigen-specific therapeutic vaccines and adoptive transfer of tumor-infiltrating lymphocytes are being complemented by molecular engineering approaches allowing the development of tumor-specific TCR transgenic and chimeric antigen receptor T cells. In addition, the spectacular results obtained in the last years with immune checkpoint inhibitors are transfiguring immunotherapy, these agents being used both as single molecules, but also in combination with other immunotherapeutic modalities. Implementation of these various strategies is ongoing for more and more malignancies, including tumors located in the brain, raising the question of the immunological particularities of this site. This may necessitate cautious selection of tumor antigens, minimizing the immunosuppressive environment and promoting efficient T cell trafficking to the tumor. Once these aspects are taken into account, we might efficiently design immunotherapy for patients suffering from tumors located in the brain, with beneficial clinical outcome.

Immunological effects of chemotherapy and radiotherapy against brain tumors

INTRODUCTION

The mainstays of brain tumor therapy are surgery, radiotherapy and chemotherapy. Cancer immunotherapy is explored as an additional treatment modality. However, emerging evidence indicates that also radio- and chemotherapy have immunological effects in addition to their cytotoxic and cytostatic activities.

AREA COVERED

We summarize the literature on radio- and chemotherapy-mediated immunological effects in primary and secondary brain tumors and outline open questions within the field. To this end, a literature search was performed using the terms 'brain tumor', 'immune system', 'immunogenic cell death', 'vaccination', 'checkpoint inhibition', 'radiotherapy', 'chemotherapy' and derivations thereof. Expert commentary: Immunological effects of chemo- and radiotherapy in brain tumors involve direct immunogenic modulations of tumor cells, changes of the microenvironment and functional alterations of innate and adaptive immune cells. Each treatment modality can exert various effects that comprise both immune-stimulatory and immunosuppressive mechanisms. A detailed knowledge of these mechanisms is indispensable for an optimal combination of conventional anti-tumor treatments and novel immunotherapeutic approaches.

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.

Immunosuppressive mechanisms in glioblastoma

Despite maximal surgical and medical therapy, the treatment of glioblastoma remains a seriously vexing problem, with median survival well under 2 years and few long-term survivors. Targeted therapy has yet to produce significant advances in treatment of these lesions in spite of advanced molecular characterization of glioblastoma and glioblastoma cancer stem cells. Recently, immunotherapy has emerged as a promising mode for some of the hardest to treat tumors, including metastatic melanoma. Although immunotherapy has been evaluated in glioblastoma in the past with limited success, better understanding of the failures of these therapies could lead to more successful treatments in the future. Furthermore, there is a persistent challenge for the use of immune therapy to treat glioblastoma secondary to the existence of redundant mechanisms of tumor-mediated immune suppression. Here we will address these mechanisms of immunosuppression in glioblastoma and therapeutic approaches.

Developing immunotherapeutic strategies to target brain tumors

INTRODUCTION

Recent years have seen rapid growth in cancer treatments that enhance the anti-tumor activities of the immune system. Collectively known as immunotherapy, modulation of the immune system has shown success treating some hematological malignancies, but has yet to be successfully applied to the treatment of patients with brain tumors.

AREAS COVERED

This review highlights mechanistic insights from murine studies and compiled recent clinical trial data, focusing on the most aggressive brain tumor, glioblastoma (GBM). The field has recently accumulated a critical mass of data, and we discuss past treatment failures in the context of newly developed approaches now entering clinical trials. This article provides an overview of the immunotherapeutic armamentarium currently in development for the treatment of patients with GBM, who are in dire need of safe and effective therapies. Expert commentary: Themes that emerge include the importance of mitigating the effects of an immunosuppressive tumor microenvironment and the potential for innate immune cell activation to enhance cytotoxic anti-tumor activity. Consideration of these studies as a collective may inform the design of new immunotherapies, as well as the immune monitoring protocols for patients participating in clinical trials.

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.