Elevated CD3+ and CD8+ tumor-infiltrating immune cells correlate with prolonged survival in glioblastoma patients despite integrated immunosuppressive mechanisms in the tumor microenvironment and at the systemic level

Efficacy of ruthenium coordination complex-based Rutherrin in a preclinical rat glioblastoma model

Background

Glioblastoma is an aggressive brain cancer in adults with a grave prognosis, aggressive radio and chemotherapy provide only a 15 months median survival.

Methods

We evaluated the tolerability and efficacy of the Ruthenium-based photosensitizer TLD-1433 with apo-Transferrin (Rutherrin) in the rat glioma 2 (RG-2) model. The specific tumor uptake ratio and photodynamic therapy (PDT) threshold of the rat glioblastoma and normal brain were determined, survival and CD8⁺T-cell infiltration post-therapy were analyzed. Results were compared with those obtained for 5-aminolevulinic acid (ALA)-induced Protoporphyrin IX (PpIX)-mediated photodynamic therapy in the same animal model. As both photosensitizers have different photophysical properties, the number of absorbed photons required to achieve an equal cell kill was determined for in vitro and in vivo studies.

Results

A significantly lower absorbed energy was sufficient to achieve LD₅₀ with Rutherrin versus PpIX-mediated PDT. Rutherrin provides a higher specific uptake ratio (SUR) >20 in tumors versus normal brain, whereas the SUR for ALA-induced PpIX was 10.6. To evaluate the short-term tissue response in vivo, enhanced T2-weighted magnetic resonance imaging (MRI) provided the spatial extent of edema, post PpIX-PDT at twice the cross-section versus Rutherrin-PDT suggesting reduced nonspecific damage, typically associated with a secondary wave of neuronal damage. Following a single therapy, a significant survival increase was observed in rats bearing glioma for PDT mediated by Rutherrin versus PpIX for the selected treatment conditions. Rutherrin-PDT also demonstrated an increased CD8+T-cell infiltration in the tumors.

Conclusion

Rutherrin-PDT was well tolerated providing a safe and effective treatment of RG-2 glioma.

Clinical chimeric antigen receptor-T cell therapy: a new and promising treatment modality for glioblastoma

Chimeric antigen receptor (CAR)-T cell therapy is now approved in the United States and Europe as a standard treatment for relapsed/refractory B-cell malignancies. It has also been approved recently by the Therapeutic Goods Administration in Australia and may soon be publicly reimbursed. This advance has accentuated scientific, clinical and commercial interest in adapting this exciting technology for the treatment of solid cancers where it is widely recognised that the challenges of overcoming a hostile tumor microenvironment are most acute. Indeed, CAR-T cell technology may be of the greatest value for those cancers that lack pre-existing immunity because they are immunologically 'cold', or have a low somatic tumor mutation load, or both. These cancers are generally not amenable to therapeutic immune checkpoint blockade, but CAR-T cell therapy may be effective because it provides an abundant supply of autologous tumor-specific T cells. This is achieved by using genetic engineering to re-direct autologous T-cell cytotoxicity towards a tumor-associated antigen, bypassing endogenous T-cell requirements for antigen processing, MHC-dependent antigen presentation and co-stimulation. One of the most challenging solid cancers is glioblastoma, which has among the least permissive immunological milieu of any cancer, and which is almost always fatal. Here, we argue that CAR-T cell technology may counter some glioblastoma defences and provide a beachhead for furthering our eventual therapeutic aims of restoring effective antitumor immunity. Although clinical investigation of CAR-T cell therapy for glioblastoma is at an early stage, we discuss three recently published studies, which feature significant differences in target antigen, CAR-T cell phenotype, route of administration and tumor response. We discuss the lessons, which may be learned from these studies and which may guide further progress in the field.

The combination of neoantigen quality and T lymphocyte infiltrates identifies glioblastomas with the longest survival

Glioblastoma (GBM) is resistant to multimodality therapeutic approaches. A high burden of tumor-specific mutant peptides (neoantigens) correlates with better survival and response to immunotherapies in selected solid tumors but how neoantigens impact clinical outcome in GBM remains unclear. Here, we exploit the similarity between tumor neoantigens and infectious disease-derived immune epitopes and apply a neoantigen fitness model for identifying high-quality neoantigens in a human pan-glioma dataset. We find that the neoantigen quality fitness model stratifies GBM patients with more favorable clinical outcome and, together with CD8+ T lymphocytes tumor infiltration, identifies a GBM subgroup with the longest survival, which displays distinct genomic and transcriptomic features. Conversely, neither tumor neoantigen burden from a quantitative model nor the isolated enrichment of CD8+ T lymphocytes were able to predict survival of GBM patients. This approach may guide optimal stratification of GBM patients for maximum response to immunotherapy.

Podoplanin Positive Myeloid Cells Promote Glioma Development by Immune Suppression

The dynamic and interactive tumor microenvironment is conceived as a considerable parameter in tumor development and therapy response. Implementing this knowledge in the development of future cancer treatments could provide novel options in the combat of highly aggressive and difficult-to-treat tumors such as gliomas. One compartment of the tumor microenvironment that has gained growing interest is the immune system. As endogenous defense machinery the immune system has the capacity to fight against cancer cells. This, however, is frequently circumvented by tumor cells engaging immune-regulatory mechanisms that disable tumor-directed immune responses. Thus, in order to unlock the immune system against cancer cells, it is crucial to characterize in great detail individual tumor-associated immune cell subpopulations and dissect whether and how they influence immune evasion. In this study we investigated the function of a tumor-associated myeloid cell subpopulation characterized by podoplanin expression on the development of high-grade glioma tumors. Here, we show that the deletion of podoplanin in myeloid cells results in increased (CD8⁺) T-cell infiltrates and significantly prolonged survival in an orthotopic transplantation model. In vitro co-cultivation experiments indicate a podoplanin-dependent transcriptional regulation of arginase-1, a well-known player in myeloid cell-mediated immune suppression. These findings identify podoplanin positive myeloid cells as one novel mediator of the glioma-induced immune suppression. Thus, the targeted ablation of podoplanin positive myeloid cells could be included in combinatorial cancer therapies to enhance immune-mediated tumor elimination.

Glioblastoma heterogeneity and the tumour microenvironment: implications for preclinical research and development of new treatments

Glioblastoma is the deadliest form of brain cancer. Aside from inadequate treatment options, one of the main reasons glioblastoma is so lethal is the rapid growth of tumour cells coupled with continuous cell invasion into surrounding healthy brain tissue. Significant intra- and inter-tumour heterogeneity associated with differences in the corresponding tumour microenvironments contributes greatly to glioblastoma progression. Within this tumour microenvironment, the extracellular matrix profoundly influences the way cancer cells become invasive, and changes to extracellular (pH and oxygen levels) and metabolic (glucose and lactate) components support glioblastoma growth. Furthermore, studies on clinical samples have revealed that the tumour microenvironment is highly immunosuppressive which contributes to failure in immunotherapy treatments. Although technically possible, many components of the tumour microenvironment have not yet been the focus of glioblastoma therapies, despite growing evidence of its importance to glioblastoma malignancy. Here, we review recent progress in the characterisation of the glioblastoma tumour microenvironment and the sources of tumour heterogeneity in human clinical material. We also discuss the latest advances in technologies for personalised and in vitro preclinical studies using brain organoid models to better model glioblastoma and its interactions with the surrounding healthy brain tissue, which may play an essential role in developing new and more personalised treatments for this aggressive type of cancer.

Ex vivo-expanded highly purified natural killer cells in combination with temozolomide induce antitumor effects in human glioblastoma cells in vitro

Glioblastoma is the leading malignant glioma with a poor prognosis. This study aimed to investigate the antitumor effects of natural killer cells in combination with temozolomide as the standard chemotherapeutic agent for glioblastoma. Using a simple, feeder-less, and chemically defined culture method, we expanded human peripheral blood mononuclear cells and assessed the receptor expression, natural killer cell activity, and regulatory T cell frequency in expanded cells. Next, using the standard human glioblastoma cell lines (temozolomide-sensitive U87MG, temozolomide-resistant T98G, and LN-18), we assessed the ligand expressions of receptors on natural killer cells. Furthermore, the antitumor effects of the combination of the expanded natural killer cells and temozolomide were assessed using growth inhibition assays, apoptosis detection assays, and senescence-associated β-galactosidase activity assays in the glioblastoma cell lines. Novel culture systems were sufficient to attain highly purified (>98%), expanded (>440-fold) CD3⁻/CD56⁺ peripheral blood-derived natural killer cells. We designated the expanded population as genuine induced natural killer cells. Genuine induced natural killer cells exhibited a high natural killer activity and low regulatory T cell frequency compared with lymphokine-activated killer cells. Growth inhibition assays revealed that genuine induced natural killer cells inhibited the glioblastoma cell line growth but enhanced temozolomide-induced inhibition effects in U87MG. Apoptosis detection assays revealed that genuine induced natural killer cells induced apoptosis in the glioblastoma cell lines. Furthermore, senescence-associated β-galactosidase activity assays revealed that temozolomide induced senescence in U87MG. Genuine induced natural killer cells induce apoptosis in temozolomide-sensitive and temozolomide-resistant glioblastoma cells and enhances temozolomide-induced antitumor effects in different mechanisms. Hence, the combination of genuine induced natural killer cells and temozolomide may prove to be a promising immunochemotherapeutic approach in patients with glioblastoma if the antitumor effects in vivo can be demonstrated.

Dynamic visualization of the whole process of cytotoxic T lymphocytes killing B16 tumor cells in vitro

Cytotoxic T lymphocytes (CTLs) play a key role in adoptive cell therapy (ACT) by destroying tumor cells. Although some mechanisms of CTLs killing tumor cells have already been revealed, the precise dynamic information of CTLs' interaction with tumor cells is still not known. Here, we used confocal microscopy to visualize the whole process of how CTLs kill tumor cells in vitro. According to imaging data, CTLs destroyed the target tumor cells rapidly and efficiently. Several CTLs surrounded one or more tumor cells, and the average time for CTLs destroying one or more tumor cells in vitro is dozens of minutes only. Our study displayed the temporal events of CTLs' interaction with tumor cells at the beginning up to the point of killing them. Furthermore, the imaging data presented strong cytotoxicity of CTLs toward the specific tumor cells. These results could help us to well understand the mechanism of CTLs' elimination of tumor cells and improve the efficacy of ACT in cancer immunotherapy.

The interplay among psychological distress, the immune system, and brain tumor patient outcomes

A malignant brain tumor diagnosis is often accompanied with intense feelings and can be associated with psychosocial conditions including depression, anxiety, and/or increased distress levels. Previous work has highlighted the impact of uncontrolled psychological distress among brain tumor patients. Given the negative impact of maladaptive psychosocial and biobehavioral factors on normal immune system functions, the question remains as to how psychological conditions potentially affect the brain tumor patient anti-tumor immune response. Since immunotherapy has yet to show efficacy at increasing malignant glioma patient survival in all randomized, phase III clinical trials to-date, this review provides new insights into the potential negative effects of chronic distress on brain tumor patient immune functions and outcomes.

Harnessing Radiation Biology to Augment Immunotherapy for Glioblastoma

Glioblastoma is the most common adult primary brain tumor and carries a dismal prognosis. Radiation is a standard first-line therapy, typically deployed following maximal safe surgical debulking, when possible, in combination with cytotoxic chemotherapy. For other systemic cancers, standard of care is being transformed by immunotherapies, including checkpoint-blocking antibodies targeting CTLA-4 and PD-1/PD-L1, with potential for long-term remission. Ongoing studies are evaluating the role of immunotherapies for GBM. Despite dramatic responses in some cases, randomized trials to date have not met primary outcomes. Challenges have been attributed in part to the immunologically "cold" nature of glioblastoma relative to other malignancies successfully treated with immunotherapy. Radiation may serve as a mechanism to improve tumor immunogenicity. In this review, we critically evaluate current evidence regarding radiation as a synergistic facilitator of immunotherapies through modulation of both the innate and adaptive immune milieu. Although current preclinical data encourage efforts to harness synergistic biology between radiation and immunotherapy, several practical and scientific challenges remain. Moreover, insights from radiation biology may unveil additional novel opportunities to help mobilize immunity against GBM.

Carbon ion radiotherapy boost in the treatment of glioblastoma: a randomized phase I/III clinical trial

Background

Glioblastoma (GBM) is a highly virulent tumor of the central nervous system, with a median survival < 15 months. Clearly, an improvement in treatment outcomes is needed. However, the emergence of these malignancies within the delicate brain parenchyma and their infiltrative growth pattern severely limit the use of aggressive local therapies. The particle therapy represents a new promising therapeutic approach to circumvent these prohibitive conditions with improved treatment efficacy.

Methods and design

Patients with newly diagnosed malignant gliomas will have their tumor tissue samples submitted for the analysis of the status of O-6-methylguanine-DNA methyltransferase (MGMT) promoter methylation. In Phase I, the patients will undergo an induction carbon ion radiotherapy (CIRT) boost followed by 60 GyE of proton irradiation with concurrent temozolomide (TMZ) at 75 mg/m². To determine the maximal dose of safe induction boost, the tolerance, and acute toxicity rates in a dose-escalation manner from 9 to 18 GyE in three fractions will be used. In Phase III, GBM-only patients will be randomized to receive either 60 GyE (2 GyE per fraction) of proton irradiation with concurrent TMZ (control arm) or a CIRT boost (dose determined in Phase I of this trial) followed by 60 GyE of proton irradiation with concurrent TMZ. The primary endpoints are overall survival (OS) and toxicity rates (acute and long-term). Secondary endpoints are progression-free survival (PFS), and tumor response (based upon assessment with C-methionine/fluoro-ethyl-tyrosine positron emission tomography [MET/FET PET] or magnetic resonance imaging [MRI] and detection of serologic immune markers). We hypothesize that the induction CIRT boost will result in a greater initial tumor-killing ability and prime the tumor microenvironment for enhanced immunologic tumor clearance, resulting in an expected 33% improvement in OS rates.

Discussion

The prognosis of GBM remains grim. The mechanism underpinning the poor prognosis of this malignancy is its chronic state of tumor hypoxia, which promotes both immunosuppression/immunologic evasion and radio-resistance. The unique physical and biological properties of CIRT are expected to overcome these microenvironmental limitations to confer an improved tumor-killing ability and anti-tumor immune response, which could result in an improvement in OS with minimal toxicity.

Trial registration number This trial has been registered with the China Clinical Trials Registry, and was allocated the number ChiCTR-OID-17013702.

Tumor-infiltrating immune cell subpopulations and programmed death ligand 1 (PD-L1) expression associated with clinicopathological and prognostic parameters in ependymoma

Ependymomas are biologically and clinically heterogeneous tumors of the central nervous system that have variable clinical outcomes. The status of the tumor immune microenvironment in ependymoma remains unclear. Immune cell subsets and programmed death ligand 1 (PD-L1) expression were measured in 178 classical ependymoma cases by immunohistochemistry using monoclonal antibodies that recognized tumor-infiltrating lymphocyte subsets (TILs; CD3, CD4, CD8, FOXP3, and CD20), tumor-associated macrophages (TAMs; CD68, CD163, AIF1), indoleamine 2,3-dioxygenase (IDO)+ cells and PD-L1-expressing tumor cells. Increases in CD3+ and CD8+ cell numbers were associated with a prolonged PFS. In contrast, increased numbers of FOXP3+ and CD68+ cells and a ratio of CD163/AIF1+ cells were significantly associated with a shorter PFS. An increase in the IDO+ cell number was associated with a significantly longer PFS. To consider the quantities of TILs, TAMs, and IDO+ cells together, the cases were clustered into 2 immune cell subgroups using a k-means clustering analysis. Immune cell subgroup A, which was defined by high CD3+, low CD68+ and high IDO+ cell counts, predicted a favorable PFS compared to subgroup B by univariate and multivariate analyses. We found six ependymoma cases expressing PD-L1. All these cases were supratentorial ependymoma, RELA fusion-positive (ST-RELA). PD-L1 expression showed no prognostic significance. This study showed that the analysis of tumor-infiltrating immune cells could aid in predicting the prognosis of ependymoma patients and in determining therapeutic strategies to target the tumor microenvironment. PD-L1 expression in the ST-RELA subgroup suggests that this marker has a potential added value for future immunotherapy treatments.

Metabolic and functional reprogramming of myeloid-derived suppressor cells and their therapeutic control in glioblastoma

Glioblastoma, also known as glioblastoma multi-forme, is the most common and deadliest form of high-grade malignant brain tumors with limited available treatments. Within the glioblastoma tumor microenvironment (TME), tumor cells, stromal cells, and infiltrating immune cells continuously interact and exchange signals through various secreted factors including cytokines, chemokines, growth factors, and metabolites. Simultaneously, they dynamically reprogram their metabolism according to environmental energy demands such as hypoxia and neo-vascularization. Such metabolic re-programming can determine fates and functions of tumor cells as well as immune cells. Ultimately, glioma cells in the TME transform immune cells to suppress anti-tumor immune cells such as T, natural killer (NK) cells, and dendritic cells (DC), and evade immune surveillance, and even to promote angiogenesis and tumor metastasis. Glioma-associated microglia/macrophages (GAMM) and myeloid-derived suppressor cells (MDSC) are most abundantly recruited and expanded myeloid lineage cells in glioblastoma TME and mainly lead to immunosuppression. In this review, of myeloid cells we will focus on MDSC as an important driver to induce immunosuppression in glioblastoma. Here, we review current literature on immunosuppressive functions and metabolic reprogramming of MDSCs in glioblastoma and discuss their metabolic pathways as potential therapeutic targets to improve current incurable glioblastoma treatment.

Immunothérapie des glioblastomes

IMMUNOTHERAPY IN GLIOBLASTOMAS

Targeting the immune system as a therapeutic strategy in solid tumors has shown great efficacy in various tumor types. However the role and success of this approach in glioblastomas remain to be determined. Recent studies demonstrated that central nervous system is no longer considered as an immunoprivileged sanctuary with impressive immune response without blood brain barrier's disruption. Improving our understanding of immune privilege in the central nervous system could lead to better treatment strategies in gliobastomas. This review focuses on describing the immune system in the central nervous system and immuno-therapeutic strategies under development in glioblastomas.

IL-15 is a component of the inflammatory milieu in the tumor microenvironment promoting antitumor responses

Previous studies have provided evidence that IL-15 expression within human tumors is crucial for optimal antitumor responses; however, the regulation of IL-15 within the tumor microenvironment (TME) is unclear. We report herein, in analyses of mice implanted with various tumor cell lines, soluble IL-15/IL-15Rα complexes (sIL-15 complexes) are abundant in the interstitial fluid of tumors with expression preceding the infiltration of tumor-infiltrating lymphocytes. Moreover, IL-15 as well as type I IFN, which regulates IL-15, was required for establishing normal numbers of CD8 T cells and natural killer cells in tumors. Depending on tumor type, both the tumor and the stroma are sources of sIL-15 complexes. In analyses of IL-15 reporter mice, most myeloid cells in the TME express IL-15 with CD11b⁺Ly6C^hi cells being the most abundant, indicating there is a large source of IL-15 protein in tumors that lies sequestered within the tumor stroma. Despite the abundance of IL-15-expressing cells, the relative levels of sIL-15 complexes are low in advanced tumors but can be up-regulated by local stimulator of IFN genes (STING) activation. Furthermore, while treatment of tumors with STING agonists leads to tumor regression, optimal STING-mediated immunity and regression of distant secondary tumors required IL-15 expression. Overall, our study reveals the dynamic regulation of IL-15 in the TME and its importance in antitumor immunity. These findings provide insight into an unappreciated attribute of the tumor landscape that contributes to antitumor immunity, which can be manipulated therapeutically to enhance antitumor responses.

NK Cell-Based Glioblastoma Immunotherapy

Glioblastoma (GB) is the most aggressive and most common malignant primary brain tumor diagnosed in adults. GB shows a poor prognosis and, unfortunately, current therapies are unable to improve its clinical outcome, imposing the need for innovative therapeutic approaches. The main reason for the poor prognosis is the great cell heterogeneity of the tumor mass and its high capacity for invading healthy tissues. Moreover, the glioblastoma microenvironment is capable of suppressing the action of the immune system through several mechanisms such as recruitment of cell modulators. Development of new therapies that avoid this immune evasion could improve the response to the current treatments for this pathology. Natural Killer (NK) cells are cellular components of the immune system more difficult to deceive by tumor cells and with greater cytotoxic activity. Their use in immunotherapy gains strength because they are a less toxic alternative to existing therapy, but the current research focuses on mimicking the NK attack strategy. Here, we summarize the most recent studies regarding molecular mechanisms involved in the GB and immune cells interaction and highlight the relevance of NK cells in the new therapeutic challenges.

Fates of CD8+ T cells in Tumor Microenvironment

Studies have reported a positive correlation between elevated CD8+ T cells in the tumor microenvironment (TME) and good prognosis in cancer. However, the mechanisms linking T cell tumor-infiltration and tumor rejection are yet to be fully understood. The cells and factors of the TME facilitate tumor development in various ways. CD8+ T cell function is influenced by a number of factors, including CD8+ T cell trafficking and localization into tumor sites; as well as CD8+ T cell growth and differentiation. This review highlights recent literature as well as currently evolving concepts regarding the fates of CD8+ T cells in the TME from three different aspects CD8+ T cell trafficking, differentiation and function. A thorough understanding of factors contributing to the fates of CD8+ T cells will allow researchers to develop new strategies and improve on already existing strategies to facilitate CD8+ T cell mediated anti-tumor function, impede T cell dysfunction and modulate the TME into a less immunosuppressive TME.

Irradiation to Improve the Response to Immunotherapeutic Agents in Glioblastomas

Purpose

Glioblastoma (GBM) remains an incurable disease despite extensive treatment with surgical resection, irradiation, and temozolomide. In line with many other forms of aggressive cancers, GBM is currently under consideration as a target for immunotherapy. However, GBM tends to be nonimmunogenic and exhibits a microenvironment with few or no effector T cells, a relatively low nonsynonymous somatic mutational load, and a low predicted neoantigen burden. GBM also exploits a multitude of immunosuppressive strategies.

Methods and Materials

A number of immunotherapeutic approaches have been tested with disappointing results. A rationale exists to combine immunotherapy and radiation therapy, which can induce an immunogenic form of cell death with T-cell activation and tumor infiltration.

Results

Various immunotherapy agents, including immune checkpoint modulators, transforming growth factor beta receptor inhibitors, and indoleamine-2,3-dioxygenase inhibitors, have been evaluated with irradiation in preclinical GBM models, with promising results, and are being further tested in clinical trials.

Conclusions

This review aims to present the basic rationale behind this emerging complementary therapeutic approach in GBM, appraise the current preclinical and clinical data, and discuss the future challenges in improving the antitumor immune response.

CART Immunotherapy: Development, Success, and Translation to Malignant Gliomas and Other Solid Tumors

T cell chimeric antigen receptor (CAR) technology has allowed for the introduction of a high degree of tumor selectivity into adoptive cell transfer therapies. Evolution of this technology has produced a robust antitumor immunotherapeutic strategy that has resulted in dramatic outcomes in liquid cancers. CAR-expressing T-cells (CARTs) targeting CD19 and CD20 have been successfully used in the treatment of hematologic malignancies, producing sustained tumor regressions in a majority of treated patients. These encouraging results have led to a historic and unprecedented FDA approval of CTL019, Novartis' CAR T-cell therapy for the treatment of children and young adults with relapsed or refractory B-cell acute lymphoblastic leukemia (ALL). However, the translation of this technology to solid tumors, like malignant gliomas (MG), has thus far been unsuccessful. This review provides a timely analysis of the factors leading to the success of CART immunotherapy in the setting of hematologic malignancies, barriers limiting its success in the treatment of solid tumors, and approaches to overcome these challenges and allow the application of CART immunotherapy as a treatment modality for refractory tumors, like malignant gliomas, that are in desperate need of effective therapies.

Low-dose irradiated mesenchymal stromal cells break tumor defensive properties in vivo

Solid tumors, including gliomas, still represent a challenge to clinicians and first line treatments often fail, calling for new paradigms in cancer therapy. Novel strategies to overcome tumor resistance are mainly represented by multi-targeted approaches, and cell vector-based therapy is one of the most promising treatment modalities under development. Here, we show that mouse bone marrow-derived mesenchymal stromal cells (MSCs), when primed with low-dose irradiation (irMSCs), undergo changes in their immunogenic and angiogenic capacity and acquire anti-tumoral properties in a mouse model of glioblastoma (GBM). Following grafting in GL261 glioblastoma, irMSCs migrate extensively and selectively within the tumor and infiltrate predominantly the peri-vascular niche, leading to rejection of established tumors and cure in 29% of animals. The therapeutic radiation dose window is narrow, with effects seen between 2 and 15 Gy, peaking at 5 Gy. A single low-dose radiation decreases MSCs inherent immune suppressive properties in vitro as well as shapes their immune regulatory ability in vivo. Intra-tumorally grafted irMSCs stimulate the immune system and decrease immune suppression. Additionally, irMSCs enhance peri-tumoral reactive astrocytosis and display anti-angiogenic properties. Hence, the present study provides strong evidence for a therapeutic potential of low-dose irMSCs in cancer as well as giving new insight into MSC biology and applications.

Multidimensional communication in the microenvirons of glioblastoma

Glioblastomas are heterogeneous and invariably lethal tumours. They are characterized by genetic and epigenetic variations among tumour cells, which makes the development of therapies that eradicate all tumour cells challenging and currently impossible. An important component of glioblastoma growth is communication with and manipulation of other cells in the brain environs, which supports tumour progression and resistance to therapy. Glioblastoma cells recruit innate immune cells and change their phenotype to support tumour growth. Tumour cells also suppress adaptive immune responses, and our increasing understanding of how T cells access the brain and how the tumour thwarts the immune response offers new strategies for mobilizing an antitumour response. Tumours also subvert normal brain cells - including endothelial cells, neurons and astrocytes - to create a microenviron that favours tumour success. Overall, after glioblastoma-induced phenotypic modifications, normal cells cooperate with tumour cells to promote tumour proliferation, invasion of the brain, immune suppression and angiogenesis. This glioblastoma takeover of the brain involves multiple modes of communication, including soluble factors such as chemokines and cytokines, direct cell-cell contact, extracellular vesicles (including exosomes and microvesicles) and connecting nanotubes and microtubes. Understanding these multidimensional communications between the tumour and the cells in its environs could open new avenues for therapy.

Glioblastoma Stem-Like Cells Are More Susceptible Than Differentiated Cells to Natural Killer Cell Lysis Mediated Through Killer Immunoglobulin-Like Receptors-Human Leukocyte Antigen Ligand Mismatch and Activation Receptor-Ligand Interactions

Glioblastoma (GBM) is the most aggressive brain malignancy in adults, where survival is approximately 14.6 months. Novel therapies are urgently needed and immunotherapy has hailed a new dawn for treatment of solid tumors. Natural killer (NK) cells may be amenable therapeutic effectors against heterogeneous GBM, since they also do not require co-stimulation and antigen specificity. However, it is unclear how culture media routinely used in pre-clinical studies affect GBM cell responses to NK-mediated cytotoxicity. We hypothesized that the culture medium would affect GBM cell phenotype, proliferation, and responses to NK cytotoxicity. We investigated in paired analyses n = 6 patient-derived primary GBM cells propagated in stem cell or serum-containing medium for morphology, proliferation, as well as susceptibility to NK cytolysis and related this to expression of surface and intracellular lineage markers, as well as ligands for NK cell activating and inhibitory receptors. We genotyped the GBM cells for human leukocyte antigen (HLA) as well as the killer immunoglobulin-like receptors (KIR) of the n = 6 allogeneic NK cells used as effector cells. Culture in serum-containing medium induced a switch in GBM cell morphology from suspension neuropsheres to adherent epithelial-mesenchymal-like phenotypes, which was partially reversible. The differentiated cells diminished expression of nestin, CD133 (prominin-1), and A2B5 putative glioma stem-cell markers, attenuated growth, diminished expression of ligands for activating NK cell receptors, while upregulating class I HLA ligands for NK cell inhibitory receptors. When maintained in serum-containing medium, fewer GBM cells expressed intercellular cell adhesion molecule-1 (ICAM-1) and were less susceptible to lysis by NK cells expressing αLβ2 integrin receptor (LFA-1), mediated through combination of inhibitory KIR-HLA ligand mismatch and diminished activation receptor-ligand interactions compared to cells maintained in stem cell media. We conclude that development of preclinical immunotherapy strategies against GBM should not use cells propagated in serum-containing media to avoid misinterpretation of potential therapeutic responses.

Molecular, Pathological, Radiological, and Immune Profiling of Non-brainstem Pediatric High-Grade Glioma from the HERBY Phase II Randomized Trial

The HERBY trial was a phase II open-label, randomized, multicenter trial evaluating bevacizumab (BEV) in addition to temozolomide/radiotherapy in patients with newly diagnosed non-brainstem high-grade glioma (HGG) between the ages of 3 and 18 years. We carried out comprehensive molecular analysis integrated with pathology, radiology, and immune profiling. In post-hoc subgroup analysis, hypermutator tumors (mismatch repair deficiency and somatic POLE/POLD1 mutations) and those biologically resembling pleomorphic xanthoastrocytoma ([PXA]-like, driven by BRAF_V600E or NF1 mutation) had significantly more CD8+ tumor-infiltrating lymphocytes, and longer survival with the addition of BEV. Histone H3 subgroups (hemispheric G34R/V and midline K27M) had a worse outcome and were immune cold. Future clinical trials will need to take into account the diversity represented by the term "HGG" in the pediatric population.

Serglycin as a potential biomarker for glioma: association of serglycin expression, extent of mast cell recruitment and glioblastoma progression

Serglycin is an intracellular proteoglycan with a unique ability to adopt highly divergent structures by glycosylation with variable types of glycosaminoglycans (GAGs) when expressed by different cell types. Serglycin is overexpressed in aggressive cancers suggesting its protumorigenic role. In this study, we explored the expression of serglycin in human glioma and its correlation with survival and immune cell infiltration. We demonstrate that serglycin is expressed in glioma and that increased expression predicts poor survival of patients. Analysis of serglycin expression in a large cohort of low- and high-grade human glioma samples reveals that its expression is grade dependent and is positively correlated with mast cell (MC) infiltration. Moreover, serglycin expression in patient-derived glioma cells is significantly increased upon MC co-culture. This is also accompanied by increased expression of CXCL12, CXCL10, as well as markers of cancer progression, including CD44, ZEB1 and vimentin.In conclusion, these findings indicate the importance of infiltrating MCs in glioma by modulating signaling cascades involving serglycin, CD44 and ZEB1. The present investigation reveals serglycin as a potential prognostic marker for glioma and demonstrates an association with the extent of MC recruitment and glioma progression, uncovering potential future therapeutic opportunities for patients.

Role of Macrophages in Brain Tumor Growth and Progression

The role of macrophages in the growth and the progression of tumors has been extensively studied in recent years. A large body of data demonstrates that macrophage polarization plays an essential role in the growth and progression of brain tumors, such as gliomas, meningiomas, and medulloblastomas. The brain neoplasm cells have the ability to influence the polarization state of the tumor associated macrophages. In turn, innate immunity cells have a decisive role through regulation of the acquired immune response, but also through humoral cross-talking with cancer cells in the tumor microenvironment. Neoangiogenesis, which is an essential element in glial tumor progression, is even regulated by the tumor associated macrophages, whose activity is linked to other factors, such as hypoxia. In addition, macrophages play a decisive role in establishing the entry into the bloodstream of cancer cells. As is well known, the latter phenomenon is also present in brain tumors, even if they only rarely metastasize. Looking ahead in the future, we can imagine that characterizing the relationships between tumor and tumor associated macrophage, as well as the study of circulating tumor cells, could give us useful tools in prognostic evaluation and therapy. More generally, the study of innate immunity in brain tumors can boost the development of new forms of immunotherapy.

The Complex Interplay between Chronic Inflammation, the Microbiome, and Cancer: Understanding Disease Progression and What We Can Do to Prevent It

Cancer is a multifaceted condition, in which a senescent cell begins dividing in an irregular manner due to various factors such as DNA damage, growth factors and inflammation. Inflammation is not typically discussed as carcinogenic; however, a significant percentage of cancers arise from chronic microbial infections and damage brought on by chronic inflammation. A hallmark cancer-inducing microbe is Helicobacter pylori and its causation of peptic ulcers and potentially gastric cancer. This review discusses the recent developments in understanding microbes in health and disease and their potential role in the progression of cancer. To date, microbes can be linked to almost every cancer, including colon, pancreatic, gastric, and even prostate. We discuss the known mechanisms by which these microbes can induce cancer growth and development and how inflammatory cells may contribute to cancer progression. We also discuss new treatments that target the chronic inflammatory conditions and their associated cancers, and the impact microbes have on treatment success. Finally, we examine common dietary misconceptions in relation to microbes and cancer and how to avoid getting caught up in the misinterpretation and over inflation of the results.

Vacquinol-1 inducible cell death in glioblastoma multiforme is counter regulated by TRPM7 activity induced by exogenous ATP

Glioblastomas (GBM) are the most malignant brain tumors in humans and have a very poor prognosis. New therapeutic options are urgently needed. A novel drug, Vacquinol-1 (Vac), a quinolone derivative, displays promising properties by inducing rapid cell death in GBM but not in non-transformed tissues. Features of this type of cell death are compatible with a process termed methuosis. Here we tested Vac on a highly malignant glioma cell line observed by long-term video microscopy. Human dental-pulp stem cells (DPSCs) served as controls. A major finding was that an exogenous ATP concentration of as little as 1 μM counter regulated the Vac-induced cell death. Studies using carvacrol, an inhibitor of transient receptor potential cation channel, subfamily M, member 7 (TRPM7), demonstrated that the ATP-inducible inhibitory effect is likely to be via TRPM7. Exogenous ATP is of relevance in GBM with large necrotic areas. Our results support the use of GBM cultures with different grades of malignancy to address their sensitivity to methuosis. The video-microscopy approach presented here allows decoding of signaling pathways as well as mechanisms of chemotherapeutic resistance by long-term observation. Before implementing Vac as a novel therapeutic drug in GBM, cells from each individual patient need to be assessed for their ATP sensitivity. In summary, the current investigation supports the concept of methuosis, described as non-apoptotic cell death and a promising approach for GBM treatment. Tissue-resident ATP/necrosis may interfere with this cell-death pathway but can be overcome by a natural compound, carvacrol that even penetrates the blood-brain barrier.

CD8+ T Cells and NK Cells: Parallel and Complementary Soldiers of Immunotherapy

CD8+ T cells and NK cells are both cytotoxic effector cells of the immune system, but the recognition, specificity, sensitivity, and memory mechanisms are drastically different. While many of these topics have been extensively studied in CD8+ T cells, very little is known about NK cells. Current cancer immunotherapies mainly focus on CD8+ T cells, but have many issues of toxicity and efficacy. Given the heterogeneous nature of cancer, personalized cancer immunotherapy that integrates the power of both CD8+ T cells in adaptive immunity and NK cells in innate immunity might be the future direction, along with precision targeting and effective delivery of tumor-specific, memory CD8+ T cells and NK cells.

Immune evasion mediated by PD-L1 on glioblastoma-derived extracellular vesicles

Binding of programmed death ligand-1 (PD-L1) to programmed cell death protein-1 (PD1) leads to cancer immune evasion via inhibition of T cell function. One of the defining characteristics of glioblastoma, a universally fatal brain cancer, is its profound local and systemic immunosuppression. Glioblastoma has also been shown to generate extracellular vesicles (EVs), which may play an important role in tumor progression. We thus hypothesized that glioblastoma EVs may be important mediators of immunosuppression and that PD-L1 could play a role. We show that glioblastoma EVs block T cell activation and proliferation in response to T cell receptor stimulation. PD-L1 was expressed on the surface of some, but not of all, glioblastoma-derived EVs, with the potential to directly bind to PD1. An anti-PD1 receptor blocking antibody significantly reversed the EV-mediated blockade of T cell activation but only when PD-L1 was present on EVs. When glioblastoma PD-L1 was up-regulated by IFN-γ, EVs also showed some PD-L1-dependent inhibition of T cell activation. PD-L1 expression correlated with the mesenchymal transcriptome profile and was anatomically localized in the perinecrotic and pseudopalisading niche of human glioblastoma specimens. PD-L1 DNA was present in circulating EVs from glioblastoma patients where it correlated with tumor volumes of up to 60 cm3. These results suggest that PD-L1 on EVs may be another mechanism for glioblastoma to suppress antitumor immunity and support the potential of EVs as biomarkers in tumor patients.

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.

Transcriptional characterization of immunological infiltrates and their relation with glioblastoma patients overall survival

Introduction: Several cell populations from the peripheral immune system interact to create a complex immunologic status during glioblastoma growth and response to therapy. The aim of this study was to integrate the impact of different immune cell populations present in glioblastoma tumor microenvironment on overall survival. Methodology: Gene expression and clinical data were generated by The Cancer Genome Atlas and previously reported meta-signatures representing cells of the immune system were used. The relationship between meta-signatures was evaluated through Pearson's correlation analyses. Survival analyses were performed through Kaplan-Meier plots and Cox regression model. Results and discussion: Meta-signatures corresponding to infiltrating immune cells with immunosuppressive roles, such as macrophages, NK and NK T cells, MDSCs and Tregs, correlated with poorer patient prognosis. Meta-signatures related to CD8+ T cells predicted improved survival only in patients with low immunosuppressive meta-signatures. By clustering the meta-signatures we found that the cluster containing high meta-signatures of macrophages, MDSCs and Tregs demonstrated the worst prognosis. Conclusion: Integrating the information provided by transcriptional signatures of immunological aspects is fundamental in understanding the impact of the immune system on patient survival. We found a predictive impact on survival with positive role for CD8 and negative roles for macrophages, MDSC, Tregs, NK and NK-T in glioblastoma patients. Understanding these regulatory and stimulatory factors of patients' immune system is essential to delineate an effective strategy to increase the anti-tumor immune response and to generate potential clinical benefits.

T-Cell Exhaustion Signatures Vary with Tumor Type and Are Severe in Glioblastoma

Purpose: T-cell dysfunction is a hallmark of glioblastoma (GBM). Although anergy and tolerance have been well characterized, T-cell exhaustion remains relatively unexplored. Exhaustion, characterized in part by the upregulation of multiple immune checkpoints, is a known contributor to failures amid immune checkpoint blockade, a strategy that has lacked success thus far in GBM. This study is among the first to examine, and credential as bona fide, exhaustion among T cells infiltrating human and murine GBM.Experimental Design: Tumor-infiltrating and peripheral blood lymphocytes (TILs and PBLs) were isolated from patients with GBM. Levels of exhaustion-associated inhibitory receptors and poststimulation levels of the cytokines IFNγ, TNFα, and IL2 were assessed by flow cytometry. T-cell receptor Vβ chain expansion was also assessed in TILs and PBLs. Similar analysis was extended to TILs isolated from intracranial and subcutaneous immunocompetent murine models of glioma, breast, lung, and melanoma cancers.Results: Our data reveal that GBM elicits a particularly severe T-cell exhaustion signature among infiltrating T cells characterized by: (1) prominent upregulation of multiple immune checkpoints; (2) stereotyped T-cell transcriptional programs matching classical virus-induced exhaustion; and (3) notable T-cell hyporesponsiveness in tumor-specific T cells. Exhaustion signatures differ predictably with tumor identity, but remain stable across manipulated tumor locations.Conclusions: Distinct cancers possess similarly distinct mechanisms for exhausting T cells. The poor TIL function and severe exhaustion observed in GBM highlight the need to better understand this tumor-imposed mode of T-cell dysfunction in order to formulate effective immunotherapeutic strategies targeting GBM. Clin Cancer Res; 24(17); 4175-86. ©2018 AACRSee related commentary by Jackson and Lim, p. 4059.

Current state and future prospects of immunotherapy for glioma

There is a large unmet need for effective therapeutic approaches for glioma, the most malignant brain tumor. Clinical and preclinical studies have enormously expanded our knowledge about the molecular aspects of this deadly disease and its interaction with the host immune system. In this review we highlight the wide array of immunotherapeutic interventions that are currently being tested in glioma patients. Given the molecular heterogeneity, tumor immunoediting and the profound immunosuppression that characterize glioma, it has become clear that combinatorial approaches targeting multiple pathways tailored to the genetic signature of the tumor will be required in order to achieve optimal therapeutic efficacy.

NKG2D ligands in glioma stem-like cells: expression in situ and in vitro

Glioblastoma multiforme (GBM) is a highly malignant brain tumor. Tumor stem cells have a major influence on tumor malignancy, and immunological escape mechanisms, involving the Natural Killer Group 2, member D (NKG2D) receptor-ligand-system, are key elements in tumor immuno-surveillance. We analyzed the expression profile and localization of NKG2D ligands (NKG2DL) and embryonic and neural stem cell markers in solid human GBM and stem-like cells isolated from glioma cell lines by qRT-PCR and immunohistochemistry, including quantitative analysis. We also evaluated the effect of Temozolomide (TMZ), the standard chemotherapeutic agent used in GBM therapy, on NKG2DL expression. NKG2DL-positive cells were mostly found scattered and isolated, were detectable in glial fibrillary acidic protein (GFAP)-positive tumor regions and partly in the penumbra of tumor vessels. NKG2DL were found in a distinct tumor stem-like cell subpopulation and were broadly costained with each other. Quantitative analysis revealed, that dependent on the individual NKG2DL investigated, cell portions costained with different stem cell markers varied between small (Musashi-1) and high (KLf-4) amounts. However, a costaining of NKG2DL with CD3γ, typically found in T cells, was also observable, whereas CD11b as a marker for tumor micoglia cells was only rarely costained with NKG2DL. Stem-like cells derived from the glioma cell lines T98G and U251MG showed a distinct expression pattern of NKG2DL and stem cell markers, which seemed to be balanced in a cell line-specific way. With differentiation, T98G displayed less NKG2DL, whereas in U251MG, only expression of most stem cell markers decreased. In addition, stimulation with TMZ led to a significant upregulation of NKG2DL in stem-like cells of both lines. As stem-like glioma cells tend to show a higher expression of NKG2DL than more differentiated tumor cells and TMZ treatment supports upregulation of NKG2DL, the NKG2D system might play an important role in tumor stem cell survival and in GBM therapy.

Immunologic and gene expression profiles of spontaneous canine oligodendrogliomas

Malignant glioma (MG), the most common primary brain tumor in adults, is extremely aggressive and uniformly fatal. Several treatment strategies have shown significant preclinical promise in murine models of glioma; however, none have produced meaningful clinical responses in human patients. We hypothesize that introduction of an additional preclinical animal model better approximating the complexity of human MG, particularly in interactions with host immune responses, will bridge the existing gap between these two stages of testing. Here, we characterize the immunologic landscape and gene expression profiles of spontaneous canine glioma and evaluate its potential for serving as such a translational model. RNA in situ hybridization, flowcytometry, and RNA sequencing were used to evaluate immune cell presence and gene expression in healthy and glioma-bearing canines. Similar to human MGs, canine gliomas demonstrated increased intratumoral immune cell infiltration (CD4+, CD8+ and CD4+Foxp3+ T cells). The peripheral blood of glioma-bearing dogs also contained a relatively greater proportion of CD4+Foxp3+ regulatory T cells and plasmacytoid dendritic cells. Tumors were strongly positive for PD-L1 expression and glioma-bearing animals also possessed a greater proportion of immune cells expressing the immune checkpoint receptors CTLA-4 and PD-1. Analysis of differentially expressed genes in our canine populations revealed several genetic changes paralleling those known to occur in human disease. Naturally occurring canine glioma has many characteristics closely resembling human disease, particularly with respect to genetic dysregulation and host immune responses to tumors, supporting its use as a translational model in the preclinical testing of prospective anti-glioma therapies proven successful in murine studies.

FOXOs in cancer immunity: Knowns and unknowns

In the tumor microenvironment (TME), cancer cells, stromal cells, and immune cells, along with their extracellular factors, have profound effects on either promoting or repressing anti-cancer immunity. Accumulating evidence has shown the paradoxical intrinsic role of the Forkhead box O (FOXO) family of transcription factors in cancer, which can act as a tumor repressor while also maintaining cancer stem cells. FOXOs also regulate cancer immunity. FOXOs promote antitumor activity through negatively regulating the expression of immunosuppressive proteins, such as programmed death 1 ligand 1 (PD-L1), and vascular endothelial growth factor (VEGF) in tumor cells or stromal cells, which can shape an immunotolerant state in the TME. FOXOs also intrinsically control the anti-tumor immune response as well as the homeostasis and development of immune cells, including T cells, B cells, natural killer (NK) cells, macrophages, and dendritic cells. As a cancer repressor, reviving the activity of Foxo1 forces tumor-infiltrating activated regulatory T (T_reg) cells to egress from tumor tissues. As a promoter of cancer development, Foxo3 and Foxo1 negatively regulate cytotoxicity of both CD8⁺ T cells and NK cells against tumor cells. In this review, we focus on the complex role of FOXOs in regulating cancer immunity due to the various roles that they play in cancer cells, stromal cells, and immune cells. We also speculate on some possible additional roles of FOXOs in cancer immunity based on findings regarding FOXOs in non-cancer settings, such as infectious disease.

Analysis of immunobiologic markers in primary and recurrent glioblastoma

Glioblastoma (GBM) generates a varied immune response and understanding the immune microenvironment may lead to novel immunotherapy treatments modalities. The goal of this study was to evaluate the expression of immunologic markers of potential clinical significance in primary versus recurrent GBM and assess the relationship between these markers and molecular characteristics of GBM. Human GBM samples were evaluated and analyzed with immunohistochemistry for multiple immunobiologic markers (CD3, CD8, FoxP3, CD68, CD163, PD1, PDL1, CTLA4, CD70). Immunoreactivity was analyzed using Aperio software. Degree of strong positive immunoreactivity within the tumor was compared to patient and tumor characteristics including age, gender, MGMT promoter methylation status, and ATRX, p53, and IDH1 mutation status. Additionally, the TCGA database was used to perform similar analysis of these factors in GBM using RNA-seq by expectation-maximization. Using odds ratios, IDH1 mutated GBM had statistically significant decreased expression of CD163 and CD70 and a trend for decreased PD1, CTLA4, and Foxp3. ATRX-mutated GBMs exhibited statistically significant increased CD3 immunoreactivity, while those with p53 mutations were found to have significantly increased CTLA4 immunoreactivity. The odds of having strong CD8 and CD68 reactivity was significantly less in MGMT methylated tumors. No significant difference was identified in any immune marker between the primary and recurrent GBM, nor was a significant change in immunoreactivity identified among age intervals. TCGA analysis corroborated findings related to the differential immune profile of IDH1 mutant, p53 mutant, and MGMT unmethylated tumors. Immunobiologic markers have greater association with the molecular characteristics of the tumor than with primary/recurrent status or age.

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.

Environmental stimuli shape microglial plasticity in glioma

In glioma, microglia and infiltrating macrophages are exposed to factors that force them to produce cytokines and chemokines, which contribute to tumor growth and to maintaining a pro-tumorigenic, immunosuppressed microenvironment. We demonstrate that housing glioma-bearing mice in enriched environment (EE) reverts the immunosuppressive phenotype of infiltrating myeloid cells, by modulating inflammatory gene expression. Under these conditions, the branching and patrolling activity of myeloid cells is increased, and their phagocytic activity is promoted. Modulation of gene expression depends on interferon-(IFN)-γ produced by natural killer (NK) cells. This modulation disappears in mice depleted of NK cells or lacking IFN-γ, and was mimicked by exogenous interleukin-15 (IL-15). Further, we describe a key role for brain-derived neurotrophic factor (BDNF) that is produced in the brain of mice housed in EE, in mediating the expression of IL-15 in CD11b⁺ cells. These data define novel mechanisms linking environmental cues to the acquisition of a pro-inflammatory, anti-tumor microenvironment in mouse brain.

Chimeric Antigen Receptors T Cell Therapy in Solid Tumor: Challenges and Clinical Applications

Adoptive cellular immunotherapy (ACT) employing engineered T lymphocytes expressing chimeric antigen receptors (CARs) has demonstrated promising antitumor effects in advanced hematologic cancers, such as relapsed or refractory acute lymphoblastic leukemia, chronic lymphocytic leukemia, and non-Hodgkin lymphoma, supporting the translation of ACT to non-hematological malignancies. Although CAR T cell therapy has made remarkable strides in the treatment of patients with certain hematological cancers, in solid tumors success has been limited likely due to heterogeneous antigen expression, immunosuppressive networks in the tumor microenvironment limiting CAR T cell function and persistence, and suboptimal trafficking to solid tumors. Here, we outline specific approaches to overcome barriers to CAR T cell effectiveness in the context of the tumor microenvironment and offer our perspective on how expanding the use of CAR T cells in solid tumors may require modifications in CAR T cell design. We anticipate these modifications will further expand CAR T cell therapy in clinical practice.

Poly(I:C) primes primary human glioblastoma cells for an immune response invigorated by PD-L1 blockade

Prognosis of glioblastoma remains dismal, underscoring the need for novel therapies. Immunotherapy is generating promising results, but requires combination strategies to unlock its full potential. We investigated the immunomodulatory capacities of poly(I:C) on primary human glioblastoma cells and its combinatorial potential with programmed death ligand (PD-L) blockade. In our experiments, poly(I:C) stimulated expression of both PD-L1 and PD-L2 on glioblastoma cells, and a pro-inflammatory secretome, including type I interferons (IFN) and chemokines CXCL9, CXCL10, CCL4 and CCL5. IFN-β was partially responsible for the elevated PD-1 ligand expression on these cells. Moreover, real-time PCR and chloroquine-mediated blocking experiments indicated that poly(I:C) triggered Toll-like receptor 3 to elicit its effect. Cocultures of poly(I:C)-treated glioblastoma cells with peripheral blood mononuclear cells enhanced lymphocytic activation (CD69, IFN-γ) and cytotoxic capacity (CD107a, granzyme B). Additional PD-L1 blockade further propagated immune activation. Besides activating immunity, poly(I:C)-treated glioblastoma cells also doubled the attraction of CD8⁺ T cells, and to a lesser extent CD4⁺ T cells, via a mechanism which included CXCR3 and CCR5 ligands. Our results indicate that by triggering glioblastoma cells, poly(I:C) primes the tumor microenvironment for an immune response. Secreted cytokines allow for immune activation while chemokines attract CD8⁺ T cells to the front, which are postulated as a prerequisite for effective PD-1/PD-L1 blockade. Accordingly, additional blockade of the concurrently elevated tumoral PD-L1 further reinforces the immune activation. In conclusion, our data proposes poly(I:C) treatment combined with PD-L1 blockade to invigorate the immune checkpoint inhibition response in glioblastoma.

Development of a reliable and accurate algorithm to quantify the tumor immune stroma (QTiS) across tumor types

The tumor microenvironment plays an important role in the tumor biology. Overall survival of tumor patients after resection is influenced by tumor-infiltrating lymphocytes (TILs) as a component of the tumor stroma. However, it is not clear how to assess TILs in the tumor stroma due to heterogeneous methods in different cancer types. Therefore, we present a novel Quantification of the Tumor immune Stroma (QTiS) Algorithm to reliably and accurately quantify cells in the tumor stroma. Immunohistochemical staining of CD3 and CD8 cells in sections of metastatic colorectal cancer (mCRC), ovarian cancer (OvCa), hepatocellular carcinoma (HCC), and pancreatic ductal adenocarcinoma (PDAC), alltogether N = 80, was performed. Hot spots of infiltrating immune cells are reported in the literature. Reliability of the hot spot identification of TILs was examined by two blinded observers. Accuracy was tested in 1 and 3 hot spots using computed counting methods (ZEN 2 software counting (ZC), ImageJ software with subjective threshold (ISC) and ImageJ with color deconvolution (IAC)) and compared to manual counting. All tumor types investigated showed an accumulation of TILs in the tumor stroma (peri- and intratumoral). Reliability between observers indicated a high level consistency. Accuracy for CD8+/CD3+ ratio and absolute cell count required 1 and 3 hot spots, respectively. ISC was found to be the best for paraffin sections, whereas IAC was ideal for frozen sections. ImageJ software is cost-effective and yielded the best results. In conclusion, an algorithm for quantification of tumoral stroma could be established. With this QTiS Algorithm counting of tumor stromal cells is reliable, accurate, and cost-effective.

CD4+ and Perivascular Foxp3+ T Cells in Glioma Correlate with Angiogenesis and Tumor Progression

Background

Angiogenesis and immune cell infiltration are key features of gliomas and their manipulation of the microenvironment, but their prognostic significance remains indeterminate. We evaluate the interconnection between tumor-infiltrating lymphocyte (TIL) and tumor blood-vasculatures in the context of glioma progression.

Methods

Paired tumor tissues of 44 patients from three tumor-recurrent groups: diffuse astrocytomas (DA) recurred as DA, DA recurred as glioblastomas (GBM), and GBM recurred as GBM were evaluated by genetic analysis, immunohistochemistry for tumor blood vessel density, TIL subsets, and clinical outcomes. These cells were geographically divided into perivascular and intratumoral TILs. Associations were examined between these TILs, CD34+ tumor blood vessels, and clinical outcomes. To determine key changes in TIL subsets, microarray data of 15-paired tumors from patients who failed antiangiogenic therapy- bevacizumab, and 16-paired tumors from chemo-naïve recurrent GBM were also evaluated and compared.

Results

Upon recurrence in primary gliomas, similar kinetic changes were found between tumor blood vessels and each TIL subset in all groups, but only CD4+ including Foxp3+ TILs, positively correlated with the density of tumor blood vessels. CD4 was the predominant T cell population based on the expression of gene-transcripts in primary GBMs, and increased activated CD4+ T cells were revealed in Bevacizumab-resistant recurrent tumors (not in chemo-naïve recurrent tumors). Among these TILs, 2/3 of them were found in the perivascular niche; Foxp3+ T cells in these niches not only correlated with the tumor vessels but were also an independent predictor of shortened recurrence-free survival (RFS) (HR = 4.199, 95% CI 1.522–11.584, p = 0.006).

Conclusion

The minimal intratumoral T cell infiltration and low detection of CD8 transcripts expression in primary GBMs can potentially limit antitumor response. CD4+ and perivascular Foxp3+ TILs associate with tumor angiogenesis and tumor progression in glioma patients. Our results suggest that combining antiangiogenic agents with immunotherapeutic approaches may help improve the antitumor efficacy for patients with malignant gliomas.