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Immunotherapy has enabled remarkable therapeutic responses across cancers of various lineages, albeit with some notable exceptions such as glioblastoma. Several previous misconceptions, which have impaired progress in the past, including the presence and role of the blood-brain barrier and a lack of lymphatic drainage, have been refuted. Nonetheless, a subset of patients with brain metastases but, paradoxically, not the vast majority of those with gliomas are able to respond to immune-checkpoint inhibitors. Immune profiling of samples obtained from patients with central nervous system malignancies using techniques such as mass cytometry and single-cell sequencing along with experimental data from genetically engineered mouse models have revealed fundamental differences in immune composition and immunobiology that not only explain the differences in responsiveness to these agents but also lay the foundations for immunotherapeutic strategies that are applicable to gliomas. Herein, we review the emerging data on the differences in immune cell composition, function and interactions within central nervous system tumours and provide guidance on the development of novel immunotherapies for these historically difficult-to-treat cancers.

As immunotherapy assumes a central role in the management of many cancers, ongoing work is directed at understanding whether immune-based treatments will be successful in patients with glioblastoma (GBM). Despite several large studies conducted in the last several years, there remain no FDA-approved immunotherapies in this patient population. Nevertheless, there are a range of exciting new approaches being applied to GBM, all of which may not only allow us to develop new treatments but also help us understand fundamental features of the immune response in the central nervous system. In this review, we summarize new developments in the application of immune checkpoint blockade, from biomarker-driven patient selection to the timing of treatment. Moreover, we summarize novel work in personalized immune-oncology by reviewing work in cancer immunogenomics–driven neoantigen vaccine studies. Finally, we discuss cell therapy efforts by reviewing the current state of chimeric antigen receptor T-cell therapy.

PURPOSE OF REVIEW In this review, we summarized recent findings that highlight the progress for checkpoint blockade immunotherapy in glioblastoma (GBM) patients. RECENT FINDINGS We reviewed new data from our group and others that suggest that the timing of when immunotherapy is applied can impact the antitumor immune response and, potentially, the ultimate clinical benefit of patients. SUMMARY The neoadjuvant priming and expansion of exhausted T cells within the GBM microenvironment, followed by the removal of an immune suppressive tumor microenvironment through surgical resection, may lead to enhanced antitumor immune responses that are beneficial clinically. As such, neoadjuvant immunotherapeutic approaches and rational combinations may be helpful scientifically to understand how immunotherapeutic interventions influence the tumor microenvironment, as well benefit the patients.

To study the impact of intratumoral VHL heterogeneity observed in patient ccRCC primary tumors, we engineered VHL gene deletion in three RCC models, including a new primary tumor cell line derived from an aggressive metastatic ccRCC. The VHL gene-deleted (VHL-KO) cells underwent epithelial-to-mesenchymal transition (EMT) and showed diminished proliferation and tumorigenicity compared to the parental, VHL-expressing (VHL+) cells. Renal tumors with either VHL+ or VHL-KO cells alone exhibit minimal metastatic potential. Interestingly, tumors with both cells displayed rampant lung metastasis, highlighting a novel cooperative metastatic mechanism. The poorly proliferative VHL-KO cells stimulated the proliferation, EMT and motility of neighboring VHL+ cells. We found that periostin (POSTN), a protein product overexpressed and secreted by VHL- cells, promoted metastasis by enhancing the motility of VHL-WT cells and facilitating vascular escape of tumor cells. Genetic deletion or antibody blockade of POSTN dramatically suppressed lung metastases in our preclinical models. Our work suggests a new strategy to halt progression in ccRCC by disrupting the critical metastatic crosstalk between heterogeneous cell populations within a tumor.

The response of patients with recurrent glioblastoma multiforme to neoadjuvant immune checkpoint blockade has been challenging to interpret due to the inter-patient and intra-tumor heterogeneity. We report on a comparative analysis of tumor tissues collected from patients with recurrent glioblastoma and high-risk melanoma, both treated with neoadjuvant checkpoint blockade. We develop a framework that uses multiplex spatial protein profiling, machine learning-based image analysis, and data-driven computational models to investigate the pathophysiological and molecular factors within the tumor microenvironment that influence treatment response. Using melanoma to guide the interpretation of glioblastoma analyses, we interrogate the protein expression in microscopic compartments of tumors, and determine the correlates of cytotoxic CD8+ T cells, tumor growth, treatment response, and immune cell-cell interaction. This work reveals similarities shared between glioblastoma and melanoma, immunosuppressive factors that are unique to the glioblastoma microenvironment, and potential co-targets for enhancing the efficacy of neoadjuvant immune checkpoint blockade., The response to neoadjuvant immune checkpoint blockade (ICB) in patients with recurrent gliolastoma multiforme (GBM) has been challenging to interpret. Here the authors develop a tumor analysis framework that reveals molecular similarities between GBM and melanoma and unique patterns of immunosuppression in GBM indicating potential co-targets for neoadjuvant ICB.

International audience; In two cohorts of patients with glioblastoma who received anti-PD-1, Sonabend and colleagues show that ERK1/2 phosphorylation, detected by immunohistochemistry, provides a biomarker for MAPK/ERK pathway activity and better survival on this therapy. Only a subset of recurrent glioblastoma (rGBM) responds to anti-PD-1 immunotherapy. Previously, we reported enrichment of BRAF/PTPN11 mutations in 30% of rGBM that responded to PD-1 blockade. Given that BRAF and PTPN11 promote MAPK/ERK signaling, we investigated whether activation of this pathway is associated with response to PD-1 inhibitors in rGBM, including patients that do not harbor BRAF/PTPN11 mutations. Here we show that immunohistochemistry for ERK1/2 phosphorylation (p-ERK), a marker of MAPK/ERK pathway activation, is predictive of overall survival following adjuvant PD-1 blockade in two independent rGBM patient cohorts. Single-cell RNA-sequencing and multiplex immunofluorescence analyses revealed that p-ERK was mainly localized in tumor cells and that high-p-ERK GBMs contained tumor-infiltrating myeloid cells and microglia with elevated expression of MHC class II and associated genes. These findings indicate that ERK1/2 activation in rGBM is predictive of response to PD-1 blockade and is associated with a distinct myeloid cell phenotype.

Cancer immunotherapy has made remarkable advances with over 50 separate Food and Drug Administration (FDA) approvals as first- or second-line indications since 2015. These include immune checkpoint blocking antibodies, chimeric antigen receptor-transduced T cells, and bispecific T-cell–engaging antibodies. While multiple cancer types now benefit from these immunotherapies, notable exceptions thus far include brain tumors, such as glioblastoma. As such, it seems critical to gain a better understanding of unique mechanistic challenges underlying the resistance of malignant gliomas to immunotherapy, as well as to acquire insights into the development of future strategies. An Immuno-Oncology Think Tank Meeting was held during the 2019 Annual Society for Neuro-Oncology Scientific Conference. Discussants in the fields of neuro-oncology, neurosurgery, neuro-imaging, medical oncology, and cancer immunology participated in the meeting. Sessions focused on topics such as the tumor microenvironment, myeloid cells, T-cell dysfunction, cellular engineering, and translational aspects that are critical and unique challenges inherent with primary brain tumors. In this review, we summarize the discussions and the key messages from the meeting, which may potentially serve as a basis for advancing the field of immune neuro-oncology in a collaborative manner.

Despite immune checkpoint inhibitors having success in several other tumor types, many glioblastoma (GBM) patients fail to respond or maintain a sustained response. Work published by our group (Cloughesy et al, 2019) demonstrated that relative to adjuvant programmed cell death-1 (PD-1) blockade, neoadjuvant treatment doubled the median overall survival (OS) for recurrent GBM patients and resulted in an enhanced interferon-γ signature. This suggests that anti-PD-1 given in the neoadjuvant setting may improve outcomes for recurrent GBM patients. The challenge remains in identifying the molecular and genetic signatures associated with response to immune checkpoint blockade. To address this, we analyzed the tumor sample and clinical response data from the patients treated in this clinical trial (n=31). We stratified patients as stable disease (SD) versus progressive disease (PD) based on their response assessment in neuro-oncology criteria (RANO) scores from cycle 2 of treatment post-surgery. Among the SD patients, 77.8% received neoadjuvant treatment while 22.2% received adjuvant therapy. In this group, a median OS was not reached. Among the PD patients, 40.9% received neoadjuvant treatment and 59.1% received adjuvant therapy, with a median OS of 257 days. Next, we analyzed factors that impact response to immunotherapy, which includes somatic mutational burden and interferon-γ pathway induction. We calculated somatic mutational variants, copy number variants (CNVs), and differential gene expression from the bulk tumor exome and RNA-sequencing data. The total mutation counts were similar between groups and no association was identified with increased mutational burden. In addition, total CNV stability was similar between groups. However, when looking at genes involved in the JAK/STAT signaling pathway, there were notably more copy number losses of JAK2 in the PD group when compared to the SD group (85.0% versus 66.7%). These findings merit further exploration as the JAK/STAT pathway has been implicated in response to immune checkpoint blockade.

Despite recent advances with immunotherapy in other tumor types, malignant glioma patients have not shown a therapeutic benefit, potentially due to the insufficient activation of an immune response. We and others have documented immune responses and extended survival following dendritic cell (DC) vaccination in small clinical trials. In this Phase II clinical trial, we randomized malignant glioma patients to receive autologous tumor lysate pulsed DC vaccination with and without adjuvant toll-like receptor (TLR) agonists. Treatment with TLRs in cancer patients has been shown to activate the innate immune response by inducing the expression of pro-inflammatory factors and cytokines. Twenty-three patients with WHO grade III or IV glioma received three intradermal injections of autologous tumor lysate-pulsed DC on days 0, 14, and 28 in conjunction with either a placebo adjuvant, TLR-7 agonist (Resiquimod), or TLR-3 agonist (Poly ICLC). We observed a difference in survival for the DC-vaccinated patients who received adjuvant Poly ICLC treatment of 54 months over adjuvant placebo (20 months) and adjuvant Resiquimod (28 months) groups (P = 0.04). The patient cohorts were balanced for WHO grade, IDH mutation, and MGMT methylation status. Mass cytometry (CyTOF) analysis of patient peripheral blood mononuclear cells (PBMCs) showed increased levels of the monocyte populations CD14+CD16- and CD14dimCD16+ after Poly ICLC treatment. In addition, gene expression analysis of the PBMC populations using single cell RNA sequencing demonstrated increased expression of pro-inflammatory genes after adjuvant Poly ICLC and Resiquimod treatment. Nonetheless, a greater fold change increase and a larger pro-inflammatory repertoire was observed in the Poly ICLC group. Overall, these findings demonstrate that adjuvant Poly ICLC increases the number of circulating monocytes and induces a large pro-inflammatory response, which may account for the survival differences observed over adjuvant Resiquimod and placebo.

Purpose: Wild-type isocitrate dehydrogenase–expressing glioblastoma (GBM) is the most common and aggressive primary brain tumor with a median age at diagnosis of ≥65 years. It accounts for approximately 90% of all GBMs and has a median overall survival (OS) of Experimental Design: (i) Clinical data: GBM patient datasets from The Cancer Genome Atlas, Northwestern Medicine Enterprise Data Warehouse, and clinical studies evaluating ICB were stratified by age and compared for OS. (ii) Animal models: young, middle-aged, and older adult wild-type and indoleamine 2,3 dioxygenase (IDO)-knockout syngeneic mice were intracranially engrafted with CT-2A or GL261 glioma cell lines and treated with or without CTLA-4/PD-L1 mAbs, or radiation, anti–PD-1 mAb, and/or a pharmacologic IDO enzyme inhibitor. Results: Advanced age was associated with decreased GBM patient survival regardless of treatment with ICB. The advanced age–associated increase of brain IDO expression was linked to the suppression of immunotherapeutic efficacy and was not reversed by IDO enzyme inhibitor treatment. Conclusions: Immunosuppression increases in the brain during advanced age and inhibits antiglioma immunity in older adults. Going forward, it will be important to fully understand the factors and mechanisms in the elderly brain that contribute to the decreased survival of older patients with GBM during treatment with ICB.

Purpose: Dendritic cells (DC) initiate adaptive immune responses through the uptake and presentation of antigenic material. In preclinical studies, intratumorally injected activated DCs (aDCs; DCVax-Direct) were superior to immature DCs in rejecting tumors from mice. Experimental Design: This single-arm, open-label phase I clinical trial evaluated the safety and efficacy of aDCs, administered intratumorally, in patients with solid tumors. Three dose levels (2 million, 6 million, and 15 million aDCs per injection) were tested using a standard 3 + 3 dose-escalation trial design. Feasibility, immunogenicity, changes to the tumor microenvironment after direct injection, and survival were evaluated. We also investigated cytokine production of aDCs prior to injection. Results: In total, 39 of the 40 enrolled patients were evaluable. The injections of aDCs were well tolerated with no dose-limiting toxicities. Increased lymphocyte infiltration was observed in 54% of assessed patients. Stable disease (SD; best response) at week 8 was associated with increased overall survival. Increased secretion of interleukin (IL)-8 and IL12p40 by aDCs was significantly associated with survival (P = 0.023 and 0.024, respectively). Increased TNFα levels correlated positively with SD at week 8 (P < 0.01). Conclusions: Intratumoral aDC injections were feasible and safe. Increased production of specific cytokines was correlated with SD and prolonged survival, demonstrating a link between the functional profile of aDCs prior to injection and patient outcomes. Clin Cancer Res; 24(16); 3845–56. ©2018 AACR.

PD-1 checkpoint inhibition has led to remarkable clinical responses in several cancer types. Whereas PD-1 blockade has not shown an overall survival (OS) benefit for glioblastoma (GBM) patients, a subset of them exhibit long-term responses to this immunotherapy. Previously, we reported an enrichment of BRAF/PTPN11 activating mutations in 30% of recurrent GBMs that responded to PD-1 blockade, but the molecular profile of the majority of responders remained elusive. Given that BRAF and PTPN11 promote MAPK/ERK signaling, we investigated whether activation of this pathway is associated with response to PD-1 inhibitors in recurrent GBM, including patients that do not harbor BRAF/PTPN11 mutations. Immunohistochemistry for ERK1/2 phosphorylation (p-ERK), a marker of MAPK/ERK pathway activation, was performed in a discovery cohort including pre-treatment specimens of 29 recurrent GBM patients treated with adjuvant PD-1 blockade, and 33 patients who did not undergo immunotherapy. p-ERK was predictive of response and OS following PD-1 blockade. Yet p-ERK was not associated with OS in patients not treated with immunotherapy. p-ERK was also associated with OS in a validation GBM cohort treated with adjuvant anti-PD-1 therapy. Single-cell RNA-seq and multiplex-immunofluorescence analyses revealed that p-ERK was mainly localized in tumor cells and high p-ERK GBMs contained tumor-infiltrating myeloid cells and microglia with elevated expression of MHC class II and associated genes. Thus, our findings indicate that ERK1/2 activation in recurrent GBM is predictive of response to PD-1 blockade and is associated with a distinct myeloid cell phenotype.

Diffusion magnetic resonance imaging (MRI) estimates of the apparent diffusion coefficient (ADC) has been revealed to be useful for predicting treatment response in patients with glioblastoma (GBM), with an increase in ADC indicating tumor cell death. The aim of the current study was to investigate whether quantitative changes in diffusion MRI after treatment with immune checkpoint inhibitors (ICI) could predict OS in patients with recurrent GBM. A total of 61 patients were included in this retrospective study with the following inclusion criteria: (i) diagnosis of recurrent GBM treated either with pembrolizumab or nivolumab and (ii) availability of diffusion data in pre- and post-ICI MRI. Tumor volume and median relative apparent diffusion coefficient (rADC) within enhancing tumor with respect to normal-appearing white matter were calculated. Median OS for all patients was 7.6 months (range, 1.0–30.6 months). Results showed that higher post-treatment rADC was associated with significantly longer OS (median, 372 days for rADC ≧ 1.42 versus 211 days for rADC < 1.42; P = 0.01, log-rank test), whereas tumor volume and pre-treatment rADC were not significantly associated with OS. Cox regression analysis revealed post-treatment rADC significantly influences OS (P = 0.02, univariate analysis), even after controlling for age, sex, and IDH status (P = 0.007, multivariate analysis), and additionally controlling for whether surgery was performed after ICI treatment (P = 0.049, multivariate analysis). In conclusion, a high post-treatment rADC may be an early imaging biomarker for identifying OS benefit in recurrent GBM patients receiving ICI treatment.

Introduction The immunotherapeutic targeting of New York-esophageal squamous cell carcinoma (NY-ESO-1) and other cancer/testis antigens (CTA) is an appealing strategy for the treatment of malignant gliomas because CTA are not expressed in most normal adult tissues and their expression can be induced in tumors for targeting by T-cells. Basally, NY-ESO-1 is often poorly expressed in glioblastoma (GBM), presumably through promoter methylation. Mechanisms governing the expression of CTA have been explored in other cancers; however, neither the prevalence of NY-ESO-1 downregulation in GBM patient tumors nor the presumed mechanism of downregulation by promoter methylation in GBM has been formally established. Methods We characterized baseline CpG methylation of NY-ESO-1 in 30 bulk patient GBM samples, 10 patient-derived gliomaspheres, and three established tumor cell lines using bisulfite sequencing. We induced NY-ESO-1 expression in vitro in U251 human GBM cells using the hypomethylating agent decitabine (DAC). We investigated the epigenetic response of DAC-treated U251 with bisulfite sequencing and NY-ESO-1 expression with quantitative real-time PCR. Lastly, we performed single-cell RNA sequencing on DAC-treated GBM U251 to evaluate tumor subpopulations that upregulate NY-ESO-1 and other co-expressed CTA after DAC treatment. Results Baseline NY-ESO-1 expression is associated with promoter methylation in the majority of GBM. Treatment of cells with 1 µM DAC every day for 4 days explicitly demethylated the promoter region of NY-ESO-1 and resulted in a 1000-fold increase in mRNA expression. DAC treatment upregulates NY-ESO-1 coordinately with other cancer/testis antigens CTAG2 and MAGEA4 as demonstrated by single-cell RNA sequencing. Conclusion Exposure of U251 to DAC results in promoter demethylation in NY-ESO-1 and increased expression of CTA. DAC treatment may therefore render GBM susceptible to targeting of these antigens by T-cells, revealing a feasible strategy of NY-ESO-1 and co-expressed CTA promoter demethylation to sensitize GBM to immunotherapy.

// Dagmar Quandt 1 , Hans Dieter Zucht 2 , Arno Amann 3 , Anne Wulf-Goldenberg 4 , Carl Borrebaeck 5 , Michael Cannarile 6 , Diether Lambrechts 7 , Herbert Oberacher 8 , James Garrett 9 , Tapan Nayak 10 , Michael Kazinski 11 , Charles Massie 12 , Heidi Schwarzenbach 13 , Michele Maio 14 , Robert Prins 15 , Bjorn Wendik 16 , Richard Hockett 17 , Daniel Enderle 18 , Mikkel Noerholm 18 , Hans Hendriks 19 , Heinz Zwierzina 3 and Barbara Seliger 1 1 Institute of Medical Immunology, Martin Luther University Halle-Wittenberg, Halle, Germany 2 Protagen, Dortmund, Germany 3 Department of Haematology and Oncology, Medical University Innsbruck, Innsbruck, Austria 4 Experimental Pharmacology and Oncology, Berlin-Buch GmbH, Berlin, Germany 5 Create Health Translational Cancer Center, Lund University, Lund, Sweden 6 Roche Pharmaceutical Research and Early Development, Roche Innovation Center, Munich, Germany 7 Laboratory for Translational Genetics, VIB Center for Cancer Biology, Leuven, Belgium 8 Institute of Legal Medicine and Core Facility Metabolomics, Medical University of Innsbruck, Innsbruck, Austria 9 Global Drug Development, Novartis Institutes for BioMedical Research, Cambridge, Massachusetts, USA 10 Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Basel, Switzerland 11 Qiagen, Hilden, Germany 12 CRUK Cambridge Institute, Cambridge, UK 13 University Medical Center Hamburg-Eppendorf, Department of Tumor Biology Hamburg, Hamburg, Germany 14 Medical Oncology and Immunotherapy, University Hospital of Siena, Siena, Italy 15 Department of Neurosurgery, David Geffen School of Medicine at UCLA, Los Angeles, California, USA 16 Perkin Elmer, Hamburg, Germany 17 Biodesix, Boulder, Colorado, USA 18 Exosome Diagnostics GmbH, Martinsried, Germany 19 Hendriks Pharmaceutical Consulting, Purmerend, The Netherlands Correspondence to: Barbara Seliger, email: Barbara.Seliger@uk-halle.de Keywords: liquid biopsy, biomarker, tumor, high throughput analysis, immunotherapy Received: February 08, 2017 Accepted: April 04, 2017 Published: April 24, 2017 ABSTRACT During the last decade, novel immunotherapeutic strategies, in particular antibodies directed against immune checkpoint inhibitors, have revolutionized the treatment of different malignancies leading to an improved survival of patients. Identification of immune-related biomarkers for diagnosis, prognosis, monitoring of immune responses and selection of patients for specific cancer immunotherapies is urgently required and therefore areas of intensive research. Easily accessible samples in particular liquid biopsies (body fluids), such as blood, saliva or urine, are preferred for serial tumor biopsies. Although monitoring of immune and tumor responses prior, during and post immunotherapy has led to significant advances of patients’ outcome, valid and stable prognostic biomarkers are still missing. This might be due to the limited capacity of the technologies employed, reproducibility of results as well as assay stability and validation of results. Therefore solid approaches to assess immune regulation and modulation as well as to follow up the nature of the tumor in liquid biopsies are urgently required to discover valuable and relevant biomarkers including sample preparation, timing of the collection and the type of liquid samples. This article summarizes our knowledge of the well-known liquid material in a new context as liquid biopsy and focuses on collection and assay requirements for the analysis and the technical developments that allow the implementation of different high-throughput assays to detect alterations at the genetic and immunologic level, which could be used for monitoring treatment efficiency, acquired therapy resistance mechanisms and the prognostic value of the liquid biopsies.

Recurrent pediatric high-grade glioma (pHGG) is the leading cause of cancer-related mortality in children. Immunotherapy is a successful treatment approach for a growing number of cancers and is being investigated as a treatment strategy for pHGG. Immunotherapy has shown the most benefit in tumors with increased infiltrating T cells at baseline. Our recently published results revealed that neoadjuvant checkpoint inhibition in recurrent adult glioblastoma was associated with upregulation of a T cell and interferon-γ-related gene expression signature (Tcell-IFNγGES) and was correlated with a significantly extended overall survival (OS). In this study, we examined the immune landscape in recurrent pHGG and the association of Tcell-IFNγGES in the tumor with survival. We analyzed tumor RNAseq data collected at time of recurrence from a historical cohort of 42 pHGG patients from the Children’s Brain Tumor Tissue Consortium. We found a significant transcriptional enrichment of Tcell-IFNγGES in 54% of the tumors. The survival of patients with high Tcell-IFNγGES was observed to be significantly higher than patients with low Tcell-IFNγGES, (log-rank p=0.05). The 3-year OS for patients with low versus high Tcell-IFNγGE was 28.5% (95%, CI:13.7%-59.5%) compared to 50.2% (95%, CI:33.1%-76.1%). When patients were stratified by age, gender and race, low Tcell-IFNγGES was found to be a poor OS prognostic factor (hazard ratio=2.4 (1.14–5.14), p=0.02). This indicates a strong relationship of decreased Tcell-IFNγGES and increased risk of death. Future investigations are necessary to validate these findings, and to explore the value of Tcell-IFNγGES as a predictive biomarker for response to immunotherapy in pHGG.

Brain metastases (BM) commonly arise in patients with melanoma, lung, and breast cancer. Currently, there are limited options for GBM and BM patients who have failed the first-line standard treatment, underscoring the importance of developing new therapeutic strategies. Last year, we and other groups evaluated the neoadjuvant timing of anti-PD-1 checkpoint blockade therapy in recurrent GBM (rGBM) patients, which resulted in a modest survival benefit. In light of the known effectiveness of anti-PD-1 as a systemic therapy to control melanoma and non-small cell lung cancer BM, we set out to study the anti-tumor immune response of BM patients to anti-PD-1 in the neoadjuvant setting. We posited that neoadjuvant anti-PD-1 in patients with BM would result in a stronger antitumoral immune response, which could be quantified at the single cell level. To test this, we made use of contemporary single cell techniques, including multiplex immunofluorescence, time-of-flight mass cytometry (CyTOF) and single-cell RNA sequencing (scRNAseq), to characterize the intratumoral immune cell populations and their transcriptomic profiles. We found that neoadjuvant anti-PD-1 significantly increased the number of tumor infiltrating T lymphocytes in BM compared to rGBM (2.5 fold in BM, p= 0.02 vs. 1.4 fold in rGBM, p= 0.19). Multiplex immunofluorescence analysis of T cells in BM samples revealed a change from T cell exclusion to a diffusely infiltrating phenotype after anti-PD-1 treatment. Importantly, BM showed a higher fraction of effector/cytotoxic T cells compared to rGBM (7.3% vs. 0.9% of lymphoid cells, p= 0.005) and anti-PD-1 further enhanced this population. In the myeloid compartment of BM, neoadjuvant anti-PD-1 increased the frequency of HLA-DR+CD206- M1-like macrophages, implicating a pro-inflammatory microenvironment. In summary, our study delineated the immune cell subtypes altered by neoadjuvant anti-PD-1 and offers insights into new combination therapies that can help understand the clinical efficacy of immunotherapy for BM and GBM patients.

Aberrant alternative splicing (AS) is widespread in cancer, leading to an extensive but largely unexploited repertoire of potential immunotherapy targets. Here we describe IRIS, a computational platform leveraging large-scale cancer and normal transcriptomics data to discover AS-derived tumor antigens for T-cell receptor (TCR) and chimeric antigen receptor T-cell (CAR-T) therapies. Applying IRIS to RNA-Seq data from 22 glioblastomas resected from patients, we identified candidate epitopes and validated their recognition by patient T cells, demonstrating IRIS’s utility for expanding targeted cancer immunotherapy.

INTRODUCTION The lack of immunotherapeutic antigen targets selectively expressed on meningiomas have historically hindered its immunotherapy development. However, recent literature showed that in meningiomas, NY-ESO-1 is the most frequently expressed Cancer-Testis(CT)-antigen, which is a group of proteins silent in somatic cells but reactivated in cancers. NY-ESO-1 also has higher expression in higher-grade meningiomas. Decitabine is known to upregulate CT-antigens and augment immunotherapy. To evaluate systemic adoptive transfer for meningiomas, we tested the efficacy of NY-ESO-1 T-cell-receptor(TCR)-transduced T-cells in vitro and in vivo, and the role of decitabine in meningioma immunotherapy. METHODS NY-ESO-1 TCR-Transduced T-cells were generated by double-transfection with supernatants from PG-13 retroviral packaging cell line encoding HLA-A*0201–restricted NY-ESO-1(157 – 165)-specific TCR. In vitro cytolysis was measured using the xCelligence Real-Time Cell Analyzer System. We utilized human meningioma cells SF1335(Grade I, HLA-A2.1 positive) and CH157(Grade III, HLA-A2.1 negative) in vitro and in vivo. RESULTS CH157 and SF1335 have high and low NY-ESO-1 expression, respectively. Decitabine upregulated NY-ESO-1 mRNA expression in SF1335 by 6-fold after 2 days and by 100-fold after 9 days, with similar effect on protein expression. Co-culturing CH157, CH157-HLA-A2.1(CH157 transduced with HLA-A2.1 vector), SF1335, and decitabine-pretreated-SF1335 cells individually with NY-ESO-1 TCR transduced T-cells at a ratio of 1:1 resulted in 0%, 65%, 20% and 40% cytolysis at 10hours, respectively. Systemic(intravenous) adoptive transfer of TCR-transduced T-cells significantly increased overall survival in NSG mice with intracranial xenografts of CH157-HLA-A2.1 (p=0.04) and SF1335(not treated with decitabine) (p=0.06). CONCLUSIONS NY-ESO-1 TCR-transduced T-cells induce NY-ESO-1 and HLA-A2.1-specific cytolysis in meningioma in vitro, and systemic adoptive transfer confers a statistically significant survival benefit in vivo for meningiomas with high NY-ESO-1 expression. Decitabine upregulates NY-ESO-1 expression and increases tumor cytolysis by TCR-transduced T-cells in meningiomas. Targeting NY-ESO-1 may be a clinically feasible immunotherapeutic strategy to treat aggressive meningiomas.

Glioblastoma is the most common primary malignant brain tumor in adults and is associated with poor survival. The Ivy Foundation Early Phase Clinical Trials Consortium conducted a randomized, multi-institution clinical trial to evaluate immune responses and survival following neoadjuvant and/or adjuvant therapy with pembrolizumab in 35 patients with recurrent, surgically resectable glioblastoma. Patients who were randomized to receive neoadjuvant pembrolizumab, with continued adjuvant therapy following surgery, had significantly extended overall survival compared to patients that were randomized to receive adjuvant, post-surgical programmed cell death protein 1 (PD-1) blockade alone. Neoadjuvant PD-1 blockade was associated with upregulation of T cell- and interferon-γ-related gene expression, but downregulation of cell-cycle-related gene expression within the tumor, which was not seen in patients that received adjuvant therapy alone. Focal induction of programmed death-ligand 1 in the tumor microenvironment, enhanced clonal expansion of T cells, decreased PD-1 expression on peripheral blood T cells and a decreasing monocytic population was observed more frequently in the neoadjuvant group than in patients treated only in the adjuvant setting. These findings suggest that the neoadjuvant administration of PD-1 blockade enhances both the local and systemic antitumor immune response and may represent a more efficacious approach to the treatment of this uniformly lethal brain tumor.

To evaluate the association between a vessel size index (VSIMRI) derived from dynamic susceptibility contrast (DSC) perfusion imaging using a custom spin-and-gradient echo echoplanar imaging (SAGE-EPI) sequence and quantitative estimates of vessel morphometry based on immunohistochemistry from image-guided biopsy samples. The current study evaluated both relative cerebral blood volume (rCBV) and VSIMRI in eleven patients with high-grade glioma (7 WHO grade III and 4 WHO grade IV). Following 26 MRI-guided glioma biopsies in these 11 patients, we evaluated tissue morphometry, including vessel density and average radius, using an automated procedure based on the endothelial cell marker CD31 to highlight tumor vasculature. Measures of rCBV and VSIMRI were then compared to histological measures. We demonstrate good agreement between VSI measured by MRI and histology; VSIMRI = 13.67 μm and VSIHistology = 12.60 μm, with slight overestimation of VSIMRI in grade III patients compared to histology. rCBV showed a moderate but significant correlation with vessel density (r = 0.42, p = 0.03), and a correlation was also observed between VSIMRI and VSIHistology (r = 0.49, p = 0.01). The current study supports the hypothesis that vessel size measures using MRI accurately reflect vessel caliber within high-grade gliomas, while traditional measures of rCBV are correlated with vessel density and not vessel caliber.

Brain-infiltrating lymphocytes (BILs) were isolated from resected brain tissue from 10 pediatric epilepsy patients who had undergone surgery for Hemimegalencephaly (HME) (n = 1), Tuberous sclerosis complex (TSC) (n = 2), Focal cortical dysplasia (FCD) (n = 4), and Rasmussen encephalitis (RE) (n = 3). Peripheral blood mononuclear cells (PBMCs) were also isolated from blood collected at the time of the surgery. Cells were immunostained with a panel of 20 antibody markers, and analyzed by mass cytometry. To identify and quantify the immune cell types in the samples, an unbiased clustering method was applied to the entire data set. More than 85 percent of the CD45+ cells isolated from resected RE brain tissue comprised T cells; by contrast NK cells and myeloid cells constituted 80-95 percent of the CD45+ cells isolated from the TSC and the FCD brain specimens. Three populations of myeloid cells made up >50 percent of all of the myeloid cells in all of the samples of which a population of HLA-DR+ CD11b+ CD4- cells comprised the vast majority of myeloid cells in the BIL fractions from the FCD and TSC cases. CD45RA+ HLA-DR- CD11b+ CD16+ NK cells constituted the major population of NK cells in the blood from all of the cases. This subset also comprised the majority of NK cells in BILs from the resected RE and HME brain tissue, whereas NK cells defined as CD45RA- HLA-DR+ CD11b- CD16- cells comprised 86-96 percent of the NK cells isolated from the FCD and TSC brain tissue. Thirteen different subsets of CD4 and CD8 αβ T cells and γδ T cells accounted for over 80% of the CD3+ T cells in all of the BIL and PBMC samples. At least 90 percent of the T cells in the RE BILs, 80 percent of the T cells in the HME BILs and 40-66 percent in the TSC and FCD BILs comprised activated antigen-experienced (CD45RO+ HLA-DR+ CD69+) T cells. We conclude that even in cases where there is no evidence for an infection or an immune disorder, activated peripheral immune cells may be present in epileptogenic areas of the brain, possibly in response to seizure-driven brain inflammation.

Although immunotherapeutic strategies are emerging as adjunctive treatments for cancer, sensitive methods of monitoring the immune response after treatment remain to be established. We used a novel next-generation sequencing approach to determine whether quantitative assessments of tumor-infiltrating lymphocyte (TIL) content and the degree of overlap of T-cell receptor (TCR) sequences in brain tumors and peripheral blood were predictors of immune response and overall survival in glioblastoma patients treated with autologous tumor lysate–pulsed dendritic cell immunotherapy. A statistically significant correlation was found between a higher estimated TIL content and increased time to progression and overall survival. In addition, we were able to assess the proportion of shared TCR sequences between tumor and peripheral blood at time points before and after therapy, and found the level of TCR overlap to correlate with survival outcomes. Higher degrees of overlap, or the development of an increased overlap following immunotherapy, was correlated with improved clinical outcome, and may provide insights into the successful, antigen-specific immune response. Cancer Immunol Res; 4(5); 412–8. ©2016 AACR.

Malignant glioma, associated with a poor prognosis, is the most common primary malignant brain tumor in adults. We and others have documented immune responses following dendritic cell (DC) vaccination as an active immunotherapeutic treatment for these patients. In this phase II clinical trial, we randomized malignant glioma patients to receive autologous tumor lysate pulsed DC vaccination with and without adjuvant Toll-like receptor (TLR) agonists. TLRs are present on dendritic cells and serve to modulate immune responses. Twenty-three patients with WHO grade III or IV glioma were treated with three intradermal injections of autologous tumor lysate-pulsed DC on days 0, 14, and 28 followed by an adjuvant placebo, TLR-7 agonist (resiquimod), or TLR-3 agonist (Poly ICLC). Mass cytometry (CyTOF) was used to analyze immune cell populations of patient peripheral blood mononuclear cells (PBMC) before and following treatment. DC-vaccinated patients who received adjuvant Poly ICLC treatment had a significantly improved median survival of 54 months over placebo (11 months) and adjuvant resiquimod (17 months) groups (P This abstract is also being presented as Poster B27. Citation Format: Joseph P. Antonios, Richard G. Everson, Aaron Mochizuki, Sara Khattab, Horacio Soto, Prashant Romiyo, Matthew Z. Sun, Diana Moughon, Emma Billingslea-Yoon, Sylvia Odesa, Gang Li, Eric Kawaguchi, Alex Salazar, William Yong, Jason Schlossman, Benjamin Ellingson, Anthony C. Wang, Timothy Cloughesy, Robert M. Prins, Linda M. Liau. Adjuvant TLR-3 administration enhances proinflammatory immune responses and is associated with extended survival in glioblastoma patients treated with dendritic cell vaccination [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr PR13.

Despite advances in the understanding of glioblastoma multiforme (GBM) molecular biology, genomics, and tumor microenvironment, prognosis for patients diagnosed with this disease remains dismal with standard therapies. We and others have shown utility in dendritic cell (DC) vaccination as an active immunotherapeutic treatment for these patients. In this study, we evaluated the use of autologous tumor lysate puled DC vaccine with and without adjuvant toll-like receptor (TLR) agonists. TLRs are present on dendritic cells and serve to modulate immune responses. Twenty-three patients with WHO Grade III or IV glioma were treated with three intradermal injections of autologous tumor lysate-pulsed DC on days 0, 14, and 28 followed by adjuvant placebo treatment, resiquimod (TLR-7 agonist), or poly ICLC (TLR-3 agonist). Gene expression profiling, immunohistochemistry, and mass cytometry (cyTOF) were performed on patient tumors and peripheral blood mononuclear cells. Patients that received adjuvant poly ICLC had a significantly improved median survival of 54 months over placebo (11 months) and adjuvant resiquimod (17 months) groups. Within each treatment cohort, patients with Grade III tumors had increased overall survival over Grade IV tumors. Overall, patients with MGMT methylated tumors on pathology had a median survival of 57 months, while patients with MGMT unmethylated tumors had a median survival of 19 months. Our findings suggest that adjuvant TLR-3 agonist improves outcomes with autologous lysate-pulsed DC vaccine treatment.

BACKGROUND: The use of anti-PD-1 therapy, pembrolizumab, has shown minimal therapeutic effect as an adjuvant treatment in glioblastoma, but its efficacy as a neoadjuvant in recurrent glioblastoma setting has yet to be established. METHODS: The Ivy Foundation Early Phase Clinical Trials’ Consortium conducted a randomized, multi-institution Phase I clinical trial to evaluate the immune response and survival following neoadjuvant and adjuvant therapy with pembrolizumab in thirty patients with recurrent, surgically resectable glioblastoma. Formalin-fixed paraffin embedded tissue was stained using multiplex immunohistochemistry to spatially visualize and quantify the following markers: CD8, PD-1, CD45, GFAP, and PD-L1. RESULTS: The density of tumor infiltrating CD8 T-cells was not statistically different between groups, but distinctly variable in the neoadjuvant treatment group. PD-1 expression across both treatment groups co-localized with CD8 T-cells, though 9 neoadjuvant and only 3 adjuvant samples had appreciable PD-1 detected. Samples with the highest percentage of PD-L1 expression and double positive CD8/PD-1 cell population were present in both groups. Notable CD45/PD-L1 populations were found in 3 neoadjuvant treated samples, with only 1 in the adjuvant group. Samples were classified as having either constitutive, focal, or negative PD-L1 expression pattern with varying degrees of CD8 infiltrate. 7 neoadjuvant patients and 3 adjuvant patients exhibited a focal phenotype with a high CD8 infiltrate. Neoadjuvant samples exhibiting focal PD-L1 expression also had a higher median survival compared to the corresponding adjuvant group (p=0.035, Mantel-Cox log rank). CONCLUSION: Classification of tumors based on PD-L1, CD8, and PD-1 IHC may be predictive of outcome and therapeutic effect. We identified a subset of patients with focal expression of PD-L1 with increased survival. This suggests that focally expressed PD-L1, perhaps induced on tumor and immune infiltrate by the presence of an anti-tumor CD8 response, is a biomarker that is predictive of a positive response to anti-PD-1 checkpoint blockade.

Glioblastoma is the most common malignant brain tumor in adults and is associated with poor survival. It is often resistant to standard-of-care chemotherapy and radiation, necessitating the development of more effective treatments. The Ivy Foundation Early Phase Clinical Trials’ Consortium conducted a randomized, multi-institution clinical trial to evaluate the immune response and survival following neoadjuvant and adjuvant therapy with pembrolizumab, a PD-1 monoclonal antibody, in thirty patients with recurrent, surgically resectable glioblastoma. Patients who received neoadjuvant pembrolizumab, with continued adjuvant therapy following surgery, had significantly extended overall survival compared to patients that received adjuvant, post-surgical PD-1 blockade alone (HR=0.33, p

Background Standard therapy for glioblastoma includes surgery, radiotherapy, and temozolomide. This Phase 3 trial evaluates the addition of an autologous tumor lysate-pulsed dendritic cell vaccine (DCVax®-L) to standard therapy for newly diagnosed glioblastoma. Methods After surgery and chemoradiotherapy, patients were randomized (2:1) to receive temozolomide plus DCVax-L (n = 232) or temozolomide and placebo (n = 99). Following recurrence, all patients were allowed to receive DCVax-L, without unblinding. The primary endpoint was progression free survival (PFS); the secondary endpoint was overall survival (OS). Results For the intent-to-treat (ITT) population (n = 331), median OS (mOS) was 23.1 months from surgery. Because of the cross-over trial design, nearly 90% of the ITT population received DCVax-L. For patients with methylated MGMT (n = 131), mOS was 34.7 months from surgery, with a 3-year survival of 46.4%. As of this analysis, 223 patients are ≥ 30 months past their surgery date; 67 of these (30.0%) have lived ≥ 30 months and have a Kaplan-Meier (KM)-derived mOS of 46.5 months. 182 patients are ≥ 36 months past surgery; 44 of these (24.2%) have lived ≥ 36 months and have a KM-derived mOS of 88.2 months. A population of extended survivors (n = 100) with mOS of 40.5 months, not explained by known prognostic factors, will be analyzed further. Only 2.1% of ITT patients (n = 7) had a grade 3 or 4 adverse event that was deemed at least possibly related to the vaccine. Overall adverse events with DCVax were comparable to standard therapy alone. Conclusions Addition of DCVax-L to standard therapy is feasible and safe in glioblastoma patients, and may extend survival. Trial registration Funded by Northwest Biotherapeutics; Clinicaltrials.gov number: NCT00045968; https://clinicaltrials.gov/ct2/show/NCT00045968?term=NCT00045968&rank=1; initially registered 19 September 2002

Background Standard therapy for glioblastoma includes surgery, radiotherapy, and temozolomide. This Phase 3 trial evaluates the addition of an autologous tumor lysate-pulsed dendritic cell vaccine (DCVax®-L) to standard therapy for newly diagnosed glioblastoma. Methods After surgery and chemoradiotherapy, patients were randomized (2:1) to receive temozolomide plus DCVax-L (n = 232) or temozolomide and placebo (n = 99). Following recurrence, all patients were allowed to receive DCVax-L, without unblinding. The primary endpoint was progression free survival (PFS); the secondary endpoint was overall survival (OS). Results For the intent-to-treat (ITT) population (n = 331), median OS (mOS) was 23.1 months from surgery. Because of the cross-over trial design, nearly 90% of the ITT population received DCVax-L. For patients with methylated MGMT (n = 131), mOS was 34.7 months from surgery, with a 3-year survival of 46.4%. As of this analysis, 223 patients are ≥ 30 months past their surgery date; 67 of these (30.0%) have lived ≥ 30 months and have a Kaplan-Meier (KM)-derived mOS of 46.5 months. 182 patients are ≥ 36 months past surgery; 44 of these (24.2%) have lived ≥ 36 months and have a KM-derived mOS of 88.2 months. A population of extended survivors (n = 100) with mOS of 40.5 months, not explained by known prognostic factors, will be analyzed further. Only 2.1% of ITT patients (n = 7) had a grade 3 or 4 adverse event that was deemed at least possibly related to the vaccine. Overall adverse events with DCVax were comparable to standard therapy alone. Conclusions Addition of DCVax-L to standard therapy is feasible and safe in glioblastoma patients, and may extend survival. Trial registration Funded by Northwest Biotherapeutics; Clinicaltrials.gov number: NCT00045968; https://clinicaltrials.gov/ct2/show/NCT00045968?term=NCT00045968&rank=1; initially registered 19 September 2002

Central nervous system tumors are the leading cause of cancer related death in children. Despite much progress in the field of pediatric neurooncology, modern combination treatment regimens often result in significant late effects, such as neurocognitive deficits, endocrine dysfunction, secondary malignancies, and a host of other chronic health problems. Precision medicine strategies applied to pediatric neurooncology target specific characteristics of individual patients’ tumors to achieve maximal killing of neoplastic cells while minimizing unwanted adverse effects. Here, we review emerging trends and the current literature that have guided the development of new molecularly based classification schemas, promising diagnostic techniques, targeted therapies, and delivery platforms for the treatment of pediatric central nervous system tumors., Graphical Abstract

BACKGROUND Recurrent glioblastoma has a poor median overall survival despite multimodal treatment. The use of pembrolizumab, an anti-PD-1 monoclonal antibody, demonstrates promise, including improved overall survival and increased immune response, when used in the neoadjuvant setting. METHODS We evaluated 13 patients with surgically accessible recurrent glioblastoma who were treated at the University of California, Los Angeles with neoadjuvant checkpoint inhibition prior to tumor resection. Combining data with our previously published multi-center study, we followed this cohort prospectively, performing tumor gene expression to validate the immune response and improved survival following neoadjuvant therapy with pembrolizumab. RESULTS When combined with findings from our prior study, patients in the neoadjuvant group (n = 27) had an overall survival of 400 days, whereas those in the adjuvant-only group (n = 19) had a median overall survival of 228 days by Kaplan-Meier estimator (P = 0.029, log-rank test). Progression-free survival in the neoadjuvant group was 108 days, whereas in the adjuvant-only group it was 72.5 days (P = 0.017, log-rank test). In elastic net penalized Cox proportional hazards regression, neoadjuvant anti-PD-1 blockade continued to be associated with improved overall survival, with a hazard ratio of 0.11 (P=0.003, log-rank test). Bulk tumor gene expression corroborates our previously described pattern of increased T-cell- and IFN-g-related gene expression, decreased cell-cycle-related signatures and their association with clinical response. Additionally, epigenetic regulation inversely correlated with clinical response. CONCLUSIONS Our findings support the neoadjuvant timing of PD-1 blockade in enhancing local immune responses and prolonging overall- and progression-free-survival. Correlative biological studies suggest a potential role for cell-cycle-related gene expression as a biomarker to predict response to therapy. Continued data collection and the addition of patients to the neoadjuvant arm of the trial, will be crucial to determine the potential role of checkpoint inhibition in the treatment of this deadly disease.

© 2017, National Academy of Sciences. All rights reserved. Contrast-enhanced MRI is typically used to follow treatment response and progression in patients with glioblastoma (GBM). However, differentiating tumor progression from pseudoprogression remains a clinical dilemma largely unmitigated by current advances in imaging techniques. Noninvasive imaging techniques capable of distinguishing these two conditions could play an important role in the clinical management of patients with GBM and other brain malignancies. We hypothesized that PET probes for deoxycytidine kinase (dCK) could be used to differentiate immune inflammatory responses from other sources of contrast-enhancement on MRI. Orthotopic malignant gliomas were established in syngeneic immunocompetent mice and then treated with dendritic cell (DC) vaccination and/or PD-1 mAb blockade. Mice were then imaged with [18F]-FAC PET/CT and MRI with i.v. contrast. The ratio of contrast enhancement on MRI to normalized PET probe uptake, which we term the immunotherapeutic response index, delineated specific regions of immune inflammatory activity. On postmortem examination, FACS-based enumeration of intracranial tumor-infiltrating lymphocytes directly correlated with quantitative [18F]-FAC PET probe uptake. Three patients with GBM undergoing treatment with tumor lysate-pulsed DC vaccination and PD-1 mAb blockade were also imaged before and after therapy using MRI and a clinical PET probe for dCK. Unlike in mice, [18F]-FAC is rapidly catabolized in humans; thus, we used another dCK PET probe, [18F]-clofarabine ([18F]-CFA), that may be more clinically relevant. Enhanced [18F]-CFA PET probe accumulation was identified in tumor and secondary lymphoid organs after immunotherapy. Our findings identify a noninvasive modality capable of imaging the host antitumor immune response against intracranial tumors.

Glioblastoma multiforme (GBM) is the most aggressive malignant brain tumor and is associated with an extremely poor clinical prognosis. One pathologic hallmark of GBM is excessive vascularization with abnormal blood vessels. Extensive investigation of anti-angiogenic therapy as a treatment for recurrent GBM has been performed. Bevacizumab, a monoclonal anti-vascular endothelial growth factor A (VEGF-A), suggests a progression-free survival benefit but no overall survival benefit. Developing novel anti-angiogenic therapies are urgently needed in controlling GBM growth. In this study, we demonstrate tumor expression of epithelial membrane protein-2 (EMP2) promotes angiogenesis both in vitro and in vivo using cell lines from human GBM. Mechanistically, this pro-angiogenic effect of EMP2 was partially through upregulating tumor VEGF-A levels. A potential therapeutic effect of a systemic administration of anti-EMP2 IgG1 on intracranial xenografts was observed resulting in both significant reduction of tumor load and decreased tumor vasculature. These results suggest the potential for anti-EMP2 IgG1 as a promising novel anti-angiogenic therapy for GBM. Further investigation is needed to fully understand the molecular mechanisms how EMP2 modulates GBM pathogenesis and progression and to further characterize anti-EMP2 therapy in GBM.

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

Endogenous vaults are ribonucleoproteins expressed throughout various cell types and across numerous species. Several central nervous system (CNS) tumors have been reported to exhibit high levels of major vault protein (MVP). The vault has been hypothesized to play a role in cellular transport. Although further studies are needed to elucidate the mechanisms of endogenous vault function, these advances may enable the development of targeted therapies to prevent cancer cells from acquiring MVP-related drug resistance. In addition, they seem suited for use as nanocapsules for delivering various therapeutic agents and immunogenic proteins, representing a promising prospect for CNS tumor immunotherapy.

Contrast-enhanced MRI is typically used to follow treatment response and progression in glioblastoma (GBM) patients. However, differentiating tumor progression from pseudoprogression remains a clinical dilemma largely unmitigated by advancements in imaging techniques. Non-invasive imaging techniques capable of distinguishing these two conditions could play an important role in the clinical management of patients with GBM and other brain malignancies. We hypothesized that novel PET probes for deoxycytidine kinase (dCK) could be used to differentiate immune inflammatory responses from other sources of contrast-enhancement on MRI. Orthotopic malignant gliomas were established in syngeneic immunocompetent mice, and subsequently treated with dendritic cell (DC) vaccination and/or PD-1 mAb blockade. Mice were then imaged with [18F]d-FAC PET/CT and MRI with intravenous contrast. Pre-contrast T1 was subtracted from T1+C to generate a contrast subtraction map. Co-registration of PET and MRI voxel data further co-localized areas of contrast enhancement with areas of PET-denoted inflammatory response, which was only visualized within the groups that were treated with immunotherapy. The ratio of contrast enhancement on MRI to normalized PET probe uptake, which we termed the Immunotherapeutic Response Index (ITRI), delineated specific regions of immune inflammatory activity. On post-mortem examination, FACS-based enumeration of intracranial tumor-infiltrating lymphocytes directly correlated with quantitative [18F]d-FAC PET probe uptake. Three GBM patients undergoing treatment with tumor lysate-pulsed dendritic cell vaccination and PD-1 mAb blockade were also imaged using MRI and a clinical PET probe for dCK before and after therapy. [18F]-FAC is not clinically relevant due to rapid catabolism in humans, thus enhanced [18F]-Clofarabine ([18F] CFA) PET probe accumulation was identified in tumor and secondary lymphoid organs after immunotherapy. Our findings identify a non-invasive modality capable of imaging the host anti-tumor immune response against intracranial tumors.

INTRODUCTION: PD-1 blockade has demonstrated efficacy in numerous cancer types; however, responses vary widely. Consequently, numerous studies have sought to identify reliable biomarkers that predict response to PD-1 inhibition. Documented responses to PD-1 blockade in GBM are limited to patients with hypermutated phenotypes, which are rare in this disease. METHODS: We opened a multi-institutional pilot study of pembrolizumab in patients with recurrent, surgically resectable GBM, randomizing patients 1:1 to receive neoadjuvant plus adjuvant pembrolizumab or adjuvant-only therapy. We hypothesized that neoadjuvant PD-1 blockade would lead to statistically significant differences in peripheral immune cell populations, using time-of-flight mass cytometry (CyTOF) to achieve our aims. RESULTS: Patients who received neoadjuvant pembrolizumab demonstrated decreases in a CD33(+)CD11b(+)CD11c(+)CD14(+)CD16(+) intermediate monocyte population between baseline and after surgery (adjusted P value = 0.027), whereas no changes were seen in the adjuvant-only group. When evaluating the median expression of markers of antigen experience and activation on various cell populations, we noted increases in CD127 and CTLA4 (P = 0.016 and 0.006, respectively) as well as decreases in PD-1 and CD25 (P = 0.016 and 0.027, respectively) expression on CD4(+) T-cells in the neoadjuvant group before and after the first dose of pembrolizumab, but not the adjuvant-only cohort. On CD8(+) T-cells, there was a significant decrease in PD-1 expression in the neoadjuvant group only (P = 0.004). Furthermore, in penalized regression survival analyses, a CD4(+) T-cell population has emerged as a potential predictor of clinical response. CONCLUSIONS: Leveraging time-of-flight mass cytometry, we have demonstrated that neoadjuvant PD-1 blockade elicits distinct changes in myeloid and lymphoid cell populations in patients with recurrent, surgically resectable glioblastoma. We hypothesize that this is reflective of tumor-specific T-cell activation in the presence of tumor antigens; these T-cells are subsequently expanded and activated in a tumor- and interferon-γ-driven process following surgical resection.

12013Background: Recent data suggested a correlation of active WNT signaling and tumor T cell exclusion. We developed a syngeneic BRAFV600E/PTEN-/-melanoma model YUMM2.1 (Y2.1) that has partial res...

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

Meeting abstracts Glioma tumor lysate-pulsed dendritic cell (DC) vaccination is an effective treatment modality. However, cure rates in the established tumor setting are not therapeutically significant in our preclinical models. We inferred that immunosuppressive antigen presenting cells (iAPCs)

Immunotherapy is a promising area of therapy in patients with neuro-oncological malignancies. However, early-phase studies show unique challenges associated with the assessment of radiological changes in response to immunotherapy reflecting delayed responses or therapy-induced inflammation. Clinical benefit, including long-term survival and tumour regression, can still occur after initial disease progression or after the appearance of new lesions. Refinement of the response assessment criteria for patients with neuro-oncological malignancies undergoing immunotherapy is therefore warranted. Herein, a multinational and multidisciplinary panel of neuro-oncology immunotherapy experts describe immunotherapy Response Assessment for Neuro-Oncology (iRANO) criteria based on guidance for the determination of tumour progression outlined by the immune-related response criteria and the RANO working group. Among patients who demonstrate imaging findings meeting RANO criteria for progressive disease within 6 months of initiating immunotherapy, including the development of new lesions, confirmation of radiographic progression on follow-up imaging is recommended provided that the patient is not significantly worse clinically. The proposed criteria also include guidelines for the use of corticosteroids. We review the role of advanced imaging techniques and the role of measurement of clinical benefit endpoints including neurological and immunological functions. The iRANO guidelines put forth in this Review will evolve successively to improve their usefulness as further experience from immunotherapy trials in neuro-oncology accumulate.

In a Phase 1 dose escalation study we evaluated the safety, feasibility, toxicity, and survival of patients treated with allogeneic cytotoxic T lymphocytes and recombinant IL-2 (alloCTL, rIL-2) infusion administered to the resection cavity of patients with recurrent glioma (WHO grade III or IV). AlloCTL are generated when gamma-irradiated lymphoblasts from the brain tumor patient stimulate the proliferation of peripheral blood mononuclear cells (PBMC) isolated from an HLA-disparate healthy donor in ex vivo culture via one-way mixed lymphocyte reaction. Nine patients were treated on the protocol and received a range of 0.5-5 cycles of therapy. Patients and donors were mismatched at a minimum of 2 HLA A, B, DR loci. Infusates were at least 30% CD3+. Cytotoxicity of alloCTL against patient PBMC ranged from 21.0-84.4% at a 30:1 effector to target ratio. The ratio of CD4/CD8 T cells averaged 1.12 (range 0.14-2.95). In vitro restimulation of alloCTL with patient lymphoblasts allowed for quantitation of immune cell subset proliferation and production of IFN-γ. Adverse events were noted at all three dose levels tested, and were primarily limited to Grade 1-2. Grade 3-4 events were noted only at dose levels 2 and 3. One patient experienced a dose limiting toxicity characterized by Grade 3 fatigue, arthralgia, headache, and non-infectious meningitis. Patient serum samples were collected during the course of therapy to determine Th1/Th2 cytokine profiles using Luminex multiplex analysis. Tumor progression was evident in 8/9 patients resulting in removal from the clinical trial. Median overall survival from the time of inclusion into the study was 8.8 months (range- 3.6-35.7 months). Two patients are still alive at greater than 35.7 and 16.4 months. The results suggest that alloCTL infusion is safe, feasible, and may warrant further study based on the clinical results.

INTRODUCTION: Glioblastoma multiforme (GBM) is a deadly disease with a survival of approximately 15 months. Epithelial membrane protein 2 (EMP2) is correlated with advanced disease and adverse outcomes in several cancers and has recently been found to be expressed on the surface of GBM cells. Its expression in GBM increases integrin surface expression resulting in activation of focal adhesion kinase and Src and promoting increased tumor growth, cell migration, and invasion. METHODS: Subcutaneous and orthotopic mouse models were utilized for this study. In the subcutaneous model, n = 4 BALB/c mice were inoculated with U373 cells and treated with weekly systemic treatments of either anti-EMP2 or control IgG1. Tumor size was measured weekly. In the intracranial model, n = 6 BALB/c nude mice were inoculated with U87 cells overexpressing EMP2 and treated with weekly systemic injections of either anti-EMP2 or control IgG1. Tumor size was followed with bioluminescence imaging. RESULTS: In the subcutaneous model, tumor growth was significantly reduced at 50 days when treated with anti-EMP2 antibody (19 mm3 vs. 45 mm3, p < 0.05), and the residual tumors displayed significant necrosis compared to the control group. In the intracranial model, the treatment group showed a trend toward reduced tumor growth compared to the control group. The mean fold change in average tumor radiance in the treatment group was 402 compared to 543 in the control group. CONCLUSION: Our data present an extremely novel biomarker and therapeutic target for GBM. These findings suggest that targeting EMP2 may be an effective treatment modality for GBM. Further studies are needed to fully elucidate the role of targeting EMP2 in the treatment of GBM.

Immunotherapy represents a promising area of therapy among neuro-oncology patients. However, early phase studies reveal unique challenges associated with assessment of radiological changes reflecting delayed responses or therapy-induced inflammation. Clinical benefit, including long-term survival and tumor regression, can still occur following initial apparent progression or appearance of new lesions. Refinement of response assessment criteria for neuro-oncology patients undergoing immunotherapy is therefore warranted. A multinational and multidisciplinary panel of neuro-oncology immunotherapy experts describes immunotherapy response assessment for neuro-oncology (iRANO) criteria that are based on guidance for determination of tumor progression outlined by the immune-related response criteria (irRC) and the response assessment in neuro-oncology (RANO) working group. Among patients who demonstrate imaging findings meeting RANO criteria for progressive disease (PD) within six months of initiating immunotherapy including the development of new lesions, confirmation of radiographic progression on follow-up imaging is recommended provided that the patient is not significantly worse clinically. The proposed criteria also include guidelines for use of corticosteroids. The role of advanced imaging techniques and measurement of clinical benefit endpoints including neurologic and immunologic functions are reviewed. The iRANO guidelines put forth herein will evolve successively to improve their utility as further experience from immunotherapy trials in neuro-oncology accumulate.

While dendritic cell vaccination is a promising treatment for glioblastoma (GBM), sensitive methods of monitoring the immune response after treatment remain to be established. We sought to determine whether: 1) T cell receptor (TCR) repertoire overlap between peripheral blood and tumor and 2) tumor infiltrating lymphocyte (TIL) content, as assessed by next generation DNA sequencing, are predictors of immune response and survival. Genomic DNA from pre and post treatment tumor, as well as pre and post treatment peripheral blood, of 16 GBM patients enrolled in Phase I and II DC vaccination clinical trials was subjected to next generation sequencing through the TCRVβ region to quantify TIL content and assess the overlap between tumor and blood. Of the 5 patients for whom initial and relapsed tumors were available, two patients with high TCR sequence overlap between tumor and blood prior to treatment demonstrated the longest overall survival (OS) of 71.3 and 28.7 months. Two patients with poor OS (6.3 and 4.5 months) had low blood and tumor TCR overlap both before and after treatment. One multi-focal recurrent patient with intermediate OS (12.6 months) demonstrated an initially low overlap between pre-treatment tumor and blood; however, the TCR overlap increased 200-fold after treatment. Because we did not possess post-treatment, relapsed tumors for many patients, we tested whether the density of pre-treatment TILs was relevant. For the 16 patients from whom we had pre-treatment tumor tissue, the estimated TIL content significantly correlated with time to progression and OS (HR = 0.252, p = 0.0442; HR = 0.277, p = 0.0461), respectively. The estimated TIL content of pre-treatment tumor directly correlates with survival in GBM patients who received autologous tumor lysate-pulsed DC vaccination. Furthermore, the trends of tumor and peripheral blood TCR overlap suggest that this technology can be utilized to track tumor-specific T cell populations without prior knowledge of their antigen specificity.

Immunotherapy represents an appealing option to specifically target CNS tumors using the immune system. In this report, we tested whether adjunctive treatment with the TLR-7 agonist imiquimod could augment antitumor immune responsiveness in CNS tumor-bearing mice treated with human gp100 + tyrosine-related protein-2 melanoma-associated Ag peptide-pulsed dendritic cell (DC) vaccination. Treatment of mice with 5% imiquimod resulted in synergistic reduction in CNS tumor growth compared with melanoma-associated Ag-pulsed DC vaccination alone. Continuous imiquimod administration in CNS tumor-bearing mice, however, was associated with the appearance of robust innate immune cell infiltration and hemorrhage into the brain and the tumor. To understand the immunological mechanisms by which imiquimod augmented antitumor immunity, we tested whether imiquimod treatment enhanced DC function or the priming of tumor-specific CD8+ T cells in vivo. With bioluminescent, in vivo imaging, we determined that imiquimod dramatically enhanced both the persistence and trafficking of DCs into the draining lymph nodes after vaccination. We additionally demonstrated that imiquimod administration significantly increased the accumulation of tumor-specific CD8+ T cells in the spleen and draining lymph nodes after DC vaccination. The results suggest that imiquimod positively influences DC trafficking and the priming of tumor-specific CD8+ T cells. However, inflammatory responses induced in the brain by TLR signaling must also take into account the local microenvironment in the context of antitumor immunity to induce clinical benefit. Nevertheless, immunotherapeutic targeting of malignant CNS tumors may be enhanced by the administration of the innate immune response modifier imiquimod.

OBJECTIVE For many years, the central nervous system (CNS) has been described as "immunologically privileged" and devoid of conventional immune reactivity. However, our more current understanding of neuroimmunology supports a different view. Although immune mechanisms within the CNS may behave differently from those located at peripheral anatomic sites, it is now widely accepted that biologically relevant immune responses can and do occur within the brain and that these responses can play important roles in CNS disease. The objective of this present review is to explore key aspects of recent insights into the cellular interactions involved in neuroimmunology, which may suggest more rational approaches to the immunotherapy of neurosurgical disorders. CONCLUSION Modern advances in molecular medicine and basic immunology have yielded a plethora of new data about CNS immunobiology. The design of effective immunotherapeutic strategies for CNS diseases requires a contemporary understanding of the basic tenets of how the immune system works. The current renaissance in this field may give neurosurgeons hope that, in the future, immunotherapy-based paradigms may be able to successfully treat neurosurgical diseases that are currently refractory to traditional therapies.

Rats bearing a 5-day intracranial (i.c.) syngeneic glioma were treated with a subcutaneous (s.c.) vaccination consisting of irradiated glioma cells or a multimodality approach composed of radiotherapy plus s.c. vaccination. Vaccination of rats harboring a T9 glioma with 5 x 10(6) irradiated T9.F glioma cells (a clone derived from the T9 glioblastoma cell line) resulted in a marked enhancement of i.c. glioma growth and a significant decrease in survival. Histopathology of the tumors from vaccinated rats revealed a massive glioma composed of healthy tumor tissue lacking any marked inflammation, edema or hemorrhage. Analysis of the tumor-infiltrating mononuclear cells indicated that gliomas from vaccinated rats contained a 10-fold greater lymphoid infiltrate per milligram of tumor as compared to tumors from non-vaccinated rats, suggesting that the vaccination had induced immune cells to localize to the i.c. glioma. Combined treatment consisting of 15 Gy of whole head irradiation of the 5-day glioma followed by vaccination with T9.F cells resulted in a significant increase in survival compared to that of non-treated rats, 45% of which remained tumor-free. Microscopic evaluation in survivors of the tumor implantation site revealed the presence of hemosiderin-laden macrophages and other mononuclear cells, with the absence of tumor cells within the residual lesion. When survivors were challenged s.c. with viable T9.F glioma cells, a delayed-type hypersensitivity (DTH) reaction appeared at the challenge site. T cells purified from these rats proliferated and secreted Th(1)-associated cytokines when stimulated with irradiated T9.F glioma cells, and lysed T9.F target cells. In contrast, when these rats were challenged s.c. with the unrelated MadB106 adenocarcinoma, tumor formation was observed. These findings indicate that the treatment of an established i.c. glioma with a cellular vaccination alone may induce enhanced tumor growth; however, when the vaccination is combined with radiation therapy, the results are beneficial in terms of increased survival time or complete remission that is accompanied by the development of tumor-specific cellular immunity.

In a phase 1 trial, a CMV-specific CD8+ T-cell response was induced in a patient with glioblastoma after vaccination with dendritic cells and autologous tumor. CMV in glial cells could serve as an immunotherapeutic target in glioblastoma.