Immune-checkpoint blockade and active immunotherapy for glioma

The potential of mesenchymal stem cell coexpressing cytosine deaminase and secretory IL18-FC chimeric cytokine in suppressing glioblastoma recurrence

Glioblastoma multiforme (GBM) patients have a high recurrence rate of 90%, and the 5-year survival rate is only about 5%. Cytosine deaminase (CDA)/5-fluorocytosine (5-FC) gene therapy is a promising glioma treatment as 5-FC can cross the blood-brain barrier (BBB), while 5-fluorouracil (5-FU) cannot. Furthermore, 5-FU can assist reversing the immunological status of cold solid tumors. This study developed mesenchymal stem cells (MSCs) co-expressing yeast CDA and the secretory IL18-FC superkine to prevent recurrent tumor progression by simultaneously exerting cytotoxic effects and enhancing immune responses. IL18 was fused with Igk and IgG2a FC domains to enhance its secretion and serum half-life. The study confirmed the expression and activity of the CDA enzyme, as well as the expression, secretion, and activity of secretory IL18 and IL18-FC superkine, which were expressed by lentiviruses transduced-MSCs. In the transwell tumor-tropism assay, it was observed that the genetically modified MSCs retained their selective tumor-tropism ability following transduction. CDA-expressing MSCs, in the presence of 5-FC (200 µg/ml), induced cell cycle arrest and apoptosis in glioma cells through bystander effects in an indirect transwell co-culture system. They reduced the viability of the direct co-culture system when they constituted only 12.5 % of the cell population. The effectiveness of engineered MSCs in suppressing tumor progression was assessed by intracerebral administration of a lethal dose of GL261 cells combined in a ratio of 1:1 with MSCs expressing CDA, or CDA and sIL18, or CDA and sIL18-FC, into C57BL/6 mice. PET scan showed no conspicuous tumor mass in the MSC-CDA-sIL18-FC group that received 5-FC treatment. The pathological analysis showed that tumor progression suppressed in this group until 20th day after cell inoculation. Cytokine assessment showed that both interferon-gamma (IFN-γ) and interleukin-4 (IL-4) increased in the serum of MSC-CDA-sIL18 and MSC-CDA-sIL18-FC, treated with normal saline (NS) compared to those of the control group. The MSC-CDA-sIL18-FC group that received 5-FC treatment showed reduced serum levels of IL-6 and a considerably improved survival rate compared to the control group. Therefore, MSCs co-expressing yeast CDA and secretory IL18-FC, with tumor tropism capability, may serve as a supplementary approach to standard GBM treatment to effectively inhibit tumor progression and prevent recurrence.

Individualized Multimodal Immunotherapy for Adults with IDH1 Wild-Type GBM: A Single Institute Experience

Synergistic activity between maintenance temozolomide (TMZm) and individualized multimodal immunotherapy (IMI) during/after first-line treatment has been suggested to improve the overall survival (OS) of adults with IDH1 wild-type MGMT promoter-unmethylated (unmeth) GBM. We expand the data and include the OS of MGMT promoter-methylated (meth) adults with GBM. Unmeth (10 f, 18 m) and meth (12 f, 10 m) patients treated between 27 May 2015 and 1 January 2022 were analyzed retrospectively. There were no differences in age (median: 48 y) or Karnofsky performance index (median: 80). The IMI consisted of 5-day immunogenic cell death (ICD) therapies during TMZm: Newcastle disease virus (NDV) bolus injections and sessions of modulated electrohyperthermia (mEHT); subsequent active specific immunotherapy: dendritic cell (DC) vaccines plus modulatory immunotherapy; and maintenance ICD therapy. There were no differences in the number of vaccines (median: 2), total number of DCs (median: 25.6 × 10⁶), number of NDV injections (median: 31), and number of mEHT sessions (median: 28) between both groups. The median OS of 28 unmeth patients was 22 m (2y-OS: 39%), confirming previous results. OS of 22 meth patients was significantly better (p = 0.0414) with 38 m (2y-OS: 81%). There were no major treatment-related adverse reactions. The addition of IMI during/after standard of care should be prospectively explored.

A 2-Gene Signature Related to Interferon-Gamma Predicts Prognosis and Responsiveness to Immune Checkpoint Blockade of Glioma

Background

Gliomas represent the most common and aggressive brain malignancy. Interferon-gamma (IFNG) is a potent inducer of immune response, developing IFNG-related gene signature may promote the diagnosis and treatment of this disease.

Methods

Bulk tumor and single-cell mRNA-seq datasets of glioma ranging from WHO grade II to IV with corresponding demographics were included. Multiple bioinformatics and machine learning algorithms were performed to develop an IFNG-related prognostic signature and evaluate immune checkpoint blockade (ICB) therapy response.

Results

IFNGR1 and IFNGR2 were used as concise IFNG-related gene signature based on which the IFNGR score well-characterized the IFNG response in the glioma microenvironment. Increased IFNGR score was associated with clinicopathological parameters relating to tumor malignancy and prevailing molecular pathological markers. Notably, K-M and Cox regression analysis found that the IFNGR score was an effective prognostic biomarker, and was associated with tumor relapse for a subset of patients. Notably, IFNGR1 and IFNGR2 were preferentially expressed by the Mono/Macro cells in the glioma microenvironment and were significantly correlated with M2 macrophage. Thus, the IFNGR score-high group had increased expression of immune checkpoints and had the potential to predict ICB responsiveness.

Conclusion

In conclusion, we have developed a concise IFNG-related gene signature of clinical significance, which may improve the current diagnosis and treatment of glioma.

Novel Immune-Related Gene-Based Signature Characterizing an Inflamed Microenvironment Predicts Prognosis and Radiotherapy Efficacy in Glioblastoma

Effective treatment of glioblastoma (GBM) remains an open challenge. Given the critical role of the immune microenvironment in the progression of cancers, we aimed to develop an immune-related gene (IRG) signature for predicting prognosis and improving the current treatment paradigm of GBM. Multi-omics data were collected, and various bioinformatics methods, as well as machine learning algorithms, were employed to construct and validate the IRG-based signature and to explore the characteristics of the immune microenvironment of GBM. A five-gene signature (ARPC1B, FCGR2B, NCF2, PLAUR, and S100A11) was identified based on the expression of IRGs, and an effective prognostic risk model was developed. The IRG-based risk model had superior time-dependent prognostic performance compared to well-studied molecular pathology markers. Besides, we found prominent inflamed features in the microenvironment of the high-risk group, including neutrophil infiltration, immune checkpoint expression, and activation of the adaptive immune response, which may be associated with increased hypoxia, epidermal growth factor receptor (EGFR) wild type, and necrosis. Notably, the IRG-based risk model had the potential to predict the effectiveness of radiotherapy. Together, our study offers insights into the immune microenvironment of GBM and provides useful information for clinical management of this desperate disease.

An evidence mapping and scientometric analysis of the top-100 most cited clinical trials of anti-PD-1/PD-L1 drugs to treat cancers

OBJECTIVE

To gain a deeper understanding of the hot topics and future prospects of programmed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1) inhibitors treatment of cancer through scientometric analysis of the top-100 most cited clinical trials.

MATERIALS AND METHODS

We searched the Web of Science Core Collection database from 1980 to June 2019. Two reviewers independently screened the top-100 most cited clinical trials that defined by the National Institutes of Health starting from the most cited article. Title, year of publication, citations, type of cancer, and focused aspects of outcomes were extracted from included clinical trials. VOSviewer software (version 1.6.9) and Excel 2016 were used to do statistical analysis. The evidence mapping was used to present the relationship between cancers, drugs, citations, and outcomes, etc. RESULTS: The top-100 most cited clinical trials published from 2010 to 2018 in nine journals with high impact factor (IF) (IF₂₀₁₈:6.68-70.67), and Lancet Oncology (USA) published the most clinical trials (n = 29, IF₂₀₁₈ = 35.3856). The total number of citations of the top-100 most cited clinical trials was from 59 to 5606. 920 authors from 34 countries and 458 organizations participated in publishing the top-100 most cited clinical trials. The USA (n = 95) and Memorial Sloan-Kettering Cancer Center (n = 31) contributed the most publications. Based on the evidence mapping, there are 25 different types of cancers (e.g. lung cancer, melanoma, and renal cell cancer) and five focused aspects of outcomes (e.g. safety and efficacy).

CONCLUSION

The USA was the dominant country. Anti-PD-1/PD-L1 drugs were widely used to treat lung cancer, melanoma, renal cell cancer, and Hodgkin lymphoma. More exploration should be done to explore the use of anti-PD-1/PD-L1 drugs to treat more type of cancers in future research.

Construction of Interferon-Gamma-Related Gene Signature to Characterize the Immune-Inflamed Phenotype of Glioblastoma and Predict Prognosis, Efficacy of Immunotherapy and Radiotherapy

Interferon-gamma (IFNG) has profound impacts on tumor-immune interaction and is of great clinical significance for multiple cancers. Exploring the role of IFNG in glioblastoma (GBM) may optimize the current treatment paradigm of this disease. Here, multi-dimensional data of 429 GBM samples were collected. Various bioinformatics algorithms were employed to establish a gene signature that characterizes immunological features, genomic alterations, and clinical characteristics associated with the IFNG response. In this way, a novel IFNG-related gene signature (IFNGrGS, including TGFBI, IL4I1, ACP5, and LUM) has been constructed and validated. Samples with increased IFNGrGS scores were characterized by increased neutrophil and macrophage infiltration and exuberant innate immune responses, while the activated adaptive immune response may be frustrated by multiple immunosuppressive mechanisms. Notably, the IFNG pathway as well as its antagonistic pathways including IL4, IL10, TGF-beta, and VEGF converged on the expression of immune checkpoints. Besides, gene mutations involved in the microenvironment were associated with the IFNGrGS-based stratification, where the heterogeneous prognostic significance of EGFR mutation may be related to the different degrees of IFNG response. Moreover, the IFNGrGS score had solid prognostic value and the potential to screen ICB and radiotherapy sensitive populations. Collectively, our study provided insights into the role of IFNG on the GBM immune microenvironment and offered feasible information for optimizing the treatment of GBM.

The Current State of Potential Therapeutic Modalities for Glioblastoma Multiforme: A Clinical Review

Glioblastoma multiforme (GBM), as the most lethal brain tumor, continues to be incurable. Considering the high mortality rate of GBM, it is crucial to develop new treatment approaches. Conventional therapies, including maximal surgical resection, radiation therapy, and chemotherapy (typically temozolomide), have not led to significant changes in the survival rates of GBM patients. However, emerging modalities, such as the use of tyrosine kinase inhibitors, mTOR inhibitors, NF-κB modulators, nitrosoureas, and immunotherapeutic agents have shown promising in improving GBM outcomes. In this context, we reviewed the current status of GBM treatment, the efficacy of existing standard therapies in improving disease outcomes, and future therapeutic directions.

Challenges and potential of PD-1/PD-L1 checkpoint blockade immunotherapy for glioblastoma

PD-1/PD-L1 checkpoint blockades have achieved significant progress in several kinds of tumours. Pembrolizumab, which targets PD-1, has been approved as a first-line treatment for advanced non-small cell lung cancer (NSCLC) patients with positive PD-L1 expression. However, PD-1/PD-L1 checkpoint blockades have not achieved breakthroughs in treating glioblastoma because glioblastoma has a low immunogenic response and an immunosuppressive microenvironment caused by the precise crosstalk between cytokines and immune cells. A phase III clinical trial, Checkmate 143, reported that nivolumab, which targets PD-1, did not demonstrate survival benefits compared with bavacizumab in recurrent glioblastoma patients. Thus, the combination of a PD-1/PD-L1 checkpoint blockade with RT, TMZ, antibodies targeting other inhibitory or stimulatory molecules, targeted therapy, and vaccines may be an appealing solution aimed at achieving optimal clinical benefit. There are many ongoing clinical trials exploring the efficacy of various approaches based on PD-1/PD-L1 checkpoint blockades in primary or recurrent glioblastoma patients. Many challenges need to be overcome, including the identification of discrepancies between different genomic subtypes in their response to PD-1/PD-L1 checkpoint blockades, the selection of PD-1/PD-L1 checkpoint blockades for primary versus recurrent glioblastoma, and the identification of the optimal combination and sequence of combination therapy. In this review, we describe the immunosuppressive molecular characteristics of the tumour microenvironment (TME), candidate biomarkers of PD-1/PD-L1 checkpoint blockades, ongoing clinical trials and challenges of PD-1/PD-L1 checkpoint blockades in glioblastoma.

The Prognostic and Therapeutic Value of PD-L1 in Glioma

Glioma is the most common type of primary brain tumors. After standard treatment regimen (surgical section, radiotherapy and chemotherapy), the average survival time remains merely around 14 months for glioblastoma (grade IV glioma). Recent immune therapy targeting to the immune inhibitory checkpoint axis, i.e., programmed cell death protein 1 (PD-1) and its ligand PD-L1 (i.e., CD274 or B7-H1), has achieved breakthrough in many cancers but still not in glioma. PD-L1 is considered a major prognostic biomarker for immune therapy in many cancers, with anti-PD-1 or anti-PD-L1 antibodies being used. However, the expression and subcellular distribution of PD-L1 in glioma cells exhibits great variance in different studies, severely impairing PD-L1's value as therapeutic and prognostic biomarker in glioma. The role of PD-L1 in modulating immune therapy is complicated. In addition, endogenous PD-L1 plays tumorigenic roles in glioma development. In this review, we summarize PD-L1 mRNA expression and protein levels detected by using different methods and antibodies in human glioma tissues in all literatures, and we evaluate the prognostic value of PD-L1 in glioma. We also summarize the relationships between PD-L1 and immune cell infiltration in glioma. The mechanisms regulating PD-L1 expression and the oncogenic roles of endogenous PD-L1 are discussed. Further, the therapeutic results of using anti-PD-1/PD-L1 antibodies or PD-L1 knockdown are summarized and evaluated. In summary, current results support that PD-L1 is not only a prognostic biomarker of immune therapy, but also a potential therapeutic target for glioma.

Immunotherapy of Primary Brain Tumors: Facts and Hopes

The field of cancer immunotherapy has made exciting progress for some cancer types in recent years. However, recent failures of late-phase clinical trials evaluating checkpoint blockade in patients with glioblastoma (GBM) represent continued challenges for brain cancer immunotherapy. This is likely due to multiple factors including but not limited to marked genetic and antigenic heterogeneity, relatively low mutational loads, and paucity of GBM-infiltrating T cells. We review recent and ongoing studies targeting the checkpoint molecules as monotherapy or in combination with other modalities, and discuss the mechanisms underlying the unresponsiveness of GBM to single-modality immunotherapy approaches. We also discuss other novel immunotherapy approaches that may promote T-cell responses and overcome the "cold tumor" status of GBM, including oncolytic viruses and adoptive T-cell therapy. Clin Cancer Res; 24(21); 5198-205. ©2018 AACR.

Receptor-Targeted Glial Brain Tumor Therapies

Among primary brain tumors, malignant gliomas are notably difficult to manage. The higher-grade tumors represent an unmet need in medicine. There have been extensive efforts to implement receptor-targeted therapeutic approaches directed against gliomas. These approaches include immunotherapies, such as vaccines, adoptive immunotherapy, and passive immunotherapy. Targeted cytotoxic radio energy and pro-drug activation have been designed specifically for brain tumors. The field of targeting through receptors progressed significantly with the discovery of an interleukin 13 receptor alpha 2 (IL-13RA2) as a tumor-associated receptor over-expressed in most patients with glioblastoma (GBM) but not in normal brain. IL-13RA2 has been exploited in novel experimental therapies with very encouraging clinical responses. Other receptors are specifically over-expressed in many patients with GBM, such as EphA2 and EphA3 receptors, among others. These findings are important in view of the heterogeneity of GBM tumors and multiple tumor compartments responsible for tumor progression and resistance to therapies. The combined targeting of multiple receptors in different tumor compartments should be a preferred way to design novel receptor-targeted therapeutic approaches in gliomas.

Predictors of Response to Autologous Dendritic Cell Therapy in Glioblastoma Multiforme

Background

Glioblastoma (GBM) is the most common and lethal primary malignant glioma in adults. Dendritic cell (DC) vaccines have demonstrated promising results in GBM clinical trials. However, some patients do not respond well to DC therapy, with survival rates similar to those of conventional therapy. We retrospectively analyzed clinical and laboratory data to evaluate the factors affecting vaccine treatment.

Methods

Forty-seven patients with de novo GBM were enrolled at China Medical University Hospital between 2005 and 2010 and divided into two subgroups. One subgroup of 27 patients received postsurgical adjuvant immunotherapy with autologous dendritic cell/tumor antigen vaccine (ADCTA) in conjunction with conventional treatment of concomitant chemoradiotherapy (CCRT) with temozolomide. The other 20 patients received only postsurgical conventional treatment without immunotherapy. Immunohistochemistry for CD45, CD4, CD8, programed death ligand 1 (PD-L1), and programed death 1 (PD-1) was performed on sections of surgical tumor specimens and peripheral blood mononuclear cells (PBMCs). Pearson's correlation, Cox proportional hazard model, and Kaplan-Meier analyses were performed to examine the correlations between the prognostic factors and survival rates.

Results

Younger age (<57 years), gross total resection, and CCRT and PD-1⁺ lymphocyte counts were significant prognostic factors of overall survival (OS) and progression-free survival (PFS) in the ADCTA group. Sex, CD45⁺ lymphocyte count, CD4⁺ or CD8⁺ lymphocyte count, tumor PD-L1 expression, isocitrate dehydrogenase 1 mutation, and O6 methylguanine-DNA methyltransferase promoter methylation status were not significant factors in both groups. In the ADCTA group, patients with tumor-infiltrating lymphocytes (TILs) with a lower PD-1⁺/CD8⁺ ratio (≤0.21) had longer OS and PFS (median OS 60.97 months, P < 0.001 and PFS 11.2 months, P < 0.008) compared to those with higher PD-1⁺/CD8⁺ ratio (>0.21) (median OS 20.07 months, P < 0.001 and PFS 4.43 months, P < 0.008). Similar results were observed in patients' PBMCs; lymphocyte counts with lower PD-1⁺/CD8⁺ ratio (≤0.197) had longer OS and PFS. There was a significant correlation of PD-1⁺/CD8⁺ ratio between TILs and PBMCs (Pearson's correlation R² = 0.6002, P < 0.001). By contrast, CD4^-, CD8^-, but PD-1⁺, CD45⁺ tumor-infiltrating lymphocytes have no impact on OS and PFS (P = 0.073 and P = 0.249, respectively).

Conclusion

For patients receiving DC vaccine adjuvant therapy, better outcomes are predicted in patients with younger age, with TILs or PBMCs with lower PD-1⁺/CD8⁺ ratio, with gross tumor resection, and receiving CCRT.

A radiosensitivity gene signature and PD-L1 predict the clinical outcomes of patients with lower grade glioma in TCGA

PURPOSE

Identifying predictive factors for the clinical outcome of patients with lower grade gliomas following radiotherapy could help optimize patient treatments. Here, we investigate the predictive efficacy of both a previously identified "31-gene signature" and programmed death ligand-1 (PD-L1) expression.

MATERIAL AND METHODS

We identified 511 patients with lower grade glioma (Grade 2 and 3) in The Cancer Genome Atlas dataset and divided them into two clusters: radiosensitive (RS) and radioresistant (RR). Patients were also classified as PD-L1-high or PD-L1-low based on CD274 mRNA expression. Five-year survival rates were compared across patient groups, and differentially expressed genes were identified via a gene enrichment analysis.

RESULTS

Among 511 patients with lower grade glioma in The Cancer Genome Atlas dataset, we identified a group that was characterized by radioresistant and high PD-L1 (the PD-L1-high-RR group). Multivariate Cox models demonstrated that the membership in the PD-L1-high-RR can predict overall survival regarding to RT. Differentially expressed genes associated with the PD-L1-high-RR group were found to play a role in the immune response, including the T-cell receptor signaling pathway.

CONCLUSION

We tested the predictive value of a "31-gene signature" and PD-L1 expression status in a dataset of patients with lower grade glioma. Our results suggest that the patient population classified as the PD-L1-high-RR may benefit most from radiotherapy combined with anti-PD-1/PD-L1 treatment. Prospective clinical trial is necessary to validate the findings in a homogenous treated patient cohort.

Case report: pembrolizumab-induced Type 1 diabetes in a patient with metastatic cholangiocarcinoma

BACKGROUND

Immune checkpoint inhibitors are novel cancer therapies associated with numerous autoimmune toxicities, some of which are only now being appreciated.

CASE PRESENTATION

A 67-year old female with metastatic cholangiocarcinoma and no prior history of diabetes was treated with leucovorin, fluorouracil, oxaliplatin and pembrolizumab. After eight cycles, she developed new onset type 1 diabetes mellitus with positive glutamic acid decarboxylase antibody titers. Conclusions: To our knowledge, this is the first reported case of PD-1 inhibitor associated Type 1 diabetes mellitus in a patient with cholangiocarcinoma and supports others' experiences that PD-1 inhibition can cause a spectrum of autoimmune adverse events that require clinical monitoring and periodic screenings.

Abnormal expression of circulating and tumor-infiltrating carcinoembryonic antigen-related cell adhesion molecule 1 in patients with glioma

Glioma, the most prevalent primary tumor of the central nervous system, is known to evade immune surveillance and escape immune attacks by inducing immunosuppression. The homophilic interactions of the carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) serve a critical function in immunoregulation. In the present study, the expression levels of CEACAM1 in peripheral blood mononuclear cells and tumor-infiltrating lymphocytes (TILs) from patients with gliomas were assessed. Furthermore, associations between CEACAM1 expression and multiple clinicopathological characteristics in patients with gliomas were analyzed. The results of the present study suggested that the expression of CEACAM1 in circulating T cells was markedly increased in patients with gliomas compared with control subjects, and was further increased in TILs. Patients with high-grade gliomas [World Health Organization (WHO) grade III–IV] demonstrated a significantly increased expression of CEACAM1 on T cells compared with those with low-grade gliomas (WHO grade I–II). Furthermore, the expression of CEACAM1 on T cells was negatively correlated with the Karnofsky score and the plasma level of interferon-γ in patients with gliomas. Immunohistochemical analysis revealed that the expression levels of CEACAM1 in high-grade glioma tissues (WHO grade III–IV) were increased compared with the expression levels in the controls, and were associated with the expression of CEACAM1 in TILs. In summary, the results of the present study indicate that homophilic interactions of CEACAM1 may participate in the progression and development of gliomas through their negative regulatory effects on T cells. Thus, CEACAM1 may be a promising candidate for targeted glioma immunotherapy.

Glioblastoma update: molecular biology, diagnosis, treatment, response assessment, and translational clinical trials

This is an exciting time in neuro-oncology. Discoveries elucidating the molecular mechanisms of oncogenesis and the molecular subtypes of glioblastoma multiforme (GBM) have led to new diagnostic and classification schemes with more prognostic power than histology alone. Molecular profiling has become part of the standard neuropathological evaluation of GBM. Chemoradiation followed by adjuvant temozolomide remains the standard therapy for newly diagnosed GBM, but survival remains unsatisfactory. Patients with recurrent GBM continue to have a dismal prognosis, but neuro-oncology centers with active clinical trial programs are seeing a small but increasing cadre of patients with longer survival. Molecularly targeted therapeutics, personalized therapy based on molecular profiling of individual tumors, and immunotherapeutic strategies are all being evaluated and refined in clinical trials. Understanding of the molecular mechanisms of tumor-mediated immunosuppression, and specifically interactions between tumor cells and immune effector cells in the tumor microenvironment, has led to a new generation of immunotherapies, including vaccine and immunomodulatory strategies as well as T-cell-based treatments. Molecularly targeted therapies, chemoradiation, immunotherapies, and anti-angiogenic therapies have created the need to develop more reliable neuroimaging criteria for differentiating the effects of therapy from tumor progression and changes in blood–brain barrier physiology from treatment response. Translational clinical trials for patients with GBM now incorporate quantitative imaging using both magnetic resonance imaging and positron emission tomography techniques. This update presents a summary of the current standards for therapy for newly diagnosed and recurrent GBM and highlights promising translational research.

Recognition by natural killer cells of N6-isopentenyladenosine-treated human glioma cell lines

Cancer cell stress induced by cytotoxic agents promotes antitumor immune response. Here, we observed that N6-isopentenyladenosine (iPA), an isoprenoid modified adenosine with a well established anticancer activity, was able to induce a significant upregulation of cell surface expression of natural killer (NK) cell activating receptor NK Group 2 member D (NKG2D) ligands on glioma cells in vitro and xenografted in vivo. Specifically suboptimal doses of iPA (0.1 and 1 µM) control the selective upregulation of UL16-binding protein 2 on p53wt-expressing U343MG and that of MICA/B on p53mut-expressing U251MG cells. This event made the glioblastoma cells a potent target for NK cell-mediated recognition through a NKG2D restricted mechanism. p53 siRNA-mediated knock-down and pharmacological inhibition (pifithrin-α), profoundly prevented the iPA action in restoring the immunogenicity of U343MG cells through a mechanism that is dependent upon p53 status of malignancy. Furthermore, accordingly to the preferential recognition of senescent cells by NK cells, we found that iPA treatment was critical for glioma cells entry in premature senescence through the induction of S and G2/M phase arrest. Collectively, our results indicate that behind the well established cytotoxic and antiangiogenic effects, iPA can also display an immune-mediated antitumor activity. The indirect engagement of the innate immune system and its additional activity in primary derived patient's glioma cell model (GBM17 and GBM37), fully increase its translational relevance and led to the exploitation of the isoprenoid pathway for a valid therapeutic intervention in antiglioma research.

Modulating glioma-mediated myeloid-derived suppressor cell development with sulforaphane

Glioblastoma is the most common primary tumor of the brain and has few long-term survivors. The local and systemic immunosuppressive environment created by glioblastoma allows it to evade immunosurveillance. Myeloid-derived suppressor cells (MDSCs) are a critical component of this immunosuppression. Understanding mechanisms of MDSC formation and function are key to developing effective immunotherapies. In this study, we developed a novel model to reliably generate human MDSCs from healthy-donor CD14+ monocytes by culture in human glioma-conditioned media. Monocytic MDSC frequency was assessed by flow cytometry and confocal microscopy. The resulting MDSCs robustly inhibited T cell proliferation. A cytokine array identified multiple components of the GCM potentially contributing to MDSC generation, including Monocyte Chemoattractive Protein-1, interleukin-6, interleukin-8, and Macrophage Migration Inhibitory Factor (MIF). Of these, Macrophage Migration Inhibitory Factor is a particularly attractive therapeutic target as sulforaphane, a naturally occurring MIF inhibitor derived from broccoli sprouts, has excellent oral bioavailability. Sulforaphane inhibits the transformation of normal monocytes to MDSCs by glioma-conditioned media in vitro at pharmacologically relevant concentrations that are non-toxic to normal leukocytes. This is associated with a corresponding increase in mature dendritic cells. Interestingly, sulforaphane treatment had similar pro-inflammatory effects on normal monocytes in fresh media but specifically increased immature dendritic cells. Thus, we have used a simple in vitro model system to identify a novel contributor to glioblastoma immunosuppression for which a natural inhibitor exists that increases mature dendritic cell development at the expense of myeloid-derived suppressor cells when normal monocytes are exposed to glioma conditioned media.

Isocitrate dehydrogenase mutations suppress STAT1 and CD8+ T cell accumulation in gliomas

Mutations in the isocitrate dehydrogenase genes IDH1 and IDH2 are among the first genetic alterations observed during the development of lower-grade glioma (LGG). LGG-associated IDH mutations confer gain-of-function activity by converting α-ketoglutarate to the oncometabolite R-2-hydroxyglutarate (2HG). Clinical samples and gene expression data from The Cancer Genome Atlas (TCGA) demonstrate reduced expression of cytotoxic T lymphocyte-associated genes and IFN-γ-inducible chemokines, including CXCL10, in IDH-mutated (IDH-MUT) tumors compared with IDH-WT tumors. Given these findings, we have investigated the impact of IDH mutations on the immunological milieu in LGG. In immortalized normal human astrocytes (NHAs) and syngeneic mouse glioma models, the introduction of mutant IDH1 or treatment with 2HG reduced levels of CXCL10, which was associated with decreased production of STAT1, a regulator of CXCL10. Expression of mutant IDH1 also suppressed the accumulation of T cells in tumor sites. Reductions in CXCL10 and T cell accumulation were reversed by IDH-C35, a specific inhibitor of mutant IDH1. Furthermore, IDH-C35 enhanced the efficacy of vaccine immunotherapy in mice bearing IDH-MUT gliomas. Our findings demonstrate a mechanism of immune evasion in IDH-MUT gliomas and suggest that specific inhibitors of mutant IDH may improve the efficacy of immunotherapy in patients with IDH-MUT gliomas.

Expression of programmed cell death-ligand 1 and its correlation with clinical outcomes in gliomas

Programmed cell death-ligand 1(PD-L1) was expressed in various malignancies, and interaction with its receptor programmed cell death 1 (PD-1) often contributed to immune evasion of tumor cells. In this study, we explored the expression of PD-L1 and its correlation with clinical outcomes in gliomas.

Clinicopathological data of 229 patients with gliomas was collected. PD-L1 expression was assessed by tissue-microarray-based immunohistochemistry. Over 5% of tumor cells with cytoplasm or membrane staining was defined as PD-L1 positive expression. The associations of clinicopathological features with overall survival (OS) and disease-free survival (DFS) were analyzed by univariate analysis and multivariate analysis was further performed by Cox regression model.

PD-L1 positive expression was observed in 51.1% gliomas patients and no significant association was verified between PD-L1 expression and pathological grade in 229 gliomas patients. However, PD-L1 expression rate was 49.2%, 53.7% and 68.8% for grade II, III and IV in 161 patients with those ≥ 12 months of OS, respectively. Although no significant discrepancies was displayed, there was a certain degree of differences between PD-L1 expression and pathological grade (49.2% vs. 53.7% vs. 68.8%, P = 0.327). Univariate analysis showed that PD-L1 expression was significantly associated with poor OS in the patients with long-time survival or follow up (OS ≥ 12 months) (P = 0.018), especially in patients with grade IV (P = 0.019). Multivariate analysis revealed that a strong tendency towards statistical significance was found between PD-L1 expression and poor OS (P = 0.081).

In gliomas patients with long-time survival or follow up, PD-L1 positive expression could indicate the poor prognosis and it is possible that immunotherapy targeting PD-L1 pathway needed to be determined in the further study.

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

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

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

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

Immunotherapy for glioma: from illusion to realistic prospects?

There is now evidence that the rules established for tumor immunology and immunotherapy in general are relevant for brain tumors. Treatment strategies explored have mainly involved vaccines using either tumor cells or components, and vaccines with defined synthetic peptides. This latter approach offers the advantage to select well-characterized antigens with selective or preferential expression on glioma. This is a prerequisite because collateral damage to the brain is not allowed. A second strategy which is reaching clinical trials is T cell therapy using the patients' own lymphocytes engineered to become tumor reactive. Tumor specificity can be conferred by forced expression of either a high-avidity T cell receptor or an antitumor antibody (the latter cells are called chimeric antigen receptors). An advantage of T cell engineering is the possibility to modify the cells to augment cellular activation, in vivo persistence and resistance to the tumor immunosuppressive milieu. A direct targeting of the hostile glioma microenvironment will additionally be required for achieving potent immunotherapy and various trials are assessing this issue. Finally, combining immunotherapy with immune checkpoint inhibitors and chemotherapy must be explored within rigorous clinical trials that favor constant interactions between the bench and bedside. Regarding immunotherapy for glioma patients, what was an unrealistic dream a decade ago is today a credible prospect.

Irradiation of necrotic cancer cells, employed for pulsing dendritic cells (DCs), potentiates DC vaccine-induced antitumor immunity against high-grade glioma

Dendritic cell (DC)-based immunotherapy has yielded promising results against high-grade glioma (HGG). However, the efficacy of DC vaccines is abated by HGG-induced immunosuppression and lack of attention toward the immunogenicity of the tumor lysate/cells used for pulsing DCs. A literature analysis of DC vaccination clinical trials in HGG patients delineated the following two most predominantly applied methods for tumor lysate preparation: freeze-thaw (FT)-induced necrosis or FT-necrosis followed by X-ray irradiation. However, from the available clinical evidence, it is unclear which of both methodologies has superior immunogenic potential. Using an orthotopic HGG murine model (GL261-C57BL/6), we observed that prophylactic vaccination with DCs pulsed with irradiated FT-necrotic cells (compared to FT-necrotic cells only) prolonged overall survival by increasing tumor rejection in glioma-challenged mice. This was associated, both in prophylactic and curative vaccination setups, with an increase in brain-infiltrating Th1 cells and cytotoxic T lymphocytes (CTL), paralleled by a reduced accumulation of regulatory T cells, tumor-associated macrophages (TAM) and myeloid-derived suppressor cells (MDSC). Further analysis showed that irradiation treatment of FT-necrotic cells considerably increased the levels of carbonylated proteins — a surrogate-marker of oxidation-associated molecular patterns (OAMPs). Through further application of antioxidants and hydrogen peroxide, we found a striking correlation between the amount of lysate-associated protein carbonylation/OAMPs and DC vaccine-mediated tumor rejection capacity thereby suggesting for the first time a role for protein carbonylation/OAMPs in at least partially mediating antitumor immunity. Together, these data strongly advocate the use of protein oxidation-inducing modalities like irradiation for increasing the immunogenicity of tumor lysate/cells used for pulsing DC vaccines.

Ex vivo generation of dendritic cells from cryopreserved, post-induction chemotherapy, mobilized leukapheresis from pediatric patients with medulloblastoma

Generation of patient-derived, autologous dendritic cells (DCs) is a critical component of cancer immunotherapy with ex vivo-generated, tumor antigen-loaded DCs. An important factor in the ability to generate DCs is the potential impact of prior therapies on DC phenotype and function. We investigated the ability to generate DCs using cells harvested from pediatric patients with medulloblastoma for potential evaluation of DC-RNA based vaccination approach in this patient population. Cells harvested from medulloblastoma patient leukapheresis following induction chemotherapy and granulocyte colony stimulating factor mobilization were cryopreserved prior to use in DC generation. DCs were generated from the adherent CD14+ monocytes using standard procedures and analyzed for cell recovery, phenotype and function. To summarize, 4 out of 5 patients (80%) had sufficient monocyte recovery to permit DC generation, and we were able to generate DCs from 3 out of these 4 patient samples (75%). Overall, we successfully generated DCs that met phenotypic requisites for DC-based cancer therapy from 3 out of 5 (60%) patient samples and met both phenotypic and functional requisites from 2 out of 5 (40%) patient samples. This study highlights the potential to generate functional DCs for further clinical treatments from refractory patients that have been heavily pretreated with myelosuppressive chemotherapy. Here we demonstrate the utility of evaluating the effect of the currently employed standard-of-care therapies on the ex vivo generation of DCs for DC-based clinical studies in cancer patients.

Serum macrophage-derived chemokine/CCL22 levels are associated with glioma risk, CD4 T cell lymphopenia and survival time

Defects in antigen presenting cell function have been implicated in glioma immunosuppression. We measured peripheral CCL22, a dendritic cell/macrophage derived T cell trafficking chemokine, in sera from 1,208 glioma cases and 976 controls to assess whether it might provide a biomarker of glioma risk, survival and immune dysfunction. Cluster models were used to examine the relationship between CCL22 and glioma risk. Patient survival was assessed using Cox regression models. We also examined the relationship between CCL22 levels and CD4 cell counts, as well as allergy history and IgE levels. CCL22 levels were significantly lower among glioma cases compared with controls (Mean ± SEM: 1.23 ± 0.03 ng/mL in cases vs. 1.60 ± 0.03 ng/mL in controls, p < 0.0001) and this difference remained significant even after controlling for other covariates in the cluster models (highest quartile versus lowest Odds Ratio = 0.21, p < 0.0001). CD4 cell counts were positively correlated with CCL22 in glioma cases (Spearman r(2) = 0.51, p < 0.01) and were significantly lower in cases compared with controls. Higher CCL22 levels were associated with longer survival in all cases combined and in GBM cases (hazard ratio(allcases) = 0.81; 95% CI: 0.72-0.91, p = 0.0003). CCL22 levels were not associated with IgE level or self-reported allergies. Circulating CCL22 levels are related to both glioma risk and survival duration independent of age, histology, grade and IDH mutation status. CCL22 should be considered a marker of immune status with potential prognostic value.

Brain Tumor Immunotherapy: What have We Learned so Far?

High grade glioma is a rare brain cancer, incurable in spite of modern neurosurgery, radiotherapy, and chemotherapy. Novel approaches are in research, and immunotherapy emerges as a promising strategy. Clinical experiences with active specific immunotherapy demonstrate feasibility, safety and most importantly, but incompletely understood, prolonged long-term survival in a fraction of the patients. In relapsed patients, we developed an immunotherapy schedule and we categorized patients into clinically defined risk profiles. We learned how to combine immunotherapy with standard multimodal treatment strategies for newly diagnosed glioblastoma multiforme patients. The developmental program allows further improvements related to newest scientific insights. Finally, we developed a mode of care within academic centers to organize cell-based therapies for experimental clinical trials in a large number of patients.

FGL2 as a Multimodality Regulator of Tumor-Mediated Immune Suppression and Therapeutic Target in Gliomas

BACKGROUND

Fibrinogen-like protein 2 (FGL2) may promote glioblastoma multiforme (GBM) cancer development by inducing multiple immune-suppression mechanisms.

METHODS

The biological significance of FGL2 expression was assessed using the The Cancer Genome Atlast (TCGA) glioma database and tumor lysates analysis. The therapeutic effects of an anti-Fgl2 antibody and the role of immune suppression regulation by Fgl2 were determined in immune-competent, NOD-scid IL2Rgammanull (NSG), and FcɣRIIB-/- mice (n = 3-18 per group). Data were analyzed with two-way analysis of variance, log-rank survival analysis, and Pearson correlation. All statistical tests were two-sided.

RESULTS

In low-grade gliomas, 72.5% of patients maintained two copies of the FGL2 gene, whereas 83.8% of GBM patients had gene amplification or copy gain. Patients with high levels of FGL2 mRNA in glioma tissues had a lower overall survival (P = .009). Protein levels of FGL2 in GBM lysates were higher relative to low-grade glioma lysates (11.48±5.75ng/mg vs 3.96±1.01ng/mg, P = .003). In GL261 mice treated with an anti-FGL2 antibody, median survival was 27 days compared with only 17 days for mice treated with an isotype control antibody (P = .01). The anti-FGL2 antibody treatment reduced CD39(+) Tregs, M2 macrophages, programmed cell death protein 1 (PD-1), and myeloid-derived suppressor cells (MDSCs). FGL2-induced increases in M2, CD39, and PD-1 were ablated in FcɣRIIB-/- mice.

CONCLUSIONS

FGL2 augments glioma immunosuppression by increasing the expression levels of PD-1 and CD39, expanding the frequency of tumor-supportive M2 macrophages via the FcγRIIB pathway, and enhancing the number of MDSCs and CD39(+) regulatory T cells. Collectively, these results show that FGL2 functions as a key immune-suppressive modulator and has potential as an immunotherapeutic target for treating GBM.

Induction of robust type-I CD8+ T-cell responses in WHO grade 2 low-grade glioma patients receiving peptide-based vaccines in combination with poly-ICLC

PURPOSE

WHO grade 2 low-grade gliomas (LGG) with high risk factors for recurrence are mostly lethal despite current treatments. We conducted a phase I study to evaluate the safety and immunogenicity of subcutaneous vaccinations with synthetic peptides for glioma-associated antigen (GAA) epitopes in HLA-A2(+) adults with high-risk LGGs in the following three cohorts: (i) patients without prior progression, chemotherapy, or radiotherapy (RT); (ii) patients without prior progression or chemotherapy but with prior RT; and (iii) recurrent patients.

EXPERIMENTAL DESIGN

GAAs were IL13Rα2, EphA2, WT1, and Survivin. Synthetic peptides were emulsified in Montanide-ISA-51 and given every 3 weeks for eight courses with intramuscular injections of poly-ICLC, followed by q12 week booster vaccines.

RESULTS

Cohorts 1, 2, and 3 enrolled 12, 1, and 10 patients, respectively. No regimen-limiting toxicity was encountered except for one case with grade 3 fever, fatigue, and mood disturbance (cohort 1). ELISPOT assays demonstrated robust IFNγ responses against at least three of the four GAA epitopes in 10 and 4 cases of cohorts 1 and 3, respectively. Cohort 1 patients demonstrated significantly higher IFNγ responses than cohort 3 patients. Median progression-free survival (PFS) periods since the first vaccine are 17 months in cohort 1 (range, 10-47+) and 12 months in cohort 3 (range, 3-41+). The only patient with large astrocytoma in cohort 2 has been progression-free for more than 67 months since diagnosis.

CONCLUSION

The current regimen is well tolerated and induces robust GAA-specific responses in WHO grade 2 glioma patients. These results warrant further evaluations of this approach. Clin Cancer Res; 21(2); 286-94. ©2014 AACR.

Dendritic cell-based vaccine for the treatment of malignant glioma: a systematic review

OBJECTIVE

Glioblastoma multiforme (GBM) has a poor prognosis. The purpose of this systematic review and meta-analysis was to analyze the outcomes of clinical trials which compared immunotherapy with conventional therapy for the treatment of malignant gliomas.

METHODS

PubMed, Cochrane and Google Scholar databases were searched for relevant studies. The 2-year survival rate was used to evaluate effectiveness of immunotherapy.

RESULTS

Of 171 studies identified, six comparative trials were included in the systematic review. Immunotherapy was associated with a significantly longer OS and 2-year survival compared to conventional therapy.

CONCLUSION

Immunotherapy may improve the survival of patients with GBM.