Current state of immunotherapy for glioblastoma

Combined proteomics/miRNomics of dendritic cell immunotherapy-treated glioblastoma patients as a screening for survival-associated factors

Glioblastoma is the most prevalent and aggressive brain cancer. With a median overall survival of ~15–20 months under standard therapy, novel treatment approaches are desperately needed. A recent phase II clinical trial with a personalized immunotherapy based on tumor lysate-charged dendritic cell (DC) vaccination, however, failed to prolong survival. Here, we investigated tumor tissue from trial patients to explore glioblastoma survival-related factors. We followed an innovative approach of combining mass spectrometry-based quantitative proteomics (n = 36) with microRNA sequencing plus RT-qPCR (n = 38). Protein quantification identified, e.g., huntingtin interacting protein 1 (HIP1), retinol-binding protein 1 (RBP1), ferritin heavy chain (FTH1) and focal adhesion kinase 2 (FAK2) as factor candidates correlated with a dismal prognosis. MicroRNA analysis identified miR-216b, miR-216a, miR-708 and let-7i as molecules potentially associated with favorable tissue characteristics as they were enriched in patients with a comparably longer survival. To illustrate the utility of integrated miRNomics and proteomics findings, focal adhesion was studied further as one example for a pathway of potential general interest.

Taken together, we here mapped possible drivers of glioblastoma outcome under immunotherapy in one of the largest DC vaccination tissue analysis cohorts so far—demonstrating usefulness and feasibility of combined proteomics/miRNomics approaches. Future research should investigate agents that sensitize glioblastoma to (immuno)therapy—potentially building on insights generated here.

Glioblastoma is an aggressive form of brain cancer and effective immunotherapeutics are limited, with treatment currently based on chemotherapy and radiotherapy. A recent phase II clinical trial tested a personalized, targeted dendritic cell-based immunotherapy but there was no observed improvement in patient survival or progression-free survival compared to standard-of-care therapy. Here, Carmen Visus and colleagues have used tumor tissue samples from glioblastoma patients involved in this trial and receiving immunotherapy. Using a combination of mass spectrometry-based proteomics, microRNA sequencing and RT-qPCR they identified factors associated with survival or poor prognosis. Proteomics associated poor prognosis with various proteins including focal adhesion kinase 2 (FAK2), whilst microRNAs, miR-216b, miR-216a, miR-708 and let-7i, were associated with longer survival. Focussing on one pathway, FAK2, they integrated the proteomic and microRNA datasets and saw a negative association with overall survival across all patients. To test this, they added an FAK inhibitor to glioblastoma cell lines, including cells isolated from trial patients, and observed inhibition of gliomaspheres in treated cells, providing insights into potential immunotherapy targets.

How tissue fluidity influences brain tumor progression

Mechanical properties of biological tissues and, above all, their solid or fluid behavior influence the spread of malignant tumors. While it is known that solid tumors tend to have higher mechanical rigidity, allowing them to aggressively invade and spread in solid surrounding healthy tissue, it is unknown how softer tumors can grow within a more rigid environment such as the brain. Here, we use in vivo magnetic resonance elastography (MRE) to elucidate the role of anomalous fluidity for the invasive growth of soft brain tumors, showing that aggressive glioblastomas (GBMs) have higher water content while behaving like solids. Conversely, our data show that benign meningiomas (MENs), which contain less water than brain tissue, are characterized by fluid-like behavior. The fact that the 2 tumor entities do not differ in their soft properties suggests that fluidity plays an important role for a tumor's aggressiveness and infiltrative potential. Using tissue-mimicking phantoms, we show that the anomalous fluidity of neurotumors physically enables GBMs to penetrate surrounding tissue, a phenomenon similar to Saffman-Taylor viscous-fingering instabilities, which occur at moving interfaces between fluids of different viscosity. Thus, targeting tissue fluidity of malignant tumors might open horizons for the diagnosis and treatment of cancer.

Convection-enhanced delivery of temozolomide and whole cell tumor immunizations in GL261 and KR158 experimental mouse gliomas

Background

Glioblastomas (GBM) are therapy-resistant tumors with a profoundly immunosuppressive tumor microenvironment. Chemotherapy has shown limited efficacy against GBM. Systemic delivery of chemotherapeutic drugs is hampered by the difficulty of achieving intratumoral levels as systemic toxicity is a dose-limiting factor. Although some of its effects might be mediated by immune reactivity, systemic chemotherapy can also inhibit induced or spontaneous antitumor immune reactivity. Convection-enhanced delivery of temozolomide (CED-TMZ) can tentatively increase intratumoral drug concentration while reducing systemic side effects. The objective of this study was to evaluate the therapeutic effect of intratumorally delivered temozolomide in combination with immunotherapy and whether such therapy can generate a cellular antitumor immune response.

Methods

Single bolus intratumoral injection and 3-day mini-osmotic pumps (Alzet®) were used to deliver intratumoral TMZ in C57BL6 mice bearing orthotopic gliomas. Immunotherapy consisted of subcutaneous injections of irradiated GL261 or KR158 glioma cells. Tumor size and intratumoral immune cell populations were analyzed by immunohistochemistry.

Results

Combined CED-TMZ and immunotherapy had a synergistic antitumor effect in the GL261 model, compared to CED-TMZ or immunotherapy as monotherapies. In the KR158 model, immunization cured a small proportion of the mice whereas addition of CED-TMZ did not have a synergistic effect. However, CED-TMZ as monotherapy prolonged the median survival. Moreover, TMZ bolus injection in the GL261 model induced neurotoxicity and lower cure rate than its equivalent dose delivered by CED. In addition, we found that T-cells were the predominant cells responsible for the TMZ antitumor effect in the GL261 model. Finally, CED-TMZ combined with immunotherapy significantly reduced tumor volume and increased the intratumoral influx of T-cells in both models.

Conclusions

We show that immunotherapy synergized with CED-TMZ in the GL261 model and cured animals in the KR158 model. Single bolus administration of TMZ was effective with a narrower therapeutic window than CED-TMZ. Combined CED-TMZ and immunotherapy led to an increase in the intratumoral influx of T-cells. These results form part of the basis for the translation of the therapy to patients with GBM but the dosing and timing of delivery will have to be explored in depth both experimentally and clinically.

Response Assessment in Neuro-Oncology Criteria for Gliomas: Practical Approach Using Conventional and Advanced Techniques

The Response Assessment in Neuro-Oncology criteria were developed as an objective tool for radiologic assessment of treatment response in high-grade gliomas. Imaging plays a critical role in the management of the patient with glioma, from initial diagnosis to posttreatment follow-up, which can be particularly challenging for radiologists. Interpreting findings after surgery, radiation, and chemotherapy requires profound knowledge about the tumor biology, as well as the peculiar changes expected to ensue as a consequence of each treatment technique. In this article, we discuss the imaging findings associated with tumor progression, tumor response, pseudoprogression, and pseudoresponse according to the Response Assessment in Neuro-Oncology criteria for high-grade and lower-grade gliomas. We describe relevant practical issues when evaluating patients with glioma, such as the need for imaging in the first 48 hours, the radiation therapy planning and isodose curves, the significance of T2/FLAIR hyperintense lesions, the impact of the timing for the evaluation after radiation therapy, and the definition of progressive disease on the histologic specimen. We also illustrate the correlation among the findings on conventional MR imaging with advanced techniques, such as perfusion, diffusion-weighted imaging, spectroscopy, and amino acid PET. Because many of the new lesions represent a mixture of tumor cells and tissue with radiation injury, the radiologist aims to identify the predominant component of the lesion and categorize the findings according to Response Assessment in Neuro-Oncology criteria so that the patient can receive the best treatment.

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.

A novel Buthus martensii Karsch chlorotoxin derivative for glioma SPECT imaging

An increasing number of studies show the diagnostic and therapeutic potential of scorpion venoms and toxins in cancer, including malignant glioma that represents the most fatal primary brain tumors.

Autologous and Pooled Tumor Lysates in Combined Immunotherapy of Patients with Glioblastoma

Although major progress has been made in the standard treatment for glioblastomas, encompassing the maximal surgical resection, chemotherapy and radiation therapy, it is possible to increase survival rates significantly only in a few patients. Therefore, it is necessary to explore new therapeutic modalities, one of which is immunotherapy.

The aim of the study was to evaluate the efficacy of the combined use of autologous and pooled tumor lysates in comprehensive treatment of patients with glioblastoma.

The blood-brain barrier and blood-tumour barrier in brain tumours and metastases

For a blood-borne cancer therapeutic agent to be effective, it must cross the blood vessel wall to reach cancer cells in adequate quantities, and it must overcome the resistance conferred by the local microenvironment around cancer cells. The brain microenvironment can thwart the effectiveness of drugs against primary brain tumours as well as brain metastases. In this Review, we highlight the cellular and molecular components of the blood-brain barrier (BBB), a specialized neurovascular unit evolved to maintain brain homeostasis. Tumours are known to compromise the integrity of the BBB, resulting in a vasculature known as the blood-tumour barrier (BTB), which is highly heterogeneous and characterized by numerous distinct features, including non-uniform permeability and active efflux of molecules. We discuss the challenges posed by the BBB and BTB for drug delivery, how multiple cell types dictate BBB function and the role of the BTB in disease progression and treatment. Finally, we highlight emerging molecular, cellular and physical strategies to improve drug delivery across the BBB and BTB and discuss their impact on improving conventional as well as emerging treatments, such as immune checkpoint inhibitors and engineered T cells. A deeper understanding of the BBB and BTB through the application of single-cell sequencing and imaging techniques, and the development of biomarkers of BBB integrity along with systems biology approaches, should enable new personalized treatment strategies for primary brain malignancies and brain metastases.

Nanocarrier-based drug combination therapy for glioblastoma

The current achievements in treating glioblastoma (GBM) patients are not sufficient because many challenges exist, such as tumor heterogeneity, the blood brain barrier, glioma stem cells, drug efflux pumps and DNA damage repair mechanisms. Drug combination therapies have shown increasing benefits against those challenges. With the help of nanocarriers, enhancement of the efficacy and safety could be gained using synergistic combinations of different therapeutic agents. In this review, we will discuss the major issues for GBM treatment, the rationales of drug combinations with or without nanocarriers and the principle of enhanced permeability and retention effect involved in nanomedicine-based tumor targeting and promising nanodiagnostics or -therapeutics. We will also summarize the recent progress and discuss the clinical perspectives of nanocarrier-based combination therapies. The goal of this article was to provide better understanding and key considerations to develop new nanomedicine combinations and nanotheranostics options to fight against GBM.

Comorbid Medical Conditions as Predictors of Overall Survival in Glioblastoma Patients

Glioblastoma (GBM) is an aggressive central nervous system tumor with a poor prognosis. This study was conducted to determine any comorbid medical conditions that are associated with survival in GBM. Data were collected from medical records of all patients who presented to VCU Medical Center with GBM between January 2005 and February 2015. Patients who underwent surgery/biopsy were considered for inclusion. Cox proportional hazards regression modeling was performed to assess the relationship between survival and sex, race, and comorbid medical conditions. 163 patients met inclusion criteria. Comorbidities associated with survival on individual-characteristic analysis included: history of asthma (Hazard Ratio [HR]: 2.63; 95% Confidence Interval [CI]: 1.24–5.58; p = 0.01), hypercholesterolemia (HR: 1.95; 95% CI: 1.09–3.50; p = 0.02), and incontinence (HR: 2.29; 95% CI: 0.95–5.57; p = 0.07). History of asthma (HR: 2.22; 95% CI: 1.02–4.83; p = 0.04) and hypercholesterolemia (HR: 1.99; 95% CI: 1.11–3.56; p = 0.02) were associated with shorter survival on multivariable analysis. Surgical patients with GBM who had a prior history of asthma or hypercholesterolemia had significantly higher relative risk for mortality on individual-characteristic and multivariable analyses.

CCR2 inhibition reduces tumor myeloid cells and unmasks a checkpoint inhibitor effect to slow progression of resistant murine gliomas

Immunotherapy directed at the PD-L1/PD-1 axis has produced treatment advances in various human cancers. Unfortunately, progress has not extended to glioblastoma (GBM), with phase III clinical trials assessing anti-PD-1 monotherapy failing to show efficacy in newly diagnosed and recurrent tumors. Myeloid-derived suppressor cells (MDSCs), a subset of immunosuppressive myeloid derived cells, are known to infiltrate the tumor microenvironment of GBM. Growing evidence suggests the CCL2-CCR2 axis is important for this process. This study evaluated the combination of PD-1 blockade and CCR2 inhibition in anti-PD-1-resistant gliomas. CCR2 deficiency unmasked an anti-PD-1 survival benefit in KR158 glioma-bearing mice. CD11b⁺/Ly6C^hi/PD-L1⁺ MDSCs within established gliomas decreased with a concomitant increase in overall CCR2⁺ cells and MDSCs within bone marrow of CCR2-deficient mice. The CCR2 antagonist CCX872 increased median survival as a monotherapy in KR158 glioma-bearing animals and further increased median and overall survival when combined with anti-PD-1. Additionally, combination of CCX872 and anti-PD-1 prolonged median survival time in 005 GSC GBM-bearing mice. In both models, CCX872 decreased tumor associated MDSCs and increased these cells within the bone marrow. Examination of tumor-infiltrating lymphocytes revealed an elevated population, increased IFNγ expression, indicating enhanced cytolytic activity, as well as decreased expression of exhaustion markers in CD4⁺ and CD8⁺ T cells following combination treatment. These data establish that combining CCR2 and PD-1 blockade extends survival in clinically relevant murine glioma models and provides the basis on which to advance this combinatorial treatment toward early-phase human trials.

A review of traditional Chinese medicine for treatment of glioblastoma

Glioblastoma (GBM) is the most common primary malignant intracranial tumor. Due to its high morbidity, high mortality, high recurrence rate, and low cure rate, it has brought great difficulty for treatment. Although the current treatment is multimodal, including surgical resection, radiotherapy, and chemotherapy, it does not significantly improve survival time. The dismal prognosis and inevitable recurrence as well as resistance to chemoradiotherapy may be related to its highly cellular heterogeneity and multiple subclonal populations. Traditional Chinese medicine has its own unique advantages in the prevention and treatment of it. A comprehensive literature search of anti-glioblastoma active ingredients and derivatives from traditional Chinese medicine was carried out in literature published in PubMed, Scopus, Web of Science Cochrane library, CNKI, Wanfang, and VIP database. Hence, this article systematically reviews experimental research progress of some traditional Chinese medicine in treatment of glioblastoma from two aspects: strengthening vital qi and eliminating pathogenic qi. Among, strengthening vital qi medicine includes panax ginseng, licorice, lycium barbarum, angelica sinensis; eliminating pathogenic medicine includes salvia miltiorrhiza bunge, scutellaria baicalensis, coptis rhizoma, thunder god vine, and sophora flavescens. We found that the same active ingredient can act on different signaling pathways, such as ginsenoside Rg3 inhibited proliferation and induced apoptosis via the AKT, MEK signal pathway. Hence, this multi-target, multi-level pathway may bring on a new dawn for the treatment of glioblastoma.

EGFR806-CAR T cells selectively target a tumor-restricted EGFR epitope in glioblastoma

Targeting solid tumor antigens with chimeric antigen receptor (CAR) T cell therapy requires tumor specificity and tolerance toward variability in antigen expression levels. Given the relative paucity of unique cell surface proteins on tumor cells for CAR targeting, we have focused on identifying tumor-specific epitopes that arise as a consequence of target protein posttranslational modification. We designed a CAR using a mAb806-based binder, which recognizes tumor-specific untethered EGFR. The mAb806 epitope is also exposed in the EGFRvIII variant transcript. By varying spacer domain elements of the CAR, we structurally tuned the CAR to recognize low densities of EGFR representative of non-gene amplified expression levels in solid tumors. The appropriately tuned short-spacer 2nd generation EGFR806-CAR T cells showed efficient in vitro cytokine secretion and glioma cell lysis, which was competitively blocked by a short peptide encompassing the mAb806 binding site. Unlike the nonselective Erbitux-based CAR, EGFR806-CAR T cells did not target primary human fetal brain astrocytes expressing wild-type EGFR, but showed a similar level of activity compared to Erbitux-CAR when the tumor-specific EGFRvIII transcript variant was overexpressed in astrocytes. EGFR806-CAR T cells successfully treated orthotopic U87 glioma implants in NSG mice, with 50% of animals surviving to 90 days. With additional IL-2 support, all tumors were eradicate without recurrence after 90 days. In a novel human induced pluripotent stem cell (iPSC)-derived teratoma xenograft model, EGFR806-CAR T cells infiltrated but were not activated in EGFR+ epidermal cell nests as assessed by Granzyme B expression. These results indicate that EGFR806-CAR T cells effectively and selectively target EGFR-expressing tumor cells.

Novel approaches for glioblastoma treatment: Focus on tumor heterogeneity, treatment resistance, and computational tools

BACKGROUND

Glioblastoma (GBM) is a highly aggressive primary brain tumor. Currently, the suggested line of action is the surgical resection followed by radiotherapy and treatment with the adjuvant temozolomide, a DNA alkylating agent. However, the ability of tumor cells to deeply infiltrate the surrounding tissue makes complete resection quite impossible, and, in consequence, the probability of tumor recurrence is high, and the prognosis is not positive. GBM is highly heterogeneous and adapts to treatment in most individuals. Nevertheless, these mechanisms of adaption are unknown.

RECENT FINDINGS

In this review, we will discuss the recent discoveries in molecular and cellular heterogeneity, mechanisms of therapeutic resistance, and new technological approaches to identify new treatments for GBM. The combination of biology and computer resources allow the use of algorithms to apply artificial intelligence and machine learning approaches to identify potential therapeutic pathways and to identify new drug candidates.

CONCLUSION

These new approaches will generate a better understanding of GBM pathogenesis and will result in novel treatments to reduce or block the devastating consequences of brain cancers.

Siglecs, Novel Immunotherapy Targets, Potentially Enhance The Effectiveness of Existing Immune Checkpoint Inhibitors in Glioma Immunotherapy

Background

Inhibitors of immune checkpoints have shown little effect in clinical trials involving glioma patients. Here, we explored novel targets for use in future treatments. Previous studies showed the sialic acid-binding Ig-like lectin (Siglec) family to have a specific role in immunosuppression. We aimed to study the characteristics and immune function of Siglec family members.

Methods

Transcriptome data from 1024 glioma samples and 1551 glioma single cells were used in our study. Clinical and molecular pathology information was also included. Statistical, bioinformatical methods, and single-cell sequencing analysis were applied to investigate the role of Siglec family members.

Results

Siglecs-5, −7, −9, and −16 showed a significant correlation with immunosuppression in glioma. They are typically expressed in higher grade, IDH-wildtype, and mesenchymal subtype gliomas. Siglec-5, −7, and −9 had a similar immune function to TIM-3, while Siglec-16 was similar to PD-L1, suppressing tumor immunity via different mechanisms. Joint use of Siglec-inhibitors and immune checkpoint inhibitors could prolong the survival of glioma patients.

Conclusion

Siglec-5, −7, −9, and −16 suppressed tumor immunity in different ways. Joint usage of inhibitors may be an effective means to improve the efficacy of glioma immunotherapy.

Metronomic capecitabine as an immune modulator in glioblastoma patients reduces myeloid-derived suppressor cells

BACKGROUNDMyeloid-derived suppressor cells (MDSCs) are elevated in the circulation of patients with glioblastoma (GBM), present in tumor tissue, and associated with poor prognosis. While low-dose chemotherapy reduces MDSCs in preclinical models, the use of this strategy to reduce MDSCs in GBM patients has yet to be evaluated.METHODSA phase 0/I dose-escalation clinical trial was conducted in patients with recurrent GBM treated 5-7 days before surgery with low-dose chemotherapy via capecitabine, followed by concomitant low-dose capecitabine and bevacizumab. Clinical outcomes, including progression-free and overall survival, were measured, along with safety and toxicity profiles. Over the treatment time course, circulating MDSC levels were measured by multiparameter flow cytometry, and tumor tissue immune profiles were assessed via time-of-flight mass cytometry.RESULTSEleven patients total were enrolled across escalating dose cohorts of 150, 300, and 450 mg bid. No serious adverse events related to the drug combination were observed. Compared with pretreatment baseline, circulating MDSCs were found to be higher after surgery in the 150-mg treatment arm and lower in the 300-mg and 450-mg treatment arms. Increased cytotoxic immune infiltration was observed after low-dose capecitabine compared with untreated GBM patients in the 300-mg and 450-mg treatment arms.CONCLUSIONSLow-dose, metronomic capecitabine in combination with bevacizumab was well tolerated in GBM patients and was associated with a reduction in circulating MDSC levels and an increase in cytotoxic immune infiltration into the tumor microenvironment.TRIAL REGISTRATIONClinicalTrials.gov NCT02669173.FUNDINGThis research was funded by the Cleveland Clinic, Case Comprehensive Cancer Center, the Musella Foundation, B*CURED, the NIH, the National Cancer Institute, the Sontag Foundation, Blast GBM, the James B. Pendleton Charitable Trust, and the Dr. Miriam and Sheldon G. Adelson Medical Research Foundation. Capecitabine was provided in kind by Mylan Pharmaceuticals.

CAR-Engineered NK Cells for the Treatment of Glioblastoma: Turning Innate Effectors Into Precision Tools for Cancer Immunotherapy

Glioblastoma (GB) is the most common and aggressive primary brain tumor in adults and currently incurable. Despite multimodal treatment regimens, median survival in unselected patient cohorts is <1 year, and recurrence remains almost inevitable. Escape from immune surveillance is thought to contribute to the development and progression of GB. While GB tumors are frequently infiltrated by natural killer (NK) cells, these are actively suppressed by the GB cells and the GB tumor microenvironment. Nevertheless, ex vivo activation with cytokines can restore cytolytic activity of NK cells against GB, indicating that NK cells have potential for adoptive immunotherapy of GB if potent cytotoxicity can be maintained in vivo. NK cells contribute to cancer immune surveillance not only by their direct natural cytotoxicity which is triggered rapidly upon stimulation through germline-encoded cell surface receptors, but also by modulating T-cell mediated antitumor immune responses through maintaining the quality of dendritic cells and enhancing the presentation of tumor antigens. Furthermore, similar to T cells, specific recognition and elimination of cancer cells by NK cells can be markedly enhanced through expression of chimeric antigen receptors (CARs), which provides an opportunity to generate NK-cell therapeutics of defined specificity for cancer immunotherapy. Here, we discuss effects of the GB tumor microenvironment on NK-cell functionality, summarize early treatment attempts with ex vivo activated NK cells, and describe relevant CAR target antigens validated with CAR-T cells. We then outline preclinical approaches that employ CAR-NK cells for GB immunotherapy, and give an overview on the ongoing clinical development of ErbB2 (HER2)-specific CAR-NK cells currently applied in a phase I clinical trial in glioblastoma patients.

Therapeutic targeting of tumor-associated myeloid cells synergizes with radiation therapy for glioblastoma

Tumor-associated myeloid cells (TAMCs) are key drivers of immunosuppression in the tumor microenvironment, which profoundly impedes the clinical response to immune-dependent and conventional therapeutic modalities. As a hallmark of glioblastoma (GBM), TAMCs are massively recruited to reach up to 50% of the brain tumor mass. Therefore, they have recently been recognized as an appealing therapeutic target to blunt immunosuppression in GBM with the hope of maximizing the clinical outcome of antitumor therapies. Here we report a nano-immunotherapy approach capable of actively targeting TAMCs in vivo. As we found that programmed death-ligand 1 (PD-L1) is highly expressed on glioma-associated TAMCs, we rationally designed a lipid nanoparticle (LNP) formulation surface-functionalized with an anti-PD-L1 therapeutic antibody (αPD-L1). We demonstrated that this system (αPD-L1-LNP) enabled effective and specific delivery of therapeutic payload to TAMCs. Specifically, encapsulation of dinaciclib, a cyclin-dependent kinase inhibitor, into PD-L1-targeted LNPs led to a robust depletion of TAMCs and an attenuation of their immunosuppressive functions. Importantly, the delivery efficiency of PD-L1-targeted LNPs was robustly enhanced in the context of radiation therapy (RT) owing to the RT-induced up-regulation of PD-L1 on glioma-infiltrating TAMCs. Accordingly, RT combined with our nano-immunotherapy led to dramatically extended survival of mice in 2 syngeneic glioma models, GL261 and CT2A. The high targeting efficiency of αPD-L1-LNP to human TAMCs from GBM patients further validated the clinical relevance. Thus, this study establishes a therapeutic approach with immense potential to improve the clinical response in the treatment of GBM and warrants a rapid translation into clinical practice.

A tumor-targeting nanomedicine carrying the p53 gene crosses the blood-brain barrier and enhances anti-PD-1 immunotherapy in mouse models of glioblastoma

Despite its anticipated clinical potential, anti-PD-1 immunotherapy has only yielded poor outcomes in recent clinical trials for glioblastoma patients. Strategies combining anti-PD-1 antibody with other treatment modalities are being explored to alter the immunosuppressive microenvironment that appears to characterize these anti-PD-1-insensitive tumors. Here, we evaluated whether introducing wild-type p53 gene via a tumor-targeting nanomedicine (termed SGT-53) could provide immune stimulation and augment anti-PD-1 therapy in mouse syngeneic GL261 tumor models (either subcutaneous or intracranial). In both models, anti-PD-1 monotherapy had no demonstrable therapeutic effect. However, combining anti-PD-1 with our investigational nanomedicine SGT-53 was very effective in inhibiting tumor growth, inducing tumor cell apoptosis and increasing intratumoral T-cell infiltration. A significant survival benefit was observed in mice bearing intracranial glioblastoma receiving combination treatment. Importantly, SGT-53 upregulated PD-L1 expression both in vitro and in vivo. Transcriptome analysis revealed modulation of genes linked to either cancer progression or immune activation after combination treatment. Our data suggest that SGT-53 can boost antitumor immunity and sensitize glioblastoma to anti-PD-1 therapy by converting immunologically "cold" tumors into "hot" tumors. Combining SGT-53 with anti-PD-1 might benefit more patients from anti-PD-1 immunotherapy and our data support evaluation of this combination in patients with glioblastoma.

Increased RLIP76 expression in IDH1 wild‑type glioblastoma multiforme is associated with worse prognosis

Mutation of the isocitrate dehydrogenase (IDH) gene is regarded a novel indicator for the prognosis of patients with glioma. However, the role of the IDH1 gene mutations in carcinogenesis and the mechanisms underlying their function in glioblastoma multiforme (GBM) remain unknown. The present study aimed to determine whether the association of RLIP76 with the different IDH1 mutational status could serve as a putative biomarker for improving disease prognosis. Quantitative PCR, western blotting and immunohistochemical staining assays were used to investigate the expression levels of RLIP76 in 124 patients with GBM with different IDH1 mutational status. In addition, the association between RLIP76 expression, IDH1 mutational status and clinicopathological characteristics was investigated. The effects of RLIP76 expression and IDH1 mutational status on cell proliferation, cell apoptosis, and cell signaling were examined by Cell Counting Kit-8, flow cytometry and western blot assays, respectively. The data demonstrated that IDH1 wild-type (IDH1^Wt) patients with low RLIP76 expression exhibited improved overall and progression-free survival. This effect was not observed in patients with IDH1 mutant (IDH1^Mut) GBM. In vitro assays demonstrated that knockdown of IDH1 or overexpression of the IDH1 R132H mutation suppressed cell proliferation and promoted cell apoptosis in U87 glioma cells. Mechanistic studies further indicated that although the IDH1 R132H mutant phenotype exhibited similar antitumor effects on GBM cells as those observed with the IDH1 knockdown, it acted via a different mechanism with regard to the regulation of the apoptosis signaling pathway. IDH1 R132H mutant cells promoted p53-induced apoptosis, while the IDH1 knockdown inhibited the RLIP76-dependent apoptotic pathway in glioma cells. The findings of the present study provided insight to the contribution of IDH1 mutation in the development of GBM and indicated that RLIP76 may be considered as a prognostic biomarker of IDH1^Wt GBM.

CLEC5A expressed on myeloid cells as a M2 biomarker relates to immunosuppression and decreased survival in patients with glioma

Glioma is the most common tumor in the central nervous system that portends a poor prognosis. Key genes negatively related to survival may provide targets for therapy to improve the outcome of glioma. Here, we report a protein-coding gene CLEC5A, which is the top 1 gene by univariate Cox regression analysis of 524 primary GBM samples. Expression of CLEC5A is significantly correlated with decreased overall survival in patients with glioma via large-scale analysis. An analysis of 2589 patient samples showed that CLEC5A expression is higher in (1) glioblastoma than in lower-grade glioma and nontumor tissue, (2) in the mesenchymal subtype than in other subtypes, and (3) in IDH1-wild type glioblastoma than in IDH1-mutated glioblastoma. Notably, this tumor-associated biomarker is expressed preferentially on myeloid cells over glioma cells. And it shows a strong co-expression with M2 macrophage biomarker. Furthermore, CLEC5A-associated genes are enriched in immunosuppressive biological processes. The silico flow cytometry also showed CLEC5A expression related to less tumor purity and more tumor-promoting leukocytes infiltration. In conclusion, we proposed a new M2 biomarker expressed on myeloid cells that may decrease survival in patients with glioma through immunosuppressive mechanisms.

Application Of Adoptive Immunotherapy In Ovarian Cancer

Ovarian cancer (OC) has been the most fatal gynecological disease that threatens women's health. Surgery and platinum-based chemotherapy are the basic ovarian cancer treatments that can improve survival, but the five-year survival rate has not improved because of delayed diagnosis, drug resistance, and recurrence. Novel treatments are needed to improve the prognosis and survival rate of ovarian cancer patients. In recent years, adoptive cell therapy (ACT) has received increasing attention as an emerging therapeutic strategy in the treatment of solid tumors including OC. ACT has shown promising results in many preclinical and clinical trials of OC. The application of ACT depends on different effector cells, such as lymphokine-activated killer (LAK) cells, tumor-infiltrating lymphocytes (TILs), and genetically modified T cells. In this review, we focus on adoptive immunotherapies in ovarian cancer and summarize completed and ongoing preclinical/clinical trials. The future development directions and obstacles for ACT in OC treatment are discussed.

Blocking lncRNA MALAT1/miR-199a/ZHX1 Axis Inhibits Glioblastoma Proliferation and Progression

Zinc fingers and homeoboxes 1 (ZHX1) is a transcription repressor that has been implicated in the tumorigenesis and progression of diverse tumors. The functional role and regulating mechanism of ZHX1 has not been elucidated in glioblastoma (GBM). Previous reports have suggested that a large number of non-coding RNAs play a vital role in glioma initiation and progression. This study aimed to investigate the functional role and co-regulatory mechanisms of the metastasis-associated lung adenocarcinoma transcript-1 (MALAT1)/ microRNA-199a (miR-199a)/ZHX1 axis in GBM. We analyzed the expression of the MALAT1/miR-199a/ZHX1 axis and its correlation with patients' overall survival using two different glioma gene-expression datasets. A series of in vitro and in vivo studies including dual luciferase reporter assay, fluorescence in situ hybridization (FISH), RNA immunoprecipitation, and pull-down experiments were completed to elucidate the biological significance of the MALAT1/miR-199a/ZHX1 axis in promoting glioma proliferation and progression. Elevated ZHX1 expression correlated with poor prognosis in GBM patients, and in vitro studies demonstrated that ZHX1 attenuated GBM cell apoptosis by downregulation of pro-apoptotic protein (Bax) and upregulation of anti-apoptotic protein (Bcl-2). Furthermore, knockdown of MALAT1 inhibited GBM proliferation and progression in vitro and reduced tumor volume and prolonged survival in an orthotopic GBM murine model. Finally, we demonstrated that MALAT1 promoted ZHX1 expression via acting as a competing endogenous RNA by sponging miR-199a. The MALAT1/miR-199a/ZHX1 axis promotes GBM cell proliferation and progression in vitro and in vivo, and its expression negatively correlates with GBM patient survival. Blocking the MALAT1/miR-199a/ZHX1 axis can serve as a novel therapeutic strategy for treating GBM.

Myeloid-Derived Suppressive Cells Promote B cell-Mediated Immunosuppression via Transfer of PD-L1 in Glioblastoma

The potent immunosuppression induced by glioblastoma (GBM) is one of the primary obstacles to finding effective immunotherapies. One hallmark of the GBM-associated immunosuppressive landscape is the massive infiltration of myeloid-derived suppressor cells (MDSC) and, to a lesser extent, regulatory T cells (Treg) within the tumor microenvironment. Here, we showed that regulatory B cells (Breg) are a prominent feature of the GBM microenvironment in both preclinical models and clinical samples. Forty percent of GBM patients (n = 60) scored positive for B-cell tumor infiltration. Human and mouse GBM-associated Bregs were characterized by immunosuppressive activity toward activated CD8⁺ T cells, the overexpression of inhibitory molecules PD-L1 and CD155, and production of immunosuppressive cytokines TGFβ and IL10. Local delivery of B cell-depleting anti-CD20 immunotherapy improved overall survival of animals (IgG vs. anti-CD20 mean survival: 18.5 vs. 33 days, P = 0.0001), suggesting a potential role of Bregs in GBM progression. We unveiled that GBM-associated MDSCs promoted regulatory B-cell function by delivering microvesicles transporting membrane-bound PD-L1, able to be up-taken by tumoral B cells. The transfer of functional PD-L1 via microvesicles conferred Bregs the potential to suppress CD8⁺ T-cell activation and acquisition of an effector phenotype. This work uncovered the role of B cells in GBM physiopathology and provides a mechanism by which the GBM microenvironment controls B cell-mediated immunosuppression.See related Spotlight on p. 1902.

NKG2D Controls Natural Reactivity of Vγ9Vδ2 T Lymphocytes against Mesenchymal Glioblastoma Cells

PURPOSE

Cellular immunotherapies are currently being explored to eliminate highly invasive and chemoradioresistant glioblastoma (GBM) cells involved in rapid relapse. We recently showed that concomitant stereotactic injections of nonalloreactive allogeneic Vγ9Vδ2 T lymphocytes eradicate zoledronate-primed human GBM cells. In the present study, we investigated the spontaneous reactivity of allogeneic human Vγ9Vδ2 T lymphocytes toward primary human GBM cells, in vitro and in vivo, in the absence of any prior sensitization.

EXPERIMENTAL DESIGN

Through functional and transcriptomic analyses, we extensively characterized the immunoreactivity of human Vγ9Vδ2 T lymphocytes against various primary GBM cultures directly derived from patient tumors.

RESULTS

We evidenced that GBM cells displaying a mesenchymal signature are spontaneously eliminated by allogeneic human Vγ9Vδ2 T lymphocytes, a reactivity process being mediated by γδ T-cell receptor (TCR) and tightly regulated by cellular stress-associated NKG2D pathway. This led to the identification of highly reactive Vγ9Vδ2 T lymphocyte populations, independently of a specific TCR repertoire signature. Moreover, we finally provide evidence of immunotherapeutic efficacy in vivo, in the absence of any prior tumor cell sensitization.

CONCLUSIONS

By identifying pathways implicated in the selective natural recognition of mesenchymal GBM cell subtypes, accounting for 30% of primary diagnosed and 60% of recurrent GBM, our results pave the way for novel targeted cellular immunotherapies.

Identification of key candidate genes and pathways in glioblastoma by integrated bioinformatical analysis

Glioblastoma (GBM), characterized by high morbidity and mortality, is one of the most common lethal diseases worldwide. To identify the molecular mechanisms that contribute to the development of GBM, three cohort profile datasets (GSE50161, GSE90598 and GSE104291) were integrated and thoroughly analyzed; these datasets included 57 GBM cases and 22 cases of normal brain tissue. The current study identified differentially expressed genes (DEGs), and analyzed potential candidate genes and pathways. Additionally, a DEGs-associated protein-protein interaction (PPI) network was established for further investigation. Then, the hub genes associated with prognosis were identified using a Kaplan-Meier analysis based on The Cancer Genome Atlas database. Firstly, the current study identified 378 consistent DEGs (240 upregulated and 138 downregulated). Secondly, a cluster analysis of the DEGs was performed based on functions of the DEGs and signaling pathways were analyzed using the enrichment analysis tool on DAVID. Thirdly, 245 DEGs were identified using PPI network analysis. Among them, two co-expression modules comprising of 30 and 27 genes, respectively, and 35 hub genes were identified using Cytoscape MCODE. Finally, Kaplan-Meier analysis of the hub genes revealed that the increased expression of calcium-binding protein 1 (CABP1) was negatively associated with relapse-free survival. To summarize, all enriched Gene Ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways may participate in mechanisms underlying GBM occurrence and progression, however further studies are required. CABP1 may be a key gene associated with the biological process of GBM development and may be involved in a crucial mechanism of GBM progression.

Long non-coding RNA, HOTAIRM1, promotes glioma malignancy by forming a ceRNA network

Long non-coding RNAs play critical roles in tumorigenesis and the immune process. In this study, RNA sequencing data for 946 glioma samples from The Cancer Genome Atlas and the Chinese Glioma Genome Atlas databases were analyzed to evaluate the prognostic value and function of homeobox A transcript antisense RNA myeloid-specific (HOTAIRM)1. HOTAIRM1 expression was associated with clinical and molecular features of glioma: patients with high HOTAIRM1 expression were more likely to be classified as malignant cases, and elevated HOTAIRM1 level was associated with shorter survival time in subgroups stratified by clinical and molecular features. A multivariate Cox regression analysis showed that HOTAIRM1 was an independent prognostic factor for patient outcome. In vitro experiments revealed that HOTAIRM1 knockdown suppressed the malignant behavior of glioma and increased tumor sensitivity to temozolomide. The results of an in silico analysis indicated that HOTAIRM1 promotes the malignancy of glioma by acting as a sponge for microRNA (miR)-129-5p and miR-495-3p. HOTAIRM1 overexpression was also associated with immune activation characterized by enhanced T cell-mediated immune and inflammatory responses. These results suggest that HOTAIRM1 is a prognostic biomarker and potential therapeutic target in glioma.

Mechanisms of immunotherapy resistance: lessons from glioblastoma

Glioblastoma (GBM) is the deadliest form of brain cancer, with a median survival of less than 2 years despite surgical resection, radiation, and chemotherapy. GBM's rapid progression, resistance to therapy, and inexorable recurrence have been attributed to several factors, including its rapid growth rate, its molecular heterogeneity, its propensity to infiltrate vital brain structures, the regenerative capacity of treatment-resistant cancer stem cells, and challenges in achieving high concentrations of chemotherapeutic agents in the central nervous system. Escape from immunosurveillance is increasingly recognized as a landmark event in cancer biology. Translation of this framework to clinical oncology has positioned immunotherapy as a pillar of cancer treatment. Amid the bourgeoning successes of cancer immunotherapy, GBM has emerged as a model of resistance to immunotherapy. Here we review the mechanisms of immunotherapy resistance in GBM and discuss how insights into GBM-immune system interactions might inform the next generation of immunotherapeutics for GBM and other resistant pathologies.

The biological macromolecule Nocardia rubra cell-wall skeleton as an avenue for cell-based immunotherapy

Promoting the antitumor effects of cell-based immunotherapy for clinical application remains a difficult challenge. Nocardia rubra cell-wall skeleton (N-CWS) is an immunotherapeutic agent for cancers that have been proven to possess the ability to activate immune response without showing toxicity. However, its effects on immune cells that are derived from tumor patients and cultured in vitro remain unclear. As expected, N-CWS can enhance the proliferation and viability of cytokine-induced killer (CIK) cells, dendritic cells (DCs), and natural killer (NK) cells. The maturation of DCs and specific cytotoxicity against NK cells and CIK cells were consistently promoted. The TUNEL-staining and the Annexin V/propidium iodide assay revealed that after treatment with N-CWS, the stimulated CIK/NK cells could induce DNA breaks in tumor cells. Furthermore, quantitative real-time polymerase chain reaction and western blot analysis showed upregulation of proapoptotic biomarkers (caspase-3 and caspase-9) and a downregulation of the antiapoptotic biomarker Bcl-2 in the tumor cells of the N-CWS-treated group, indicating that N-CWS could induce hepatocellular carcinoma cell apoptosis via CIK/NK cells. Finally, CIK/NK cells could notably suppress the invasion and migration of tumor cells in the presence of N-CWS. Our study provides evidence that N-CWS could significantly increase the growth of CIK cells, DCs, and NK cells, particularly due to its robust antitumor activities by inducing apoptosis, and attenuate the invasion and migration of tumor cells.

Mesenchymal transition and increased therapy resistance of glioblastoma cells is related to astrocyte reactivity

Grade IV astrocytoma/glioblastoma multiforme (GBM) is essentially incurable, partly due to its heterogenous nature, demonstrated even within the glioma-initiating cell (GIC) population. Increased therapy resistance of GICs is coupled to transition into a mesenchymal (MES) cell state. The GBM MES molecular signature displays a pronounced inflammatory character and its expression vary within and between tumors. Herein, we investigate how MES transition of GBM cells relates to inflammatory responses of normal astroglia. In response to CNS insults astrocytes enter a reactive cell state and participate in directing neuroinflammation and subsequent healing processes. We found that the MES signature show strong resemblance to gene programs induced in reactive astrocytes. Likewise, astrocyte reactivity gene signatures were enriched in therapy-resistant MES-like GIC clones. Variable expression of astrocyte reactivity related genes also largely defined intratumoral GBM cell heterogeneity at the single-cell level and strongly correlated with our previously defined therapy-resistance signature (based on linked molecular and functional characterization of GIC clones). In line with this, therapy-resistant MES-like GIC secreted immunoregulatory and tissue repair related proteins characteristic of astrocyte reactivity. Moreover, sensitive GIC clones could be made reactive through long-term exposure to the proinflammatory cytokine interleukin 1 beta (IL1β). IL1β induced a slow MES transition, increased therapy resistance, and a shift in DNA methylation profile towards that of resistant clones, which confirmed a slow reprogramming process. In summary, GICs enter through MES transition a reactive-astrocyte-like cell state, connected to therapy resistance. Thus, from a biological point of view, MES GICs would preferably be called 'reactive GICs'. The ability of GBM cells to mimic astroglial reactivity contextualizes the immunomodulatory and microenvironment reshaping abilities of GBM cells that generate a tumor-promoting milieu. This insight will be important to guide the development of future sensitizing therapies targeting treatment-resistant relapse-driving cell populations as well as enhancing the efficiency of immunotherapies in GBM. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Blood-brain barrier permeable nano immunoconjugates induce local immune responses for glioma therapy

Brain glioma treatment with checkpoint inhibitor antibodies to cytotoxic T-lymphocyte-associated antigen 4 (a-CTLA-4) and programmed cell death-1 (a-PD-1) was largely unsuccessful due to their inability to cross blood-brain barrier (BBB). Here we describe targeted nanoscale immunoconjugates (NICs) on natural biopolymer scaffold, poly(β-L-malic acid), with covalently attached a-CTLA-4 or a-PD-1 for systemic delivery across the BBB and activation of local brain anti-tumor immune response. NIC treatment of mice bearing intracranial GL261 glioblastoma (GBM) results in an increase of CD8+ T cells, NK cells and macrophages with a decrease of regulatory T cells (Tregs) in the brain tumor area. Survival of GBM-bearing mice treated with NIC combination is significantly longer compared to animals treated with single checkpoint inhibitor-bearing NICs or free a-CTLA-4 and a-PD-1. Our study demonstrates trans-BBB delivery of tumor-targeted polymer-conjugated checkpoint inhibitors as an effective GBM treatment via activation of both systemic and local privileged brain tumor immune response.

Circular RNA CircMTO1 Inhibits Proliferation of Glioblastoma Cells via miR-92/WWOX Signaling Pathway

Background

Circular RNA circMTO1 has been reported to inhibit the progression of many types of cancers. However, the role of circMTO1 in the progression of glioblastoma remains unclear. The purpose of our study was to explore the potential involvement of circMTO1 in glioblastoma.

Material/Methods

The expression of circMTO1 in human glioblastoma tissues was determined via quantitative real-time polymerase chain reaction (qRT-PCR). The effect of circMTO1 on proliferation of human glioblastoma cell line U251 was assessed through the Cell Counting Kit-8 (CCK-8) and colony formation assay. The regulatory interaction between circMTO1 and miR-92 was explored by bioinformatics prediction and luciferase reporter assay.

Results

We showed that circMTO1 was markedly downregulated in glioblastoma tissues compared with adjacent normal tissues. Lower circMTO1 level was significantly associated with shorter overall survival among patients with glioblastoma. In addition, circMTO1 inhibited proliferation of cell U251 cells. Mechanistically, circMTO1 upregulates the expression of WWOX in U251 cells, and WWOX mediates circMTO1-induced inhibition of proliferation of U251 cells. In addition, miR-92 downregulates the expression of WWOX by the targeting its mRNA 3′ UTR. More importantly, circMTO1 directly interact with miR-92, and subsequently serves as a miRNA sponge to upregulate WWOX expression.

Conclusions

Our results demonstrate that circMTO1 inhibits the proliferation of glioblastoma cells via the miR-92/WWOX signaling pathway.

Human Mesenchymal glioblastomas are characterized by an increased immune cell presence compared to Proneural and Classical tumors

Glioblastoma (GBM) is the most aggressive malignant primary brain tumor in adults, with a median survival of 14.6 months. Recent efforts have focused on identifying clinically relevant subgroups to improve our understanding of pathogenetic mechanisms and patient stratification. Concurrently, the role of immune cells in the tumor microenvironment has received increasing attention, especially T cells and tumor-associated macrophages (TAM). The latter are a mixed population of activated brain-resident microglia and infiltrating monocytes/monocyte-derived macrophages, both of which express ionized calcium-binding adapter molecule 1 (IBA1). This study investigated differences in immune cell subpopulations among distinct transcriptional subtypes of GBM. Human GBM samples were molecularly characterized and assigned to Proneural, Mesenchymal or Classical subtypes as defined by NanoString nCounter Technology. Subsequently, we performed and analyzed automated immunohistochemical stainings for TAM as well as specific T cell populations. The Mesenchymal subtype of GBM showed the highest presence of TAM, CD8⁺, CD3⁺ and FOXP3⁺ T cells, as compared to Proneural and Classical subtypes. High expression levels of the TAM-related gene AIF1, which encodes the TAM-specific protein IBA1, correlated with a worse prognosis in Proneural GBM, but conferred a survival benefit in Mesenchymal tumors. We used our data to construct a mathematical model that could reliably identify Mesenchymal GBM with high sensitivity using a combination of the aforementioned cell-specific IHC markers. In conclusion, we demonstrated that molecularly distinct GBM subtypes are characterized by profound differences in the composition of their immune microenvironment, which could potentially help to identify tumors amenable to immunotherapy.

Glycan modification of glioblastoma-derived extracellular vesicles enhances receptor-mediated targeting of dendritic cells

Glioblastoma is the most prevalent and aggressive primary brain tumour for which total tumour lysate-pulsed dendritic cell vaccination is currently under clinical evaluation. Glioblastoma extracellular vesicles (EVs) may represent an enriched cell-free source of tumour-associated (neo-) antigens to pulse dendritic cells (DCs) for the initiation of an anti-tumour immune response. Capture and uptake of EVs by DCs could occur in a receptor-mediated and presumably glycan-dependent way, yet the glycan composition of glioblastoma EVs is unknown. Here, we set out to characterize the glycocalyx composition of glioblastoma EVs by lectin-binding ELISA and comprehensive immunogold transmission electron microscopy (immuno-TEM). The surface glycan profile of human glioblastoma cell line-derived EVs (50-200 nm) was dominated by α-2,3- and α-2,6 linked sialic acid-capped complex N-glycans and bi-antennary N-glycans. Since sialic acids can trigger immune inhibitory sialic acid-binding Ig-like lectin (Siglec) receptors, we screened for Siglec ligands on the EVs. Glioblastoma EVs showed significant binding to Siglec-9, which is highly expressed on DCs. Surprisingly, however, glioblastoma EVs lack glycans that could bind Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Non-integrin (DC-SIGN, CD209), a receptor that mediates uptake and induction of CD4+ and CD8+ T cell activation. Therefore, we explored whether modification of the EV glycan surface could reduce immune inhibitory Siglec binding, while enhancing EV internalization by DCs in a DC-SIGN dependent manner. Desialylation with a pan-sialic acid hydrolase led to reduction of sialic acid expression on EVs. Moreover, insertion of a high-affinity ligand (LewisY) for DC-SIGN resulted in a four-fold increase of uptake by monocyte-derived DCs. In conclusion, we show that the glycocalyx composition of EVs is a key factor of efficient DC targeting and that modification of the EV glycocalyx potentiates EVs as anti-cancer vaccine.

Development of a Human Cytomegalovirus (HCMV)-Based Therapeutic Cancer Vaccine Uncovers a Previously Unsuspected Viral Block of MHC Class I Antigen Presentation

Human cytomegalovirus (HCMV) induces a uniquely high frequency of virus-specific effector/memory CD8+ T-cells, a phenomenon termed “memory inflation”. Thus, HCMV-based vaccines are particularly interesting in order to stimulate a sustained and strong cellular immune response against cancer. Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor with high lethality and inevitable relapse. The current standard treatment does not significantly improve the desperate situation underlining the urgent need to develop novel approaches. Although HCMV is highly fastidious with regard to species and cell type, GBM cell lines are susceptible to HCMV. In order to generate HCMV-based therapeutic vaccine candidates, we deleted all HCMV-encoded proteins (immunoevasins) that interfere with MHC class I presentation. The aim being to use the viral vector as an adjuvant for presentation of endogenous tumor antigens, the presentation of high levels of vector-encoded neoantigens and finally the repurposing of bystander HCMV-specific CD8+ T cells to fight the tumor. As neoantigen, we exemplarily used the E6 and E7 proteins of human papillomavirus type 16 (HPV-16) as a non-transforming fusion protein (E6/E7) that covers all relevant antigenic peptides. Surprisingly, GBM cells infected with E6/E7-expressing HCMV-vectors failed to stimulate E6-specific T cells despite high level expression of E6/E7 protein. Further experiments revealed that MHC class I presentation of E6/E7 is impaired by the HCMV-vector although it lacks all known immunoevasins. We also generated HCMV-based vectors that express E6-derived peptide fused to HCMV proteins. GBM cells infected with these vectors efficiently stimulated E6-specific T cells. Thus, fusion of antigenic sequences to HCMV proteins is required for efficient presentation via MHC class I molecules during infection. Taken together, these results provide the preclinical basis for development of HCMV-based vaccines and also reveal a novel HCMV-encoded block of MHC class I presentation.

GARP as an Immune Regulatory Molecule in the Tumor Microenvironment of Glioblastoma Multiforme

Glycoprotein A repetition predominant (GARP), a specific surface molecule of activated regulatory T cells, has been demonstrated to significantly contribute to tolerance in humans by induction of peripheral Treg and regulatory M2-macrophages and by inhibition of (tumorantigen-specific) T effector cells. Previous work identified GARP on Treg, and also GARP on the surface of several malignant tumors, as well as in a soluble form being shedded from their surface, contributing to tumor immune escape. Preliminary results also showed GARP expression on brain metastases of malignant melanoma. On the basis of these findings, we investigated whether GARP is also expressed on primary brain tumors. We showed GARP expression on glioblastoma (GB) cell lines and primary GB tissue, as well as on low-grade glioma, suggesting an important influence on the tumor micromilieu and the regulation of immune responses also in primary cerebral tumors. This was supported by the finding that GB cells led to a reduced, in part GARP-dependent effector T cell function (reduced proliferation and reduced cytokine secretion) in coculture experiments. Interestingly, GARP was localized not only on the cell surface but also in the cytoplasmatic, as well as nuclear compartments in tumor cells. Our findings reveal that GARP, as an immunoregulatory molecule, is located on, as well as in, tumor cells of GB and low-grade glioma, inhibiting effector T cell function, and thus contributing to the immunosuppressive tumor microenvironment of primary brain tumors. As GARP is expressed on activated Treg, as well as on brain tumors, it may be an interesting target for new immunotherapeutic approaches using antibody-based strategies as this indication.

Enhanced anti-angiogenic effects of bevacizumab in glioblastoma treatment upon intranasal administration in polymeric nanoparticles

Glioblastoma multiforme (GBM) is one of the most aggressive cancers, where the aggressiveness of tumor has been associated to its high vascularization rate. Bevacizumab (Avastin®), an anti-angiogenic monoclonal antibody, has been used to decrease the angiogenic profile. To circumvent the blood-brain barrier (BBB) and decrease off-target organ toxicity, bevacizumab-loaded poly(D,L-lactic-co-glycolic acid) nanoparticles (PLGA NP) were developed and intranasally administrated in CD-1 mice to study their pharmacokinetic and pharmacodynamic profile. After 7 days of administration, PLGA NP showed a higher brain bioavailability of bevacizumab when compared to intranasally administrated free bevacizumab. On the other hand, bevacizumab-loaded PLGA NP were able to increase the penetration (higher Cmáx) and the residence time of bevacizumab into the brain (higher Clast). Furthermore, PLGA NP formulation totally prevented bevacizumab systemic exposure. The efficacy of this nanosystem was next evaluated in a validated orthotopic GBM nude mice model, studying the tumor growth over time by bioluminescence and the anti-angiogenic effects. After 14 days, bevacizumab-loaded PLGA NP demonstrated a reduction in the tumor growth accompanied by a higher anti-angiogenic effect compared to the free bevacizumab. These results can be explained by the fact that bevacizumab was found in the brain just for bevacizumab-loaded PLGA NP group, after 14 days of formulation administration. Therefore, we believe that our strategy would be an efficient alternative to improve GBM treatment with high impact for patient life quality and survival.

Boosting often overlooked long wavelength emissions of rare-earth nanoparticles for NIR-II fluorescence imaging of orthotopic glioblastoma

Rare-earth nanoparticles (RE NPs) with narrow long wavelength emissions have been recently investigated for their potential application for fluorescence imaging in the second near-infrared window (NIR-II). Previously these RE NPs have a very limited application in the diagnosis and treatment of deep-seated tumors such as brain tumors, due to their weak fluorescence in the range of 1300-1700 nm. Herein, we report a significant enhancement of more than 10 times regular emission of NaNdF₄ nanoparticles at 1340 nm wavelength by coating them with an inert layer of NaLuF₄, followed by sensitizing with a near-infrared dye (IR-808). We deliver these highly bright nanoparticles into the brain by using focused ultrasound to temporarily open the blood-brain barrier (BBB), and then detect the orthotopic glioblastoma by fluorescence imaging at 1340 nm. The images obtained from long wavelength fluorescence (i.e. 1340 nm) exhibited better resolution and contrast compared to the short wavelength fluorescence (i.e. 1060 nm). Our study not only provides insights for enhancing often overlooked emissions of rare-earth nanoparticles for NIR-II fluorescence imaging of deep-seated tumors, but also demonstrates great potential of focused ultrasound based technology in delivering nanotheranostic agents.

Genome-wide identification of lncRNAs as novel prognosis biomarkers of glioma

BACKGROUND

Glioma is the primary cancer of the central nervous system, and defining the prognosis of glioma is of great significance in the clinical. The long noncoding RNAs (lncRNAs) emerge as important regulators of pathological processes. This study aimed to identify lncRNAs which could function as potential prognosis biomarkers of glioma.

MATERIAL AND METHODS

Glioma RNA-seq data from TCGA and CGGA were analyzed to identify neoplasm grade associated lncRNAs by DEseq. 2R and weighted gene co-expression network analysis. Consensus module genes were analyzed in Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway to predict lncRNAs biological functions. Then neutrophil immune estimations were analyzed by Tumor Immune Estimation Resource. Transcrption factors of these lncRNAs were predicted by PROMO. Overall survival and receiver operating characteristic (ROC) analyses were applied to test the accuracy of predicted lncRNAs as the markers of prognosis.

RESULTS

We identified four lncRNAs most correlated with both higher neoplasm grade and worse prognosis, including AC064875.2, HOTAIRM1, LINC00908, and RP11-84A19.3. Neutrophil-mediated immunity and cell adhesion junction were considered as the main biological functions of these lncRNAs. In addition, the correlation of these four lncRNAs with glioma prognosis was validated.

CONCLUSION

Neutrophil immune infiltration is implicated in higher neoplasm grade and worse prognosis of glioma. AC064875.2, HOTAIRM1, LINC00908, and RP11-84A19.3 may serve as potential prognosis biomarkers of glioma.

Arming oHSV with ULBP3 drives abscopal immunity in lymphocyte-depleted glioblastoma

Oncolytic viruses induce local tumor destruction and inflammation. Whether virotherapy can also overcome immunosuppression in noninfected tumor areas is under debate. To address this question, we have explored immunologic effects of oncolytic herpes simplex viruses (oHSVs) in a genetically engineered mouse model of isocitrate dehydrogenase (IDH) wild-type glioblastoma, the most common and most malignant primary brain tumor in adults. Our model recapitulates the genomics, the diffuse infiltrative growth pattern, and the extensive macrophage-dominant immunosuppression of human glioblastoma. Infection with an oHSV that was armed with a UL16-binding protein 3 (ULBP3) expression cassette inhibited distant tumor growth in the absence of viral spreading (abscopal effect) and yielded accumulation of activated macrophages and T cells. There was also abscopal synergism of oHSVULBP3 with anti-programmed cell death 1 (anti-PD-1) against distant, uninfected tumor areas; albeit consistent with clinical trials in patients with glioblastoma, monotherapy with anti-PD-1 was ineffective in our model. Arming oHSV with ULBP3 led to upregulation of antigen processing and presentation gene sets in myeloid cells. The cognate ULBP3 receptor NKG2D, however, is not present on myeloid cells, suggesting a noncanonical mechanism of action of ULBP3. Overall, the myeloid-dominant, anti-PD-1-sensitive abscopal effect of oHSVULBP3 warrants further investigation in patients with IDH wild-type glioblastoma.

Current and Future Imaging Methods for Evaluating Response to Immunotherapy in Neuro-Oncology

Imaging plays a central role in evaluating responses to therapy in neuro-oncology patients. The advancing clinical use of immunotherapies has demonstrated that treatment-related inflammatory responses mimic tumor growth via conventional imaging, thus spurring the development of new imaging approaches to adequately distinguish between pseudoprogression and progressive disease. To this end, an increasing number of advanced imaging techniques are being evaluated in preclinical and clinical studies. These novel molecular imaging approaches will serve to complement conventional response assessments during immunotherapy. The goal of these techniques is to provide definitive metrics of tumor response at earlier time points to inform treatment decisions, which has the potential to improve patient outcomes. This review summarizes the available immunotherapy regimens, clinical response criteria, current state-of-the-art imaging approaches, and groundbreaking strategies for future implementation to evaluate the anti-tumor and immune responses to immunotherapy in neuro-oncology applications.

Immunologic Profiling of Mutational and Transcriptional Subgroups in Pediatric and Adult High-Grade Gliomas

Immunologic treatment strategies are under investigation for high-grade gliomas. Determining relevant immunologic pathways is required for invigorating a tumor-specific immune response. We therefore investigated the immunologic phenotypes within different subgroups of high-grade gliomas, with a focus on rare genetic subgroups of pediatric and adolescent patients to identify potentially targetable mechanisms. We gathered published gene-expression data from 1,135 high-grade glioma patients and applied a machine-learning technique to determine their transcriptional (mesenchymal, classic, neural, and proneural) and mutational [K27, G34, IDH, and wild type (WT)] subtypes. Gene signatures of infiltrating immune cells and functional immune pathways were evaluated in correlation to histologic diagnosis, age, and transcriptional and mutational subgroups. Our analysis identified four distinct microenvironmental signatures of immune cell infiltration (immune 1-4), which can be stratified into vascular, monocytic/stromal, monocytic/T-cell-, and antigen-presenting cell (APC)/natural killer (NK) cell/T-cell-dominated immune clusters. Immune cell expression profiles correlated with transcriptional and mutational subgroups but were independent of age and histologic diagnosis. By including functional pathways and correlating the expression of immunostimulatory and -inhibitory receptor-ligand interactions, we were able to define the immunologic microenvironment and identify possible immunologic subtypes associated with poor prognosis. In addition, comparison of overall survival with the immunologic landscape and with checkpoint molecules revealed correlations within the transcriptional and mutational subgroups, highlighting the potential application of PD-1/PD-L1 checkpoint inhibition in K27-mutated tumors. Our study shows that transcriptional and mutational subgroups are characterized by distinct immunologic tumor microenvironments, demonstrating the immunologic heterogeneity within high-grade gliomas and suggesting an immune-specific stratification for upcoming immunotherapy trials.

Clinicopathological implications of TIM3+ tumor-infiltrating lymphocytes and the miR-455-5p/Galectin-9 axis in skull base chordoma patients

Chordoma is difficult to eradicate due to high local recurrence rates. The immune microenvironment is closely associated with tumor prognosis; however, its role in skull base chordoma is unknown. The expression of Galectin-9 (Gal9) and tumor-infiltrating lymphocyte (TIL) markers was assessed by immunohistochemistry. Kaplan-Meier and multivariate Cox analyses were used to assessing local recurrence-free survival (LRFS) and overall survival (OS) of patients. MiR-455-5p was identified as a regulator of Gal9 expression. Immunopositivity for Gal9 was associated with tumor invasion (p = 0.019), Karnofsky performance status (KPS) score (p = 0.017), and total TIL count (p < 0.001); downregulation of miR-455-5p was correlated with tumor invasion (p = 0.017) and poor prognosis; and the T-cell immunoglobulin and mucin-domain 3 (TIM3)+ TIL count was associated with chordoma invasion (p = 0.010) and KPS score (p = 0.037). Furthermore, multivariate analysis indicated that only TIM3+ TIL density was an independent prognostic factor for LRFS (p = 0.010) and OS (p = 0.016). These results can be used to predict clinical outcome and provide a basis for immune therapy in skull base chordoma patients.

Symbiotic Macrophage-Glioma Cell Interactions Reveal Synthetic Lethality in PTEN-Null Glioma

Heterotypic interactions across diverse cell types can enable tumor progression and hold the potential to expand therapeutic interventions. Here, combined profiling and functional studies of glioma cells in glioblastoma multiforme (GBM) models establish that PTEN deficiency activates YAP1, which directly upregulates lysyl oxidase (LOX) expression. Mechanistically, secreted LOX functions as a potent macrophage chemoattractant via activation of the β1 integrin-PYK2 pathway in macrophages. These infiltrating macrophages secrete SPP1, which sustains glioma cell survival and stimulates angiogenesis. In PTEN-null GBM models, LOX inhibition markedly suppresses macrophage infiltration and tumor progression. Correspondingly, YAP1-LOX and β1 integrin-SPP1 signaling correlates positively with higher macrophage density and lower overall survival in GBM patients. This symbiotic glioma-macrophage interplay provides therapeutic targets specifically for PTEN-deficient GBM.