Search

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

T cells are critical effectors of cancer immunotherapies, but little is known about their gene expression programs in diffuse gliomas. Here, we leverage single-cell RNA sequencing (RNA-seq) to chart the gene expression and clonal landscape of tumor-infiltrating T cells across 31 patients with isocitrate dehydrogenase (IDH) wild-type glioblastoma and IDH mutant glioma. We identify potential effectors of anti-tumor immunity in subsets of T cells that co-express cytotoxic programs and several natural killer (NK) cell genes. Analysis of clonally expanded tumor-infiltrating T cells further identifies the NK gene KLRB1 (encoding CD161) as a candidate inhibitory receptor. Accordingly, genetic inactivation of KLRB1 or antibody-mediated CD161 blockade enhances T cell-mediated killing of glioma cells in vitro and their anti-tumor function in vivo. KLRB1 and its associated transcriptional program are also expressed by substantial T cell populations in other human cancers. Our work provides an atlas of T cells in gliomas and highlights CD161 and other NK cell receptors as immunotherapy targets.

Glioblastomas are the most common form of malignant primary brain tumor and an important cause of morbidity and mortality. In recent years there have been important advances in understanding the molecular pathogenesis and biology of these tumors, but this has not translated into significantly improved outcomes for patients. In this consensus review from the Society for Neuro-Oncology (SNO) and the European Association of Neuro-Oncology (EANO), the current management of isocitrate dehydrogenase wildtype (IDHwt) glioblastomas will be discussed. In addition, novel therapies such as targeted molecular therapies, agents targeting DNA damage response and metabolism, immunotherapies, and viral therapies will be reviewed, as well as the current challenges and future directions for research.

BackgroundRNAs within extracellular vesicles (EVs) have potential as diagnostic biomarkers for patients with cancer and are identified in a variety of biofluids. Glioblastomas (GBMs) release EVs containing RNA into cerebrospinal fluid (CSF). Here we describe a multi-institutional study of RNA extracted from CSF-derived EVs of GBM patients to detect the presence of tumor-associated amplifications and mutations in epidermal growth factor receptor (EGFR).MethodsCSF and matching tumor tissue were obtained from patients undergoing resection of GBMs. We determined wild-type (wt)EGFR DNA copy number amplification, as well as wtEGFR and EGFR variant (v)III RNA expression in tumor samples. We also characterized wtEGFR and EGFRvIII RNA expression in CSF-derived EVs.ResultsEGFRvIII-positive tumors had significantly greater wtEGFR DNA amplification (P = 0.02) and RNA expression (P = 0.03), and EGFRvIII-positive CSF-derived EVs had significantly more wtEGFR RNA expression (P = 0.004). EGFRvIII was detected in CSF-derived EVs for 14 of the 23 EGFRvIII tissue-positive GBM patients. Conversely, only one of the 48 EGFRvIII tissue-negative patients had the EGFRvIII mutation detected in their CSF-derived EVs. These results yield a sensitivity of 61% and a specificity of 98% for the utility of CSF-derived EVs to detect an EGFRvIII-positive GBM.ConclusionOur results demonstrate CSF-derived EVs contain RNA signatures reflective of the underlying molecular genetic status of GBMs in terms of wtEGFR expression and EGFRvIII status. The high specificity of the CSF-derived EV diagnostic test gives us an accurate determination of positive EGFRvIII tumor status and is essentially a less invasive "liquid biopsy" that might direct mutation-specific therapies for GBMs.

This workshop addressed challenges of clinical research in neurosurgery. Randomized controlled clinical trials (RCTs) have high internal validity, but often insufficiently generalize to real-world practice. Observational studies are inclusive but often lack sufficient rigor. The workshop considered possible solutions, such as (1) statistical methods for demonstrating causality using observational data; (2) characteristics required of a registry supporting effectiveness research; (3) trial designs combining advantages of observational studies and RCTs; and (4) equipoise, an identified challenge for RCTs. In the future, advances in information technology potentially could lead to creation of a massive database where clinical data from all neurosurgeons are integrated and analyzed, ending the separation of clinical research and practice and leading to a new "science of practice."

Cytomegalovirus (CMV) has been implicated in glioblastoma (GBM); however, a mechanistic connection in vivo has not been established. The purpose of this study is to characterize the effects of murine CMV (MCMV) on GBM growth in murine models. Syngeneic GBM models were established in mice perinatally infected with MCMV. We found that tumor growth was markedly enhanced in [MCMV.sup.+] mice, with a significant reduction in overall survival compared with that of controls (P < 0.001). We observed increased angiogenesis and tumor blood flow in [MCMV.sup.+] mice. MCMV reactivation was observed in intratumoral perivascular pericytes and tumor cells in mouse and human GBM specimens, and pericyte coverage of tumor vasculature was strikingly augmented in [MCMV.sup.+] mice. We identified PDGF-D as a CMV-induced factor essential for pericyte recruitment, angiogenesis, and tumor growth. The antiviral drug cidofovir improved survival in [MCMV.sup.+] mice, inhibiting MCMV reactivation, PDGF-D expression, pericyte recruitment, and tumor angiogenesis. These data show that MCMV potentiates GBM growth in vivo by increased pericyte recruitment and angiogenesis due to alterations in the secretome of CMV-infected cells. Our model provides evidence for a role of CMV in GBM growth and supports the application of antiviral approaches for GBM therapy., Introduction Glioblastoma (GBM) is the most common malignant brain tumor, with approximately 10,000 new cases per year in the US. There is no effective treatment, and patient survival remains dismal [...]

Although histopathological diagnosis is essential in decision of therapeutic strategy for gliomas, sometimes the tumors diagnosed in one histological entity show thoroughly different clinical courses. This phenomenon is believed to be due primarily to the presence of the genetic subgroup. In fact, relationship between treatment response and certain genetic characteristics is indicated (e.g. better chemosensitivity in glioma with losses of 1p/19q (−1p/19q)). It is highly likely that genetic classification of glioma is useful to select the adjuvant treatment. Additionally, gain of 7q (+7q) and −1p/19q are early events in 2 distinct tumor lineages, astrocytic tumors and oligodendroglial tumors, respectively, and these tumors obtain additional genetic aberration (−9p, 10q) with tumor progression. On the other hand, concerning the tumors without +7q or −1p/19q, little is known about clinically important genetic aberration. Therefore the study on such tumors could provide useful information for the prognosis prediction and the determination of treatment strategy. METHODS: We selected 39 cases of gliomas without +7q or −1p/19q from 200 adult supratentorial glioma cases surgically treated and analyzed chromosomal DNA copy number aberrations (CNAs) by comparative genomic hybridization (CGH) from 2005 to 2012. We correlated clinical features of these tumors with histological characteristics, CNAs and IDH1 status. RESULTS: The clinical course of gliomas without +7q or −1p/19q was not correlated with additional genetic aberration of -9p or 10q, which have been known as genetic markers for poor prognosis, and absence of +7q or −1p/19q was maintained at the time of recurrence. The tumors without +7q or −1p/19q showed relatively favorable prognosis although mutation of IDH1 was infrequent in these tumors (35.8 %). CONCLUSION: The gliomas without +7q or −1p/19q have clinical features distinct from the +7q and −1p/19q gliomas. Prognostic markers for each subgroups could help establish therapeutic strategy against the tumor. DNA methylation is a mechanism altering the normal state of cells implicated in many cancers. Currently the methylation status of MGMT is one of the most widely utilized clinical genetic tests performed on glioblastoma multiforme (GBM). While several global gene expression signatures have been developed, it is unclear if genome-wide DNA methylation signatures can predict prognosis in cancer. We used a computational algorithm (MethylMix) to analyze genome-wide DNA methylation in GBM data obtained from The Cancer Genome Atlas (TCGA). MethylMix identified a set of driver genes that met criteria for being both differential and functional. Differential refers to a difference in cancer methylation compared to normal tissue; functional refers to having a significant correlation with matched gene expression changes. We then used these MethylMix driver genes to build multivariate models of overall survival using linear regression and validated these models in independent data sets. Applying MethylMix and linear regression we identified a novel methylation signature predictive of overall survival, which we here define as the GLIOMETH signature. Interestingly, GLIOMETH did not include MGMT, suggesting that MGMT methylation is not essential to predict prognosis in GBM. GLIOMETH was prognostically significant even in a multivariate analysis with known prognostic covariates, including MGMT methylation. We validated GLIOMETH in two external DNA methylation data sets and two gene expression data sets, using a leveraging technique predicting methylation in terms of gene expression, showing also a significant survival correlation. Differential and functional DNA methylation is predictive of overall survival in GBM independent of known prognostic factors. We identified GLIOMETH as a DNA methylation signature that is predictive of overall survival in GBM, outperforming MGMT methylation. The GLIOMETH model validated across multiple independent DNA methylation and gene expression validation data sets demonstrating its robustness as an independent predictor of prognosis in GBM. Recent next-generation genomic studies of medulloblastoma have revealed an unexpected and overwhelming convergence of somatic alterations affecting chromatin-modifying genes. Estimates informed by next-generation sequencing implicate that at least one third of all medulloblastomas have somatic mutations in a chromatin modifier, including those targeting histone methyltransfereses, histone demethylases, and related chromatin modulators that collectively function to influence chromatin conformation associated gene expression states. These mutations occur across all four medulloblastoma subgroups although different sets of genes appear to be selectively altered in a subgroup-specific manner. Despite the abundance of evidence implicating deregulation of chromatin modifiers as a key event in medulloblastoma pathogenesis, the medulloblastoma epigenome remains largely unexplored, and studies cataloguing histone modification states on a genome-wide scale have yet to be reported. To comprehensively investigate the histone code in medulloblastoma and the consequences associated with mutations affecting histone-modifying genes, we have performed ChIP-sequencing on a set of well-characterized primary medulloblastoma specimens. Histone marks examined in this study include the six modifications mandated by the International Human Epigenome Consortium (IHEC), including H3K4me3, H3K9me3, H3K27me3, H3K27ac, H3K4me1 and H3K36me3. Chromatin isolates from primary fresh-frozen tissues representative of each medulloblastoma subgroup were immunoprecipitated with the indicated antibodies and sequenced with a HiSeq Illumina sequencer to obtain at least 10 million unique reads per ChIP experiment. Peak calling was performed using multiple publicly available tools and data integrated with existing ENCODE data for the same histone marks. Inter-subgroup comparisons of histone modification states revealed a wealth of distinguishing genomic regions that were highly correlated with alternative patterns of gene expression existing between the subgroups. Moreover, integration with existing mutational profiles demonstrated aberrant chromatin states that could be linked to underlying mutations in select chromatin modifiers. Ongoing work will focus on expanding the cohort and integration with all levels of ‘omic data.

Proteins are densely packed in cells and tissues, where they form complex nanostructures. Expansion microscopy (ExM) variants have been used to separate proteins from each other in preserved biospecimens, improving antibody access to epitopes. Here, we present an ExM variant, decrowding expansion pathology (dExPath), that can expand proteins away from each other in human brain pathology specimens, including formalin-fixed paraffin-embedded (FFPE) clinical specimens. Immunostaining of dExPath-expanded specimens reveals, with nanoscale precision, previously unobserved cellular structures, as well as more continuous patterns of staining. This enhanced molecular staining results in observation of previously invisible disease marker–positive cell populations in human glioma specimens, with potential implications for tumor aggressiveness. dExPath results in improved fluorescence signals even as it eliminates lipofuscin-associated autofluorescence. Thus, this form of expansion-mediated protein decrowding may, through improved epitope access for antibodies, render immunohistochemistry more powerful in clinical science and, perhaps, diagnosis. Editor's summary: Expansion microscopy allows to image structures sized below the diffraction limit of light by physical expansion of biological specimens before imaging. Here, Valdes and colleagues developed decrowding expansion pathology (dExPath), a variant of expansion microscopy, that improved antibody access of epitopes during post-expansion staining. Used in mouse and fixed human brain pathology specimens, dExPath revealed cells and structures not detected with standard expansion microscopy or super-resolved structured illumination microscopy. This iteration of expansion microscopy could therefore be a useful tool for basic research and neuropathology. —Daniela Neuhofer [ABSTRACT FROM AUTHOR]

Background: The GL261 and CT2A syngeneic tumor lines are frequently used as immunocompetent orthotopic mouse models of human glioblastoma (huGBM) but demonstrate distinct differences in their responses to immunotherapy. Methods: To decipher the cell-intrinsic mechanisms that drive immunotherapy resistance in CT2A-luc and to define the aspects of human cancer biology that these lines can best model, we systematically compared their characteristics using whole exome and transcriptome sequencing, and protein analysis through immunohistochemistry, Western blot, flow cytometry, immunopeptidomics, and phosphopeptidomics. Results: The transcriptional profiles of GL261-luc2 and CT2A-luc tumors resembled those of some huGBMs, despite neither line sharing the essential genetic or histologic features of huGBM. Both models exhibited striking hypermutation, with clonal hotspot mutations in RAS genes (Kras p.G12C in GL261-luc2 and Nras p.Q61L in CT2A-luc). CT2A-luc distinctly displayed mesenchymal differentiation, upregulated angiogenesis, and multiple defects in antigen presentation machinery (e.g. Tap1 p.Y488C and Psmb8 p.A275P mutations) and interferon response pathways (e.g. copy number losses of loci including IFN genes and reduced phosphorylation of JAK/STAT pathway members). The defect in MHC class I expression could be overcome in CT2Aluc by interferon-g treatment, which may underlie the modest efficacy of some immunotherapy combinations. Additionally, CT2A-luc demonstrated substantial baseline secretion of the CCL-2, CCL-5, and CCL-22 chemokines, which play important roles as myeloid chemoattractants. Conclusion: Although the clinical contexts that can be modeled by GL261 and CT2A for huGBM are limited, CT2A may be an informative model of immunotherapy resistance due to its deficits in antigen presentation machinery and interferon response pathways. [ABSTRACT FROM AUTHOR]

The lack of reliable predictive biomarkers to guide effective therapy is a major obstacle to the advancement of therapy for high-grade gliomas, particularly glioblastoma (GBM), one of the few cancers whose prognosis has not improved over the past several decades. With this pilot clinical trial (number NCT04135807), we provide first-in-human evidence that drug-releasing intratumoral microdevices (IMDs) can be safely and effectively used to obtain patient-specific, high-throughput molecular and histopathological drug response profiling. These data can complement other strategies to inform the selection of drugs based on their observed antitumor effect in situ. IMDs are integrated into surgical practice during tumor resection and remain in situ only for the duration of the otherwise standard operation (2 to 3 hours). None of the six enrolled patients experienced adverse events related to the IMD, and the exposed tissue was usable for downstream analysis for 11 out of 12 retrieved specimens. Analysis of the specimens provided preliminary evidence of the robustness of the readout, compatibility with a wide array of techniques for molecular tissue interrogation, and promising similarities with the available observed clinical-radiological responses to temozolomide. From an investigational aspect, the amount of information obtained with IMDs allows characterization of tissue effects of any drugs of interest, within the physiological context of the intact tumor, and without affecting the standard surgical workflow. Editor's summary: Patients with high grade gliomas (HGG) and particularly glioblastoma (GBM) have poor overall survival and lack predictive biomarkers to guide therapeutic treatment. To overcome this, Peruzzi et al. have developed intratumoral microdevices (IMD) to be inserted and removed during surgery that release drugs, resected tissue can then be evaluated for efficacy that reflects systemic treatment efficacy. This was tested in six patients (NCT04135807) and found to be safe, and tissue was usable for downstream analysis with implications to replicating responses to temozolomide. This device requires additional testing in patients but represents a promising strategy to help guide treatment of HGG and improve treatment outcomes. —Dorothy Hallberg [ABSTRACT FROM AUTHOR]

Transcriptional signatures and immune cell infiltrates associated with immune activation distinguish patients with glioblastoma who initially respond to immune checkpoint blockade from those who do not., Author(s): Hirotaka Ito [sup.1] , Hiroshi Nakashima [sup.1] , E. Antonio Chiocca [sup.1] Author Affiliations: (1) Harvey Cushing Neuro-oncology Laboratories, Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, [...]

Oncolytic viral (OV) therapy, which uses genetically engineered tumor-targeting viruses, is being increasingly used in cancer clinical trials due to the direct cytolytic effects of this treatment that appear to provoke a robust immune response against the tumor. As OVs enter tumor cells, intrinsic host defenses have the potential to hinder viral replication and spread within the tumor mass. In this report, we show that histone deacetylase 6 (HDAC6) in tumor cells appears to alter the trafficking of postentry OVs from the nucleus toward lysosomes. In glioma cell lines and glioma-stem-like cells, HDAC6 inhibition (HDAC6i) by either pharmacologic or genetic means substantially increased replication of oncolytic herpes simplex virus type 1 (oHSV). Moreover, HDAC6i increased shuttling of post-entry oHSV to the nucleus. In addition, electron microscopic analysis revealed that post-entry oHSVs are preferentially taken up into glioma cells through the endosomal pathway rather than via fusion at the cell surface. Together, these findings illustrate a mechanism of glioma cell defense against an incoming infection by oHSV and identify possible approaches to enhance oHSV replication and subsequent lysis of tumor cells., Introduction Malignant gliomas (such as glioblastoma [GBM]) remain formidable cancers based on their poor prognosis, with a median survivorship of 15 months or less, extensive neurologic morbidity, and cost of [...]