Publications by authors named "Pedro Lowenstein"

168 Publications

Transbronchial biopsies' histopathological findings leading to successful late steroid therapy in Covid-19 acute respiratory failure.

Virchows Arch 2021 Jan 7. Epub 2021 Jan 7.

Department of Lung Diseases, Favaloro Foundation University Hospital, Buenos Aires, Argentina.

We present results from clinical, radiologic, gas exchange, lung mechanics, and fibre-optic bronchoscopy-guided transbronchial biopsies in a case of acute respiratory failure due to SARS-CoV-2 (Covid-19). This report highlights the pulmonary, immunological, and inflammatory changes found during acute diffuse alveolar damage and the later organizing phase. An early diffuse alveolar damage pattern with predominant epithelial involvement with active recruitment of T cells and monocytes was observed followed by a late organizing pattern with pneumocyte hyperplasia, inflammatory infiltration, prominent endotheliitis, and secondary germinal centers. The patient's deterioration paralleling the late immuno-pathological findings based the decision to administer intravenous corticosteroids, resulting in clinical, gasometric, and radiologic improvement. We believe that real-time clinicopathological correlation, along with the description of the immunological processes at play, will contribute to the full clinical picture of Covid-19 and might lead to a more rational approach in the precise timing of anti-inflammatory, anti-cytokine, or steroid therapies.
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http://dx.doi.org/10.1007/s00428-020-02975-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7789084PMC
January 2021

Immune-stimulatory (TK/Flt3L) gene therapy opens the door to a promising new treatment strategy against brainstem gliomas.

Oncotarget 2020 Dec 15;11(50):4607-4612. Epub 2020 Dec 15.

Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI 48109, USA.

Diffuse intrinsic pontine glioma (DIPG) is a rare brainstem tumor which carries a dismal prognosis. To date. there are no effective treatments for DIPG. Transcriptomic studies have shown that DIPGs have a distinct profile compared to hemispheric high-grade pediatric gliomas. These specific genomic features coupled with the younger median age group suggest that DIPG is of developmental origin. There is a major unmet need for novel effective therapeutic approaches for DIPG. Clinical and preclinical studies have expanded our understanding of the molecular pathways in this deadly disease. We have developed a genetically engineered brainstem glioma model harboring the recurrent DIPG mutation, activin A receptor type I (ACVR1)-G328V (mACVR1) using the sleeping beauty transposon system. DIPG neurospheres isolated from the genetically engineered mouse model were implanted into the pons of immune-competent mice to assess the therapeutic efficacy and toxicity of immunostimulatory gene therapy using adenoviruses expressing thymidine kinase (TK) and fms-like tyrosine kinase 3 ligand (Flt3L). Immunostimulatory adenoviral-mediated delivery of TK/Flt3L in mice bearing brainstem gliomas resulted in antitumor immunity, recruitment of antitumor-specific T cells, and improved median survival by stimulating the host antitumor immune response. Therapeutic efficacy of the immunostimulatory gene therapy strategy will be tested in the clinical arena in a Phase I clinical trial. We also discuss immunotherapeutic interventions currently being implemented in DIPG patients and discuss the profound therapeutic implications of immunotherapy for this patient populations.
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http://dx.doi.org/10.18632/oncotarget.27834DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7747859PMC
December 2020

Genetically Engineered Mouse Model of Brainstem High-Grade Glioma.

STAR Protoc 2020 Dec 25;1(3):100165. Epub 2020 Nov 25.

Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI 48109, USA.

Brainstem gliomas are aggressive tumors that are more prevalent in pediatric patients. The location of these tumors makes them inoperable, and currently there is no effective treatment. Recent genomic data revealed the unique biology of these tumors. The following protocol provides a method to incorporate these specific genetic lesions in a mouse glioma model. Using this model, the effects of these mutations in tumor progression and response to treatments can be studied within a relevant context. For complete details on the use and execution of this protocol, please refer to Mendez et al. (2020).
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http://dx.doi.org/10.1016/j.xpro.2020.100165DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7757359PMC
December 2020

Hemispherical Pediatric High-Grade Glioma: Molecular Basis and Therapeutic Opportunities.

Int J Mol Sci 2020 Dec 17;21(24). Epub 2020 Dec 17.

Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI 48109, USA.

In this review, we discuss the molecular characteristics, development, evolution, and therapeutic perspectives for pediatric high-grade glioma (pHGG) arising in cerebral hemispheres. Recently, the understanding of biology of pHGG experienced a revolution with discoveries arising from genomic and epigenomic high-throughput profiling techniques. These findings led to identification of prevalent molecular alterations in pHGG and revealed a strong connection between epigenetic dysregulation and pHGG development. Although we are only beginning to unravel the molecular biology underlying pHGG, there is a desperate need to develop therapies that would improve the outcome of pHGG patients, as current therapies do not elicit significant improvement in median survival for this patient population. We explore the molecular and cell biology and clinical state-of-the-art of pediatric high-grade gliomas (pHGGs) arising in cerebral hemispheres. We discuss the role of driving mutations, with a special consideration of the role of epigenetic-disrupting mutations. We will also discuss the possibilities of targeting unique molecular vulnerabilities of hemispherical pHGG to design innovative tailored therapies.
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http://dx.doi.org/10.3390/ijms21249654DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7766684PMC
December 2020

Inhibition of 2-hydroxyglutarate elicits metabolic reprogramming and mutant IDH1 glioma immunity in mice.

J Clin Invest 2021 Feb;131(4)

Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, Michigan, USA.

Mutant isocitrate dehydrogenase 1 (IDH1-R132H; mIDH1) is a hallmark of adult gliomas. Lower grade mIDH1 gliomas are classified into 2 molecular subgroups: 1p/19q codeletion/TERT-promoter mutations or inactivating mutations in α-thalassemia/mental retardation syndrome X-linked (ATRX) and TP53. This work focuses on glioma subtypes harboring mIDH1, TP53, and ATRX inactivation. IDH1-R132H is a gain-of-function mutation that converts α-ketoglutarate into 2-hydroxyglutarate (D-2HG). The role of D-2HG within the tumor microenvironment of mIDH1/mATRX/mTP53 gliomas remains unexplored. Inhibition of D-2HG, when used as monotherapy or in combination with radiation and temozolomide (IR/TMZ), led to increased median survival (MS) of mIDH1 glioma-bearing mice. Also, D-2HG inhibition elicited anti-mIDH1 glioma immunological memory. In response to D-2HG inhibition, PD-L1 expression levels on mIDH1-glioma cells increased to similar levels as observed in WT-IDH gliomas. Thus, we combined D-2HG inhibition/IR/TMZ with anti-PDL1 immune checkpoint blockade and observed complete tumor regression in 60% of mIDH1 glioma-bearing mice. This combination strategy reduced T cell exhaustion and favored the generation of memory CD8+ T cells. Our findings demonstrate that metabolic reprogramming elicits anti-mIDH1 glioma immunity, leading to increased MS and immunological memory. Our preclinical data support the testing of IDH-R132H inhibitors in combination with IR/TMZ and anti-PDL1 as targeted therapy for mIDH1/mATRX/mTP53 glioma patients.
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http://dx.doi.org/10.1172/JCI139542DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7880418PMC
February 2021

Systemic brain tumor delivery of synthetic protein nanoparticles for glioblastoma therapy.

Nat Commun 2020 11 10;11(1):5687. Epub 2020 Nov 10.

Biointerfaces Institute, University of Michigan, 2800 Plymouth Road, Ann Arbor, MI, 48109, USA.

Glioblastoma (GBM), the most aggressive form of brain cancer, has witnessed very little clinical progress over the last decades, in part, due to the absence of effective drug delivery strategies. Intravenous injection is the least invasive drug delivery route to the brain, but has been severely limited by the blood-brain barrier (BBB). Inspired by the capacity of natural proteins and viral particulates to cross the BBB, we engineered a synthetic protein nanoparticle (SPNP) based on polymerized human serum albumin (HSA) equipped with the cell-penetrating peptide iRGD. SPNPs containing siRNA against Signal Transducer and Activation of Transcription 3 factor (STAT3i) result in in vitro and in vivo downregulation of STAT3, a central hub associated with GBM progression. When combined with the standard of care, ionized radiation, STAT3i SPNPs result in tumor regression and long-term survival in 87.5% of GBM-bearing mice and prime the immune system to develop anti-GBM immunological memory.
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http://dx.doi.org/10.1038/s41467-020-19225-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7655867PMC
November 2020

An Optimized Protocol for In Vivo Analysis of Tumor Cell Division in a Sleeping Beauty-Mediated Mouse Glioma Model.

STAR Protoc 2020 Sep 6;1(2). Epub 2020 Jun 6.

Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI 48109, USA.

Malignant gliomas are the most common and aggressive primary brain tumor in adults, and high mitotic rates are associated with their malignancy. Gliomas were modeled in mice using the Sleeping Beauty system to encode genetic lesions recapitulating the human disease. The presented workflow allows the study of the proliferation of glioma cells , enabling the identification of different phases of the cell cycle, with the advantage that 5-ethynyl-2'-deoxyuridine staining does not involve denaturation steps and samples do not require histological processing. For complete details on the use and execution of this protocol, please refer to Núñez et al. (2019).
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http://dx.doi.org/10.1016/j.xpro.2020.100044DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7518519PMC
September 2020

Glioblastoma Utilizes Fatty Acids and Ketone Bodies for Growth Allowing Progression during Ketogenic Diet Therapy.

iScience 2020 Aug 13;23(9):101453. Epub 2020 Aug 13.

Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA; Department of Psychiatry and Biobehavioral Sciences and Semel Institute for Neuroscience & Human Behavior, UCLA, Los Angeles, CA, USA; Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, CA, USA; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, UCLA, Los Angeles, CA, USA. Electronic address:

Glioblastoma (GBM) metabolism has traditionally been characterized by a primary dependence on aerobic glycolysis, prompting the use of the ketogenic diet (KD) as a potential therapy. In this study we evaluated the effectiveness of the KD in GBM and assessed the role of fatty acid oxidation (FAO) in promoting GBM propagation. In vitro assays revealed FA utilization throughout the GBM metabolome and growth inhibition in nearly every cell line in a broad spectrum of patient-derived glioma cells treated with FAO inhibitors. In vivo assessments revealed that knockdown of carnitine palmitoyltransferase 1A (CPT1A), the rate-limiting enzyme for FAO, reduced the rate of tumor growth and increased survival. However, the unrestricted ketogenic diet did not reduce tumor growth and for some models significantly reduced survival. Altogether, these data highlight important roles for FA and ketone body metabolism that could serve to improve targeted therapies in GBM.
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http://dx.doi.org/10.1016/j.isci.2020.101453DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7471621PMC
August 2020

Purine metabolism regulates DNA repair and therapy resistance in glioblastoma.

Nat Commun 2020 07 30;11(1):3811. Epub 2020 Jul 30.

Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 48109, USA.

Intratumoral genomic heterogeneity in glioblastoma (GBM) is a barrier to overcoming therapy resistance. Treatments that are effective independent of genotype are urgently needed. By correlating intracellular metabolite levels with radiation resistance across dozens of genomically-distinct models of GBM, we find that purine metabolites, especially guanylates, strongly correlate with radiation resistance. Inhibiting GTP synthesis radiosensitizes GBM cells and patient-derived neurospheres by impairing DNA repair. Likewise, administration of exogenous purine nucleosides protects sensitive GBM models from radiation by promoting DNA repair. Neither modulating pyrimidine metabolism nor purine salvage has similar effects. An FDA-approved inhibitor of GTP synthesis potentiates the effects of radiation in flank and orthotopic patient-derived xenograft models of GBM. High expression of the rate-limiting enzyme of de novo GTP synthesis is associated with shorter survival in GBM patients. These findings indicate that inhibiting purine synthesis may be a promising strategy to overcome therapy resistance in this genomically heterogeneous disease.
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http://dx.doi.org/10.1038/s41467-020-17512-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7393131PMC
July 2020

Tumor mutational burden predicts survival in patients with low-grade gliomas expressing mutated IDH1.

Neurooncol Adv 2020 Jan-Dec;2(1):vdaa042. Epub 2020 Mar 27.

Department of Neurosurgery, University of Michigan Medical School, MSRB II, Ann Arbor, Michigan, USA.

Background: Gliomas are the most common primary brain tumors. High-Grade Gliomas have a median survival (MS) of 18 months, while Low-Grade Gliomas (LGGs) have an MS of approximately 7.3 years. Seventy-six percent of patients with LGG express mutated isocitrate dehydrogenase (mIDH) enzyme. Survival of these patients ranges from 1 to 15 years, and tumor mutational burden ranges from 0.28 to 3.85 somatic mutations/megabase per tumor. We tested the hypothesis that the tumor mutational burden would predict the survival of patients with tumors bearing mIDH.

Methods: We analyzed the effect of tumor mutational burden on patients' survival using clinical and genomic data of 1199 glioma patients from The Cancer Genome Atlas and validated our results using the Glioma Longitudinal AnalySiS consortium.

Results: High tumor mutational burden negatively correlates with the survival of patients with LGG harboring mIDH ( = .005). This effect was significant for both Oligodendroglioma (LGG-IDH-; MS = 2379 vs 4459 days in high vs low, respectively; = .005) and Astrocytoma (LGG-IDH-; MS = 2286 vs 4412 days in high vs low respectively; = .005). There was no differential representation of frequently mutated genes (eg, , , , and ) in either group. Gene set enrichment analysis revealed an enrichment in Gene Ontologies related to cell cycle, DNA-damage response in high versus low tumor mutational burden. Finally, we identified 6 gene sets that predict survival for LGG-IDH- and LGG-IDH-.

Conclusions: we demonstrate that tumor mutational burden is a powerful, robust, and clinically relevant prognostic factor of MS in mIDH patients.
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http://dx.doi.org/10.1093/noajnl/vdaa042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7212865PMC
March 2020

Synthetic High-density Lipoprotein Nanodiscs for Personalized Immunotherapy Against Gliomas.

Clin Cancer Res 2020 Aug 21;26(16):4369-4380. Epub 2020 May 21.

Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, Michigan.

Purpose: Gliomas are brain tumors with dismal prognoses. The standard-of-care treatments for gliomas include surgical resection, radiation, and temozolomide administration; however, they have been ineffective in providing significant increases in median survival. Antigen-specific cancer vaccines and immune checkpoint blockade may provide promising immunotherapeutic approaches for gliomas.

Experimental Design: We have developed immunotherapy delivery vehicles based on synthetic high-density lipoprotein (sHDL) loaded with CpG, a Toll-like receptor-9 agonist, and tumor-specific neoantigens to target gliomas and elicit immune-mediated tumor regression.

Results: We demonstrate that vaccination with neoantigen peptide-sHDL/CpG cocktail in combination with anti-PD-L1 immune checkpoint blocker elicits robust neoantigen-specific T-cell responses against GL261 cells and eliminated established orthotopic GL261 glioma in 33% of mice. Mice remained tumor free upon tumor cell rechallenge in the contralateral hemisphere, indicating the development of immunologic memory. Moreover, in a genetically engineered murine model of orthotopic mutant IDH1 (mIDH1) glioma, sHDL vaccination with mIDH1 neoantigen eliminated glioma in 30% of animals and significantly extended the animal survival, demonstrating the versatility of our approach in multiple glioma models.

Conclusions: Overall, our strategy provides a general roadmap for combination immunotherapy against gliomas and other cancer types.
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http://dx.doi.org/10.1158/1078-0432.CCR-20-0341DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7442596PMC
August 2020

Immunotherapy for gliomas: shedding light on progress in preclinical and clinical development.

Expert Opin Investig Drugs 2020 Jul 4;29(7):659-684. Epub 2020 Jun 4.

Department of Neurosurgery, University of Michigan Medical School , Ann Arbor, MI, USA.

Introduction: Gliomas are infiltrating brain tumors associated with high morbidity and mortality. Current standard of care includes radiation, chemotherapy, and surgical resection. Today, survival rates for malignant glioma patients remain dismal and unchanged for decades. The glioma microenvironment is highly immunosuppressive and consequently this has motivated the development of immunotherapies for counteracting this condition, enabling the immune cells within the tumor microenvironment to react against this tumor.

Areas Covered: The authors discuss immunotherapeutic strategies for glioma in phase-I/II clinical trials and illuminate their mechanisms of action, limitations, and key challenges. They also examine promising approaches under preclinical development.

Expert Opinion: In the last decade there has been an expansion in immune-mediated anti-cancer therapies. In the glioma field, sophisticated strategies have been successfully implemented in preclinical models. Unfortunately, clinical trials have not yet yielded consistent results for glioma patients. This could be attributed to our limited understanding of the complex immune cell infiltration and its interaction with the tumor cells, the selected time for treatment, the combination with other therapies and the route of administration of the agent. Applying these modalities to treat malignant glioma is challenging, but many new alternatives are emerging to by-pass these hurdles.
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http://dx.doi.org/10.1080/13543784.2020.1768528DOI Listing
July 2020

Self-organization in brain tumors: How cell morphology and cell density influence glioma pattern formation.

PLoS Comput Biol 2020 05 7;16(5):e1007611. Epub 2020 May 7.

Arizona State University, School of Mathematical & Statistical Sciences, Tempe, Arizona, United States of America.

Modeling cancer cells is essential to better understand the dynamic nature of brain tumors and glioma cells, including their invasion of normal brain. Our goal is to study how the morphology of the glioma cell influences the formation of patterns of collective behavior such as flocks (cells moving in the same direction) or streams (cells moving in opposite direction) referred to as oncostream. We have observed experimentally that the presence of oncostreams correlates with tumor progression. We propose an original agent-based model that considers each cell as an ellipsoid. We show that stretching cells from round to ellipsoid increases stream formation. A systematic numerical investigation of the model was implemented in [Formula: see text]. We deduce a phase diagram identifying key regimes for the dynamics (e.g. formation of flocks, streams, scattering). Moreover, we study the effect of cellular density and show that, in contrast to classical models of flocking, increasing cellular density reduces the formation of flocks. We observe similar patterns in [Formula: see text] with the noticeable difference that stream formation is more ubiquitous compared to flock formation.
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http://dx.doi.org/10.1371/journal.pcbi.1007611DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7244185PMC
May 2020

Laser Capture Microdissection of Glioma Subregions for Spatial and Molecular Characterization of Intratumoral Heterogeneity, Oncostreams, and Invasion.

J Vis Exp 2020 04 12(158). Epub 2020 Apr 12.

Dept. of Neurosurgery, University of Michigan Medical School; Dept. of Cell and Developmental Biology, University of Michigan Medical School; Rogel Cancer Center, University of Michigan Medical School;

Gliomas are primary brain tumors characterized by their invasiveness and heterogeneity. Specific histological patterns such as pseudopalisades, microvascular proliferation, mesenchymal transformation and necrosis characterize the histological heterogeneity of high-grade gliomas. Our laboratory has demonstrated that the presence of high densities of mesenchymal cells, named oncostreams, correlate with tumor malignancy. We have developed a unique approach to understand the mechanisms that underlie glioma's growth and invasion. Here, we describe a comprehensive protocol that utilizes laser capture microdissection (LMD) and RNA sequencing to analyze differential mRNA expression of intra-tumoral heterogeneous multicellular structures (i.e., mesenchymal areas or areas of tumor invasion). This method maintains good tissue histology and RNA integrity. Perfusion, freezing, embedding, sectioning, and staining were optimized to preserve morphology and obtain high-quality laser microdissection samples. The results indicate that perfusion of glioma bearing mice using 30% sucrose provides good morphology and RNA quality. In addition, staining tumor sections with 4% Cresyl violet and 0.5% eosin results in good nuclear and cellular staining, while preserving RNA integrity. The method described is sensitive and highly reproducible and it can be utilized to study tumor morphology in various tumor models. In summary, we describe a complete method to perform LMD that preserves morphology and RNA quality for sequencing to study the molecular features of heterogeneous multicellular structures within solid tumors.
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http://dx.doi.org/10.3791/60939DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7253033PMC
April 2020

Therapeutic Efficacy of Immune Stimulatory Thymidine Kinase and fms-like Tyrosine Kinase 3 Ligand (TK/Flt3L) Gene Therapy in a Mouse Model of High-Grade Brainstem Glioma.

Clin Cancer Res 2020 Aug 24;26(15):4080-4092. Epub 2020 Apr 24.

Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, Michigan.

Purpose: Diffuse intrinsic pontine glioma (DIPG) bears a dismal prognosis. A genetically engineered brainstem glioma model harboring the recurrent DIPG mutation, Activin A receptor type I (ACVR1)-G328V (mACVR1), was developed for testing an immune-stimulatory gene therapy.

Experimental Design: We utilized the Sleeping Beauty transposase system to generate an endogenous mouse model of mACVR1 brainstem glioma. Histology was used to characterize and validate the model. We performed RNA-sequencing analysis on neurospheres harboring mACVR1. mACVR1 neurospheres were implanted into the pons of immune-competent mice to test the therapeutic efficacy and toxicity of immune-stimulatory gene therapy using adenoviruses expressing thymidine kinase (TK) and fms-like tyrosine kinase 3 ligand (Flt3L). mACVR1 neurospheres expressing the surrogate tumor antigen ovalbumin were generated to investigate whether TK/Flt3L treatment induces the recruitment of tumor antigen-specific T cells.

Results: Histologic analysis of mACVR1 tumors indicates that they are localized in the brainstem and have increased downstream signaling of bone morphogenetic pathway as demonstrated by increased phospho-smad1/5 and Id1 levels. Transcriptome analysis of mACVR1 neurosphere identified an increase in the TGFβ signaling pathway and the regulation of cell differentiation. Adenoviral delivery of TK/Flt3L in mice bearing brainstem gliomas resulted in antitumor immunity, recruitment of antitumor-specific T cells, and increased median survival (MS).

Conclusions: This study provides insights into the phenotype and function of the tumor immune microenvironment in a mouse model of brainstem glioma harboring mACVR1. Immune-stimulatory gene therapy targeting the hosts' antitumor immune response inhibits tumor progression and increases MS of mice bearing mACVR1 tumors.
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http://dx.doi.org/10.1158/1078-0432.CCR-19-3714DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7415674PMC
August 2020

Epigenetic reprogramming and chromatin accessibility in pediatric diffuse intrinsic pontine gliomas: a neural developmental disease.

Neuro Oncol 2020 02;22(2):195-206

Department of Cell and Developmental Biology and Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, Michigan.

Diffuse intrinsic pontine glioma (DIPG) is a rare but deadly pediatric brainstem tumor. To date, there is no effective therapy for DIPG. Transcriptomic analyses have revealed DIPGs have a distinct profile from other pediatric high-grade gliomas occurring in the cerebral hemispheres. These unique genomic characteristics coupled with the younger median age group suggest that DIPG has a developmental origin. The most frequent mutation in DIPG is a lysine to methionine (K27M) mutation that occurs on H3F3A and HIST1H3B/C, genes encoding histone variants. The K27M mutation disrupts methylation by polycomb repressive complex 2 on histone H3 at lysine 27, leading to global hypomethylation. Histone 3 lysine 27 trimethylation is an important developmental regulator controlling gene expression. This review discusses the developmental and epigenetic mechanisms driving disease progression in DIPG, as well as the profound therapeutic implications of epigenetic programming.
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http://dx.doi.org/10.1093/neuonc/noz218DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7032633PMC
February 2020

Isolation and characterization of immune cells from the tumor microenvironment of genetically engineered pediatric high-grade glioma models using the sleeping beauty transposon system.

Methods Enzymol 2020 3;632:369-388. Epub 2019 Jun 3.

Department of Neurosurgery, University of Michigan Medical School, MSRB II, Ann Arbor, MI, United States; Department of Cell and Developmental Biology, University of Michigan Medical School, MSRB II, Ann Arbor, MI, United States. Electronic address:

Gliomas are the most common malignant brain tumors in the pediatric population. Even though great efforts have been made to understand their distinctive molecular characteristics, there has not been any improvements in the median survival in decades. In children, high-grade glial tumors have a median survival of 9-15 months. It has recently been demonstrated that pediatric high-grade gliomas (pHGG) are biologically and molecularly different from the adult counterparts, which could explain why conventional treatments universally fail. The development of an in vivo pHGG model harboring the specific genetic alterations encountered in pediatric gliomas is imperative in order to study the molecular basis that drives the progression and aggressiveness of these tumors. It would also enable harnessing these results for the development of novel therapeutic approaches. Our lab has implemented a method to induce brain tumors using transposon-mediated integration of plasmid DNA into cells of the subventricular zone of neonatal mouse brain. One of the main advantages of this method is that tumors are induced by altering the genome of the host cells, allowing us to recapitulate the salient features of the human disease. In this chapter we describe a method to isolate two cell populations from tumors generated in situ in mice, i.e., one population enriched in tumor cells and another population enriched in CD45+ cells. We also present methodologies as to how tumor infiltrating immune cells can be phenotypically characterized using flow cytometry.
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http://dx.doi.org/10.1016/bs.mie.2019.05.023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7047649PMC
December 2020

Functional assay to assess T-cell inhibitory properties of myeloid derived suppressor cells (MDSCs) isolated from the tumor microenvironment of murine glioma models.

Methods Enzymol 2020 18;632:215-228. Epub 2019 Jun 18.

Department of Neurosurgery, University of Michigan Medical School, MSRB II, Ann Arbor, MI, United States; Department of Cell and Developmental Biology, University of Michigan Medical School, MSRB II, Ann Arbor, MI, United States. Electronic address:

Despite advances in uncovering the molecular mechanisms that mediate glioma progression and the implementation of novel therapeutic modalities, patients' prognosis remains dismal. This is due to both systemic and local tumor induced immune suppression. We are particularly interested in the role played by infiltrating immunosuppressive myeloid derived suppressor cells (MDSCs) in the glioma tumor microenvironment (TME). This immunosuppressive TME also interferes with the effectiveness of immunotherapies against glioma. Development of multipronged treatment approaches is imperative when aiming to generate a robust anti-glioma immune response. Evaluating the inhibitory potential of MDSCs within the TME is an important aspect for developing effective treatments for glioma. Herein, we discuss methodology to assess the inhibitory effects of MDSCs isolated from the TME using a mouse glioma model.
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http://dx.doi.org/10.1016/bs.mie.2019.05.047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7038868PMC
December 2020

Prospects of biological and synthetic pharmacotherapies for glioblastoma.

Expert Opin Biol Ther 2020 03 20;20(3):305-317. Epub 2020 Jan 20.

Department of Neurosurgery, University of Michigan, Ann Arbor, MI, USA.

: The field of neuro-oncology has experienced significant advances in recent years. More is known now about the molecular and genetic characteristics of glioma than ever before. This knowledge leads to the understanding of glioma biology and pathogenesis, guiding the development of targeted therapeutics and clinical trials. The goal of this review is to describe the state of basic, translational, and clinical research as it pertains to biological and synthetic pharmacotherapy for gliomas.: Challenges remain in designing accurate preclinical models and identifying patients that are likely to respond to a particular targeted therapy. Preclinical models for therapeutic assessment are critical to identify the most promising treatment approaches.: Despite promising new therapeutics, there have been no significant breakthroughs in glioma treatment and patient outcomes. Thus, there is an urgent need to better understand the mechanisms of treatment resistance and to design effective clinical trials.
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http://dx.doi.org/10.1080/14712598.2020.1713085DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7059118PMC
March 2020

Fyn tyrosine kinase, a downstream target of receptor tyrosine kinases, modulates antiglioma immune responses.

Neuro Oncol 2020 06;22(6):806-818

Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, Michigan.

Background: High-grade gliomas are aggressive and immunosuppressive brain tumors. Molecular mechanisms that regulate the inhibitory immune tumor microenvironment (TME) and glioma progression remain poorly understood. Fyn tyrosine kinase is a downstream target of the oncogenic receptor tyrosine kinase pathway and is overexpressed in human gliomas. Fyn's role in vivo in glioma growth remains unknown. We investigated whether Fyn regulates glioma initiation, growth and invasion.

Methods: We evaluated the role of Fyn using genetically engineered mouse glioma models (GEMMs). We also generated Fyn knockdown stem cells to induce gliomas in immune-competent and immune-deficient mice (nonobese diabetic severe combined immunodeficient gamma mice [NSG], CD8-/-, CD4-/-). We analyzed molecular mechanism by RNA sequencing and bioinformatics analysis. Flow cytometry was used to characterize immune cellular infiltrates in the Fyn knockdown glioma TME.

Results: We demonstrate that Fyn knockdown in diverse immune-competent GEMMs of glioma reduced tumor progression and significantly increased survival. Gene ontology (GO) analysis of differentially expressed genes in wild-type versus Fyn knockdown gliomas showed enrichment of GOs related to immune reactivity. However, in NSG and CD8-/- and CD4-/- immune-deficient mice, Fyn knockdown gliomas failed to show differences in survival. These data suggest that the expression of Fyn in glioma cells reduces antiglioma immune activation. Examination of glioma immune infiltrates by flow cytometry displayed reduction in the amount and activity of immune suppressive myeloid derived cells in the Fyn glioma TME.

Conclusions: Gliomas employ Fyn mediated mechanisms to enhance immune suppression and promote tumor progression. We propose that Fyn inhibition within glioma cells could improve the efficacy of antiglioma immunotherapies.
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http://dx.doi.org/10.1093/neuonc/noaa006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7283034PMC
June 2020

Functional characterization of tumor antigen-specific T-cells isolated from the tumor microenvironment of sleeping beauty induced murine glioma models.

Methods Enzymol 2020 8;631:91-106. Epub 2019 Jun 8.

Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI, United States; Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, United States. Electronic address:

Diffuse Gliomas represent 80% of brain tumors with an average survival of the most aggressive form glioblastoma (GBM) 15-22 months from the time of diagnosis. The current standard of care includes tumor resection, chemotherapy and radiation, nevertheless, the incidence of recurrence remains high and there is a critical need for developing new therapeutic strategies. T-cell mediated immunotherapy that triggers an anti-tumor T cell-mediated memory response is a promising approach since it will not only attack the primary tumor but also prevent recurrence. Multiple immunotherapeutic strategies against glioma are currently being tested in clinical trials. We have developed an immune-mediated gene therapy (Thymidine kinase plus Fms-like tyrosine kinase 3 ligand: TK/Flt3L) which induces a robust anti-tumor T cell response leading to tumor regression, long-term survival and immunological memory in GBM models. Efficacy of the anti-glioma T cell therapy is determined by anti-tumor specific effector T cells. Therefore, assessing effector T cell activation status and function are critical readouts for determining the effectiveness of the therapy. Here, we detail methodologies to evaluate tumor specific T-cell responses using a genetically engineered Sleeping Beauty transposase-mediated glioma model. We first describe the glioma model and the generation of neurospheres (NS) that express the surrogate antigen cOVA. Then, we describe functional assays to determine anti-tumor T-cell response.
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http://dx.doi.org/10.1016/bs.mie.2019.05.032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7021207PMC
January 2021

Engineering patient-specific cancer immunotherapies.

Nat Biomed Eng 2019 10 12;3(10):768-782. Epub 2019 Aug 12.

Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI, USA.

Research into the immunological processes implicated in cancer has yielded a basis for the range of immunotherapies that are now considered the fourth pillar of cancer treatment (alongside surgery, radiotherapy and chemotherapy). For some aggressive cancers, such as advanced non-small-cell lung carcinoma, combination immunotherapies have resulted in unprecedented treatment efficacy for responding patients, and have become frontline therapies. Individualized immunotherapy, enabled by the identification of patient-specific mutations, neoantigens and biomarkers, and facilitated by advances in genomics and proteomics, promises to broaden the responder patient population. In this Perspective, we give an overview of immunotherapies leveraging engineering approaches, including the design of biomaterials, delivery strategies and nanotechnology solutions, for the realization of individualized cancer treatments such as nanoparticle vaccines customized with neoantigens, cell therapies based on patient-derived dendritic cells and T cells, and combinations of theranostic strategies. Developments in precision cancer immunotherapy will increasingly rely on the adoption of engineering principles.
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http://dx.doi.org/10.1038/s41551-019-0436-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6783331PMC
October 2019

IDH1-R132H acts as a tumor suppressor in glioma via epigenetic up-regulation of the DNA damage response.

Sci Transl Med 2019 02;11(479)

Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI 48109, USA.

Patients with glioma whose tumors carry a mutation in isocitrate dehydrogenase 1 (IDH1) are younger at diagnosis and live longer. mutations co-occur with other molecular lesions, such as 1p/19q codeletion, inactivating mutations in the tumor suppressor protein 53 ) gene, and loss-of-function mutations in alpha thalassemia/mental retardation syndrome X-linked gene (). All adult low-grade gliomas (LGGs) harboring ATRX loss also express the IDH1 mutation. The current molecular classification of LGGs is based, partly, on the distribution of these mutations. We developed a genetically engineered mouse model harboring IDH1, and inactivating mutations, and activated NRAS G12V. Previously, we established that ATRX deficiency, in the context of wild-type IDH1, induces genomic instability, impairs nonhomologous end-joining DNA repair, and increases sensitivity to DNA-damaging therapies. In this study, using our mouse model and primary patient-derived glioma cultures with IDH1 mutations, we investigated the function of IDH1 in the context of TP53 and ATRX loss. We discovered that IDH1 expression in the genetic context of and gene inactivation (i) increases median survival in the absence of treatment, (ii) enhances DNA damage response (DDR) via epigenetic up-regulation of the ataxia-telangiectasia-mutated (ATM) signaling pathway, and (iii) elicits tumor radioresistance. Accordingly, pharmacological inhibition of ATM or checkpoint kinases 1 and 2, essential kinases in the DDR, restored the tumors' radiosensitivity. Translation of these findings to patients with IDH1 glioma harboring TP53 and ATRX loss could improve the therapeutic efficacy of radiotherapy and, consequently, patient survival.
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http://dx.doi.org/10.1126/scitranslmed.aaq1427DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6400220PMC
February 2019

High-Density Lipoprotein-Mimicking Nanodiscs for Chemo-immunotherapy against Glioblastoma Multiforme.

ACS Nano 2019 02 11;13(2):1365-1384. Epub 2019 Feb 11.

Glioblastoma multiforme (GBM) is an aggressive primary brain tumor, for which there is no cure. Treatment effectiveness for GBM has been limited due to tumor heterogeneity, an immunosuppressive tumor microenvironment (TME), and the presence of the blood-brain barrier, which hampers the transport of chemotherapeutic compounds to the central nervous system (CNS). High-density lipoprotein (HDL)-mimicking nanodiscs hold considerable promise to achieve delivery of bioactive compounds into tumors. Herein, we tested the ability of synthetic HDL nanodiscs to deliver chemotherapeutic agents to the GBM microenvironment and elicit tumor regression. To this end, we developed chemo-immunotherapy delivery vehicles based on sHDL nanodiscs loaded with CpG, a Toll-like receptor 9 (TLR9) agonist, together with docetaxel (DTX), a chemotherapeutic agent, for targeting GBM. Our data show that delivery of DTX-sHDL-CpG nanodiscs into the tumor mass elicited tumor regression and antitumor CD8 T cell responses in the brain TME. We did not observe any overt off-target side effects. Furthermore, the combination of DTX-sHDL-CpG treatment with radiation (IR), which is the standard of care for GBM, resulted in tumor regression and long-term survival in 80% of GBM-bearing animals. Mice remained tumor-free upon tumor cell rechallenge in the contralateral hemisphere, indicating the development of anti-GBM immunological memory. Collectively, these data indicate that sHDL nanodiscs constitute an effective drug delivery platform for the treatment of GBM, resulting in tumor regression, long-term survival, and immunological memory when used in combination with IR. The proposed delivery platform has significant potential for clinical translation.
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http://dx.doi.org/10.1021/acsnano.8b06842DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6484828PMC
February 2019

Evaluation of Biomarkers in Glioma by Immunohistochemistry on Paraffin-Embedded 3D Glioma Neurosphere Cultures.

J Vis Exp 2019 01 9(143). Epub 2019 Jan 9.

Department of Neurosurgery, University of Michigan Medical School; Department of Cell & Developmental Biology, University of Michigan;

Analysis of protein expression in glioma is relevant for several aspects in the study of its pathology. Numerous proteins have been described as biomarkers with applications in diagnosis, prognosis, classification, state of tumor progression, and cell differentiation state. These analyses of biomarkers are also useful to characterize tumor neurospheres (NS) generated from glioma patients and glioma models. Tumor NS provide a valuable in vitro model to assess different features of the tumor from which they are derived and can more accurately mirror glioma biology. Here we describe a detailed method to analyze biomarkers in tumor NS using immunohistochemistry (IHC) on paraffin-embedded tumor NS.
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http://dx.doi.org/10.3791/58931DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6352905PMC
January 2019

Mutant ATRX: uncovering a new therapeutic target for glioma.

Expert Opin Ther Targets 2018 07 20;22(7):599-613. Epub 2018 Jun 20.

a Department of Neurosurgery , The University of Michigan School of Medicine , Ann Arbor , MI , USA.

Introduction: ATRX is a chromatin remodeling protein whose main function is the deposition of the histone variant H3.3. ATRX mutations are widely distributed in glioma, and correlate with alternative lengthening of telomeres (ALT) development, but they also affect other cellular functions related to epigenetic regulation. Areas covered: We discuss the main molecular characteristics of ATRX, from its various functions in normal development to the effects of its loss in ATRX syndrome patients and animal models. We focus on the salient consequences of ATRX mutations in cancer, from a clinical to a molecular point of view, focusing on both adult and pediatric glioma. Finally, we will discuss the therapeutic opportunities future research perspectives. Expert opinion: ATRX is a major component of various essential cellular pathways, exceeding its functions as a histone chaperone (e.g. DNA replication and repair, chromatin higher-order structure regulation, gene transcriptional regulation, etc.). However, it is unclear how the loss of these functions in ATRX-null cancer cells affects cancer development and progression. We anticipate new treatments and clinical approaches will emerge for glioma and other cancer types as mechanistic and molecular studies on ATRX are only just beginning to reveal the many critical functions of this protein in cancer.
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http://dx.doi.org/10.1080/14728222.2018.1487953DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6044414PMC
July 2018

Multi-focal sequencing of a diffuse intrinsic pontine glioma establishes PTEN loss as an early event.

NPJ Precis Oncol 2017 14;1(1):32. Epub 2017 Sep 14.

Department of Pediatrics, Division of Pediatric Hematology/Oncology, Michigan Medicine, Ann Arbor, MI 48109 USA.

Improved molecular understanding is needed for rational treatment of diffuse intrinsic pontine gliomas (DIPG). Here, using multi-focal paired tumor and germline exome DNA and RNA sequencing, we uncovered phosphatase and tensin homolog () loss as a clonal mutation in the case of a 6-year-old boy with a diffuse intrinsic pontine glioma, and incorporated copy number alteration analyses to provide a more detailed understanding of clonal evolution in diffuse intrinsic pontine gliomas. As well, using the PedcBioPortal, we found alterations in in 16 of 326 (4.9%) cases of pediatric high-grade glioma (3 of 154 (1.9%) brainstem) for which full sequencing data was available. Our data strengthens the association with loss in diffuse intrinsic pontine gliomas and provides further argument for the inclusion of in future targeted sequencing panels for pediatric diffuse intrinsic pontine gliomas and for the development and optimization of mTOR/PI3K inhibitors with optimal central nervous system penetration.
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http://dx.doi.org/10.1038/s41698-017-0033-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5871904PMC
September 2017

Molecular ablation of tumor blood vessels inhibits therapeutic effects of radiation and bevacizumab.

Neuro Oncol 2018 09;20(10):1356-1367

Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, Michigan.

Background: Glioblastoma (GBM) is an aggressive and highly vascular tumor with median survival below 2 years. Despite advances in surgery, radiotherapy, and chemotherapy, survival has improved modestly. To combat glioma vascular proliferation, anti-angiogenic agents targeting vascular endothelial growth factor (VEGF) were introduced. Preclinically these agents were effective, yet they did not improve overall survival in phase III trials. We tested the hypothesis that ganciclovir (GCV)-mediated killing of proliferating endothelial cells expressing herpes simplex virus type 1 thymidine kinase (HSV1-TK) would have direct antitumor effects, and whether vessel ablation would affect the antitumor activity of anti-VEGF antibodies and radiotherapy.

Methods: Proliferating endothelial cells were eliminated using GCV-mediated killing of proliferating endothelial cells expressing HSV1-TK (in Tie2-TK-IRES-GFP mice). Syngeneic NRAS/p53 (NP) gliomas were implanted into the brains of Tie2-TK-IRES-GFP mice. Endothelial proliferation activates the Tie2 promoter and HSV1-TK expression. Administration of GCV kills proliferating tumor endothelial cells and slows tumor growth. The effects of endothelial cell ablation on anti-angiogenic therapy were examined using anti-VEGF antibodies or irradiation.

Results: GCV administration reduced tumor growth and vascular density, increased tumor apoptosis, and prolonged survival. Anti-VEGF antibodies or irradiation also prolonged survival. Surprisingly, combining GCV with irradiation, or with anti-VEGF antibodies, reduced their individual therapeutic effects.

Conclusion: GCV-mediated killing of proliferating endothelial cells expressing HSV1-TK, anti-VEGF antibodies, or irradiation all reduced growth of a murine glioma. However, elimination of microvascular proliferation decreased the efficacy of anti-VEGF or irradiation therapy. We conclude that, in our model, the integrity of proliferating vessels is necessary for the antiglioma effects of anti-VEGF and radiation therapy.
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http://dx.doi.org/10.1093/neuonc/noy055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6140787PMC
September 2018

Native Chromatin Immunoprecipitation Using Murine Brain Tumor Neurospheres.

J Vis Exp 2018 01 29(131). Epub 2018 Jan 29.

Department of Cell and Developmental Biology, University of Michigan Medical School; Department of Neurosurgery, University of Michigan Medical School;

Epigenetic modifications may be involved in the development and progression of glioma. Changes in methylation and acetylation of promoters and regulatory regions of oncogenes and tumor suppressors can lead to changes in gene expression and play an important role in the pathogenesis of brain tumors. Native chromatin immunoprecipitation (ChIP) is a popular technique that allows the detection of modifications or other proteins tightly bound to DNA. In contrast to cross-linked ChIP, in native ChIP, cells are not treated with formaldehyde to covalently link protein to DNA. This is advantageous because sometimes crosslinking may fix proteins that only transiently interact with DNA and do not have functional significance in gene regulation. In addition, antibodies are generally raised against unfixed peptides. Therefore, antibody specificity is increased in native ChIP. However, it is important to keep in mind that native ChIP is only applicable to study histones or other proteins that bind tightly to DNA. This protocol describes the native chromatin immunoprecipitation on murine brain tumor neurospheres.
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http://dx.doi.org/10.3791/57016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5912236PMC
January 2018