CAR T Cells Targeting Podoplanin Reduce Orthotopic Glioblastomas in Mouse Brains

Chimeric antigen receptor T-cell immunotherapy for glioblastoma: practical insights for neurosurgeons

The prognosis for glioblastoma (GBM) remains exceedingly poor despite state-of-the-art multimodal therapy. Immunotherapy, particularly with cytotoxic T cells, represents a promising alternative. Perhaps the most prominent T-cell technology is the chimeric antigen receptor (CAR), which in 2017 received accelerated approval from the Food and Drug Administration for the treatment of hematological malignancies. Several CARs for GBM have been recently tested in clinical trials with exciting results. The authors review these clinical data and discuss areas of ongoing research.

Clinical chimeric antigen receptor-T cell therapy: a new and promising treatment modality for glioblastoma

Chimeric antigen receptor (CAR)-T cell therapy is now approved in the United States and Europe as a standard treatment for relapsed/refractory B-cell malignancies. It has also been approved recently by the Therapeutic Goods Administration in Australia and may soon be publicly reimbursed. This advance has accentuated scientific, clinical and commercial interest in adapting this exciting technology for the treatment of solid cancers where it is widely recognised that the challenges of overcoming a hostile tumor microenvironment are most acute. Indeed, CAR-T cell technology may be of the greatest value for those cancers that lack pre-existing immunity because they are immunologically 'cold', or have a low somatic tumor mutation load, or both. These cancers are generally not amenable to therapeutic immune checkpoint blockade, but CAR-T cell therapy may be effective because it provides an abundant supply of autologous tumor-specific T cells. This is achieved by using genetic engineering to re-direct autologous T-cell cytotoxicity towards a tumor-associated antigen, bypassing endogenous T-cell requirements for antigen processing, MHC-dependent antigen presentation and co-stimulation. One of the most challenging solid cancers is glioblastoma, which has among the least permissive immunological milieu of any cancer, and which is almost always fatal. Here, we argue that CAR-T cell technology may counter some glioblastoma defences and provide a beachhead for furthering our eventual therapeutic aims of restoring effective antitumor immunity. Although clinical investigation of CAR-T cell therapy for glioblastoma is at an early stage, we discuss three recently published studies, which feature significant differences in target antigen, CAR-T cell phenotype, route of administration and tumor response. We discuss the lessons, which may be learned from these studies and which may guide further progress in the field.

Podoplanin Expression and IDH-Wildtype Status Predict Venous Thromboembolism in Patients with High-Grade Gliomas in the Early Postoperative Period

OBJECTIVE

Venous thromboembolism (VTE) often is encountered in patients with high-grade gliomas. The underlying mechanisms are unclear, as is the optimal prophylactic protocol. The purpose of the present study was to identify risk factors of VTE and examine the validity of early VTE detection in high-grade gliomas.

METHODS

We reviewed the medical records of 165 patients with newly diagnosed high-grade glioma treated at Niigata University Hospital during the years 2009 to 2016. If the serum D-dimer levels increased to 5.0 μg/mL or more, computed tomography was performed to detect VTE. Furthermore, immunohistochemistry with antibodies against podoplanin was performed on available 101 tumor tissues.

RESULTS

Of the 165 patients, 44 (26.7%) developed VTE. Of the 44 patients, 34 (79.5%) developed VTE within 7 days after surgery. No fatal VTE occurred and major complications secondary to anticoagulation occurred in only 2 (1.2%) patients. On multivariate analysis, lower Karnofsky Performance Scale status, podoplanin expression, and isocitrate dehydrogenase-wildtype status were independently associated with the risk of VTE (P < 0.05).

CONCLUSIONS

We found that most VTEs occurred early in the postoperative period and commonly in patients with lower Karnofsky Performance Scale status and isocitrate dehydrogenase-wildtype gliomas, which expressed podoplanin.

Venous Thromboembolism in Brain Tumors: Risk Factors, Molecular Mechanisms, and Clinical Challenges

Venous thromboembolism (VTE) is a common complication in patients with primary brain tumors, with up to 20% of patients per year having a VTE event. Clinical risk factors for VTE include glioblastoma subtype, paresis, or surgery. Furthermore, specific factors playing a role in tumor biology were recently identified to predispose to prothrombotic risk. For instance, mutations in the isocitrate dehydrogenase 1 (IDH1) gene, which occurs in a subgroup of glioma, correlate with risk of VTE, with low incidence in patients with presence of an IDH1 mutation compared with those with IDH1 wild-type status. In addition, expression of the glycoprotein podoplanin on brain tumors was associated with both intratumoral thrombi and high risk of VTE. As podoplanin has the ability to activate platelets, a mechanistic role of podoplanin-mediated platelet activation in VTE development has been suggested. From a clinical point of view, the management of patients with primary brain tumors and VTE is challenging. Anticoagulation is required to treat patients; however, it is associated with increased risk of intracranial hemorrhage. This review focuses on describing the epidemiology, risk factors, and mechanisms of brain tumor-associated thrombosis and discusses clinical challenges in the prevention and treatment of VTE in patients with brain tumors.

Lentiviral Vectors as Tools for the Study and Treatment of Glioblastoma

Glioblastoma (GBM) has the worst prognosis among brain tumors, hence basic biology, preclinical, and clinical studies are necessary to design effective strategies to defeat this disease. Gene transfer vectors derived from the most-studied lentivirus-the Human Immunodeficiency Virus type 1-have wide application in dissecting GBM specific features to identify potential therapeutic targets. Last-generation lentiviruses (LV), highly improved in safety profile and gene transfer capacity, are also largely employed as delivery systems of therapeutic molecules to be employed in gene therapy (GT) approaches. LV were initially used in GT protocols aimed at the expression of suicide factors to induce GBM cell death. Subsequently, LV were adopted to either express small noncoding RNAs to affect different aspects of GBM biology or to overcome the resistance to both chemo- and radiotherapy that easily develop in this tumor after initial therapy. Newer frontiers include adoption of LV for engineering T cells to express chimeric antigen receptors recognizing specific GBM antigens, or for transducing specific cell types that, due to their biological properties, can function as carriers of therapeutic molecules to the cancer mass. Finally, LV allow the setting up of improved animal models crucial for the validation of GBM specific therapies.

Podoplanin in Inflammation and Cancer

Podoplanin is a small cell-surface mucin-like glycoprotein that plays a crucial role in the development of the alveoli, heart, and lymphatic vascular system. Emerging evidence indicates that it is also involved in the control of mammary stem-cell activity and biogenesis of platelets in the bone marrow, and exerts an important function in the immune response. Podoplanin expression is upregulated in different cell types, including fibroblasts, macrophages, T helper cells, and epithelial cells, during inflammation and cancer, where it plays important roles. Podoplanin is implicated in chronic inflammatory diseases, such as psoriasis, multiple sclerosis, and rheumatoid arthritis, promotes inflammation-driven and cancer-associated thrombosis, and stimulates cancer cell invasion and metastasis through a variety of strategies. To accomplish its biological functions, podoplanin must interact with other proteins located in the same cell or in neighbor cells. The binding of podoplanin to its ligands leads to modulation of signaling pathways that regulate proliferation, contractility, migration, epithelial⁻mesenchymal transition, and remodeling of the extracellular matrix. In this review, we describe the diverse roles of podoplanin in inflammation and cancer, depict the protein ligands of podoplanin identified so far, and discuss the mechanistic basis for the involvement of podoplanin in all these processes.

Functional significance of the platelet immune receptors GPVI and CLEC-2

Although platelets are best known for their role in hemostasis, they are also crucial in development, host defense, inflammation, and tissue repair. Many of these roles are regulated by the immune-like receptors glycoprotein VI (GPVI) and C-type lectin receptor 2 (CLEC-2), which signal through an immunoreceptor tyrosine-based activation motif (ITAM). GPVI is activated by collagen in the subendothelial matrix, by fibrin and fibrinogen in the thrombus, and by a remarkable number of other ligands. CLEC-2 is activated by the transmembrane protein podoplanin, which is found outside of the vasculature and is upregulated in development, inflammation, and cancer, but there is also evidence for additional ligands. In this Review, we discuss the physiological and pathological roles of CLEC-2 and GPVI and their potential as targets in thrombosis and thrombo-inflammatory disorders (i.e., disorders in which inflammation plays a critical role in the ensuing thrombosis) relative to current antiplatelet drugs.

Combination of isocitrate dehydrogenase 1 (IDH1) mutation and podoplanin expression in brain tumors identifies patients at high or low risk of venous thromboembolism

Essentials Risk stratification for venous thromboembolism (VTE) in patients with brain tumors is challenging. Patients with IDH1 wildtype and high podoplanin expression have a 6-month VTE risk of 18.2%. Patients with IDH1 mutation and no podoplanin expression have a 6-month VTE risk of 0%. IDH1 mutation and podoplanin overexpression in primary brain tumors appear to be exclusive.

SUMMARY

Background Venous thromboembolism (VTE) is a frequent complication in primary brain tumor patients. Independent studies revealed that podoplanin expression in brain tumors is associated with increased VTE risk, whereas the isocitrate dehydrogenase 1 (IDH1) mutation is associated with very low VTE risk. Objectives To investigate the interrelation between intratumoral podoplanin expression and IDH1 mutation, and their mutual impact on VTE development. Patients/Methods In a prospective cohort study, intratumoral IDH1 R132H mutation and podoplanin were determined in brain tumor specimens (mainly glioma) by immunohistochemistry. The primary endpoint of the study was symptomatic VTE during a 2-year follow-up. Results All brain tumors that expressed podoplanin to a medium-high extent showed also an IDH1 wild-type status. A score based on IDH1 status and podoplanin expression levels allowed prediction of the risk of VTE. Patients with wild-type IDH1 brain tumors and high podoplanin expression had a significantly increased VTE risk compared with those with mutant IDH1 tumors and no podoplanin expression (6-month risk 18.2% vs. 0%). Conclusions IDH1 mutation and podoplanin overexpression seem to be exclusive. Although brain tumor patients with IDH1 mutation are at very low risk of VTE, the risk of VTE in patients with IDH1 wild-type tumors is strongly linked to podoplanin expression levels.

Podoplanin: An emerging cancer biomarker and therapeutic target

Podoplanin (PDPN) is a transmembrane receptor glycoprotein that is upregulated on transformed cells, cancer associated fibroblasts and inflammatory macrophages that contribute to cancer progression. In particular, PDPN increases tumor cell clonal capacity, epithelial mesenchymal transition, migration, invasion, metastasis and inflammation. Antibodies, CAR-T cells, biologics and synthetic compounds that target PDPN can inhibit cancer progression and septic inflammation in preclinical models. This review describes recent advances in how PDPN may be used as a biomarker and therapeutic target for many types of cancer, including glioma, squamous cell carcinoma, mesothelioma and melanoma.

Podoplanin emerges as a functionally relevant oral cancer biomarker and therapeutic target

Oral cancer has become one of the most aggressive types of cancer, killing 140,000 people worldwide every year. Current treatments for oral cancer include surgery and radiation therapies. These procedures can be very effective; however, they can also drastically decrease the quality of life for survivors. New chemotherapeutic treatments are needed to more effectively combat oral cancer. The transmembrane receptor podoplanin (PDPN) has emerged as a functionally relevant oral cancer biomarker and chemotherapeutic target. PDPN expression promotes tumor cell migration leading to oral cancer invasion and metastasis. Here, we describe the role of PDPN in oral squamous cell carcinoma progression, and how it may be exploited to prevent and treat oral cancer.

Glycosylation Changes in Brain Cancer

Protein glycosylation is a posttranslational modification that affects more than half of all known proteins. Glycans covalently bound to biomolecules modulate their functions by both direct interactions, such as the recognition of glycan structures by binding partners, and indirect mechanisms that contribute to the control of protein conformation, stability, and turnover. The focus of this Review is the discussion of aberrant glycosylation related to brain cancer. Altered sialylation and fucosylation of N- and O-glycans play a role in the development and progression of brain cancer. Additionally, aberrant O-glycan expression has been implicated in brain cancer. This Review also addresses the clinical potential and applications of aberrant glycosylation for the detection and treatment of brain cancer. The viable roles glycans may play in the development of brain cancer therapeutics are addressed as well as cancer-glycoproteomics and personalized medicine. Glycoprotein alterations are considered as a hallmark of cancer while high expression in body fluids represents an opportunity for cancer assessment.

Yeast display biopanning identifies human antibodies targeting glioblastoma stem-like cells

Glioblastoma stem-like cells (GSC) are hypothesized to evade current therapies and cause tumor recurrence, contributing to poor patient survival. Existing cell surface markers for GSC are developed from embryonic or neural stem cell systems; however, currently available GSC markers are suboptimal in sensitivity and specificity. We hypothesized that the GSC cell surface proteome could be mined with a yeast display antibody library to reveal novel immunophenotypes. We isolated an extensive collection of antibodies that were differentially selective for GSC. A single domain antibody VH-9.7 showed selectivity for five distinct patient-derived GSC lines and visualized orthotopic GBM xenografts in vivo after conjugation with a near-infrared dye. These findings demonstrate a previously unexplored high-throughput strategy for GSC-selective antibody discovery, to aid in GSC isolation, diagnostic imaging, and therapeutic targeting.

The efficacy of chimeric antigen receptor (CAR) immunotherapy in animal models for solid tumors: A systematic review and meta-analysis

BACKGROUND

Most recently, an emerging theme in the field of tumor immunology predominates: chimeric antigen receptor (CAR) therapy in treating solid tumors. The number of related preclinical trials was surging. However, an evaluation of the effects of preclinical studies remained absent. Hence, a meta-analysis was conducted on the efficacy of CAR in animal models for solid tumors.

METHODS

The authors searched PubMed/Medline, Embase, and Google scholar up to April 2017. HR for survival was extracted based on the survival curve. The authors used fixed effect models to combine the results of all the trials. Heterogeneity was assessed by I-square statistic. Quality assessment was conducted following the Stroke Therapy Academic Industry Roundtable standard. Publication bias was assessed using Egger's test.

RESULTS

Eleven trials were included, including 54 experiments with a total of 362 animals involved. CAR immunotherapy significantly improved the survival of animals (HR: 0.25, 95% CI: 0.13-0.37, P < 0.001). The quality assessment revealed that no study reported whether allocation concealment and blinded outcome assessment were conducted, and only five studies implemented randomization.

CONCLUSIONS

This meta-analysis indicated that CAR therapy may be a potential clinical strategy in treating solid tumors.

Adoptive immunotherapy for the treatment of glioblastoma: progress and possibilities

Patients with glioblastoma have a very poor prognosis. Adoptive cellular therapy (ACT) is defined as the collection of circulating or tumor-infiltrating lymphocytes, their selection, modification, expansion and activation, and their re-administration to patients in order to induce antitumor activity. Although various ACTs have been attempted, most failed to improve the outcome. Immune checkpoint blockade antibodies and T cell engineering with tumor-specific chimeric antigen receptors suggest the emergence of a new era of immunotherapy. Here, we summarize approaches with ACTs using genetically modified T cells, which have been improved by enhancing their antitumor activity, and discuss strategies to develop these therapies. The mechanisms by which gliomas modulate and evade the immune system are also discussed.

Establishment of Mouse Monoclonal Antibody LpMab-13 Against Human Podoplanin

Podoplanin (PDPN)/Aggrus is a type-I transmembrane sialoglycoprotein, which possesses a platelet aggregation-stimulating (PLAG) domain. The O-glycosylation on Thr52 of human PDPN (hPDPN) is critical for the interaction of hPDPN with C-type lectin-like receptor-2 (CLEC-2), resulting in platelet aggregation. Many anti-hPDPN monoclonal antibodies (MAbs) against PLAG domains and non-PLAG domains have been established; however, mouse anti-PLAG2/3 MAb, the epitope of which is consistent with rat anti-PLAG2/3 MAb NZ-1, has not been established. NZ-1 inhibits the hPDPN-CLEC-2 interaction and is also useful for anti-PA tag MAb. We recently established CasMab technology to produce MAbs against membranous proteins. Herein, we produced a novel anti-hPDPN MAb, LpMab-13, which binds to PLAG2/3 domains. LpMab-13 recognized endogenous hPDPN of cancer cells, including glioblastoma, oral cancer, lung cancer, and malignant mesothelioma, and normal cells such as lymphatic endothelial cells and podocytes of kidney in Western blot, flow cytometry, and immunohistochemistry. LpMab-13 recognized glycan-deficient hPDPN in flow cytometry, indicating that the interaction between LpMab-13 and hPDPN is independent of its glycosylation. The minimum epitope of LpMab-13 was identified as Ala42-Asp49 of hPDPN using Western blot and flow cytometry. The combination of different epitope-possessing MAbs could be advantageous for the hPDPN-targeting diagnosis and therapy.

Antitumor activity of chLpMab-2, a human-mouse chimeric cancer-specific antihuman podoplanin antibody, via antibody-dependent cellular cytotoxicity

Human podoplanin (hPDPN), a platelet aggregation‐inducing transmembrane glycoprotein, is expressed in different types of tumors, and it binds to C‐type lectin‐like receptor 2 (CLEC‐2). The overexpression of hPDPN is involved in invasion and metastasis. Anti‐hPDPN monoclonal antibodies (mAbs) such as NZ‐1 have shown antitumor and antimetastatic activities by binding to the platelet aggregation‐stimulating (PLAG) domain of hPDPN. Recently, we developed a novel mouse anti‐hPDPN mAb, LpMab‐2, using the cancer‐specific mAb (CasMab) technology. In this study we developed chLpMab‐2, a human–mouse chimeric anti‐hPDPN antibody, derived from LpMab‐2. chLpMab‐2 was produced using fucosyltransferase 8‐knockout (KO) Chinese hamster ovary (CHO)‐S cell lines. By flow cytometry, chLpMab‐2 reacted with hPDPN‐expressing cancer cell lines including glioblastomas, mesotheliomas, and lung cancers. However, it showed low reaction with normal cell lines such as lymphatic endothelial and renal epithelial cells. Moreover, chLpMab‐2 exhibited high antibody‐dependent cellular cytotoxicity (ADCC) against PDPN‐expressing cells, despite its low complement‐dependent cytotoxicity. Furthermore, treatment with chLpMab‐2 abolished tumor growth in xenograft models of CHO/hPDPN, indicating that chLpMab‐2 suppressed tumor development via ADCC. In conclusion, chLpMab‐2 could be useful as a novel antibody‐based therapy against hPDPN‐expressing tumors.

Advances in the molecular genetics of gliomas - implications for classification and therapy

Genome-wide molecular-profiling studies have revealed the characteristic genetic alterations and epigenetic profiles associated with different types of gliomas. These molecular characteristics can be used to refine glioma classification, to improve prediction of patient outcomes, and to guide individualized treatment. Thus, the WHO Classification of Tumours of the Central Nervous System was revised in 2016 to incorporate molecular biomarkers - together with classic histological features - in an integrated diagnosis, in order to define distinct glioma entities as precisely as possible. This paradigm shift is markedly changing how glioma is diagnosed, and has important implications for future clinical trials and patient management in daily practice. Herein, we highlight the developments in our understanding of the molecular genetics of gliomas, and review the current landscape of clinically relevant molecular biomarkers for use in classification of the disease subtypes. Novel approaches to the genetic characterization of gliomas based on large-scale DNA-methylation profiling and next-generation sequencing are also discussed. In addition, we illustrate how advances in the molecular genetics of gliomas can promote the development and clinical translation of novel pathogenesis-based therapeutic approaches, thereby paving the way towards precision medicine in neuro-oncology.

Chimeric antigen receptors for treatment of glioblastoma: a practical review of challenges and ways to overcome them

Glioblastoma (GBM) is by far the most common and the most aggressive of all the primary brain malignancies. No curative therapy exists, and median life expectancy hovers at around 1 year after diagnosis, with a minute fraction surviving beyond 5 years. The difficulty in treating GBM lies in the cancer's protected niche within the blood-brain barrier and the heterogeneity of the cancer cells, which possess varying degrees of susceptibility to various common modalities of treatment. Over time, it is the tumor heterogeneity of GBM and the ability of the cancer stem cells to evolve in response treatment that renders the cancer refractory to conventional treatment. Therefore, research has increasingly focused on treatment that incorporates knowledge of GBM molecular biology to therapeutic strategies. One type of therapy that shows great promise is the area of T-cell immunotherapy to target GBM-specific tumor antigens. One attractive strategy is to use T cells that have undergone genetic modification to express a chimeric antigen receptor capable of interacting with tumor antigens. In this article, we will review chimeric antigen receptor T-cell therapy, their advantages, drawbacks, challenges facing their use and how those challenges may be overcome.

Genetically Engineered Macrophages: A Potential Platform for Cancer Immunotherapy

In spite of their successes against hematologic malignancies, immunotherapeutic interventions for the treatment of patients with glioblastoma (GBM) have thus far been unsuccessful. This is in part due to the presence of a tumor microenvironment that fosters neoplastic growth and protects the tumor from destruction by the immune system. A novel genetically engineered macrophage-based platform has been developed with the potential to minimize the effects of the suppressive tumor microenvironment and improve innate and adaptive antitumor immune responses. A newly described lentiviral expression system was validated for the generation of transduced monocytes and monocyte-derived macrophages, and transgene expression was shown to be stable over the course of weeks to months, both in vitro and in a mouse xenograft model of GBM. Furthermore, the genetically engineered macrophages (GEMs) neither caused morbidity in animals nor contributed to accelerated tumor growth. The versatility of GEMs is also highlighted by showing that they can be engineered to secrete proteins that either reduce immune suppression, such as the soluble transforming growth factor beta receptor II, or promote immune cell activation, by expressing interleukin 21. There is also the potential to prevent GEM-mediated immune suppression by using the CRISPR system to knock out genes responsible for dysfunction of cytotoxic cells, including interleukin 10 and programmed death-ligand 1. Together, these results suggest that GEMs are an ideal cell type for transforming the tumor microenvironment and enhancing antitumor immunity. Importantly, it is anticipated that these findings will have broad applicability to other types of tumors with microenvironments that currently preclude successful immunotherapeutic approaches.

Developing immunotherapeutic strategies to target brain tumors

INTRODUCTION

Recent years have seen rapid growth in cancer treatments that enhance the anti-tumor activities of the immune system. Collectively known as immunotherapy, modulation of the immune system has shown success treating some hematological malignancies, but has yet to be successfully applied to the treatment of patients with brain tumors.

AREAS COVERED

This review highlights mechanistic insights from murine studies and compiled recent clinical trial data, focusing on the most aggressive brain tumor, glioblastoma (GBM). The field has recently accumulated a critical mass of data, and we discuss past treatment failures in the context of newly developed approaches now entering clinical trials. This article provides an overview of the immunotherapeutic armamentarium currently in development for the treatment of patients with GBM, who are in dire need of safe and effective therapies. Expert commentary: Themes that emerge include the importance of mitigating the effects of an immunosuppressive tumor microenvironment and the potential for innate immune cell activation to enhance cytotoxic anti-tumor activity. Consideration of these studies as a collective may inform the design of new immunotherapies, as well as the immune monitoring protocols for patients participating in clinical trials.