Pilot Trial of Adoptive Transfer of Chimeric Antigen Receptor-transduced T Cells Targeting EGFRvIII in Patients With Glioblastoma

Engineered cells as glioblastoma therapeutics

In spite of significant recent advances in our understanding of the genetics and cell biology of glioblastoma, to date, this has not led to improved treatments for this cancer. In addition to small molecule, antibody, and engineered virus approaches, engineered cells are also being explored as glioblastoma therapeutics. This includes CAR-T cells, CAR-NK cells, as well as engineered neural stem cells and mesenchymal stem cells. Here we review the state of this field, starting with clinical trial studies. These have established the feasibility and safety of engineered cell therapies for glioblastoma and show some evidence for activity. Next, we review the preclinical literature and compare the strengths and weaknesses of various starting cell types for engineered cell therapies. Finally, we discuss future directions for this nascent but promising modality for glioblastoma therapy.

Advances in Immunotherapies for Gliomas

PURPOSE OF REVIEW

Immunotherapy-based treatment of glioblastoma has been challenging because of the tumor's limited neoantigen profile and weakly immunogenic composition. This article summarizes the current clinical trials underway by evaluating the leading immunotherapy paradigms, the encountered barriers, and the future directions needed to overcome such tumor evasion.

RECENT FINDINGS

A limited number of phase III trials have been completed for checkpoint inhibitor, vaccine, as well as gene therapies, and have been unable to show improvement in survival outcomes. Nevertheless, these trials have also shown these strategies to be safe and promising with further adaptations. Further large-scale studies for chimeric antigen receptors T cell therapies and viral therapies are anticipated. Many current trials are broadening the number of antigens targeted and modulating the microtumor environment to abrogate early mechanisms of resistance. Future GBM treatment will also likely require synergistic effects by combination regimens.

Advances in immunotherapy for glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most common and aggressive malignant brain tumor of the central nervous system and has a very poor prognosis. The current standard of care for patients with GBM involves surgical resection, radiotherapy, and chemotherapy. Unfortunately, conventional therapies have not resulted in significant improvements in the survival outcomes of patients with GBM; therefore, the overall mortality rate remains high. Immunotherapy is a type of cancer treatment that helps the immune system to fight cancer and has shown success in different types of aggressive cancers. Recently, healthcare providers have been actively investigating various immunotherapeutic approaches to treat GBM. We reviewed the most promising immunotherapy candidates for glioblastoma that have achieved encouraging results in clinical trials, focusing on immune checkpoint inhibitors, oncolytic viruses, nonreplicating viral vectors, and chimeric antigen receptor (CAR) immunotherapies.

The current landscape of immunotherapy for pediatric brain tumors

Pediatric central nervous system tumors are the most common solid malignancies in childhood, and aggressive therapy often leads to long-term sequelae in survivors, making these tumors challenging to treat. Immunotherapy has revolutionized prospects for many cancer types in adults, but the intrinsic complexity of treating pediatric patients and the scarcity of clinical studies of children to inform effective approaches have hampered the development of effective immunotherapies in pediatric settings. Here, we review recent advances and ongoing challenges in pediatric brain cancer immunotherapy, as well as considerations for efficient clinical translation of efficacious immunotherapies into pediatric settings.

[Perspectives for the evolution and use of CAR-T cells]

CAR-T cells have recently made a stunning entry on the arena of immunotherapy of B-cell lymphomas. This new treatment approach represents the culmination of 30 years of efforts to understand the role of T cells in the antitumor response. However, this technology is still in its infancy and suffers from a number of limitations. Many areas for improvement, based in particular on the possibilities of additional genetic manipulations of CAR-T cells, aim at reducing their toxicity, increasing their persistence in vivo, preventing the risk of tumor escape, recruiting other immune effectors, or extending their application to other cancers. Further studies of the dynamic interaction between the patient and these live drugs will allow elucidating the mechanisms determining the antitumor response in this context and thus developing more efficiently the future CAR-T cells.

[T cell-based immunotherapies in solid tumors]

In solid tumors, adoptive T cell therapies based on ex vivo amplification of antitumor T cell are represented by three main complementary approaches : (i) tumor infiltrating lymphocytes (TILs) which are amplified in vitro before reinjection to the patient, (ii) chimeric antigen receptor (CAR) engineered T cells and (iii) T cell receptor (TCR) engineered T cells. Despite encouraging results, some obstacles remain, such as optimal target selection and tumor microenvironment. In this Review, we discuss pros and cons of these different therapeutic strategies that may open new perspectives in the treatment of solid tumors.

Delivery strategies for cell-based therapies in the brain: overcoming multiple barriers

Cell-based therapies to the brain are promising for the treatment of multiple brain disorders including neurodegeneration and cancers. In order to access the brain parenchyma, there are multiple physiological barriers that must be overcome depending on the route of delivery. Specifically, the blood-brain barrier has been a major difficulty in drug delivery for decades, and it still presents a challenge for the delivery of therapeutic cells. Other barriers, including the blood-cerebrospinal fluid barrier and lymphatic-brain barrier, are less explored, but may offer specific challenges or opportunities for therapeutic delivery. Here we discuss the barriers to the brain and the strategies currently in place to deliver cell-based therapies, including engineered T cells, dendritic cells, and stem cells, to treat diseases. With a particular focus on cancers, we also highlight the current ongoing clinical trials that use cell-based therapies to treat disease, many of which show promise at treating some of the deadliest illnesses.

CAR T cell therapy in solid tumors: a short review

Chimeric antigen receptor (CAR) T cell therapy has been established in the treatment of hematological malignancies. However, in solid tumors its efficacy remains limited. The aim of this article is to give an overview of the field of cell therapy itself, to introduce the underlying concepts of CAR T cell-based treatment approaches and to address its limitations in advancing the treatment for solid malignancies.

Immunosuppression in Glioblastoma: Current Understanding and Therapeutic Implications

Glioblastoma (GBM) is the most common primary brain tumor in adults an carries and carries a terrible prognosis. The current regiment of surgical resection, radiation, and chemotherapy has remained largely unchanged in recent years as new therapeutic approaches have struggled to demonstrate benefit. One of the most challenging hurdles to overcome in developing novel treatments is the profound immune suppression found in many GBM patients. This limits the utility of all manner of immunotherapeutic agents, which have revolutionized the treatment of a number of cancers in recent years, but have failed to show similar benefit in GBM therapy. Understanding the mechanisms of tumor-mediated immune suppression in GBM is critical to the development of effective novel therapies, and reversal of this effect may prove key to effective immunotherapy for GBM. In this review, we discuss the current understanding of tumor-mediated immune suppression in GBM in both the local tumor microenvironment and systemically. We also discuss the effects of current GBM therapy on the immune system. We specifically explore some of the downstream effectors of tumor-driven immune suppression, particularly myeloid-derived suppressor cells (MDSCs) and other immunosuppressive monocytes, and the manner by which GBM induces their formation, with particular attention to the role of GBM-derived extracellular vesicles (EVs). Lastly, we briefly review the current state of immunotherapy for GBM and discuss additional hurdles to overcome identification and implementation of effective therapeutic strategies.

Engineered CAR-T and novel CAR-based therapies to fight the immune evasion of glioblastoma: gutta cavat lapidem

INTRODUCTION

The field of cancer immunotherapy has achieved great advancements through the application of genetically engineered T cells with chimeric antigen receptors (CAR), that have shown exciting success in eradicating hematologic malignancies and have proved to be safe with promising early signs of antitumoral activity in the treatment of glioblastoma (GBM).

AREAS COVERED

We discuss the use of CAR T cells in GBM, focusing on limitations and obstacles to advancement, mostly related to toxicities, hostile tumor microenvironment, limited CAR T cells infiltration and persistence, target antigen loss/heterogeneity and inadequate trafficking. Furthermore, we introduce the refined strategies aimed at strengthening CAR T activity and offer insights in to novel immunotherapeutic approaches, such as the potential use of CAR NK or CAR M to optimize anti-tumor effects for GBM management.

EXPERT OPINION

With the progressive wide use of CAR T cell therapy, significant challenges in treating solid tumors, including central nervous system (CNS) tumors, are emerging, highlighting early disease relapse and cancer cell resistance issues, owing to hostile immunosuppressive microenvironment and tumor antigen heterogeneity. In addition to CAR T cells, there is great interest in utilizing other types of CAR-based therapies, such as CAR natural killer (CAR NK) or CAR macrophages (CAR M) cells for CNS tumors.

A review of neurotoxicities associated with immunotherapy and a framework for evaluation

Immuno-oncology agents, including immune checkpoint inhibitors (ICIs) and chimeric antigen receptor T (CAR-T) cell therapies, are increasing in use for a growing list of oncologic indications. While harnessing the immune system against cancer cells has a potent anti-tumor effect, it can also cause widespread autoimmune toxicities that limit therapeutic potential. Neurologic toxicities have unique presentations and can progress rapidly, necessitating prompt recognition. In this article, we review the spectrum of central and peripheral neurologic immune-related adverse events (irAEs) associated with ICI therapies, emphasizing a diagnostic framework that includes consideration of the therapy regimen, timing of symptom onset, presence of non-neurologic irAEs, pre-existing neurologic disease, and syndrome specific features. In addition, we review the immune effector cell-associated neurotoxicity syndrome (ICANS) associated with CAR-T cell therapy and address diagnostic challenges specific to patients with brain metastases. As immunotherapy use grows, so too will the number of patients affected by neurotoxicity. There is an urgent need to understand pathogenic mechanisms, predictors, and optimal treatments of these toxicities, so that we can manage them without sacrificing anti-tumor efficacy.

Facing CAR T Cell Challenges on the Deadliest Paediatric Brain Tumours

Central nervous system (CNS) tumours comprise 25% of the paediatric cancer diagnoses and are the leading cause of cancer-related death in children. Current treatments for paediatric CNS tumours are far from optimal and fail for those that relapsed or are refractory to treatment. Besides, long-term sequelae in the developing brain make it mandatory to find new innovative approaches. Chimeric antigen receptor T cell (CAR T) therapy has increased survival in patients with B-cell malignancies, but the intrinsic biological characteristics of CNS tumours hamper their success. The location, heterogeneous antigen expression, limited infiltration of T cells into the tumour, the selective trafficking provided by the blood-brain barrier, and the immunosuppressive tumour microenvironment have emerged as the main hurdles that need to be overcome for the success of CAR T cell therapy. In this review, we will focus mainly on the characteristics of the deadliest high-grade CNS paediatric tumours (medulloblastoma, ependymoma, and high-grade gliomas) and the potential of CAR T cell therapy to increase survival and patients' quality of life.

Cell Therapy for Colorectal Cancer: The Promise of Chimeric Antigen Receptor (CAR)-T Cells

Colorectal cancer (CRC) is a global public health problem as it is the third most prevalent and the second most lethal cancer worldwide. Major efforts are underway to understand its molecular pathways as well as to define the tumour-associated antigens (TAAs) and tumour-specific antigens (TSAs) or neoantigens, in order to develop an effective treatment. Cell therapies are currently gaining importance, and more specifically chimeric antigen receptor (CAR)-T cell therapy, in which genetically modified T cells are redirected against the tumour antigen of interest. This immunotherapy has emerged as one of the most promising advances in cancer treatment, having successfully demonstrated its efficacy in haematological malignancies. However, in solid tumours, such as colon cancer, it is proving difficult to achieve the same results due to the shortage of TSAs, on-target off-tumour effects, low CAR-T cell infiltration and the immunosuppressive microenvironment. To address these challenges in CRC, new approaches are proposed, including combined therapies, the regional administration of CAR-T cells and more complex CAR structures, among others. This review comprehensively summarises the current landscape of CAR-T cell therapy in CRC from the potential tumour targets to the preclinical studies and clinical trials, as well as the limitations and future perspectives of this novel antitumour strategy.

GD2 CAR T cells against human glioblastoma

Glioblastoma is the most malignant primary brain tumor and is still in need of effective medical treatment. We isolated patient-derived glioblastoma cells showing high GD2 antigen expression representing a potential target for CAR T strategy. Data highlighted a robust GD2 CAR antitumor potential in 2D and 3D glioblastoma models associated with a significant and CAR T-restricted increase of selected cytokines. Interestingly, immunosuppressant TGF β1, expressed in all co-cultures, did not influence antitumor activity. The orthotopic NOD/SCID models using primary glioblastoma cells reproduced human histopathological features. Considering still-conflicting data on the delivery route for targeting brain tumors, we compared intracerebral versus intravenous CAR T injections. We report that the intracerebral route significantly increased the length of survival time in a dose-dependent manner, without any side effects. Collectively, the proposed anti-GD2 CAR can counteract human glioblastoma potentially opening a new therapeutic option for a still incurable cancer.

Fibrin gel enhances the antitumor effects of chimeric antigen receptor T cells in glioblastoma

Regional delivery of chimeric antigen receptor (CAR) T cells in glioblastoma represents a rational therapeutic approach as an alternative to intravenous administration to avoid the blood-brain barrier impediment. Here, we developed a fibrin gel that accommodates CAR-T cell loading and promotes their gradual release. Using a model of subtotal glioblastoma resection, we demonstrated that the fibrin-based gel delivery of CAR-T cells within the surgical cavity enables superior antitumor activity compared to CAR-T cells directly inoculated into the tumor resection cavity.

Fn14-targeted BiTE and CAR-T cells demonstrate potent preclinical activity against glioblastoma

T cell-engaging therapies involving bispecific T cell engager (BiTE) and chimeric antigen receptor T (CAR-T) cells have achieved great success in the treatment of hematological tumors. However, the paucity of ideal cell surface molecules that can be targeted on glioblastoma (GBM) partially reduces the immunotherapeutic efficacy. Recently, high expression of Fn14 has been reported in several solid tumors, so the strategy of exploiting this specific antigen for GBM immunotherapy is worth studying. Consequently, we constructed Fn14× CD3 BiTE and Fn14-specific CAR-T cells and investigated their cytotoxic activity against GBM in vitro and in vivo. First, expression of Fn14 was confirmed in glioma tissues and GBM cells. Then, we designed Fn14-specific BiTE and CAR-T cells and tested their cytotoxicity in GBM cell cultures and mouse models of GBM. Fn14 was highly expressed in GBM tissues and cell lines, while it was undetectable in normal brain samples. Fn14× CD3 BiTE, Fn14 CAR-T cells and Fn14 CAR-T/IL-15 cells were antigen-specific and highly cytotoxic, showing good antitumor activity in vitro and causing significant regression of established solid tumors in xenograft models. However, the xenografts treated with Fn14 CAR-T cells regrew, whereas xenografts treated with Fn14 CAR-T/IL-15 cells did not. IL-15 engineering augmented the antitumor activity of Fn14 CAR-T cells and resulted in significant antitumor effects similar to those of Fn14× CD3 BiTE. Our results suggest that Fn14 is an appropriate target for GBM. Anti-Fn14 BiTE and Fn14-specific CAR-T/IL-15 cells may be exciting immunotherapeutic options for malignant brain cancer.

The Challenges and Future of Immunotherapy for Gliomas

ABSTRACT

Gliomas and glioblastoma comprise the majority of brain malignancies and are difficult to treat despite standard of care and advances in immunotherapy. The challenges of controlling glioma growth and recurrence involve the uniquely immunosuppressive tumor microenvironment and systemic blunting of immune responses. In addition to highlighting key features of glioma and glioblastoma composition and immunogenicity, this review presents several future directions for immunotherapy, such as vaccines and synergistic combination treatment regimens, to better combat these tumors.

Chimeric antigen receptor (CAR) immunotherapy: basic principles, current advances, and future prospects in neuro-oncology

With recent advances, chimeric antigen receptor (CAR) immunotherapy has become a promising modality for patients with refractory cancer diseases. The successful results of CAR T cell therapy in relapsed and refractory B-cell malignancies shifted the paradigm of cancer immunotherapy by awakening the scientific, clinical, and commercial interest in translating this technology for the treatment of solid cancers. This review elaborates on fundamental principles of CAR T cell therapy (development of CAR construct, challenges of CAR T cell therapy) and its application on solid tumors as well as CAR T cell therapy potential in the field of neuro-oncology. Glioblastoma (GBM) is identified as one of the most challenging solid tumors with a permissive immunological milieu and dismal prognosis. Standard multimodal treatment using maximal safe resection, radiochemotherapy, and maintenance chemotherapy extends the overall survival beyond a year. Recurrence is, however, inevitable. GBM holds several unique features including its vast intratumoral heterogeneity, immunosuppressive environment, and a partially permissive anatomic blood–brain barrier, which offers a unique opportunity to investigate new treatment approaches. Tremendous efforts have been made in recent years to investigate novel CAR targets and target combinations with standard modalities for solid tumors and GBM to improve treatment efficacy. In this review, we outline the history of CAR immunotherapy development, relevant CAR target antigens validated with CAR T cells as well as preclinical approaches in combination with adjunct approaches via checkpoint inhibition, bispecific antibodies, and second-line systemic therapies that enhance anticancer efficacy of the CAR-based cancer immunotherapy.

Prognostic Gene Expression Signature in Patients With Distinct Glioma Grades

Background

Glioma is the most common type of primary brain tumor in adults. Patients with the most malignant form have an overall survival time of <16 months. Although considerable progress has been made in defining the adapted therapeutic strategies, measures to counteract tumor escape have not kept pace, due to the developed resistance of malignant glioma. In fact, identifying the nature and role of distinct tumor-infiltrating immune cells in glioma patients would decipher potential mechanisms behind therapy failure.

Methods

We integrated into our study glioma transcriptomic datasets from the Cancer Genome Atlas (TCGA) cohort (154 GBM and 516 LGG patients). LM22 immune signature was built using CIBERSORT. Hierarchical clustering and UMAP dimensional reduction algorithms were applied to identify clusters among glioma patients either in an unsupervised or supervised way. Furthermore, differential gene expression (DGE) has been performed to unravel the top expressed genes among the identified clusters. Besides, we used the least absolute shrinkage and selection operator (LASSO) and Cox regression algorithm to set up the most valuable prognostic factor.

Results

Our study revealed, following gene enrichment analysis, the presence of two distinct groups of patients. The first group, defined as cluster 1, was characterized by the presence of immune cells known to exert efficient antitumoral immune response and was associated with better patient survival, whereas the second group, cluster 2, which exhibited a poor survival, was enriched with cells and molecules, known to set an immunosuppressive pro-tumoral microenvironment. Interestingly, we revealed that gene expression signatures were also consistent with each immune cluster function. A strong presence of activated NK cells was revealed in cluster 1. In contrast, potent immunosuppressive components such as regulatory T cells, neutrophils, and M0/M1/M2 macrophages were detected in cluster 2, where, in addition, inhibitory immune checkpoints, such as PD-1, CTLA-4, and TIM-3, were also significantly upregulated. Finally, Cox regression analysis further corroborated that tumor-infiltrating cells from cluster 2 exerted a significant impact on patient prognosis.

Conclusion

Our work brings to light the tight implication of immune components on glioma patient prognosis. This would contribute to potentially developing better immune-based therapeutic approaches.

Blood-Brain Barrier, Cell Junctions, and Tumor Microenvironment in Brain Metastases, the Biological Prospects and Dilemma in Therapies

Brain metastasis is the most commonly seen brain malignancy, frequently originating from lung cancer, breast cancer, and melanoma. Brain tumor has its unique cell types, anatomical structures, metabolic constraints, and immune environment, which namely the tumor microenvironment (TME). It has been discovered that the tumor microenvironment can regulate the progression, metastasis of primary tumors, and response to the treatment through the particular cellular and non-cellular components. Brain metastasis tumor cells that penetrate the brain–blood barrier and blood–cerebrospinal fluid barrier to alter the function of cell junctions would lead to different tumor microenvironments. Emerging evidence implies that these tumor microenvironment components would be involved in mechanisms of immune activation, tumor hypoxia, antiangiogenesis, etc. Researchers have applied various therapeutic strategies to inhibit brain metastasis, such as the combination of brain radiotherapy, immune checkpoint inhibitors, and monoclonal antibodies. Unfortunately, they hardly access effective treatment. Meanwhile, most clinical trials of target therapy patients with brain metastasis are always excluded. In this review, we summarized the clinical treatment of brain metastasis in recent years, as well as their influence and mechanisms underlying the differences between the composition of tumor microenvironments in the primary tumor and brain metastasis. We also look forward into the feasibility and superiority of tumor microenvironment-targeted therapies in the future, which may help to improve the strategy of brain metastasis treatment.

Treatment-Related Adverse Events of Chimeric Antigen Receptor T-Cell (CAR T) in Clinical Trials: A Systematic Review and Meta-Analysis

Simple Summary

Successful treatment of hematological malignancies with chimeric antigen receptors T (CAR-T) cells has led to much enthusiasm for the wide clinical usage and development of novel CAR-T therapies. However, it also challenges physicians and investigators to recognize and deal with treatment-associated toxicities. We conducted a systematic review and meta-analysis from 84 eligible study and a total of 2592 patients to identify the comprehensive incidences and severity of CRS and neurological symptoms (NS) as well as the potential differences in AEs across a variety of cancer types, CAR-T targets, and other factors, thereby offering a significant implication on its future application and research.

Abstract

Chimeric antigen receptors T (CAR-T) cell therapy of cancer is a rapidly evolving field. It has been shown to be remarkably effective in cases of hematological malignancies, and its approval by the FDA has significantly increased the enthusiasm for wide clinical usage and development of novel CAR-T therapies. However, it has also challenged physicians and investigators to recognize and deal with treatment-associated toxicities. A total of 2592 patients were included from 84 eligible studies that were systematically searched and reviewed from the databases of PubMed, de, the American Society of Hematology and the Cochrane Library. The meta-analysis and subgroup analysis by a Bayesian logistic regression model were used to evaluate the incidences of therapy-related toxicities such as cytokine release syndrome (CRS) and neurological symptoms (NS), and the differences between different targets and cancer types were analyzed. The pooled all-grade CRS rate and grade ≥ 3 CRS rate was 77% and 29%, respectively, with a significantly higher incidence in the hematologic malignancies (all-grade: 81%; grade ≥ 3: 29%) than in solid tumors (all-grade: 37%; grade ≥ 3: 19%). The pooled estimate NS rate from the individual studies were 40% for all-grade and 28% for grade ≥ 3. It was also higher in the hematologic subgroup than in the solid tumors group. The subgroup analysis by cancer type showed that higher incidences of grade ≥ 3 CRS were observed in anti-CD19 CAR-T therapy for ALL and NHL, anti-BCMA CAR-T for MM, and anti-CEA CAR-T for solid tumors, which were between 24–36%, while higher incidences of grade ≥ 3 NS were mainly observed in CD19-ALL/NHL (23–37%) and BCMA-MM (12%). Importantly, subgroup analysis on anti-CD19 CAR-T studies showed that young patients (vs. adult patients), allologous T cell origin (vs. autologous origin), gamma retrovirus vector, and higher doses of CAR-T cells were associated with high-grade CRS. On the other hand, the patients with NHL (vs ALL), administered with higher dose of CAR-T, and adult patients (vs. young patients) had an increased incidence of grade ≥ 3 NS events. This study offers a comprehensive summary of treatment-related toxicity and will guide future clinical trials and therapeutic designs investigating CAR T cell therapy.

Chimeric Antigen Receptor T-Cell Therapy: Updates in Glioblastoma Treatment

Glioblastoma multiforme (GBM) are the most common and among the deadliest brain tumors in adults. Current mainstay treatments are insufficient to treat this tumor, and therefore, more effective therapies are desperately needed. Immunotherapy, which takes advantage of the body's natural defense mechanism, is an exciting emerging field in neuro-oncology. Adoptive cell therapy with chimeric antigen receptor (CAR) T cells provides a treatment strategy based on using patients' own selected and genetically engineered cells that target tumor-associated antigens. These cells are harvested from patients, modified to target specific proteins expressed by the tumor, and re-introduced into the patient with the goal of destroying tumor cells. Here, we review the history of CAR T-cell therapy, and describe the characteristics of various generations of CAR T therapies, and the challenges inherent to treatment of GBM. Finally, we describe recent and current CAR T clinical trials designed to combat GBM.

Identification of neoantigen-reactive T lymphocytes in the peripheral blood of a patient with glioblastoma

The adoptive transfer of naturally occurring T cells that recognize cancer neoantigens has led to durable tumor regressions in select patients with cancer. However, it remains unknown whether such T cells can be isolated from and used to treat patients with glioblastoma, a cancer that is refractory to currently available therapies. To answer this question, we stimulated patient blood-derived memory T cells in vitro using peptides and minigenes that represented point mutations unique to patients’ tumors (ie, candidate neoantigens) and then tested their ability to specifically recognize these mutations. In a cohort of five patients with glioblastoma, we found that circulating CD4⁺ memory T cells from one patient recognized a cancer neoantigen harboring a mutation in the EED gene (EED^H189N) that was unique to that patient’s tumor. This finding suggests that neoantigen-reactive T cells could indeed be isolated from patients with glioblastoma, thereby providing a rationale for further efforts to develop neoantigen-directed adoptive T cell therapy for this disease.

Exploiting Single-Cell Tools in Gene and Cell Therapy

Single-cell molecular tools have been developed at an incredible pace over the last five years as sequencing costs continue to drop and numerous molecular assays have been coupled to sequencing readouts. This rapid period of technological development has facilitated the delineation of individual molecular characteristics including the genome, transcriptome, epigenome, and proteome of individual cells, leading to an unprecedented resolution of the molecular networks governing complex biological systems. The immense power of single-cell molecular screens has been particularly highlighted through work in systems where cellular heterogeneity is a key feature, such as stem cell biology, immunology, and tumor cell biology. Single-cell-omics technologies have already contributed to the identification of novel disease biomarkers, cellular subsets, therapeutic targets and diagnostics, many of which would have been undetectable by bulk sequencing approaches. More recently, efforts to integrate single-cell multi-omics with single cell functional output and/or physical location have been challenging but have led to substantial advances. Perhaps most excitingly, there are emerging opportunities to reach beyond the description of static cellular states with recent advances in modulation of cells through CRISPR technology, in particular with the development of base editors which greatly raises the prospect of cell and gene therapies. In this review, we provide a brief overview of emerging single-cell technologies and discuss current developments in integrating single-cell molecular screens and performing single-cell multi-omics for clinical applications. We also discuss how single-cell molecular assays can be usefully combined with functional data to unpick the mechanism of cellular decision-making. Finally, we reflect upon the introduction of spatial transcriptomics and proteomics, its complementary role with single-cell RNA sequencing (scRNA-seq) and potential application in cellular and gene therapy.

Advances in Immunotherapy for Adult Glioblastoma

Simple Summary

Therapy failure and disease recurrence are hallmarks of glioblastoma (GBM), the most common and lethal tumor in adults that originates in the brain. Despite aggressive standards of care, tumor recurrence is inevitable with no standardized second-line therapy. Recent clinical studies evaluating therapies that augment the anti-tumor immune response (i.e., immunotherapies) have yielded promising results in subsets of GBM patients. Here, we summarize clinical studies in the past decade that evaluate vaccines, immune checkpoint inhibitors and chimeric antigen receptor (CAR) T cells for treatment of GBM. Although immunotherapies have yet to return widespread efficacy for the majority of GBM patients, critical insights from completed and ongoing clinical trials are informing development of the next generation of therapies, with the goal to alleviate disease burden and extend patient survival.

Abstract

Despite aggressive multimodal therapy, glioblastoma (GBM) remains the most common malignant primary brain tumor in adults. With the advent of therapies that revitalize the anti-tumor immune response, several immunotherapeutic modalities have been developed for treatment of GBM. In this review, we summarize recent clinical and preclinical efforts to evaluate vaccination strategies, immune checkpoint inhibitors (ICIs) and chimeric antigen receptor (CAR) T cells. Although these modalities have shown long-term tumor regression in subsets of treated patients, the underlying biology that may predict efficacy and inform therapy development is being actively investigated. Common to all therapeutic modalities are fundamental mechanisms of therapy evasion by tumor cells, including immense intratumoral heterogeneity, suppression of the tumor immune microenvironment and low mutational burden. These insights have led efforts to design rational combinatorial therapies that can reignite the anti-tumor immune response, effectively and specifically target tumor cells and reliably decrease tumor burden for GBM patients.

Toward precision immunotherapy using multiplex immunohistochemistry and in silico methods to define the tumor immune microenvironment

Recent developments in cancer immunotherapy promise better outcomes for cancer patients, although clinical trials for difficult to treat cancers such as malignant brain cancer present special challenges, showing little response to first generation immunotherapies. Reasons for differences in immunotherapy response in some cancer types are likely due to the nature of tumor microenvironment, which harbors multiple cell types which interact with tumor cells to establish immunosuppression. The cell types which appear to hold the key in regulating tumor immunosuppression are the tumor-infiltrating immune cells. The current standard treatment for difficult to treat cancer, including the most malignant brain cancer, glioblastoma, continues to offer a bleak outlook for patients. Immune-profiling and correlation with pathological and clinical data will lead to a deeper understanding of the tumor immune microenvironment and contribute toward the selection, optimization and development of novel precision immunotherapies. Here, we review the current understanding of the tumor microenvironmental landscape in glioblastoma with a focus on next-generation technologies including multiplex immunofluorescence and computational approaches to map the brain tumor microenvironment to decipher the role of the immune system in this lethal malignancy.

Novel Receptor Tyrosine Kinase Pathway Inhibitors for Targeted Radionuclide Therapy of Glioblastoma

Glioblastoma (GB) remains the most fatal brain tumor characterized by a high infiltration rate and treatment resistance. Overexpression and/or mutation of receptor tyrosine kinases is common in GB, which subsequently leads to the activation of many downstream pathways that have a critical impact on tumor progression and therapy resistance. Therefore, receptor tyrosine kinase inhibitors (RTKIs) have been investigated to improve the dismal prognosis of GB in an effort to evolve into a personalized targeted therapy strategy with a better treatment outcome. Numerous RTKIs have been approved in the clinic and several radiopharmaceuticals are part of (pre)clinical trials as a non-invasive method to identify patients who could benefit from RTKI. The latter opens up the scope for theranostic applications. In this review, the present status of RTKIs for the treatment, nuclear imaging and targeted radionuclide therapy of GB is presented. The focus will be on seven tyrosine kinase receptors, based on their central role in GB: EGFR, VEGFR, MET, PDGFR, FGFR, Eph receptor and IGF1R. Finally, by way of analyzing structural and physiological characteristics of the TKIs with promising clinical trial results, four small molecule RTKIs were selected based on their potential to become new therapeutic GB radiopharmaceuticals.

Current progress in chimeric antigen receptor T cell therapy for glioblastoma multiforme

Glioblastoma multiforme (GBM) is one of the deadliest brain tumors with an unfavorable prognosis and overall survival of approximately 20 months following diagnosis. The current treatment for GBM includes surgical resections and chemo‐ and radiotherapeutic modalities, which are not effective. CAR‐T immunotherapy has been proven effective for CD19‐positive blood malignancies, and the application of CAR‐T cell therapy for solid tumors including GBM offers great hope for this aggressive tumor which has a limited response to current treatments. CAR‐T technology depends on the use of patient‐specific T cells genetically engineered to express specific tumor‐associated antigens (TAAs). Interaction of CAR‐T cells with tumor cells triggers the destruction/elimination of these cells by the induction of cytotoxicity and the release of different cytokines. Despite the great promise of CAR‐T cell‐based therapy several challenges exist. These include the heterogeneity of GBM cancer cells, aberrant various signaling pathways involved in tumor progression, antigen escape, the hostile inhibitory GBM microenvironment, T cell dysfunction, blood‐brain barrier, and defective antigen presentation. All need to be addressed before full application at the clinical level can begin. Herein we provide a focused review of the rationale for the use of different types of CAR‐T cells (including FcγRs), the different GBM‐associated antigens, the challenges still facing CAR‐T‐based therapy, and means to overcome such challenges. Finally, we enumerate currently completed and ongoing clinical trials, highlighting the different ways such trials are designed to overcome specific problems. Exploitation of the full potential of CAR‐T cell therapy for GBM depends on their solution.

The multifactorial roles of microglia and macrophages in the maintenance and progression of glioblastoma

The functional characteristics of glial cells, in particular microglia, have attained considerable importance in several diseases, including glioblastoma, the most hostile and malignant type of intracranial tumor. Microglia performs a highly significant role in the brain's inflammatory response mechanism. They exhibit anti-tumor properties via phagocytosis and the activation of a number of different cytotoxic substances. Some tumor-derived factors, however, transform these microglial cells into immunosuppressive and tumor-supportive, facilitating survival and progression of tumorigenic cells. Glioma-associated microglia and/or macrophages (GAMs) accounts for a large proportion of glioma infiltrating cells. Once within the tumor, GAMs exhibit a distinct phenotype of initiation that subsequently supports the growth and development of tumorigenic cells, angiogenesis and stimulates the infiltration of healthy brain regions. Interventions that suppress or prohibit the induction of GAMs at the tumor site or attenuate their immunological activities accommodating anti-tumor actions are likely to exert positive impact on glioblastoma treatment. In the present paper, we aim to summarize the most recent knowledge of microglia and its physiology, as well as include a very brief description of different molecular factors involved in microglia and glioblastoma interplay. We further address some of the major signaling pathways that regulate the baseline motility of glioblastoma progression. Finally, we discussed a number of therapeutic approaches regarding glioblastoma treatment.

Innovative and Promising Strategies to Enhance Effectiveness of Immunotherapy for CNS Tumors: Where Are We?

Although there are several immunotherapy approaches for the treatment of Central Nervous System (CNS) tumors under evaluation, currently none of these approaches have received approval from the regulatory agencies. CNS tumors, especially glioblastomas, are tumors characterized by highly immunosuppressive tumor microenvironment, limiting the possibility of effectively eliciting an immune response. Moreover, the peculiar anatomic location of these tumors poses relevant challenges in terms of safety, since uncontrolled hyper inflammation could lead to cerebral edema and cranial hypertension. The most promising strategies of immunotherapy in neuro-oncology consist of the use of autologous T cells redirected against tumor cells through chimeric antigen receptor (CAR) constructs or genetically modified T-cell receptors. Trials based on native or genetically engineered oncolytic viruses and on vaccination with tumor-associated antigen peptides are also under evaluation. Despite some sporadic complete remissions achieved in clinical trials, the outcome of patients with CNS tumors treated with different immunotherapeutic approaches remains poor. Based on the lessons learned from these unsatisfactory experiences, novel immune-therapy approaches aimed at overcoming the profound immunosuppressive microenvironment of these diseases are bringing new hope to reach the cure for CNS tumors.

CAR T Cell-Based Immunotherapy for the Treatment of Glioblastoma

Glioblastoma multiforme (GBM) is the most common and aggressive malignant primary brain tumor in adults. Current treatment options typically consist of surgery followed by chemotherapy or more frequently radiotherapy, however, median patient survival remains at just over 1 year. Therefore, the need for novel curative therapies for GBM is vital. Characterization of GBM cells has contributed to identify several molecules as targets for immunotherapy-based treatments such as EGFR/EGFRvIII, IL13Rα2, B7-H3, and CSPG4. Cytotoxic T lymphocytes collected from a patient can be genetically modified to express a chimeric antigen receptor (CAR) specific for an identified tumor antigen (TA). These CAR T cells can then be re-administered to the patient to identify and eliminate cancer cells. The impressive clinical responses to TA-specific CAR T cell-based therapies in patients with hematological malignancies have generated a lot of interest in the application of this strategy with solid tumors including GBM. Several clinical trials are evaluating TA-specific CAR T cells to treat GBM. Unfortunately, the efficacy of CAR T cells against solid tumors has been limited due to several factors. These include the immunosuppressive tumor microenvironment, inadequate trafficking and infiltration of CAR T cells and their lack of persistence and activity. In particular, GBM has specific limitations to overcome including acquired resistance to therapy, limited diffusion across the blood brain barrier and risks of central nervous system toxicity. Here we review current CAR T cell-based approaches for the treatment of GBM and summarize the mechanisms being explored in pre-clinical, as well as clinical studies to improve their anti-tumor activity.

Are chimeric antigen receptor T cells (CAR-T cells) the future in immunotherapy for autoimmune diseases?

OBJECTIVE

CAR-T cell therapy has revolutionized the treatment of oncological diseases, and potential uses in autoimmune diseases have recently been described. The review aims to integrate the available data on treatment with CAR-T cells, emphasizing autoimmune diseases, to determine therapeutic advances and their possible future clinical applicability in autoimmunity.

MATERIALS AND METHODS

A search was performed in PubMed with the keywords "Chimeric Antigen Receptor" and "CART cell". The documents of interest were selected, and a critical review of the information was carried out.

RESULTS

In the treatment of autoimmune diseases, in preclinical models, three different cellular strategies have been used, which include Chimeric antigen receptor T cells, Chimeric autoantibody receptor T cells, and Chimeric antigen receptor in regulatory T lymphocytes. All three types of therapy have been effective. The potential adverse effects within them, cytokine release syndrome, cellular toxicity and neurotoxicity must always be kept in mind.

CONCLUSIONS

Although information in humans is not yet available, preclinical models of CAR-T cells in the treatment of autoimmune diseases show promising results, so that in the future, they may become a useful and effective therapy in the treatment of these pathologies.

CAR T-Cells for CNS Lymphoma: Driving into New Terrain?

Primary CNS lymphomas (PCNSL) represent a group of extranodal non-Hodgkin lymphomas and secondary CNS lymphomas refer to secondary involvement of the neuroaxis by systemic disease. CNS lymphomas are associated with limited prognosis even after aggressive multimodal therapy. Chimeric antigen receptor (CAR) T-cells have proven as a promising therapeutic avenue in hematological B-cell malignancies including diffuse large B-cell lymphoma, B-cell acute lymphoblastic leukemia, and mantle-cell lymphoma. CARs endow an autologous T-cell population with MHC-unrestricted effectivity against tumor target antigens such as the pan B-cell marker CD19. In PCNSL, compelling and long-lasting anti-tumor effects of such therapy have been shown in murine immunocompromised models. In clinical studies on CAR T-cells for CNS lymphoma, only limited data are available and often include both patients with PCNSL but also patients with secondary CNS lymphoma. Several clinical trials on CAR T-cell therapy for primary and secondary CNS lymphoma are currently ongoing. Extrapolated from the available preliminary data, an overall acceptable safety profile with considerable anti-tumor effects might be expected. Whether these beneficial anti-tumor effects are as long-lasting as in animal models is currently in doubt; and the immunosuppressive tumor microenvironment of the brain may be among the most pivotal factors limiting efficacy of CAR T-cell therapy in CNS lymphoma. Based on an increasing understanding of CAR T-cell interactions with the tumor cells as well as the cerebral tissue, modifications of CAR design or the combination of CAR T-cell therapy with other therapeutic approaches may aid to release the full therapeutic efficiency of CAR T-cells. CAR T-cells may therefore emerge as a novel treatment strategy in primary and secondary CNS lymphoma.

Chimeric Antigen Receptor T Cells for Glioblastoma: Current Concepts, Challenges, and Future Perspectives

Glioblastoma is the most common malignant primary brain tumor and is associated with a poor prognosis even after multimodal therapy. Chimeric antigen receptor (CAR) T cells have emerged as a promising therapeutic avenue in glioblastoma. CARs incorporate antigen-recognition moieties that endow autologous T cells with specificity against antigens expressed on glioblastoma (e.g., interleukin [IL]-13Rα2, epidermal growth factor receptor variant III [EGFRvIII], and human epidermal growth factor receptor 2 [HER2]). Compelling antitumor effects of such therapy have been shown in murine glioblastoma models. In humans, 5 phase I/II studies on IL-13Rα2-, EGFRvIII-, and HER2-directed CAR T cells for the treatment of glioblastoma have been published suggesting an acceptable safety profile. However, antitumor effects fell short of expectations in these initial clinical studies. Tumor heterogeneity, antigen loss, and the immunosuppressive tumor microenvironment are among the most important factors to limit the efficacy of CAR T-cell therapy in glioblastoma. Novel target antigens, modification of CAR T-cell design, the combination of CAR T-cell therapy with other therapeutic approaches, but also the use of CAR natural killer cells or CAR macrophages may optimize antitumor effects. Numerous clinical trials studying such approaches are ongoing, as well as several preclinical studies. With an increasing understanding of immune-escape mechanisms of glioblastoma and novel manufacturing techniques for CARs, CAR T cells may provide clinically relevant activity in glioblastoma. This review focuses on the use of CAR T cells in glioblastoma, but also introduces the basic structure, mechanisms of action, and relevant side effects of CAR T cells.

Immunotherapy for Glioblastoma: Current Progress and Challenge

Glioblastoma is a highly lethal brain cancer with a median survival rate of less than 15 months when treated with the current standard of care, which consists of surgery, radiotherapy and chemotherapy. With the recent success of immunotherapy in other aggressive cancers such as advanced melanoma and advanced non-small cell lung cancer, glioblastoma has been brought to the forefront of immunotherapy research. Resistance to therapy has been a major challenge across a multitude of experimental candidates and no immunotherapies have been approved for glioblastoma to-date. Intra- and inter-tumoral heterogeneity, an inherently immunosuppressive environment and tumor plasticity remain barriers to be overcome. Moreover, the unique tissue-specific interactions between the central nervous system and the peripheral immune system present an additional challenge for immune-based therapies. Nevertheless, there is sufficient evidence that these challenges may be overcome, and immunotherapy continues to be actively pursued in glioblastoma. Herein, we review the primary ongoing immunotherapy candidates for glioblastoma with a focus on immune checkpoint inhibitors, myeloid-targeted therapies, vaccines and chimeric antigen receptor (CAR) immunotherapies. We further provide insight on mechanisms of resistance and how our understanding of these mechanisms may pave the way for more effective immunotherapeutics against glioblastoma.

Novel high-affinity EGFRvIII-specific chimeric antigen receptor T cells effectively eliminate human glioblastoma

Objectives

The increasing success of Chimeric Antigen Receptor (CAR) T cell therapy in haematological malignancies is reinvigorating its application in many other cancer types and with renewed focus on its application to solid tumors. We present a novel CAR against glioblastoma, an aggressive, malignant glioma, with a dismal survival rate for which treatment options have remained unchanged for over a decade.

Methods

We use the human Retained Display (ReD) antibody platform (Myrio Therapeutics) to identify a novel single‐chain variable fragment (scFv) that recognises epidermal growth factor receptor mutant variant III (EGFRvIII), a common and tumor‐specific mutation found in glioblastoma. We use both in vitro functional assays and an in vivo orthotopic xenograft model of glioblastoma to examine the function of our novel CAR, called GCT02, targeted using murine CAR T cells.

Results

Our EGFRvIII‐specific scFv was found to be of much higher affinity than reported comparators reverse‐engineered from monoclonal antibodies. Despite the higher affinity, GCT02 CAR T cells kill equivalently but secrete lower amounts of cytokine. In addition, GCT02‐CAR T cells also mediate rapid and complete tumor elimination in vivo.

Conclusion

We present a novel EGFRvIII‐specific CAR, with effective antitumor functions both in in vitro and in a xenograft model of human glioblastoma.

Case Report: Prolonged Survival Following EGFRvIII CAR T Cell Treatment for Recurrent Glioblastoma

Autologous chimeric antigen receptor (CAR) T cells targeted to epidermal growth factor receptor variant III (CAR T-EGFRvIII) have been developed and administered experimentally to treat patients with IDH1 wildtype recurrent glioblastoma (rGBM) (NCT02209376). We report the case of a 59-year-old patient who received a single peripheral infusion of CAR T-EGFRvIII cells and survived 36 months after disease recurrence, exceeding expected survival for recurrent glioblastoma. Post-infusion histopathologic analysis of tissue obtained during a second stage surgical resection revealed immunosuppressive adaptive changes in the tumor tissue as well as reduced EGFRvIII expression. Serial brain imaging demonstrated a significant reduction in relative cerebral blood volume (rCBV), a measure strongly associated with tumor proliferative activity, at early time points following CAR T treatment. Notably, CAR T-EGFRvIII cells persisted in her peripheral circulation during 29 months of follow-up, the longest period of CAR T persistence reported in GBM trials to date. These findings in a long-term survivor show that peripherally administered CAR T-EGFRvIII cells can persist for years in the circulation and suggest that this cell therapy approach could be optimized to achieve broader efficacy in recurrent GBM patients.

Immunotherapy and radiation for high-grade glioma: a narrative review

Glioblastoma and other high-grade gliomas (HGGs) are the most common and deadly primary brain tumors. Due to recent advances in immunotherapy and improved clinical outcomes in other disease sites, the study of immunotherapy in HGG has increased significantly. Herein, we summarize and evaluate existing evidence and ongoing clinical trials investigating the use of immunotherapy in the treatment of HGG, including therapeutic vaccination, immune checkpoint inhibition, adoptive lymphocyte transfer, and combinatorial approaches utilizing radiation and multiple modalities of immunotherapy. Special attention is given to the mechanisms by which radiation may improve immunogenicity in HGG, why this motivates the study of radiation in combination with immunotherapy, and how to determine optimal dosing and scheduling of radiation. Though larger randomized controlled trials have not consistently shown improvements in clinical outcomes, this area of research is still in its early stages and a number of important lessons can be taken away from the studies that have been completed to date. Many studies found a subset of patients who experienced durable responses, and analysis of their immune cells and tumor cells can be used to identify biomarkers that predict therapeutic response, as well as additional glioma-specific targets that can enhance therapeutic efficacy in a challenging tumor type.

CAR-T cells and BiTEs in solid tumors: challenges and perspectives

Chimeric antigen receptor (CAR)-modified T cells and BiTEs are both immunotherapies which redirect T cell specificity against a tumor-specific antigen through the use of antibody fragments. They demonstrated remarkable efficacy in B cell hematologic malignancies, thus paving the way for their development in solid tumors. Nonetheless, the use of such new drugs to treat solid tumors is not straightforward. So far, the results from early phase clinical trials are not as impressive as expected but many improvements are under way. In this review we present an overview of the clinical development of CAR-T cells and BiTEs targeting the main antigens expressed by solid tumors. We emphasize the most frequent hurdles encountered by either CAR-T cells or BiTEs, or both, and summarize the strategies that have been proposed to overcome these obstacles.

IFNγ Is Critical for CAR T Cell-Mediated Myeloid Activation and Induction of Endogenous Immunity

Chimeric antigen receptor (CAR) T cells mediate potent antigen-specific antitumor activity; however, their indirect effects on the endogenous immune system are not well characterized. Remarkably, we demonstrate that CAR T-cell treatment of mouse syngeneic glioblastoma (GBM) activates intratumoral myeloid cells and induces endogenous T-cell memory responses coupled with feed-forward propagation of CAR T-cell responses. IFNγ production by CAR T cells and IFNγ responsiveness of host immune cells are critical for tumor immune landscape remodeling to promote a more activated and less suppressive tumor microenvironment. The clinical relevance of these observations is supported by studies showing that human IL13Rα2-CAR T cells activate patient-derived endogenous T cells and monocytes/macrophages through IFNγ signaling and induce the generation of tumor-specific T-cell responses in a responding patient with GBM. These studies establish that CAR T-cell therapy has the potential to shape the tumor microenvironment, creating a context permissible for eliciting endogenous antitumor immunity. SIGNIFICANCE: Our findings highlight the critical role of IFNγ signaling for a productive CAR T-cell therapy in GBM. We establish that CAR T cells can activate resident myeloid populations and promote endogenous T-cell immunity, emphasizing the importance of host innate and adaptive immunity for CAR T-cell therapy of solid tumors.This article is highlighted in the In This Issue feature, p. 2113.

Challenging Hurdles of Current Targeting in Glioblastoma: A Focus on Immunotherapeutic Strategies

Glioblastoma is the most frequent primary neoplasm of the central nervous system and still suffers from very poor therapeutic impact. No clear improvements over current standard of care have been made in the last decade. For other cancers, but also for brain metastasis, which harbors a very distinct biology from glioblastoma, immunotherapy has already proven its efficacy. Efforts have been pursued to allow glioblastoma patients to benefit from these new approaches, but the road is still long for broad application. Here, we aim to review key glioblastoma immune related characteristics, current immunotherapeutic strategies being explored, their potential caveats, and future directions.

CAR T cell therapy as a promising approach in cancer immunotherapy: challenges and opportunities

BACKGROUND

Chimeric antigen receptor (CAR)-modified T cell therapy has shown great potential in the immunotherapy of patients with hematologic malignancies. In spite of this striking achievement, there are still major challenges to overcome in CAR T cell therapy of solid tumors, including treatment-related toxicity and specificity. Also, other obstacles may be encountered in tackling solid tumors, such as their immunosuppressive microenvironment, the heterogeneous expression of cell surface markers, and the cumbersome arrival of T cells at the tumor site. Although several strategies have been developed to overcome these challenges, aditional research aimed at enhancing its efficacy with minimum side effects, the design of precise yet simplified work flows and the possibility to scale-up production with reduced costs and related risks is still warranted.

CONCLUSIONS

Here, we review main strategies to establish a balance between the toxicity and activity of CAR T cells in order to enhance their specificity and surpass immunosuppression. In recent years, many clinical studies have been conducted that eventually led to approved products. To date, the FDA has approved two anti-CD19 CAR T cell products for non-Hodgkin lymphoma therapy, i.e., axicbtagene ciloleucel and tisagenlecleucel. With all the advances that have been made in the field of CAR T cell therapy for hematologic malignancies therapy, ongoing studies are focused on optimizing its efficacy and specificity, as well as reducing the side effects. Also, the efforts are poised to broaden CAR T cell therapeutics for other cancers, especially solid tumors.

The Role of Cytokines and Chemokines in Shaping the Immune Microenvironment of Glioblastoma: Implications for Immunotherapy

Glioblastoma is the most common form of primary brain tumour in adults. For more than a decade, conventional treatment has produced a relatively modest improvement in the overall survival of glioblastoma patients. The immunosuppressive mechanisms employed by neoplastic and non-neoplastic cells within the tumour can limit treatment efficacy, and this can include the secretion of immunosuppressive cytokines and chemokines. These factors can play a significant role in immune modulation, thus disabling anti-tumour responses and contributing to tumour progression. Here, we review the complex interplay between populations of immune and tumour cells together with defined contributions by key cytokines and chemokines to these intercellular interactions. Understanding how these tumour-derived factors facilitate the crosstalk between cells may identify molecular candidates for potential immunotherapeutic targeting, which may enable better tumour control and improved patient survival.

In vivo CART cell imaging: Paving the way for success in CART cell therapy

Chimeric antigen receptor T (CART) cells are a promising immunotherapy that has induced dramatic anti-tumor responses in certain B cell malignancies. However, CART cell expansion and trafficking are often insufficient to yield long-term remissions, and serious toxicities can arise after CART cell administration. Visualizing CART cell expansion and trafficking in patients can detect an inadequate CART cell response or serve as an early warning for toxicity development, allowing CART cell treatment to be tailored accordingly to maximize therapeutic benefits. To this end, various imaging platforms are being developed to track CART cells in vivo, including nonspecific strategies to image activated T cells and reporter systems to specifically detect engineered T cells. Many of these platforms are clinically applicable and hold promise to provide valuable information and guide improved CART cell treatment.

Cellular Immunotherapy Targeting Cancer Stem Cells: Preclinical Evidence and Clinical Perspective

The term “cancer stem cells” (CSCs) commonly refers to a subset of tumor cells endowed with stemness features, potentially involved in chemo-resistance and disease relapses. CSCs may present peculiar immunogenic features influencing their homeostasis within the tumor microenvironment. The susceptibility of CSCs to recognition and targeting by the immune system is a relevant issue and matter of investigation, especially considering the multiple emerging immunotherapy strategies. Adoptive cellular immunotherapies, especially those strategies encompassing the genetic redirection with chimeric antigen receptors (CAR), hold relevant promise in several tumor settings and might in theory provide opportunities for selective elimination of CSC subsets. Initial dedicated preclinical studies are supporting the potential targeting of CSCs by cellular immunotherapies, indirect evidence from clinical studies may be derived and new studies are ongoing. Here we review the main issues related to the putative immunogenicity of CSCs, focusing on and highlighting the existing evidence and opportunities for cellular immunotherapy approaches with T and non-T antitumor lymphocytes.

New Era of Immunotherapy in Pediatric Brain Tumors: Chimeric Antigen Receptor T-Cell Therapy

Immunotherapy, including chimeric antigen receptor (CAR) T-cell therapy, immune checkpoint inhibitors, cancer vaccines, and dendritic cell therapy, has been incorporated as a fifth modality of modern cancer care, along with surgery, radiation, chemotherapy, and target therapy. Among them, CAR T-cell therapy emerges as one of the most promising treatments. In 2017, the first two CAR T-cell drugs, tisagenlecleucel and axicabtagene ciloleucel for B-cell acute lymphoblastic leukemia (ALL) and diffuse large B-cell lymphoma (DLBCL), respectively, were approved by the Food and Drug Administration (FDA). In addition to the successful applications to hematological malignancies, CAR T-cell therapy has been investigated to potentially treat solid tumors, including pediatric brain tumor, which serves as the leading cause of cancer-associated death for children and adolescents. However, the employment of CAR T-cell therapy in pediatric brain tumors still faces multiple challenges, such as CAR T-cell transportation and expansion through the blood–brain barrier, and identification of the specific target antigen on the tumor surface and immunosuppressive tumor microenvironment. Nevertheless, encouraging outcomes in both clinical and preclinical trials are coming to light. In this article, we outline the current propitious progress and discuss the obstacles needed to be overcome in order to unveil a new era of treatment in pediatric brain tumors.

Glioma Stem Cells as Immunotherapeutic Targets: Advancements and Challenges

Glioblastoma is the most common and lethal primary brain malignancy. Despite major investments in research into glioblastoma biology and drug development, treatment remains limited and survival has not substantially improved beyond 1-2 years. Cancer stem cells (CSC) or glioma stem cells (GSC) refer to a population of tumor originating cells capable of self-renewal and differentiation. While controversial and challenging to study, evidence suggests that GCSs may result in glioblastoma tumor recurrence and resistance to treatment. Multiple treatment strategies have been suggested at targeting GCSs, including immunotherapy, posttranscriptional regulation, modulation of the tumor microenvironment, and epigenetic modulation. In this review, we discuss recent advances in glioblastoma treatment specifically focused on targeting of GCSs as well as their potential integration into current clinical pathways and trials.

Immunotherapy: A Potential Approach for High-Grade Spinal Cord Astrocytomas

Spinal cord astrocytomas (SCAs) account for 6–8% of all primary spinal cord tumors. For high-grade SCAs, the prognosis is often poor with conventional therapy, thus the urgent need for novel treatments to improve patient survival. Immunotherapy is a promising therapeutic strategy and has been used to treat cancer in recent years. Several clinical trials have evaluated immunotherapy for intracranial gliomas, providing evidence for immunotherapy-mediated ability to inhibit tumor growth. Given the unique microenvironment and molecular biology of the spinal cord, this review will offer new perspectives on moving toward the application of successful immunotherapy for SCAs based on the latest studies and literature. Furthermore, we will discuss the challenges associated with immunotherapy in SCAs, propose prospects for future research, and provide a periodic summary of the current state of immunotherapy for SCAs immunotherapy.

Organoid Models of Glioblastoma and Their Role in Drug Discovery

Glioblastoma (GBM) is a devastating adult brain cancer with high rates of recurrence and treatment resistance. Cellular heterogeneity and extensive invasion of surrounding brain tissues are characteristic features of GBM that contribute to its intractability. Current GBM model systems do not recapitulate some of the complex features of GBM and have not produced sufficiently-effective treatments. This has cast doubt on the effectiveness of current GBM models and drug discovery paradigms. In search of alternative pre-clinical GBM models, various 3D organoid-based GBM model systems have been developed using human cells. The scalability of these systems and potential to more accurately model characteristic features of GBM, provide promising new avenues for pre-clinical GBM research and drug discovery efforts. Here, we review the current suite of organoid-GBM models, their individual strengths and weaknesses, and discuss their future applications with an emphasis on compound screening.