Prognostic relevance of tumor-infiltrating lymphocytes and immune checkpoints in pediatric medulloblastoma

EphA2 and phosphoantigen-mediated selective killing of medulloblastoma by γδT cells preserves neuronal and stem cell integrity

Medulloblastoma (MB) is a pediatric brain tumor that develops in the cerebellum, representing one of the most common malignant brain cancers in children. Standard treatments include surgery, chemotherapy, and radiation, but despite a 5-y survival rate of approximately 70%, these therapies often lead to significant neurological damage in the developing brain. This underscores the urgent need for less toxic, more effective therapeutic alternatives. Recent advancements in cancer immunotherapy, including immune checkpoint inhibitors and CAR-T cell therapy, have revolutionized cancer treatment. One promising avenue is the use of Gamma Delta (γδ)T cells, a unique T cell population with potential advantages, such as non-alloreactivity, potent tumor cell lysis, and broad antigen recognition. However, their capacity to recognize and target MB cells remains underexplored. To investigate the therapeutic potential of γδT cells against MB, we analyzed the proportion and status of MB-infiltrated γδT cells within patient datasets. We next investigated the expression of γδT cell ligands on MB cells and identified the EphA2 receptor and the phosphoantigen/Butyrophilin complex as key ligands, activating Vγ9 Vδ1 and Vγ9 Vδ2 T cells, respectively, leading to significant MB cell lysis in both monolayer and spheroid models. Importantly, preliminary safety data showed that γδT cells did not target differentiated neurons or neuroepithelial stem cells derived from induced pluripotent stem cells, underscoring the selectivity and safety of this approach. In conclusion, γδT cells trigger an efficient and specific killing of MB and would offer a promising novel therapeutic strategy.

The evolution of immune profiling: will there be a role for nanoparticles?

Immune profiling provides insights into the functioning of the immune system, including the distribution, abundance, and activity of immune cells. This understanding is essential for deciphering how the immune system responds to pathogens, vaccines, tumors, and other stimuli. Analyzing diverse immune cell types facilitates the development of personalized medicine approaches by characterizing individual variations in immune responses. With detailed immune profiles, clinicians can tailor treatment strategies to the specific immune status and needs of each patient, maximizing therapeutic efficacy while minimizing adverse effects. In this review, we discuss the evolution of immune profiling, from interrogating bulk cell samples in solution to evaluating the spatially-rich molecular profiles across intact preserved tissue sections. We also review various multiplexed imaging platforms recently developed, based on immunofluorescence and imaging mass spectrometry, and their impact on the field of immune profiling. Identifying and localizing various immune cell types across a patient's sample has already provided important insights into understanding disease progression, the development of novel targeted therapies, and predicting treatment response. We also offer a new perspective by highlighting the unprecedented potential of nanoparticles (NPs) that can open new horizons in immune profiling. NPs are known to provide enhanced detection sensitivity, targeting specificity, biocompatibility, stability, multimodal imaging features, and multiplexing capabilities. Therefore, we summarize the recent developments and advantages of NPs, which can contribute to advancing our understanding of immune function to facilitate precision medicine. Overall, NPs have the potential to offer a versatile and robust approach to profile the immune system with improved efficiency and multiplexed imaging power.

Identification of tumor rejection antigens and the immunologic landscape of medulloblastoma

BACKGROUND

The current standard of care treatments for medulloblastoma are insufficient as these do not take tumor heterogeneity into account. Newer, safer, patient-specific treatment approaches are required to treat high-risk medulloblastoma patients who are not cured by the standard therapies. Immunotherapy is a promising treatment modality that could be key to improving survival and avoiding morbidity. For an effective immune response, appropriate tumor antigens must be targeted. While medulloblastoma patients with subgroup-specific genetic substitutions have been previously reported, the immunogenicity of these genetic alterations remains unknown. The aim of this study is to identify potential tumor rejection antigens for the development of antigen-directed cellular therapies for medulloblastoma.

METHODS

We developed a cancer immunogenomics pipeline and performed a comprehensive analysis of medulloblastoma subgroup-specific transcription profiles (n = 170, 18 WNT, 46 SHH, 41 Group 3, and 65 Group 4 patient tumors) available through International Cancer Genome Consortium (ICGC) and European Genome-Phenome Archive (EGA). We performed in silico antigen prediction across a broad array of antigen classes including neoantigens, tumor-associated antigens (TAAs), and fusion proteins. Furthermore, we evaluated the antigen processing and presentation pathway in tumor cells and the immune infiltrating cell landscape using the latest computational deconvolution methods.

RESULTS

Medulloblastoma patients were found to express multiple private and shared immunogenic antigens. The proportion of predicted TAAs was higher than neoantigens and gene fusions for all molecular subgroups, except for sonic hedgehog (SHH), which had a higher neoantigen burden. Importantly, cancer-testis antigens, as well as previously unappreciated neurodevelopmental antigens, were found to be expressed by most patients across all medulloblastoma subgroups. Despite being immunologically cold, medulloblastoma subgroups were found to have distinct immune cell gene signatures.

CONCLUSIONS

Using a custom antigen prediction pipeline, we identified potential tumor rejection antigens with important implications for the development of immunotherapy for medulloblastoma.

Late-onset lymphopenia during radiation is associated with an increased risk of tumor recurrence in newly diagnosed pediatric medulloblastoma

BACKGROUND

Recent data found a correlation between lymphopenia occurring early during craniospinal radiation therapy (RT) and risk of disease recurrence in newly diagnosed childhood medulloblastoma. However, the population included patients who received chemotherapy prior to or during RT. Here, we investigate the effect of lymphopenia during RT in patients with newly diagnosed pediatric medulloblastoma who were chemotherapy-naïve.

PROCEDURE

We analyzed 79 patients with newly diagnosed medulloblastoma (ages 2-21 years) treated between 1997 and 2013 with craniospinal RT. Log-rank tests were used to determine survival differences, and Cox proportional hazards regression was used to assess associations between patient characteristics and lymphopenia with disease recurrence risk.

RESULTS

Eighty-three percent of patients (62/75) had grade ≥3 lymphopenia by RT Week 3, with 95% developing grade ≥3 lymphopenia at some point during therapy. There was no difference in incidence of lymphopenia between those who received proton beam RT (93%) versus photon (97%). Twenty-four of 79 (30%) patients developed disease recurrence at an average 27.0 months after diagnosis. There was higher risk of disease recurrence in patients with grade ≥3 lymphopenia during RT Week 4 (log-rank p = .016; Cox p = .03) and Week 5 (log-rank p = .024; Cox p = .032); after adjusting for clinical risk group, only grade ≥3 lymphopenia at Week 4 remained prognostic (Cox p = .04). No correlation was found between risk of tumor recurrence and early lymphopenia (RT Weeks 0-3) or absolute lymphocyte count (ALC) below the median at any time during RT.

CONCLUSIONS

Lymphopenia during RT Weeks 4 and 5 correlates with increased risk of tumor recurrence in pediatric patients with newly diagnosed medulloblastoma.

Understanding Cancer's Defense against Topoisomerase-Active Drugs: A Comprehensive Review

In recent years, the emergence of cancer drug resistance has been one of the crucial tumor hallmarks that are supported by the level of genetic heterogeneity and complexities at cellular levels. Oxidative stress, immune evasion, metabolic reprogramming, overexpression of ABC transporters, and stemness are among the several key contributing molecular and cellular response mechanisms. Topo-active drugs, e.g., doxorubicin and topotecan, are clinically active and are utilized extensively against a wide variety of human tumors and often result in the development of resistance and failure to therapy. Thus, there is an urgent need for an incremental and comprehensive understanding of mechanisms of cancer drug resistance specifically in the context of topo-active drugs. This review delves into the intricate mechanistic aspects of these intracellular and extracellular topo-active drug resistance mechanisms and explores the use of potential combinatorial approaches by utilizing various topo-active drugs and inhibitors of pathways involved in drug resistance. We believe that this review will help guide basic scientists, pre-clinicians, clinicians, and policymakers toward holistic and interdisciplinary strategies that transcend resistance, renewing optimism in the ongoing battle against cancer.

Oncolytic virus-driven immune remodeling revealed in mouse medulloblastomas at single cell resolution

Oncolytic viruses, modified for tumor-restricted infection, are a promising cancer immunotherapeutic, yet much remains to be understood about factors driving their activity and outcome in the tumor microenvironment. Here, we report that oncolytic herpes simplex virus C134, previously found to exert T cell-dependent efficacy in mouse models of glioblastoma, exerts T cell-independent efficacy in mouse models of medulloblastoma, indicating this oncolytic virus uses different mechanisms in different tumors. We investigated C134's behavior in mouse medulloblastomas, using single cell RNA sequencing to map C134-induced gene expression changes across cell types, timepoints, and medulloblastoma subgroup models at whole-transcriptome resolution. Our work details substantial oncolytic virus-induced transcriptional remodeling of medulloblastoma-infiltrating immune cells, 10 subpopulations of monocytes and macrophages collectively demonstrating M1-like responses to C134, and suggests C134 be investigated as a potential new therapy for medulloblastoma.

Opportunities and Advances in Radiomics and Radiogenomics for Pediatric Medulloblastoma Tumors

Recent advances in artificial intelligence have greatly impacted the field of medical imaging and vastly improved the development of computational algorithms for data analysis. In the field of pediatric neuro-oncology, radiomics, the process of obtaining high-dimensional data from radiographic images, has been recently utilized in applications including survival prognostication, molecular classification, and tumor type classification. Similarly, radiogenomics, or the integration of radiomic and genomic data, has allowed for building comprehensive computational models to better understand disease etiology. While there exist excellent review articles on radiomics and radiogenomic pipelines and their applications in adult solid tumors, in this review article, we specifically review these computational approaches in the context of pediatric medulloblastoma tumors. Based on our systematic literature research via PubMed and Google Scholar, we provide a detailed summary of a total of 15 articles that have utilized radiomic and radiogenomic analysis for survival prognostication, tumor segmentation, and molecular subgroup classification in the context of pediatric medulloblastoma. Lastly, we shed light on the current challenges with the existing approaches as well as future directions and opportunities with using these computational radiomic and radiogenomic approaches for pediatric medulloblastoma tumors.

Characterizing the tumor immune microenvironment of ependymomas using targeted gene expression profiles and RNA sequencing

BACKGROUND

Defining the tumor immune microenvironment (TIME) of patients using transcriptome analysis is gaining more popularity. Here, we examined and discussed the pros and cons of using RNA sequencing for fresh frozen samples and targeted gene expression immune profiles (NanoString) for formalin-fixed, paraffin-embedded (FFPE) samples to characterize the TIME of ependymoma samples.

RESULTS

Our results showed a stable expression of the 40 housekeeping genes throughout all samples. The Pearson correlation of the endogenous genes was high. To define the TIME, we first checked the expression of the PTPRC gene, known as CD45, and found it was above the detection limit in all samples by both techniques. T cells were identified consistently using the two types of data. In addition, both techniques showed that the immune landscape was heterogeneous in the 6 ependymoma samples used for this study.

CONCLUSIONS

The low-abundant genes were detected in higher quantities using the NanoString technique, even when FFPE samples were used. RNA sequencing is better suited for biomarker discovery, fusion gene detection, and getting a broader overview of the TIME. The technique that was used to measure the samples had a considerable effect on the type of immune cells that were identified. The limited number of tumor-infiltrating immune cells compared to the high density of tumor cells in ependymoma can limit the sensitivity of RNA expression techniques regarding the identification of the infiltrating immune cells.

Exploring the Molecular Complexity of Medulloblastoma: Implications for Diagnosis and Treatment

Medulloblastoma is the most common malignant brain tumor in children. Over the last few decades, significant progress has been made in revealing the key molecular underpinnings of this disease, leading to the identification of distinct molecular subgroups with different clinical outcomes. In this review, we provide an update on the molecular landscape of medulloblastoma and treatment strategies. We discuss the four main molecular subgroups (WNT-activated, SHH-activated, and non-WNT/non-SHH groups 3 and 4), highlighting the key genetic alterations and signaling pathways associated with each entity. Furthermore, we explore the emerging role of epigenetic regulation in medulloblastoma and the mechanism of resistance to therapy. We also delve into the latest developments in targeted therapies and immunotherapies. Continuing collaborative efforts are needed to further unravel the complex molecular mechanisms and profile optimal treatment for this devastating disease.

Immunobiology and Cytokine Modulation of the Pediatric Brain Tumor Microenvironment: A Scoping Review

Utilizing a Scoping Review strategy in the domain of immune biology to identify immune therapeutic targets, knowledge gaps for implementing immune therapeutic strategies for pediatric brain tumors was assessed. The analysis demonstrated limited efforts to date to characterize and understand the immunological aspects of tumor biology with an over-reliance on observations from the adult glioma population. Foundational knowledge regarding the frequency and ubiquity of immune therapeutic targets is an area of unmet need along with the development of immune-competent pediatric tumor models to test therapeutics and especially combinatorial treatment. Opportunities arise in the evolution of pediatric tumor classification from histological to molecular with targeted immune therapeutics.

The Role of Immunotherapy in the Treatment of Rare Central Nervous System Tumors

Establishing novel therapies for rare central nervous system (CNS) tumors is arduous due to challenges in conducting clinical trials in rare tumors. Immunotherapy treatment has been a rapidly developing field and has demonstrated improvements in outcomes for multiple types of solid malignancies. In rare CNS tumors, the role of immunotherapy is being explored. In this article, we review the preclinical and clinical data of various immunotherapy modalities in select rare CNS tumors, including atypical meningioma, aggressive pituitary adenoma, pituitary carcinoma, ependymoma, embryonal tumor, atypical teratoid/rhabdoid tumor, and meningeal solitary fibrous tumor. Among these tumor types, some studies have shown promise; however, ongoing clinical trials will be critical for defining and optimizing the role of immunotherapy for these patients.

Pediatric Brain Tumours: Lessons from the Immune Microenvironment

In spite of recent advances in tumour molecular subtyping, pediatric brain tumours (PBTs) remain the leading cause of cancer-related deaths in children. While some PBTs are treatable with favourable outcomes, recurrent and metastatic disease for certain types of PBTs remains challenging and is often fatal. Tumour immunotherapy has emerged as a hopeful avenue for the treatment of childhood tumours, and recent immunotherapy efforts have been directed towards PBTs. This strategy has the potential to combat otherwise incurable PBTs, while minimizing off-target effects and long-term sequelae. As the infiltration and activation states of immune cells, including tumour-infiltrating lymphocytes and tumour-associated macrophages, are key to shaping responses towards immunotherapy, this review explores the immune landscape of the developing brain and discusses the tumour immune microenvironments of common PBTs, with hopes of conferring insights that may inform future treatment design.

Advances in the application of immune checkpoint inhibitors in gynecological tumors

BACKGROUND

Immune checkpoints are regulatory molecules that suppress immune effector cells, and are essential for maintaining tolerance, preventing autoimmune reactions, and minimizing tissue damage by controlling the duration and intensity of the immune responses. However, immune checkpoints are frequently upregulated during cancer and dampen the anti-tumor immune responses. Immune checkpoint inhibitors (ICIs) have been effective against multiple tumors, and have improved patients' survival outcomes. Recent clinical trials have also reported promising therapeutic effects of ICIs in some gynecological cancers.

AIM

To review the current research and future directions in the treatment of gynecological malignancies, including ovarian, cervical and endometrial cancers, using ICIs.

CONCLUSION

Currently, cervical and ovarian cancers are the only gynecological tumors that are treated by immunotherapeutic approaches. In addition, ICIs, chimeric antigen receptor (CAR)- and T cell receptor (TCR)-engineered T cells targeting endometrial tumors, especially those originating in the vulva and fallopian tubes, are under development. Nevertheless, the molecular mechanism underlying the effects of ICIs, especially in combination with chemotherapy, radiation therapy, anti-angiogenesis drugs and poly ADP ribose polymerase inhibitors (PARPi), needs to be elucidated. Furthermore, novel predictive biomarkers have to be identified in order to increase the therapeutic efficacy of ICIs while reducing adverse reactions.

Epigenetics and immune cells in medulloblastoma

Medulloblastoma (MB) is a highly malignant childhood tumor of the cerebellum. Transcriptional and epigenetic signatures have classified MB into four molecular subgroups, further stratified into biologically different subtypes with distinct somatic copy-number aberrations, driver genes, epigenetic alterations, activated pathways, and clinical outcomes. The brain tumor microenvironment (BTME) is of importance to regulate a complex network of cells, including immune cells, involved in cancer progression in brain malignancies. MB was considered with a “cold” immunophenotype due to the low influx of immune cells across the blood brain barrier (BBB). Recently, this assumption has been reconsidered because of the identification of infiltrating immune cells showing immunosuppressive phenotypes in the BTME of MB tumors. Here, we are providing a comprehensive overview of the current status of epigenetics alterations occurring during cancer progression with a description of the genomic landscape of MB by focusing on immune cells within the BTME. We further describe how new immunotherapeutic approaches could influence concurring epigenetic mechanisms of the immunosuppressive cells in BTME. In conclusion, the modulation of these molecular genetic complexes in BTME during cancer progression might enhance the therapeutic benefit, thus firing new weapons to fight MB.

Behavioral Improvements following Lesion Resection for Pediatric Epilepsy: Pediatric Psychosurgery?

INTRODUCTION

Resection of brain lesions associated with refractory epilepsy to achieve seizure control is well accepted. However, concurrent behavioral effects of these lesions such as changes in mood, personality, and cognition and the effects of surgery on behavior have not been well characterized. We describe 5 such children with epileptogenic lesions and significant behavioral abnormalities which improved after surgery.

CASE DESCRIPTIONS

Five children (ages 3-14 years) with major behavioral abnormalities and lesional epilepsy were identified and treated at our center. Behavioral problems included academic impairment, impulsivity, self-injurious behavior, and decreased social interaction with diagnoses of ADHD, oppositional defiant disorder, and autism. Pre-operative neuropsychiatric testing was performed in 4/5 patients and revealed low-average cognitive and intellectual abilities for their age, attentional difficulties, and poor memory. Lesions were located in the temporal (2 gangliogliomas, 1 JPA, 1 cavernoma) and parietal (1 DNET) lobes. Gross total resection was achieved in all cases. At mean 1-year follow-up, seizure freedom (Engel 1a in 3 patients, Engel 1c in 2 patients) and significant behavioral improvements (academic performance, attention, socialization, and aggression) were achieved in all. Two patients manifested violence pre-operatively; one had extreme behavior with violence toward teachers and peers despite low seizure burden. Since surgery, his behavior has normalized.

CONCLUSION

We identified 5 patients with severe behavioral disorders in the setting of lesional epilepsy, all of whom demonstrated improvement after surgery. The degree of behavioral abnormality was disproportionate to epilepsy severity, suggesting a more complicated mechanism by which lesional epilepsy impacts behavior. We propose a novel paradigm in which lesionectomy may offer behavioral benefit even when seizures are not refractory. Thus, behavioral improvement may be an important novel goal for neurosurgical resection in children with epileptic brain lesions.

Digital expression profile of immune checkpoint genes in medulloblastomas identifies CD24 and CD276 as putative immunotherapy targets

Introduction

Medulloblastoma is the most common and lethal pediatric malignant brain tumor. It comprises four main molecular subgroups: WNT-activated, SHH-activated, Group 3, and Group 4. Medulloblastoma treatment is surgical resection, craniospinal radiation, and chemotherapy. However, many patients do not respond to therapy, and most suffer severe side effects. Cancer immunotherapy targeting immune checkpoints (IC) (PD-1, PD-L1, and CTLA4) has been getting disappointing outcomes in brain tumors. Nevertheless, other less explored immune checkpoints may be promising candidates for medulloblastoma therapy.

Objectives

In the present study, we aimed to characterize the expression profile of 19 immune checkpoints in medulloblastoma.

Methods

We analyzed 88 formalin-fixed paraffin-embedded medulloblastomas previously classified for each molecular subgroup and three non-tumoral brain tissue. mRNA levels of 19 immune checkpoint-related genes were quantified using the nCounter (PanCancer Immune Profiling Panel) assay. Further in silico analysis was performed in two larger public microarray datasets, one of which enabled comparisons between tumoral and non-tumoral tissues. Immunohistochemistry of PD-L1 was performed in a subset of cases. Microsatellite instability was also molecularly analyzed.

Results

We observed an absence of expression of the canonic ICs, namely PDCD1 (PD-1), CD274 (PD-L1), and CTLA4, as well as CD80, CD86, BTLA, IDO1, CD48, TNFSF14, CD160, CEACAM1, and CD244. PD-L1 protein expression was also practically absent. We found higher mRNA levels of CD24, CD47, CD276 (B7-H3), and PVR, and lower mRNA levels of HAVCR2, LAG3, and TIGIT genes, with significant differences across the four molecular subgroups. Compared to the non-tumor tissues, the expression levels of CD276 in all subgroups and CD24 in SHH, Group 3, and Group 4 subgroups are significantly higher. The in silico analysis confirmed the expression profile found in the Brazilian cohort, including the lower/absent expression of the canonic ICs. Moreover, it confirmed the overexpression of CD24 and CD276 in medulloblastomas compared with the non-tumor tissue. Additionally, CD276 and CD24 high levels were associated with worse survival.

Conclusion

These results highlight the low or absence of mRNA levels of the canonic targetable ICs in medulloblastomas. Importantly, the analysis revealed overexpression of CD24 and CD276, which can constitute prognostic biomarkers and attractive immunotherapy targets for medulloblastomas.

Immunotherapy for Pediatric Brain and Spine Tumors: Current State and Future Directions

BACKGROUND

Brain tumors are the most common solid tumors and the leading cause of cancer-related deaths in children. Incidence in the USA has been on the rise for the last 2 decades. While therapeutic advances in diagnosis and treatment have improved survival and quality of life in many children, prognosis remains poor and current treatments have significant long-term sequelae.

SUMMARY

There is a substantial need for the development of new therapeutic approaches, and since the introduction of immunotherapy by immune checkpoint inhibitors, there has been an exponential increase in clinical trials to adopt these and other immunotherapy approaches in children with brain tumors. In this review, we summarize the current immunotherapy landscape for various pediatric brain tumor types including choroid plexus tumors, embryonal tumors (medulloblastoma, AT/RT, PNETs), ependymoma, germ cell tumors, gliomas, glioneuronal and neuronal tumors, and mesenchymal tumors. We discuss the latest clinical trials and noteworthy preclinical studies to treat these pediatric brain tumors using checkpoint inhibitors, cellular therapies (CAR-T, NK, T cell), oncolytic virotherapy, radioimmunotherapy, tumor vaccines, immunomodulators, and other targeted therapies.

KEY MESSAGES

The current landscape for immunotherapy in pediatric brain tumors is still emerging, but results in certain tumors have been promising. In the age of targeted therapy, genetic tumor profiling, and many ongoing clinical trials, immunotherapy will likely become an increasingly effective tool in the neuro-oncologist armamentarium.

Cellular Immunotherapy for Medulloblastoma

Medulloblastoma (MB) is the most common malignant brain tumor in children, making up ~20% of all primary pediatric brain tumors. Current therapies consist of maximal surgical resection and aggressive radio- and chemotherapy. A third of the treated patients cannot be cured and survivors are often left with devastating long-term side effects. Novel efficient and targeted treatment is desperately needed for this patient population. Cellular immunotherapy aims to enhance and utilize immune cells to target tumors, and has been proven successful in various cancers. However, for MB, the knowledge and possibilities of cellular immunotherapy are limited. In this review, we provide a comprehensive overview of the current status of cellular immunotherapy for MB, from fundamental in vitro research to in vivo models and (ongoing) clinical trials. In addition, we compare our findings to cellular immunotherapy in glioma, an MB-like intracranial tumor. Finally, future possibilities for MB are discussed to improve efficacy and safety.

Medulloblastoma in the Modern Era: Review of Contemporary Trials, Molecular Advances, and Updates in Management

Critical discoveries over the past two decades have transformed our understanding of medulloblastoma from a single entity into a clinically and biologically heterogeneous disease composed of at least four molecularly distinct subgroups with prognostically and therapeutically relevant genomic signatures. Contemporary clinical trials also have provided valuable insight guiding appropriate treatment strategies. Despite therapeutic and biological advances, medulloblastoma patients across the age spectrum experience tumor- and treatment-related morbidity and mortality. Using an updated risk stratification approach integrating both clinical and molecular features, ongoing research seeks to (1) cautiously reduce therapy and mitigate toxicity in low-average risk patients, and (2) thoughtfully intensify treatment with incorporation of novel, biologically guided agents for patients with high-risk disease. Herein, we review important historical and contemporary studies, discuss management updates, and summarize current knowledge of the biological landscape across unique pediatric, infant, young adult, and relapsed medulloblastoma populations.

Molecular profile reveals immune-associated markers of medulloblastoma for different subtypes

Medulloblastoma, a common pediatric malignant tumor, has been recognized to have four molecular subgroups [wingless (WNT), sonic hedgehog (SHH), group 3, group 4], which are defined by the characteristic gene transcriptomic and DNA methylomic profiles, and has distinct clinical features within each subgroup. The tumor immune microenvironment is integral in tumor initiation and progression and might be associated with therapeutic responses. However, to date, the immune infiltrative landscape of medulloblastoma has not yet been elucidated. Thus, we proposed MethylCIBERSORT to estimate the degree of immune cell infiltration and weighted correlation network analysis (WGCNA) to find modules of highly correlated genes. Synthesizing the hub genes in the protein–protein interaction (PPI) network and modules of the co-expression network, we identify three candidate biomarkers [GRB2-associated-binding protein 1 (GAB1), Abelson 1 (ABL1), and CXC motif chemokine receptor type 4 (CXCR4)] via the molecular profiles of medulloblastoma. Given this, we investigated the correlation between these three immune hub genes and immune checkpoint blockade response and the potential of drug prediction further. In addition, this study demonstrated a higher presence of endothelial cells and infiltrating immune cells in Group 3 tumor bulk. The above results will be conducive to better comprehending the immune-related pathogenesis and treatment of medulloblastoma.

Pediatric medulloblastoma express immune checkpoint B7-H3

PURPOSE

Medulloblastomas (MB) are highly malignant brain tumors that predominantly occur in young infants. Immunotherapy to boost the immune system is emerging as a novel promising approach, but is often hampered by inhibitory immune checkpoints. In the present study, we have studied immune checkpoint B7-H3 expression in a tissue cohort of human pediatric MB.

METHODS

Expression of B7-H3 was detected by immunohistochemistry and classified via B7-H3 staining intensity and percentage of B7-H3 positive tumor cells. Subsequently, B7-H3 protein expression was distinguished in MB molecular subtypes and correlated to immune cell infiltrates, patient characteristics, and survival.

RESULTS

B7-H3 protein expression was found in 23 out of 24 (96%) human pediatric MB cases and in 17 out of 24 (71%) MB cases > 25% of tumor cells had any level of B7-H3 expression. B7-H3 protein expression was more frequent on Group-4 MB as compared with other molecular subtypes (p = 0.02). Tumors with high B7-H3 expression showed less influx of γδT cells (p = 0.002) and CD3+ T cells (p = 0.041).

CONCLUSION

Immune checkpoint B7-H3 is differentially expressed by the large majority of pediatric MB. This further warrants the development of novel B7-H3-directed (immuno)therapeutic methods for children with incurable, metastatic, or chemo-resistant MB.

Pediatric Pan-Central Nervous System Tumor Methylome Analyses Reveal Immune-Related LncRNAs

Pediatric central nervous system (CNS) tumors are the second most common cancer diagnosis among children. Long noncoding RNAs (lncRNAs) emerge as critical regulators of gene expression, and they play fundamental roles in immune regulation. However, knowledge on epigenetic changes in lncRNAs in diverse types of pediatric CNS tumors is lacking. Here, we integrated the DNA methylation profiles of 2,257 pediatric CNS tumors across 61 subtypes with lncRNA annotations and presented the epigenetically regulated landscape of lncRNAs. We revealed the prevalent lncRNA methylation heterogeneity across pediatric pan-CNS tumors. Based on lncRNA methylation profiles, we refined 14 lncRNA methylation clusters with distinct immune microenvironment patterns. Moreover, we found that lncRNA methylations were significantly correlated with immune cell infiltrations in diverse tumor subtypes. Immune-related lncRNAs were further identified by investigating their correlation with immune cell infiltrations and potentially regulated target genes. LncRNA with methylation perturbations potentially regulate the genes in immune-related pathways. We finally identified several candidate immune-related lncRNA biomarkers (i.e., SSTR5-AS1, CNTN4-AS1, and OSTM1-AS1) in pediatric cancer for further functional validation. In summary, our study represents a comprehensive repertoire of epigenetically regulated immune-related lncRNAs in pediatric pan-CNS tumors, and will facilitate the development of immunotherapeutic targets.

Individualized discovery of rare cancer drivers in global network context

Late advances in genome sequencing expanded the space of known cancer driver genes several-fold. However, most of this surge was based on computational analysis of somatic mutation frequencies and/or their impact on the protein function. On the contrary, experimental research necessarily accounted for functional context of mutations interacting with other genes and conferring cancer phenotypes. Eventually, just such results become ‘hard currency’ of cancer biology. The new method, NEAdriver employs knowledge accumulated thus far in the form of global interaction network and functionally annotated pathways in order to recover known and predict novel driver genes. The driver discovery was individualized by accounting for mutations’ co-occurrence in each tumour genome – as an alternative to summarizing information over the whole cancer patient cohorts. For each somatic genome change, probabilistic estimates from two lanes of network analysis were combined into joint likelihoods of being a driver. Thus, ability to detect previously unnoticed candidate driver events emerged from combining individual genomic context with network perspective. The procedure was applied to 10 largest cancer cohorts followed by evaluating error rates against previous cancer gene sets. The discovered driver combinations were shown to be informative on cancer outcome. This revealed driver genes with individually sparse mutation patterns that would not be detectable by other computational methods and related to cancer biology domains poorly covered by previous analyses. In particular, recurrent mutations of collagen, laminin, and integrin genes were observed in the adenocarcinoma and glioblastoma cancers. Considering constellation patterns of candidate drivers in individual cancer genomes opens a novel avenue for personalized cancer medicine.

Coming in from the cold: overcoming the hostile immune microenvironment of medulloblastoma

Medulloblastoma is an aggressive brain tumor that occurs predominantly in children. Despite intensive therapy, many patients die of the disease, and novel therapies are desperately needed. Although immunotherapy has shown promise in many cancers, the low mutational burden, limited infiltration of immune effector cells, and immune-suppressive microenvironment of medulloblastoma have led to the assumption that it is unlikely to respond to immunotherapy. However, emerging evidence is challenging this view. Here we review recent preclinical and clinical studies that have identified mechanisms of immune evasion in medulloblastoma, and highlight possible therapeutic interventions that may give new hope to medulloblastoma patients and their families.

A Toolkit for Profiling the Immune Landscape of Pediatric Central Nervous System Malignancies

The prognosis of pediatric central nervous system (CNS) malignancies remains dismal due to limited treatment options, resulting in high mortality rates and long-term morbidities. Immunotherapies, including checkpoint inhibition, cancer vaccines, engineered T cell therapies, and oncolytic viruses, have promising results in some hematological and solid malignancies, and are being investigated in clinical trials for various high-grade CNS malignancies. However, the role of the tumor immune microenvironment (TIME) in CNS malignancies is mostly unknown for pediatric cases. In order to successfully implement immunotherapies and to eventually predict which patients would benefit from such treatments, in-depth characterization of the TIME at diagnosis and throughout treatment is essential. In this review, we provide an overview of techniques for immune profiling of CNS malignancies, and detail how they can be utilized for different tissue types and studies. These techniques include immunohistochemistry and flow cytometry for quantifying and phenotyping the infiltrating immune cells, bulk and single-cell transcriptomics for describing the implicated immunological pathways, as well as functional assays. Finally, we aim to describe the potential benefits of evaluating other compartments of the immune system implicated by cancer therapies, such as cerebrospinal fluid and blood, and how such liquid biopsies are informative when designing immune monitoring studies. Understanding and uniformly evaluating the TIME and immune landscape of pediatric CNS malignancies will be essential to eventually integrate immunotherapy into clinical practice.

Tumor immunotherapies by immune checkpoint inhibitors (ICIs); the pros and cons

The main breakthrough in tumor immunotherapy was the discovery of immune checkpoint (IC) proteins, which act as a potent suppressor of the immune system by a myriad of mechanisms. After that, scientists focused on the immune checkpoint molecules mainly. Thereby, much effort was spent to progress novel strategies for suppressing these inhibitory axes, resulting in the evolution of immune checkpoint inhibitors (ICIs). Then, ICIs have become a promising approach and shaped a paradigm shift in tumor immunotherapies. CTLA-4 plays an influential role in attenuation of the induction of naïve and memory T cells by engagement with its responding ligands like B7-1 (CD80) and B7-2 (CD86). Besides, PD-1 is predominantly implicated in adjusting T cell function in peripheral tissues through its interaction with programmed death-ligand 1 (PD-L1) and PD-L2. Given their suppressive effects on anti-tumor immunity, it has firmly been documented that ICIs based therapies can be practical and rational therapeutic approaches to treat cancer patients. Nonetheless, tumor inherent or acquired resistance to ICI and some treatment-related toxicities restrict their application in the clinic. The current review will deliver a comprehensive overview of the ICI application to treat human tumors alone or in combination with other modalities to support more desired outcomes and lower toxicities in cancer patients. Video Abstract.

Enhanced Survival of High-Risk Medulloblastoma-Bearing Mice after Multimodal Treatment with Radiotherapy, Decitabine, and Abacavir

Children with high-risk SHH/TP53-mut and Group 3 medulloblastoma (MB) have a 5-year overall survival of only 40%. Innovative approaches to enhance survival while preventing adverse effects are urgently needed. We investigated an innovative therapy approach combining irradiation (RT), decitabine (DEC), and abacavir (ABC) in a patient-derived orthotopic SHH/TP53-mut and Group 3 MB mouse model. MB-bearing mice were treated with DEC, ABC and RT. Mouse survival, tumor growth (BLI, MRT) tumor histology (H/E), proliferation (Ki-67), and endothelial (CD31) staining were analyzed. Gene expression was examined by microarray and RT-PCR (Ki-67, VEGF, CD31, CD15, CD133, nestin, CD68, IBA). The RT/DEC/ABC therapy inhibited tumor growth and enhanced mouse survival. Ki-67 decreased in SHH/TP53-mut MBs after RT, DEC, RT/ABC, and RT/DEC/ABC therapy. CD31 was higher in SHH/TP53-mut compared to Group 3 MBs and decreased after RT/DEC/ABC. Microarray analyses showed a therapy-induced downregulation of cell cycle genes. By RT-PCR, no therapy-induced effect on stem cell fraction or immune cell invasion/activation could be shown. We showed for the first time that RT/DEC/ABC therapy improves survival of orthotopic SHH/TP53-mut and Group 3 MB-bearing mice without inducing adverse effects suggesting the potential for an adjuvant application of this multimodal therapy approach in the human clinic.

The Current Landscape of Targeted Clinical Trials in Non-WNT/Non-SHH Medulloblastoma

Simple Summary

Medulloblastoma is a form of malignant brain tumor that arises predominantly in infants and young children and can be divided into different groups based on molecular markers. The group of non-WNT/non-SHH medulloblastoma includes a spectrum of heterogeneous subgroups that differ in their biological characteristics, genetic underpinnings, and clinical course of disease. Non-WNT/non-SHH medulloblastoma is currently treated with surgery, chemotherapy, and radiotherapy; however, new drugs are needed to treat patients who are not yet curable and to reduce treatment-related toxicity and side effects. We here review which new treatment options for non-WNT/non-SHH medulloblastoma are currently clinically tested. Furthermore, we illustrate the challenges that have to be overcome to reach a new therapeutic standard for non-WNT/non-SHH medulloblastoma, for instance the current lack of good preclinical models, and the necessity to conduct trials in a comparably small patient collective.

Abstract

Medulloblastoma is an embryonal pediatric brain tumor and can be divided into at least four molecularly defined groups. The category non-WNT/non-SHH medulloblastoma summarizes medulloblastoma groups 3 and 4 and is characterized by considerable genetic and clinical heterogeneity. New therapeutic strategies are needed to increase survival rates and to reduce treatment-related toxicity. We performed a noncomprehensive targeted review of the current clinical trial landscape and literature to summarize innovative treatment options for non-WNT/non-SHH medulloblastoma. A multitude of new drugs is currently evaluated in trials for which non-WNT/non-SHH patients are eligible, for instance immunotherapy, kinase inhibitors, and drugs targeting the epigenome. However, the majority of these trials is not restricted to medulloblastoma and lacks molecular classification. Whereas many new molecular targets have been identified in the last decade, which are currently tested in clinical trials, several challenges remain on the way to reach a new therapeutic strategy for non-WNT/non-SHH medulloblastoma. These include the severe lack of faithful preclinical models and predictive biomarkers, the question on how to stratify patients for clinical trials, and the relative lack of studies that recruit large, homogeneous patient collectives. Innovative trial designs and international collaboration will be a key to eventually overcome these obstacles.

Combination therapy with immune checkpoint inhibitors (ICIs); a new frontier

Recently, immune checkpoint inhibitors (ICIs) therapy has become a promising therapeutic strategy with encouraging therapeutic outcomes due to their durable anti-tumor effects. Though, tumor inherent or acquired resistance to ICIs accompanied with treatment-related toxicities hamper their clinical utility. Overall, about 60-70% of patients (e.g., melanoma and lung cancer) who received ICIs show no objective response to intervention. The resistance to ICIs mainly caused by alterations in the tumor microenvironment (TME), which in turn, supports angiogenesis and also blocks immune cell antitumor activities, facilitating tumor cells' evasion from host immunosurveillance. Thereby, it has been supposed and also validated that combination therapy with ICIs and other therapeutic means, ranging from chemoradiotherapy to targeted therapies as well as cancer vaccines, can capably compromise tumor resistance to immune checkpoint blocked therapy. Herein, we have focused on the therapeutic benefits of ICIs as a groundbreaking approach in the context of tumor immunotherapy and also deliver an overview concerning the therapeutic influences of the addition of ICIs to other modalities to circumvent tumor resistance to ICIs.

Conventional Therapies Deplete Brain-Infiltrating Adaptive Immune Cells in a Mouse Model of Group 3 Medulloblastoma Implicating Myeloid Cells as Favorable Immunotherapy Targets

Medulloblastoma is the most common childhood brain cancer. Mainstay treatments of radiation and chemotherapy have not changed in decades and new treatment approaches are crucial for the improvement of clinical outcomes. To date, immunotherapies for medulloblastoma have been unsuccessful, and studies investigating the immune microenvironment of the disease and the impact of current therapies are limited. Preclinical models that recapitulate both the disease and immune environment are essential for understanding immune-tumor interactions and to aid the identification of new and effective immunotherapies. Using an immune-competent mouse model of aggressive Myc-driven medulloblastoma, we characterized the brain immune microenvironment and changes induced in response to craniospinal irradiation, or the medulloblastoma chemotherapies cyclophosphamide or gemcitabine. The role of adaptive immunity in disease progression and treatment response was delineated by comparing survival outcomes in wildtype C57Bl/6J and in mice deficient in Rag1 that lack mature T and B cells. We found medulloblastomas in wildtype and Rag1-deficient mice grew equally fast, and that craniospinal irradiation and chemotherapies extended survival equally in wildtype and Rag1-deficient mice, suggesting that tumor growth and treatment response is independent of T and B cells. Medulloblastomas were myeloid dominant, and in wildtype mice, craniospinal irradiation and cyclophosphamide depleted T and B cells in the brain. Gemcitabine treatment was found to minimally alter the immune populations in the brain, resulting only in a depletion of neutrophils. Intratumorally, we observed an abundance of Iba1⁺ macrophages, and we show that CD45^high cells comprise the majority of immune cells within these medulloblastomas but found that existing markers are insufficient to clearly delineate resident microglia from infiltrating macrophages. Ultimately, brain resident and peripheral macrophages dominate the brain and tumor microenvironment and are not depleted by standard-of-care medulloblastoma therapies. These populations therefore present a favorable target for immunotherapy in combination with front-line treatments.

Relapsed Medulloblastoma in Pre-Irradiated Patients: Current Practice for Diagnostics and Treatment

Relapsed medulloblastoma (rMB) accounts for a considerable, and disproportionate amount of childhood cancer deaths. Recent advances have gone someway to characterising disease biology at relapse including second malignancies that often cannot be distinguished from relapse on imaging alone. Furthermore, there are now multiple international early-phase trials exploring drug-target matches across a range of high-risk/relapsed paediatric tumours. Despite these advances, treatment at relapse in pre-irradiated patients is typically non-curative and focuses on providing life-prolonging and symptom-modifying care that is tailored to the needs and wishes of the individual and their family. Here, we describe the current understanding of prognostic factors at disease relapse such as principal molecular group, adverse molecular biology, and timing of relapse. We provide an overview of the clinical diagnostic process including signs and symptoms, staging investigations, and molecular pathology, followed by a summary of treatment modalities and considerations. Finally, we summarise future directions to progress understanding of treatment resistance and the biological mechanisms underpinning early therapy-refractory and relapsed disease. These initiatives include development of comprehensive and collaborative molecular profiling approaches at relapse, liquid biopsies such as cerebrospinal fluid (CSF) as a biomarker of minimal residual disease (MRD), modelling strategies, and the use of primary tumour material for real-time drug screening approaches.

Immune cell landscape and immunotherapy of medulloblastoma

Medulloblastoma is the most common primary pediatric malignancy of the central nervous system. Recurrent and refractory patients account for approximately 30% of them. Immune cells are an important component of the brain tumor microenvironment, including tumor-associated macrophages, T lymphocytes, natural killer cells, dendritic cells, neutrophils and B lymphocytes. Understanding how they behave and interact is important in the investigation of the onset and progression of medulloblastoma. Here, we overview the features and recent advances of each component of immune cells in medulloblastoma. Meanwhile, immunotherapy is a promising but also challenging treatment strategy for medulloblastoma. At present, there are a growing number of immunotherapeutic approaches under investigation including immune checkpoint inhibitors, oncolytic viruses, cancer vaccines, chimeric antigen receptor T cell therapies, and natural killer cells in recurrent and refractory medulloblastoma patients.

High expression of Toll-like receptor 7 is a survival factor in pediatric medulloblastoma

PURPOSE

Medulloblastoma is an embryonal brain tumor that predominantly occurs in childhood with a wide histological and molecular variability. Our aim was to investigate the expression of Toll-like receptors (TLRs), their association with the infiltration of immune cells and with the histological subgroups, and, also, with the overall survival of patients.

METHODS

Fifty-six paraffin-preserved biopsies from children with medulloblastoma of the classic, desmoplastic, and anaplastic subtypes were included. Microarrays of tissues were performed, and the infiltration of T and NK cells was quantified, as well as the expression of TLR7, TLR8, and TLR9. For all statistical analyses, significance was p < 0.05.

RESULTS

CD4 + and CD8 + T lymphocytes and NK cells were found infiltrating the tumor. The infiltration of NK and CD4 + cells was greater in the classic and desmoplastic subtypes than in anaplastic. We found an important expression of TLRs in all medulloblastomas, but TLR7 and TLR8 were considerably higher in classic and desmoplastic subtypes than in anaplastic. Importantly, we observed that TLR7 was a prognostic factor for survival.

CONCLUSIONS

Medulloblastomas present cellular infiltration and a differential expression of TLRs depending on the histological subtype. TLR7 is a prognostic factor of survival that is dependent on treatment and age.

Identification of an Immunogenic Medulloblastoma-Specific Fusion Involving EPC2 and GULP1

Medulloblastoma is the most common malignant brain tumor in children. Immunotherapy is yet to demonstrate dramatic results in medulloblastoma, one reason being the low rate of mutations creating new antigens in this entity. In tumors with low mutational burden, gene fusions may represent a source of tumor-specific neoantigens. Here, we reviewed the landscape of fusions in medulloblastoma and analyzed their predicted immunogenicity. Furthermore, we described a new in-frame fusion protein identified by RNA-Seq. The fusion involved two genes on chromosome 2 coding for the enhancer of polycomb homolog 2 (EPC2) and GULP PTB domain containing engulfment adaptor 1 (GULP1) respectively. By qRT-PCR analysis, the fusion was detected in 3 out of 11 medulloblastoma samples, whereby 2 samples were from the same patients obtained at 2 different time points (initial diagnosis and relapse), but not in other pediatric brain tumor entities. Cloning of the full-length sequence indicated that the fusion protein contains the N-terminal enhancer of polycomb-like domain A (EPcA) of EPC2 and the coiled-coil domain of GULP1. In silico analyses predicted binding of the neoantigen-derived peptide to HLA-A*0201. A total of 50% of the fusions described in the literature were also predicted to produce an immunogenic peptide. The EPC2-GULP1 fusion peptide was able to induce a de novo T cell response characterized by interferon gamma release of CD8⁺ cytotoxic T cells in vitro. While the functional relevance of this fusion in medulloblastoma biology remains to be clarified, our data support an immunotherapeutic approach for pediatric medulloblastoma patients carrying the EPC2-GULP1 fusion and other immunogenic fusions.

Hedgehog Pathway Inhibitors against Tumor Microenvironment

Targeting the hedgehog (HH) pathway to treat aggressive cancers of the brain, breast, pancreas, and prostate has been ongoing for decades. Gli gene amplifications have been long discovered within malignant glioma patients, and since then, inhibitors against HH pathway-associated molecules have successfully reached the clinical stage where several of them have been approved by the FDA. Albeit this success rate implies suitable progress, clinically used HH pathway inhibitors fail to treat patients with metastatic or recurrent disease. This is mainly due to heterogeneous tumor cells that have acquired resistance to the inhibitors along with the obstacle of effectively targeting the tumor microenvironment (TME). Severe side effects such as hyponatremia, diarrhea, fatigue, amenorrhea, nausea, hair loss, abnormal taste, and weight loss have also been reported. Furthermore, HH signaling is known to be involved in the regulation of immune cell maturation, angiogenesis, inflammation, and polarization of macrophages and myeloid-derived suppressor cells. It is critical to determine key mechanisms that can be targeted at different levels of tumor development and progression to address various clinical issues. Hence current research focus encompasses understanding how HH controls TME to develop TME altering and combinatorial targeting strategies. In this review, we aim to discuss the pros and cons of targeting HH signaling molecules, understand the mechanism involved in treatment resistance, reveal the role of the HH pathway in anti-tumor immune response, and explore the development of potential combination treatment of immune checkpoint inhibitors with HH pathway inhibitors to target HH-driven cancers.

The Growing Relevance of Immunoregulation in Pediatric Brain Tumors

Pediatric brain tumors are genetically heterogeneous solid neoplasms. With a prevailing poor prognosis and widespread resistance to conventional multimodal therapy, these aggressive tumors are the leading cause of childhood cancer-related deaths worldwide. Advancement in molecular research revealed their unique genetic and epigenetic characteristics and paved the way for more defined prognostication and targeted therapeutic approaches. Furthermore, uncovering the intratumoral metrics on a single-cell level placed non-malignant cell populations such as innate immune cells into the context of tumor manifestation and progression. Targeting immune cells in pediatric brain tumors entails unique challenges but promising opportunities to improve outcome. Herein, we outline the current understanding of the role of the immune regulation in pediatric brain tumors.

Immunotherapy in Medulloblastoma: Current State of Research, Challenges, and Future Perspectives

Medulloblastoma (MB), a primary tumor of the central nervous system, is among the most prevalent pediatric neoplasms. The median age of diagnosis is six. Conventional therapies include surgical resection of the tumor with subsequent radiation and chemotherapy. However, these therapies often cause severe brain damage, and still, approximately 75% of pediatric patients relapse within a few years. Because the conventional therapies cause such severe damage, especially in the pediatric developing brain, there is an urgent need for better treatment strategies such as immunotherapy, which over the years has gained accumulating interest. Cancer immunotherapy aims to enhance the body's own immune response to tumors and is already widely used in the clinic, e.g., in the treatment of melanoma and lung cancer. However, little is known about the possible application of immunotherapy in brain cancer. In this review, we will provide an overview of the current consensus on MB classification and the state of in vitro, in vivo, and clinical research concerning immunotherapy in MB. Based on existing evidence, we will especially focus on immune checkpoint inhibition and CAR T-cell therapy. Additionally, we will discuss challenges associated with these immunotherapies and relevant strategies to overcome those.

Medulloblastoma in an Adult Female Patient: A Rare Presentation

Medulloblastoma (MB) is an aggressive malignant tumor of the posterior fossa of the CNS that mainly affects children younger than 15 years of age. It is uncommon in the adult population compared to children. Any adult patient presenting with cerebellar mass must be evaluated with brain tissue biopsy to rule out MB. Our patient is a 27-year-old female who presented with sudden onset of frontal headache and was diagnosed with MB.

Immunosuppression in Medulloblastoma: Insights into Cancer Immunity and Immunotherapy

OPINION STATEMENT

Medulloblastoma (MB) is the most common pediatric brain malignancy, with a 5-year overall survival (OS) rate of around 65%. The conventional MB treatment, comprising surgical resection followed by irradiation and adjuvant chemotherapy, often leads to impairment in normal body functions and poor quality of life, especially with the increased risk of recurrence and subsequent development of secondary malignancies. The development and progression of MB are facilitated by a variety of immune-evading mechanisms such as the secretion of immunosuppressive molecules, activation of immunosuppressive cells, inhibition of immune checkpoint molecules, impairment of adhesive molecules, downregulation of the major histocompatibility complex (MHC) molecules, protection against apoptosis, and activation of immunosuppressive pathways. Understanding the tumor-immune relationship in MB is crucial for effective development of immune-based therapeutic strategies. In this comprehensive review, we discuss the immunological aspect of the brain, focusing on the current knowledge tackling the mechanisms of MB immune suppression and evasion. We also highlight several key immunotherapeutic approaches developed to date for the treatment of MB.

DIMEimmune: Robust estimation of infiltrating lymphocytes in CNS tumors from DNA methylation profiles

The interaction of CNS tumors with infiltrating lymphocytes plays an important role in their initiation and progression and might be related to therapeutic responses. Gene expression-based methods have been successfully used to characterize the tumor microenvironment. However, methylation data are now increasingly used for molecular diagnostics and there are currently only few methods to infer information about the microenvironment from this data type. Using an approach based on differential methylation and principal component analysis, we developed DIMEimmune (Differential Methylation Analysis for Immune Cell Estimation) to estimate CD4⁺ and CD8⁺ T cell abundance as well as tumor-infiltrating lymphocytes (TILs) scores from bulk methylation data. Well-established approaches based on gene expression data and immunohistochemistry-based lymphocyte counts were used as benchmarks. The comparison of DIMEimmune to the previously published MethylCIBERSORT and MeTIL algorithms showed an improved correlation with both gene expression-based and immunohistological results across different brain tumor types. Further, we applied our method to large datasets of glioma, medulloblastoma, atypical teratoid/rhabdoid tumors (ATRTs) and ependymoma. High-grade gliomas showed higher scores of tumor-infiltrating lymphocytes than lower-grade gliomas. There were overall only few tumor-infiltrating lymphocytes in medulloblastoma subgroups. ATRTs were highly infiltrated by lymphocytes, most prominently in the MYC subgroup. DIMEimmune-based estimates of TILs were a significant prognostic factor in the overall cohort of gliomas and medulloblastomas, but not within methylation-based diagnostic subgroups. To conclude, DIMEimmune allows for robust estimates of TIL abundance and might contribute to establishing them as a prognostic or predictive factor in future studies of CNS tumors.

Biological Role of MYCN in Medulloblastoma: Novel Therapeutic Opportunities and Challenges Ahead

The constitutive and dysregulated expression of the transcription factor MYCN has a central role in the pathogenesis of the paediatric brain tumour medulloblastoma, with an increased expression of this oncogene correlating with a worse prognosis. Consequently, the genomic and functional alterations of MYCN represent a major therapeutic target to attenuate tumour growth in medulloblastoma. This review will provide a comprehensive synopsis of the biological role of MYCN and its family components, their interaction with distinct signalling pathways, and the implications of this network in medulloblastoma development. We will then summarise the current toolbox for targeting MYCN and highlight novel therapeutic avenues that have the potential to results in better-tailored clinical treatments.

Natural Killer cells and monoclonal antibodies: Two partners for successful antibody dependent cytotoxicity against tumor cells

Monoclonal antibodies targeting tumors are one of the most important discoveries in the field of cancer. Although several effective antibodies have been developed, a relapse may occur. One of their mechanisms of action is Antibody Dependent Cell Cytotoxicity (ADCC), by engaging the Fc γ receptor CD16 expressing Natural Killer cells, innate lymphoid cells involved in cancer immunosurveillance and able to kill tumor cells. A lack of NK cells observed in many cancers may therefore be a cause of the low efficacy of antibodies observed in some clinical situations. Here we review clear evidences of the essential partnership between NK cells and antibodies showed in vitro, in vivo, and in clinical trials in different indications, describe the hurdles and ways to enhance ADCC and the evolution of monoclonal antibody therapy. NK cell adoptive immunotherapy combined with monoclonal antibodies may overcome the resistance to the treatment and enhance their efficacy.

Development of a prognostic model based on an immunogenomic landscape analysis of medulloblastoma

Medulloblastoma (MB) is one of the most common central nervous system tumors in children. At present, the vital role of immune abnormalities has been proved in tumorigenesis and progression. However, the immune mechanism in MB is still poorly understood. In the present study, 51 differentially expressed immune-related genes (DE-IRGs) and 226 survival associated immune-related genes (Sur-IRGs) were screened by an integrated analysis of multi-array. Moreover, the potential pathways were enriched by functional analysis, such as ‘cytokine–cytokine receptor interaction’, ‘Ras signaling pathway’, ‘PI3K-Akt signaling pathway’ and ‘pathways in cancer’. Furthermore, 10 core IRGs were identified from DE-IRGs and Sur-IRGs. And the potential regulatory mechanisms of core IRGs were also explored. Additionally, a new prognostic model, including 7 genes (HDGF, CSK, PNOC, S100A13, RORB, FPR1, and ICAM2) based on IRGs, was established by multivariable COX analysis. In summary, our study revealed the underlying immune mechanism of MB. Moreover, we developed a prognostic model associated with clinical characteristics and could reflect the infiltration of immune cells.

CSF1R inhibition depletes tumor-associated macrophages and attenuates tumor progression in a mouse sonic Hedgehog-Medulloblastoma model

The immune microenvironment of tumors can play a critical role in promoting or inhibiting tumor progression depending on the context. We present evidence that tumor-associated macrophages/microglia (TAMs) can promote tumor progression in the sonic hedgehog subgroup of medulloblastoma (SHH-MB). By combining longitudinal manganese-enhanced magnetic resonance imaging (MEMRI) and immune profiling of a sporadic mouse model of SHH-MB, we found the density of TAMs is higher in the ~50% of tumors that progress to lethal disease. Furthermore, reducing regulatory T cells or eliminating B and T cells in Rag1 mutants does not alter SHH-MB tumor progression. As TAMs are a dominant immune component in tumors and are normally dependent on colony-stimulating factor 1 receptor (CSF1R), we treated mice with a CSF1R inhibitor, PLX5622. Significantly, PLX5622 reduces a subset of TAMs, prolongs mouse survival, and reduces the volume of most tumors within 4 weeks of treatment. Moreover, concomitant with a reduction in TAMs the percentage of infiltrating cytotoxic T cells is increased, indicating a change in the tumor environment. Our studies in an immunocompetent preclinical mouse model demonstrate TAMs can have a functional role in promoting SHH-MB progression. Thus, CSF1R inhibition could have therapeutic potential for a subset of SHH-MB patients.

Deconstructing Sonic Hedgehog Medulloblastoma: Molecular Subtypes, Drivers, and Beyond

Medulloblastoma (MB) is a highly malignant cerebellar tumor predominantly diagnosed during childhood. Driven by pathogenic activation of sonic hedgehog (SHH) signaling, SHH subgroup MB (SHH-MB) accounts for nearly one-third of diagnoses. Extensive molecular analyses have identified biologically and clinically relevant intertumoral heterogeneity among SHH-MB tumors, prompting the recognition of novel subtypes. Beyond germline and somatic mutations promoting constitutive SHH signaling, driver alterations affect a multitude of pathways and molecular processes, including TP53 signaling, chromatin modulation, and post-transcriptional gene regulation. Here, we review recent advances in the underpinnings of SHH-MB in the context of molecular subtypes, clarify novel somatic and germline drivers, highlight cellular origins and developmental hierarchies, and describe the composition of the tumor microenvironment and its putative role in tumorigenesis.

Immune cell infiltration and cytokine secretion analysis reveal a non-inflammatory microenvironment of medulloblastoma

Medulloblastoma (MB) is the most common lethal malignant pediatric brain tumor. Adjuvant immunotherapy for medulloblastoma has been proposed in both pre-clinical and clinical practice. To provide a precision strategy of designing immunotherapy for MB, the present study performed a descriptive analysis of immune microenvironment in a cohort and compared the differences between four subgroups of MB. Subtypes (WNT, SHH Group 3 and Group 4) of medulloblastoma were identified using K-means clustering according to the expression of signature genes. Tumor infiltrating immune cell population was assessed by both bio-informative algorithm based on gene expression and immunohistochemistry staining. Cytokines in tumor microenvironment were detected using Luminex. Gene Set Enrichment Analysis demonstrated a raised immune response in the SHH subgroup. Lymphocyte infiltration was low in all four subgroups, while more CD4+ T cells were observed in the Group 4 subtype. Programmed cell death protein 1 (PD1)/ ligand 1 (PD-L1) expression was absent in the cohort. The SHH subtype recruited more activated tumor associated macrophage/microglia compared with the other subgroups. Cytokines within the MB microenvironment were low compared with the glioblastoma samples. In contrast to glioblastoma, the immune microenvironment of pediatric MB is non-inflammatory and does not recruit many immune cells. These observations provide important considerations for the design of immunotherapeutic approaches for MB, such as inducing more lymphocytes into the tumor microenvironment.

Strategies to Enhance the Efficacy of T-Cell Therapy for Central Nervous System Tumors

Mortality rates in patients diagnosed with central nervous system (CNS) tumors, originating in the brain or spinal cord, continue to remain high despite the advances in multimodal treatment regimens, including surgery, radiation, and chemotherapy. Recent success of adoptive cell transfer immunotherapy treatments using chimeric antigen receptor (CAR) engineered T cells against in chemotherapy resistant CD19 expressing B-cell lymphomas, has provided the foundation for investigating efficacy of CAR T immunotherapies in the context of brain tumor. Although significant efforts have been made in developing and translating the novel CAR T therapies for CNS tumors, including glioblastoma (GBM), researchers are yet to achieve a similar level of success as with liquid malignancies. In this review, we discuss strategies and considerations essential for developing robust preclinical models for the translation of T cell-based therapies for CNS tumors. Some of the key considerations include route of delivery, increasing persistence of T cells in tumor environment, remodeling of myeloid environment, establishing the window of treatment opportunity, harnessing endogenous immune system, designing multiple antigen targeting T cells, and rational combination of immunotherapy with the current standard of care. Although this review focuses primarily on CAR T therapies for GBM, similar strategies, and considerations are applicable to all CNS tumors in general.

Pediatric pan-central nervous system tumor analysis of immune-cell infiltration identifies correlates of antitumor immunity

Immune-therapy is an attractive alternative therapeutic approach for targeting central nervous system (CNS) tumors and the constituency of the Tumor Immune Microenvironment (TIME) likely to predict patient response. Here, we describe the TIME of >6000 primarily pediatric CNS tumors using a deconvolution approach (methylCIBERSORT). We produce and validate a custom reference signature defining 11 non-cancer cell types to estimate relative proportions of infiltration in a panCNS tumor cohort spanning 80 subtypes. We group patients into three broad immune clusters associated with CNS tumor types/subtypes. In cohorts of medulloblastomas (n = 2325), malignant rhabdoid tumors (n = 229) and pediatric high-grade gliomas (n = 401), we show significant associations with molecular subgroups/subtypes, mutations, and prognosis. We further identify tumor-specific immune clusters with phenotypic characteristics relevant to immunotherapy response (i.e. Cytolytic score, PDL1 expression). Our analysis provides an indication of the potential future therapeutic and prognostic possibilities of immuno-methylomic profiling in pediatric CNS tumor patients that may ultimately inform approach to immune-therapy.

Tumor Lipids of Pediatric Papillary Renal Cell Carcinoma Stimulate Unconventional T Cells

Papillary renal cell carcinoma (PRCC) is a rare entity in children with no established therapy protocols for advanced diseases. Immunotherapy is emerging as an important therapeutic tool for childhood cancer. Tumor cells can be recognized and killed by conventional and unconventional T cells. Unconventional T cells are able to recognize lipid antigens presented via CD1 molecules independently from major histocompatibility complex, which offers new alternatives for cancer immunotherapies. The nature of those lipids is largely unknown and α-galactosylceramide is currently used as a synthetic model antigen. In this work, we analyzed infiltrating lymphocytes of two pediatric PRCCs using flow cytometry, immunohistochemistry and qRT-PCR. Moreover, we analyzed the CD1d expression within both tumors. Tumor lipids of PRCC samples and three normal kidney samples were fractionated and the recognition of tumor own lipid fractions by unconventional T cells was analyzed in an in vitro assay. We identified infiltrating lymphocytes including γδ T cells and iNKT cells, as well as CD1d expression in both samples. One lipid fraction, containing ceramides and monoacylglycerides amongst others, was able to induce the proliferation of iNKT cells isolated from peripheral blood mononuclear cells (PBMCs) of healthy donors and of one matched PRCC patient. Furthermore, CD1d tetramer stainings revealed that a subset of iNKT cells is able to bind lipids being present in fraction 2 via CD1d. We conclude that PRCCs are infiltrated by conventional and unconventional T cells and express CD1d. Moreover, certain lipids, present in pediatric PRCC, are able to stimulate unconventional T cells. Manipulating these lipids and T cells may open new strategies for therapy of pediatric PRCCs.

CAR T Cell Therapy for Pediatric Brain Tumors

Chimeric Antigen Receptor (CAR) T cell therapy has recently begun to be used for solid tumors such as glioblastoma multiforme. Many children with pediatric malignant brain tumors develop extensive long-term morbidity of intensive multimodal curative treatment. Others with certain diagnoses and relapsed disease continue to have limited therapies and a dismal prognosis. Novel treatments such as CAR T cells could potentially improve outcomes and ameliorate the toxicity of current treatment. In this review, we discuss the potential of using CAR therapy for pediatric brain tumors. The emerging insights on the molecular subtypes and tumor microenvironment of these tumors provide avenues to devise strategies for CAR T cell therapy. Unique characteristics of these brain tumors, such as location and associated morbid treatment induced neuro-inflammation, are novel challenges not commonly encountered in adult brain tumors. Despite these considerations, CAR T cell therapy has the potential to be integrated into treatment schema for aggressive pediatric malignant brain tumors in the future.